Sample records for study laser cooling
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Laser cooling of molecular anions.
Yzombard, Pauline; Hamamda, Mehdi; Gerber, Sebastian; Doser, Michael; Comparat, Daniel
2015-05-29
We propose a scheme for laser cooling of negatively charged molecules. We briefly summarize the requirements for such laser cooling and we identify a number of potential candidates. A detailed computation study with C_{2}^{-}, the most studied molecular anion, is carried out. Simulations of 3D laser cooling in a gas phase show that this molecule could be cooled down to below 1 mK in only a few tens of milliseconds, using standard lasers. Sisyphus cooling, where no photodetachment process is present, as well as Doppler laser cooling of trapped C_{2}^{-}, are also simulated. This cooling scheme has an impact on the study of cold molecules, molecular anions, charged particle sources, and antimatter physics.
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Study of laser cooling in deep optical lattice: two-level quantum model
NASA Astrophysics Data System (ADS)
Prudnikov, O. N.; Il'enkov, R. Ya.; Taichenachev, A. V.; Yudin, V. I.; Rasel, E. M.
2018-01-01
We study a possibility of laser cooling of 24Mg atoms in deep optical lattice formed by intense off-resonant laser field in a presence of cooling field resonant to narrow (3s3s) 1 S 0 → (3s3p)3 P 1 (λ = 457 nm) optical transition. For description of laser cooling with taking into account quantum recoil effects we consider two quantum models. The first one is based on direct numerical solution of quantum kinetic equation for atom density matrix and the second one is simplified model based on decomposition of atom density matrix over vibration states in the lattice wells. We search cooling field intensity and detuning for minimum cooling energy and fast laser cooling.
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Laser Cooling the Diatomic Molecule CaH
NASA Astrophysics Data System (ADS)
Velasquez, Joe, III; Di Rosa, Michael
2014-06-01
To laser-cool a species, a closed (or nearly closed) cycle is required to dissipate translational energy through many directed laser-photon absorption and subsequent randomly-directed spontaneous emission events. Many atoms lend themselves to such a closed-loop cooling cycle. Attaining laser-cooled molecular species is challenging because of their inherently complex internal structure, yet laser-cooling molecules could lead to studies in interesting chemical dynamics among other applications. Typically, laser-cooled atoms are assembled into molecules through photoassociation or Feschbach resonance. CaH is one of a few molecules whose internal structure is quite atom-like, allowing a nearly closed cycle without the need for many repumping lasers. We will also present our work-to-date on laser cooling this molecule. We employ traditional pulsed atomic/molecular beam techniques with a laser vaporization source to generate species with well-defined translational energies over a narrow range of velocity. In this way, we can apply laser-cooling to most species in the beam along a single dimension (the beam's axis). This project is funded by the LDRD program of the Los Alamos National Laboratory.
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Photodetachment and Doppler laser cooling of anionic molecules
NASA Astrophysics Data System (ADS)
Gerber, Sebastian; Fesel, Julian; Doser, Michael; Comparat, Daniel
2018-02-01
We propose to extend laser-cooling techniques, so far only achieved for neutral molecules, to molecular anions. A detailed computational study is performed for {{{C}}}2- molecules stored in Penning traps using GPU based Monte Carlo simulations. Two cooling schemes—Doppler laser cooling and photodetachment cooling—are investigated. The sympathetic cooling of antiprotons is studied for the Doppler cooling scheme, where it is shown that cooling of antiprotons to subKelvin temperatures could becomes feasible, with impacts on the field of antimatter physics. The presented cooling schemes also have applications for the generation of cold, negatively charged particle sources and for the sympathetic cooling of other molecular anions.
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Yang, Shuo; Du, Dong; Chang, Baohua
2018-02-04
In the laser deposition of single crystal and directionally-solidified superalloys, it is desired to form laser deposits with high volume fractions of columnar grains by suppressing the columnar-to-equiaxed transition efficiently. In this paper, the influence of beam profile (circular and square shapes) and cooling conditions (natural cooling and forced cooling) on the geometric morphology and microstructure of deposits were experimentally studied in the laser deposition of a directionally-solidified superalloy, IC10, and the mechanisms of influence were revealed through a numerical simulation of the thermal processes during laser deposition. The results show that wider and thinner deposits were obtained with the square laser beam than those with the circular laser beam, regardless of whether natural or forced cooling conditions was used. The heights and contact angles of deposits were notably increased due to the reduced substrate temperatures by the application of forced cooling for both laser beam profiles. Under natural cooling conditions, columnar grains formed epitaxially at both the center and the edges of the deposits with the square laser beam, but only at the center of the deposits with the circular laser beam; under forced cooling conditions, columnar grains formed at both the center and the edges of deposits regardless of the laser beam profile. The high ratios of thermal gradient and solidification velocity in the height direction of the deposits were favorable to forming deposits with higher volume fractions of columnar grains.
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Yang, Shuo; Du, Dong
2018-01-01
In the laser deposition of single crystal and directionally-solidified superalloys, it is desired to form laser deposits with high volume fractions of columnar grains by suppressing the columnar-to-equiaxed transition efficiently. In this paper, the influence of beam profile (circular and square shapes) and cooling conditions (natural cooling and forced cooling) on the geometric morphology and microstructure of deposits were experimentally studied in the laser deposition of a directionally-solidified superalloy, IC10, and the mechanisms of influence were revealed through a numerical simulation of the thermal processes during laser deposition. The results show that wider and thinner deposits were obtained with the square laser beam than those with the circular laser beam, regardless of whether natural or forced cooling conditions was used. The heights and contact angles of deposits were notably increased due to the reduced substrate temperatures by the application of forced cooling for both laser beam profiles. Under natural cooling conditions, columnar grains formed epitaxially at both the center and the edges of the deposits with the square laser beam, but only at the center of the deposits with the circular laser beam; under forced cooling conditions, columnar grains formed at both the center and the edges of deposits regardless of the laser beam profile. The high ratios of thermal gradient and solidification velocity in the height direction of the deposits were favorable to forming deposits with higher volume fractions of columnar grains. PMID:29401715
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Laser probes for noninvasive coagulation of subsurface tissues
NASA Astrophysics Data System (ADS)
Chung, Chia-Chun; Permpongkosol, Sompol; Varkarakis, Ioannis M.; Lima, Guilherme; Franco, Nicholas; Hayman, Michael H.; Nicol, Theresa; Fried, Nathaniel M.
2006-02-01
Previous ex vivo tissue studies utilizing deep laser heating combined with contact cooling of the tissue surface produced noninvasive thermal destruction of subsurface tissue structures in skin and liver samples. This study describes the design and preliminary in vivo testing of two integrated laser/cooling probes for simultaneous Nd:YAG laser irradiation and sapphire contact cooling of liver and skin tissues in an in vivo, acute porcine model for potential use in laparoscopic and endoscopic surgery. Nd:YAG laser radiation with a wavelength of 1.06 μm, power of 20 W, 7.5-mm-diameter spot, 500-ms pulse length, and repetition rate of 0.625 Hz, was delivered to the tissue with a total irradiation time of 16 s. The tissue surface was continuously cooled with a sapphire plate maintained at -5 °C, and with pre- and post-ablation cooling times measuring 120 s and 30 s, resulting in a total operation time of 166 s per a lesion. Thermal lesions were created in liver and skin at a 1-mm depth below the tissue surface and with a 3-4 mm diameter. The laser parameters and lesion dimensions were comparable to previous ex vivo tissue studies. Preliminary in vivo animal studies demonstrate noninvasive creation of subsurface thermal lesions in tissue using Nd:YAG laser irradiation in conjunction with sapphire contact cooling. Chronic wound healing studies will be necessary to optimize the laser and cooling parameters. Potential clinical applications include endoscopic laser treatment of female stress urinary incontinence and thermal coagulation of early stage bladder tumors.
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[Water-cooled laser sealing of lung tissue in an ex-vivo ventilated porcine lung model].
Tonoyan, T; Prisadov, G; Menges, P; Herrmann, K; Bobrov, P; Linder, A
2014-06-01
Laser resections of lung metastases are followed by air leaks from the parenchymal defect. Large surfaces after metastasectomy are closed by sutures or sealants while smaller areas are frequently sealed thermally by cautery or laser. In this study two different techniques of thermal sealing of lung tissue with laser light are investigated. Carbonisation of lung tissue during thermal sealing appears at temperatures higher than 180 °C. Hypothetically this is contraproductive to haemo- as well as to pneumostasis. In this experimental study thermal laser sealing with and without carbonisation is investigated. In one series tissue temperatures higher than 100 °C are avoided by water dropping from the tip of the light guide onto the parenchymal leak. In the other series carbonisation appeared because the laser light was applied in the non-contact mode without tissue cooling. The characteristics of the laser were 40 W, 1350 nm continuous mode. Air leaks (Vt) were measured with a simple and fast technique with high precision. The sealing effect of either series was defined as S = (1-Vt/V0) and the difference of S was statistically examined. The basic values V0 before sealing were about the same in both series. The air leaks Vt after 15, 30 and 45 s of sealing varied significantly in both series (p = 0.03). During simultaneous cooling the sealing effect was increasing with the duration of laser application, while it became worse in the series without cooling. Histological examination of the sealing zone showed only coagulation of the tissue, while ruptured alveolae could be seen more often in the non-cooled sealing area. It could be shown in the ex-vivo lung model that laser sealing of parenchymal leaks is improved by simultaneous cooling during laser application. Non cooled laser sealing seems to heat up the tissue abruptly and create carbonisation followed by multiple ruptures of alveola and small airways. In accordance with our clinical experience this experimental study confirms that laser sealing for pneumostasis after metastasectomy can be improved by simultaneously cooling the resection area when treated with the laser. Georg Thieme Verlag KG Stuttgart · New York.
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The suitability of barium monofluoride for laser cooling from ab initio study
NASA Astrophysics Data System (ADS)
Kang, Shuying; Kuang, Fangguang; Jiang, Gang; Du, Jiguang
2016-03-01
The feasibility of laser cooling the 138Ba19F molecule is performed using ab initio quantum chemistry. Three low-lying doublet electronic states X 2Σ+, A' 2Δ and A 2Π are determined by the multireference configuration-interaction (MRCI) method, where the spin-orbit coupling (SOC) effect is also taken into account in the electronic structure calculations. The computed spectroscopic constants and permanent dipole moments agree well with the available experimental data. The Franck-Condon factors of the A 2П → X 2Σ+ transition show highly diagonal dominance (f00 = 0.981, f11 = 0.940, f22 = 0.896) and the A 2П state has a radiative lifetime of τ = 37.8 ns, allowing for rapid laser cooling. Our calculation indicates that the laser-cooling scheme require only three lasers at 822 nm, 855 nm and 856 nm proceeded on the A 2П (ν‧) ← X 2Σ+ (ν‧‧) transitions. The appeared intervening state A' 2Δ between the X 2Σ+ and A 2П states is the main challenge for laser cooling this molecule. In fact, the calculated vibrational branching loss ratio to the intermediate A' 2Δ state is almost negligible at a level of η < 4.5 × 10-9. Thus, BaF is a promising laser-cooling candidate with a relatively simple laser-cooling scheme.
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NASA Astrophysics Data System (ADS)
Chang, Chun-Hung; Wilson, Christopher R.; Fried, Nathaniel M.
2015-07-01
Lasers have been used in combination with applied cooling methods to preserve superficial skin layers (100's μm's) during cosmetic surgery. Preservation of a thicker tissue surface layer (millimeters) may also allow development of other noninvasive laser procedures. We are exploring noninvasive therapeutic laser applications in urology (e.g. laser vasectomy and laser treatment of female stress urinary incontinence), which require surface tissue preservation on the millimeter scale. In this preliminary study, four lasers were compared for noninvasive creation of deep subsurface thermal lesions. Laser energy from three diode lasers (650, 808, and 980 nm) and a Ytterbium fiber laser (1075 nm) was delivered through a custom built, side-firing, laser probe with integrated cooling. An alcohol-based solution at -5 °C was circulated through a flow cell, cooling a sapphire window, which in turn cooled the tissue surface. The probe was placed in contact with porcine liver tissue, ex vivo, kept hydrated in saline and maintained at ~ 35 °C. Incident laser power was 4.2 W, spot diameter was 5.3 mm, and treatment time was 60 s. The optimal laser wavelength tested for creation of deep subsurface thermal lesions during contact cooling of tissues was 1075 nm, which preserved a surface layer of ~ 2 mm. The Ytterbium fiber laser provides a compact, low maintenance, and high power alternative laser source to the Neodymium:YAG laser for noninvasive thermal therapy.
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Wu, Edward C.; Sun, Victor; Manuel, Cyrus T.; Protsenko, Dmitriy E.; Jia, Wangcun; Nelson, J. Stuart; Wong, Brian J. F.
2014-01-01
Laser cartilage reshaping (LCR) with cryogen spray cooling is a promising modality for producing cartilage shape change while reducing cutaneous thermal injury. However, LCR in thicker tissues, such as auricular cartilage, requires higher laser power, thus increasing cooling requirements. To eliminate the risks of freeze injury characteristic of high cryogen spray pulse rates, a carbon dioxide (CO2) spray, which evaporates rapidly from the skin, has been proposed as the cooling medium. This study aims to identify parameter sets which produce clinically significant reshaping while producing minimal skin thermal injury in LCR with CO2 spray cooling in ex vivo rabbit auricular cartilage. Excised whole rabbit ears were mechanically deformed around a cylindrical jig and irradiated with a 1.45-μm wavelength diode laser (fluence 12–14 J/cm2 per pulse, four to six pulse cycles per irradiation site, five to six irradiation sites per row for four rows on each sample) with concomitant application of CO2 spray (pulse duration 33–85 ms) to the skin surface. Bend angle measurements were performed before and after irradiation, and the change quantified. Surface temperature distributions were measured during irradiation/cooling. Maximum skin surface temperature ranged between 49.0 to 97.6 °C following four heating/cooling cycles. Significant reshaping was achieved with all laser dosimetry values with a 50–70 °C difference noted between controls (no cooling) and irradiated ears. Increasing cooling pulse duration yielded progressively improved gross skin protection during irradiation. CO2 spray cooling may potentially serve as an alternative to traditional cryogen spray cooling in LCR and may be the preferred cooling medium for thicker tissues. Future studies evaluating preclinical efficacy in an in vivo rabbit model are in progress. PMID:23307439
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Wu, Edward C; Sun, Victor; Manuel, Cyrus T; Protsenko, Dmitriy E; Jia, Wangcun; Nelson, J Stuart; Wong, Brian J F
2013-11-01
Laser cartilage reshaping (LCR) with cryogen spray cooling is a promising modality for producing cartilage shape change while reducing cutaneous thermal injury. However, LCR in thicker tissues, such as auricular cartilage, requires higher laser power, thus increasing cooling requirements. To eliminate the risks of freeze injury characteristic of high cryogen spray pulse rates, a carbon dioxide (CO2) spray, which evaporates rapidly from the skin, has been proposed as the cooling medium. This study aims to identify parameter sets which produce clinically significant reshaping while producing minimal skin thermal injury in LCR with CO2 spray cooling in ex vivo rabbit auricular cartilage. Excised whole rabbit ears were mechanically deformed around a cylindrical jig and irradiated with a 1.45-μm wavelength diode laser (fluence 12-14 J/cm(2) per pulse, four to six pulse cycles per irradiation site, five to six irradiation sites per row for four rows on each sample) with concomitant application of CO2 spray (pulse duration 33-85 ms) to the skin surface. Bend angle measurements were performed before and after irradiation, and the change quantified. Surface temperature distributions were measured during irradiation/cooling. Maximum skin surface temperature ranged between 49.0 to 97.6 °C following four heating/cooling cycles. Significant reshaping was achieved with all laser dosimetry values with a 50-70 °C difference noted between controls (no cooling) and irradiated ears. Increasing cooling pulse duration yielded progressively improved gross skin protection during irradiation. CO2 spray cooling may potentially serve as an alternative to traditional cryogen spray cooling in LCR and may be the preferred cooling medium for thicker tissues. Future studies evaluating preclinical efficacy in an in vivo rabbit model are in progress.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Rozhdestvensky, Yu V
The possibility is studied for obtaining intense cold atomic beams by using the Renyi entropy to optimise the laser cooling process. It is shown in the case of a Gaussian velocity distribution of atoms, the Renyi entropy coincides with the density of particles in the phase space. The optimisation procedure for cooling atoms by resonance optical radiation is described, which is based on the thermodynamic law of increasing the Renyi entropy in time. Our method is compared with the known methods for increasing the laser cooling efficiency such as the tuning of a laser frequency in time and a changemore » of the atomic transition frequency in an inhomogeneous transverse field of a magnetic solenoid. (laser cooling)« less
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NASA Astrophysics Data System (ADS)
Seryi, Andrei; Lesz, Zsolt; Andreev, Alexander; Konoplev, Ivan
2017-03-01
A novel method for generating GigaGauss solenoidal fields in a laser-plasma bubble, using screw-shaped laser pulses, has been recently presented. Such magnetic fields enable fast synchrotron radiation cooling of the beam emittance of laser-plasma accelerated leptons. This recent finding opens a novel approach for design of laser-plasma FELs or colliders, where the acceleration stages are interleaved with laser-plasma emittance cooling stages. In this concept paper, we present an outline of what a staged plasma-acceleration FEL could look like, and discuss further studies needed to investigate the feasibility of the concept in detail.
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Ultracold Anions for High-Precision Antihydrogen Experiments
NASA Astrophysics Data System (ADS)
Cerchiari, G.; Kellerbauer, A.; Safronova, M. S.; Safronova, U. I.; Yzombard, P.
2018-03-01
Experiments with antihydrogen (H ¯) for a study of matter-antimatter symmetry and antimatter gravity require ultracold H ¯ to reach ultimate precision. A promising path towards antiatoms much colder than a few kelvin involves the precooling of antiprotons by laser-cooled anions. Because of the weak binding of the valence electron in anions—dominated by polarization and correlation effects—only few candidate systems with suitable transitions exist. We report on a combination of experimental and theoretical studies to fully determine the relevant binding energies, transition rates, and branching ratios of the most promising candidate La- . Using combined transverse and collinear laser spectroscopy, we determined the resonant frequency of the laser cooling transition to be ν =96.592 713 (91 ) THz and its transition rate to be A =4.90 (50 )×104 s-1 . Using a novel high-precision theoretical treatment of La- we calculated yet unmeasured energy levels, transition rates, branching ratios, and lifetimes to complement experimental information on the laser cooling cycle of La- . The new data establish the suitability of La- for laser cooling and show that the cooling transition is significantly stronger than suggested by a previous theoretical study.
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Ultracold Anions for High-Precision Antihydrogen Experiments.
Cerchiari, G; Kellerbauer, A; Safronova, M S; Safronova, U I; Yzombard, P
2018-03-30
Experiments with antihydrogen (H[over ¯]) for a study of matter-antimatter symmetry and antimatter gravity require ultracold H[over ¯] to reach ultimate precision. A promising path towards antiatoms much colder than a few kelvin involves the precooling of antiprotons by laser-cooled anions. Because of the weak binding of the valence electron in anions-dominated by polarization and correlation effects-only few candidate systems with suitable transitions exist. We report on a combination of experimental and theoretical studies to fully determine the relevant binding energies, transition rates, and branching ratios of the most promising candidate La^{-}. Using combined transverse and collinear laser spectroscopy, we determined the resonant frequency of the laser cooling transition to be ν=96.592 713(91) THz and its transition rate to be A=4.90(50)×10^{4} s^{-1}. Using a novel high-precision theoretical treatment of La^{-} we calculated yet unmeasured energy levels, transition rates, branching ratios, and lifetimes to complement experimental information on the laser cooling cycle of La^{-}. The new data establish the suitability of La^{-} for laser cooling and show that the cooling transition is significantly stronger than suggested by a previous theoretical study.
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Molecular Dynamics Simulation of the Three-Dimensional Ordered State in Laser-Cooled Heavy-Ion Beams
NASA Astrophysics Data System (ADS)
Yuri, Yosuke
A molecular dynamics simulation is performed to study the formation of three-dimensional ordered beams by laser cooling in a cooler storage ring. Ultralow-temperature heavy-ion beams are generated by transverse cooling with displaced Gaussian lasers and resonant coupling. A three-dimensional ordered state of the ion beam is attained at a high line density. The ordered beam exhibits several unique characteristics different from those of an ideal crystalline beam.
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Cooling rates and intensity limitations for laser-cooled ions at relativistic energies
NASA Astrophysics Data System (ADS)
Eidam, Lewin; Boine-Frankenheim, Oliver; Winters, Danyal
2018-04-01
The ability of laser cooling for relativistic ion beams is investigated. For this purpose, the excitation of relativistic ions with a continuous wave and a pulsed laser is analyzed, utilizing the optical Bloch equations. The laser cooling force is derived in detail and its scaling with the relativistic factor γ is discussed. The cooling processes with a continuous wave and a pulsed laser system are investigated. Optimized cooling scenarios and times are obtained in order to determine the required properties of the laser and the ion beam for the planed experiments. The impact of beam intensity effects, like intrabeam scattering and space charge are analyzed. Predictions from simplified models are compared to particle-in-cell simulations and are found to be in good agreement. Finally two realistic example cases of Carbon ions in the ESR and relativistic Titanium ions in SIS100 are compared in order to discuss prospects for future laser cooling experiments.
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Flowing Air-Water Cooled Slab Nd: Glass Laser
NASA Astrophysics Data System (ADS)
Lu, Baida; Cai, Bangwei; Liao, Y.; Xu, Shifa; Xin, Z.
1989-03-01
A zig-zag optical path slab geometry Nd: glass laser cooled through flowing air-water is developed by us. Theoretical studies on temperature distribution of slab and rod configurations in the unsteady state clarify the advantages of the slab geometry laser. The slab design and processing are also reported. In our experiments main laser output characteristics, e. g. laser efficiency, polarization, far-field divergence angle as well as resonator misalignment are investigated. The slab phosphate glass laser in combination with a crossed Porro-prism resonator demonstrates a good laser performance.
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NASA Astrophysics Data System (ADS)
Bo, Yan; Bu, Wenhao; Chen, Tao; Lv, Guitao
2017-04-01
In this poster, we report our recently experimental progresses in laser cooling of BaF molecule. Our theoretic calculation shows BaF is a good candidate for laser cooling: quasi-cycling transitions, good wavelengths (around 900nm) for the main transitions. We have built a 4K cryogenic machine, laser ablate the target to make BaF molecules. The precise spectroscopy of BaF is measured and the laser cooling related transitions are identified. The collision between BaF and 4K He is carefully characterized. The quasi-cycling transition is demonstrated. And laser cooling experiment is going on.
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Foil cooling for rep-rated electron beam pumped KrF lasers
NASA Astrophysics Data System (ADS)
Giuliani, J. L.; Hegeler, F.; Sethian, J. D.; Wolford, M. F.; Myers, M. C.; Abdel-Khalik, S.; Sadowski, D.; Schoonover, K.; Novak, V.
2006-06-01
In rep-rated electron beam pumped lasers the foil separating the vacuum diode from the laser gas is subject to repeated heating due to partial beam stopping. Three cooling methods are examined for the Electra KrF laser at the Naval Research Laboratory (NRL). Foil temperature measurements for convective cooling by the recirculating laser gas and by spray mist cooling are reported, along with estimates for thermal conductive foil cooling to the hibachi ribs. Issues on the application of each of these approaches to laser drivers in a fusion power plant are noted. Work supported by DOE/NNSA.
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Cryogen spray cooling during laser tissue welding.
Fried, N M; Walsh, J T
2000-03-01
Cryogen cooling during laser tissue welding was explored as a means of reducing lateral thermal damage near the tissue surface and shortening operative time. Two centimetre long full-thickness incisions were made on the epilated backs of guinea pigs, in vivo. India ink was applied to the incision edges then clamps were used to appose the edges. A 4 mm diameter beam of 16 W, continuous-wave, 1.06 microm, Nd:YAG laser radiation was scanned over the incisions, producing approximately 100 ms pulses. There was a delay of 2 s between scans. The total irradiation time was varied from 1-2 min. Cryogen was delivered to the weld site through a solenoid valve in spurt durations of 20, 60 and 100 ms. The time between spurts was either 2 or 4 s, corresponding to one spurt every one or two laser scans. Histology and tensile strength measurements were used to evaluate laser welds. Total irradiation times were reduced from 10 min without surface cooling to under 1 min with surface cooling. The thermal denaturation profile showed less denaturation in the papillary dermis than in the mid-dermis. Welds created using optimized irradiation and cooling parameters had significantly higher tensile strengths (1.7 +/- 0.4 kg cm(-2)) than measured in the control studies without cryogen cooling (1.0 +/- 0.2 kg cm(-2)) (p < 0.05). Cryogen cooling of the tissue surface during laser welding results in increased weld strengths while reducing thermal damage and operative times. Long-term studies will be necessary to determine weld strengths and the amount of scarring during wound healing.
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LASER BIOLOGY AND MEDICINE: Optoacoustic laser monitoring of cooling and freezing of tissues
NASA Astrophysics Data System (ADS)
Larin, Kirill V.; Larina, I. V.; Motamedi, M.; Esenaliev, R. O.
2002-11-01
Real-time monitoring of cooling and freezing of tissues, cells, and other biological objects with a high spatial and time resolution, which is necessary for selective destruction of cancer and benign tumours during cryotherapy, as well as for preventing any damage to the structure and functioning of biological objects in cryobiology, is considered. The optoacoustic method, based on the measurement and analysis of acoustic waves induced by short laser pulses, is proposed for monitoring the cooling and freezing of the tissue. The effect of cooling and freezing on the amplitude and time profile of acoustic signals generated in real tissues and in a model object is studied. The experimental results indicate that the optoacoustic laser technique can be used for real-time monitoring of cooling and freezing of biological objects with a submillimeter spatial resolution and a high contrast.
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NASA Astrophysics Data System (ADS)
Wang, Jingwei; Zhu, Pengfei; Liu, Hui; Liang, Xuejie; Wu, Dihai; Liu, Yalong; Yu, Dongshan; Zah, Chung-en; Liu, Xingsheng
2017-02-01
High power diode lasers have been widely used in many fields. To meet the requirements of high power and high reliability, passively cooled single bar CS-packaged diode lasers must be robust to withstand thermal fatigue and operate long lifetime. In this work, a novel complete indium-free double-side cooling technology has been applied to package passively cooled high power diode lasers. Thermal behavior of hard solder CS-package diode lasers with different packaging structures was simulated and analyzed. Based on these results, the device structure and packaging process of double-side cooled CS-packaged diode lasers were optimized. A series of CW 200W 940nm high power diode lasers were developed and fabricated using hard solder bonding technology. The performance of the CW 200W 940nm high power diode lasers, such as output power, spectrum, thermal resistance, near field, far field, smile, lifetime, etc., is characterized and analyzed.
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Simulations Of Laser Cooling In An Ultracold Neutral Plasma
NASA Astrophysics Data System (ADS)
Langin, Thomas; Strickler, Trevor; Pohl, Thomas; Vrinceanu, Daniel; Killian, Thomas
2016-05-01
Ultracold neutral plasmas (UNPs) generated by photoionization of laser-cooled, magneto-optically trapped neutral gases, are useful systems for studying strongly coupled plasmas. Coupling is parameterized by Γi, the ratio of the average nearest neighbor Coulomb interaction energy to the ion kinetic energy. For typical UNPs, Γi is currently limited to ~ 3 . For alkaline earth ions, higher Γi can be achieved by laser-cooling. Using Molecular Dynamics and a quantum trajectories approach, we have simulated laser-cooling of Sr+ ions interacting through a Yukawa potential. The simulations include re-pumping from two long-lived D-states, and are conducted at experimentally achievable parameters (density n = 2 e+14 m-3, size σ0 = 4 mm, Te = 19 K). Laser-cooling is shown to both reduce the temperature by a factor of 2 over relevant timescales (tens of μ s) and slow the electron thermal-pressure driven radial expansion of the UNP. We also discuss the unique aspects of laser-cooling in a highly collisional system; in particular, the effect of collisions on dark state formation due to the coupling of the P3/2 state to both the S1/2 (via the cooling transition) and the D5/2 (via a re-pump transition) states. Supported by NSF and DoE, the Air Force Office of Scientific Research, the NDSEG Program, and NIH NCRR S10RR02950, an IBM SUR Award in partnership with CISCO, Qlogic and Adaptive Computing.
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Clock Technology Development for the Laser Cooling and Atomic Physics (LCAP) Program
NASA Technical Reports Server (NTRS)
Klipstein, W. M.; Thompson, R. J.; Seidel, D. J.; Kohel, J.; Maleki, L.
1998-01-01
The Time and Frequency Sciences and Technology Group at Jet Propulsion Laboratory (JPL) has developed a laser cooling capability for flight and has been selected by NASA to support the Laser-Cooling and Atomic Physics (LCAP) program. Current work in the group includes design and development for tee two laser-cooled atomic clock experiments which have been selected for flight on the International Space Station.
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Photothermal heating and cooling of nanostructures.
Crane, Matthew Joseph; Zhou, Xuezhe; Davis, E James; Pauzauskie, Peter
2018-06-11
A vast range of insulating, semiconducting, and metallic nanomaterials have been studied over the past several decades with the aim of understanding how continuous-wave or pulsed laser radiation can influence their chemical functionality and local environment. Many fascinating observations have been made during laser irradiation including, but not limited to, the superheating of solvents, mass-transport-mediated morphology evolution, photodynamic therapy, morphology dependent resonances, and a range of phase transformations. In addition to laser heating, recent experiments have demonstrated the laser cooling of nanoscale materials through the emission of upconverted, anti-Stokes photons by trivalent rare-earth ions. This focus review outlines the analytical modeling of photothermal heat transport with an emphasis on the experimental validation of anti-Stokes laser cooling. This general methodology can be applied to a wide range of photothermal applications, including nanomedicine, photocatalysis, and the synthesis of new materials. The review concludes with an overview of recent advances and future directions for anti-Stokes cooling. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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Ion-Atom Cold Collisions and Atomic Clocks
NASA Technical Reports Server (NTRS)
Prestage, John D.; Maleki, Lute; Tjoelker, Robert L.
1997-01-01
Collisions between ultracold neutral atoms have for some time been the subject of investigation, initially with hydrogen and more recently with laser cooled alkali atoms. Advances in laser cooling and trapping of neutral atoms in a Magneto-Optic Trap (MOT) have made cold atoms available as the starting point for many laser cooled atomic physics investigations. The most spectacularly successful of these, the observation of Bose-Einstein Condensation (BEC) in a dilute ultra-cold spin polarized atomic vapor, has accelerated the study of cold collisions. Experimental and theoretical studies of BEC and the long range interaction between cold alkali atoms is at the boundary of atomic and low temperature physics. Such studies have been difficult and would not have been possible without the development and advancement of laser cooling and trapping of neutral atoms. By contrast, ion-atom interactions at low temperature, also very difficult to study prior to modern day laser cooling, have remained largely unexplored. But now, many laboratories worldwide have almost routine access to cold neutral atoms. The combined technologies of ion trapping, together with laser cooling of neutrals has made these studies experimentally feasible and several very important, novel applications might come out of such investigations . This paper is an investigation of ion-atom interactions in the cold and ultra-cold temperature regime. Some of the collisional ion-atom interactions present at room temperature are very much reduced in the low temperature regime. Reaction rates for charge transfer between unlike atoms, A + B(+) approaches A(+) + B, are expected to fall rapidly with temperature, approximately as T(sup 5/2). Thus, cold mixtures of atoms and ions are expected to coexist for very long times, unlike room temperature mixtures of the same ion-atom combination. Thus, it seems feasible to cool ions via collisions with laser cooled atoms. Many of the conventional collisional interactions, exploited as a useful tool at room temperature and higher, are greatly enhanced at low energy. For example, collisional spin transfer from one species of polarized atoms to another has long been a useful method for polarizing a sample of atoms where no other means was available. Because optical pumping cannot be used to polarize the nuclear spin of Xe-129 or He-3 (for use in nmr imaging of the lungs), the nuclear spins are polarized via collisions with an optically pumped Rb vapor in a cell containing both gases. In another case, a spin polarized thermal Cs beam was used to polarize the hyperfine states of trapped He(+)-3 ions in order to measure their hyperfine clock transition frequency. The absence of an x-ray light source to optically pump the ground state of the He(+)-3 ion necessitated this alternative state preparation. Similarly, Cd(+) and Sr(+) ions were spin-oriented via collisions in a cell with optically pumped Rb vapor. Resonant RF spin changing transitions in the ground state of the ions were detected by changes in the Rb resonance light absorption. Because cold collision spin exchange rates scale with temperature as T(sup -1/2) this technique is expected to be a far more powerful tool than the room temperature counterpart. This factor of 100 or more enhancement in spin exchange reaction rates at low temperatures is the basis for a novel trapped ion clock where laser cooled neutrals will cool, state select and monitor the ion clock transition. The advantage over conventional direct laser cooling of trapped ions is that the very expensive and cumbersome UV laser light sources, required to excite the ionic cooling transition, are effectively replaced by simple diode lasers.
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Kuan, Edward C.; Hamamoto, Ashley A.; Sun, Victor; Nguyen, Tony; Manuel, Cyrus T.; Protsenko, Dmitry E.; Wong, Brian J.F.; Nelson, J. Stuart; Jia, Wangcun
2014-01-01
BACKGROUND/OBJECTIVES Similar to conventional cryogen spray cooling, carbon dioxide (CO2) spray may be used in combination with laser cartilage reshaping (LCR) to produce cartilage shape change while minimizing cutaneous thermal injury. Recent ex vivo evaluation of LCR with CO2 cooling in a rabbit model has identified a promising initial parameter space for in vivo safety and efficacy evaluation. This pilot study aimed to evaluate shape change and cutaneous injury following LCR with CO2 cooling in 5 live rabbits. STUDY DESIGN/MATERIALS AND METHODS The midportion of live rabbit ears were irradiated with a 1.45 μm wavelength diode laser (12 J/cm2) with simultaneous CO2 spray cooling (85 ms duration, 4 alternating heating/cooling cycles per site, 5 to 6 irradiation sites per row for 3 rows per ear). Experimental and control ears (no LCR) were splinted in the flexed position for 30 days following exposure. A total of 5 ears each were allocated to the experimental and control groups. RESULTS Shape change was observed in all irradiated ears (mean 70 ± 3°), which was statistically different from control (mean 37 ± 11 °, p = 0.009). No significant thermal cutaneous injury was observed, with preservation of the full thickness of skin, microvasculature, and adnexal structures. Confocal microscopy and histology demonstrated an intact and viable chondrocyte population surrounding irradiated sites. CONCLUSIONS LCR with CO2 spray cooling can produce clinically significant shape change in the rabbit auricle while minimizing thermal cutaneous and cartilaginous injury and frostbite. This pilot study lends support for the potential use of CO2 spray as an adjunct to existing thermal-based cartilage reshaping modalities. An in vivo systematic evaluation of optimal laser dosimetry and cooling parameters is required. PMID:25557008
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High density, optically corrected, micro-channel cooled, v-groove monolithic laser diode array
Freitas, Barry L.
1998-01-01
An optically corrected, micro-channel cooled, high density laser diode array achieves stacking pitches to 33 bars/cm by mounting laser diodes into V-shaped grooves. This design will deliver>4kW/cm2 of directional pulsed laser power. This optically corrected, micro-channel cooled, high density laser is usable in all solid state laser systems which require efficient, directional, narrow bandwidth, high optical power density pump sources.
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Optimum design on refrigeration system of high-repetition-frequency laser
NASA Astrophysics Data System (ADS)
Li, Gang; Li, Li; Jin, Yezhou; Sun, Xinhua; Mao, Shaojuan; Wang, Yuanbo
2014-12-01
A refrigeration system with fluid cycle, semiconductor cooler and air cooler is designed to solve the problems of thermal lensing effect and unstable output of high-repetition-frequency solid-state lasers. Utilizing a circulating water pump, water recycling system carries the water into laser cavity to absorb the heat then get to water cooling head. The water cooling head compacts cold spot of semiconductor cooling chips, so the heat is carried to hot spot which contacts the radiating fins, then is expelled through cooling fan. Finally, the cooled water return to tank. The above processes circulate to achieve the purposes of highly effective refrigeration in miniative solid-state lasers.The refrigeration and temperature control components are designed strictly to ensure refrigeration effect and practicability. we also set up a experiment to test the performances of this refrigeration system, the results show that the relationship between water temperature and cooling power of semiconductor cooling chip is linear at 20°C-30°C (operating temperature range of Nd:YAG), the higher of the water temperature, the higher of cooling power. According to the results, cooling power of single semiconductor cooling chip is above 60W, and the total cooling power of three semiconductor cooling chips achieves 200W that will satisfy the refrigeration require of the miniative solid-state lasers.The performance parameters of laser pulse are also tested, include pulse waveform, spectrogram and laser spot. All of that indicate that this refrigeration system can ensure the output of high-repetition-frequency pulse whit high power and stability.
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Space qualified Nd:YAG laser (phase 1 - design)
NASA Technical Reports Server (NTRS)
Foster, J. D.; Kirk, R. F.
1971-01-01
Results of a design study and preliminary design of a space qualified Nd:YAG laser are presented. A theoretical model of the laser was developed to allow the evaluation of the effects of various parameters on its performance. Various pump lamps were evaluated and sum pumping was considered. Cooling requirements were examined and cooling methods such as radiation, cryogenic and conductive were analysed. Power outputs and efficiences of various configurations and the pump and laser lifetime are discussed. Also considered were modulation and modulating methods.
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Laser and Optical Subsystem for NASA's Cold Atom Laboratory
NASA Astrophysics Data System (ADS)
Kohel, James; Kellogg, James; Elliott, Ethan; Krutzik, Markus; Aveline, David; Thompson, Robert
2016-05-01
We describe the design and validation of the laser and optics subsystem for NASA's Cold Atom Laboratory (CAL), a multi-user facility being developed at NASA's Jet Propulsion Laboratory for studies of ultra-cold quantum gases in the microgravity environment of the International Space Station. Ultra-cold atoms will be generated in CAL by employing a combination of laser cooling techniques and evaporative cooling in a microchip-based magnetic trap. Laser cooling and absorption imaging detection of bosonic mixtures of 87 Rb and 39 K or 41 K will be accomplished using a high-power (up to 500 mW ex-fiber), frequency-agile dual wavelength (767 nm and 780 nm) laser and optical subsystem. The CAL laser and optical subsystem also includes the capability to generate high-power multi-frequency optical pulses at 784.87 nm to realize a dual-species Bragg atom interferometer. Currently at Humboldt-Universität zu Berlin.
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High density, optically corrected, micro-channel cooled, v-groove monolithic laser diode array
Freitas, B.L.
1998-10-27
An optically corrected, micro-channel cooled, high density laser diode array achieves stacking pitches to 33 bars/cm by mounting laser diodes into V-shaped grooves. This design will deliver > 4kW/cm{sup 2} of directional pulsed laser power. This optically corrected, micro-channel cooled, high density laser is usable in all solid state laser systems which require efficient, directional, narrow bandwidth, high optical power density pump sources. 13 figs.
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Politi, Y; Levi, A; Enk, C D; Lapidoth, M
2015-12-01
Acne treatment by a mid-infrared laser may be unsatisfactory due to deeply situated acne-affected sebaceous glands which serve as its target. Skin manipulation by vacuum and contact cooling may improve laser-skin interaction, reduce pain sensation, and increase overall safety and efficacy. To evaluate the safety and efficacy of acne treatment using an integrated cooling-vacuum-assisted 1540-nm erbium:glass laser, a prospective interventional study was conducted. It included 12 patients (seven men and five women) suffering from mild-to-moderate acne vulgaris. The device utilizes a mid-infrared 1540-nm laser (Alma Lasers Ltd. Caesarea, Israel), which is integrated with combined cooling-vacuum-assisted technology. An acne lesion is initially manipulated upon contact by a vacuum-cooling-assisted tip, followed by three to four stacked laser pulses (500-600 mJ, 4 mm spot size, and frequency of 2 Hz). Patients underwent four to six treatment sessions with a 2-week interval and were followed-up 1 and 3 months after the last treatment. Clinical photographs were taken by high-resolution digital camera before and after treatment. Clinical evaluation was performed by two independent dermatologists, and results were graded on a scale of 0 (exacerbation) to 4 (76-100 % improvement). Patients' and physicians' satisfaction was also recorded. Pain perception and adverse effects were evaluated as well. All patients demonstrated a moderate to significant improvement (average score of 3.6 and 2.0 within 1 and 3 months, respectively, following last treatment session). No side effects, besides a transient erythema, were observed. Cooling-vacuum-assisted 1540-nm laser is safe and effective for the treatment of acne vulgaris.
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Regulation and Measurement of the Heat Generated by Automatic Tooth Preparation in a Confined Space.
Yuan, Fusong; Zheng, Jianqiao; Sun, Yuchun; Wang, Yong; Lyu, Peijun
2017-06-01
The aim of this study was to assess and regulate heat generation in the dental pulp cavity and circumambient temperature around a tooth during laser ablation with a femtosecond laser in a confined space. The automatic tooth preparing technique is one of the traditional oral clinical technology innovations. In this technique, a robot controlled an ultrashort pulse laser to automatically complete the three-dimensional teeth preparing in a confined space. The temperature control is the main measure for protecting the tooth nerve. Ten tooth specimens were irradiated with a femtosecond laser controlled by a robot in a confined space to generate 10 teeth preparation. During the process, four thermocouple sensors were used to record the pulp cavity and circumambient environment temperatures with or without air cooling. A statistical analysis of the temperatures was performed between the conditions with and without air cooling (p < 0.05). The recordings showed that the temperature with air cooling was lower than that without air cooling and that the heat generated in the pulp cavity was lower than the threshold for dental pulp damage. These results indicate that femtosecond laser ablation with air cooling might be an appropriate method for automatic tooth preparing.
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Magneto-optical cooling of atoms.
Raizen, Mark G; Budker, Dmitry; Rochester, Simon M; Narevicius, Julia; Narevicius, Edvardas
2014-08-01
We propose an alternative method to laser cooling. Our approach utilizes the extreme brightness of a supersonic atomic beam, and the adiabatic atomic coilgun to slow atoms in the beam or to bring them to rest. We show how internal-state optical pumping and stimulated optical transitions, combined with magnetic forces, can be used to cool the translational motion of atoms. This approach does not rely on momentum transfer from photons to atoms, as in laser cooling. We predict that our method can surpass laser cooling in terms of flux of ultracold atoms and phase-space density, with lower required laser power.
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New Experimental Approaches and Theoretical Modeling Methods for Laser Cooling Atoms and Molecules
2006-07-27
support of experimental efforts in various laboratories to produce ultracold molecules by laser -induced photoassociation of laser -cooled atoms. We are......temperatures so far have been 25mK [7], rather than tens of µK as one can achieve with laser cooling of atoms. Thus an approach that begins with cold
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Evaluation of thermal cooling mechanisms for laser application to teeth.
Miserendino, L J; Abt, E; Wigdor, H; Miserendino, C A
1993-01-01
Experimental cooling methods for the prevention of thermal damage to dental pulp during laser application to teeth were compared to conventional treatment in vitro. Pulp temperature measurements were made via electrical thermistors implanted within the pulp chambers of extracted human third molar teeth. Experimental treatments consisted of lasing without cooling, lasing with cooling, laser pulsing, and high-speed dental rotary drilling. Comparisons of pulp temperature elevation measurements for each group demonstrated that cooling by an air and water spray during lasing significantly reduced heat transfer to dental pulp. Laser exposures followed by an air and water spray resulted in pulp temperature changes comparable to conventional treatment by drilling. Cooling by an air water spray with evacuation appears to be an effective method for the prevention of thermal damage to vital teeth following laser exposure.
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First demonstration of an all-solid-state optical cryocooler
Hehlen, Markus P.; Meng, Junwei; Albrecht, Alexander R.; ...
2018-06-06
Solid-state optical refrigeration uses anti-Stokes fluorescence to cool macroscopic objects to cryogenic temperatures without vibrations. Crystals such as Yb 3+-doped YLiF 4 (YLF:Yb) have previously been laser-cooled to 91 K. In this study, we show for the first time laser cooling of a payload connected to a cooling crystal. A YLF:Yb crystal was placed inside a Herriott cell and pumped with a 1020-nm laser (47 W) to cool a HgCdTe sensor that is part of a working Fourier Transform Infrared (FTIR) spectrometer to 135 K. This first demonstration of an all-solid-state optical cryocooler was enabled by careful control of themore » various desired and undesired heat flows. Fluorescence heating of the payload was minimized by using a single-kink YLF thermal link between the YLF:Yb cooling crystal and the copper coldfinger that held the HgCdTe sensor. The adhesive-free bond between YLF and YLF:Yb showed excellent thermal reliability. This laser-cooled assembly was then supported by silica aerogel cylinders inside a vacuum clamshell to minimize undesired conductive and radiative heat loads from the warm surroundings. Our structure can serve as a baseline for future optical cryocooler devices.« less
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First demonstration of an all-solid-state optical cryocooler
DOE Office of Scientific and Technical Information (OSTI.GOV)
Hehlen, Markus P.; Meng, Junwei; Albrecht, Alexander R.
Solid-state optical refrigeration uses anti-Stokes fluorescence to cool macroscopic objects to cryogenic temperatures without vibrations. Crystals such as Yb 3+-doped YLiF 4 (YLF:Yb) have previously been laser-cooled to 91 K. In this study, we show for the first time laser cooling of a payload connected to a cooling crystal. A YLF:Yb crystal was placed inside a Herriott cell and pumped with a 1020-nm laser (47 W) to cool a HgCdTe sensor that is part of a working Fourier Transform Infrared (FTIR) spectrometer to 135 K. This first demonstration of an all-solid-state optical cryocooler was enabled by careful control of themore » various desired and undesired heat flows. Fluorescence heating of the payload was minimized by using a single-kink YLF thermal link between the YLF:Yb cooling crystal and the copper coldfinger that held the HgCdTe sensor. The adhesive-free bond between YLF and YLF:Yb showed excellent thermal reliability. This laser-cooled assembly was then supported by silica aerogel cylinders inside a vacuum clamshell to minimize undesired conductive and radiative heat loads from the warm surroundings. Our structure can serve as a baseline for future optical cryocooler devices.« less
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Laser cooling by adiabatic transfer
NASA Astrophysics Data System (ADS)
Norcia, Matthew; Cline, Julia; Bartolotta, John; Holland, Murray; Thompson, James
2017-04-01
We have demonstrated a new method of laser cooling applicable to particles with narrow linewidth optical transitions. This simple and robust cooling mechanism uses a frequency-swept laser to adiabatically transfer atoms between internal and motional states. The role of spontaneous emission is reduced (though is still critical) compared to Doppler cooling. This allows us to achieve greater slowing forces than would be possible with Doppler cooling, and may make this an appealing technique for cooling molecules. In this talk, I will present a demonstration of this technique in a cold strontium system. DARPA QUASAR, NIST, NSF PFC.
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Rapid crystallization of externally produced ions in a Penning trap
NASA Astrophysics Data System (ADS)
Murböck, T.; Schmidt, S.; Birkl, G.; Nörtershäuser, W.; Thompson, R. C.; Vogel, M.
2016-10-01
We have studied the cooling dynamics, formation process, and geometric structure of mesoscopic crystals of externally produced magnesium ions in a Penning trap. We present a cooling model and measurements for a combination of buffer gas cooling and laser cooling which has been found to reduce the ion kinetic energy by eight orders of magnitude from several hundreds of eV to μ eV and below within seconds. With ion numbers of the order of 1 ×103 to 1 ×105 , such cooling leads to the formation of ion Coulomb crystals which display a characteristic shell structure in agreement with the theory of non-neutral plasmas. We show the production and characterization of two-species ion crystals as a means of sympathetic cooling of ions lacking a suitable laser-cooling transition.
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NASA Astrophysics Data System (ADS)
Mordon, Serge R.; Capon, Alexandre; Creusy, Collette; Fleurisse, Laurence; Buys, Bruno; Faucheux, Marc A.; Servell, Pascal
2000-05-01
Selective dermal remodeling using diode or 1.32 micrometer Nd:YAG lasers has been recently proposed for skin rejuvenation. This new technique consists in inducing collagen tightening and/or neocollagen synthesis without significant damage of the overlying epidermis. Such an approach requires (1) a cooling system in order to target dermal collagen with relatively good protection of the epidermal layer, (2) a specific wavelength for confining the thermal damage into the upper dermis (100 to 400 micrometer). Based on previous studies, demonstrating a better water absorption and a reduced melanin absorption at 1.54 micrometer compared to the 1.32 micrometer, this experimental study aimed to evaluate a new laser (co-doped Yb-Er:phosphate glass material, Aramis, Quantel-France) emitting at 1.54 micrometer. This laser was used in combination with the Dermacool system (Dermacool, Mableton, USA) in order to achieve epidermis cooling before, during and after irradiation. Male hairless rats were used for the study. Pulse train irradiation (1.1 J, 3 Hz, 30 pulses) and different cooling temperatures (+5 degree(s)C, 0 degree(s)C, -5 degree(s)C) were screened with clinical examination and histological evaluation at 1, 3, and 7 days after laser irradiation. The clinical effects showed that pulse train irradiation produced reproducible epidermal preservation and confinement of the thermal damage into the dermis. The different cooling temperatures did not provide detectable differences in terms of size and depth of thermal damage. New collagen synthesis was confirmed by a marked fibroblastic proliferation, detected in the lower dermis at D3 and clearly seen in the upper dermis at D7. This new laser appears to be a promising new tool for the treatment of skin laxity, solar elastosis, facial rhytids and mild reduction of wrinkles.
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Apparatus for laser slowing and cooling of molecules
2016-10-09
cooling of a new molecular species, TlF. We have also successfully acquired and assembled the parts for a custom laser system, which produces long...preliminary work on laser cooling of a new molecular species, TlF. We have also successfully acquired and assembled the parts for a custom laser system, which... custom laser system, which produces long (~200 microsecond), single-frequency pulses with energy ~1.1 Joules at 1064 nm and/or ~0.4 Joules at 532 nm
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Conduction cooled compact laser for chemcam instrument
NASA Astrophysics Data System (ADS)
Faure, B.; Saccoccio, M.; Maurice, S.; Durand, E.; Derycke, C.
2017-11-01
A new conduction cooled compact laser for Laser Induced Breakdown Spectroscopy (LIBS) on Mars is presented. The laser provides pulses with energy higher than 30mJ at 1μm of wavelength with a good spatial quality. Three development prototypes of this laser have been built and functional and environmental tests have been done. Then, the Qualification and Flight models have been developed and delivered. A spare model is now developed. This laser will be mounted on the ChemCam Instrument of the NASA mission MSL 2009. ChemCam Instrument is developed in collaboration between France (CESR and CNES) and USA (LANL). The goal of this Instrument is to study the chemical composition of Martian rocks. A laser source (subject of this presentation) emits a pulse which is focused by a telescope. It creates a luminous plasma on the rock; the light of this plasma is then analysed by three spectrometers to obtain information on the composition of the rock. The laser source is developed by the French company Thales Laser, with a technical support from CNES and CESR. This development is funded by CNES. The laser is compact, designed to work in burst mode. It doesn't require any active cooling.
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Laser cooling of BH and GaF: insights from an ab initio study.
Gao, Yu-feng; Gao, Tao
2015-04-28
The feasibility of laser cooling BH and GaF is investigated using ab initio quantum chemistry. The ground state X (1)Σ(+) and first two excited states (3)Π and (1)Π of BH and GaF are calculated using the multireference configuration interaction (MRCI) level of theory. For GaF, the spin-orbit coupling effect is also taken into account in the electronic structure calculations at the MRCI level. Calculated spectroscopic constants for BH and GaF show good agreement with available theoretical and experimental results. The highly diagonal Franck-Condon factors (BH: f00 = 0.9992, f11 = 0.9908, f22 = 0.9235; GaF: f00 = 0.997, f11 = 0.989, f22 = 0.958) for the (1)Π (v' = 0-2) → X (1)Σ(+) (v = 0-2) transitions in BH and GaF are determined, which are found to be in good agreement with the theoretical and experimental data. Radiative lifetime calculations of the (1)Π (v' = 0-2) state (BH: 131, 151, and 187 ns; GaF: 2.26, 2.36, and 2.48 ns) are found to be short enough for rapid laser cooling. The proposed laser cooling schemes that drive the (1)Π (v' = 0) → X (1)Σ(+) (v = 0) transition use just one laser wavelength λ00 (BH: 436 nm, GaF: 209 nm). Though the cooling wavelength of GaF is deep in the UVC, a frequency quadrupled Ti:sapphire laser (189-235 nm) could be capable of generating useful quantities of light at this wavelength. The present results indicate that BH and GaF are two good choices of molecules for laser cooling.
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Laser cooling of a trapped two-component Fermi gas
DOE Office of Scientific and Technical Information (OSTI.GOV)
Idziaszek, Z.; Centrum Fizyki Teoretycznej, Polska Akademia Nauk, 02-668 Warsaw; Santos, L.
2003-04-01
We study the collective Raman cooling of a trapped two-component Fermi gas using quantum master equation in the festina lente regime, where the heating due to photon reabsorption can be neglected. The Monte Carlo simulations show that three-dimensional temperatures of the order of 0.008T{sub F} can be achieved. We analyze the heating related to background losses, and show that our laser-cooling scheme can maintain the temperature of the gas without significant additional losses.
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Nonablative laser treatment of facial rhytides
NASA Astrophysics Data System (ADS)
Lask, Gary P.; Lee, Patrick K.; Seyfzadeh, Manouchehr; Nelson, J. Stuart; Milner, Thomas E.; Anvari, Bahman; Dave, Digant P.; Geronemus, Roy G.; Bernstein, Leonard J.; Mittelman, Harry; Ridener, Laurie A.; Coulson, Walter F.; Sand, Bruce; Baumgarder, Jon; Hennings, David R.; Menefee, Richard F.; Berry, Michael J.
1997-05-01
The purpose of this study is to evaluate the safety and effectiveness of the New Star Model 130 neodymium:yttrium aluminum garnet (Nd:YAG) laser system for nonablative laser treatment of facial rhytides (e.g., periorbital wrinkles). Facial rhytides are treated with 1.32 micrometer wavelength laser light delivered through a fiberoptic handpiece into a 5 mm diameter spot using three 300 microsecond duration pulses at 100 Hz pulse repetition frequency and pulse radiant exposures extending up to 12 J/cm2. Dynamic cooling is used to cool the epidermis selectively prior to laser treatment; animal histology experiments confirm that dynamic cooling combined with nonablative laser heating protects the epidermis and selectively injures the dermis. In the human clinical study, immediately post-treatment, treated sites exhibit mild erythema and, in a few cases, edema or small blisters. There are no long-term complications such as marked dyspigmentation and persistent erythema that are commonly observed following ablative laser skin resurfacing. Preliminary results indicate that the severity of facial rhytides has been reduced, but long-term follow-up examinations are needed to quantify the reduction. The mechanism of action of this nonablative laser treatment modality may involve dermal wound healing that leads to long- term synthesis of new collagen and extracellular matrix material.
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NASA Astrophysics Data System (ADS)
Chang, Chun-Hung; Fried, Nathaniel M.
2016-02-01
Infrared lasers have been used in combination with applied cooling methods to preserve superficial skin layers during cosmetic surgery. Similarly, combined laser irradiation and tissue cooling may also allow development of minimally invasive laser therapies beyond dermatology. This study compares diffusing, side-firing, and radial delivery laser balloon catheter designs for creation of subsurface lesions in tissue, ex vivo, using a near-IR laser and applied contact cooling. An Ytterbium fiber laser with 1075 nm wavelength delivered energy through custom built 18 Fr (6-mm-OD) balloon catheters incorporating either 10-mm-long diffusing fiber tip, 90 degree side-firing fiber, or radial delivery cone mirror, through a central lumen. A chilled solution was flowed through a separate lumen into 9-mm-diameter balloon to keep probe cooled at 7°C. Porcine liver tissue samples were used as preliminary tissue model for immediate observation of thermal lesion creation. The diffusing fiber produced subsurface thermal lesions measuring 49.3 +/- 10.0 mm2 and preserved 0.8 +/- 0.1 mm of surface tissue. The side-firing fiber produced subsurface thermal lesions of 2.4 +/- 0.9 mm2 diameter and preserved 0.5 +/- 0.1 mm of surface tissue. The radial delivery probe assembly failed to produce subsurface thermal lesions, presumably due to the small effective spot diameter at the tissue surface, which limited optical penetration depth. Optimal laser power and irradiation time measured 15 W and 100 s for diffusing fiber and 1.4 W and 20 s, for side-firing fiber, respectively. Diffusing and side-firing laser balloon catheter designs provided subsurface thermal lesions in tissue. However, the divergent laser beam in both designs limited the ability to preserve a thicker layer of tissue surface. Further optimization of laser and cooling parameters may be necessary to preserve thicker surface tissue layers.
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Dental ablation with 1064 nm, 500 ps, Diode pumped solid state laser: A preliminary study.
Sozzi, Michele; Fornaini, Carlo; Cucinotta, Annamaria; Merigo, Elisabetta; Vescovi, Paolo; Selleri, Stefano
2013-01-01
The Er:YAG laser in conservative dentistry is. good alternative to conventional instruments. Though several studies show the advantages of these devices, some drawbacks and unsolved problems are still present, such as the cost of the device and the large dimensions of the equipment. In the present study, the effectiveness of dental surface ablation with a picosecond infrared diode-pumped solid-state (DPSS) laser was investigated. In vitro tests on extracted human teeth were carried out, with assessment of the ablation quality in the tooth and thermal increase inside the pulp chamber. A solid-state picosecond laser was used for the experiments. The samples were exposed to laser energy at 1064 nm at a frequency of 30 kHz and a 500 ps pulse width. The target teeth were cooled during exposures. The internal temperature of the pulp chamber was monitored with. thermocouple. Optical microscope images showed effective ablation with the absence of carbonisation and micro-cracks. The cooling maintained the temperature rise in the pulp chamber below the permitted 5.5°C. The main problem with the use of lasers in dentistry when teeth are the target is the heat generated in the pulp chamber of the target teeth. With lasers operating in the femtosecond mode, a better management of the internal temperature is possible, but is offset by the high cost of such devices. With the ps domain system used in the present study together with cooling using chilled water, effective and clean ablation could be achieved with a controlled thermal effect in the pulp chamber. In this preliminary study with a picosecond domain DPSS laser using water cooling for the target, effective hard tissue ablation was achieved keeping the thermal increase in the pulp within the permitted range. The results suggest that this system could be used in clinical practice with appropriate modifications.
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Dew point effect of cooled hydrogel pads on human stratum corneum biosurface.
Xhauflaire-Uhoda, Emmanuelle; Paquet, Philippe; Piérard, Gérald E
2008-01-01
Cooled hydrogel pads are used to prevent overheating effects of laser therapy. They do not induce cold injuries to the skin, but their more subtle physiological effects have not been thoroughly studied. To describe the changes in transepidermal water loss and electrometric properties of the skin surface following application of cooled hydrogel pads. Measurements were performed on normal forearm skin of 27 healthy volunteers and on freshly excised skin from abdominoplasty. LaserAid hydrogel pads cooled to 4 degrees C were placed for 15 min on the forearm skin. Measurements of transepidermal water loss (TEWL) and electrometric properties (Corneometer, Nova DPM 900) were performed before application and after removal of the cooled pads. A consistent increase in corneometer units, dermal phase meter (DPM) values and TEWL were recorded at removal of the cooled hydrogel pads. Both the in vivo and in vitro assessments brought similar information. The similar changes disclosed in vitro and in vivo suggest that a common physical process is operating in these conditions. The observed phenomenon is opposite to the predicted events given by the Arrhenius law probably because of the combination of cooling and occlusion by the pads. A dew point effect (air temperature at which relative humidity is maximal) is likely involved in the moisture content of the stratum corneum. Thus, the biological impact of using cooling hydrogel pads during laser therapy is different from the effect of a cryogenic spray cooling procedure. The better preservation of the water balance in the stratum corneum by the cooled hydrogel pads could have a beneficial esthetic effect on laser treated areas. (c) 2008 S. Karger AG, Basel.
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Towards Laser Cooling Trapped Ions with Telecom Light
NASA Astrophysics Data System (ADS)
Dungan, Kristina; Becker, Patrick; Donoghue, Liz; Liu, Jackie; Olmschenk, Steven
2015-05-01
Quantum information has many potential applications in communication, atomic clocks, and the precision measurement of fundamental constants. Trapped ions are excellent candidates for applications in quantum information because of their isolation from external perturbations, and the precise control afforded by laser cooling and manipulation of the quantum state. For many applications in quantum communication, it would be advantageous to interface ions with telecom light. We present progress towards laser cooling and trapping of doubly-ionized lanthanum, which should require only infrared, telecom-compatible light. Additionally, we present progress on optimization of a second-harmonic generation cavity for laser cooling and trapping barium ions, for future sympathetic cooling experiments. This research is supported by the Army Research Office, Research Corporation for Science Advancement, and Denison University.
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Temperature distribution of laser crystal in end-pumped DPSSL
NASA Astrophysics Data System (ADS)
Zheng, Yibo; Jia, Liping; Zhang, Lei; Wen, Jihua; Kang, Junjian
2009-11-01
The temperature distribution in different cooling system was studied. A thermal distribution model of laser crystal was established. Based on the calculation, the temperature distribution and deformation of ND:YVO4 crystal in different cooling system were obtained. When the pumping power is 2 W and the radius of pumping beams is 320μm, the temperature distribution and end face distortion of the laser crystal are lowest by using side directly hydrocooling method. The study shows that, the side directly hydrocooling method is a more efficient method to control the crystal temperature distribution and reduce the thermal effect.
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Simulation of Cooling Rate Effects on Ti-48Al-2Cr-2Nb Crack Formation in Direct Laser Deposition
NASA Astrophysics Data System (ADS)
Yan, Lei; Li, Wei; Chen, Xueyang; Zhang, Yunlu; Newkirk, Joe; Liou, Frank; Dietrich, David
2017-03-01
Transient temperature history is vital in direct laser deposition (DLD) as it reveals the cooling rate at specific temperatures. Cooling rate directly relates to phase transformation and types of microstructure formed in deposits. In this paper, finite element analysis simulation was employed to study the transient temperature history and cooling rate at different experimental setups in the Ti-48Al-2Cr-2Nb DLD process. An innovative prediction strategy was developed to model with a moving Gaussian distribution heat source and element birth and death technology in ANSYS®, and fabricate crack-free deposits. This approach helps to understand and analyze the impact of cooling rate and also explain phase information gathered from x-ray diffraction.
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Lewis, Owen; Stogran, Edmund M.
1980-01-01
Laser apparatus is described wherein an active laser element, such as the disc of a face-pumped laser, is mounted in a housing such that the weight of the element is supported by glass spheres which fill a chamber defined in the housing between the walls of the housing and the edges of the laser element. The uniform support provided by the spheres enable the chamber and the pump side of the laser element to be sealed without affecting the alignment or other optical properties of the laser element. Cooling fluid may be circulated through the sealed region by way of the interstices between the spheres. The spheres, and if desired also the cooling fluid may contain material which absorbs radiation at the wavelength of parasitic emissions from the laser element. These parasitic emissions enter the spheres through the interface along the edge surface of the laser element and it is desirable that the index of refraction of the spheres and cooling fluid be near the index of refraction of the laser element. Thus support, cooling, and parasitic suppression functions are all accomplished through the use of the arrangement.
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NASA Astrophysics Data System (ADS)
Cilip, Christopher Michael
Development of a noninvasive vasectomy technique may eliminate male fear of complications (incision, bleeding, infection, and scrotal pain) and result in a more popular procedure. These studies build off previous studies that report the ability to thermally target tissue substructures with near infrared laser radiation while maintaining a healthy superficial layer of tissue through active surface cooling. Initial studies showed the ability to increase the working depth compared to that of common dermatological procedures and the translation into an ex vivo canine model targeting the vas deferens in a noninvasive laser vasectomy. Laser and cooling parameter optimization was required to determine the best possible wavelength for a safe transition to an in vivo canine model. Optical clearing agents were investigated as a mechanism to decrease tissue scattering during in vivo procedures to increase optical penetration depth and reduce the overall power required. Optical and thermal computer models were developed to determine the efficacy for a successful transition into a human model. Common clinical imaging modalities (ultrasound, high frequency ultrasound, and optical coherence tomography) were tested as possible candidates for real-time imaging feedback to determine surgical success. Finally, a noninvasive laser vasectomy prototype clamp incorporating laser, cooling, and control in a single package was designed and tested in vivo. Occlusion of the canine vas deferens able to withstand physiological burst pressures measured postoperative was shown during acute and chronic studies. This procedure is ready for azoospermia and recanalization studies in a clinical setting.
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Motional studies of one and two laser-cooled trapped ions for electric-field sensing applications
NASA Astrophysics Data System (ADS)
Domínguez, F.; Gutiérrez, M. J.; Arrazola, I.; Berrocal, J.; Cornejo, J. M.; Del Pozo, J. J.; Rica, R. A.; Schmidt, S.; Solano, E.; Rodríguez, D.
2018-03-01
We have studied the dynamics of one and two laser-cooled trapped ?Ca? ions by applying electric fields of different nature along the axial direction of the trap, namely, driving the motion with a harmonic dipolar field, or with white noise. These two types of driving induce distinct motional states of the axial modes: a coherent oscillation with the dipolar field, or an enhanced Brownian motion due to an additional contribution to the heating rate from the electric noise. In both scenarios, the sensitivity of an isolated ion and a laser-cooled two-ion crystal has been evaluated and compared. The analysis and understanding of this dynamics is important towards the implementation of a novel Penning trap mass-spectroscopy technique based on optical detection, aiming at improving precision and sensitivity.
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Injection locking of a high power ultraviolet laser diode for laser cooling of ytterbium atoms
DOE Office of Scientific and Technical Information (OSTI.GOV)
Hosoya, Toshiyuki; Miranda, Martin; Inoue, Ryotaro
2015-07-15
We developed a high-power laser system at a wavelength of 399 nm for laser cooling of ytterbium atoms with ultraviolet laser diodes. The system is composed of an external cavity laser diode providing frequency stabilized output at a power of 40 mW and another laser diode for amplifying the laser power up to 220 mW by injection locking. The systematic method for optimization of our injection locking can also be applied to high power light sources at any other wavelengths. Our system does not depend on complex nonlinear frequency-doubling and can be made compact, which will be useful for providing light sources formore » laser cooling experiments including transportable optical lattice clocks.« less
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Tunnell, J W; Nelson, J S; Torres, J H; Anvari, B
2000-01-01
Higher laser fluences than currently used in therapy (5-10 J/cm(2)) are expected to result in more effective treatment of port wine stain (PWS) birthmarks. However, higher incident fluences increase the risk of epidermal damage caused by absorption of light by melanin. Cryogen spray cooling offers an effective method to reduce epidermal injury during laser irradiation. The objective of this study was to determine whether high laser incident fluences (15-30 J/cm(2)) could be used while still protecting the epidermis in ex vivo human skin samples. Non-PWS skin from a human cadaver was irradiated with a Candela ScleroPlus Laser (lambda = 585 nm; pulse duration = 1.5 msec) by using various incident fluences (8-30 J/cm(2)) without and with cryogen spray cooling (refrigerant R-134a; spurt durations: 40-250 msec). Assessment of epidermal damage was based on histologic analysis. Relatively short spurt durations (40-100 msec) protected the epidermis for laser incident fluences comparable to current therapeutic levels (8-10 J/cm(2)). However, longer spurt durations (100-250 msec) increased the fluence threshold for epidermal damage by a factor of three (up to 30 J/cm(2)) in these ex vivo samples. Results of this ex vivo study show that epidermal protection from high laser incident fluences can be achieved by increasing the cryogen spurt duration immediately before pulsed laser exposure. Copyright 2000 Wiley-Liss, Inc.
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Preparation of a high concentration of lithium-7 atoms in a magneto-optical trap
DOE Office of Scientific and Technical Information (OSTI.GOV)
Zelener, B. B., E-mail: bobozel@mail.ru; Saakyan, S. A.; Sautenkov, V. A.
2014-11-15
This study is aimed at obtaining high concentration of optically cooled lithium-7 atoms for preparing strongly interacting ultracold plasma and Rydberg matter. A special setup has been constructed, in which two high-power semiconductor lasers are used to cool lithium-7 atoms in a magneto-optical trap. At an optimum detuning of the cooling laser frequency and a magnetic field gradient of 35 G/cm, the concentration of ultracold lithium-7 atoms reaches about 10{sup 11} cm{sup −3}. Additional independent information about the concentration and number of ultracold lithium-7 atoms on different sublevels of the ground state was obtained by using of an additional probingmore » laser.« less
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Svaasand, Lars O; Nelson, J Stuart
2004-01-01
The physical basis for optimization of wavelength, pulse duration, and cooling for laser-induced selective photothermolysis of hair follicles in human skin is discussed. The results indicate that the most important optimization parameter is the cooling efficiency of the technique utilized for epidermal protection. The optical penetration is approximately the same for lasers at 694, 755, and 800 nm. The penetration of radiation from Nd:yttrium-aluminum-garnet lasers at 1064 nm is, however, somewhat larger. Photothermal damage to the follicle is shown to be almost independent of laser pulse duration up to 100 ms. The results reveal that epidermal cooling by a 30-80-ms-long cryogen spurt immediately before laser exposure is the only efficient technique for laser pulse durations less than 10 ms. For longer pulse durations in the 30-100 ms range, protection can be done efficiently by skin cooling during laser exposure. For laser pulses of 100 ms, an extended precooling period, e.g., by bringing a cold object into good thermal contact with the skin for about 1 s, can be of value. Thermal quenching of laser induced epidermal temperature rise after pulsed exposure can most efficiently be done with a 20 ms cryogen spurt applied immediately after irradiation. (c) 2004 Society of Photo-Optical Instrumentation Engineers.
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All-diode-laser cooling of Sr+ isotope ions for analytical applications
NASA Astrophysics Data System (ADS)
Jung, Kyunghun; Yamamoto, Kazuhiro; Yamamoto, Yuta; Miyabe, Masabumi; Wakaida, Ikuo; Hasegawa, Shuichi
2017-06-01
Trapping and cooling of Sr+ isotope ions by an all-diode-laser system has been demonstrated in order to develop a novel mass spectrometric technique in combination with ion trap-laser cooling. First, we constructed external cavity diode lasers and associated stabilization apparatus for laser cooling of Sr+ ions. The transition frequencies confirmed by optogalvanic spectroscopy enabled successful cooling of 88Sr+ ions. An image of two trapped ions has been captured by CCD camera. Minor isotopes, 84Sr+ and 86Sr+, were also cooled and trapped. From an analysis of the observed spectra of a string crystal of each isotope, the isotope shifts of the cooling transition (5s 2S1/2 → 5p 2P1/2) of Sr+ ions were determined to be +371(8) MHz for Δν84-88 and +169(8) MHz for Δν86-88. In the case of the repumping transition (4d 2D3/2 → 5p 2P1/2), Δν84-88 and Δν86-88 were measured to be -833(6) and -400(5) MHz, respectively. These values are in good agreement with previously reported values.
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LD side-pumped Nd:YAG Q-switched laser without water cooling
NASA Astrophysics Data System (ADS)
Ling, Ming; Jin, Guang-yong; Tan, Xue-chun; Wu, Zhi-chao; Liang, Zhu
2009-07-01
A novel LD side-pumped Nd:YAG Q-switched solid-state laser, which made use of the special pumping strcture with conductive cooling instead of water cooling, was investigated.After selecting an appropriate length and diameter of Nd:YAG laser crystal rod and using three groups of laser diode centimeter bar which was composed by 12 laser diodes and uniformly arranged according to the angle of 120°,side-pumping structure of laser was accomplished.Adopting plano-concave resonator ,mending double end face of laser crystal and designing heat-stability resonator made the resonator steadily oscillate.Laser crystal rod which was tight fastened by copper net was conductively cooled and radiation block was furnished on the external of copper net for increasing the radiation capacity.High reflection gold film was plated on the cooling wall in the opposite way of pumping light, so that the laser crystal was uniformly pumped and the laser with low order mode output.Making the use of pillar lens focus and ray trace computing, reasonable parameters were caculated to couple pumping light to laser with high-efficiency.It was the electrooptic Q-switched which was made to be micro-integration eliminating voltage by KD*P crystal that improved the ratio between acting and unacting.Inner heat radiated from laser in good time with TE cooler and the laser ran at constant temperature with water cooling when the big external heat sink emanated a steady heat to periphery. Experiments revealed that the syetem pumping efficiency riseed by 18% and the laser threshold energy was 192 mJ under the condition of this novel pumping structure. The low mode output of 10-12ns pulse width and the maximum output energy of 98 mJ was achieved with an incident pump energy of 720 mJ in 1064nm.The optical-to-optical conversion efficiency was up to 13. 6 %,and the power instability in 24 h was better than +/-1. 7 %.
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Thermal management of liquid direct cooled split disk laser
NASA Astrophysics Data System (ADS)
Yang, Huomu; Feng, Guoying; Zhou, Shouhuan
2015-02-01
The thermal effects of a liquid direct cooled split disk laser are modeled and analytically solved. The analytical solutions with the consideration of longitudinal cooling liquid temperature rise have been given to describe the temperature distribution in the split disk and cooling liquid based on the hydrodynamics and heat transfer. The influence of cooling liquid, liquid flowing velocity, thickness of cooling channel and of disk gain medium can also be got from the analytical solutions.
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Ross, Edward V; Chuang, Gary S; Ortiz, Arisa E; Davenport, Scott A
2018-04-01
High concentrations of sub-micron nanoparticles have been shown to be released during laser hair removal (LHR) procedures. These emissions pose a potential biohazard to healthcare workers that have prolonged exposure to LHR plume. We sought to demonstrate that cold sapphire skin cooling done in contact mode might suppress plume dispersion during LHR. A total of 11 patients were recruited for laser hair removal. They were treated on the legs and axilla with a 755 or 1064 nm millisecond-domain laser equipped with either (i) cryogen spray (CSC); (ii) refrigerated air (RA); or (iii) contact cooling with sapphire (CC). Concentration of ultrafine nanoparticles <1 μm were measured just before and during LHR with the three respective cooling methods. For contact cooling (CC), counts remained at baseline levels, below 3,500 parts per cubic centimeter (ppc) for all treatments. In contrast, the CSC system produced large levels of plume, peaking at times to over 400,000 ppc. The CA cooled system produced intermediate levels of plume, about 35,000 ppc (or about 10× baseline). Cold Sapphire Skin cooling with gel suppresses plume during laser hair removal, potentially eliminating the need for smoke evacuators, custom ventilation systems, and respirators during LHR. Lasers Surg. Med. 50:280-283, 2018. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.
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Progress Towards Laser Cooling of an Ultracold Neutral Plasma
NASA Astrophysics Data System (ADS)
Langin, Thomas; Gorman, Grant; Chen, Zhitao; Chow, Kyle; Killian, Thomas
2017-04-01
We report on progress towards laser-cooling of the ion component of an ultracold neutral plasma (UNP) consisting of 88Sr+. The goal of the experiment is to increase the value of the ion Coulomb Coupling Parameter, Γi, which is the ratio of the average nearest neighbor Coulomb interaction energy to the ion kinetic energy. Currently, Γi is limited to 3 in most UNP systems. We have developed a new photoionization pathway for plasma creation that starts with atoms in a magnetic trap. This allows us to create much larger plasmas (upwards of 109 atoms with a width of 4 mm). This greatly reduces the plasma expansion rate, giving more time for laser cooling. We have also installed lasers for optically pumping atoms out of dark states that are populated during laser cooling. We will discuss these new systems, along with the results of our first attempts at laser-cooling. Supported by NSF and DoE (PHY-0714603), the Air Force Office of Scientific Research (FA9550-12-1-0267), and the Shell Foundation.
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Robinson, C. Paul; Jensen, Reed J.; Cotter, Theodore P.; Boyer, Keith; Greiner, Norman R.
1988-01-01
A process and apparatus for separating isotopes by selective excitation of isotopic species of a volatile compound by tuned laser light. A highly cooled gas of the volatile compound is produced in which the isotopic shift is sharpened and defined. Before substantial condensation occurs, the cooled gas is irradiated with laser light precisely tuned to a desired wavelength to selectively excite a particular isotopic species in the cooled gas. The laser light may impart sufficient energy to the excited species to cause it to undergo photolysis, photochemical reaction or even to photoionize. Alternatively, a two-photon irradiation may be applied to the cooled gas to induce photolysis, photochemical reaction or photoionization. The process is particularly applicable to the separation of isotopes of uranium.
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Isotope separation by laser means
Robinson, C. Paul; Jensen, Reed J.; Cotter, Theodore P.; Greiner, Norman R.; Boyer, Keith
1982-06-15
A process for separating isotopes by selective excitation of isotopic species of a volatile compound by tuned laser light. A highly cooled gas of the volatile compound is produced in which the isotopic shift is sharpened and defined. Before substantial condensation occurs, the cooled gas is irradiated with laser light precisely tuned to a desired wavelength to selectively excite a particular isotopic species in the cooled gas. The laser light may impart sufficient energy to the excited species to cause it to undergo photochemical reaction or even to photoionize. Alternatively, a two-photon irradiation may be applied to the cooled gas to induce photochemical reaction or photoionization. The process is particularly applicable to the separation of isotopes of uranium and plutonium.
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NASA Astrophysics Data System (ADS)
Freitas, Nahuel; Paz, Juan Pablo
2018-03-01
We analyze the lowest achievable temperature for a mechanical oscillator coupled with a quantum refrigerator composed of a parametrically driven system that is in contact with a bosonic reservoir where the energy is dumped. We show that the cooling of the oscillator (achieved by the resonant transport of its phonon excitations into the environment) is always stopped by a fundamental heating process that is dominant at sufficiently low temperatures. This process can be described as the nonresonant production of excitation pairs. This result is in close analogy with the recent study that showed that pair production is responsible for enforcing the validity of the dynamical version of the third law of thermodynamics [Phys. Rev. E 95, 012146 (2017), 10.1103/PhysRevE.95.012146]. Interestingly, we relate our model to the ones used to describe laser cooling of a single trapped ion reobtaining the correct limiting temperatures for the regimes of resolved and nonresolved sidebands. We show that the limiting temperature for laser cooling is achieved when the cooling transitions induced by the resonant transport of excitations from the motion into the electromagnetic environment is compensated by the heating transitions induced by the creation of phonon-photon pairs.
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The effects of cooling systems on CO2-lased human enamel.
Lian, H J; Lan, W H; Lin, C P
1996-12-01
The thermal effects on dentin during CO2 laser irradiation on human enamel were investigated. To simulate the clinical practice, two cooling methods (air and water spray) were applied immediately after laser exposure, whereas one group without cooling was served as control. Three hundred and sixty uniform tooth blocks were obtained from freshly extracted human third molars. Temperature change measurements were made via electrical thermocouple implanted within the tooth block 2 mm away from the enamel surface. Experimental treatments consisted of lasing without cooling, lasing with 0.5-ml/sec water cooling, and lasing with 15-psi air cooling. Our results indicated that (1) both air- and water-cooling groups could reduce temperature elevation significantly; (2) the larger power energy resulted in the higher temperature elevation. In conclusion, for CO2 laser irradiation on human enamel both water- and air-cooling methods may be effective on prevention of thermal damage of pulp.
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Dynamic cooling during laser skin welding
NASA Astrophysics Data System (ADS)
Fried, Nathaniel M.; Walsh, Joseph T., Jr.
1999-06-01
Cryogen spray cooling of the tissue surface was investigated for laser welding applications. Benefits include reduced thermal damage to the papillary dermis and reduced operation time. Two-cm-long, full-thickness incisions were made on the backs of guinea pigs, in vivo. India ink was used as an absorber and clamps were used to appose the incision edges. Continuous-wave, 1.06-μm, Nd:YAG laser radiation was scanned over the incisions, producing ~100 ms pulses. A 4-mm-diameter laser spot was used with a constant power of 16 W. The total operation time was 60 or 120 s. Cryogen was delivered in spurt durations of 20, 60, or 100 ms, with 2 or 4 s between spurts. The working distance was approximately 12 cm, and the spray covered an area of about 5.0 x 5.0 cm. Control welds were irradiated for 20, 40, or 60 s. Total operation times were reduced from 10 min without dynamic cooling to 1 min with dynamic cooling. Optimal tensile strength was 1.7 +/- 0.7 kg/cm2, comparible to stengths of 2.1 +/- 0.7 kg/cm2 reported in previous studies without cryogen cooling (p>0.25). Thermal damage in the papillary dermis measured 320 +/- 80 μm.
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The influence of various cooling rates during laser alloying on nodular iron surface layer
NASA Astrophysics Data System (ADS)
Paczkowska, Marta; Makuch, Natalia; Kulka, Michał
2018-06-01
The results of research referring to modification of the nodular iron surface layer by laser alloying with cobalt were presented. The aim of this study was to analyze the possibilities of cobalt implementation into the surface layer of nodular iron in various laser heat treatment conditions (by generating different cooling rates of melted surface layer). The modified surface layer of nodular iron was analyzed with OM, SEM, TEM, XRD, EDS and Vickers microhardness tester. The modified surface layer of nodular iron after laser alloying consisted of: the alloyed zone (melted with cobalt), the transition zone and the hardened zone from solid state. The alloyed zone was characterized by higher microstructure homogeneity - in contrast to the transition and the hardened zones. All the alloyed zones contained a dendritic microstructure. Dendrites consisted of martensite needles and retained austenite. Cementite was also detected. It was stated, that due to similar dimension of iron and cobalt atoms, their mutual replacement in the crystal lattice could occur. Thus, formation of phases based on α solution: Co-Fe (44-1433) could not be excluded. Although cobalt should be mostly diluted in solid solutions (because of its content in the alloyed zone), the other newly formed phases as Co (ε-hex.), FeC and cobalt carbides: Co3C, CoC0.25 could be present in the alloyed zones as a result of unique microstructure creation during laser treatment. Pearlite grains were observed in the zone, formed using lower power density of the laser beam and its longer exposition time. Simply, such conditions resulted in the cooling rate which was lower than critical cooling rate. The alloyed zones, produced at a higher cooling rate, were characterized by better microstructure homogeneity. Dendrites were finer in this case. This could result from a greater amount of crystal nuclei appearing at higher cooling rate. Simultaneously, the increased amount of γ-Fe and Fe3C precipitates was expected in the alloyed zone formed at higher cooling rates. The hardness of nodular iron surface layer, alloyed with cobalt, was up to 4-times higher than the hardness of core material. The hardness of alloyed zones strongly depended on laser treatment conditions. In the case of lower cooling rate, lower hardness was observed due to more coarse-grained microstructure and a presence of pearlite. The hardness of the alloyed zone increased (from 850 to 950HV0.1) together with the increasing cooling rate (from 2 · 103 to nearly 9 · 103 °C/s). Laser treatment enabled a formation of surface layers on nodular iron, alloyed with cobalt. The microstructure of such a surface layer could be controlled by the laser processing parameters. High hardness and fine microstructure of the laser-alloyed nodular iron with cobalt should result in higher resistance to wear, corrosion and even (due to effect of cobalt addition) elevated temperatures during operation conditions of machine parts.
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Chlebicki, Cara A.; Protsenko, Dmitry E.; Wong, Brian J.
2014-01-01
Previous studies have demonstrated the feasibility of laser irradiation (λ=1.45 μm) in tandem with cryogen spray cooling (CSC) to reshape rabbit auricular cartilage using total energy density of 14 J/cm2. The aim of this study was to further explore and identify the dosimetry parameter space for laser output energy, CSC duration, and treatment cycles required to achieve shape change while limiting skin and cartilage injury. Ten New Zealand white rabbits were treated with the 1.45 μm diode laser combined with cryogen spray cooling (Candela Smoothbeam™, Candela Co., Wayland, MA). The ear's central portion was bent around a cylindrical jig and irradiated in consecutive spots of 6 mm diameter (13 J/cm2 or 14 J/cm2 per spot) along 3 rows encompassing the bend. CSC was delivered during irradiation in cycles consisting of 25-35 ms. At thin and thick portions of the ear, 4-7 and 6-10 treatment cycles were delivered, respectively. After surgery, ears were examined and splinted for 6 weeks. Treatment parameters resulting in acceptable (Grades 1 & 2) and unacceptable (Grade 3) skin injuries for thick and thin regions were identified and shape change was observed. Confocal and histological analysis of cartilage tissue revealed several outcomes correlating to laser dosimetry, CSC duration, and treatment cycles. These outcomes included expansion of cartilage layers (thickening), partial cartilage injuries, and full thickness cartilage injuries. We determined therapy thresholds for laser output energy, cryogen spray cooling duration, and treatment cycles in the rabbit auricular model. These parameters are a starting point for future clinical procedures aimed at correcting external ear deformities. PMID:24202858
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Chlebicki, Cara A; Protsenko, Dmitry E; Wong, Brian J
2014-05-01
Previous studies have demonstrated the feasibility of laser irradiation (λ = 1.45 μm) in tandem with cryogen spray cooling (CSC) to reshape rabbit auricular cartilage using a total energy density of 14 J/cm(2). The aim of this study was to further explore and identify the dosimetry parameter space for laser output energy, CSC duration, and treatment cycles required to achieve shape change while limiting skin and cartilage injury. Ten New Zealand white rabbits were treated with the 1.45 μm diode laser combined with cryogen spray cooling (Candela Smoothbeam™, Candela Co., Wayland, MA, USA). The ear's central portion was bent around a cylindrical jig and irradiated in consecutive spots of 6 mm diameter (13 or 14 J/cm(2) per spot) along three rows encompassing the bend. CSC was delivered during irradiation in cycles consisting of 25-35 ms. At thin and thick portions of the ear, 4-7 and 6-10 treatment cycles were delivered, respectively. After surgery, ears were examined and splinted for 6 weeks. Treatment parameters resulting in acceptable (grades 1 and 2) and unacceptable (grade 3) skin injuries for thick and thin regions were identified, and shape change was observed. Confocal and histological analysis of cartilage tissue revealed several outcomes correlating to laser dosimetry, CSC duration, and treatment cycles. These outcomes included expansion of cartilage layers (thickening), partial cartilage injuries, and full-thickness cartilage injuries. We determined therapy thresholds for laser output energy, cryogen spray cooling duration, and treatment cycles in the rabbit auricular model. These parameters are a starting point for future clinical procedures aimed at correcting external ear deformities.
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Triatomic molecules laser-cooled
NASA Astrophysics Data System (ADS)
2017-06-01
Molecules containing three atoms have been laser-cooled to ultracold temperatures for the first time. John Doyle and colleagues at Harvard University in the US used a technique called Sisyphus cooling to chill an ensemble of about a million strontium-monohydroxide molecules to 750 μK.
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Investigation of RF excited CW CO2 waveguide lasers local oscillator - RF excitation
NASA Technical Reports Server (NTRS)
Hochuli, U.
1988-01-01
A new local oscillator housing was built which seems to have improved laser life. Laser cooling was changed from internal water cooling to the more convenient thermal contact cooling. At the present time, a conclusion can not be made if the 20 percent reduction in power output is the result of poorer cooling or poorer grating alignment. The coupling-starting network was improved from 55 to about 90 percent. It can be adjusted by varying trimmers C sub 1 and C sub 2 to match RF power levels between 10 and 30 W. If the laser admittance changes greatly with laser life rematching will have to be achieved by remote control for space applications. The same holds true if the RF power level has to be changed with a maximum efficiency constraint.
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Diode laser (980nm) cartilage reshaping
NASA Astrophysics Data System (ADS)
El Kharbotly, A.; El Tayeb, T.; Mostafa, Y.; Hesham, I.
2011-03-01
Loss of facial or ear cartilage due to trauma or surgery is a major challenge to the otolaryngologists and plastic surgeons as the complicated geometric contours are difficult to be animated. Diode laser (980 nm) has been proven effective in reshaping and maintaining the new geometric shape achieved by laser. This study focused on determining the optimum laser parameters needed for cartilage reshaping with a controlled water cooling system. Harvested animal cartilages were angulated with different degrees and irradiated with different diode laser powers (980nm, 4x8mm spot size). The cartilage specimens were maintained in a deformation angle for two hours after irradiation then released for another two hours. They were serially measured and photographed. High-power Diode laser irradiation with water cooling is a cheep and effective method for reshaping the cartilage needed for reconstruction of difficult situations in otorhinolaryngologic surgery. Key words: cartilage,diode laser (980nm), reshaping.
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Conduction cooled compact laser for the chemcam instrument
NASA Astrophysics Data System (ADS)
Durand, E.; Derycke, C.; Simon-Boisson, C.; Muller, S.; Faure, B.; Saccoccio, M.; Maurice, M.
2017-11-01
A new conduction cooled compact laser for laser induced spectroscopy on the Mars Science Laboratory (MSL) to be launched in 2009 is presented. An oscillator combined to amplifiers generates 30mJ at 1μm with a good spatial quality. Development prototype of this laser has been built and characterized. Environmental testing of this prototype is also reported.
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Probing Molecular Ions With Laser-Cooled Atomic Ions
2017-10-11
Sept. 23, 2015 Precision Chemical Dynamics and Quantum Control of Ultracold Molecular Ion Reactions , Cold Molecular Ions at the Quantum limit (COMIQ...ken.brown@chemistry.gatech.edu This work solved an old mystery about the lifetime of Ca+ due to reactions with background gases in laser-cooling experiments...Relative to other alkaline earths, Ca+ had a much slower reaction rate. We discovered the reason is that the Doppler cooling laser is near
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Robinson, C.P.; Reed, J.J.; Cotter, T.P.; Boyer, K.; Greiner, N.R.
1975-11-26
A process and apparatus for separating isotopes by selective excitation of isotopic species of a volatile compound by tuned laser light is described. A highly cooled gas of the volatile compound is produced in which the isotopic shift is sharpened and defined. Before substantial condensation occurs, the cooled gas is irradiated with laser light precisely tuned to a desired wavelength to selectively excite a particular isotopic species in the cooled gas. The laser light may impart sufficient energy to the excited species to cause it to undergo photolysis, photochemical reaction or even to photoionize. Alternatively, a two-photon irradiation may be applied to the cooled gas to induce photolysis, photochemical reaction or photoionization. The process is particularly applicable to the separation of isotopes of uranium.
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High duty cycle hard soldered kilowatt laser diode arrays
NASA Astrophysics Data System (ADS)
Klumel, Genady; Karni, Yoram; Oppenheim, Jacob; Berk, Yuri; Shamay, Moshe; Tessler, Renana; Cohen, Shalom
2010-02-01
High-brightness laser diode arrays operating at a duty cycle of 10% - 20% are in ever-increasing demand for the optical pumping of solid state lasers and directed energy applications. Under high duty-cycle operation at 10% - 20%, passive (conductive) cooling is of limited use, while micro-coolers using de-ionized cooling water can considerably degrade device reliability. When designing and developing actively-cooled collimated laser diode arrays for high duty cycle operation, three main problems should be carefully addressed: an effective local and total heat removal, a minimization of packaging-induced and operational stresses, and high-precision fast axis collimation. In this paper, we present a novel laser diode array incorporating a built-in tap water cooling system, all-hard-solder bonded assembly, facet-passivated high-power 940 nm laser bars and tight fast axis collimation. By employing an appropriate layout of water cooling channels, careful choice of packaging materials, proper design of critical parts, and active optics alignment, we have demonstrated actively-cooled collimated laser diode arrays with extended lifetime and reliability, without compromising their efficiency, optical power density, brightness or compactness. Among the key performance benchmarks achieved are: 150 W/bar optical peak power at 10% duty cycle, >50% wallplug efficiency and <1° collimated fast axis divergence. A lifetime of >0.5 Ghots with <2% degradation has been experimentally proven. The laser diode arrays have also been successfully tested under harsh environmental conditions, including thermal cycling between -20°C and 40°C and mechanical shocks at 500g acceleration. The results of both performance and reliability testing bear out the effectiveness and robustness of the manufacturing technology for high duty-cycle laser arrays.
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Proposal for Laser Cooling of Alkaline Earth Monoalkoxide Free Radicals
NASA Astrophysics Data System (ADS)
Baum, Louis; Kozyryev, Ivan; Matsuda, Kyle; Doyle, John M.
2016-05-01
Cold samples of polyatomic molecules will open new avenues in physics, chemistry, and quantum science. Non-diagonal Franck-Condon factors, technically challenging wavelengths, and the lack of strong electronic transitions inhibit direct laser cooling of nonlinear molecules. We identify a scheme for optical cycling in certain molecules with six or more atoms. Replacing hydrogen in alcohols with an alkaline earth metal (M) leads to alkaline earth monoalkoxide free radicals (MOR), which have favorable properties for laser cooling. M-O bond is very ionic, so the metal orbitals are slightly affected by the nature of R on the ligand. Diagonal Franck-Condon factors, laser accessible transitions, and a small hyperfine structure make MOR molecules suitable for laser cooling. We explore a scheme for optical cycling on the A - X transition of SrOCH3 . Molecules lost to dark vibrational states will be repumped on the B - X transition. Extension to larger species is possible through expansion of the R group since transitions involve the promotion of the metal-centered nonbonding valence electron. We will detail our estimations of the Franck-Condon factors, simulations of the cooling process and describe progress towards the Doppler cooling of MOR polyatomics.
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Method and system for powering and cooling semiconductor lasers
DOE Office of Scientific and Technical Information (OSTI.GOV)
Telford, Steven J; Ladran, Anthony S
A semiconductor laser system includes a diode laser tile. The diode laser tile includes a mounting fixture having a first side and a second side opposing the first side and an array of semiconductor laser pumps coupled to the first side of the mounting fixture. The semiconductor laser system also includes an electrical pulse generator thermally coupled to the diode bar and a cooling member thermally coupled to the diode bar and the electrical pulse generator.
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Ruggedized microchannel-cooled laser diode array with self-aligned microlens
Freitas, Barry L.; Skidmore, Jay A.
2003-11-11
A microchannel-cooled, optically corrected, laser diode array is fabricated by mounting laser diode bars onto Si surfaces. This approach allows for the highest thermal impedance, in a ruggedized, low-cost assembly that includes passive microlens attachment without the need for lens frames. The microlensed laser diode array is usable in all solid-state laser systems that require efficient, directional, narrow bandwidth, high optical power density pump sources.
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A Technology Demonstration Experiment for Laser Cooled Atomic Clocks in Space
NASA Technical Reports Server (NTRS)
Klipstein, W. M.; Kohel, J.; Seidel, D. J.; Thompson, R. J.; Maleki, L.; Gibble, K.
2000-01-01
We have been developing a laser-cooling apparatus for flight on the International Space Station (ISS), with the intention of demonstrating linewidths on the cesium clock transition narrower than can be realized on the ground. GLACE (the Glovebox Laser- cooled Atomic Clock Experiment) is scheduled for launch on Utilization Flight 3 (UF3) in 2002, and will be mounted in one of the ISS Glovebox platforms for an anticipated 2-3 week run. Separate flight definition projects funded at NIST and Yale by the Micro- gravity Research Division of NASA as a part of its Laser Cooling and Atomic Physics (LCAP) program will follow GLACE. Core technologies for these and other LCAP missions are being developed at JPL, with the current emphasis on developing components such as the laser and optics subsystem, and non-magnetic vacuum-compatible mechanical shutters. Significant technical challenges in developing a space qualifiable laser cooling apparatus include reducing the volume, mass, and power requirements, while increasing the ruggedness and reliability in order to both withstand typical launch conditions and achieve several months of unattended operation. This work was performed at the Jet Propulsion Laboratory under a contract with the National Aeronautics and Space Administration.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Scipioni Bertoli, Umberto; Guss, Gabe; Wu, Sheldon
We report detailed understanding of the complex melt pool physics plays a vital role in predicting optimal processing regimes in laser powder bed fusion additive manufacturing. In this work, we use high framerate video recording of Selective Laser Melting (SLM) to provide useful insight on the laser-powder interaction and melt pool evolution of 316 L powder layers, while also serving as a novel instrument to quantify cooling rates of the melt pool. The experiment was performed using two powder types – one gas- and one water-atomized – to further clarify how morphological and chemical differences between these two feedstock materialsmore » influence the laser melting process. Finally, experimentally determined cooling rates are compared with values obtained through computer simulation, and the relationship between cooling rate and grain cell size is compared with data previously published in the literature.« less
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Scipioni Bertoli, Umberto; Guss, Gabe; Wu, Sheldon; ...
2017-09-21
We report detailed understanding of the complex melt pool physics plays a vital role in predicting optimal processing regimes in laser powder bed fusion additive manufacturing. In this work, we use high framerate video recording of Selective Laser Melting (SLM) to provide useful insight on the laser-powder interaction and melt pool evolution of 316 L powder layers, while also serving as a novel instrument to quantify cooling rates of the melt pool. The experiment was performed using two powder types – one gas- and one water-atomized – to further clarify how morphological and chemical differences between these two feedstock materialsmore » influence the laser melting process. Finally, experimentally determined cooling rates are compared with values obtained through computer simulation, and the relationship between cooling rate and grain cell size is compared with data previously published in the literature.« less
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Heat Pipe Technology: A bibliography with abstracts
NASA Technical Reports Server (NTRS)
1974-01-01
This bibliography lists 149 references with abstracts and 47 patents dealing with applications of heat pipe technology. Topics covered include: heat exchangers for heat recovery; electrical and electronic equipment cooling; temperature control of spacecraft; cryosurgery; cryogenic, cooling; nuclear reactor heat transfer; solar collectors; laser mirror cooling; laser vapor cavitites; cooling of permafrost; snow melting; thermal diodes variable conductance; artery gas venting; and venting; and gravity assisted pipes.
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Laser Cooled Atomic Clocks in Space
NASA Technical Reports Server (NTRS)
Thompson, R. J.; Kohel, J.; Klipstein, W. M.; Seidel, D. J.; Maleki, L.
2000-01-01
The goals of the Glovebox Laser-cooled Atomic Clock Experiment (GLACE) are: (1) first utilization of tunable, frequency-stabilized lasers in space, (2) demonstrate laser cooling and trapping in microgravity, (3) demonstrate longest 'perturbation-free' interaction time for a precision measurement on neutral atoms, (4) Resolve Ramsey fringes 2-10 times narrower than achievable on Earth. The approach taken is: the use of COTS components, and the utilization of prototype hardware from LCAP flight definition experiments. The launch date is scheduled for Oct. 2002. The Microgravity Science Glovebox (MSG) specifications are reviewed, and a picture of the MSG is shown.
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Innovative opto-mechanical design of a laser head for compact thin-disk
NASA Astrophysics Data System (ADS)
Macúchová, Karolina; Smrž, Martin; Řeháková, Martina; Mocek, Tomáš
2016-11-01
We present recent progress in design of innovative versatile laser head for lasers based on thin-disk architecture which are being constructed at the HiLASE centre of the IOP in the Czech Republic. Concept of thin-disk laser technology allows construction of lasers providing excellent beam quality with high average output power and optical efficiency. Our newly designed thin-disk carrier and pump module comes from optical scheme consisting of a parabolic mirror and roof mirrors proposed in 90's. However, mechanical parts and a cooling system were in-house simplified and tailor-made to medium power lasers since no suitable setup was commercially available. Proposed opto-mechanical design is based on stable yet easily adjustable mechanics. The only water nozzle-cooled component is a room-temperature-operated thindisk mounted on a special cooling finger. Cooling of pump optics was replaced by heat conductive transfer from mirrors made of special Al alloy to a massive brass baseplate. Such mirrors are easy to manufacture and very cheap. Presented laser head was manufactured and tested in construction of Er and Yb doped disk lasers. Details of the latest design will be presented.
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Suppression of Laser Shot Noise Using Laser-Cooled OptoMechanical Systems
2010-04-22
that this device will be able to demonstrate squeezing in a fairly short time . Background: The goal of this effort was to create laser light with...The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing...REPORT Final report on Seedling project: "Suppression of Laser Shot Noise Using Laser -Cooled Opto-Mechanical Systems" 14. ABSTRACT 16. SECURITY
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Study of Atomic Quasi-Stable States, Decoherence And Cooling of Mesoscale Particles
NASA Astrophysics Data System (ADS)
Zhong, Changchun
Quantum mechanics, since its very beginning, has totally changed the way we understand nature. The past hundred years have seen great successes in the application of quantum physics, including atomic spectra, laser technology, condensed matter physics and the remarkable possibility for quantum computing, etc. This thesis is dedicated to a small regime of quantum physics. In the first part of the thesis, I present the studies of atomic quasi-stable states, which refer to those Rydberg states of an atom that are relatively stable in the presence of strong fields. Through spectrally probing the quasi-stable states, series of survival peaks are found. If the quasi-stable electrons were created by ultraviolet (UV) lasers with two different frequencies, the survival peaks could be modulated by continuously changing the phase difference between the UV and the IR laser. The quantum simulation, through directly solving the Schrodinger equation, matches the experimental results performed with microwave fields, and our studies should provide a guidance for future experiments. Despite the huge achievements in the application of quantum theory, there are still some fundamental problems that remain unresolved. One of them is the so-called quantum-to-classical transition, which refers to the expectation that the system behaves in a more classical manner when the system size increases. This basic question was not well answered until decoherence theory was proposed, which states that the coherence of a quantum system tends to be destroyed by environmental interruptions. Thus, if a system is well isolated from its environment, it is in principle possible to observe macroscopic quantum coherence. Quite recently, testing quantum principles in the macroscale has become a hot topic due to rapic technological developments. A very promising platform for testing macroscale quantum physics is a laser levitated nanoparticle, and cooling its mechanical motion to the ground state is the first step. In the second part of this thesis, we develop the theory of decoherence for a mesoscopic system's rotational degrees of freedom. Combining decoherence in the translational degrees of freedom, the system's shot noise heating is discussed. We then focus on cooling the nanoparticle in the laser-shot-noise-dominant regime using two different feedback cooling schemes: the force feedback cooling and the parametric feedback cooling. Both quantum and classical calculations are performed, and an exact match is observed. We also explore the parameters that could possibly affect the cooling trend, where we find that the cooling limit for both cooling schemes strongly depends on the position measurement efficiency, and it poses good questions for researchers interested in achieving ground state cooling: what is the best measurement efficiency for a given measurement setup and what can be done to get a better measurement efficiency?
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Microgravity Spray Cooling Research for High Powered Laser Applications
NASA Technical Reports Server (NTRS)
Zivich, Chad P.
2004-01-01
An extremely powerful laser is being developed at Goddard Space Flight Center for use on a satellite. This laser has several potential applications. One application is to use it for upper atmosphere weather research. In this case, the laser would reflect off aerosols in the upper atmosphere and bounce back to the satellite, where the aerosol velocities could be calculated and thus the upper atmosphere weather patterns could be monitored. A second application would be for the US. Air Force, which wants to use the laser strategically as a weapon for satellite defense. The Air Force fears that in the coming years as more and more nations gain limited space capabilities that American satellites may become targets, and the laser could protect the satellites. Regardless of the ultimate application, however, a critical step along the way to putting the laser in space is finding a way to efficiently cool it. While operating the laser becomes very hot and must be cooled to prevent overheating. On earth, this is accomplished by simply running cool tap water over the laser to keep it cool. But on a satellite, this is too inefficient. This would require too much water mass to be practical. Instead, we are investigating spray cooling as a means to cool the laser in microgravity. Spray cooling requires much less volume of fluid, and thus could be suitable for use on a satellite. We have inherited a 2.2 second Drop Tower rig to conduct our research with. In our experiments, water is pressurized with a compressed air tank and sprayed through a nozzle onto our test plate. We can vary the pressure applied to the water and the temperature of the plate before an experiment trial. The whole process takes place in simulated microgravity in the 2.2 second Drop Tower, and a high speed video camera records the spray as it hits the plate. We have made much progress in the past few weeks on these experiments. The rig originally did not have the capability to heat the test plate, but I did some heat transfer calculations and picked out a heater to order for the rig. I learned QBasic programming language to change the operating code for our drops, allowing us to rapidly cycle the spray nozzle open and closed to study the effects. We have derived an equation for flow rate vs. pressure for our experiment. We have recorded several videos of drops at different pressures, some with heated test plate and some without, and have noticed substantial differences in the liquid behavior. I have also changed the computer program to write a file with temperature vs. time profiles for the test plate, and once the necessary thermocouple comes in (it was ordered last week), we will have temperature profiles to accompany the videos. Once we have these temperature profiles to go with the videos, we will be able to see how the temperature is affected by the spray at different pressures, and how the spray changes its behavior once as the plate changes from hot to cool. With quantitative temperature data, we can then mathematically model the heat transfer from the plate to the cooling spray. Finally, we can look at the differences between trials in microgravity and those in normal earth gravity.
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Efficient Operation of Conductively Cooled Ho:Tm:LuLiF Laser Oscillator/Amplifier
NASA Technical Reports Server (NTRS)
Yu, Jirong; Bai, Yingxin; Trieu, Bo; Petros, M.; Petzar, Paul; Lee, Hyung; Singh, U.
2008-01-01
A conductively-cooled Ho:Tm:LuLiF laser oscillator generates 1.6J normal mode pulses at 10Hz with optical to optical efficiency of 20%. When the laser head module is used as the amplifier, the double-pass small-signal amplification excesses 25.
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Study of the production of unique new glasses
NASA Technical Reports Server (NTRS)
Happe, R. A.
1972-01-01
A number of high new oxide glasses have been prepared by a laser-spin melting technique where droplets are ejected from a molten mass. Techniques have been developed for measuring the optical properties of most of the new glasses so produced. A preliminary study of processing equipment for producing new glasses in a zero gravity environment onboard manned space laboratory is reported. Induction and laser melting emerge as preferred techniques for melting spheroids of new glass compositions in space. Sample calculations for power required to induction melt new glass compositions are presented. Cooling rate calculations show that radiation cooling of the high melting materials results in very short cooling times for 1/2 inch diameters to temperatures where the spheroids can be handled.
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Correction of small imperfections on white glazed china surfaces by laser radiation
NASA Astrophysics Data System (ADS)
Képíró, I.; Osvay, K.; Divall, M.
2007-07-01
A laser-assisted technique has been developed for correction of small diameter (1 mm) and shallow (0.5 mm) imperfections on the surface of gloss fired porcelain. To study the physics and establish the important parameters, artificially made holes in a porcelain sample have been first filled with correction material, then covered with raw glaze and treated by a pulsed, 7 kHz repetition rate CO 2 laser at 10.6 μm. The modification of the surface and the surrounding area have been quantified and studied with a large range of parameters of incident laser power (1-10 W), width of the laser pulses (10-125 μs) and duration of laser heating (60-480 s). Although the shine of the treated area, defined as the distribution of micro-droplets on the surface, is very similar to the untreated surfaces, the surroundings of the treated area usually show cracks. The measurement of both the spatial temperature distribution and the temporal cooling rate of the treated surface has revealed that a simple melting process always results in high gradient temperature distribution within the irradiated zone. Its inhomogeneous and fast cooling always generate at least micro-cracks on the surface within a few seconds after the laser was turned off. The duration and intensity of the laser irradiation have been then optimized in order to achieve the fastest possible melting of the surface, but without producing such high temperature gradients. To eliminate the cracks, more elaborated pre-heating and slowed-cooling-rate processes have been tried with prosperous results. These achievements complete our previous study, making possible to repair the most common surface imperfections and holes of gloss fired china samples.
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Experimental and Theoretical Studies of Laser Cooling and Emittance Control of Neutral Beams.
1987-01-31
the collective atomic recoil serves to op reduce the momentum spread of an atomic sample (laser cooling) or to produce a diffraction pattern from a...mtasured 1.5 m downstream from the OKDE interaction region, permits a measure of the ODKE momentum spread. We will discuss each of the various...spectrometer provides a real-time measure of the hydrogen flux, which can be monitored continuously during data collection . We were able to generate
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NASA Astrophysics Data System (ADS)
Bright, Robin Michael
The ability to adequately cool internal gas-turbine engine components in next-generation commercial and military aircraft is of extreme importance to the aerospace industry as the demand for high-efficiency engines continues to push operating temperatures higher. Pulsed laser-drilling is rapidly becoming the preferred method of creating cooling holes in high temperature components due a variety of manufacturing advantages of laser-drilling over conventional hole-drilling techniques. As cooling requirements become more demanding, the impact of drilling conditions on material removal behavior and subsequent effects on hole quality becomes critical. In this work, the development of emission spectroscopy as a method to probe the laser-drilling process is presented and subsequently applied to the study of material behavior of various structural aerospace materials during drilling. Specifically, emitted photons associated with energy level transitions within excited neutral atoms in material ejected during drilling were detected and analyzed. Systematic spectroscopic studies indicated that electron energy level populations and calculated electron temperatures within ejected material are dependent on both laser pulse energy and duration. Local thermal conditions detected by the developed method were related to the characteristics of ejected material during drilling and to final hole quality. Finally, methods of utilizing the observed relationships for spectroscopic process monitoring and control were demonstrated.
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Candidates for direct laser cooling of diatomic molecules with the simplest 1Σ -1Σ electronic system
NASA Astrophysics Data System (ADS)
Li, Chuanliang; Li, Yachao; Ji, Zhonghua; Qiu, Xuanbing; Lai, Yunzhong; Wei, Jilin; Zhao, Yanting; Deng, Lunhua; Chen, Yangqin; Liu, Jinjun
2018-06-01
We propose to utilize the 1Σ-1Σ electronic transition system for direct laser cooling of heteronuclear diatomic molecules. AgH, as well as its deuterium isotopolog AgD, is used as an example to illustrate the cooling schemes. Potential-energy curves and relevant molecular parameters of both AgH and AgD, including the spin-orbit constants and the electronic transition dipole moments, are determined in internally contracted multiconfiguration-reference configuration interaction calculations. The highly diagonal Franck-Condon matrices of the A 1Σ+-X 1Σ+ transitions predicted by the calculations suggest the existence of quasi-closed-cycle transitions, which renders these molecules suitable for direct laser cooling. By solving rate equations numerically, we demonstrated that both AgH and AgD molecules can be cooled from 25 K to 2 mK temperature in approximately 20 ms. Our investigation elucidates and supports the hypothesis that molecules in the simplest 1Σ-1Σ system can serve as favorable candidates for direct laser cooling.
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Cryogenic Optical Refrigeration
2012-03-22
Applications of Laser Cooling of Solids, 1st ed. (Wiley-VCH, 2009). 12. M. Sheik- Bahae and R. I . Epstein, “Optical refrigeration,” Nat. Photonics 1(12), 693–699...2007). Advances in Optics and Photonics 4, 78–107 (2012) doi:10.1364/AOP.4.000078 99 13. M. Sheik- Bahae and R. I . Epstein, “Laser cooling of solids...Sheik- Bahae and R. I . Epstein, “Can laser light cool semiconductors,” Phys. Rev. Lett. 92(24), 247403 (2004). 18. P. Asbeck, “Self-absorption effects
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Trapping, retention and laser cooling of Th3+ ions in a multisection linear quadrupole trap
NASA Astrophysics Data System (ADS)
Borisyuk, P. V.; Vasil'ev, O. S.; Derevyashkin, S. P.; Kolachevsky, N. N.; Lebedinskii, Yu. Yu.; Poteshin, S. S.; Sysoev, A. A.; Tkalya, E. V.; Tregubov, D. O.; Troyan, V. I.; Khabarova, K. Yu.; Yudin, V. I.; Yakovlev, V. P.
2017-06-01
A multisection linear quadrupole trap for Th3+ ions is described. Multiply charged ions are obtained by the laser ablation method. The possibility of trapping and retention of ˜103 ions is demonstrated in macroscopic time scales of ˜30 s. Specific features of cooling Th3+ ions on the electron transitions with wavelengths of 1088, 690 and 984 nm in Th3+ ion are discussed; a principal scheme of a setup for laser cooling is presented.
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Ultracold molecules for the masses: Evaporative cooling and magneto-optical trapping
NASA Astrophysics Data System (ADS)
Stuhl, B. K.
While cold molecule experiments are rapidly moving towards their promised benefits of precision spectroscopy, controllable chemistry, and novel condensed phases, heretofore the field has been greatly limited by a lack of methods to cool and compress chemically diverse species to temperatures below ten millikelvin. While in atomic physics these needs are fulfilled by laser cooling, magneto-optical trapping, and evaporative cooling, until now none of these techniques have been applicable to molecules. In this thesis, two major breakthroughs are reported. The first is the observation of evaporative cooling in magnetically trapped hydroxyl (OH) radicals, which potentially opens a path all the way to Bose-Einstein condensation of dipolar radicals, as well as allowing cold- and ultracold-chemistry studies of fundamental reaction mechanisms. Through the combination of an extremely high gradient magnetic quadrupole trap and the use of the OH Λ-doublet transition to enable highly selective forced evaporation, cooling by an order of magnitude in temperature was achieved and yielded a final temperature no higher than 5mK. The second breakthrough is the successful application of laser cooling and magneto-optical trapping to molecules. Motivated by a proposal in this thesis, laser cooling of molecules is now known to be technically feasible in a select but substantial pool of diatomic molecules. The demonstration of not only Doppler cooling but also two-dimensional magneto-optical trapping in yttrium (II) oxide, YO, is expected to enable rapid growth in the availability of ultracold molecules—just as the invention of the atomic magneto-optical trap stimulated atomic physics twenty-five years ago.
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Hot zone design for controlled growth to mitigate cracking in laser crystal growth
NASA Astrophysics Data System (ADS)
Zhang, Hui; Zheng, Lili; Fang, Haisheng
2011-03-01
Cracking is a major problem during large diameter crystal growth. The objective of this work is to design an effective hot zone for a controlled growth of Yb:S-FAP [Yb3+:Sr5(PO4)3F] laser crystal by the Czochralski technology and effective cooling that can reduce stress. Theoretical and numerical analyses are performed to study the causes of cracking, mitigate the major cracking, as well as reduce cooling time. In the current system, three locations in the crystal are prone to crack, such as the top shoulder of the crystal, the middle portion above the crucible edge, and the bottom tail portion. Based on numerical simulations, we propose a new hot zone design and cooling procedure to grow and cool large diameter crystal without cracking.
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NASA Astrophysics Data System (ADS)
Premasiri, Amaranath; Happawana, Gemunu; Rosen, Arye
2007-02-01
Photodynamic therapy (PDT) is an approved treatment modality for Barrett's and invasive esophageal carcinoma. Proper Combination of photosentizing agent, oxygen, and a specific wavelength of light to activate the photosentizing agents is necessary for the cytotoxic destruction of cancerous cells by PDT. As a light source expensive solid-state laser sources currently are being used for the treatment. Inexpensive semiconductor lasers have been suggested for the light delivery system, however packaging of semiconductor lasers for optimal optical power output is challenging. In this paper, we present a multidirectional direct water-cooling of semiconductor lasers that provides a better efficiency than the conventional unidirectional cooling. AlGaAsP lasers were tested under de-ionized (DI) water and it is shown that the optical power output of the lasers under the DI water is much higher than that of the uni-directional cooling of lasers. Also, in this paper we discuss how direct DI water-cooling can optimize power output of semiconductor lasers. Thereafter an optimal design of the semiconductor laser package is shown with the DI water-cooling system. Further, a microwave antenna is designed which is to be imprinted on to a balloon catheter in order to provide local heating of esophagus, leading to an increase in local oxygenation of the tumor to generate an effective level of singlet oxygen for cellular death. Finally the optimal level of light energy that is required to achieve the expected level of singlet oxygen is modeled to design an efficient PDT protocol.
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Modular package for cooling a laser diode array
Mundinger, David C.; Benett, William J.; Beach, Raymond J.
1992-01-01
A laser diode array is disclosed that includes a plurality of planar packages and active cooling. The laser diode array may be operated in a long duty cycle, or in continuous operation. A laser diode bar and a microchannel heat sink are thermally coupled in a compact, thin planar package having the laser diode bar located proximate to one edge. In an array, a number of such thin planar packages are secured together in a stacked configuration, in close proximity so that the laser diodes are spaced closely. The cooling means includes a microchannel heat sink that is attached proximate to the laser bar so that it absorbs heat generated by laser operation. To provide the coolant to the microchannels, each thin planar package comprises a thin inlet manifold and a thin outlet manifold connected to an inlet corridor and an outlet corridor. The inlet corridor comprises a hole extending through each of the packages in the array, and the outlet corridor comprises a hole extending through each of the packages in the array. The inlet and outlet corridors are connected to a conventional coolant circulation system. The laser diode array with active cooling has application as an optical pump for high power solid state lasers. Further, it can be incorporated in equipment such as communications devices and active sensors, and in military and space applications, and it can be useful in applications having space constraints and energy limitations.
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Rugged passively cooled high power laser fiber optic connectors and methods of use
DOE Office of Scientific and Technical Information (OSTI.GOV)
Rinzler, Charles C.; Gray, William C.; Fraze, Jason D.
2016-06-07
There are provided high power laser connectors and couplers and methods that are capable of providing high laser power without the need for active cooling to remote, harsh and difficult to access locations and under difficult and harsh conditions and to manage and mitigate the adverse effects of back reflections.
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Possibilities of application of the swirling flows in cooling systems of laser mirrors
NASA Astrophysics Data System (ADS)
Shanin, Yu; Chernykh, A.
2018-03-01
The paper presents analytical investigations into advanced cooling systems of the laser mirrors with heat exchange intensification by methods of ordered vortex impact on a coolant flow structure. Advantages and effectiveness of the proposed cooling systems have been estimated to reduction displacement of an optical mirror surface due to a flexure.
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NASA Astrophysics Data System (ADS)
Heinemann, S.; McDougall, S. D.; Ryu, G.; Zhao, L.; Liu, X.; Holy, C.; Jiang, C.-L.; Modak, P.; Xiong, Y.; Vethake, T.; Strohmaier, S. G.; Schmidt, B.; Zimer, H.
2018-02-01
The advance of high power semiconductor diode laser technology is driven by the rapidly growing industrial laser market, with such high power solid state laser systems requiring ever more reliable diode sources with higher brightness and efficiency at lower cost. In this paper we report simulation and experimental data demonstrating most recent progress in high brightness semiconductor laser bars for industrial applications. The advancements are in three principle areas: vertical laser chip epitaxy design, lateral laser chip current injection control, and chip cooling technology. With such improvements, we demonstrate disk laser pump laser bars with output power over 250W with 60% efficiency at the operating current. Ion implantation was investigated for improved current confinement. Initial lifetime tests show excellent reliability. For direct diode applications <1 um smile and >96% polarization are additional requirements. Double sided cooling deploying hard solder and optimized laser design enable single emitter performance also for high fill factor bars and allow further power scaling to more than 350W with 65% peak efficiency with less than 8 degrees slow axis divergence and high polarization.
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NASA Astrophysics Data System (ADS)
Steiger, J.; Beck, B. R.; Gruber, L.; Church, D. A.; Holder, J. P.; Schneider, D.
1999-01-01
Storage rings and Penning traps are being used to study ions in their highest charge states. Both devices must have the capability for ion cooling in order to perform high precision measurements such as mass spectrometry and laser spectroscopy. This is accomplished in storage rings in a merged beam arrangement where a cold electron beam moves at the speed of the ions. In RETRAP, a Penning trap located at Lawrence Livermore National Laboratory, a sympathetic laser/ion cooling scheme has been implemented. In a first step, singly charged beryllium ions are cooled electronically by a tuned circuit and optically by a laser. Then hot, highly charged ions are merged into the cold Be plasma. By collisions, their kinetic energy is reduced to the temperature of the Be plasma. First experiments indicate that the highly charged ions form a strongly coupled plasma with a Coulomb coupling parameter exceeding 1000.
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Design study of a laser-cooled infrared sensor
Hehlen, Markus Peter; Boncher, William Lawrence; Love, Steven Paul
2015-03-10
The performance of a solid-state optical refrigerator is the result of a complex interplay of numerous optical and thermal parameters. We present a first preliminary study of an optical cryocooler using ray-tracing techniques. A numerical optimization identified a non-resonant cavity with astigmatism. This geometry offered more efficient pump absorption by the YLF:10%Yb laser-cooling crystal compared to non-resonant cavities without astigmatism that have been pursued experimentally so far. Ray tracing simulations indicate that ~80% of the incident pump light can absorbed for temperatures down to ~100 K. Calculations of heat loads, cooling power, and net payload heat lift are presented. Theymore » show that it is possible to cool a payload to a range of 90–100 K while producing a net payload heat lift of 80 mW and 300 mW when pumping a YLF:10%Yb crystal with 20 W and 50 W at 1020 nm, respectively. This performance is suited to cool HgCdTe infrared detectors that are used for sensing in the 8–12 μm atmospheric window. While the detector noise would be ~6× greater at 100 K than at 77 K, the laser refrigerator would introduce no vibrations and thus eliminate sources of microphonic noise that are limiting the performance of current systems.« less
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Temperature measurements during laser skin welding
NASA Astrophysics Data System (ADS)
Fried, Nathaniel M.; Choi, Bernard; Welch, Ashley J.; Walsh, Joseph T., Jr.
1999-06-01
A thermal camera was used to measure surface temperatures during laser skin welding to provide feedback for optimization of the laser parameters. Two-cm-long, full- thickness incisions were made in guinea pig skin. India ink was used as an absorber. Continuous-wave, 1.06-μm, Nd:YAG laser radiation was scanned over the incisions, producing a pulse duration of approximately 100 ms. Cooling durations between scans of 1.6, 4.0, and 8.0 s were studied with total operation times of 3, 5, and 10 min, respectively. A laser spot diameter of 5 mm was used with the power constant at 10 W. Thermal images were obtained at 30 frames per second with a thermal camera detecting 3.5 micrometers radiation. Surface temperatures were recorded at 0, 1, and 6 mm from the center line of the incision. Cooling durations between scans of 1.6 s and 4.0 s in vitro resulted in temperatures at the weld site remaining above ~65°C for prolonged periods of time. Cooling durations between scans as long as 8.0 s were sufficient both in vitro and in vivo to prevent a significant rise in baseline temperatures at the weld site over time.
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Photochemical isotope separation
Robinson, C. Paul; Jensen, Reed J.; Cotter, Theodore P.; Greiner, Norman R.; Boyer, Keith
1987-01-01
A process for separating isotopes by selective excitation of isotopic species of a volatile compound by tuned laser light. A highly cooled gas of the volatile compound is produced in which the isotopic shift is sharpened and defined. Before substantial condensation occurs, the cooled gas is irradiated with laser light precisely tuned to a desired wavelength to selectively excite a particular isotopic species in the cooled gas. The laser light may impart sufficient energy to the excited species to cause it to undergo photochemical reaction or even to photoionize. Alternatively, a two-photon irradiation may be applied to the cooled gas to induce photochemical reaction or photoionization. The process is particularly applicable to the separation of isotopes of uranium and plutonium.
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Laser-induced rotation and cooling of a trapped microgyroscope in vacuum
Arita, Yoshihiko; Mazilu, Michael; Dholakia, Kishan
2013-01-01
Quantum state preparation of mesoscopic objects is a powerful playground for the elucidation of many physical principles. The field of cavity optomechanics aims to create these states through laser cooling and by minimizing state decoherence. Here we demonstrate simultaneous optical trapping and rotation of a birefringent microparticle in vacuum using a circularly polarized trapping laser beam—a microgyroscope. We show stable rotation rates up to 5 MHz. Coupling between the rotational and translational degrees of freedom of the trapped microgyroscope leads to the observation of positional stabilization in effect cooling the particle to 40 K. We attribute this cooling to the interaction between the gyroscopic directional stabilization and the optical trapping field. PMID:23982323
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Narrow-line laser cooling by adiabatic transfer
NASA Astrophysics Data System (ADS)
Norcia, Matthew A.; Cline, Julia R. K.; Bartolotta, John P.; Holland, Murray J.; Thompson, James K.
2018-02-01
We propose and demonstrate a novel laser cooling mechanism applicable to particles with narrow-linewidth optical transitions. By sweeping the frequency of counter-propagating laser beams in a sawtooth manner, we cause adiabatic transfer back and forth between the ground state and a long-lived optically excited state. The time-ordering of these adiabatic transfers is determined by Doppler shifts, which ensures that the associated photon recoils are in the opposite direction to the particle’s motion. This ultimately leads to a robust cooling mechanism capable of exerting large forces via a weak transition and with reduced reliance on spontaneous emission. We present a simple intuitive model for the resulting frictional force, and directly demonstrate its efficacy for increasing the total phase-space density of an atomic ensemble. We rely on both simulation and experimental studies using the 7.5 kHz linewidth 1S0 to 3P1 transition in 88Sr. The reduced reliance on spontaneous emission may allow this adiabatic sweep method to be a useful tool for cooling particles that lack closed cycling transitions, such as molecules.
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Laser cooling of 85Rb atoms to the recoil-temperature limit
NASA Astrophysics Data System (ADS)
Huang, Chang; Kuan, Pei-Chen; Lan, Shau-Yu
2018-02-01
We demonstrate the laser cooling of 85Rb atoms in a two-dimensional optical lattice. We follow the two-step degenerate Raman sideband cooling scheme [Kerman et al., Phys. Rev. Lett. 84, 439 (2000), 10.1103/PhysRevLett.84.439], where a fast cooling of atoms to an auxiliary state is followed by a slow cooling to a dark state. This method has the advantage of independent control of the heating rate and cooling rate from the optical pumping beam. We operate the lattice at a Lamb-Dicke parameter η =0.45 and show the cooling of spin-polarized 85Rb atoms to the recoil temperature in both dimensions within 2.4 ms with the aid of adiabatic cooling.
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Scaling studies of solar pumped lasers
NASA Astrophysics Data System (ADS)
Christiansen, W. H.; Chang, J.
1985-08-01
A progress report of scaling studies of solar pumped lasers is presented. Conversion of blackbody radiation into laser light has been demonstrated in this study. Parametric studies of the variation of laser mixture composition and laser gas temperature were carried out for CO2 and N2O gases. Theoretical analysis and modeling of the system have been performed. Reasonable agreement between predictions in the parameter variation and the experimental results have been obtained. Almost 200 mW of laser output at 10.6 micron was achieved by placing a small sapphire laser tube inside an oven at 1500 K the tube was filled with CO2 laser gas mixture and cooled by longitudinal nitrogen gas flow.
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Scaling studies of solar pumped lasers
NASA Technical Reports Server (NTRS)
Christiansen, W. H.; Chang, J.
1985-01-01
A progress report of scaling studies of solar pumped lasers is presented. Conversion of blackbody radiation into laser light has been demonstrated in this study. Parametric studies of the variation of laser mixture composition and laser gas temperature were carried out for CO2 and N2O gases. Theoretical analysis and modeling of the system have been performed. Reasonable agreement between predictions in the parameter variation and the experimental results have been obtained. Almost 200 mW of laser output at 10.6 micron was achieved by placing a small sapphire laser tube inside an oven at 1500 K the tube was filled with CO2 laser gas mixture and cooled by longitudinal nitrogen gas flow.
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IR multiphoton absorption of SF6 in flow with Ar at moderate energy fluences
NASA Astrophysics Data System (ADS)
Makarov, G. N.; Ronander, E.; van Heerden, S. P.; Gouws, M.; van der Merwe, K.
1997-10-01
IR multiple photon absorption (MPA) of SF6 in flow with Ar (SF6: Ar=1:100) in conditions of a large vibrational/rotational temperature difference (TV𪒮 K, TR䏐 K) was studied at moderate energy fluences from ۂ.1 to 𪐬 mJ/cm2, which are of interest for isotope selective two-step dissociation of molecules. A 50 cm Laval-type slit nozzle for the flow cooling, and a TEA CO2-laser for excitation of molecules were used in the experiments. The laser energy fluence dependences of the SF6 MPA were studied for several CO2-laser lines which are in a good resonance with the linear absorption spectrum of the Ƚ vibration of SF6 at low temperature. The effect of the laser pulse duration (intensity) on MPA of flow cooled SF6 with Ar was also studied. The results are compared with those obtained in earlier studies.
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Fast optical cooling of a nanomechanical cantilever by a dynamical Stark-shift gate.
Yan, Leilei; Zhang, Jian-Qi; Zhang, Shuo; Feng, Mang
2015-10-12
The efficient cooling of nanomechanical resonators is essential to exploration of quantum properties of the macroscopic or mesoscopic systems. We propose such a laser-cooling scheme for a nanomechanical cantilever, which works even for the low-frequency mechanical mode and under weak cooling lasers. The cantilever is coupled by a diamond nitrogen-vacancy center under a strong magnetic field gradient and the cooling is assisted by a dynamical Stark-shift gate. Our scheme can effectively enhance the desired cooling efficiency by avoiding the off-resonant and undesired carrier transitions, and thereby cool the cantilever down to the vicinity of the vibrational ground state in a fast fashion.
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Fast optical cooling of a nanomechanical cantilever by a dynamical Stark-shift gate
Yan, Leilei; Zhang, Jian-Qi; Zhang, Shuo; Feng, Mang
2015-01-01
The efficient cooling of nanomechanical resonators is essential to exploration of quantum properties of the macroscopic or mesoscopic systems. We propose such a laser-cooling scheme for a nanomechanical cantilever, which works even for the low-frequency mechanical mode and under weak cooling lasers. The cantilever is coupled by a diamond nitrogen-vacancy center under a strong magnetic field gradient and the cooling is assisted by a dynamical Stark-shift gate. Our scheme can effectively enhance the desired cooling efficiency by avoiding the off-resonant and undesired carrier transitions, and thereby cool the cantilever down to the vicinity of the vibrational ground state in a fast fashion. PMID:26455901
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Astigmatic Herriott cell for optical refrigeration
NASA Astrophysics Data System (ADS)
Gragossian, Aram; Meng, Junwei; Ghasemkhani, Mohammadreza; Albrecht, Alexander R.; Sheik-Bahae, Mansoor
2017-01-01
Cooling rare-earth-doped crystals to the lowest temperature possible requires enhanced resonant absorption and high-purity crystals. Since resonant absorption decreases as the crystal is cooled, the only path forward is to increase the number of roundtrips that the laser makes inside the crystal. To achieve even lower temperatures than previously reported, we have employed an astigmatic Herriott cell to improve laser absorption at low temperatures. Preliminary results indicate improvement over previous designs. This cavity potentially enables us to use unpolarized high-power fiber lasers, and to achieve much higher cooling power for practical applications.
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Laser cooling and imaging of individual radioactive +90Sr ions
NASA Astrophysics Data System (ADS)
Jung, Kyunghun; Iwata, Yoshihiro; Miyabe, Masabumi; Yamamoto, Kazuhiro; Yonezu, Tomohisa; Wakaida, Ikuo; Hasegawa, Shuichi
2017-10-01
We have developed an apparatus integrating resonance-ionization, ion-trap, and laser-cooling techniques for an ultratrace radioactive isotope 90Sr analysis. Trapped +90Sr isotope ions were laser cooled, and their 4 d 3/2 2D →5 p 1/2 2P transition isotope shift was experimentally measured to be -281 (17 ) MHz by comparing individual spectra of +88Sr and +90Sr ions. Crystallization of +90Sr was carried out using the resonance frequency value confirmed in our experiment, and then +90Sr individual ions were successfully observed.
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Compact conductively cooled electro-optical Q-switched Nd:YAG laser
NASA Astrophysics Data System (ADS)
Li, Chaoyang; Lu, Chengqiang; Li, Chuan; Zang, Yannan; Yang, Zhen; Han, Song; Li, Ye; Yang, Ning; Shi, Junfeng; Zhou, Zewu
2017-11-01
We report on a compact conductively cooled high-repetition-rate nanosecond Nd:YAG laser. The oscillator was an laser diode side-pumped electro-optical (EO) Q-switched Nd:YAG rod laser adopting unstable cavity with a variable reflectivity mirror. A pulse train of 142 mJ with duration of 10 ns, repetition rate of 80 Hz at 1064 nm has been achieved. Maximum pulse energy was obtained at the pump energy of 1380 mJ, corresponding to the optical-optical conversion efficiency of 10.3%. The peak power was deduced to be 14.2 MW. The near-field pattern demonstrated a nearly super Gaussian flat top profile. To our knowledge, this is the highest repetition rate operation for a conductively cooled EO Q-switched Nd:YAG rod laser.
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Cryogenic cooling for high power laser amplifiers
NASA Astrophysics Data System (ADS)
Perin, J. P.; Millet, F.; Divoky, M.; Rus, B.
2013-11-01
Using DPSSL (Diode Pumped Solid State Lasers) as pumping technology, PW-class lasers with enhanced repetition rates are developed. Each of the Yb YAG amplifiers will be diode-pumped at a wavelength of 940 nm. This is a prerequisite for achieving high repetition rates (light amplification duration 1 millisecond and repetition rate 10 Hz). The efficiency of DPSSL is inversely proportional to the temperature, for this reason the slab amplifier have to be cooled at a temperature in the range of 100 K-170 K with a heat flux of 1 MW*m-2. This paper describes the thermo-mechanical analysis for the design of the amplification laser head, presents a preliminary proposal for the required cryogenic cooling system and finally outlines the gain of cryogenic operation for the efficiency of high pulsed laser.
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Kilmer, Suzanne L
2017-01-01
Cryolipolysis is a safe, effective non-surgical procedure to reduce fat. For most cryolipolysis treatments, tissue is pulled between parallel cooling plates with a treatment duration of 60 minutes. A novel contoured cup, medium-sized applicator was developed to increase tissue contact with reduced skin tension and reduced treatment time. This prototype contoured cup was investigated with a standard cryolipolysis applicator to evaluate safety, efficacy, and patient preference. A prototype CoolCup medium-sized vacuum applicator (CoolSculpting System, ZELTIQ Aesthetics) was used to treat n = 19 subjects in the flanks. Randomly assigned, one flank received standard treatment with the CoolCore applicator (-10°C for 60 minutes). The contralateral flank received treatment from the CoolCup (-11°C for 35 minutes). The clinical study primary efficacy endpoint was 70% correct identification of baseline photographs by independent physician review. Incidence of adverse device effects was monitored. Fat layer reduction was measured by ultrasound and subject surveys were administered 12 weeks post-treatment. Equivalent efficacy was demonstrated between the CoolCore standard treatment and the prototype CoolCup. Independent review from three blinded physicians found 81% correct identification of baseline photographs for the standard treatment and 79% for the CoolCup. Ultrasound measurements indicated mean fat layer reduction of 4.38 mm for the standard treatment and 4.40 mm for the CoolCup; no statistically significant difference was found when comparing treatment efficacy of the two applicators (P = 0.96). Patient questionnaires revealed 85% preferred CoolCup because of shorter treatment duration and greater comfort. Procedural assessments revealed 45% lower pain scores for CoolCup. Immediate post-treatment clinical assessments revealed 82% less bruising. Typical side effects, such as numbness and erythema, were similar. There were no adverse events. This clinical study of a prototype medium-sized vacuum applicator with a cooled contoured surface indicates that the CoolCup produces equivalent safety and efficacy to the standard CoolCore cryolipolysis applicator. With a 42% reduction in treatment time, the procedure was found to be more comfortable because of lower vacuum skin tension and shorter treatment duration. Lasers Surg. Med. 49:63-68, 2017. © 2016 The Authors. Lasers in Surgery and Medicine Published by Wiley Periodicals, Inc. © 2016 The Authors. Lasers in Surgery and Medicine Published by Wiley Periodicals, Inc.
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High energy bursts from a solid state laser operated in the heat capacity limited regime
Albrecht, G.; George, E.V.; Krupke, W.F.; Sooy, W.; Sutton, S.B.
1996-06-11
High energy bursts are produced from a solid state laser operated in a heat capacity limited regime. Instead of cooling the laser, the active medium is thermally well isolated. As a result, the active medium will heat up until it reaches some maximum acceptable temperature. The waste heat is stored in the active medium itself. Therefore, the amount of energy the laser can put out during operation is proportional to its mass, the heat capacity of the active medium, and the temperature difference over which it is being operated. The high energy burst capacity of a heat capacity operated solid state laser, together with the absence of a heavy, power consuming steady state cooling system for the active medium, will make a variety of applications possible. Alternately, cooling takes place during a separate sequence when the laser is not operating. Industrial applications include new material working processes. 5 figs.
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High energy bursts from a solid state laser operated in the heat capacity limited regime
Albrecht, Georg; George, E. Victor; Krupke, William F.; Sooy, Walter; Sutton, Steven B.
1996-01-01
High energy bursts are produced from a solid state laser operated in a heat capacity limited regime. Instead of cooling the laser, the active medium is thermally well isolated. As a result, the active medium will heat up until it reaches some maximum acceptable temperature. The waste heat is stored in the active medium itself. Therefore, the amount of energy the laser can put out during operation is proportional to its mass, the heat capacity of the active medium, and the temperature difference over which it is being operated. The high energy burst capacity of a heat capacity operated solid state laser, together with the absence of a heavy, power consuming steady state cooling system for the active medium, will make a variety of applications possible. Alternately, cooling takes place during a separate sequence when the laser is not operating. Industrial applications include new material working processes.
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Subsurface wrinkle removal by laser treatment in combination with dynamic cooling
NASA Astrophysics Data System (ADS)
Paithankar, Dilip Y.; Hsia, James C.; Ross, E. V.
2000-05-01
Compared to traditional CO2 or Er:YAG laser resurfacing, sub-surface thermal injury to stimulate skin remodeling for the removal of wrinkles is attractive due to the lower morbidity associated with epidermal preservation. We have developed a technique that thermally damages dermal collagen while preserving the epidermis by a combination of infra-red laser irradiation and dynamic cooling of skin. Wound healing response to the thermal denaturation of collagen may trigger synthesis of fresh collagen and result in restoration of a more youthful appearance. The laser wavelength is chosen so as to thermally injure dermis in a narrow band at depths of 150 to 500 microns from the surface of the skin. The epidermis is preserved by a Candela dynamic cooling device (DCDTM) cryogen spray. Three-dimensional Monte Carlo calculations have been done to calculate the light distribution within tissue while taking into account light absorption and scattering. This light distribution has been used to calculate heat generation within tissue. Heat transfer calculations have been done while taking into consideration the cryogen cooling. The resulting temperature profiles have been used to suggest heating and cooling parameters. Freshly excised ex vivo pig skin was irradiated with laser and DCD at these heating and cooling parameters. Histological evaluation of the biopsies has shown that it is possible to spare the epidermis while thermally denaturing the dermal collagen. The modeling and histology results are discussed.
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NASA Astrophysics Data System (ADS)
Yudkin, Yaakov; Khaykovich, Lev
2018-05-01
We show experimentally that three-dimensional laser cooling of lithium atoms on the D2 line is possible when the laser light is tuned exactly to resonance with the dominant atomic transition. Qualitatively, it can be understood by applying simple Doppler cooling arguments to the specific hyperfine structure of the excited state of lithium atoms, which is both dense and inverted. However, to build a quantitative theory, we must resolve to a full model which takes into account both the entire atomic structure of all 24 Zeeman sublevels and the laser light polarization. Moreover, by means of Monte Carlo simulations, we show that coherent processes play an important role in showing consistency between the theory and the experimental results.
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Toward laser cooling and trapping lanthanum ions
NASA Astrophysics Data System (ADS)
Olmschenk, Steven; Banner, Patrick; Hankes, Jessie; Nelson, Amanda
2017-04-01
Trapped atomic ions are a leading candidate for applications in quantum information. For scalability and applications in quantum communication, it would be advantageous to interface ions with telecom light. We present progress toward laser cooling doubly-ionized lanthanum, which should require only infrared, telecom-compatible light. Since the hyperfine structure of this ion has not been measured, we are using optogalavanic spectroscopy in a hollow cathode lamp to measure the hyperfine spectrum of transitions in lanthanum. Using laser ablation to directly produce ions from a solid target, we laser cool and trap barium ions, and explore extending this technique to lanthanum ions. This research is supported by the Army Research Office, Research Corporation for Science Advancement, and Denison University.
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Zhuang, W Z; Chen, Yi-Fan; Su, K W; Huang, K F; Chen, Y F
2012-09-24
We experimentally confirm that diamond surface cooling can significantly enhance the output performance of a sub-nanosecond diode-end-pumped passively Q-switched Yb:YAG laser. It is found that the pulse energy obtained with diamond cooling is approximately 1.5 times greater than that obtained without diamond cooling, where a Cr(4+):YAG absorber with the initial transmission of 84% is employed. Furthermore, the standard deviation of the pulse amplitude peak-to-peak fluctuation is found to be approximately 3 times lower than that measured without diamond cooling. Under a pump power of 3.9 W, the passively Q-switched Yb:YAG laser can generate a pulse train of 3.3 kHz repetition rate with a pulse energy of 287 μJ and with a pulse width of 650 ps.
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Thin planar package for cooling an array of edge-emitting laser diodes
Mundinger, David C.; Benett, William J.
1992-01-01
A laser diode array is disclosed that includes a plurality of planar assemblies and active cooling of each assembly. The laser diode array may be operated in a long duty cycle, or in continuous operation. A laser diode bar and a microchannel heat sink are thermally coupled in a compact, thin planar assembly having the laser diode bar located proximate to one edge. In an array, a number of such thin planar assemblies are secured together in a stacked configuration, in close proximity so that the laser diodes are spaced closely. The cooling means includes a microchannel heat sink proximate to the laser diode bar to absorb heat generated by laser operation. To provide the coolant to the microchannels, each thin planar assembly comprises passageways that connect the microchannels to inlet and outlet corridors. Each inlet passageway may comprise a narrow slot that directs coolant into the microchannels and increases the velocity of flow therethrough. The corridors comprises holes extending through each of the assemblies in the array. The inlet and outlet corridors are connected to a conventional coolant circulation system. The laser diode array with active cooling has applications as an optical pump for high power solid state lasers, or by mating the diodes with fiber optic lenses. Further, the arrays can be useful in applications having space constraints and energy limitations, and in military and space applications. The arrays can be incorporated in equipment such as communications devices and active sensors.
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Synthesis and evaluation of ultra-pure rare-earth-coped glass for laser refrigeration
DOE Office of Scientific and Technical Information (OSTI.GOV)
Patterson, Wendy M; Hehlen, Markus P; Epstein, Richard I
2009-01-01
Significant progress has been made in synthesizing and characterizing ultra-pure, rare-earth doped ZIBLAN (ZrF{sub 4}-InF{sub 3}BaF{sub 2}-LaF{sub 3}-AlF{sub 3}-NaF) glass capable of laser refrigeration. The glass was produced from fluorides which were purified and subsequently treated with hydrofluoric gas at elevated temperatures to remove impurities before glass formation. Several Yb3 +-doped samples were studied with degrees of purity and composition with successive iterations producing an improved material. We have developed a non-invasive, spectroscopic technique, two band differential luminescence thermometry (TBDLT), to evaluate the intrinsic quality of the ytterbium doped ZIBLAN used for laser cooling experiments. TBDLT measures local temperature changesmore » within an illuminated volume resulting solely from changes in the relative thermal population of the excited state levels. This TBDLT technique utilizes two commercially available band pass filters to select and integrate the 'difference regions' of interest in the luminescence spectra. The goal is to determine the minimum temperature to which the ytterbium sample can cool on the local scale, unphased by surface heating. This temperature where heating and cooling are exactly balanced is the zero crossing temperature (ZCT) and can be used as a measure for the presence of impurities and the overall quality of the laser cooling material. Overall, favorable results were obtained from 1 % Yb3+-doped glass, indicating our glasses are desirable for laser refrigeration.« less
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Quantitative theoretical analysis of lifetimes and decay rates relevant in laser cooling BaH
NASA Astrophysics Data System (ADS)
Moore, Keith; Lane, Ian C.
2018-05-01
Tiny radiative losses below the 0.1% level can prove ruinous to the effective laser cooling of a molecule. In this paper the laser cooling of a hydride is studied with rovibronic detail using ab initio quantum chemistry in order to document the decays to all possible electronic states (not just the vibrational branching within a single electronic transition) and to identify the most populated final quantum states. The effect of spin-orbit and associated couplings on the properties of the lowest excited states of BaH are analysed in detail. The lifetimes of the A2Π1/2, H2Δ3/2 and E2Π1/2 states are calculated (136 ns, 5.8 μs and 46 ns respectively) for the first time, while the theoretical value for B2 Σ1/2+ is in good agreement with experiments. Using a simple rate model the numbers of absorption-emission cycles possible for both one- and two-colour cooling on the competing electronic transitions are determined, and it is clearly demonstrated that the A2Π - X2Σ+ transition is superior to B2Σ+ - X2Σ+ , where multiple tiny decay channels degrade its efficiency. Further possible improvements to the cooling method are proposed.
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Photochemical isotope separation
Robinson, C.P.; Jensen, R.J.; Cotter, T.P.; Greiner, N.R.; Boyer, K.
1987-04-28
A process is described for separating isotopes by selective excitation of isotopic species of a volatile compound by tuned laser light. A highly cooled gas of the volatile compound is produced in which the isotopic shift is sharpened and defined. Before substantial condensation occurs, the cooled gas is irradiated with laser light precisely tuned to a desired wavelength to selectively excite a particular isotopic species in the cooled gas. The laser light may impart sufficient energy to the excited species to cause it to undergo photochemical reaction or even to photoionize. Alternatively, a two-photon irradiation may be applied to the cooled gas to induce photochemical reaction or photoionization. The process is particularly applicable to the separation of isotopes of uranium and plutonium. 8 figs.
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NASA Technical Reports Server (NTRS)
Shoji, J. M.; Larson, V. R.
1976-01-01
The application of advanced liquid-bipropellant rocket engine analysis techniques has been utilized for prediction of the potential delivered performance and the design of thruster wall cooling schemes for laser-heated rocket thrusters. Delivered specific impulse values greater than 1000 lbf-sec/lbm are potentially achievable based on calculations for thrusters designed for 10-kW and 5000-kW laser beam power levels. A thruster wall-cooling technique utilizing a combination of regenerative cooling and a carbon-seeded hydrogen boundary layer is presented. The flowing carbon-seeded hydrogen boundary layer provides radiation absorption of the heat radiated from the high-temperature plasma. Also described is a forced convection thruster wall cooling design for an experimental test thruster.
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Λ-enhanced grey molasses on the D2 transition of Rubidium-87 atoms.
Rosi, Sara; Burchianti, Alessia; Conclave, Stefano; Naik, Devang S; Roati, Giacomo; Fort, Chiara; Minardi, Francesco
2018-01-22
Laser cooling based on dark states, i.e. states decoupled from light, has proven to be effective to increase the phase-space density of cold trapped atoms. Dark-states cooling requires open atomic transitions, in contrast to the ordinary laser cooling used for example in magneto-optical traps (MOTs), which operate on closed atomic transitions. For alkali atoms, dark-states cooling is therefore commonly operated on the D 1 transition nS 1/2 → nP 1/2 . We show that, for 87 Rb, thanks to the large hyperfine structure separations the use of this transition is not strictly necessary and that "quasi-dark state" cooling is efficient also on the D 2 line, 5S 1/2 → 5P 3/2 . We report temperatures as low as (4.0 ± 0.3) μK and an increase of almost an order of magnitude in the phase space density with respect to ordinary laser sub-Doppler cooling.
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Laser Cooled YbF Molecules for Measuring the Electron's Electric Dipole Moment
NASA Astrophysics Data System (ADS)
Lim, J.; Almond, J. R.; Trigatzis, M. A.; Devlin, J. A.; Fitch, N. J.; Sauer, B. E.; Tarbutt, M. R.; Hinds, E. A.
2018-03-01
We demonstrate one-dimensional sub-Doppler laser cooling of a beam of YbF molecules to 100 μ K . This is a key step towards a measurement of the electron's electric dipole moment using ultracold molecules. We compare the effectiveness of magnetically assisted and polarization-gradient sub-Doppler cooling mechanisms. We model the experiment and find good agreement with our data.
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Laser Cooled YbF Molecules for Measuring the Electron's Electric Dipole Moment.
Lim, J; Almond, J R; Trigatzis, M A; Devlin, J A; Fitch, N J; Sauer, B E; Tarbutt, M R; Hinds, E A
2018-03-23
We demonstrate one-dimensional sub-Doppler laser cooling of a beam of YbF molecules to 100 μK. This is a key step towards a measurement of the electron's electric dipole moment using ultracold molecules. We compare the effectiveness of magnetically assisted and polarization-gradient sub-Doppler cooling mechanisms. We model the experiment and find good agreement with our data.
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A Novel Gravito-Optical Surface Trap for Neutral Atoms
NASA Astrophysics Data System (ADS)
Xie, Chun-Xia; Wang, Zhengling; Yin, Jian-Ping
2006-04-01
We propose a novel gravito-optical surface trap (GOST) for neutral atoms based on one-dimensional intensity gradient cooling. The surface optical trap is composed of a blue-detuned reduced semi-Gaussian laser beam (SGB), a far-blue-detuned dark hollow beam and the gravity field. The SGB is produced by the diffraction of a collimated Gaussian laser beam passing through the straight edge of a semi-infinite opaque plate and then is reduced by an imaging lens. We calculate the intensity distribution of the reduced SGB, and study the dynamic process of the SGB intensity-gradient induced Sisyphus cooling for 87Rb atoms by using Monte Carlo simulations. Our study shows that the proposed GOST can be used not only to trap cold atoms loaded from a standard magneto-optical trap, but also to cool the trapped atoms to an equilibrium temperature of 3.47 μK from ~120 μK, even to realize an all-optical two-dimensional Bose-Einstein condensation by using optical-potential evaporative cooling.
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Advancements in high-power diode laser stacks for defense applications
NASA Astrophysics Data System (ADS)
Pandey, Rajiv; Merchen, David; Stapleton, Dean; Patterson, Steve; Kissel, Heiko; Fassbender, Wilhlem; Biesenbach, Jens
2012-06-01
This paper reports on the latest advancements in vertical high-power diode laser stacks using micro-channel coolers, which deliver the most compact footprint, power scalability and highest power/bar of any diode laser package. We present electro-optical (E-O) data on water-cooled stacks with wavelengths ranging from 7xx nm to 9xx nm and power levels of up to 5.8kW, delivered @ 200W/bar, CW mode, and a power-conversion efficiency of >60%, with both-axis collimation on a bar-to-bar pitch of 1.78mm. Also, presented is E-O data on a compact, conductively cooled, hardsoldered, stack package based on conventional CuW and AlN materials, with bar-to-bar pitch of 1.8mm, delivering average power/bar >15W operating up to 25% duty cycle, 10ms pulses @ 45C. The water-cooled stacks can be used as pump-sources for diode-pumped alkali lasers (DPALs) or for more traditional diode-pumped solid-state lasers (DPSSL). which are power/brightness scaled for directed energy weapons applications and the conductively-cooled stacks as illuminators.
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Cervicofacial subcutaneous emphysema associated with dental laser treatment.
Mitsunaga, S; Iwai, T; Kitajima, H; Yajima, Y; Ohya, T; Hirota, M; Mitsudo, K; Aoki, N; Yamashita, Y; Omura, S; Tohnai, I
2013-12-01
Cervicofacial subcutaneous emphysema is a rare complication of dental procedures. Although most cases of emphysema occur incidentally with the use of a high-speed air turbine handpiece, there have been some reports over the past decade of cases caused by dental laser treatment. Emphysema as a complication caused by the air cooling spray of a dental laser is not well known, even though dental lasers utilize compressed air just as air turbines and syringes do. In this study, we comprehensively reviewed cases of emphysema attributed to dental laser treatment that appeared in the literature between January 2001 and September 2012, and we included three such cases referred to us. Among 13 cases identified in total, nine had cervicofacial subcutaneous and mediastinal emphysema. Compared with past reviews, the incidence of mediastinal emphysema caused by dental laser treatment was higher than emphysema caused by dental procedure without dental laser use. Eight patients underwent CO2 laser treatment and two underwent Er:YAG laser treatment. Nine patients had emphysema following laser irradiation for soft tissue incision. Dentists and oral surgeons should be cognizant of the potential risk for iatrogenic emphysema caused by the air cooling spray during dental laser treatment and ensure proper usage of lasers. © 2013 Australian Dental Association.
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Q-switched slab RF discharge CO laser
NASA Astrophysics Data System (ADS)
Ionin, A. A.; Kochetkov, Yu V.; Kozlov, A. Yu; Mokrousova, D. V.; Seleznev, L. V.; Sinitsyn, D. V.; Sunchugasheva, E. S.; Zemtsov, D. S.
2017-05-01
A compact repetitively pulsed cryogenically cooled slab RF discharge CO laser with double path V-type laser resonator equipped with external Q-switching system based on rotating mirror was developed and studied. The laser produced mid-IR (λ ~ 5-7 µm) radiation pulses of ~1 ÷ 2 µs duration (FWHM), peak power up to ~3 kW, and pulse repetition rate up to 130 Hz. Averaged output laser power reached 0.5 W, the laser spectrum consisted of ~80 laser lines with individual peak power up to 80 W.
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Laser ignition application in a space experiment
NASA Technical Reports Server (NTRS)
Liou, Larry C.; Culley, Dennis E.
1993-01-01
A laser ignition system is proposed for the Combustion Experiment Module on an orbiting spacecraft. The results of a design study are given using the scheduled 'Flame Ball Experiment' as the design guidelines. Three laser ignition mechanisms and wavelengths are evaluated. A prototype laser is chosen and its specifications are given, followed by consideration of the beam optical arrangement, the ignition power requirement, the laser ignition system weight, size, reliability, and laser cooling and power consumption. Electromagnetic interference to the onboard electronics caused by the laser ignition process is discussed. Finally, ground tests are suggested.
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On the possibility of laser cooling of Cr3+ ions doped crystals
NASA Astrophysics Data System (ADS)
Feofilov, S. P.; Kulinkin, A. B.
2018-01-01
The fluorescence of Cr3+ ions doped insulating crystals was studied under the excitation in the long-wavelength tail of the absorption spectrum ("laser cooling regime"). The 4T2 - 4A2 and 2E - 4A2 fluorescence spectra with a dominant anti-Stokes component were observed. Though no optical refrigeration was detected in the presented experiments, the spectroscopic results suggest that electron-phonon bands of Cr3+ ions are of interest for further investigations from the point of view of achieving optical refrigeration.
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Subsurface thermal coagulation of tissues using near infrared lasers
NASA Astrophysics Data System (ADS)
Chang, Chun-Hung Jack
Noninvasive laser therapy is currently limited primarily to cosmetic dermatological applications such as skin resurfacing, hair removal, tattoo removal and treatment of vascular birthmarks. In order to expand applications of noninvasive laser therapy, deeper optical penetration of laser radiation in tissue as well as more aggressive cooling of the tissue surface is necessary. The near-infrared laser wavelength of 1075 nm was found to be the optimal laser wavelength for creation of deep subsurface thermal lesions in liver tissue, ex vivo, with contact cooling, preserving a surface tissue layer of 2 mm. Monte Carlo light transport, heat transfer, and Arrhenius integral thermal damage simulations were conducted at this wavelength, showing good agreement between experiment and simulations. Building on the initial results, our goal is to develop new noninvasive laser therapies for application in urology, specifically for treatment of female stress urinary incontinence (SUI). Various laser balloon probes including side-firing and diffusing fibers were designed and tested for both transvaginal and transurethral approaches to treatment. The transvaginal approach showed the highest feasibility. To further increase optical penetration depth, various types and concentrations of optical clearing agents were also explored. Three cadavers studies were performed to investigate and demonstrate the feasibility of laser treatment for SUI.
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Local Laser Cooling of Yb:YLF to 110 K
2011-09-01
R. I . Epstein, “Optical refrigeration,” Nat. Photonics 1(12), 693–699 (2007). 3. M. Sheik- Bahae and R. I . Epstein, “Laser cooling of solids,” Laser...15. W. M. Patterson, M. Sheik- Bahae , R. I . Epstein, and M. P. Hehlen, “Model of laser-induced temperature changes in solid-state optical...179 (2001). 19. M. P. Hasselbeck, M. Sheik- Bahae , and R. I . Epstein, “Effect of high carrier density on luminescence thermometry in semiconductors
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Technology development for laser-cooled clocks on the International Space Station
NASA Technical Reports Server (NTRS)
Klipstein, W. M.
2003-01-01
The PARCS experiment will use a laser-cooled cesium atomic clock operating in the microgravity environment aboard the International Space Station to provide both advanced tests of gravitational theory to demonstrate a new cold-atom clock technology for space.
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Cankar, Ksenija; Music, Mark; Finderle, Zare
2016-11-01
It is generally known that differences exist between males and females with regard to sensitivity to cold. Similar differences even among females in different hormonal balance might influence microvascular response during cold provocation testing. The aim of the present study was to measure sex hormone levels, cold and cold pain perception thresholds and compare them to cutaneous laser-Doppler flux response during local cooling in both the follicular and luteal phases of the menstrual cycle. In the luteal phase a more pronounced decrease in laser-Doppler flux was observed compared to follicular phase during local cooling at 15°C (significant difference by Dunnett's test, p<0.05). In addition, statistically significant correlations between progesterone level and laser-Doppler flux response to local cooling were observed during the follicular (R=-0.552, p=0.0174) and during the luteal phases (R=0.520, p=0.0271). In contrast, the correlation between estradiol level and laser-Doppler flux response was observed only in the follicular phase (R=-0.506, p=0.0324). Our results show that individual sensitivity to cold influences cutaneous microvascular response to local cooling; that microvascular reactivity is more pronounced during the luteal phase of the menstrual cycle; and that reactivity correlates with hormone levels. The effect of specific sex hormone levels is related to the cold-provocation temperature. Copyright © 2016. Published by Elsevier Inc.
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Laser diode package with enhanced cooling
Deri, Robert J [Pleasanton, CA; Kotovsky, Jack [Oakland, CA; Spadaccini, Christopher M [Oakland, CA
2011-09-13
A laser diode package assembly includes a reservoir filled with a fusible metal in close proximity to a laser diode. The fusible metal absorbs heat from the laser diode and undergoes a phase change from solid to liquid during the operation of the laser. The metal absorbs heat during the phase transition. Once the laser diode is turned off, the liquid metal cools off and resolidifies. The reservoir is designed such that that the liquid metal does not leave the reservoir even when in liquid state. The laser diode assembly further includes a lid with one or more fin structures that extend into the reservoir and are in contact with the metal in the reservoir.
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Laser diode package with enhanced cooling
Deri, Robert J [Pleasanton, CA; Kotovsky, Jack [Oakland, CA; Spadaccini, Christopher M [Oakland, CA
2012-06-12
A laser diode package assembly includes a reservoir filled with a fusible metal in close proximity to a laser diode. The fusible metal absorbs heat from the laser diode and undergoes a phase change from solid to liquid during the operation of the laser. The metal absorbs heat during the phase transition. Once the laser diode is turned off, the liquid metal cools off and resolidifies. The reservoir is designed such that that the liquid metal does not leave the reservoir even when in liquid state. The laser diode assembly further includes a lid with one or more fin structures that extend into the reservoir and are in contact with the metal in the reservoir.
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Laser diode package with enhanced cooling
Deri, Robert J; Kotovsky, Jack; Spadaccini, Christopher M
2012-06-26
A laser diode package assembly includes a reservoir filled with a fusible metal in close proximity to a laser diode. The fusible metal absorbs heat from the laser diode and undergoes a phase change from solid to liquid during the operation of the laser. The metal absorbs heat during the phase transition. Once the laser diode is turned off, the liquid metal cools off and resolidifies. The reservoir is designed such that that the liquid metal does not leave the reservoir even when in liquid state. The laser diode assembly further includes a lid with one or more fin structures that extend into the reservoir and are in contact with the metal in the reservoir.
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Detailed numerical simulations of laser cooling processes
NASA Technical Reports Server (NTRS)
Ramirez-Serrano, J.; Kohel, J.; Thompson, R.; Yu, N.
2001-01-01
We developed a detailed semiclassical numerical code of the forces applied on atoms in optical and magnetic fields to increase the understanding of the different roles that light, atomic collisions, background pressure, and number of particles play in experiments with laser cooled and trapped atoms.
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Forward to cryogenic temperature: laser cooling of Yb: LuLiF crystal
NASA Astrophysics Data System (ADS)
Zhong, Biao; Luo, Hao; Lei, Yongqing; Shi, Yanling; Yin, Jianping
2017-06-01
The high quality Yb-doped fluoride crystals have broad prospects for optical refrigeration. We have laser cooled the Yb:LuLiF crystal to a temperature below the limit of current thermoelectric coolers ( 180 K). The 5% Yb:LuLiF crystal sample has a geometry of 2 mm×2 mm×5 mm and was supported by two fibers of 200 μm in diameter. They were placed in a 2×10-4 Pa vacuum chamber with an environment temperature of 294.5 K. The 1019 nm CW laser of power 38.7 W was adopted to irradiate the sample. The temperature of the sample was measured utilizing the DLT methods. After 20 minutes of laser irradiation, the 5% Yb:LuLiF crystal sample was cooled down to 182.4 K. By further optimizing experimental conditions and increasing the doped Yb concentration, the Yb:LuLiF crystal might be optically cooled below the cryogenic temperature of 123K in the near future.
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Thermal management in inertial fusion energy slab amplifiers
DOE Office of Scientific and Technical Information (OSTI.GOV)
Sutton, S.B.; Albrecht, G.F.
As the technology associated with the development of solid-state drivers for inertial fusion energy (IFE) has evolved, increased emphasis has been placed on the development of an efficient approach for managing the waste heat generated in the laser media. This paper addresses the technical issues associated with the gas cooling of large aperture slabs, where the laser beam propagates through the cooling fluid. It is shown that the major consequence of proper thermal management is the introduction of simple wedge, or beam steering, into the system. Achieving proper thermal management requires careful consideration of the geometry, cooling fluid characteristics, coolingmore » flow characteristics, as well as the thermal/mechanical/optical characteristics of the laser media. Particularly important are the effects of cooling rate variation and turbulent scattering on the system optical performance. Helium is shown to have an overwhelming advantage with respect to turbulent scattering losses. To mitigate cooling rate variations, the authors introduce the concept of flow conditioning. Finally, optical path length variations across the aperture are calculated. A comparison of two laser materials (S-FAP and YAG) shows the benefit of a nearly a-thermal material on optical variations in the system.« less
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Laser-induced pressure-wave and barocaloric effect during flash diffusivity measurements
DOE Office of Scientific and Technical Information (OSTI.GOV)
Wang, Hsin; Porter, Wallace D.; Dinwiddie, Ralph Barton
We report laser-induced pressure-wave and barocaloric effect captured by an infrared detector during thermal diffusivity measurements. Very fast (< 1 ms) and negative transients during laser flash measurements were captured by the infrared detector on thin, high thermal conductivity samples. Standard thermal diffusivity analysis only focuses the longer time scale thermal transient measured from the back surface due to thermal conduction. These negative spikes are filtered out and ignored as noise or anomaly from instrument. This study confirmed that the initial negative signal was indeed a temperature drop induced by the laser pulse. The laser pulse induced instantaneous volume expansionmore » and the associated cooling in the specimen can be explained by the barocaloric effect. The initial cooling (< 100 microsecond) is also known as thermoelastic effect in which a negative temperature change is generated when the material is elastically deformed by volume expansion. A subsequent temperature oscillation in the sample was observed and only lasted about one millisecond. The pressure-wave induced thermal signal was systematically studied and analyzed. In conclusion, the underlying physics of photon-mechanical-thermal energy conversions and the potential of using this signal to study barocaloric effects in solids are discussed.« less
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Laser-induced pressure-wave and barocaloric effect during flash diffusivity measurements
Wang, Hsin; Porter, Wallace D.; Dinwiddie, Ralph Barton
2017-08-01
We report laser-induced pressure-wave and barocaloric effect captured by an infrared detector during thermal diffusivity measurements. Very fast (< 1 ms) and negative transients during laser flash measurements were captured by the infrared detector on thin, high thermal conductivity samples. Standard thermal diffusivity analysis only focuses the longer time scale thermal transient measured from the back surface due to thermal conduction. These negative spikes are filtered out and ignored as noise or anomaly from instrument. This study confirmed that the initial negative signal was indeed a temperature drop induced by the laser pulse. The laser pulse induced instantaneous volume expansionmore » and the associated cooling in the specimen can be explained by the barocaloric effect. The initial cooling (< 100 microsecond) is also known as thermoelastic effect in which a negative temperature change is generated when the material is elastically deformed by volume expansion. A subsequent temperature oscillation in the sample was observed and only lasted about one millisecond. The pressure-wave induced thermal signal was systematically studied and analyzed. In conclusion, the underlying physics of photon-mechanical-thermal energy conversions and the potential of using this signal to study barocaloric effects in solids are discussed.« less
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Diffusion-cooled high-power single-mode waveguide CO2 laser for transmyocardial revascularization
NASA Astrophysics Data System (ADS)
Berishvili, I. I.; Bockeria, L. A.; Egorov, E. N.; Golubev, Vladimir S.; Galushkin, Michail G.; Kheliminsky, A. A.; Panchenko, Vladislav Y.; Roshin, A. P.; Sigaev, I. Y.; Vachromeeva, M. N.; Vasiltsov, Victor V.; Yoshina, V. I.; Zabelin, Alexandre M.; Zelenov, Evgenii V.
1999-01-01
The paper presents the results on investigations and development of multichannel waveguide CO2 laser with diffusion cooling of active medium excited by discharge of audio-frequency alternating current. The description of high-power single-mode CO2 laser with average beam power up to 1 kW is presented. The result of measurement of the laser basic parameters are offered, as well as the outcomes of performances of the laser head with long active zone, operating in waveguide mode. As an example of application of these laser, various capabilities a description of the developed medical system 'Genom' used in the transmyocardial laser revascularization (TMLR) procedure and clinical results of the possibilities of the TMLR in the surgical treatment are presented.
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Injection locking of a low cost high power laser diode at 461 nm
DOE Office of Scientific and Technical Information (OSTI.GOV)
Pagett, C. J. H.; Moriya, P. H., E-mail: paulohisao@ifsc.usp.br; Celistrino Teixeira, R.
2016-05-15
Stable laser sources at 461 nm are important for optical cooling of strontium atoms. In most existing experiments, this wavelength is obtained by frequency doubling infrared lasers, since blue laser diodes either have low power or large emission bandwidths. Here, we show that injecting less than 10 mW of monomode laser radiation into a blue multimode 500 mW high power laser diode is capable of slaving at least 50% of the power to the desired frequency. We verify the emission bandwidth reduction by saturation spectroscopy on a strontium gas cell and by direct beating of the slave with the mastermore » laser. We also demonstrate that the laser can efficiently be used within the Zeeman slower for optical cooling of a strontium atomic beam.« less
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Laser frequency stabilization using a commercial wavelength meter
NASA Astrophysics Data System (ADS)
Couturier, Luc; Nosske, Ingo; Hu, Fachao; Tan, Canzhu; Qiao, Chang; Jiang, Y. H.; Chen, Peng; Weidemüller, Matthias
2018-04-01
We present the characterization of a laser frequency stabilization scheme using a state-of-the-art wavelength meter based on solid Fizeau interferometers. For a frequency-doubled Ti-sapphire laser operated at 461 nm, an absolute Allan deviation below 10-9 with a standard deviation of 1 MHz over 10 h is achieved. Using this laser for cooling and trapping of strontium atoms, the wavemeter scheme provides excellent stability in single-channel operation. Multi-channel operation with a multimode fiber switch results in fluctuations of the atomic fluorescence correlated to residual frequency excursions of the laser. The wavemeter-based frequency stabilization scheme can be applied to a wide range of atoms and molecules for laser spectroscopy, cooling, and trapping.
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Evaporative Cooling in a Holographic Atom Trap
NASA Technical Reports Server (NTRS)
Newell, Raymond
2003-01-01
We present progress on evaporative cooling of Rb-87 atoms in our Holographic Atom Trap (HAT). The HAT is formed by the interference of five intersecting YAG laser beams: atoms are loaded from a vapor-cell MOT into the bright fringes of the interference pattern through the dipole force. The interference pattern is composed of Talbot fringes along the direction of propagation of the YAG beams, prior to evaporative cooling each Talbot fringe contains 300,000 atoms at 50 micro-K and peak densities of 2 x 10(exp 14)/cu cm. Evaporative cooling is achieved through adiabatically decreasing the intensity of the YAG laser. We present data and calculations covering a range of HAT geometries and cooling procedures.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Makarov, G N; Petin, A N
2016-03-31
We report the results of studies on the isotope-selective infrared multiphoton dissociation (IR MFD) of SF{sub 6} and CF{sub 3}I molecules in a pulsed, gas-dynamically cooled molecular flow interacting with a solid surface. The productivity of this method in the conditions of a specific experiment (by the example of SF{sub 6} molecules) is evaluated. A number of low-energy methods of molecular laser isotope separation based on the use of infrared lasers for selective excitation of molecules are analysed and their productivity is estimated. The methods are compared with those of selective dissociation of molecules in the flow interacting with amore » surface. The advantages of this method compared to the low-energy methods of molecular laser isotope separation and the IR MPD method in the unperturbed jets and flows are shown. It is concluded that this method could be a promising alternative to the low-energy methods of molecular laser isotope separation. (laser separation of isotopes)« less
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Indocyanine green-laser thermolysis of acne vulgaris
NASA Astrophysics Data System (ADS)
Genina, Elina A.; Bashkatov, Alexey N.; Simonenko, Georgy V.; Tuchin, Valery V.; Yaroslavsky, Ilya V.; Altshuler, Gregory B.
2005-08-01
The near-infrared (NIR) laser radiation due to its high penetration depth is widely used in phototherapy and photothermolysis. In application to skin appendages a high selectivity of laser treatment is needed to prevent light action on surrounding tissues. Indocyanine Green (ICG) dye may provide a high selectivity of treatment due to effective ICG uploading by a target and its narrow band of considerable absorption just at the wavelength of the NIR diode laser. The goal of this study is to demonstrate the efficacy of the NIR diode laser photothermolysis in combination with topical application of ICG suggested for treatment of acne vulgaris. Two volunteers with back-located acne were enrolled. Skin sites of subjects were stained by ICG and irradiated by NIR laser-diode light (803 or 809 nm). The individual acne lesions were photothermally treated at 18 W/cm2 (803 nm, 0.5 sec) without skin surface cooling or at 200 W/cm2 (809 nm, 0.5 sec) with cooling. The results of the observations during a month after the treatment have shown that ICG stained acne inflammatory elements were destructed for light exposures of 0.5 sec.
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Internal Energy Distribution in Sympathetically Cooled Molecular Ions
NASA Astrophysics Data System (ADS)
Thompson, Robert I.; Fisher, Amy; Harmon, Thomas; Winslade, Clayton; Ahmadi, Nasser
2002-05-01
Over the past year a research program at the University of Calgary has begun looking at the distribution of energy in the internal degrees of freedom (vibrational and rotational) of trapped and sympathetically cooled molecular ions. Ion traps are capable of holding mixed samples of charged atoms and molecules simultaneously. Atomic ions in the trapped cloud can be laser cooled by traditional techniques. The molecular ions are not directly laser cooled, but all of the trapped particles are charged so they interact strongly through Coulomb forces. It has been experimentally demonstrated that the external or translational degrees of freedom of the non-laser-cooled species are significantly lowered through this interaction (e.g. [1]). However, there is little known about the energy distribution in the in the internal degrees of freedom. This poster will outline the results of our theoretical work, as well as the technical design, construction, and initial work in the laboratory. [1] T. Baba and I. Waki, Jpn. J. Appl. Phys. 35, L1134 (1996).
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Spectroscopic and laser cooling results on Yb3+-doped BaY2F8 single crystal
NASA Astrophysics Data System (ADS)
Bigotta, Stefano; Parisi, Daniela; Bonelli, Lucia; Toncelli, Alessandra; Tonelli, Mauro; Di Lieto, Alberto
2006-07-01
Anti-Stokes cooling has been observed in an Yb3+-doped BaY2F8 single crystal. Single crystals have been grown by the Czochralski technique. The absorption spectra and the emission properties have been measured at room temperature and at 10K. The energy positions of the Stark sublevels of the ground and the excited state manifolds have been determined and separated from the vibronic substructure. The intrinsic decay time of the F5/22 level has been measured taking care of avoiding the effect of multiple reabsorption processes. The theoretical and experimental cooling efficiencies of Yb:BaY2F8 are evaluated and compared with respect to those of the most frequently investigated materials for laser cooling. A temperature drop of almost 4K was measured by pumping the crystal with 3W of laser radiation at ˜1025nm in single pass configuration with a cooling efficiency of ˜3%.
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Effect of temporal pulse shaping on the reduction of laser weld defects in a Pd-Ag-Sn dental alloy.
Bertrand, C; Poulon-Quintin, A
2011-03-01
To describe the influence of pulse shaping on the behavior of a palladium-based dental alloy during laser welding and to show how its choice is effective to promote good weld quality. Single spots, weld beads and welds with 80% overlapping were performed on Pd-Ag-Sn cast plates. A pulsed Nd:Yag laser was used with a specific welding procedure using all the possibilities for pulse-shaping: (1) the square pulse shape as the default setting, (2) a rising edge slope for gradual heating, (3) a falling edge slope to slow the cooling and (4) a combination of a rising and falling edges called bridge shape. The optimization of the pulse shape is supposed to enhance weldability and produce defect-free welds (cracks, pores…) Vickers microhardness measurements were made on cross sections of the welds. A correlation between laser welding parameters and microstructure evolution was found. Hot cracking and internal porosities were systematically detected when using rapid cooling. The presence of these types of defects was significantly reduced with the slow cooling of the molten pool. The best weld quality was obtained with the use of the bridge shape. The use of a slow cooling ramp is the only way to significantly reduce the presence of typical defects within the welds for this Pd-based alloy studied. Copyright © 2010 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.
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Narrow-line magneto-optical cooling and trapping of strongly magnetic atoms.
Berglund, Andrew J; Hanssen, James L; McClelland, Jabez J
2008-03-21
Laser cooling on weak transitions is a useful technique for reaching ultracold temperatures in atoms with multiple valence electrons. However, for strongly magnetic atoms a conventional narrow-line magneto-optical trap (MOT) is destabilized by competition between optical and magnetic forces. We overcome this difficulty in Er by developing an unusual narrow-line MOT that balances optical and magnetic forces using laser light tuned to the blue side of a narrow (8 kHz) transition. The trap population is spin polarized with temperatures reaching below 2 muK. Our results constitute an alternative method for laser cooling on weak transitions, applicable to rare-earth-metal and metastable alkaline earth elements.
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Politi, Yael; Levi, Assi; Lapidoth, Moshe
2016-11-01
Acne scars are a common result of in ammatory acne, affecting many patients worldwide. Among which, atrophic scars are the most prevalent form, presenting as dermal depressions caused by inflammatory degeneration of dermal collagen. Mid-infrared laser skin interaction is characterized by its modest absorption in water and nite penetration to the mid-dermis. Since collagen is a desirable laser target, 1540-nm wavelength is amenable for collagen remodeling within the depressed area of atrophic scars. To evaluate the safety and efficacy of acne scars treatment using an integrated cooling-vacuum-assisted 1540 nm Erbium: Glass Laser. This interventional prospective study included 25 volunteers (10 men, 15 women) with post acne atrophic scars. Patients were treated with a mid-infrared non-fractional 1540 nm Er:Glass laser (Alma Lasers Ltd. Caesarea, Israel) with integrat- ed cooling- vacuum assisted technology. Acne scars were exposed to 3 stacked laser pulses (400-600 mJ/pulse, 4 mm spot size, frequency of 3 Hz). Patients underwent 3-6 treatment sessions with a 2-3 week interval and were followed-up 1 month and 3 months after the last treatment. Clinical photographs were taken by high resolution digital camera before and after treatment. Clinical evaluation was performed by two independent dermatologists and results were graded on a scale of 0 (exacerbation) to 4 (76%-100% improvement). Patients' and physicians' satisfaction were also recorded (on a 1-5 scale). Pain perception and adverse effects were evaluated as well. Almost all patients (24/25) demonstrated a moderate to significant improvement. Average improvement was 3.9 and 4.1 points on the quartile scale used for outcome assessment 1 and 3 months following the last session, respectively. Patient satisfaction rate was 4.2. Side effects were minimal and transient: erythema, mild transient vesicles, and mild pain or inconvenience. CONCLUSION Cooling-Vacuum-Assisted mid-infrared non-fractional Er:Glass 1540 nm laser is safe and effective in the treatment of atrophic acne scars. J Drugs Dermatol. 2016;15(11):1359-1363..
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Laser Cooling for Heavy-Ion Fusion (HIF)
NASA Astrophysics Data System (ADS)
Ho, D. D.-M.; Brandon, S.; Lee, Y.
1997-05-01
A critical requirement for HIF is the ability to focus space-charge dominated beams onto a millimeter-size spot. However, chromatic aberration can result in a substantial fraction of the beam ions falling outside the spot radius. Because of the space-charge force, correcting the chromatic aberration using sextupoles is impractical. Success in laser cooling of low-current ion beams in storage rings leads us to explore the application of laser cooling to HIF. Basic scheme: After the beams have been accelerated to the desired energy by the recirculating induction linac, we let the beams coast around at constant energy. For efficient interaction between the laser and the beam ions, we use Ba+ beams. We use two lasers to pump the transitions in the Ba+ for generating the laser force FL. There is also an auxiliary force Fa, which is in the opposition direction of FL, provided by the induction cores. The momentum spread along the beam can be compressed by FL and Fa. We will present preliminary PIC simulations using the PIC code CONDOR. Potential difficulties caused by velocity space instabilities will be discussed.
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NASA Astrophysics Data System (ADS)
Kijko, V. V.; Ofitserov, Evgenii N.
2006-05-01
Thermooptic distortions of the active element of an axially diode-pumped Nd:YVO4 solid-state laser are studied at different methods of its mounting. The study was performed by the Hartmann method. A mathematical model for calculating the optical power of a thermal lens produced in the crystal upon pumping is developed and verified experimentally. It is shown that the optical power of a thermal lens produced upon axial pumping of the convectively cooled active element sealed off in a copper heat sink is half the optical power observed upon convective cooling of the active element without heat sink. The experimental and theoretical results are in good agreement.
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NASA Astrophysics Data System (ADS)
1991-12-01
The major results of an experimental study of a slab Nd:YAG laser are reported in the article; the laser was successfully developed by the authors. The major findings include the following: (1) a method for cooling the blended flowing air and water, as well the related experimental parameters; (2) by using a crossed lens cavity, the authors further improved the anomalous capability within the compensation cavity of the slab laser, as well as higher insensitivity of the system to maladjustment; and (3) a processing technique and major points of slab YAG laser medium.
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2009-03-30
seeded with 15 W of single-frequency laser light at 1064 nm and cladding -pumped of 700 W in the forward direction and 300 W in the opposite direction...57-W single-mode phosphate fiber laser Our early studies of phosphate fiber lasers taught us that adding an air-hole to the inner cladding and... cladding -pumped with a fiber-coupled laser diode at 977 nm through a dichroic beam splitter placed on the OC side. The fiber ends were cooled using the
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NASA Astrophysics Data System (ADS)
Legg, Thomas; Farries, Mark
2017-02-01
Cold atom interferometers are emerging as important tools for metrology. Designed into gravimeters they can measure extremely small changes in the local gravitational field strength and be used for underground surveying to detect buried utilities, mineshafts and sinkholes prior to civil works. To create a cold atom interferometer narrow linewidth, frequency stabilised lasers are required to cool the atoms and to setup and measure the atom interferometer. These lasers are commonly either GaAs diodes, Ti Sapphire lasers or frequency doubled InGaAsP diodes and fibre lasers. The InGaAsP DFB lasers are attractive because they are very reliable, mass-produced, frequency controlled by injection current and simply amplified to high powers with fibre amplifiers. In this paper a laser system suitable for Rb atom cooling, based on a 1560nm DFB laser and erbium doped fibre amplifier, is described. The laser output is frequency doubled with fibre coupled periodically poled LiNbO3 to a wavelength of 780nm. The output power exceeds 1 W at 780nm. The laser is stabilised at 1560nm against a fibre Bragg resonator that is passively temperature compensated. Frequency tuning over a range of 1 GHz is achieved by locking the laser to sidebands of the resonator that are generated by a phase modulator. This laser design is attractive for field deployable rugged systems because it uses all fibre coupled components with long term proven reliability.
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Frontiers in Laser Cooling, Single-Molecule Biophysics, and Energy Science: A Talk from Eric Cornell
DOE Office of Scientific and Technical Information (OSTI.GOV)
Cornell, Eric
2008-08-30
Eric Cornell presents a talk at Frontiers in Laser Cooling, Single-Molecule Biophysics and Energy Science, a scientific symposium honoring Steve Chu, director of Lawrence Berkeley National Laboratory and recipient of the 1997 Nobel Prize in Physics. The symposium was held August 30, 2008 in Berkeley.
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Frontiers in Laser Cooling, Single-Molecule Biophysics, and Energy Science: A Talk from Kurt Gibble
DOE Office of Scientific and Technical Information (OSTI.GOV)
Gibble, Kurt
2008-08-30
Kurt Gibble presents a talk at Frontiers in Laser Cooling, Single-Molecule Biophysics and Energy Science, a scientific symposium honoring Steve Chu, director of Lawrence Berkeley National Laboratory and recipient of the 1997 Nobel Prize in Physics. The symposium was held August 30, 2008 in Berkeley.
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Frontiers in Laser Cooling, Single-Molecule Biophysics, and Energy Science: A Talk from Jay Keasling
DOE Office of Scientific and Technical Information (OSTI.GOV)
Keasling, Jay
2008-08-30
Jay Keasling presents a talk at Frontiers in Laser Cooling, Single-Molecule Biophysics and Energy Science, a scientific symposium honoring Steve Chu, director of Lawrence Berkeley National Laboratory and recipient of the 1997 Nobel Prize in Physics. The symposium was held August 30, 2008 in Berkeley.
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Frontiers in Laser Cooling, Single-Molecule Biophysics, and Enrgy Science: A Talk by Carl Wieman
Wieman, Carl
2017-12-09
Carl Wieman presents a talk at Frontiers in Laser Cooling, Single-Molecule Biophysics and Energy Science, a scientific symposium honoring Steve Chu, director of Lawrence Berkeley National Laboratory and recipient of the 1997 Nobel Prize in Physics. The symposium was held August 30, 2008 in Berkeley.
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Frontiers in Laser Cooling, Single-Molecule Biophysics, and Energy Science: A Talk from Eric Cornell
Cornell, Eric
2018-02-05
Eric Cornell presents a talk at Frontiers in Laser Cooling, Single-Molecule Biophysics and Energy Science, a scientific symposium honoring Steve Chu, director of Lawrence Berkeley National Laboratory and recipient of the 1997 Nobel Prize in Physics. The symposium was held August 30, 2008 in Berkeley.
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Laser-cooled cesium fountain clock: design and expected performances
NASA Astrophysics Data System (ADS)
Clairon, Andre; Laurent, Phillipe; Nadir, A.; Santarelli, G.; Drewsen, M.; Grison, D.; Lounis, B.; Salomon, C.
1993-04-01
The use of diode lasers to cool and trap Cesium atoms in a low Cs pressure cell allows the construction of a relatively simple and reliable atomic fountain frequency standard. Here we discuss the design and the potentialities of the Cs clock frequency standards being built at L.P.T.F..
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Frontiers in Laser Cooling, Single-Molecule Biophysics, and Energy Science: A Talk from Jay Keasling
Keasling, Jay
2018-02-14
Jay Keasling presents a talk at Frontiers in Laser Cooling, Single-Molecule Biophysics and Energy Science, a scientific symposium honoring Steve Chu, director of Lawrence Berkeley National Laboratory and recipient of the 1997 Nobel Prize in Physics. The symposium was held August 30, 2008 in Berkeley.
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Frontiers in Laser Cooling, Single-Molecule Biophysics, and Enrgy Science: A Talk by Carl Wieman
DOE Office of Scientific and Technical Information (OSTI.GOV)
Wieman, Carl
Carl Wieman presents a talk at Frontiers in Laser Cooling, Single-Molecule Biophysics and Energy Science, a scientific symposium honoring Steve Chu, director of Lawrence Berkeley National Laboratory and recipient of the 1997 Nobel Prize in Physics. The symposium was held August 30, 2008 in Berkeley.
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Frontiers in Laser Cooling, Single-Molecule Biophysics, and Energy Science: A Talk from Kurt Gibble
Gibble, Kurt
2018-02-05
Kurt Gibble presents a talk at Frontiers in Laser Cooling, Single-Molecule Biophysics and Energy Science, a scientific symposium honoring Steve Chu, director of Lawrence Berkeley National Laboratory and recipient of the 1997 Nobel Prize in Physics. The symposium was held August 30, 2008 in Berkeley.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Cornejo, J. M.; Colombano, M.; Doménech, J.
A special ion trap was initially built up to perform β-ν correlation experiments with radioactive ions. The trap geometry is also well suited to perform experiments with laser-cooled ions, serving for the development of a new type of Penning trap, in the framework of the project TRAPSENSOR at the University of Granada. The goal of this project is to use a single {sup 40}Ca{sup +} ion as detector for single-ion mass spectrometry. Within this project and without any modification to the initial electrode configuration, it was possible to perform Doppler cooling on {sup 40}Ca{sup +} ions, starting from large cloudsmore » and reaching single ion sensitivity. This new feature of the trap might be important also for other experiments with ions produced at radioactive ion beam facilities. In this publication, the trap and the laser system will be described, together with their performance with respect to laser cooling applied to large ion clouds down to a single ion.« less
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DiPOLE: a 10 J, 10 Hz cryogenic gas cooled multi-slab nanosecond Yb:YAG laser.
Banerjee, Saumyabrata; Ertel, Klaus; Mason, Paul D; Phillips, P Jonathan; De Vido, Mariastefania; Smith, Jodie M; Butcher, Thomas J; Hernandez-Gomez, Cristina; Greenhalgh, R Justin S; Collier, John L
2015-07-27
The Diode Pumped Optical Laser for Experiments (DiPOLE) project at the Central Laser Facility aims to develop a scalable, efficient high pulse energy diode pumped laser amplifier system based on cryogenic gas cooled, multi-slab ceramic Yb:YAG technology. We present recent results obtained from a scaled down prototype laser system designed for operation at 10 Hz pulse repetition rate. At 140 K, the system generated 10.8 J of energy in a 10 ns pulse at 1029.5 nm when pumped by 48 J of diode energy at 940 nm, corresponding to an optical to optical conversion efficiency of 22.5%. To our knowledge, this represents the highest pulse energy obtained from a cryo cooled Yb laser to date and the highest efficiency achieved by a multi-Joule diode pumped solid state laser system. Additionally, we demonstrated shot-to-shot energy stability of 0.85% rms for the system operated at 7 J, 10 Hz during several runs lasting up to 6 hours, with more than 50 hours in total. We also demonstrated pulse shaping capability and report on beam, wavefront and focal spot quality.
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Diao, Wenting; He, Jun; Liu, Zhi; Yang, Baodong; Wang, Junmin
2012-03-26
By optical injection of an 852-nm extended-cavity diode laser (master laser) to lock the + 1-order sideband of a ~9-GHz-current-modulated diode laser (slave laser), we generate a pair of phase-locked lasers with a frequency difference up to ~9-GHz for a cesium (Cs) magneto-optical trap (MOT) with convenient tuning capability. For a cesium MOT, the master laser acts as repumping laser, locked to the Cs 6S₁/₂ (F = 3) - 6P₃/₂ (F' = 4) transition. When the + 1-order sideband of the 8.9536-GHz-current-modulated slave laser is optically injection-locked, the carrier operates on the Cs 6S₁/₂ (F = 4) - 6P₃/₂ (F' = 5) cooling cycle transition with -12 MHz detuning and acts as cooling/trapping laser. When carrying a 9.1926-GHz modulation signal, this phase-locked laser system can be applied in the fields of coherent population trapping and coherent manipulation of Cs atomic ground states.
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NASA Astrophysics Data System (ADS)
Lang, Ye; Chen, Yanzhong; Liao, Lifen; Guo, Guangyan; He, Jianguo; Fan, Zhongwei
2018-03-01
In high power diode lasers, the input cooling water temperature would affect both output power and output spectrum. In double face pumped slab laser, the spectrum of two laser diode arrays (LDAs) must be optimized for efficiency reason. The spectrum mismatch of two LDAs would result in energy storing decline. In this work, thermal induced efficiency decline due to spectral overlap between high power LDAs and laser medium was investigated. A numerical model was developed to describe the energy storing variation with changing LDAs cooling water temperature and configuration (series/parallel connected). A confirmatory experiment was conducted using a double face pumped slab module. The experiment results show good agreements with simulations.
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Variable emissivity laser thermal control system
Milner, J.R.
1994-10-25
A laser thermal control system for a metal vapor laser maintains the wall temperature of the laser at a desired level by changing the effective emissivity of the water cooling jacket. This capability increases the overall efficiency of the laser. 8 figs.
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Schoenly, Joshua E; Seka, Wolf; Rechmann, Peter
2010-01-01
A frequency-doubled Ti:sapphire laser is shown to selectively ablate dental calculus. The optimal transverse shape of the laser beam, including its variability under water-cooling, is determined for selective ablation of dental calculus. Intensity profiles under various water-cooling conditions were optically observed. The 400-nm laser was coupled into a multimode optical fiber using an f = 2.5-cm lens and light-shaping diffuser. Water-cooling was supplied coaxially around the fiber. Five human tooth samples (four with calculus and one pristine) were irradiated perpendicular to the tooth surface while the tooth was moved back and forth at 0.3 mm/second, varying between 20 and 180 iterations. The teeth were imaged before and after irradiation using light microscopy with a flashing blue light-emitting diode (LED). An environmental scanning electron microscope imaged each tooth after irradiation. High-order super-Gaussian intensity profiles are observed at the output of a fiber coiled around a 4-in. diameter drum. Super-Gaussian beams have a more-homogenous fluence distribution than Gaussian beams and have a higher energy efficiency for selective ablation. Coaxial water-cooling does not noticeably distort the intensity distribution within 1 mm from the optical fiber. In contrast, lasers focused to a Gaussian cross section (< or =50-microm diameter) without fiber propagation and cooled by a water spray are heavily distorted and may lead to variable ablation. Calculus is preferentially ablated at high fluences (> or =2 J/cm(2)); below this fluence, stalling occurs because of photo-bleaching of the calculus. Healthy dental hard tissue is not removed at fluences < or =3 J/cm(2). Supplying laser light to a tooth using an optical fiber with coaxial water-cooling is determined to be the most appropriate method when selectively removing calculus with a frequency-doubled Ti:sapphire laser. Fluences over 2 J/cm(2) are required to remove calculus efficiently since photo-bleaching stalls calculus removal below that value.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Schoenly, J.E.; Seka. W.; Rechmann, P.
A frequency-doubled Ti:sapphire laser is shown to selectively ablate dental calculus. The optimal transverse shape of the laser beam, including its variability under water-cooling, is determined for selective ablation of dental calculus. Intensity profiles under various water-cooling conditions were optically observed. The 400-nm laser was coupled into a multimode optical fiber using an f = 2.5-cm lens and light-shaping diffuser. Water-cooling was supplied coaxially around the fiber. Five human tooth samples (four with calculus and one pristine) were irradiated perpendicular to the tooth surface while the tooth was moved back and forth at 0.3 mm/second, varying between 20 and 180more » iterations. The teeth were imaged before and after irradiation using light microscopy with a flashing blue light-emitting diode (LED). An environmental scanning electron microscope imaged each tooth after irradiation. High-order super-Gaussian intensity profiles are observed at the output of a fiber coiled around a 4-in. diameter drum. Super-Gaussian beams have a morehomogenous fluence distribution than Gaussian beams and have a higher energy efficiency for selective ablation. Coaxial water-cooling does not noticeably distort the intensity distribution within 1 mm from the optical fiber. In contrast, lasers focused to a Gaussian cross section (<=50-mm diameter) without fiber propagation and cooled by a water spray are heavily distorted and may lead to variable ablation. Calculus is preferentially ablated at high fluences (>= 2 J/cm^2); below this fluence, stalling occurs because of photo-bleaching of the calculus. Healthy dental hard tissue is not removed at fluences <=3 J/cm^2. Supplying laser light to a tooth using an optical fiber with coaxial water-cooling is determined to be the most appropriate method when selectively removing calculus with a frequency-doubled Ti:sapphire laser. Fluences over 2 J/cm^2 are required to remove calculus efficiently since photo-bleaching stalls calculus removal below that value.« less
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Ablation-cooled material removal with ultrafast bursts of pulses
NASA Astrophysics Data System (ADS)
Kerse, Can; Kalaycıoğlu, Hamit; Elahi, Parviz; Çetin, Barbaros; Kesim, Denizhan K.; Akçaalan, Önder; Yavaş, Seydi; Aşık, Mehmet D.; Öktem, Bülent; Hoogland, Heinar; Holzwarth, Ronald; Ilday, Fatih Ömer
2016-09-01
The use of femtosecond laser pulses allows precise and thermal-damage-free removal of material (ablation) with wide-ranging scientific, medical and industrial applications. However, its potential is limited by the low speeds at which material can be removed and the complexity of the associated laser technology. The complexity of the laser design arises from the need to overcome the high pulse energy threshold for efficient ablation. However, the use of more powerful lasers to increase the ablation rate results in unwanted effects such as shielding, saturation and collateral damage from heat accumulation at higher laser powers. Here we circumvent this limitation by exploiting ablation cooling, in analogy to a technique routinely used in aerospace engineering. We apply ultrafast successions (bursts) of laser pulses to ablate the target material before the residual heat deposited by previous pulses diffuses away from the processing region. Proof-of-principle experiments on various substrates demonstrate that extremely high repetition rates, which make ablation cooling possible, reduce the laser pulse energies needed for ablation and increase the efficiency of the removal process by an order of magnitude over previously used laser parameters. We also demonstrate the removal of brain tissue at two cubic millimetres per minute and dentine at three cubic millimetres per minute without any thermal damage to the bulk.
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Ablation-cooled material removal with ultrafast bursts of pulses.
Kerse, Can; Kalaycıoğlu, Hamit; Elahi, Parviz; Çetin, Barbaros; Kesim, Denizhan K; Akçaalan, Önder; Yavaş, Seydi; Aşık, Mehmet D; Öktem, Bülent; Hoogland, Heinar; Holzwarth, Ronald; Ilday, Fatih Ömer
2016-09-01
The use of femtosecond laser pulses allows precise and thermal-damage-free removal of material (ablation) with wide-ranging scientific, medical and industrial applications. However, its potential is limited by the low speeds at which material can be removed and the complexity of the associated laser technology. The complexity of the laser design arises from the need to overcome the high pulse energy threshold for efficient ablation. However, the use of more powerful lasers to increase the ablation rate results in unwanted effects such as shielding, saturation and collateral damage from heat accumulation at higher laser powers. Here we circumvent this limitation by exploiting ablation cooling, in analogy to a technique routinely used in aerospace engineering. We apply ultrafast successions (bursts) of laser pulses to ablate the target material before the residual heat deposited by previous pulses diffuses away from the processing region. Proof-of-principle experiments on various substrates demonstrate that extremely high repetition rates, which make ablation cooling possible, reduce the laser pulse energies needed for ablation and increase the efficiency of the removal process by an order of magnitude over previously used laser parameters. We also demonstrate the removal of brain tissue at two cubic millimetres per minute and dentine at three cubic millimetres per minute without any thermal damage to the bulk.
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A Completely Solid-State Tunable Ti:Sapphire Laser System
NASA Technical Reports Server (NTRS)
Guerra, David V.; Coyle, D. Barry; Krebs, Danny J.
1994-01-01
Compact, completely solid-state tunable pulsed laser system passively cooled developed for potential employment in aircraft and sounding-rocket lidar experiments. Ti:sapphire based laser system pumped with frequency-doubled diode-pumped Nd:YAG. Rugged, self-contained system extremely flexible and provides pulsed output at specific frequencies with low input-power requirements. In-situ measurements enables scientists to study upper-atmosphere dynamics. Tuning range easily extended to bands between 650-950 nm in order to study other atmospheric constituents.
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Developing Density of Laser-Cooled Neutral Atoms and Molecules in a Linear Magnetic Trap
NASA Astrophysics Data System (ADS)
Velasquez, Joe, III; Walstrom, Peter; di Rosa, Michael
2013-05-01
In this poster we show that neutral particle injection and accumulation using laser-induced spin flips may be used to form dense ensembles of ultracold magnetic particles, i.e., laser-cooled paramagnetic atoms and molecules. Particles are injected in a field-seeking state, are switched by optical pumping to a field-repelled state, and are stored in the minimum-B trap. The analogous process in high-energy charged-particle accumulator rings is charge-exchange injection using stripper foils. The trap is a linear array of sextupoles capped by solenoids. Particle-tracking calculations and design of our linear accumulator along with related experiments involving 7Li will be presented. We test these concepts first with atoms in preparation for later work with selected molecules. Finally, we present our preliminary results with CaH, our candidate molecule for laser cooling. This project is funded by the LDRD program of Los Alamos National Laboratory.
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Solid-state semiconductor optical cryocooler based on CdS nanobelts.
Li, Dehui; Zhang, Jun; Wang, Xinjiang; Huang, Baoling; Xiong, Qihua
2014-08-13
We demonstrate the laser cooling of silicon-on-insulator (SOI) substrate using CdS nanobelts. The local temperature change of the SOI substrate exactly beneath the CdS nanobelts is deduced from the ratio of the Stokes and anti-Stokes Raman intensities from the Si layer on the top of the SOI substrate. We have achieved a 30 and 20 K net cooling starting from 290 K under a 3.8 mW 514 nm and a 4.4 mW 532 nm pumping, respectively. In contrast, a laser heating effect has been observed pumped by 502 and 488 nm lasers. Theoretical analysis based on the general static heat conduction module in the Ansys program package is conducted, which agrees well with the experimental results. Our investigations demonstrate the laser cooling capability of an external thermal load, suggesting the applications of II-VI semiconductors in all-solid-state optical cryocoolers.
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NASA Astrophysics Data System (ADS)
Peng, Steven Y.; Kang, Hyun Wook; Pirzadeh, Homa; Stinson, Douglas
2011-03-01
A novel MoXyTM fiber delivery device with Active Cooling Cap (ACCTM) is designed to transmit up to 180W of 532 nm laser light to treat benign prostatic hyperplasia (BPH). Under such high power tissue ablation, effective cooling is key to maintaining fiber power transmission and ensuring the reliability of the fiber delivery device To handle high power and reduce fiber degradation, the MoXy fiber features a larger core size (750 micrometer) and an internal fluid channel to ensure better cooling of the fiber tip to prevent the cap from burning, detaching, or shattering during the BPH treatment. The internal cooling channel was created with a metal cap and tubing that surrounds the optical fiber. In this study MoXy fibers were used to investigate the effect of power levels of 120 and 200 W on in-vitro bovine prostate ablation using a 532 nm XPSTM laser system. For procedures requiring more than 100 kJ, the MoXy fiber at 200W removed tissue at twice the rate of the current HPS fiber at 120W. The fiber maintained a constant tissue vaporization rate during the entire tissue ablation process. The coagulation at 200W was about 20% thicker than at 120W. In conclusion, the new fibers at 200W doubled the tissue removal rate, maintained vaporization efficiency throughout delivery of 400kJ energy, and induced similar coagulation to the existing HPS fiber at 120W.
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Awe, T. J.; Shelton, K. P.; Sefkow, A. B.; ...
2017-09-25
A cryogenically cooled hardware platform has been developed and commissioned on the Z Facility at Sandia National Laboratories in support of the Magnetized Liner Inertial Fusion (MagLIF) Program. MagLIF is a magneto-inertial fusion concept that employs a magnetically imploded metallic tube (liner) to compress and inertially confine premagnetized and preheated fusion fuel. The fuel is preheated using a ~2 kJ laser that must pass through a ~1.5-3.5-μm-thick polyimide “window” at the target’s laser entrance hole (LEH). As the terawatt-class laser interacts with the dense window, laser plasma instabilities (LPIs) can develop, which reduce the preheat energy delivered to the fuel,more » initiate fuel contamination, and degrade target performance. Cryogenically cooled targets increase the parameter space accessible to MagLIF target designs by allowing nearly 10 times thinner windows to be used for any accessible gas density. Thinner LEH windows reduce the deleterious effects of difficult to model LPIs. The Z Facility’s cryogenic infrastructure has been significantly altered to enable compatibility with the premagnetization and fuel preheat stages of MagLIF. The MagLIF cryostat brings the liquid helium coolant directly to the target via an electrically resistive conduit. This design maximizes cooling power while allowing rapid diffusion of the axial magnetic field supplied by external Helmholtz-like coils. A variety of techniques have been developed to mitigate the accumulation of ice from vacuum chamber contaminants on the cooled LEH window, as even a few hundred nanometers of ice would impact laser energy coupling to the fuel region. Here, the MagLIF cryostat has demonstrated compatibility with the premagnetization and preheat stages of MagLIF and the ability to cool targets to liquid deuterium temperatures in approximately 5 min.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Awe, T. J.; Shelton, K. P.; Sefkow, A. B.
A cryogenically cooled hardware platform has been developed and commissioned on the Z Facility at Sandia National Laboratories in support of the Magnetized Liner Inertial Fusion (MagLIF) Program. MagLIF is a magneto-inertial fusion concept that employs a magnetically imploded metallic tube (liner) to compress and inertially confine premagnetized and preheated fusion fuel. The fuel is preheated using a ~2 kJ laser that must pass through a ~1.5-3.5-μm-thick polyimide “window” at the target’s laser entrance hole (LEH). As the terawatt-class laser interacts with the dense window, laser plasma instabilities (LPIs) can develop, which reduce the preheat energy delivered to the fuel,more » initiate fuel contamination, and degrade target performance. Cryogenically cooled targets increase the parameter space accessible to MagLIF target designs by allowing nearly 10 times thinner windows to be used for any accessible gas density. Thinner LEH windows reduce the deleterious effects of difficult to model LPIs. The Z Facility’s cryogenic infrastructure has been significantly altered to enable compatibility with the premagnetization and fuel preheat stages of MagLIF. The MagLIF cryostat brings the liquid helium coolant directly to the target via an electrically resistive conduit. This design maximizes cooling power while allowing rapid diffusion of the axial magnetic field supplied by external Helmholtz-like coils. A variety of techniques have been developed to mitigate the accumulation of ice from vacuum chamber contaminants on the cooled LEH window, as even a few hundred nanometers of ice would impact laser energy coupling to the fuel region. Here, the MagLIF cryostat has demonstrated compatibility with the premagnetization and preheat stages of MagLIF and the ability to cool targets to liquid deuterium temperatures in approximately 5 min.« less
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Heralded Quantum Gate between Remote Quantum Memories
2009-06-25
emission fre- quency. Second, the geometrical modes from the two fibers are matched to better than 98% as characterized with laser light. Third, the...remains in the trap for several weeks. Doppler-cooling by laser light slightly red detuned from the 2S1=2 $ 2P1=2 transition at 369.5 nm localizes the ions...state decays to the metastable 2D3=2 level. This level is depopulated with a laser near 935.2 nm to maintain efficient cooling and state detection. We
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Conduction cooled compact laser for the supercam Libsraman instrument
NASA Astrophysics Data System (ADS)
Durand, Eric; Derycke, C.; Boudjemaa, L.; Simon-Boisson, C.; Roucayrol, L.; Perez, R.; Faure, B.; Maurice, S.
2017-09-01
A new conduction cooled compact laser for SuperCam LIBS-RAMAN instrument aboard Mars 2020 Rover is presented. An oscillator generates 30mJ at 1µm with a good spatial quality. A Second Harmonic Generator (SHG) at the oscillator output generates 15 mJ at 532 nm. A RTP electro-optical switch, between the oscillator and SHG, allows the operation mode selection (LIBS or RAMAN). Qualification model of this laser has been built and characterised. Environmental testing of this model is also reported.
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Coherent Spectroscopy of Ultra-Cold Mercury for the UV to VUV
2015-11-20
clock. During this funding period a novel UV laser system was developed to efficiently cool and trap atomic Hg to temperatures below 100 microKelvin...During this funding period a novel UV laser system was developed to efficiently cool and trap atomic Hg to temperatures below 100 microKelvin. This...able to slowly scan the UV laser system to locate the clock transition (using the standard technique
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Clock Technology Development in the Laser Cooling and Atomic Physics (LCAP) Program
NASA Technical Reports Server (NTRS)
Seidel, Dave; Thompson, R. J.; Klipstein, W. M.; Kohel, J.; Maleki, L.
2000-01-01
This paper presents the Laser Cooling and Atomic Physics (LCAP) program. It focuses on clock technology development. The topics include: 1) Overview of LCAP Flight Projects; 2) Space Clock 101; 3) Physics with Clocks in microgravity; 4) Space Clock Challenges; 5) LCAP Timeline; 6) International Space Station (ISS) Science Platforms; 7) ISS Express Rack; 8) Space Qualification of Components; 9) Laser Configuration; 10) Clock Rate Comparisons: GPS Carrier Phase Frequency Transfer; and 11) ISS Model Views. This paper is presented in viewgraph form.
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Crystal-field effects in fluoride crystals for optical refrigeration
DOE Office of Scientific and Technical Information (OSTI.GOV)
Hehlen, Markus P
2010-01-01
The field of optical refrigeration of rare-earth-doped solids has recently seen an important breakthrough. The cooling of a YLiF{sub 4} (YLF) crystal doped with 5 mol% Yb3+ to 155 K by Seletskiy et al [NPhot] has surpassed the lowest temperatures ({approx}170 K for {approx}100 mW cooling capacity) that are practical with commercial multi-stage thermoelectric coolers (TEC) [Glaister]. This record performance has advanced laser cooling into an application relevant regime and has put first practical optical cryocoolers within reach. The result is also relevant from a material perspective since for the first time, an Yb3+-doped crystal has outperformed an Yb3+-doped glass.more » The record temperature of 208 K was held by the Yb3+-doped fluorozirconate glass ZBLAN. Advanced purification and glass fabrication methods currently under development are expected to also advance ZBLAN:Yb3+ to sub-TEC temperatures. However, recent achievements with YLF:Yb3+ illustrate that crystalline materials may have two potentially game-changing advantajes over glassy materials. First, the crystalline environment reduces the inhomogeneous broadening of the Yb3+ electronic transitions as compared to a glassy matrix. The respective sharpening of the crystal-field transitions increases the peak absorption cross section at the laser excitation wavelength and allows for more efficient pumping of the Yb3+ ions, particularly at low temperatures. Second, many detrimental impurities present in the starting materials tend to be excluded from the crystal during its slow growth process, in contrast to a glass where all impurities present in the starting materials are included in the glass when it is formed by temperature quenching a melt. The ultra high purity required for laser cooling materials [PRB] therefore may be easier to realize in crystals than in glasses. Laser cooling occurs by laser excitation of a rare-earth ion followed by anti-Stokes luminescence. Each such laser-cooling cycle extracts thermal energy from the solid and carries it away as high-entropy light, thereby cooling the material. In the ideal case, the respective laser-cooling power is given by the pump wavelength ({lambda}{sub p}), the mean fluorescence wavelength ({bar {lambda}}{sub L}), and the absorption coefficient (a{sub r}) of the pumped transition. These quantities are solely determined by crystal field interactions. On one hand, a large crystal-field splitting offers a favorably large difference of {lambda}{sub p} - {bar {lambda}}{sub L} and thus a high cooling efficiency {eta}{sub cool} = ({lambda}{sub p} - {bar {lambda}}{sub L})/{bar {lambda}}{sub L}. On the other hand, a small crystal-field splitting offers a high thermal population (n{sub i}) of the initial state of the pumped transition, giving a high pump absorption coefficient and thus high laser cooling power, particularly at low temperatures. A quantitative description of crystal-field interactions is therefore critical to the understanding and optimization of optical refrigeration. In the case of Yb3+ as the laser cooling ion, however, development of a crystal-field model is met with substantial difficulties. First, Yb3+ has only two 4/multiplets, {sup 2}F{sub 7/2} and {sup 2}F{sub 5/2}, which lead to at most 7 crystal-field levels. This makes it difficult, and in some cases impossible, to evaluate the crystal-field Hamiltonian, which has at least 4 parameters for any Yb3+ point symmety lower than cubic. Second, {sup 2}F{sub 7/2}{leftrightarrow}{sup 2}F{sub 5/2} transitions exhibit an exceptionally strong electron-phonon coupling compared to 4f transitions of other rare earths. This makes it difficult to distinguish electronic from vibronic transitions in the absorption and luminescence spectra and to reliably identify the crystal-field levels. Yb3+ crystal-field splittings reported in the literature should thus generally be viewed with caution. This paper explores the effects of crystal-field interactions on the laser cooling performance of Yb3+-doped fluoride crystals. It is shown that the total crystal-field splitting of the {sup 2}F{sub 7/2} and {sup 2}F{sub 5/2} multiplets of Yb3+ can be estimated from crystal-field splittings of other rare-earth-doped fluoride crystals. This approach takes advantage of an extensive body of experimental work from which Yb3+ doped fluoride crystals with favorable laser cooling properties might be identified. Section 2 reviews the crystal-field splitting of the 4f electronic states and introduces the crystal-field strength as a means to predict the total crystal-field splitting of the {sup 2}F{sub 7/2} and {sup 2}F{sub 5/2} multiplets. Section 3 illustrates the effect of the total {sup 2}F{sub 7/2} crystal field splitting on the laser cooling power. Finally, Section 4 compiles literature data on crystal-field splittings in fluoride crystals from which the {sup 2}F{sub 7/2} splitting is predicted.« less
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Reidl-Leuthner, Christoph; Lendl, Bernhard
2013-12-01
Two thermoelectrically cooled mid-infrared distributed feedback quantum cascade lasers operated in pulsed mode have been used for the quasi-simultaneous determination of NO and NO2 in the sub-parts per million meter (sub-ppm-m) range. Using a beam splitter, the beams of the two lasers were combined and sent to a retro-reflector. The returned light was recorded with a thermoelectrically cooled mercury cadmium telluride detector with a rise time of 4 ns. Alternate operation of the lasers with pulse lengths of 300 ns and a repetition rate of 66 kHz allowed quasi-simultaneous measurements. During each pulse the laser temperature increased, causing a thermal chirp of the laser line of up to 1.3 cm(-1). These laser chirps were sufficient to scan rotational bands of NO centered at 1902 cm(-1) and NO2 located at 1632 cm(-1). In that way an absorption spectrum could be recorded from a single laser pulse. Currently achieved limits of detection are 600 parts per billion meter (ppb-m) for NO and 260 ppb-m for NO2 using signal averaging over 1 min. This work presents the first steps toward a portable stand-off, open-path instrument that uses thermoelectrically cooled detector and lasers.
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Recent developments in CO2 lasers
NASA Astrophysics Data System (ADS)
Du, Keming
1993-05-01
CO2 lasers have been used in industry mainly for such things as cutting, welding, and surface processing. To conduct a broad spectrum of high-speed and high-quality applications, most of the developments in industrial CO2 lasers at the ILT are aimed at increasing the output power, optimizing the beam quality, and reducing the production costs. Most of the commercial CO2 lasers above 5 kW are transverse-flow systems using dc excitation. The applications of these lasers are limited due to the lower beam quality, the poor point stability, and the lower modulation frequency. To overcome the problems we developed a fast axial- flow CO2 laser using rf excitation with an output of 13 kW. In section 2 some of the results are discussed concerning the gas flow, the discharge, the resonator design, optical effects of active medium, the aerodynamic window, and the modulation of the output power. The first CO2 lasers ever built are diffusion-cooled systems with conventional dc excited cylindrical discharge tubes surrounded by cooling jackets. The output power per unit length is limited to 50 W/m by those lasers with cylindrical tubes. In the past few years considerable increases in the output power were achieved, using new mechanical geometries, excitation- techniques, and resonator designs. This progress in diffusion-cooled CO2 lasers is presented in section 3.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Chu, Steve
2008-08-30
Steve Chu, director of Lawrence Berkeley National Laboratory and recipient of the 1997 Nobel Prize, presents a talk at Frontiers in Laser Cooling, Single-Molecule Biophysics and Energy Science, a scientific symposium in his honor. The symposium was held August 30, 2008 in Berkeley.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Holberg, Leo; Mills, Allen
2008-08-30
Leo Holberg and Allen Mills present a talk at Frontiers in Laser Cooling, Single-Molecule Biophysics and Energy Science, a scientific symposium honoring Steve Chu, director of Lawrence Berkeley National Laboratory and recipient of the 1997 Nobel Prize in Physics. The symposium was held August 30, 2008 in Berkeley.
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Holberg, Leo; Mills, Allen
2018-05-07
Leo Holberg and Allen Mills present a talk at Frontiers in Laser Cooling, Single-Molecule Biophysics and Energy Science, a scientific symposium honoring Steve Chu, director of Lawrence Berkeley National Laboratory and recipient of the 1997 Nobel Prize in Physics. The symposium was held August 30, 2008 in Berkeley.
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Slowing techniques for loading a magneto-optical trap of CaF molecules
NASA Astrophysics Data System (ADS)
Truppe, Stefan; Fitch, Noah; Williams, Hannah; Hambach, Moritz; Sauer, Ben; Hinds, Ed; Tarbutt, Mike
2016-05-01
Ultracold molecules in a magneto-optical trap (MOT) are useful for testing fundamental physics and studying strongly-interacting quantum systems. With experiments starting with a relatively fast (50-200 m/s) buffer-gas beam, a primary concern is decelerating molecules to below the MOT capture velocity, typically 10 m/s. Direct laser cooling, where the molecules are slowed via momentum transfer from a chirped counter-propagating narrowband laser, is a natural choice. However, chirping the cooling and repump lasers requires precise control of multiple laser frequencies simultaneously. Another approach, called ``white-light slowing'' uses a broadband laser such that all fast molecules in the beam are decelerated. By addressing numerous velocities no chirping is needed. Unfortunately, both techniques have significant losses as molecules are transversely heated during the optical cycling. Ideally, the slowing method would provide simultaneous deceleration and transverse guiding. A newly developed technique, called Zeeman-Sisyphus deceleration, is potentially capable of both. Using permanent magnets and optical pumping, the number of scattered photons is reduced, lessening transverse heating and relaxing the repump requirements. Here we compare all three options for CaF.
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NASA Astrophysics Data System (ADS)
Vignato, Costantino; Vignato, Giuseppe; Nardelli, Antonella; Baldan, Arianna; Mason, Pier N.
1994-09-01
The purpose of this study was to determine histological and ultrastructural modifications produced by an Nd:YAG pulsed laser beam after an in vivo exposure of human molars. Using a Nd:YAG pulsed laser beam delivered by a 600 micrometers optical fiber and concurrent air and water cooling spray, 14 human third molars with artificial first class cavities were exposed at different power levels (6, 7, and 8 W). All the teeth were extracted at different time periods between 10 and 25 days and prepared for histological examination. The results of the histological examination showed no evidence of degeneration or necrosis of the pulpar tissue. Analysis of the dentinal surfaces after exposure demonstrated that the dentinal tubules are completely closed due to the melted dentin. In conclusion a Nd:YAG pulsed laser beam with an air and water cooling spray is safe for treatments of class I decay and no necrosis or degeneration of the pulp was found for laser powers of 6, 7, and 8 W.
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Dynamics of laser ablation at the early stage during and after ultrashort pulse
NASA Astrophysics Data System (ADS)
Ilnitsky, D. K.; Khokhlov, V. A.; Zhakhovsky, V. V.; Petrov, Yu V.; Migdal, K. P.; Inogamov, N. A.
2016-11-01
Study of material flow in two-temperature states is needed for a fundamental understanding the physics of femtosecond laser ablation. To explore phenomena at a very early stage of laser action on a metallic target our in-house two-temperature hydrodynamics code is used here. The early stage covers duration of laser pulse with next first few picoseconds. We draw attention to the difference in behavior at this stage between the cases: (i) of an ultrathin film (thickness of order of skin depth d skin or less), (ii) thin films (thickness of a film is 4-7 of d skin for gold), and (iii) bulk targets (more than 10d skin for gold). We demonstrate that these differences follow from a competition among conductive cooling of laser excited electrons in a skin layer, electron-ion coupling, and hydrodynamics of unloading caused by excess of pressure of excited free electrons. Conductive cooling of the skin needs a heat sink, which is performed by the cold material outside the skin. Such sink is unavailable in the ultrathin films.
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Cooling of trapped ions by resonant charge exchange
NASA Astrophysics Data System (ADS)
Dutta, Sourav; Rangwala, S. A.
2018-04-01
The two most widely used ion cooling methods are laser cooling and sympathetic cooling by elastic collisions (ECs). Here, we demonstrate another method of cooling ions that is based on resonant charge exchange (RCE) between the trapped ion and the ultracold parent atom. Specifically, trapped C s+ ions are cooled by collisions with cotrapped, ultracold Cs atoms and, separately, by collisions with cotrapped, ultracold Rb atoms. We observe that the cooling of C s+ ions by Cs atoms is more efficient than the cooling of C s+ ions by Rb atoms. This signals the presence of a cooling mechanism apart from the elastic ion-atom collision channel for the Cs-C s+ case, which is cooling by RCE. The efficiency of cooling by RCE is experimentally determined and the per-collision cooling is found to be two orders of magnitude higher than cooling by EC. The result provides the experimental basis for future studies on charge transport by electron hopping in atom-ion hybrid systems.
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Re-weldability tests of irradiated 316L(N) stainless steel using laser welding technique
NASA Astrophysics Data System (ADS)
Yamada, Hirokazu; Kawamura, Hiroshi; Tsuchiya, Kunihiko; Kalinin, George; Kohno, Wataru; Morishima, Yasuo
2002-12-01
SS316L(N)-IG is the candidate material for the in-vessel and ex-vessel components of fusion reactors such as ITER (International Thermonuclear Experimental Reactor). This paper describes a study on re-weldability of un-irradiated and/or irradiated SS316L(N)-IG and the effect of helium generation on the mechanical properties of the weld joint. The laser welding process is used for re-welding of the water cooling branch pipeline repairs. It is clarified that re-welding of SS316L(N)-IG irradiated up to about 0.2 dpa (3.3 appm He) can be carried out without a serious deterioration of tensile properties due to helium accumulation. Therefore, repair of the ITER blanket cooling pipes can be performed by the laser welding process.
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Systematic optimization of laser cooling of dysprosium
NASA Astrophysics Data System (ADS)
Mühlbauer, Florian; Petersen, Niels; Baumgärtner, Carina; Maske, Lena; Windpassinger, Patrick
2018-06-01
We report on an apparatus for cooling and trapping of neutral dysprosium. We characterize and optimize the performance of our Zeeman slower and 2D molasses cooling of the atomic beam by means of Doppler spectroscopy on a 136 kHz broad transition at 626 nm. Furthermore, we demonstrate the characterization and optimization procedure for the loading phase of a magneto-optical trap (MOT) by increasing the effective laser linewidth by sideband modulation. After optimization of the MOT compression phase, we cool and trap up to 10^9 atoms within 3 seconds in the MOT at temperatures of 9 μK and phase space densities of 1.7 \\cdot 10^{-5}, which constitutes an ideal starting point for loading the atoms into an optical dipole trap and for subsequent forced evaporative cooling.
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Rydberg-Dressed Magneto-optical Trap
NASA Astrophysics Data System (ADS)
Bounds, A. D.; Jackson, N. C.; Hanley, R. K.; Faoro, R.; Bridge, E. M.; Huillery, P.; Jones, M. P. A.
2018-05-01
We propose and demonstrate the laser cooling and trapping of Rydberg-dressed Sr atoms. By off-resonantly coupling the excited state of a narrow (7 kHz) cooling transition to a high-lying Rydberg state, we transfer Rydberg properties such as enhanced electric polarizability to a stable magneto-optical trap operating at <1 μ K . Simulations show that it is possible to reach a regime where the long-range interaction between Rydberg-dressed atoms becomes comparable to the kinetic energy, opening a route to combining laser cooling with tunable long-range interactions.
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NASA Astrophysics Data System (ADS)
Hongqi, Jing; Li, Zhong; Yuxi, Ni; Junjie, Zhang; Suping, Liu; Xiaoyu, Ma
2015-10-01
A novel high-efficiency cooling mini-channel heat-sink structure has been designed to meet the package technology demands of high power density laser diode array stacks. Thermal and water flowing characteristics have been simulated using the Ansys-Fluent software. Owing to the increased effective cooling area, this mini-channel heat-sink structure has a better cooling effect when compared with the traditional macro-channel heat-sinks. Owing to the lower flow velocity in this novel high efficient cooling structure, the chillers' water-pressure requirement is reduced. Meanwhile, the machining process of this high-efficiency cooling mini-channel heat-sink structure is simple and the cost is relatively low, it also has advantages in terms of high durability and long lifetime. This heat-sink is an ideal choice for the package of high power density laser diode array stacks. Project supported by the Defense Industrial Technology Development Program (No. B1320133033).
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Relationship of oscillating and average components of laser Doppler flowmetry signal
NASA Astrophysics Data System (ADS)
Mizeva, Irina; Frick, Peter; Podtaev, Sergey
2016-08-01
Signals from laser Doppler flowmeters widely used in intravital studies of skin blood flow include, along with a slowly varying average component, an oscillating part. However, in most clinical studies, pulsations are usually smoothed by data preprocessing and only the mean blood flow is analyzed. To reveal the relationship between average and oscillating perfusion components measured by a laser Doppler flowmeter, we examined the microvascular response to the contralateral cold pressor test recorded at two different sites of the hand: dorsal part of the arm and finger pad. Such a protocol makes it possible to provide a wide range of perfusion. The average perfusion always decreases during cooling, while the oscillating component demonstrates a differently directed response. The wavelet analysis of laser Doppler flowmetry (LDF) signals shows that the pulsatile component is nonlinearly related to the average perfusion. Under low perfusion, the amplitude of pulsations is proportional to its mean value, but, as perfusion increases, the amplitude of pulsations becomes lower. The type of response is defined by the basal perfusion and the degree of vasoconstriction caused by cooling. Interpretation of the results is complicated by the nonlinear transfer function of the LDF device, the contribution of which is studied using artificial examples.
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Control system high-precision laser to obtain the ensemble of ultracold ions Th3+
NASA Astrophysics Data System (ADS)
Florentsev, V. V.; Zhdamirov, V. Yu; Rodko, I. I.; Borodulya, N. A.; Biryukov, A. P.
2018-01-01
One of key problems of nuclear standard frequency development is preparation assembly of ultracold thorium ions in Pauli trap. In this case semiconductive frequency-stabilized lasers with external resonator on frequencies 690 nm, 984 nm, and 1088 nm are used for excitation of corresponding electronic dipole and quadrupole cooling transitions for Th3+ ions. In the paper the results of development and creation of unified laser module, which is able to be used as base for full-featured system designed for laser cooling of Th3+ ions, are presented. The module is able to fine-tune necessary wavelength with accuracy ±5 nm.
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Innovative discharge geometries for diffusion-cooled gas lasers
NASA Astrophysics Data System (ADS)
Lapucci, Antonio
2004-09-01
Large area, narrow discharge gap, diffusion cooled gas lasers are nowadays a well established technology for the construction of industrial laser sources. Successful examples exist both with the slab (Rofin-Sinar) or coaxial (Trumpf) geometry. The main physical properties and the associated technical problems of the transverse large area RF discharge, adopted for the excitation of high power diffusion cooled gas lasers, are reviewed here. The main problems of this technology are related to the maintenance of a uniform and stable plasma excitation between closely spaced large-area electrodes at high power-density loading. Some practical solutions such as distributed resonance of the discharge channel proved successful in the case of square or rectangular cross-sections but hardly applicable to geometries such as that of coaxial electrodes. In this paper we present some solutions, adopted by our group, for the development of slab and annular CO2 lasers and for CO2 laser arrays with linear or circular symmetry. We will also briefly mention the difficulties encountered in the extraction of a good quality beam from an active medium with such a cross section. A problem that has also seen some interesting solutions.
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The Laser Cooling and Magneto-Optical Trapping of the YO Molecule
NASA Astrophysics Data System (ADS)
Yeo, Mark
Laser cooling and magneto-optical trapping of neutral atoms has revolutionized the field of atomic physics by providing an elegant and efficient method to produce cold dense samples of ultracold atoms. Molecules, with their strong anisotropic dipolar interaction promises to unlock even richer phenomenon. However, due to their additional vibrational and rotational degrees of freedom, laser cooling techniques have only been extended to a small set of diatomic molecules. In this thesis, we demonstrate the first magneto-optical trapping of a diatomic molecule using a quasi-cycling transition and an oscillating quadrupole magnetic field. The transverse temperature of a cryogenically produced YO beam was reduced from 25 mK to 10 mK via doppler cooling and further reduced to 2 mK with the addition of magneto-optical trapping forces. The optical cycling in YO is complicated by the presence of an intermediate electronic state, as decays through this state lead to optical pumping into dark rotational states. Thus, we also demonstrate the mixing of rotational states in the ground electronic state using microwave radiation. This technique greatly enhances optical cycling, leading to a factor of 4 increase in the YO beam fluorescence and is used in conjunction with a frequency modulated and chirped continuous wave laser to longitudinally slow the YO beam. We generate YO molecules below 10 m/s that are directly loadable into a three-dimensional magneto-optical trap. This mixing technique provides an alternative to maintaining rotational closure and should extend laser cooling to a larger set of molecules.
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NASA Astrophysics Data System (ADS)
Klusemann, Benjamin; Bambach, Markus
2018-05-01
Processing conditions play a crucial role for the resulting microstructure and properties of the material. In particular, processing materials under non-equilibrium conditions can lead to a remarkable improvement of the final properties [1]. Additive manufacturing represents a specific process example considered in this study. Models for the prediction of residual stresses and microstructure in additive manufacturing processes, such as laser metal deposition, are being developed with huge efforts to support the development of materials and processes as well as to support process design [2-4]. Since the microstructure predicted after each heating and cooling cycle induced by the moving laser source enters the phase transformation kinetics and microstucture evolution of the subsequent heating and cooling cycle, a feed-back loop for the microstructure calculation is created. This calculation loop may become unstable so that the computed microstructure and related properties become very sensitive to small variations in the input parameters, e.g. thermal conductivity. In this paper, a model for phase transformation in Ti-6Al-4V, originally proposed by Charles Murgau et al. [5], is adopted and minimal adjusted concerning the decomposition of the martensite phase are made. This model is subsequently used to study the changes in the predictions of the different phase volume fractions during heating and cooling under the conditions of laser metal deposition with respect to slight variations in the thermal process history.
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Lai, Man-Hong; Lim, Kok-Sing; Gunawardena, Dinusha S; Yang, Hang-Zhou; Chong, Wu-Yi; Ahmad, Harith
2015-03-01
In this work, we have demonstrated thermal stress relaxation in regenerated fiber Bragg gratings (RFBGs) by using direct CO₂-laser annealing technique. After the isothermal annealing and slow cooling process, the Bragg wavelength of the RFBG has been red-shifted. This modification is reversible by re-annealing and rapid cooling. It is repeatable with different cooling process in the subsequent annealing treatments. This phenomenon can be attributed to the thermal stress modification in the fiber core by means of manipulation of glass transition temperature with different cooling rates. This finding in this investigation is important for accurate temperature measurement of RFBG in dynamic environment.
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A homogeneous cooling scheme investigation for high power slab laser
NASA Astrophysics Data System (ADS)
He, Jianguo; Lin, Weiran; Fan, Zhongwei; Chen, Yanzhong; Ge, Wenqi; Yu, Jin; Liu, Hao; Mo, Zeqiang; Fan, Lianwen; Jia, Dan
2017-10-01
The forced convective heat transfer with the advantages of reliability and durability is widely used in cooling the laser gain medium. However, a flow direction induced temperature gradient always appears. In this paper, a novel cooling configuration based on longitudinal forced convective heat transfer is presented. In comparison with two different types of configurations, it shows a more efficient heat transfer and more homogeneous temperature distribution. The investigation of the flow rate reveals that the higher flow rate the better cooling performance. Furthermore, the simulation results with 20 L/min flow rate shows an adequate temperature level and temperature homogeneity which keeps a lower hydrostatic pressure in the flow path.
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NASA Astrophysics Data System (ADS)
Dian, Brian C.; Florio, Gina M.; Clarkson, Jasper R.; Longarte, Asier; Zwier, Timothy S.
2004-05-01
The conformational isomerization dynamics of melatonin and 5-methoxy N-acetyltryptophan methyl amide (5-methoxy NATMA) have been studied using the methods of IR-UV hole-filling spectroscopy and IR-induced population transfer spectroscopy. Using these techniques, single conformers of melatonin were excited via a well-defined NH stretch fundamental with an IR pump laser. This excess energy was used to drive conformational isomerization. By carrying out the infrared excitation early in a supersonic expansion, the excited molecules were re-cooled into their zero-point levels, partially re-filling the hole created in the ground state population of the excited conformer, and creating gains in population of the other conformers. These changes in population were detected using laser-induced fluorescence downstream in the expansion via an UV probe laser. The isomerization quantum yields for melatonin show some conformation specificity but no hint of vibrational mode specificity. In 5-methoxy NATMA, no isomerization was observed out of the single conformational well populated in the expansion in the absence of the infrared excitation. In order to study the dependence of the isomerization on the cooling rate, the experimental arrangement was modified so that faster cooling conditions could be studied. In this arrangement, the pump and probe lasers were overlapped in space in the high density region of the expansion, and the time dependence of the zero-point level populations of the conformers was probed following selective excitation of a single conformation. The analysis needed to extract isomerization quantum yields from the timing scans was developed and applied to the melatonin timing scans. Comparison between the frequency and time domain isomerization quantum yields under identical experimental conditions produced similar results. Under fast cooling conditions, the product quantum yields were shifted from their values under standard conditions. The results for melatonin are compared with those for N-acetyl tryptophan methyl amide.
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Monolithic microchannel heatsink
Benett, W.J.; Beach, R.J.; Ciarlo, D.R.
1996-08-20
A silicon wafer has slots sawn in it that allow diode laser bars to be mounted in contact with the silicon. Microchannels are etched into the back of the wafer to provide cooling of the diode bars. To facilitate getting the channels close to the diode bars, the channels are rotated from an angle perpendicular to the diode bars which allows increased penetration between the mounted diode bars. This invention enables the fabrication of monolithic silicon microchannel heatsinks for laser diodes. The heatsinks have low thermal resistance because of the close proximity of the microchannels to the laser diode being cooled. This allows high average power operation of two-dimensional laser diode arrays that have a high density of laser diode bars and therefore high optical power density. 9 figs.
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Monolithic microchannel heatsink
Benett, William J.; Beach, Raymond J.; Ciarlo, Dino R.
1996-01-01
A silicon wafer has slots sawn in it that allow diode laser bars to be mounted in contact with the silicon. Microchannels are etched into the back of the wafer to provide cooling of the diode bars. To facilitate getting the channels close to the diode bars, the channels are rotated from an angle perpendicular to the diode bars which allows increased penetration between the mounted diode bars. This invention enables the fabrication of monolithic silicon microchannel heatsinks for laser diodes. The heatsinks have low thermal resistance because of the close proximity of the microchannels to the laser diode being cooled. This allows high average power operation of two-dimensional laser diode arrays that have a high density of laser diode bars and therefore high optical power density.
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Theoretical investigation of the laser cooling of a LiBe molecule
NASA Astrophysics Data System (ADS)
You, Yang; Yang, Chuan-Lu; Wang, Mei-Shan; Ma, Xiao-Guang; Liu, Wen-Wang
2015-09-01
An optical scheme to create the simplest heteronuclear metal ultracold LiBe molecule is proposed based on ab initio quantum chemistry calculations. The potential energy curves, dipole moments, and transition dipole moments of 1 +2Σ , 2 +2Σ , 1 2Π , and 2 2Π states are calculated using the multireference configuration interaction and large basis sets. The analytical functions deduced from the obtained curves are used to determine the rovibrational energy levels, the Franck-Condon factors, and the Einstein coefficients of the states through solving the Schrödinger equation of nuclear movement. The spectroscopic parameters are deduced with the obtained rovibrational energy levels. The Franck-Condon factors (f00:0.998 , f11:0.986 , f22:0.920 ) for the 2 +2Σ(v =0 ) ↔1 +2Σ(v'=0 ) transition are highly diagonally distributed, and the calculated radiative lifetime (74.87 ns) of the 2 +2Σ state is found to be short enough for rapid laser cooling. The results demonstrate that LiBe could be a very promising candidate for laser cooling and a three-cycle laser cooling scheme for the molecule has been proposed.
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Macro-channel cooled high power fiber coupled diode lasers exceeding 1.2kW of output power
NASA Astrophysics Data System (ADS)
Koenning, Tobias; Alegria, Kim; Wang, Zuolan; Segref, Armin; Stapleton, Dean; Faßbender, Wilhelm; Flament, Marco; Rotter, Karsten; Noeske, Axel; Biesenbach, Jens
2011-03-01
We report on a new series of fiber coupled diode laser modules exceeding 1.2kW of single wavelength optical power from a 400um / 0.2NA fiber. The units are constructed from passively cooled laser bars as opposed to other comparably powered, commercially available modules that use micro-channel heat-sinks. Micro-channel heat sinks require cooling water to meet demanding specifications and are therefore prone to failures due to contamination and increase the overall cost to operate and maintain the laser. Dilas' new series of high power fiber coupled diode lasers are designed to eliminate micro channel coolers and their associated failure mechanisms. Low-smile soldering processes were developed to maximize the brightness available from each diode laser bar. The diode laser brightness is optimally conserved using Dilas' recently developed propriety laser bar stacking geometry and optics. A total of 24 bars are coupled into a single fiber core using a polarization multiplexing scheme. The modular design permits further power scaling through wavelength multiplexing. Other customer critical features such as industrial grade fibers, pilot beams, fiber interlocks and power monitoring are standard features on these modules. The optical design and the beam parameter calculations will be presented to explain the inherit design trade offs. Results for single and dual wavelengths modules will be presented.
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PHARAO space atomic clock: new developments on the laser source
NASA Astrophysics Data System (ADS)
Saccoccio, Muriel; Loesel, Jacques; Coatantiec, Claude; Simon, Eric; Laurent, Philippe; Lemonde, Pierre; Maksimovic, I.; Abgrall, M.
2017-11-01
The PHARAO project purpose is to open the way for a new atomic clock generation in space, where laser cooling techniques and microgravity allow high frequency stability and accuracy. The French space agency, CNES is funding and managing the clock construction. The French SYRTE and LKB laboratories are scientific and technical advisers for the clock requirements and the follow-up of subsystem development in industrial companies. EADS SODERN is developing two main subsystems of the PHARAO clock: the Laser Source and the Cesium Tube where atoms are cooled, launched, selected and detected by laser beams. The Laser Source includes an optical bench and electronic devices to generate the laser beams required. This paper describes PHARAO and the role laser beams play in its principle of operation. Then we present the Laser Source design, the technologies involved, and the status of development. Lastly, we focus of a key equipment to reach the performances expected, which is the Extended Cavity Laser Diode.
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Ekelöf, Måns; Manni, Jeffrey; Nazari, Milad; Bokhart, Mark; Muddiman, David C
2018-03-01
Laser systems are widely used in mass spectrometry as sample probes and ionization sources. Mid-infrared lasers are particularly suitable for analysis of high water content samples such as animal and plant tissues, using water as a resonantly excited sacrificial matrix. Commercially available mid-IR lasers have historically been bulky and expensive due to cooling requirements. This work presents a novel air-cooled miniature mid-IR laser with adjustable burst-mode output and details an evaluation of its performance for mass spectrometry imaging. The miniature laser was found capable of generating sufficient energy for complete ablation of animal tissue in the context of an IR-MALDESI experiment with exogenously added ice matrix, yielding several hundred confident metabolite identifications. Graphical abstract The use of a novel miniature 2.94 μm burst-mode laser in IR-MALDESI allows for rapid and sensitive mass spectrometry imaging of a whole mouse.
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Compact atom interferometer using single laser
NASA Astrophysics Data System (ADS)
Chiow, Sheng-wey; Yu, Nan
2018-06-01
A typical atom interferometer requires vastly different laser frequencies at different stages of operation, e.g., near resonant light for laser cooling and far detuned light for atom optics, such that multiple lasers are typically employed. The number of laser units constrains the achievable minimum size and power in practical devices for resource critical environments such as space. We demonstrate a compact atom interferometer accelerometer operated by a single diode laser. This is achieved by dynamically changing the laser output frequency in GHz range while maintaining spectroscopic reference to an atomic transition via a sideband generated by phase modulation. At the same time, a beam path sharing configuration is also demonstrated for a compact sensor head design, in which atom interferometer beams share the same path as that of the cooling beam. This beam path sharing also significantly simplifies three-axis atomic accelerometry in microgravity using single sensor head.
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Jan, Yih-Kuen; Lee, Bernard; Liao, Fuyuan; Foreman, Robert D
2012-10-01
The objectives of this study were to investigate the effects of local cooling on skin blood flow response to prolonged surface pressure and to identify associated physiological controls mediating these responses using the wavelet analysis of blood flow oscillations in rats. Twelve Sprague-Dawley rats were randomly assigned to three protocols, including pressure with local cooling (Δt = -10 °C), pressure with local heating (Δt = 10 °C) and pressure without temperature changes. Pressure of 700 mmHg was applied to the right trochanter area of rats for 3 h. Skin blood flow was measured using laser Doppler flowmetry. The 3 h loading period was divided into non-overlapping 30 min epochs for the analysis of the changes of skin blood flow oscillations using wavelet spectral analysis. The wavelet amplitudes and powers of three frequencies (metabolic, neurogenic and myogenic) of skin blood flow oscillations were calculated. The results showed that after an initial loading period of 30 min, skin blood flow continually decreased under the conditions of pressure with heating and of pressure without temperature changes, but maintained stable under the condition of pressure with cooling. Wavelet analysis revealed that stable skin blood flow under pressure with cooling was attributed to changes in the metabolic and myogenic frequencies. This study demonstrates that local cooling may be useful for reducing ischemia of weight-bearing soft tissues that prevents pressure ulcers.
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Jan, Yih-Kuen; Lee, Bernard; Liao, Fuyuan; Foreman, Robert D.
2012-01-01
The objectives of this study were to investigate the effects of local cooling on skin blood flow response to prolonged surface pressure and to identify associated physiological controls mediating these responses using wavelet analysis of blood flow oscillations in rats. Twelve Sprague Dawley rats were randomly assigned into three protocols, including pressure with local cooling (Δt= −10°C), pressure with local heating (Δt= 10°C), and pressure without temperature changes. Pressure of 700 mmHg was applied to the right trochanter area of rats for 3 hours. Skin blood flow was measured using laser Doppler flowmetry. The 3-hour loading period was divided into non-overlapping 30 min epochs for analysis of the changes of skin blood flow oscillations using wavelet spectral analysis. The wavelet amplitudes and powers of three frequencies (metabolic, neurogenic and myogenic) of skin blood flow oscillations were calculated. The results showed that after an initial loading period of 30 min, skin blood flow continually decreased in the conditions of pressure with heating and of pressure without temperature changes, but maintained stable in the condition of pressure with cooling. Wavelet analysis revealed that stable skin blood flow under pressure with cooling was attributed to changes in the metabolic and myogenic frequencies. This study demonstrates that local cooling may be useful for reducing ischemia of weight-bearing soft tissues that prevents pressure ulcers. PMID:23010955
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Laser treatment of infantile hemangioma: A systematic review.
Chinnadurai, Sivakumar; Sathe, Nila A; Surawicz, Tanya
2016-03-01
To systematically review studies of laser treatment of infantile hemangioma (IH). We searched multiple databases including MEDLINE® and EMBASE from 1982 to June 2015. Two investigators independently screened studies against predetermined criteria and extracted key data. Investigators independently assessed study risk of bias and the strength of the evidence of the body of literature. We identified 29 studies addressing lasers: 4 randomized controlled trials, 8 retrospective cohort studies, and 17 case series. Lasers varied across studies in type, pulse width, or cooling materials. Most comparative studies (n = 9) assessed variations of pulsed dye laser (PDL) and examined heterogeneous endpoints. Most studies reported on treatment of cutaneous lesions. Overall, longer pulse PDL with epidermal cooling was the most commonly used laser for cutaneous lesions; Nd:YAG was the most commonly used intralesionally. Most studies reported a higher success rate with longer pulse PDL compared with observation in managing the size of IH, although the magnitude of effect differed substantially. CO2 laser was used for subglottic IH in a single study, and was noted to have a higher success rate and lower complication rate than both Nd:YAG and observation. Studies comparing laser with β-blockers or in combination with β-blockers reported greater improvements in lesion size in combination arms versus β-blockers alone and greater effects of lasers on mixed superficial and deep IH. Strength of the evidence for outcomes after laser treatments ranged from insufficient to low for effectiveness outcomes. Strength of the evidence was insufficient for the effects of laser compared with β-blockers or in combination with β-blockers as studies evaluated different agents and laser types. Studies assessing outcomes after CO2 and Nd:YAG lasers typically reported some resolution of lesion size, but heterogeneity among studies limits our abilities to draw conclusions. Studies of laser treatment of IH primarily addressed different laser modalities compared with observation or other laser modalities. PDL was the most commonly studied laser type, but multiple variations in treatment protocols did not allow for demonstration of superiority of a single method. Most studies reported a higher success rate with longer pulse PDL compared to observation in managing the size of IH, although the magnitude of effect differed substantially. Studies generally found PDL more effective than other types of lasers for cutaneous lesions. When first introduced as a primary treatment for IH, various laser modalities generally offered superior outcomes compared with steroid therapy and observation. In the era of β-blocker therapy, laser treatment may retain an important role in the treatment of residual and refractory lesions. © 2015 Wiley Periodicals, Inc.
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High Energy 2-Micron Laser Developments
NASA Technical Reports Server (NTRS)
Yu, Jirong; Trieu, Bo C.; Petros, Mulugeta; Bai, Yingxin; Petzar, Paul J.; Koch, Grady J.; Singh, Upendra N.; Kavaya, Michael J.
2007-01-01
A master oscillator power amplifier, high energy Q-switched 2-micron laser system has been recently demonstrated. The laser and amplifiers are all designed in side-pumped rod configuration, pumped by back-cooled conductive packaged GaAlAs diode laser arrays. This 2-micron laser system provides nearly transform limited beam quality.
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Smart laser hole drilling for gas turbine combustors
NASA Astrophysics Data System (ADS)
Laraque, Edy
1991-04-01
A smart laser drilling system, which incorporates air flow inspection-in-process of the holes and intelligent real-time process parameter corrections, is described. The system along with good laser parameter developments is proved to be efficient for producing cooling holes which meet the highest aeronautical standards. To date, the system is used for percussion drilling of combustion chamber cooling holes. The system is considered to be very economical due to the drilling-on-the-fly capability that is capable of drilling up to 3 holes of 0.025-in. dia. per second.
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NASA Astrophysics Data System (ADS)
Schuhmann, Karsten; Kirch, Klaus; Marszałek, Mirosław; Pototschnig, Martin; Sinkunaite, Laura; Wichmann, Gunther; Zeyen, Manuel; Antognini, Aldo
2018-02-01
We present a frequency selective optical setup based on a Gires-Tournois interferometer suitable to enforce single-frequency operation of high power lasers. It is based on a birefringent Gires-Tournois interferometer combined with a λ/4 plate and a polarizer. The high-reflective part of the Gires-Tournois interferometer can be contacted to a heat sink to obtain efficient cooling (similar cooling principle as for the active medium in thin-disk lasers) enabling power scaling up to output powers in the kW range.
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High-energy thermoelectrically cooled Fe:ZnSe laser tunable over 3.75-4.82 μm.
Frolov, M P; Korostelin, Yu V; Kozlovsky, V I; Podmar'kov, Yu P; Skasyrsky, Ya K
2018-02-01
The characteristics of an Fe:ZnSe laser thermoelectrically cooled to 220 K are described. Output energy of 7.5 J and optical-to-optical efficiency of 30% have been demonstrated in single-shot operation at 4.3 μm with a 2.94 μm Er:YAG pump laser. By using an intracavity prism, continuous tuning from 3.75 to 4.82 μm has been obtained at output energy up to 3.1 J.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Liu, Hui; School of Physics, University of Chinese Academy of Sciences, Beijing 100049; Yin, Mojuan
2015-10-12
In this paper, we report on the active filtering and amplification of a single mode from an optical femtosecond laser comb with mode spacing of 250 MHz by optical injection of two external-cavity diode lasers operating in cascade to build a narrow linewidth laser for laser cooling of the strontium atoms in an optical lattice clock. Despite the low injection of individual comb mode of approximately 50 nW, a single comb line at 689 nm could be filtered and amplified to reach as high as 10 mW with 37 dB side mode suppression and a linewidth of 240 Hz. This method could be appliedmore » over a broad spectral band to build narrow linewidth lasers for various applications.« less
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Laser damage testing of optical components under cryogenic conditions
NASA Astrophysics Data System (ADS)
Oulehla, Jindrich; Pokorný, Pavel; Lazar, Josef
2012-11-01
In this contribution we present a technology for deposition and testing of interference coatings for optical components designed to operate in power pulsed lasers. The aim of the technology is to prepare components for high power laser facilities such as ELI (Extreme Light Infrastructure) or HiLASE. ELI is a part of the European plan to build a new generation of large research facilities selected by the European Strategy Forum for Research Infrastructures (ESFRI). These facilities rely on the use of diode pumped solid state lasers (DPSSL). The choice of the material for the lasers' optical components is critical. Some of the most important properties include the ability to be antireflection and high reflection coated to reduce the energy losses and increase the overall efficiency. As large amounts of heat need to be dissipated during laser operation, cryogenic cooling is necessary. The conducted experiments served as preliminary tests of laser damage threshold measurement methodology that we plan to use in the future. We designed a special apparatus consisting of a vacuum chamber and a cooling system. The samples were placed into the vacuum chamber which was evacuated and then the samples were cooled down to approximately 120K and illuminated by a pulsed laser. Pulse duration was in the nanosecond region. Multiple test sites on the sample's surface were used for different laser pulse energies. We used optical and electron microscopy and spectrophotometer measurements for coating investigation after the conducted experiments.
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Laser damage testing of optical components under cryogenic conditions
NASA Astrophysics Data System (ADS)
Oulehla, Jindřich; Pokorný, Pavel; Lazar, Josef
2012-01-01
In this contribution we present a technology for deposition and testing of interference coatings for optical components designed to operate in power pulsed lasers. The aim of the technology is to prepare components for high power laser facilities such as ELI (Extreme Light Infrastructure) or HiLASE. ELI is a part of the Eropean plan to build a new generation of large research facilities selected by the the Eropean Strategy Forum for Research Infrastructures (ESFRI). These facilities rely on the use of diode pumped solid state lasers (DPSSL). The choice of the material or the lasers' optical components is critical. Some of the most important properties include the ability to be antireflection and high reflection coated to reduce the energy losses and increase the overall efficiency. As large amounts of hear need to be dissipated during laser operation, cryogenic cooling is necessary. The conducted experiments served as preliminary tests of laser damage threshold measurement methodology that we plan to use in the future. We designed a special apparatus consistion of a vacuum chamber an a cooling system. The samples were placed into the vacuum chamber which was evacuated and them the samples were cooled down to approximately 120K and illuminated by a pulsed laser. Pulse duration was in the nanosecond region. Multiple test sites on the sample's surface were used for different laser pulse energies. We used optical and electron microscopy and spectrophotometer measurements for coating investigation after the conducted experiments.
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Development of high-power CO2 lasers and laser material processing
NASA Astrophysics Data System (ADS)
Nath, Ashish K.; Choudhary, Praveen; Kumar, Manoj; Kaul, R.
2000-02-01
Scaling laws to determine the physical dimensions of the active medium and optical resonator parameters for designing convective cooled CO2 lasers have been established. High power CW CO2 lasers upto 5 kW output power and a high repetition rate TEA CO2 laser of 500 Hz and 500 W average power incorporated with a novel scheme for uniform UV pre- ionization have been developed for material processing applications. Technical viability of laser processing of several engineering components, for example laser surface hardening of fine teeth of files, laser welding of martensitic steel shroud and titanium alloy under-strap of turbine, laser cladding of Ni super-alloy with stellite for refurbishing turbine blades were established using these lasers. Laser alloying of pre-placed SiC coating on different types of aluminum alloy, commercially pure titanium and Ti-6Al-4V alloy, and laser curing of thermosetting powder coating have been also studied. Development of these lasers and results of some of the processing studies are briefly presented here.
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Quantum enhanced feedback cooling of a mechanical oscillator using nonclassical light.
Schäfermeier, Clemens; Kerdoncuff, Hugo; Hoff, Ulrich B; Fu, Hao; Huck, Alexander; Bilek, Jan; Harris, Glen I; Bowen, Warwick P; Gehring, Tobias; Andersen, Ulrik L
2016-11-29
Laser cooling is a fundamental technique used in primary atomic frequency standards, quantum computers, quantum condensed matter physics and tests of fundamental physics, among other areas. It has been known since the early 1990s that laser cooling can, in principle, be improved by using squeezed light as an electromagnetic reservoir; while quantum feedback control using a squeezed light probe is also predicted to allow improved cooling. Here we show the implementation of quantum feedback control of a micro-mechanical oscillator using squeezed probe light. This allows quantum-enhanced feedback cooling with a measurement rate greater than it is possible with classical light, and a consequent reduction in the final oscillator temperature. Our results have significance for future applications in areas ranging from quantum information networks, to quantum-enhanced force and displacement measurements and fundamental tests of macroscopic quantum mechanics.
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Lee, Bernard; Benyajati, Siribhinya; Woods, Jeffrey A; Jan, Yih-Kuen
2014-05-01
The primary purpose of this feasibility study was to establish a correlation between pro-inflammatory cytokine accumulation and severity of tissue damage during local pressure with various temperatures. The secondary purpose was to compare skin blood flow patterns for assessing the efficacy of local cooling on reducing skin ischemia under surface pressure. Eight Sprague-Dawley rats were assigned to two protocols, including pressure with local cooling (Δt = -10 °C) and pressure with local heating (Δt = 10 °C). Pressure of 700 mmHg was applied to the right trochanter area of rats for 3 h. Skin perfusion quantified by laser Doppler flowmetry and TNF-∗ and IL-1β levels were measured. Our results showed that TNF-α concentrations were increased more significantly with local heating than with local cooling under pressure whereas IL-1β did not change. Our results support the notion that weight bearing soft tissue damage may be reduced through temperature modulation and that non-invasive perfusion measurements using laser Doppler flowmetry may be capable of assessing viability. Furthermore, these results show that perfusion response to loading pressure may be correlated with changes in local pro-inflammatory cytokines. These relationships may be relevant for the development of cooling technologies for reducing risk of pressure ulcers. Copyright © 2014 Tissue Viability Society. Published by Elsevier Ltd. All rights reserved.
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Qualification of Laser Diode Arrays for Mercury Laser Altimeter Mission
NASA Technical Reports Server (NTRS)
Stephen, Mark; Vasilyev, Aleksey; Schafer, John; Allan, Graham R.
2004-01-01
NASA's requirements for high reliability, high performance satellite laser instruments have driven the investigation of many critical components; specifically, 808 nm laser diode array (LDA) pump devices. The MESSENGER mission is flying the Mercury Laser Altimeter (MLA) which is a diode-pumped Nd:YAG laser instrument designed to map the topography of Mercury. The environment imposed on the instrument by the orbital dynamics places special requirements on the laser diode arrays. In order to limit the radiative heating of the satellite from the surface of Mercury, the satellite is designed to have a highly elliptical orbit. The satellite will heat near perigee and cool near apogee. The laser power is cycled during these orbits so that the laser is on for only 30 minutes (perigee) in a 12 hour orbit. The laser heats 10 C while powered up and cools while powered down. In order to simulate these operational conditions, we designed a test to measure the LDA performance while being temperature and power cycled. Though the mission requirements are specific to NASA and performance requirements are derived from unique operating conditions, the results are general and widely applicable. We present results on the performance of twelve LDAs operating for several hundred million pulses. The arrays are 100 watt, quasi-CW, conductively-cooled, 808 nm devices. Prior to testing, we fully characterize each device to establish a baseline for individual array performance and status. Details of this characterization can be found in reference. Arrays are divided into four groups and subjected to the temperature and power cycling matrix are shown.
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Caries selective ablation: the handpiece
NASA Astrophysics Data System (ADS)
Hennig, Thomas; Rechmann, Peter; Holtermann, Andreas
1995-05-01
Caries selective ablation is fixed to a window of fluences predicted by the ablation thresholds of carious and healthy dentin, respectively. The aim of the study was to develop a dental handpiece which guarantees homogeneous fluence at the irradiated tooth surface. Furthermore the point of treatment should be cooled down without energy losses due to the cooling system. We suggest the direct coupling of the laser radiation into a laminar stream of liquid, which acts in turn as a lengthened beam guide. The impacts of the laser radiation and of the cooling medium fall exactly into the same point. Hot ablation debris is removed out of the crater by the flush of the water jet. Fluences are constant if the handpiece is used in contact mode or at a distance. Normally the surface of a bare fiber working in contact mode is destroyed after a few shots. Coupling the laser radiation into a stream of liquid prevents this destruction. Putting together the benefits of this special handpiece short overall treatment times seem to be possible. High average power can be applied to the tooth without the threat of thermal damage. Furthermore no time consuming cutting of the fiber prolongs the treatment time.
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Improved performance of selective ablation using a specially designed handpiece
NASA Astrophysics Data System (ADS)
Hennig, Thomas; Rechmann, Peter
1996-01-01
Selective ablation is fixed to a range of fluences predicted by the ablation thresholds of infected and healthy tooth structures respectively. The aim of the study was to develop a dental handpiece, which guarantees homogeneous fluence at the irradiated tooth surface. Furthermore the point of treatment should be cooled down without energy losses due to the cooling system. We suggest the direct coupling of the laser radiation into a laminar stream of liquid, which may act in turn as a lengthened beam guide. The impacts of the laser radiation and of the cooling medium hit exactly the same point. Hot ablation debris is removed out of the crater by the flush of the water jet. While the surface of a bare fiber working on contact mode is destroyed after a few shots, it was shown that coupling the laser radiation into a stream of liquid prevents this destruction. Putting together the benefits of this special handpiece short overall treatment times seem to be possible. High average power can be applied to the tooth without the threat of thermal damage. Furthermore no time consuming cutting of the fiber prolongs the treatment time.
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ELI-beamlines: progress in development of next generation short-pulse laser systems
NASA Astrophysics Data System (ADS)
Rus, B.; Bakule, P.; Kramer, D.; Naylon, J.; Thoma, J.; Fibrich, M.; Green, J. T.; Lagron, J. C.; Antipenkov, R.; Bartoníček, J.; Batysta, F.; Baše, R.; Boge, R.; Buck, S.; Cupal, J.; Drouin, M. A.; Durák, M.; Himmel, B.; Havlíček, T.; Homer, P.; Honsa, A.; Horáček, M.; Hríbek, P.; Hubáček, J.; Hubka, Z.; Kalinchenko, G.; Kasl, K.; Indra, L.; Korous, P.; Košelja, M.; Koubíková, L.; Laub, M.; Mazanec, T.; Meadows, A.; Novák, J.; Peceli, D.; Polan, J.; Snopek, D.; Šobr, V.; Trojek, P.; Tykalewicz, B.; Velpula, P.; Verhagen, E.; Vyhlídka, Å.; Weiss, J.; Haefner, C.; Bayramian, A.; Betts, S.; Erlandson, A.; Jarboe, J.; Johnson, G.; Horner, J.; Kim, D.; Koh, E.; Marshall, C.; Mason, D.; Sistrunk, E.; Smith, D.; Spinka, T.; Stanley, J.; Stolz, C.; Suratwala, T.; Telford, S.; Ditmire, T.; Gaul, E.; Donovan, M.; Frederickson, C.; Friedman, G.; Hammond, D.; Hidinger, D.; Chériaux, G.; Jochmann, A.; Kepler, M.; Malato, C.; Martinez, M.; Metzger, T.; Schultze, M.; Mason, P.; Ertel, K.; Lintern, A.; Edwards, C.; Hernandez-Gomez, C.; Collier, J.
2017-05-01
Overview of progress in construction and testing of the laser systems of ELI-Beamlines, accomplished since 2015, is presented. Good progress has been achieved in construction of all four lasers based largely on the technology of diode-pumped solid state lasers (DPSSL). The first part of the L1 laser, designed to provide 200 mJ <15 fs pulses at 1 kHz repetition rate, is up and running. The L2 is a development line employing a 10 J / 10 Hz cryogenic gas-cooled pump laser which has recently been equipped with an advanced cryogenic engine. Operation of the L3-HAPLS system, using a gas-cooled DPSSL pump laser and a Ti:sapphire broadband amplifier, was recently demonstrated at 16 J / 28 fs, at 3.33 Hz rep rate. Finally, the 5 Hz OPCPA front end of the L4 kJ laser is up running and amplification in the Nd:glass large-aperture power amplifiers was demonstrated.
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Ultrashort pulse amplification in cryogenically cooled amplifiers
Backus, Sterling J.; Kapteyn, Henry C.; Murnane, Margaret Mary
2004-10-12
A laser amplifier system amplifies pulses in a single "stage" from .about.10.sup.-9 joules to more than 10.sup.-3 joules, with average power of 1-10 watts, and beam quality M.sup.2 <2. The laser medium is cooled substantially below room temperature, as a means to improve the optical and thermal characteristics of the medium. This is done with the medium inside a sealed, evacuated or purged cell to avoid moisture or other materials condensing on the surface. A "seed" pulse from a separate laser is passed through the laser medium, one or more times, in any of a variety of configurations including single-pass, multiple-pass, and regenerative amplifier configurations.
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Stationary Light Pulses in Cold Atomic Media and without Bragg Gratings
DOE Office of Scientific and Technical Information (OSTI.GOV)
Lin, Y.-W.; Liao, W.-T.; Peters, Thorsten
We study the creation of stationary light pulses (SLPs), i.e., light pulses without motion, based on the effect of electromagnetically induced transparency with two counterpropagating coupling fields in cold atoms. We show that the Raman excitations created by counterpropagating probe and coupling fields prohibit the formation of SLPs in media of cold and stationary atoms such as laser-cooled atom clouds, Bose condensates or color-center crystals. A method is experimentally demonstrated to suppress these Raman excitations and SLPs are realized in laser-cooled atoms. Furthermore, we report the first experimental observation of a bichromatic SLP at wavelengths for which no Bragg gratingmore » can be established. Our work advances the understanding of SLPs and opens a new avenue to SLP studies for few-photon nonlinear interactions.« less
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NASA Astrophysics Data System (ADS)
Makarov, Grigorii N.; Petin, A. N.
2006-09-01
The passage of CF3I molecules excited by high-intensity IR laser radiation to high vibrational states (with energy Ev >= 0.3-1.5 eV) and unexcited molecules in a pulsed beam through a converging truncated hollow metal cone cooled to Ts approx 80-85 K and mounted at an angle to the beam axis is studied. It is found that the excited molecules pass much more readily through the cone than the unexcited (vibrationally cold) molecules. This opens the possibility for studying the processes of energy transfer and redistribution over a cold surface covered by molecular (cluster) layers, and for separating excited and unexcited molecules in a beam.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Alessi, David A.; Rosso, Paul A.; Nguyen, Hoang T.
Laser energy absorption and subsequent heat removal from diffraction gratings in chirped pulse compressors poses a significant challenge in high repetition rate, high peak power laser development. In order to understand the average power limitations, we have modeled the time-resolved thermo-mechanical properties of current and advanced diffraction gratings. We have also developed and demonstrated a technique of actively cooling Petawatt scale, gold compressor gratings to operate at 600W of average power - a 15x increase over the highest average power petawatt laser currently in operation. As a result, combining this technique with low absorption multilayer dielectric gratings developed in ourmore » group would enable pulse compressors for petawatt peak power lasers operating at average powers well above 40kW.« less
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11 W narrow linewidth laser source at 780nm for laser cooling and manipulation of Rubidium
NASA Astrophysics Data System (ADS)
Sané, S. S.; Bennetts, S.; Debs, J. E.; Kuhn, C. C. N.; McDonald, G. D.; Altin, P. A.; Close, J. D.; Robins, N. P.
2012-04-01
We present a narrow linewidth continuous laser source with over 11 Watts of output power at 780nm, based on single-pass frequency doubling of an amplified 1560nm fibre laser with 36% efficiency. This source offers a combination of high power, simplicity, mode quality and stability. Without any active stabilization, the linewidth is measured to be below 10kHz. The fibre seed is tunable over 60GHz, which allows access to the D2 transitions in 87Rb and 85Rb, providing a viable high-power source for laser cooling as well as for large-momentum-transfer beamsplitters in atom interferometry. Sources of this type will pave the way for a new generation of high flux, high duty-cycle degenerate quantum gas experiments.
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Alessi, David A.; Rosso, Paul A.; Nguyen, Hoang T.; ...
2016-12-26
Laser energy absorption and subsequent heat removal from diffraction gratings in chirped pulse compressors poses a significant challenge in high repetition rate, high peak power laser development. In order to understand the average power limitations, we have modeled the time-resolved thermo-mechanical properties of current and advanced diffraction gratings. We have also developed and demonstrated a technique of actively cooling Petawatt scale, gold compressor gratings to operate at 600W of average power - a 15x increase over the highest average power petawatt laser currently in operation. As a result, combining this technique with low absorption multilayer dielectric gratings developed in ourmore » group would enable pulse compressors for petawatt peak power lasers operating at average powers well above 40kW.« less
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Solidification in direct metal deposition by LENS processing
NASA Astrophysics Data System (ADS)
Hofmeister, William; Griffith, Michelle
2001-09-01
Thermal imaging and metallographic analysis were used to study Laser Engineered Net Shaping (LENS™) processing of 316 stainless steel and H13 tool steel. The cooling rates at the solid-liquid interface were measured over a range of conduction conditions. The length scale of the molten zone controls cooling rates during solidification in direct metal deposition. In LENS processing, the molten zone ranges from 0.5 mm in length to 1.5 mm, resulting in cooling rates at the solid-liquid interface ranging from 200 6,000 Ks-1.
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Correlation buildup during recrystallization in three-dimensional dusty plasma clusters
DOE Office of Scientific and Technical Information (OSTI.GOV)
Schella, André; Mulsow, Matthias; Melzer, André
2014-05-15
The recrystallization process of finite three-dimensional dust clouds after laser heating is studied experimentally. The time-dependent Coulomb coupling parameter is presented, showing that the recrystallization starts with an exponential cooling phase where cooling is slower than damping by the neutral gas friction. At later times, the coupling parameter oscillates into equilibrium. It is found that a large fraction of cluster states after recrystallization experiments is in metastable states. The temporal evolution of the correlation buildup shows that correlation occurs on even slower time scale than cooling.
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Laser all-ceramic crown removal and pulpal temperature--a laboratory proof-of-principle study.
Rechmann, P; Buu, N C H; Rechmann, B M T; Finzen, F C
2015-11-01
The objective of this proof-of-principle laboratory pilot study was to evaluate the temperature increase in the pulp chamber in a worst case scenario during Er:YAG laser debonding of all-ceramic crowns. Twenty extracted molars were prepared to receive all-ceramic IPS E.max CAD full contour crowns. The crowns were bonded to the teeth with Ivoclar Multilink Automix. Times for laser debonding and temperature rise in the pulp chamber using micro-thermocouples were measured. The Er:YAG was used with 560 mJ/pulse. The irradiation was applied at a distance of 5 mm from the crown surface. Additional air-water spray for cooling was utilized. Each all-ceramic crown was successfully laser debonded with an average debonding time of 135 ± 35 s. No crown fractured, and no damage to the underlying dentin was detected. The bonding cement deteriorated, but no carbonization at the dentin/cement interface occurred. The temperature rise in the pulp chamber averaged 5.4° ± 2.2 °C. During 8 out of the 20 crown removals, the temperature rise exceeded 5.5 °C, lasting 5 to 43 s (average 18.8 ± 11.6 s). A temperature rise of 11.5 °C occurred only once, while seven times the temperature rise was limited to 6.8 ± 0.5 °C. Temperature rises above 5.5 °C occurred only when the laser was applied from one side and additional cooling from the side opposite the irradiation. Er:YAG laser energy can successfully be used to efficiently debond all-ceramic crowns from natural teeth. Temperature rises exceeding 5.5 °C only occur when an additional air/water cooling from a dental syringe is inaccurately directed. To avoid possible thermal damage and to allow further heat diffusion, clinically temperature-reduced water might be applied.
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Bello-Silva, Marina Stella; Wehner, Martin; Eduardo, Carlos de Paula; Lampert, Friedrich; Poprawe, Reinhart; Hermans, Martin; Esteves-Oliveira, Marcella
2013-01-01
This study aimed to evaluate the possibility of introducing ultra-short pulsed lasers (USPL) in restorative dentistry by maintaining the well-known benefits of lasers for caries removal, but also overcoming disadvantages, such as thermal damage of irradiated substrate. USPL ablation of dental hard tissues was investigated in two phases. Phase 1--different wavelengths (355, 532, 1,045, and 1,064 nm), pulse durations (picoseconds and femtoseconds) and irradiation parameters (scanning speed, output power, and pulse repetition rate) were assessed for enamel and dentin. Ablation rate was determined, and the temperature increase measured in real time. Phase 2--the most favorable laser parameters were evaluated to correlate temperature increase to ablation rate and ablation efficiency. The influence of cooling methods (air, air-water spray) on ablation process was further analyzed. All parameters tested provided precise and selective tissue ablation. For all lasers, faster scanning speeds resulted in better interaction and reduced temperature increase. The most adequate results were observed for the 1064-nm ps-laser and the 1045-nm fs-laser. Forced cooling caused moderate changes in temperature increase, but reduced ablation, being considered unnecessary during irradiation with USPL. For dentin, the correlation between temperature increase and ablation efficiency was satisfactory for both pulse durations, while for enamel, the best correlation was observed for fs-laser, independently of the power used. USPL may be suitable for cavity preparation in dentin and enamel, since effective ablation and low temperature increase were observed. If adequate laser parameters are selected, this technique seems to be promising for promoting the laser-assisted, minimally invasive approach.
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NASA Astrophysics Data System (ADS)
Akcaalan, Onder; Kalaycioglu, Hamit; Ilday, F. Omer
Although fs fiber laser systems are powerful technologies for material and tissue processing, limited ablation rates and high energy are drawbacks. Recently, we identified a new regime of laser-material interaction, ablation-cooled laser material removal, where the repetition rate has to be high enough so that the targeted spot size cannot cool down substantially by heat conduction which scales down ablation threshold by several orders of magnitude and reduces thermal effects to the bulk of the target. This opens the door to simplified laser systems for processing. In order to exploit this regime in tissue processing, a compact all-PM-fiber laser amplifier system with an intra-burst repetition rate of 1.5 GHz is developed on a 40 x 65 cm platform. The system is able to produce bursts ranging from 20-ns to 65-ns duration with 20 uJ to 80 uJ total energy, respectively, and pulses with up to 2 uJ individual energy and burst repetition rate ranging from 25 kHz to 200 kHz. The seed signal is generated by a home-built all-normal dispersion oscillator with 385 MHz repetition rate and converted to approximately 1.5 GHz by a multiplier. Amplified pulses are compressed to approximately 250-fs, the shortest pulse width for burst-mode fiber laser systems known to date.
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Precision ablation of dental enamel using a subpicosecond pulsed laser.
Rode, A V; Gamaly, E G; Luther-Davies, B; Taylor, B T; Graessel, M; Dawes, J M; Chan, A; Lowe, R M; Hannaford, P
2003-12-01
In this study we report the use of ultra-short-pulsed near-infrared lasers for precision laser ablation of freshly extracted human teeth. The laser wavelength was approximately 800nm, with pulsewidths of 95 and 150fs, and pulse repetition rates of 1kHz. The laser beam was focused to an approximate diameter of 50microm and was scanned over the tooth surface. The rise in the intrapulpal temperature was monitored by embedded thermocouples, and was shown to remain below 5 degrees C when the tooth was air-cooled during laser treatment. The surface preparation of the ablated teeth, observed by optical and electron microscopy, showed no apparent cracking or heat effects, and the hardness and Raman spectra of the laser-treated enamel were not distinguishable from those of native enamel. This study indicates the potential for ultra-short-pulsed lasers to effect precision ablation of dental enamel.
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Romanos, Georgios E; Belikov, Andrey V; Skrypnik, Alexei V; Feldchtein, Felix I; Smirnov, Michael Z; Altshuler, Gregory B
2015-07-01
Uncovering implants with lasers, while bloodless, has been associated with a risk of implant and bone overheating. The present study evaluated the effect of using a new generation of high-power diode lasers on the temperature of a dental implant and the surrounding tissues using an in vitro model. The implant temperature was measured at three locations using micro thermocouples. Collateral thermal damage of uncovered soft tissues was evaluated using NTBC stain. Implant temperature rise during and collateral thermal soft-tissue damage following implant uncovering with and without tissue air-cooling was studied using both the classic operational mode and the new thermo-optically powered (TOP) technology. For the classic surgical mode using a cork-initiated tip and constant laser power set at 3.4 W, the maximum temperature rise in the coronal and apical parts of the implant was 23.2 ± 4.1°С and 9.5 ± 1.8°С, respectively, while 1.5 ± 0.5 mm of collateral thermal damage of the soft tissue surrounding the implant model occurred. Using the TOP surgical tip with constant laser power reduced implant overheating by 30%; collateral thermal soft-tissue damage was 0.8 ± 0.2 mm. Using the TOP surgical mode with a tip temperature setting of 800°C and air-cooling reduced the implant temperature rise by more than 300%, and only 0.2 ± 0.1 mm of collateral thermal soft-tissue damage occurred, typical for optimized CO2 laser surgery. Furthermore, use of the new generation diode technology (TOP surgical mode) appeared to reduce the time required for implant uncovering by a factor of two, compared to the standard surgical mode. Use of the new generation diode technology (TOP surgical mode) may significantly reduce overheating of dental implants during uncovering and seems to be safer for the adjacent soft and hard tissues. Use of such diode lasers with air-cooling can radically reduce the rise in implant temperatures (by more than three times), potentially making this technology safe and effective for implant uncovering. © 2015 Wiley Periodicals, Inc.
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Hsiao, Yen-Chang; Chang, Cheng-Jen
2011-01-01
Background and Aims: Currently, the method of choice for the treatment of port-wine stains is laser photocoagulation. Because of evolving treatment options, it is no longer enough for port-wine stains merely to be lightened through laser treatment. The best course of management consists of the most appropriate laser that will produce the most complete clearing of a lesion in the fewest treatment sessions with the least morbidity. The goal is generally accomplished with the use of yellow-light lasers. Materials (Subjects) and Methods: Absorption of laser energy by melanin causes localized heating in the epidermis, which may, if not controlled, produce permanent complications such as hypertrophic scarring or dyspigmentation. Refinements of the results can be achieved by using the flashlamp-pumped pulsed dye laser (FLPDL) in conjunction with the cryogen spray cooling (CSC) system. In our related studies, the infrared thermal image instrument is used for doctors in determining the optimum laser light dosage and preventing the side effects caused by FLPDL. Topic application of angiogenesis inhibitor (Imiquimod) in conjunction with pulsed dye laser treatment for the PWS patients has been assessed for improvement of FLPDL treatment. Results: We present the clinical effect of FLPDL, and the efficacy and safety of cooled laser treatment of PWS birthmarks. Our clinical outcome in the laser treatment of patients with PWS has been achieved to maximize thermal impact on targeted vessels, while minimizing adverse complications. Conclusions: CSC in conjunction with FLPDL can improve the treatment of PWS. The infrared image instrument is helpful for doctors in determining the optimum laser light dosage. Topic application of angiogenesis inhibitor (Imiquimod) in conjunction with laser treatment for the PWS patients is promising in the near future. PMID:24155536
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Experimental studies of a zeeman-tuned xenon laser differential absorption apparatus.
Linford, G J
1973-06-01
A Zeeman-tuned cw xenon laser differential absorption device is described. The xenon laser was tuned by axial magnetic fields up to 5500 G generated by an unusually large water-cooled dc solenoid. Xenon laser lines at 3.37 micro, 3.51 micro, and 3.99 micro were tuned over ranges of 6 A, 6 A, and 11 A, respectively. To date, this apparatus has been used principally to study the details of formaldehyde absorption lines lying near the 3 .508-micro xenon laser transition. These experiments revealed that the observed absorption spectrum of formaldehyde exhibits a sufficiently unique spectral structure that the present technique may readily be used to measure relative concentrations of formaldehyde in samples of polluted air.
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Key technologies and applications of laser cooling and trapping {sup 87}Rb atomic system
DOE Office of Scientific and Technical Information (OSTI.GOV)
Ru, Ning, E-mail: runing@buaa.edu.cn; Zhang, Li, E-mail: mewan@buaa.edu.cn; Key Laboratory for Metrology, Changcheng Institute of Metrology and Measurement
2016-06-28
Atom Interferometry is proved to be a potential method for measuring the acceleration of atoms due to Gravity, we are now building a feasible system of cold atom gravimeter. In this paper development and the important applications of laser cooling and trapping atoms are introduced, some key techniques which are used to obtain {sup 87}Rb cold atoms in our experiments are also discussed.
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NASA Technical Reports Server (NTRS)
Shoji, J. M.
1977-01-01
A space vehicle application using 5,000-kw input laser power was conceptually evaluated. A detailed design evaluation of a 10-kw experimental thruster including plasma size, chamber size, cooling, and performance analyses, was performed for 50 psia chamber pressure and using hydrogen as a propellant. The 10-kw hardware fabricated included a water cooled chamber, an uncooled copper chamber, an injector, igniters, and a thrust stand. A 10-kw optical train was designed.
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The ground and low-lying excited states and feasibility of laser cooling for GaH+ and InH+ cations
NASA Astrophysics Data System (ADS)
Zhang, Qing-Qing; Yang, Chuan-Lu; Wang, Mei-Shan; Ma, Xiao-Guang; Liu, Wen-Wang
2018-03-01
The potential energy curves and transition dipole moments of 12Σ+ and 12Π states of GaH+ and InH+ cations are performed by employing ab initio calculations. Based on the potential energy curves, the rotational and vibrational energy levels of the two states are obtained by solving the Schrödinger equation of nuclear movement. The spectroscopic parameters are deduced with the obtained rovibrational energy levels. The spin-orbit coupling effect of the 2Π states for both the GaH+ and InH+ cations are also calculated. The feasibility of laser cooling of GaH+ and InH+ cations are examined by using the results of the electronic and spectroscopic properties. The highly diagonal Franck-Condon factors and appropriate radiative lifetimes are determined by using the potential energy curves and transition dipole moments for the 2Π1/2, 3/2 ↔ 12Σ+ transitions. The results indicate that the 2Π1/2, 3/2 ↔ 12Σ+ transitions of both GaH+ and InH+ cations are appropriate for the close cycle transition of laser cooling. The optical scheme of the laser cooling is constructed for the GaH+ and InH+ cations.
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The advantages and disadvantages of using the TREAT reactor for nuclear laser experiments
NASA Astrophysics Data System (ADS)
Dickson, P. W.; Snyder, A. M.; Imel, G. R.; McConnell, R. J.
The Transient Reactor Test Facility (TREAT) is a large air-cooled test facility located at the Idaho National Engineering Laboratory. Two of the major design features of TREAT, its large size and its being an air-cooled reactor, provide clues to both its advantages and disadvantages for supporting nuclear laser experiments. Its large size, which is dictated by the dilute uranium/graphite fuel, permits accommodation of geometrically large experiments. However, TREAT's large size also results in relatively long transients so that the energy deposited in an experiment is large relative to the peak power available from the reactor. TREAT's air-cooling mode of operation allows its configuration to be changed fairly readily. Due to air cooling, the reactor cools down slowly, permitting only one full power transient a day, which can be a disadvantage in some experimental programs. The reactor is capable of both steady-state or transient operation.
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Laser cooling of MgCl and MgBr in theoretical approach
DOE Office of Scientific and Technical Information (OSTI.GOV)
Wan, Mingjie; Shao, Juxiang; Huang, Duohui
Ab initio calculations for three low-lying electronic states (X{sup 2}Σ{sup +}, A{sup 2}Π, and 2{sup 2}Π) of MgCl and MgBr molecules, including spin-orbit coupling, are performed using multi-reference configuration interaction plus Davidson correction method. The calculations involve all-electronic basis sets and Douglas–Kroll scalar relativistic correction. Spectroscopic parameters well agree with available theoretical and experimental data. Highly diagonally distributed Franck-Condon factors f{sub 00} for A{sup 2}Π{sub 3/2,1/2} (υ′ = 0) → X{sup 2}Σ{sup +}{sub 1/2} (υ″ = 0) are determined for both MgCl and MgBr molecules. Suitable radiative lifetimes τ of A{sup 2}Π{sub 3/2,1/2} (υ′ = 0) states for rapid lasermore » cooling are also obtained. The proposed laser drives A{sup 2}Π{sub 3/2} (υ′ = 0) → X{sup 2}Σ{sup +}{sub 1/2} (υ″ = 0) transition by using three wavelengths (main pump laser λ{sub 00}; two repumping lasers λ{sub 10} and λ{sub 21}). These results indicate the probability of laser cooling MgCl and MgBr molecules.« less
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Sympathetic cooling of a membrane oscillator in a hybrid mechanical-atomic system
NASA Astrophysics Data System (ADS)
Jöckel, Andreas; Faber, Aline; Kampschulte, Tobias; Korppi, Maria; Rakher, Matthew T.; Treutlein, Philipp
2015-01-01
Sympathetic cooling with ultracold atoms and atomic ions enables ultralow temperatures in systems where direct laser or evaporative cooling is not possible. It has so far been limited to the cooling of other microscopic particles, with masses up to 90 times larger than that of the coolant atom. Here, we use ultracold atoms to sympathetically cool the vibrations of a Si3N4 nanomembrane, the mass of which exceeds that of the atomic ensemble by a factor of 1010. The coupling of atomic and membrane vibrations is mediated by laser light over a macroscopic distance and is enhanced by placing the membrane in an optical cavity. We observe cooling of the membrane vibrations from room temperature to 650 ± 230 mK, exploiting the large atom-membrane cooperativity of our hybrid optomechanical system. With technical improvements, our scheme could provide ground-state cooling and quantum control of low-frequency oscillators such as nanomembranes or levitated nanoparticles, in a regime where purely optomechanical techniques cannot reach the ground state.
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Kwolek, J M; Wells, J E; Goodman, D S; Smith, W W
2016-05-01
Simultaneous laser locking of infrared (IR) and ultraviolet lasers to a visible stabilized reference laser is demonstrated via a Fabry-Perot (FP) cavity. LabVIEW is used to analyze the input, and an internal proportional-integral-derivative algorithm converts the FP signal to an analog locking feedback signal. The locking program stabilized both lasers to a long term stability of better than 9 MHz, with a custom-built IR laser undergoing significant improvement in frequency stabilization. The results of this study demonstrate the viability of a simple, computer-controlled, non-temperature-stabilized FP locking scheme for our applications, laser cooling of Ca(+) ions, and its use in other applications with similar modest frequency stabilization requirements.
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High temperature semiconductor diode laser pumps for high energy laser applications
NASA Astrophysics Data System (ADS)
Campbell, Jenna; Semenic, Tadej; Guinn, Keith; Leisher, Paul O.; Bhunia, Avijit; Mashanovitch, Milan; Renner, Daniel
2018-02-01
Existing thermal management technologies for diode laser pumps place a significant load on the size, weight and power consumption of High Power Solid State and Fiber Laser systems, thus making current laser systems very large, heavy, and inefficient in many important practical applications. To mitigate this thermal management burden, it is desirable for diode pumps to operate efficiently at high heat sink temperatures. In this work, we have developed a scalable cooling architecture, based on jet-impingement technology with industrial coolant, for efficient cooling of diode laser bars. We have demonstrated 60% electrical-to-optical efficiency from a 9xx nm two-bar laser stack operating with propylene-glycolwater coolant, at 50 °C coolant temperature. To our knowledge, this is the highest efficiency achieved from a diode stack using 50 °C industrial fluid coolant. The output power is greater than 100 W per bar. Stacks with additional laser bars are currently in development, as this cooler architecture is scalable to a 1 kW system. This work will enable compact and robust fiber-coupled diode pump modules for high energy laser applications.
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NASA Astrophysics Data System (ADS)
Ohse, R. W.
1990-07-01
The necessity for increased high-temperature data reliability and extension of thermophysical property measurements up to 5000 K and above are discussed. A new transient-type laser-autoclave technique (LAT) has been developed to extend density and heat capacity measurements of high-temperature multicomponent systems far beyond their melting and boiling points. Pulsed multibeam laser heating is performed in an autoclave under high inert gas pressure to eliminate evaporation. The spherical samples are positioned by containment-free acoustic levitation regardless of their conductive or magnetic properties. Temperature, spectral and total emittances are determined by a new microsecond six-wavelength pyrometer coupled to a fast digital data acquisition system. The density is determined by high resolution microfocus X-ray shadow technique. The heat capacity is obtained from the cooling rate. Further applications are a combination of the laser-autoclave with splat cooling techniques for metastable structure synthesis and amorphous metals research and an extension of the LAT for the study of critical phenomena and the measurement of critical-point temperatures.
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Pulpal Effects of Enamel Ablation With a Microsecond Pulsed λ=9.3-μm CO2 Laser
Staninec, Michal; Darling, Cynthia L.; Goodis, Harold E.; Pierre, Daniel; Cox, Darren P.; Fan, Kenneth; Larson, Michael; Parisi, Renaldo; Hsu, Dennis; Manesh, Saman K.; Ho, Chi; Hosseini, Mehran; Fried, Daniel
2011-01-01
Background and Objectives In vitro studies have shown that CO2 lasers operating at the highly absorbed 9.3 and 9.6-μm wavelengths with a pulse duration in the range of 10–20-microsecond are well suited for the efficient ablation of enamel and dentin with minimal peripheral thermal damage. Even though these CO2 lasers are highly promising, they have yet to receive FDA approval. Clinical studies are necessary to determine if excessive heat deposition in the tooth may have any detrimental pulpal effects, particularly at higher ablative fluencies. The purpose of this study was to evaluate the pulpal safety of laser irradiation of tooth occlusal surfaces under the conditions required for small conservative preparations confined to enamel. Study Design/Materials and Methods Test subjects requiring removal of third molar teeth were recruited and teeth scheduled for extraction were irradiated using a pulsed CO2 laser at a wavelength of 9.3 μm operating at 25 or 50 Hz using a incident fluence of 20 J/cm2 for a total of 3,000 laser pulses (36 J) for both rates with water cooling. Two control groups were used, one with no treatment and one with a small cut made with a conventional high-speed hand-piece. No anesthetic was used for any of the procedures and tooth vitality was evaluated prior to treatment by heat, cold and electrical testing. Short term effects were observed on teeth extracted within 72 hours after treatment and long term effects were observed on teeth extracted 90 days after treatment. The pulps of the teeth were fixed with formalin immediately after extraction and subjected to histological examination. Additionally, micro-thermocouple measurements were used to estimate the potential temperature rise in the pulp chamber of extracted teeth employing the same irradiation conditions used in vivo. Results Pulpal thermocouple measurements showed the internal temperature rise in the tooth was within safe limits, 3.3±4°C without water cooling versus 1.7±6°C with water-cooling, n=25, P<0.05. None of the control or treatment groups showed any deleterious effects on pulpal tissues and none of the 29 test-subjects felt pain or discomfort after the procedure. Only two test-subjects felt discomfort from “cold sensitivity” during the procedure caused by the water-spray. Conclusion It appears that this CO2 laser can ablate enamel safely without harming the pulp under the rate of energy deposition employed in this study. Lasers Surg. PMID:19347946
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NASA Astrophysics Data System (ADS)
Mouton, Thomas; Mercier, Xavier; Desgroux, Pascale
2016-05-01
Jet-cooled laser-induced fluorescence is a spectroscopic method, specifically developed for the study of PAHs formed in flames. This technique has already been used to measure different aromatic species in sooting low-pressure methane flames such as benzene, naphthalene, and pyrene. The use of the LIF technique to excite PAHs drastically cooled down inside a supersonic jet offers the possibility to get selective and quantitative profiles of PAHs sampled from sooting flames. In this paper, we demonstrate the ability of this experimental method to separate the contribution of two mass isomers generated in sooting flames which are the pyrene and the fluoranthene. The selectivity of the method is demonstrated by studying the spectral properties of these species. The method is then applied to the measurement of both these species in two sooting flames with different equivalence ratios and stabilized at 200 torr (26.65 kPa). The sensitivity of the technique has been found to reach a few ppb in the case of fluoranthene measurements.
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NASA Astrophysics Data System (ADS)
Zheleznov, D. S.; Voitovich, A. V.; Mukhin, I. B.; Palashov, O. V.; Khazanov, E. A.
2006-04-01
It is shown experimentally that cooling of a Faraday isolator to liquid nitrogen temperature considerably suppresses the thermally induced depolarisation and reduces the thermal lens. This leads to an increase in the maximum average laser radiation power passing through the isolator by a factor of more than thirty for the same degree of isolation. It is shown that for the same level of cooling, conventional Faraday isolators can operate for powers up to 10 kW, while isolators with compensation of depolarisation and thermal lens can operate up to 100 kW.
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Building one molecule from a reservoir of two atoms
NASA Astrophysics Data System (ADS)
Liu, L. R.; Hood, J. D.; Yu, Y.; Zhang, J. T.; Hutzler, N. R.; Rosenband, T.; Ni, K.-K.
2018-05-01
Chemical reactions typically proceed via stochastic encounters between reactants. Going beyond this paradigm, we combined exactly two atoms in a single, controlled reaction. The experimental apparatus traps two individual laser-cooled atoms [one sodium (Na) and one cesium (Cs)] in separate optical tweezers and then merges them into one optical dipole trap. Subsequently, photoassociation forms an excited-state NaCs molecule. The discovery of previously unseen resonances near the molecular dissociation threshold and measurement of collision rates are enabled by the tightly trapped ultracold sample of atoms. As laser-cooling and trapping capabilities are extended to more elements, the technique will enable the study of more diverse, and eventually more complex, molecules in an isolated environment, as well as synthesis of designer molecules for qubits.
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Indium Single-Ion Frequency Standard
NASA Technical Reports Server (NTRS)
Nagourney, Warren
2001-01-01
A single laser-cooled indium ion is a promising candidate for an ultimate resolution optical time or frequency standard. It can be shown that single ions from group IIIA of the periodic table (indium, thallium, etc.) can have extremely small systematic errors. In addition to being free from Doppler, transit-time and collisional shifts, these ions are also quite insensitive to perturbations from ambient magnetic and electric fields (mainly due to the use of a J=0-0 transition for spectroscopy). Of all group IIIA ions, indium seems to be the most practical, since it is heavy enough to have a tolerable intercombination cooling transition rate and (unlike thallium) has transitions which are easily accessible with frequency multiplied continuous-wave lasers. A single indium ion standard has a potential inaccuracy of one part in 10(exp 18) for integration times of 10(exp 6) seconds. We have made substantial progress during the grant period in constructing a frequency standard based upon a single indium ion. At the beginning of the grant period, single indium ions were being successfully trapped, but the lasers and optical systems were inadequate to achieve the desired goal. We have considerably improved the stability of the dye laser used to cool the ions and locked it to a molecular resonance line, making it possible to observe stable cooling-line fluorescence from a single indium ion for reasonable periods of time, as required by the demands of precision spectroscopy. We have substantially improved the single-ion fluorescence signal with significant benefits for the detection efficiency of forbidden transitions using the 'shelving' technique. Finally, we have constructed a compact, efficient UV 'clock' laser and observed 'clock' transitions in single indium ions using this laser system. We will elaborate on these accomplishments.
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NASA Technical Reports Server (NTRS)
Jones, W. S.; Forsyth, J. B.; Skratt, J. P.
1979-01-01
The laser rocket systems investigated in this study were for orbital transportation using space-based, ground-based and airborne laser transmitters. The propulsion unit of these systems utilizes a continuous wave (CW) laser beam focused into a thrust chamber which initiates a plasma in the hydrogen propellant, thus heating the propellant and providing thrust through a suitably designed nozzle and expansion skirt. The specific impulse is limited only by the ability to adequately cool the thruster and the amount of laser energy entering the engine. The results of the study showed that, with advanced technology, laser rocket systems with either a space- or ground-based laser transmitter could reduce the national budget allocated to space transportation by 10 to 345 billion dollars over a 10-year life cycle when compared to advanced chemical propulsion systems (LO2-LH2) of equal capability. The variation in savings depends upon the projected mission model.
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Burton, Harry; Debardelaben, Christopher; Amir, Wafa; Planchon, Thomas A
2017-03-20
The fluorescence spectra of titanium doped sapphire (Ti:Sapphire) crystals were measured for temperature ranging from 300K to 77K. The resulting gain cross-section line shapes were calculated and used in a three-dimensional amplification model to illustrate the importance of the precise knowledge of these fluorescence spectra for the design of cryogenic cooled Ti:Sapphire based chirped-pulse laser amplifiers.
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Spectroscopy of a Synthetic Trapped Ion Qubit
NASA Astrophysics Data System (ADS)
Hucul, David; Christensen, Justin E.; Hudson, Eric R.; Campbell, Wesley C.
2017-09-01
133Ba+ has been identified as an attractive ion for quantum information processing due to the unique combination of its spin-1 /2 nucleus and visible wavelength electronic transitions. Using a microgram source of radioactive material, we trap and laser cool the synthetic A =133 radioisotope of barium II in a radio-frequency ion trap. Using the same, single trapped atom, we measure the isotope shifts and hyperfine structure of the 62P1 /2↔62S1 /2 and 62P1 /2↔52D3 /2 electronic transitions that are needed for laser cooling, state preparation, and state detection of the clock-state hyperfine and optical qubits. We also report the 62P1 /2↔52D3 /2 electronic transition isotope shift for the rare A =130 and 132 barium nuclides, completing the spectroscopic characterization necessary for laser cooling all long-lived barium II isotopes.
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A new type of caesium clock: a laser-cooled atomic fountain.
NASA Astrophysics Data System (ADS)
Clairon, A.
1995-05-01
In recent years, progress has been made in the field of cooling neutral atoms using a laser. An initial application is the construction of a new type of atomic clock. Today it is easy to produce a gas of caesium atoms at a temperature of a few microkelvins, corresponding to a mean square velocity of the order of 1 cm/s; all that is needed is two laser diodes forming an optical soup in a low pressure caesium cell. In the longer term, these cooled atoms will make it possible to build clocks whose performance will be one or two orders of magnitude better than those that exist at present. A prototype caesium clock using cold atoms has been operating for over a year that the LPTF in the Paris observatory. This article describes its design principles and gives a brief presentation of the results obtained so far.
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NASA Astrophysics Data System (ADS)
Emde, B.; Huse, M.; Hermsdorf, J.; Kaierle, S.; Wesling, V.; Overmeyer, L.; Kozakov, R.; Uhrlandt, D.
As an energy-preserving variant of laser hybrid welding, laser-assisted arc welding uses laser powers of less than 1 kW. Recent studies have shown that the electrical conductivity of a TIG welding arc changes within the arc in case of a resonant interaction between laser radiation and argon atoms. This paper presents investigations on how to control the position of the arc root on the workpiece by means of the resonant interaction. Furthermore, the influence on the welding result is demonstrated. The welding tests were carried out on a cooled copper plate and steel samples with resonant and non-resonant laser radiation. Moreover, an analysis of the weld seam is presented.
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Femtosecond laser-induced phase transformations in amorphous Cu77Ni6Sn10P7 alloy
NASA Astrophysics Data System (ADS)
Zhang, Y.; Liu, L.; Zou, G.; Chen, N.; Wu, A.; Bai, H.; Zhou, Y.
2015-01-01
In this study, the femtosecond laser-induced crystallization of CuNiSnP amorphous ribbons was investigated by utilizing an amplified Ti:sapphire laser system. X-ray diffraction and scanning electronic microscope were applied to examine the phase and morphology changes of the amorphous ribbons. Micromachining without crystallization, surface patterning, and selective crystallization were successfully achieved by changing laser parameters. Obvious crystallization occurred under the condition that the laser fluence was smaller than the ablation threshold, indicating that the structural evolution of the material depends strongly on the laser parameters. Back cooling method was used to inhibit heat accumulation; a reversible transformation between the disordered amorphous and crystalline phases can be achieved by using this method.
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Selective removal of composite sealants with near-UV laser pulses
NASA Astrophysics Data System (ADS)
Louie, Tiffany M.; Jones, Robert S.; Sarma, Anupama V.; Fried, Daniel
2004-05-01
It is often necessary to replace pit and fissure sealants and composite restorations. This task is complicated by the necessity for complete removal of the remaining composite to enable suitable adhesion of new composite. Previous studies have shown that lasers pulses from a frequency-tripled Nd:YAG laser (355-nm) can selectively remove residual composite after orthodontic bracket removal on enamel surfaces. UV laser light is preferentially absorbed by polymeric resins and the organic content of the tooth enamel. The objective of this study was to determine if such laser pulses are suitable for selective removal of the old composite from pit and fissure sealants and restorations without damaging surrounding sound tissues. Optical coherence tomography was used to acquire optical cross sections of the occlusal topography and peripheral tooth structure non-destructively before application of the sealants, after sealant application, and after sealant removal with 355-nm laser pulses with intensities ranging from 0-10 J/cm2. Thermocouples were used to monitor the temperature in the pulp chamber during composite removal under clinically relevant ablation rates, i.e., 30 Hz and 30 mJ per laser pulse. At an irradiation intensity of 1.3 J/cm2 pit and fissure sealants were completely removed without visible damage to the underlying enamel. At intensities above 1.5 J/cm2, the laser removes the resin layer while at the same time preferentially etching the surface of the enamel. Temperature excursions in the pulp chamber of extracted teeth was limited to less than 5°C if air-cooling was used during the rapid removal (1-2 min) of sealants, water-cooling was not needed. This is the first presentation of a method for the selective removal of composite restorative materials without damage to the underlying sound tooth structure.
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Electron beam cooling in intense focussed laser pulses
NASA Astrophysics Data System (ADS)
Yoffe, Samuel R.; Noble, Adam; Macleod, Alexander J.; Jaroszynski, Dino A.
2017-05-01
In the coming years, a new generation of high-power laser facilities (such as the Extreme Light Infrastructure) will become operational, for which it is important to understand how the interaction with intense laser pulses affects the bulk properties of relativistic electron bunches. At such high field intensities, we expect both radiation reaction and quantum effects to have a dominant role to play in determining the dynamics. The reduction in relative energy spread (beam cooling) at the expense of mean beam energy predicted by classical theories of radiation reaction has been shown to occur equally in the longitudinal and transverse directions, whereas this symmetry is broken when the theory is extended to approximate certain quantum effects. The reduction in longitudinal cooling suggests that the effects of radiation reaction could be better observed in measurements of the transverse distribution, which for real-world laser pulses motivates the investigation of the angular dependence of the interaction. Using a stochastic single-photon emission model with a (Gaussian beam) focussed pulse, we find strong angular dependence of the stochastic heating.
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Vibrational Spectroscopy of Laser Cooled CaH
2015-10-28
about 1 mW 369 nm laser with a bandpass filter ( Semrock 395/20 nm) that reflects the 21 399 nm laser and transmits the 369 nm laser, which are sent along...and the back mirror is a flat broadband 67 ( Semrock MaxMirror) mirror that has over 99% reflectivity over a wide range as shown in Fig. 28. The lasers
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New Submount Requirement of Conductively Cooled Laser Diodes for Lidar Applications
NASA Technical Reports Server (NTRS)
Mo, S. Y.; Cutler, A. D.; Choi, S. H.; Lee, M. H.; Singh, U. N.
2000-01-01
New submount technology is essential for the development of conductively cooled high power diode laser. The simulation and experimental results indicate that thermal conductivity of submount for high power laser-diode must be at least 600 W/m/k or higher for stable operation. We have simulated several theoretical thermal model based on new submount designs and characterized high power diode lasers to determine temperature effects on the performances of laser diodes. The characterization system measures the beam power, output beam profile, temperature distribution, and spectroscopic property of high power diode laser. The characterization system is composed of four main parts: an infrared imaging camera, a CCD camera, a monochromator, and a power meter. Thermal characteristics of two commercial-grade CW 20-W diode laser bars with open heat-sink type were determined with respect to the line shift of emission spectra and beam power stability. The center wavelength of laser emission has a tendency to shift toward longer wavelength as the driving current and heat sink temperature are increased. The increase of heat sink temperature decreases the output power of the laser bar too. Such results lay the guidelines for the design of new submount for high power laser-diodes.
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Conceptual design of laser fusion reactor KOYO-fast Concepts of reactor system and laser driver
NASA Astrophysics Data System (ADS)
Kozaki, Y.; Miyanaga, N.; Norimatsu, T.; Soman, Y.; Hayashi, T.; Furukawa, H.; Nakatsuka, M.; Yoshida, K.; Nakano, H.; Kubomura, H.; Kawashima, T.; Nishimae, J.; Suzuki, Y.; Tsuchiya, N.; Kanabe, T.; Jitsuno, T.; Fujita, H.; Kawanaka, J.; Tsubakimoto, K.; Fujimoto, Y.; Lu, J.; Matsuoka, S.; Ikegawa, T.; Owadano, Y.; Ueda, K.; Tomabechi, K.; Reactor Design Committee in Ife Forum, Members Of
2006-06-01
We have carried out the design studies of KOYO-Fast laser fusion power plant, using fast ignition cone targets, DPSSL lasers, and LiPb liquid wall chambers. Using fast ignition targets, we could design a middle sized 300 MWe reactor module, with 200 MJ fusion pulse energy and 4 Hz rep-rates, and 1200MWe modular power plants with 4 reactor modules and a 16 Hz laser driver. The liquid wall chambers with free surface cascade flows are proposed for cooling surface quickly enough to a 4 Hz pulse operation. We examined the potential of Yb-YAG ceramic lasers operated at 150˜ 225 K for both implosion and heating laser systems required for a 16-Hz repetition and 8 % total efficiency.
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Numerical Study of the Features of Ti-Nb Alloy Crystallization during Selective Laser Sintering
NASA Astrophysics Data System (ADS)
Dmitriev, A. I.; Nikonov, A. Y.
2016-07-01
The demand for implants with individual shape requires the development of new methods and approaches to their production. The obvious advantages of additive technologies and selective laser sintering are the capabilities to form both the external shape of the product and its internal structure. Recently appeared and attractive from the perspective of biomechanical compatibility are beta alloys of titanium-niobium that have similar mechanical properties to those of cortical bone. This paper studies the processes occurring at different stages of laser sintering using computer simulation on atomic scale. The effect of cooling rate on the resulting crystal structure of Ti-Nb alloy was analysed. Also, the dependence of tensile strength of sintered particles on heating time and cooling rate was studied. It was shown that the main parameter, which determines the adhesive properties of sintered particles, is the contact area obtained during sintering process. The simulation results can both help defining the technological parameters of the process to provide the desired mechanical properties of the resulting products and serve as a necessary basis for calculations on large scale levels in order to study the behaviour of actually used implants.
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NASA Astrophysics Data System (ADS)
Jung, Sung Suk; Sohn, Il
2012-12-01
The crystallization behavior of a calcium-aluminate system with various MgO content from 2.5 to 7.5 wt pct and CaO/Al2O3 ratios between 0.8 and 1.2 has been examined using a confocal laser scanning microscope (CLSM). CCT (continuous cooling transformation) and time temperature transformation (TTT) diagrams were constructed to identify the primary crystal phase of slag at different compositions and at cooling rates between 25 and 800 K/minutes. In the slag at a CaO/Al2O3 ratio of 1.0, crystallization temperature increased during isothermal and continuous cooling with higher MgO content, and the shortest incubation time was observed at 5 wt pct MgO. When MgO content was fixed to be 5 wt pct, crystallization temperature increased with lower CaO/Al2O3 ratio. According to the slag composition, cooling rates and temperature, the primary phase could be CA, or C5A3, or C3A, or C3MA2, or MgO, and the crystal morphology changes from dendrites to faceted crystals to columnar crystals in this composition range.
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Shot-noise dominant regime of a nanoparticle in a laser beam
NASA Astrophysics Data System (ADS)
Zhong, Changchun; Robicheaux, Francis
2017-04-01
The technique of laser levitation of nanoparticles has become increasingly promising in the study of cooling and controlling mesoscopic quantum systems. Unlike a mechanical system, the levitated nanoparticle is less exposed to thermalization and decoherence due to the absence of direct contact with a thermal environment. In ultrahigh vacuum, the dominant source of decoherence comes from the unavoidable photon recoil from the optical trap which sets an ultimate bound for the control of levitated systems. In this paper, we study the shot noise heating and the parametric feedback cooling of an optically trapped anisotropic nanoparticle in the laser shot noise dominant regime. The rotational trapping frequency and shot noise heating rate have a dependence on the shape of the trapped particle. For an ellipsoidal particle, the ratio of the axis lengths and the overall size controls the shot noise heating rate relative to the rotational frequency. For a near spherical nanoparticle, the effective heating rate for the rotational degrees of freedom is smaller than that for translation suggesting that the librational ground state may be easier to achieve than the vibrational ground state.
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Synthesis and evaluation of rare-earth doped glasses and crystals for optical refrigeration
NASA Astrophysics Data System (ADS)
Patterson, Wendy
This research focused on developing and characterizing rare-earth doped, solid-state materials for laser cooling. In particular, the work targeted the optimization of the lasercooling efficiency in Yb3+ and Tm3+ doped fluorides. The first instance of laser-induced cooling in a Tm3+-doped crystal, BaY2F8 was reported. Cooling by 3 degrees Kelvin below ambient temperature was obtained in a single-pass pump geometry at lambda = 1855 nm. Protocols were developed for materials synthesis and purification which can be applied to each component of ZBLANI:Yb 3+/Tm3+ (ZrF4 -- BaF2 -- LaF3 -- AlF3 -- NaF -- InF3: YbF3/TmF3) glass to enable a material with significantly reduced transition-metal impurities. A method for OH- impurity removal and ultra-drying of the metal fluorides was also improved upon. Several characterization tools were used to quantitatively and qualitatively verify purity, including inductively-coupled plasma mass spectrometry (ICP-MS). Here we found a more than 600-fold reduction in transition-metal impurities in a ZrCl2O solution. A non-contact spectroscopic technique for the measurement of laser-induced temperature changes in solids was developed. Two-band differential luminescence thermometry (TBDLT) achieved a sensitivity of ˜7 mK and enabled precise measurement of the zero-crossing temperature and net quantum efficiency. Several Yb3+-doped ZBLANI glasses fabricated from precursors of varying purity and by different processes were analyzed in detail by TBDLT. Laser-induced cooling was observed at room temperature for several of the materials. A net quantum efficiency of 97.39+/-0.01% at 238 K was found for the best ZBLANI:1%Yb 3+ laser-cooling sample produced from purified metal-fluoride precursors, and proved competitive with the best commercially procured material. The TBDLT technique enabled rapid and sensitive benchmarking of laser-cooling materials and provided critical feedback to the development and optimization of high-performance optical cryocooler materials. Also presented is an efficient and numerically stable method to calculate time-dependent, laser-induced temperature distributions in solids, including a detailed description of the computational procedure and its implementation. The model accurately predicted the zero-crossing temperature, the net quantum efficiency, and the functional shape of the transients, based on input parameters such as luminescence spectra, dopant concentration, pump properties, and several well-characterized material properties.
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Green-diode-pumped femtosecond Ti:Sapphire laser with up to 450 mW average power.
Gürel, K; Wittwer, V J; Hoffmann, M; Saraceno, C J; Hakobyan, S; Resan, B; Rohrbacher, A; Weingarten, K; Schilt, S; Südmeyer, T
2015-11-16
We investigate power-scaling of green-diode-pumped Ti:Sapphire lasers in continuous-wave (CW) and mode-locked operation. In a first configuration with a total pump power of up to 2 W incident onto the crystal, we achieved a CW power of up to 440 mW and self-starting mode-locking with up to 200 mW average power in 68-fs pulses using semiconductor saturable absorber mirror (SESAM) as saturable absorber. In a second configuration with up to 3 W of pump power incident onto the crystal, we achieved up to 650 mW in CW operation and up to 450 mW in 58-fs pulses using Kerr-lens mode-locking (KLM). The shortest pulse duration was 39 fs, which was achieved at 350 mW average power using KLM. The mode-locked laser generates a pulse train at repetition rates around 400 MHz. No complex cooling system is required: neither the SESAM nor the Ti:Sapphire crystal is actively cooled, only air cooling is applied to the pump diodes using a small fan. Because of mass production for laser displays, we expect that prices for green laser diodes will become very favorable in the near future, opening the door for low-cost Ti:Sapphire lasers. This will be highly attractive for potential mass applications such as biomedical imaging and sensing.
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2017-01-01
The ability of short pulse laser ablation in liquids to produce clean colloidal nanoparticles and unusual surface morphology has been employed in a broad range of practical applications. In this paper, we report the results of large-scale molecular dynamics simulations aimed at revealing the key processes that control the surface morphology and nanoparticle size distributions by pulsed laser ablation in liquids. The simulations of bulk Ag targets irradiated in water are performed with an advanced computational model combining a coarse-grained representation of liquid environment and an atomistic description of laser interaction with metal targets. For the irradiation conditions that correspond to the spallation regime in vacuum, the simulations predict that the water environment can prevent the complete separation of the spalled layer from the target, leading to the formation of large subsurface voids stabilized by rapid cooling and solidification. The subsequent irradiation of the laser-modified surface is found to result in a more efficient ablation and nanoparticle generation, thus suggesting the possibility of the incubation effect in multipulse laser ablation in liquids. The simulations performed at higher laser fluences that correspond to the phase explosion regime in vacuum reveal the accumulation of the ablation plume at the interface with the water environment and the formation of a hot metal layer. The water in contact with the metal layer is brought to the supercritical state and provides an environment suitable for nucleation and growth of small metal nanoparticles from metal atoms emitted from the hot metal layer. The metal layer itself has limited stability and can readily disintegrate into large (tens of nanometers) nanoparticles. The layer disintegration is facilitated by the Rayleigh–Taylor instability of the interface between the higher density metal layer decelerated by the pressure from the lighter supercritical water. The nanoparticles emerging from the layer disintegration are rapidly cooled and solidified due to the interaction with water environment, with a cooling rate of ∼2 × 1012 K/s observed in the simulations. The computational prediction of two distinct mechanisms of nanoparticle formation yielding nanoparticles with different characteristic sizes provides a plausible explanation for the experimental observations of bimodal nanoparticle size distributions in laser ablation in liquids. The ultrahigh cooling and solidification rates suggest the possibility for generation of nanoparticles featuring metastable phases and highly nonequilibrium structures. PMID:28798858
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Ibrahimi, Omar A; Kilmer, Suzanne L
2012-06-01
The long-pulsed diode (800-810-nm) laser is one of the most commonly used and effective lasers for hair removal. Limitations of currently available devices include a small treatment spot size, treatment-associated pain, and the need for skin cooling. To evaluate the long-term hair reduction capabilities of a long-pulsed diode laser with a large spot size and vacuum assisted suction. Thirty-five subjects were enrolled in a prospective, self-controlled, single-center study of axillary hair removal. The study consisted of three treatments using a long-pulsed diode laser with a large spot size and vacuum-assisted suction at 4- to 6-week intervals with follow-up visits 6 and 15 months after the last treatment. Hair clearance was quantified using macro hair-count photographs taken at baseline and at 6- and 15-month follow-up visits. Changes in hair thickness and color, levels of treatment-associated pain, and adverse events were additional study endpoints. There was statistically significant hair clearance at the 6 (54%) and 15-month (42%) follow-up visits. Remaining hairs were thinner and lighter at the 15-month follow-up visit, and the majority of subjects reported feeling up to mild to moderate pain during treatment without the use of pretreatment anesthesia or skin cooling. A long-pulsed diode laser with a large spot size and vacuum-assisted suction is safe and effective for long-term hair removal. This is the largest prospective study to evaluate long-term hair removal and the first to quantify decreases in hair thickness and darkness with treatment. © 2012 by the American Society for Dermatologic Surgery, Inc. Published by Wiley Periodicals, Inc.
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Application of Laser Treatment for Hardening Parts of Gas Turbine Engines from Titanium Alloys
NASA Astrophysics Data System (ADS)
Girzhon, V. V.; Ovchinnikov, A. V.
2017-03-01
X-ray diffraction analysis and light microscopy are used to study the structure of surface layers of helically extruded specimens of titanium alloy VT25U after laser fusion of the surface. It is shown that the rates of cooling of the melt promote formation of a martensitic α″-phase in the zone of laser fusion and of a submicrocrystalline microstructure. The microhardness in the zone of fusion of the initial specimens exceeds the microhardness of the specimens after the extrusion.
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Cooling options for high-average-power laser mirrors
NASA Astrophysics Data System (ADS)
Vojna, D.; Slezak, O.; Lucianetti, A.; Mocek, T.
2015-01-01
Thermally-induced deformations of steering mirrors reflecting 100 J/10 Hz laser pulses in vacuum have been analyzed. This deformation is caused by the thermal stress arisen due to parasitic absorption of 1 kW square-shaped flat-top laser beam in the dielectric multi-layer structure. Deformation depends on amount of absorbed power and geometry of the mirror as well as on the heat removal scheme. In our calculations, the following percentages of absorption of the incident power have been used: 1%, 0.5% and 0.1%. The absorbed power has been considered to be much higher than that expected in reality to assess the worst case scenario. Rectangular and circular mirrors made of zerodur (low thermal expansion glass) were considered for these simulations. The effect of coating layers on induced deformations has been neglected. Induced deformation of the mirror surface can significantly degrade the quality of the laser beam in the beam delivery system. Therefore, the proper design of the cooling scheme for the mirror in order to minimize the deformations is needed. Three possible cooling schemes of the mirror have been investigated. The first one takes advantage of a radiation cooling of the mirror and a copper heatsink fixed to the rear face of the mirror, the second scheme is based on additional heat conduction provided by flexible copper wires connected to the mirror holder, and the last scheme combines two above mentioned methods.
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Water-cooled hard-soldered kilowatt laser diode arrays operating at high duty cycle
NASA Astrophysics Data System (ADS)
Klumel, Genady; Karni, Yoram; Oppenhaim, Jacob; Berk, Yuri; Shamay, Moshe; Tessler, Renana; Cohen, Shalom; Risemberg, Shlomo
2010-04-01
High brightness laser diode arrays are increasingly found in defense applications either as efficient optical pumps or as direct energy sources. In many instances, duty cycles of 10- 20 % are required, together with precise optical collimation. System requirements are not always compatible with the use of microchannel based cooling, notwithstanding their remarkable efficiency. Simpler but effective solutions, which will not involve high fluid pressure drops as well as deionized water, are needed. The designer is faced with a number of challenges: effective heat removal, minimization of the built- in and operational stresses as well as precise and accurate fast axis collimation. In this article, we report on a novel laser diode array which includes an integral tap water cooling system. Robustness is achieved by all around hard solder bonding of passivated 940nm laser bars. Far field mapping of the beam, after accurate fast axis collimation will be presented. It will be shown that the design of water cooling channels , proper selection of package materials, careful design of fatigue sensitive parts and active collimation technique allow for long life time and reliability, while not compromising the laser diode array efficiency, optical power density ,brightness and compactness. Main performance characteristics are 150W/bar peak optical power, 10% duty cycle and more than 50% wall plug efficiency with less than 1° fast axis divergence. Lifetime of 0.5 Gshots with less than 10% power degradation has been proved. Additionally, the devices have successfully survived harsh environmental conditions such as thermal cycling of the coolant temperature and mechanical shocks.
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Potentialities of a new sigma(+)-sigma(-)laser configuration for radiative cooling and trapping
NASA Astrophysics Data System (ADS)
Dalibard, J.; Reynaud, S.; Cohen-Tannoudji, C.
1984-11-01
In the process of cooling and trapping neutral atoms, a new laser configuration is investigated which consists of two counterpropagating laser beams with orthogonal sigma(+) and sigma(-)polarizations. It is shown that such a configuration looks more promising than an ordinary standing wave (where the two counterpropagating waves have the same polarization), and this result is explained as being due to angular momentum conservation which prevents any coherent redistribution of photons between the two waves. The present conclusions are based on a quantitative calculation of the various parameters (potential depth, friction coefficient, diffusion coefficient) describing the mean value and the fluctuations of the radiative forces experienced, in such a laser configuration, by an atom with a J = 0 ground state and a J = 1 excited state.
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160mJ and 9ns electro-optics Q-switched conductively cooled 1047nm Nd:YLF laser
NASA Astrophysics Data System (ADS)
Yang, Qi; Ma, Jian; Lu, Tingting; Ma, Xiuhua; Zhu, Xiaolei
2015-02-01
A compact diode side-pumped conductively cooled 1047 nm Nd:YLF slab laser with high energy and short pulse width is developed. Through ray tracing method, we design a home-made pump module to homogenize the pump intensity. Based on the Possion equation, a thermal conduct model of side-pump laser is established. The temperature distribution in laser crystal is obtained, and the thermal lens is caculated. With the absorbed pump energy of 818 mJ, the maximum output energy of 228 mJ is achieved in free-running mode. At a repetition rate of 50 Hz, 160 mJ, 9 ns 1047 nm infrared light is obtained under the maximum absorbed pump energy, and the slope efficiency is 27.8%.
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Continuous-wave, single-frequency 229 nm laser source for laser cooling of cadmium atoms.
Kaneda, Yushi; Yarborough, J M; Merzlyak, Yevgeny; Yamaguchi, Atsushi; Hayashida, Keitaro; Ohmae, Noriaki; Katori, Hidetoshi
2016-02-15
Continuous-wave output at 229 nm for the application of laser cooling of Cd atoms was generated by the fourth harmonic using two successive second-harmonic generation stages. Employing a single-frequency optically pumped semiconductor laser as a fundamental source, 0.56 W of output at 229 nm was observed with a 10-mm long, Brewster-cut BBO crystal in an external cavity with 1.62 W of 458 nm input. Conversion efficiency from 458 nm to 229 nm was more than 34%. By applying a tapered amplifier (TA) as a fundamental source, we demonstrated magneto-optical trapping of all stable Cd isotopes including isotopes Cd111 and Cd113, which are applicable to optical lattice clocks.
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Understanding Molecular-Ion Neutral Atom Collisions for the Production of Ultracold Molecular Ions
2014-02-03
SECURITY CLASSIFICATION OF: This project was superseded and replaced by another ARO-funded project of the same name, which is still continuing. The goal...cooled atoms," IOTA -COST Workshop on molecular ions, Arosa, Switzerland. 5. E.R. Hudson, "Sympathetic cooling of molecules with laser cooled
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NASA Astrophysics Data System (ADS)
Wang, W. J.; Yung, K. C.; Choy, H. S.; Xiao, T. Y.; Cai, Z. X.
2018-06-01
Laser polishing of 3D printed metal components has drawn great interest in view of its potential applications in the dental implant industries. In this study, corrosion resistance, surface composition and crystalline structure of CoCr alloys were investigated. The corrosion resistance, micromorphology, composition, phase transformations and crystalline structures of samples were characterized using an electrochemical analyzer, scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and transmission electron microscope (TEM), respectively. The results indicate that high laser powers and low object distances within a certain range can facilitate the formation of complex oxide films, which exhibits high corrosion resistance. Further, object distances have a significant influence on cooling rates during the solidification of the melt pool in laser polishing, and fast cooling generates vast amounts of vacancies and defects, which result in the crystalline phase transformation from γ to ε. Consequently, the formed oxides play an important role in corrosion resistance on the outer layer, and inner layer with γ phase also helps keep the CoCr alloys in a stable structure with high resistant to corrosion. The two process parameters in laser polishing, laser power and object distances, are demonstrated as being important for controlling the surface microstructures and corrosion resistance of the additive manufactured CoCr alloy components.
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Feedback-controlled radiation pressure cooling
NASA Astrophysics Data System (ADS)
Prior, Yehiam; Vilensky, Mark; Averbukh, Ilya Sh.
2008-03-01
We propose a new approach to laser cooling of micromechanical devices, which is based on the phenomenon of optical bistability. These devices are modeled as a Fabry-Perot resonator with one fixed and one oscillating mirror. The bistability may be induced by an external feedback loop. When excited by an external laser, the cavity field has two co-existing stable steady-states depending on the position of the moving mirror. If the latter moves slow enough, the field in the cavity adjusts itself adiabatically to the mirror's instantaneous position. The mirror experiences radiation pressure corresponding to the intensity value. A sharp transition between two values of the radiation pressure force happens twice per every period of the mirror oscillation at non-equivalent positions (hysteresis effect), which leads to a non-zero net energy loss. The cooling mechanism resembles Sisyphus cooling in which the cavity mode performs sudden transitions between two stable states. We provide a dynamical stability analysis of the coupled moving mirror -- cavity field system, and find the parameters for efficient cooling. Direct numerical simulations show that a bistable cavity provides much more efficient cooling compared to the regular one.
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A 1J LD pumped Nd:YAG pulsed laser system
NASA Astrophysics Data System (ADS)
Yi, Xue-bin; Wang, Bin; Yang, Feng; Li, Jing; Liu, Ya-Ping; Li, Hui-Jun; Wang, Yu; Chen, Ren
2017-11-01
A 1J LD pumped Nd;YAG pulsed laser was designed. The laser uses an oscillation and two-staged amplification structure, and applies diode bar integrated array as side-pump. The TEC temperature control device combing liquid cooling system is organized to control the temperature of the laser system. This study also analyzed the theoretical threshold of working material, the effect of thermal lens and the basic principle of laser amplification. The results showed that the laser system can achieve 1J, 25Hz pulse laser output, and the laser pulse can be output at two width: 6-7ns and 10ns, respectively, and the original beam angle is 1.2mrad. The laser system is characterized by small size, light weight, as well as good stability, which make it being applied in varied fields such as photovoltaic radar platform and etc
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Laser induced bubbles inside liquids: Transient optical properties and effects on a beam propagation
NASA Astrophysics Data System (ADS)
Lazic, V.; Jovicevic, S.; Carpanese, M.
2012-07-01
Light transmission through a laser formed bubble (LFB) following ablation of a metallic target inside water was studied. During the early expansion and late collapsing phases, the refraction index nb of the hot high-pressure vapor bubble is higher than 1.23 and close to that of the surrounding liquid. The cavity growth lowers nb down to 1.00 and causes strong defocusing of the incident laser beam with consequent enlargement of the ablation crater diameter, here overcoming factor two. Inhomogeneous water vapor clustering inside the cool expanded bubble further perturbs the light transmission and induces irregular ablation by the successive laser pulse.
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The Microstructure Evolution of a Fe₃Al Alloy during the LENS Process.
Karczewski, Krzysztof; Durejko, Tomasz; Czujko, Tomasz
2018-03-07
A Fe₃Al intermetallic alloy has been successfully prepared by the laser-engineered net shaping (LENS) process. The applied process parameters were selected to provide various cooling rates during the solidification of the laser-melted material. The macro- and microstructure and the micro- and macrotexture of Fe₃Al samples were investigated. The influence of the cooling rate on grain morphology and texture is discussed. For the applied cooling rate range of 0.64 × 10⁴ K/s-2.6 × 10⁴ K/s, the structure is characterized by the presence of columnar grains for which the growth is directed upwards from the substrate. The intensity of the microtexture varies with the height of the sample and the cooling rate. The intensity of the texture increases with the decrease in the cooling rate. The samples that were obtained with low and medium cooling rates are characterized by the well-developed <100> and <111> macrotextures. The Fe₃Al alloy that was produced with a high cooling rate did not show a specific texture, which is reflected in the fairly uniform distribution of the normalized density intensity. Only a very weak texture with a <100> type component was observed.
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3D thermal model of laser surface glazing for H13 tool steel
NASA Astrophysics Data System (ADS)
Kabir, I. R.; Yin, D.; Naher, S.
2017-10-01
In this work a three dimensional (3D) finite element model of laser surface glazing (LSG) process has been developed. The purpose of the 3D thermal model of LSG was to achieve maximum accuracy towards the predicted outcome for optimizing the process. A cylindrical geometry of 10mm diameter and 1mm length was used in ANSYS 15 software. Temperature distribution, depth of modified zone and cooling rates were analysed from the thermal model. Parametric study was carried out varying the laser power from 200W-300W with constant beam diameter and residence time which were 0.2mm and 0.15ms respectively. The maximum surface temperature 2554°K was obtained for power 300W and minimum surface temperature 1668°K for power 200W. Heating and cooling rates increased with increasing laser power. The depth of the laser modified zone attained for 300W power was 37.5µm and for 200W power was 30µm. No molten zone was observed at 200W power. Maximum surface temperatures obtained from 3D model increased 4% than 2D model presented in author's previous work. In order to verify simulation results an analytical solution of temperature distribution for laser surface modification was used. The surface temperature after heating was calculated for similar laser parameters which is 1689°K. The difference in maximum surface temperature is around 20.7°K between analytical and numerical analysis of LSG for power 200W.
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Underwood, Lance D; Norton, Ryan J; McKay, Ryan P; Mesnard, David R; Fraze, Jason D; Zediker, Mark S; Faircloth, Brian O
2014-01-14
There is provided for laser bottom hole assembly for providing a high power laser beam having greater than 5 kW of power for a laser mechanical drilling process to advance a borehole. This assembly utilizes a reverse Moineau motor type power section and provides a self-regulating system that addresses fluid flows relating to motive force, cooling and removal of cuttings.
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Flow tube used to cool solar-pumped laser
NASA Technical Reports Server (NTRS)
1968-01-01
A flow tube has been designed and constructed to provide two major functions in the application of a laser beam for transmission of both sound and video. It maintains the YAG laser at the proper operating temperature of 300 degrees K under solar pumping conditions, and it serves as a pump cavity for the laser crystal.
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Changes in type I collagen following laser welding.
Bass, L S; Moazami, N; Pocsidio, J; Oz, M C; LoGerfo, P; Treat, M R
1992-01-01
Selection of ideal laser parameters for tissue welding is inhibited by poor understanding of the mechanism. We investigated structural changes in collagen molecules extracted from rat tail tendon (> 90% type I collagen) after tissue welding using an 808 nm diode laser and indocyanine green dye applied to the weld site. Mobility patterns on SDS-PAGE were identical in the lasered and untreated tendon extracts with urea or acetic acid. Pepsin incubation after acetic acid extraction revealed a reduction of collagen alpha and beta bands in lasered compared with untreated specimens. Circular dichroism studies of rat tail tendon showed absence of helical structure in collagen from lasered tendon. No evidence for covalent bonding was present in laser-treated tissues. Collagen molecules are denatured by the laser wavelength and parameters used in this study. No significant amount of helical structure is regenerated on cooling. We conclude that non-covalent interactions between denatured collagen molecules may be responsible for the creation of tissue welding.
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Laser cooling of molecules by zero-velocity selection and single spontaneous emission
DOE Office of Scientific and Technical Information (OSTI.GOV)
Ooi, C. H. Raymond
2010-11-15
A laser-cooling scheme for molecules is presented based on repeated cycle of zero-velocity selection, deceleration, and irreversible accumulation. Although this scheme also employs a single spontaneous emission as in [Raymond Ooi, Marzlin, and Audretsch, Eur. Phys. J. D 22, 259 (2003)], in order to circumvent the difficulty of maintaining closed pumping cycles in molecules, there are two distinct features which make the cooling process of this scheme faster and more practical. First, the zero-velocity selection creates a narrow velocity-width population with zero mean velocity, such that no further deceleration (with many stimulated Raman adiabatic passage (STIRAP) pulses) is required. Second,more » only two STIRAP processes are required to decelerate the remaining hot molecular ensemble to create a finite population around zero velocity for the next cycle. We present a setup to realize the cooling process in one dimension with trapping in the other two dimensions using a Stark barrel. Numerical estimates of the cooling parameters and simulations with density matrix equations using OH molecules show the applicability of the cooling scheme. For a gas at temperature T=1 K, the estimated cooling time is only 2 ms, with phase-space density increased by about 30 times. The possibility of extension to three-dimensional cooling via thermalization is also discussed.« less
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SBIR Grant:No-Vibration Agile Cryogenic Optical Refrigerator
DOE Office of Scientific and Technical Information (OSTI.GOV)
Epstein, Richard
2013-04-09
Optical refrigeration is currently the only all-solid-state cryocooling technology that has been demonstrated. Optical cryocoolers are devices that use laser light to cool small crystal or glass cooling elements. The cooling element absorbs the laser light and reradiates it at higher energy, an example of anti-Stokes fluorescence. The dif-ference between the energy of the outgoing and incoming light comes from the thermal energy of the cooling element, which in turn becomes colder. Entitled No-Vibration Agile Cryocoolers using Optical Refrigeration, this Phase I proposal directly addressed the continued development of the optical refrigerator components necessary to transition this scientific breakthrough intomore » National Nu-clear Security Administration (NNSA) sensor applications in line with the objectives of topic 50b. ThermoDynamic Films LLC (TDF), in collaboration with the University of New Mexico (UNM), cooled an optical-refrigerator cooling element comprised of an ytterbium-doped yttrium lithium fluoride (Yb:YLF) crystal from room tempera-ture to 123 K with about 2% efficiency. This is the world record in optical refrigera-tion and an important step toward revolutionizing cryogenic systems for sensor ap-plications. During this period, they also designed and analyzed the crucial elements of a prototype optical refrigerator including the thermal link that connects the cool-ing element with the load.« less
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The effect of prazosin on skin microcirculation as assessed by laser Doppler flowmetry.
Khan, F; Struthers, A D; Spence, V A
1988-01-01
1. Laser Doppler flowmetry was used in six normal volunteers to record changes in fingertip skin blood flow after the administration of prazosin to block postsynaptic alpha 1-adrenoceptors. 2. Prazosin (0.5 mg orally) did not alter systolic or diastolic blood pressure or heart rate. 3. Prazosin did significantly increase basal skin blood flow 2 h after its administration but this effect was no longer evident after contralateral hand warming. Prazosin markedly reduced the skin vasoconstrictor response to deep inspiration and to contralateral hand cooling. 4. This study suggests that postsynaptic alpha 1-adrenoceptors are involved in maintaining skin vasoconstrictor tone at rest and are also involved in the rapid skin vasoconstriction seen in response to a deep inspiration and to contralateral hand cooling. PMID:2846022
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Theoretical modeling on the laser-induced phase deformation of liquid crystal optical phased shifter
NASA Astrophysics Data System (ADS)
Zhou, Zhuangqi; Wang, Xiangru; Zhuo, Rusheng; He, Xiaoxian; Wu, Liang; Wang, Xiaolin; Tan, Qinggui; Qiu, Qi
2018-03-01
To improve the working condition of liquid crystal phase shifter on incident laser power, a theoretical model on laser induced phase distortion is built on the physics of heat deposition and heat transfer. Four typical factors (absorption, heat sink structure, cooling fluid rate, and substrate) are analyzed to evaluate the influence of phase distortion when a relative high-power laser is pumped into the liquid crystal phase shifter. Flow rate of cooling fluid and heat sink structure are the most important two factors on improving the limit of incident laser power. Meanwhile, silicon wafer is suggested to replace the back glass contacting the heat sink, because of its higher heat transfer coefficient. If the device is fabricated on the conditions that: the total absorption is 5% and it has a strong heat sink structure with a flow rate of 0.01 m/s, when the incident laser power is 110W, the laser-induced phase deformation on the center is diminished to be less than 0.06, and the maximum temperature increase on the center is less than 1K degree.
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Ultrafast giant magnetic cooling effect in ferromagnetic Co/Pt multilayers.
Shim, Je-Ho; Ali Syed, Akbar; Kim, Chul-Hoon; Lee, Kyung Min; Park, Seung-Young; Jeong, Jong-Ryul; Kim, Dong-Hyun; Eon Kim, Dong
2017-10-06
The magnetic cooling effect originates from a large change in entropy by the forced magnetization alignment, which has long been considered to be utilized as an alternative environment-friendly cooling technology compared to conventional refrigeration. However, an ultimate timescale of the magnetic cooling effect has never been studied yet. Here, we report that a giant magnetic cooling (up to 200 K) phenomenon exists in the Co/Pt nano-multilayers on a femtosecond timescale during the photoinduced demagnetization and remagnetization, where the disordered spins are more rapidly aligned, and thus magnetically cooled, by the external magnetic field via the lattice-spin interaction in the multilayer system. These findings were obtained by the extensive analysis of time-resolved magneto-optical responses with systematic variation of laser fluence as well as external field strength and direction. Ultrafast giant magnetic cooling observed in the present study can enable a new avenue to the realization of ultrafast magnetic devices.The forced alignment of magnetic moments leads to a large change in entropy, which can be used to reduce the temperature of a material. Here, the authors show that this magnetic cooling effect occurs on a femtosecond time scale in cobalt-platinum nano-multilayers.
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Evaluating the Field Emission Characteristics of Aluminum for DC High Voltage Photo-Electron Guns
NASA Astrophysics Data System (ADS)
Taus, Rhys; Poelker, Matthew; Forman, Eric; Mamun, Abdullah
2014-03-01
High current photoguns require high power laser light, but only a small portion of the laser light illuminating the photocathode produces electron beam. Most of the laser light (~ 65%) simply serves to heat the photocathode, which leads to evaporation of the chemicals required to create the negative electron affinity condition necessary for photoemission. Photocathode cooling techniques have been employed to address this problem, but active cooling of the photocathode is complicated because the cooling apparatus must float at high voltage. This work evaluates the field emission characteristics of cathode electrodes manufactured from materials with high thermal conductivity: aluminum and copper. These electrodes could serve as effective heat sinks, to passively cool the photocathode that resides within such a structure. However, literature suggests ``soft'' materials like aluminum and copper are ill suited for photogun applications, due to excessive field emission when biased at high voltage. This work provides an evaluation of aluminum and copper electrodes inside a high voltage field emission test stand, before and after coating with titanium nitride (TiN), a coating that enhances surface hardness. National Science Foundation Award Number: 1062320 and the Department of Defence ASSURE program.
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Thin-Film Evaporative Cooling for Side-Pumped Laser
NASA Technical Reports Server (NTRS)
Stewart, Brian K. (Inventor)
2010-01-01
A system and method are provided for cooling a crystal rod of a side-pumped laser. A transparent housing receives the crystal rod therethrough so that an annular gap is defined between the housing and the radial surface of the crystal rod. A fluid coolant is injected into the annular gap such the annular gap is partially filled with the fluid coolant while the radial surface of the crystal rod is wetted as a thin film all along the axial length thereof.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Biedermann, G. W.; McGuinness, H. J.; Rakholia, A. V.
Here, we demonstrate matter-wave interference in a warm vapor of rubidium atoms. Established approaches to light-pulse atom interferometry rely on laser cooling to concentrate a large ensemble of atoms into a velocity class resonant with the atom optical light pulse. In our experiment, we show that clear interference signals may be obtained without laser cooling. This effect relies on the Doppler selectivity of the atom interferometer resonance. Lastly, this interferometer may be configured to measure accelerations, and we demonstrate that multiple interferometers may be operated simultaneously by addressing multiple velocity classes.
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High sensitivity background absorption measurements in semiconductors
NASA Astrophysics Data System (ADS)
Giannini, Nathan; Silva, Junior R.; Wang, Chengao; Albrecht, Alexander R.; Melgaard, Seth D.; Sheik-Bahae, Mansoor
2015-03-01
Laser cooling in InGaP|GaAs double heterostructures (DHS) has been a sought after goal. Even though very high external quantum efficiency (EQE) has been achieved, background absorption has remained a bottleneck in achieving net cooling. The purpose of this study is to gain more insight into the source of the background absorption for InGaP|GaAs DHS as well as GaAs|AlGaAs DBRs by employing an excite-probe thermal Z-scan measurement.
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Methodology for estimation of time-dependent surface heat flux due to cryogen spray cooling.
Tunnell, James W; Torres, Jorge H; Anvari, Bahman
2002-01-01
Cryogen spray cooling (CSC) is an effective technique to protect the epidermis during cutaneous laser therapies. Spraying a cryogen onto the skin surface creates a time-varying heat flux, effectively cooling the skin during and following the cryogen spurt. In previous studies mathematical models were developed to predict the human skin temperature profiles during the cryogen spraying time. However, no studies have accounted for the additional cooling due to residual cryogen left on the skin surface following the spurt termination. We formulate and solve an inverse heat conduction (IHC) problem to predict the time-varying surface heat flux both during and following a cryogen spurt. The IHC formulation uses measured temperature profiles from within a medium to estimate the surface heat flux. We implement a one-dimensional sequential function specification method (SFSM) to estimate the surface heat flux from internal temperatures measured within an in vitro model in response to a cryogen spurt. Solution accuracy and experimental errors are examined using simulated temperature data. Heat flux following spurt termination appears substantial; however, it is less than that during the spraying time. The estimated time-varying heat flux can subsequently be used in forward heat conduction models to estimate temperature profiles in skin during and following a cryogen spurt and predict appropriate timing for onset of the laser pulse.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Xu, Yuntao; Dibble, Collin J.; Petrik, Nikolay G.
2016-04-26
A pulsed laser heating system has been developed that enables investigations of the dynamics and kinetics of nanoscale liquid films and liquid/solid interfaces on the nanosecond timescale in ultrahigh vacuum (UHV). Details of the design, implementation and characterization of a nanosecond pulsed laser system for transiently heating nanoscale films are described. Nanosecond pulses from a Nd:YAG laser are used to rapidly heat thin films of adsorbed water or other volatile materials on a clean, well-characterized Pt(111) crystal in UHV. Heating rates of ~1010 K/s for temperature increases of ~100 – 200 K are obtained. Subsequent rapid cooling (~5 × 109more » K/s) quenches the film, permitting in-situ, post-mortem analysis using a variety of surface science techniques. Lateral variations in the laser pulse energy are ~ ± 3% leading to a temperature uncertainty of ~ ± 5 K for a temperature jump of 200 K. Initial experiments with the apparatus demonstrate that crystalline ice films initially held at 90 K can be rapidly transformed into liquid water films with T > 273 K. No discernable recrystallization occurs during the rapid cooling back to cryogenic temperatures. In contrast, amorphous solid water films heated below the melting point rapidly crystallize. The nanosecond pulsed laser heating system can prepare nanoscale liquid and supercooled liquid films that persist for nanoseconds per heat pulse in an UHV environment, enabling experimental studies of a wide range of phenomena in liquids and at liquid/solid interfaces.« less
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Slot, Dagmar E; Timmerman, Mark F; Versteeg, Paula A; van der Velden, Ubele; van der Weijden, Fridus A
2012-12-01
Various laser systems are currently available for intra-oral use. Neodymium:Yttrium-Aluminium Garnet lasers(Nd:YAG) have been approved by the US Food and Drug Administration for soft tissue treatment in the oral cavity. The aim of this study was to test whether the use of a water-cooled Nd:YAG laser during a maintenance care programme as an adjunct to supragingival and subgingival debridement (scaling and root planing, SRP) with hand and ultrasonic instruments results in clinical improvement compared with SRP alone. This study was an examiner-blind, randomized and controlled clinical trial using a split-mouth design. Thirty subjects were selected, originally diagnosed with moderate to severe generalized periodontitis, following a periodontal maintenance care programme (PMC). Immediately after SRP in two randomly assigned contra-lateral quadrants, all pockets ≥5 mm were additionally treated with a Nd:YAG laser (1064 nm, 4W, 250-μsec pulse). Clinical assessments [probing pocket depth PPD, bleeding on pocket probing (BOPP)] were performed pre-treatment and at 6 months. Based on these assessments, the periodontal inflamed surface area (PISA) was calculated. At 6 months, the clinical parameters had significantly improved for both regimens. No statistically significant differences between treatment modalities were observed for PPD and BOPP scores at any time. PISA scores supported these findings. In residual pockets ≥5 mm, treated in a PMC, the adjunctive use of an Nd:YAG laser does not provide a clinically significant additional advantage. © 2012 John Wiley & Sons A/S.
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Xu, Yuntao; Dibble, Collin J; Petrik, Nikolay G; Smith, R Scott; Joly, Alan G; Tonkyn, Russell G; Kay, Bruce D; Kimmel, Greg A
2016-04-28
A pulsed laser heating system has been developed that enables investigations of the dynamics and kinetics of nanoscale liquid films and liquid/solid interfaces on the nanosecond time scale in ultrahigh vacuum (UHV). Details of the design, implementation, and characterization of a nanosecond pulsed laser system for transiently heating nanoscale films are described. Nanosecond pulses from a Nd:YAG laser are used to rapidly heat thin films of adsorbed water or other volatile materials on a clean, well-characterized Pt(111) crystal in UHV. Heating rates of ∼10(10) K/s for temperature increases of ∼100-200 K are obtained. Subsequent rapid cooling (∼5 × 10(9) K/s) quenches the film, permitting in-situ, post-heating analysis using a variety of surface science techniques. Lateral variations in the laser pulse energy are ∼±2.7% leading to a temperature uncertainty of ∼±4.4 K for a temperature jump of 200 K. Initial experiments with the apparatus demonstrate that crystalline ice films initially held at 90 K can be rapidly transformed into liquid water films with T > 273 K. No discernable recrystallization occurs during the rapid cooling back to cryogenic temperatures. In contrast, amorphous solid water films heated below the melting point rapidly crystallize. The nanosecond pulsed laser heating system can prepare nanoscale liquid and supercooled liquid films that persist for nanoseconds per heat pulse in an UHV environment, enabling experimental studies of a wide range of phenomena in liquids and at liquid/solid interfaces.
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Characterization of diode-laser stacks for high-energy-class solid state lasers
NASA Astrophysics Data System (ADS)
Pilar, Jan; Sikocinski, Pawel; Pranowicz, Alina; Divoky, Martin; Crump, P.; Staske, R.; Lucianetti, Antonio; Mocek, Tomas
2014-03-01
In this work, we present a comparative study of high power diode stacks produced by world's leading manufacturers such as DILAS, Jenoptik, and Quantel. The diode-laser stacks are characterized by central wavelength around 939 nm, duty cycle of 1 %, and maximum repetition rate of 10 Hz. The characterization includes peak power, electrical-to-optical efficiency, central wavelength and full width at half maximum (FWHM) as a function of diode current and cooling temperature. A cross-check of measurements performed at HiLASE-IoP and Ferdinand-Braun-Institut (FBH) shows very good agreement between the results. Our study reveals also the presence of discontinuities in the spectra of two diode stacks. We consider the results presented here a valuable tool to optimize pump sources for ultra-high average power lasers, including laser fusion facilities.
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A review of the physiological and histological effects of laser osteotomy.
Rajitha Gunaratne, G D; Khan, Riaz; Fick, Daniel; Robertson, Brett; Dahotre, Narendra; Ironside, Charlie
2017-01-01
Osteotomy is the surgical cutting of bone. Some obstacles to laser osteotomy have been melting, carbonisation and subsequent delayed healing. New cooled scanning techniques have resulted in effective bone cuts without the strong thermal side effects, which were observed by inappropriate irradiation techniques with continuous wave and long pulsed lasers. With these new techniques, osteotomy gaps histologically healed with new bone formation without any noticeable or minimum thermal damage. No significant cellular differences in bone healing between laser and mechanical osteotomies were noticed. Some studies even suggest that the healing rate may be enhanced following laser osteotomy compared to conventional mechanical osteotomy. Additional research is necessary to evaluate different laser types with appropriate laser setting variables to increase ablation rates, with control of depth, change in bone type and damage to adjacent soft tissue. Laser osteotomy has the potential to become incorporated into the armamentarium of bone surgery.
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Robust hard-solder packaging of conduction cooled laser diode bars
NASA Astrophysics Data System (ADS)
Schleuning, David; Griffin, Mike; James, Phillip; McNulty, John; Mendoza, Dan; Morales, John; Nabors, David; Peters, Mike; Zhou, Hailong; Reed, Murray
2007-02-01
We present the reliability of high-power laser diodes utilizing hard solder (AuSn) on a conduction-cooled package (HCCP). We present results of 50 W hard-pulse operation at 8xx nm and demonstrate a reliability of MTTF > 27 khrs (90% CL), which is an order of magnitude improvement over traditional packaging. We also present results at 9xx nm with a reliability of MTTF >17 khrs (90% CL) at 75 W. We discuss finite element analysis (FEA) modeling and time dependent temperature measurements combined with experimental life-test data to quantify true hard-pulse operation. We also discuss FEA and measured stress profiles across laser bars comparing soft and hard solder packaging.
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NASA Technical Reports Server (NTRS)
Snow, W. L.; Morris, O. A.
1984-01-01
Methods for increasing the radiant in light sheets used for vapor screen set-ups were investigated. Both high-pressure mercury arc lamps and lasers were considered. Pulsed operation of the air-cooled 1-kW lamps increased the light output but decreased reliability. An ellipsoidal mirror improved the output of the air-cooled lamps by concentrating the light but increased the complexity of the housing. Water-cooled-4-kW lamps coupled with high-aperture Fresnel lenses provided reasonable improvements over the air-cooled lamps. Fanned laser beams measurements of scattered light versus dew point made in conjunction with successful attempts to control the fluid injection. A number of smoke generators are described and test results comparing smoke and vapor screens are shown. Finally, one test included a periscope system to relay the image to a camera outside the flow.
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NASA Astrophysics Data System (ADS)
Wang, H. B.; Wen, W. Q.; Huang, Z. K.; Zhang, D. C.; Hai, B.; Zhu, X. L.; Zhao, D. M.; Yang, J.; Li, J.; Li, X. N.; Mao, L. J.; Mao, R. S.; Wu, J. X.; Yang, J. C.; Yuan, Y. J.; Eidam, L.; Winters, D.; Beck, T.; Kiefer, D.; Rein, B.; Walther, Th.; Loeser, M.; Schramm, U.; Siebold, M.; Bussmann, M.; Ma, X.
2017-10-01
We report on an experiment that was conducted in preparation of laser cooling experiments at the heavy-ion storage ring CSRe. The lifetimes of ion beams made up of 12C3+ and 16O4+ ions stored at an energy of 122 MeV/u in the CSRe were determined by two independent methods, firstly via a DC current transformer (DCCT) and secondly via a Schottky resonator. Using electron-cooling, the signals of the 12C3+ and 16O4+ ions could be separated and clearly observed in the Schottky spectrum. The obtained individual lifetimes of the 12C3+ and 16O4+ components were 23.6 s and 17.8 s, respectively. The proportion of 12C3+ ions in the stored ion beam was measured to be more than 70% at the beginning of the injection and increasing as a function of time. In addition to these measurements, the operation and remote control of a pulsed laser system placed directly next to the storage ring was tested in a setup similar to the one envisaged for future laser experiments.
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High-brightness line generators and fiber-coupled sources based on low-smile laser diode arrays
NASA Astrophysics Data System (ADS)
Watson, J.; Schleuning, D.; Lavikko, P.; Alander, T.; Lee, D.; Lovato, P.; Winhold, H.; Griffin, M.; Tolman, S.; Liang, P.; Hasenberg, T.; Reed, M.
2008-02-01
We describe the performance of diode laser bars mounted on conductive and water cooled platforms using low smile processes. Total smile of <1μm is readily achieved on both In and AuSn based platforms. Combined with environmentally robust lensing, these mounts form the basis of multiple, high-brightness products. Free-space-coupled devices utilizing conductively-cooled bars delivering 100W from a 200μm, 0.22NA fiber at 976nm have been developed for pumping fiber lasers, as well as for materials processing. Additionally, line generators for graphics and materials processing applications have been produced. Starting from single bars mounted on water-cooled packages that do not require de-ionized or pH-controlled water, these line generators deliver over 80W of power into a line with an aspect ratio of 600:1, and have a BPP of <2mm-mrad in the direction orthogonal to the line.
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Pulpal effects of enamel ablation with a microsecond pulsed lambda = 9.3-microm CO2 laser.
Staninec, Michal; Darling, Cynthia L; Goodis, Harold E; Pierre, Daniel; Cox, Darren P; Fan, Kenneth; Larson, Michael; Parisi, Renaldo; Hsu, Dennis; Manesh, Saman K; Ho, Chi; Hosseini, Mehran; Fried, Daniel
2009-04-01
In vitro studies have shown that CO2 lasers operating at the highly absorbed 9.3 and 9.6-microm wavelengths with a pulse duration in the range of 10-20-microsecond are well suited for the efficient ablation of enamel and dentin with minimal peripheral thermal damage. Even though these CO2 lasers are highly promising, they have yet to receive FDA approval. Clinical studies are necessary to determine if excessive heat deposition in the tooth may have any detrimental pulpal effects, particularly at higher ablative fluencies. The purpose of this study was to evaluate the pulpal safety of laser irradiation of tooth occlusal surfaces under the conditions required for small conservative preparations confined to enamel. Test subjects requiring removal of third molar teeth were recruited and teeth scheduled for extraction were irradiated using a pulsed CO2 laser at a wavelength of 9.3 microm operating at 25 or 50 Hz using a incident fluence of 20 J/cm(2) for a total of 3,000 laser pulses (36 J) for both rates with water cooling. Two control groups were used, one with no treatment and one with a small cut made with a conventional high-speed hand-piece. No anesthetic was used for any of the procedures and tooth vitality was evaluated prior to treatment by heat, cold and electrical testing. Short term effects were observed on teeth extracted within 72 hours after treatment and long term effects were observed on teeth extracted 90 days after treatment. The pulps of the teeth were fixed with formalin immediately after extraction and subjected to histological examination. Additionally, micro-thermocouple measurements were used to estimate the potential temperature rise in the pulp chamber of extracted teeth employing the same irradiation conditions used in vivo. Pulpal thermocouple measurements showed the internal temperature rise in the tooth was within safe limits, 3.3+/-1.4 degrees C without water cooling versus 1.7+/-1.6 degrees C with water-cooling, n = 25, P<0.05. None of the control or treatment groups showed any deleterious effects on pulpal tissues and none of the 29 test-subjects felt pain or discomfort after the procedure. Only two test-subjects felt discomfort from "cold sensitivity" during the procedure caused by the water-spray. It appears that this CO2 laser can ablate enamel safely without harming the pulp under the rate of energy deposition employed in this study.
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Improving confocal microscopy with solid-state semiconductor excitation sources
NASA Astrophysics Data System (ADS)
Sivers, Nelson L.
To efficiently excite the fluorescent dyes used in imaging biological samples with a confocal microscope, the wavelengths of the exciting laser must be near the fluorochrome absorption peak. However, this causes imaging problems when the fluorochrome absorption and emission spectra overlap significantly, i.e. have small Stokes shifts, which is the case for most fluorochromes that emit in the red to infrared. As a result, the reflected laser excitation cannot be distinguished from the information-containing fluorescence signal. However, cryogenically cooling the exciting laser diode enabled the laser emission wavelengths to be tuned to shorter wavelengths, decreasing the interference between the laser and the fluorochrome's fluorescence. This reduced the amount of reflected laser light in the confocal image. However, the cooled laser diode's shorter wavelength signal resulted in slightly less efficient fluorochrome excitation. Spectrophotometric analysis showed that as the laser diodes were cooled, their output power increased, which more than compensated for the lower fluorochrome excitation and resulted in significantly more intense fluorescence. Thus, by tuning the laser diode emission wavelengths away from the fluorescence signal, less reflected laser light and more fluorescence information reached the detector, creating images with better signal to noise ratios. Additionally, new, high, luminous flux, light-emitting diodes (LEDs) are now powerful enough to create confocal fluorescence signals comparable to those produced by the traditional laser excitation sources in fluorescence confocal microscopes. The broader LED spectral response effectively excited the fluorochrome, yet was spectrally limited enough for standard filter sets to separate the LED excitation from the fluorochrome fluorescence signal. Spectrophotometric analysis of the excitation and fluorescence spectra of several fluorochromes showed that high-powered, LED-induced fluorescence contained the same spectral information and could be more intense than that produced by lasers. An alternative, LED-based, confocal microscope is proposed in this thesis that would be capable of exciting multiple fluorochromes in a single specimen, producing images of several distinct cellular components simultaneously. The inexpensive, LED-based, confocal microscope would require lower peak excitation intensities to produce fluorescence signals equal to those produced by laser excitation, reducing cellular damage and slowing fluorochrome photobleaching.
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Kilowatt-level direct-'refractive index matching liquid'-cooled Nd:YLF thin disk laser resonator.
Ye, Zhibin; Liu, Chong; Tu, Bo; Wang, Ke; Gao, Qingsong; Tang, Chun; Cai, Zhen
2016-01-25
A direct-liquid-cooled Nd:YLF thin disk laser resonator is presented, which features the use of refractive index matching liquid (RIML) as coolant. Highly uniform pump intensity distribution with rectangular shape is realized by using metallic planar waveguides. Much attention has been paid on the design of the gain module, including how to achieve excellent cooling ability with multi-channel coolers and how to choose the doping levels of the crystals for realizing well-distributed pump absorption. The flow velocity of the coolant is found to be a key parameter for laser performance and optimized to keep it in laminar flow status for dissipating unwanted heat load. A single channel device is used to measure the convective heat transfer coefficient (CHTC) at different flow velocities. Accordingly, the thermal stress in the disk is analyzed numerically and the maximum permissible thermal load is estimated. Experimentally, with ten pieces of a-cut Nd:YLF thin disks of different doping levels, a linear polarized laser with an average output power of 1120 W is achieved at the pump power of 5202 W, corresponding to an optical-optical efficiency of 21.5%, and a slope efficiency of 30.8%. Furthermore, the wavefront aberration of the gain module is measured to be quite weak, with a peak to valley (PV) value of 4.0 μm when it is pumped at 5202 W, which enables the feasibility of its application in an unstable resonator. To the best of our knowledge, this is the first demonstration of kilowatt-level direct-'refractive index matching liquid'-cooled Nd:YLF thin disk laser resonator.
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NASA Astrophysics Data System (ADS)
Roth, B.; Koelemeij, J.; Daerr, H.; Ernsting, I.; Jorgensen, S.; Okhapkin, M.; Wicht, A.; Nevsky, A.; Schiller, S.
2017-11-01
Narrow ro-vibrational transitions in ultracold molecules are excellent candidates for frequency references in the near-IR to visible spectral domain and interesting systems for fundamental tests of physics, in particular for a satellite test of the gravitational redshift of clocks. We have performed laser spectroscopy of several ro-vibrational overtone transitions υ = 0 → υ = 4 in HD+ ions at around 1.4 μm. 1+1 REMPD was used as a detection method, followed by measurement of the number of remaining molecules. The molecular ions were stored in a linear radiofrequency trap and cooled to millikelvin temperatures, by sympathetic cooling using laser-cooled Be+ ions simultaneously stored in the same trap.
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A compact Nd:YAG DPSSL using diamond-cooled technology
NASA Astrophysics Data System (ADS)
Chou, Hsian P.; Wang, Yu-Lin; Hasson, Victor H.; Trainor, Daniel W.
2005-03-01
In our diamond-cooled approach, thin disks of laser gain material, e.g., Nd:YAG, are alternated between thin disks of single crystal synthetic diamond whose heat conductivity is over 2000 W/m-°K. The gain medium is face-pumped (along the optical axis) by the output of laser diode arrays. This optical configuration produces heat transfer from Nd:YAG to the diamond, in the direction of the optical axis, and then heat is rapidly conducted radially outward through the diamond to the cooling fluid circulating at the circumference of the diamond/YAG assembly. This geometry effectively removes the heat from the gain material in a manner that permits the attainment of high power output with excellent beam quality.
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NASA Astrophysics Data System (ADS)
Strohmaier, S. G.; Erbert, G.; Meissner-Schenk, A. H.; Lommel, M.; Schmidt, B.; Kaul, T.; Karow, M.; Crump, P.
2017-02-01
Progress will be presented on ongoing research into the development of ultra-high power and efficiency bars achieving significantly higher output power, conversion efficiency and brightness than currently commercially available. We combine advanced InAlGaAs/GaAs-based epitaxial structures and novel lateral designs, new materials and superior cooling architectures to enable improved performance. Specifically, we present progress in kilowatt-class 10-mm diode laser bars, where recent studies have demonstrated 880 W continuous wave output power from a 10 mm x 4 mm laser diode bar at 850 A of electrical current and 15°C water temperature. This laser achieves < 60% electro-optical efficiency at 880 W CW output power.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Hehlen, Markus Peter; Boncher, William Lawrence; Love, Steven Paul
The performance of a solid-state optical refrigerator is the result of a complex interplay of numerous optical and thermal parameters. We present a first preliminary study of an optical cryocooler using ray-tracing techniques. A numerical optimization identified a non-resonant cavity with astigmatism. This geometry offered more efficient pump absorption by the YLF:10%Yb laser-cooling crystal compared to non-resonant cavities without astigmatism that have been pursued experimentally so far. Ray tracing simulations indicate that ~80% of the incident pump light can absorbed for temperatures down to ~100 K. Calculations of heat loads, cooling power, and net payload heat lift are presented. Theymore » show that it is possible to cool a payload to a range of 90–100 K while producing a net payload heat lift of 80 mW and 300 mW when pumping a YLF:10%Yb crystal with 20 W and 50 W at 1020 nm, respectively. This performance is suited to cool HgCdTe infrared detectors that are used for sensing in the 8–12 μm atmospheric window. While the detector noise would be ~6× greater at 100 K than at 77 K, the laser refrigerator would introduce no vibrations and thus eliminate sources of microphonic noise that are limiting the performance of current systems.« less
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NASA Astrophysics Data System (ADS)
Hu, Meilong; Liu, Lu; Lv, Xuewei; Bai, Chenguang; Zhang, Shengfu
2014-01-01
The isothermal phase composition of high-titanium-bearing slag (23 mass pct TiO2) under an argon atmosphere during cooling process from 1723 K (1450 °C) was calculated by FactSage.6.3 (CRCT-ThermFact Inc., Montréal, Canada). Three main phases, which were perovskite, titania spinel, and clinopyroxene, could form during the cooling process and they precipitated at 1713 K, 1603 K, and 1498 K (1440 °C, 1330 °C, and 1225 °C), respectively. The nonisothermal crystallization process of perovskite in synthesized high-titanium-bearing slag was studied in situ by a confocal scanning laser microscope (CSLM) with cooling rate of 30 K/min. The results showed that the primary phase was perovskite that precipitated at 1703 K (1430 °C). The whole precipitation and growth process of perovskite was obtained, whereas other phases formed as glass under the current experimental conditions. Perovskite grew along a specific growth track and finally appeared with snowflake morphology. The growing kinetics of perovskite formation from molten slag were also mentioned.
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Mesoscale elucidation of laser-assisted chemical deposition of Sn nanostructured electrodes
NASA Astrophysics Data System (ADS)
Liu, Zhixiao; Deng, Biwei; Cheng, Gary J.; Deng, Huiqiu; Mukherjee, Partha P.
2015-06-01
Nanostructured tin (Sn) is a promising high-capacity electrode for improved performance in lithium-ion batteries for electric vehicles. In this work, Sn nanoisland growth for nanostructured electrodes assisted by the pulse laser irradiation has been investigated based on a mesoscale modeling formalism. The influence of pertinent processing conditions, such as pulse duration, heating/cooling rates, and atom flux, on the Sn nanostructure formation is specifically considered. The interaction between the adsorbed atom and the substrate, represented by the adatom diffusion barrier, is carefully studied. It is found that the diffusion barrier predominantly affects the distribution of Sn atoms. For both α-Sn and β-Sn, the averaged coordination number is larger than 3 when the diffusion barrier equals to 0.15 eV. The averaged coordination number decreases as the diffusion barrier increases. The substrate temperature, which is determined by heating/cooling rates and pulse duration, can also affect the formation of Sn nanoislands. For α-Sn, when applied low heating/cooling rates, nanoislands cannot form if the diffusion barrier is larger than 0.35 eV.
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Control of Hazards to Health From Laser Radiation
2006-01-01
compared to the calculated AEL. (2) Optically aided viewing. Viewing a laser beam with optical aids (other than ordinary eyeglasses or contact lenses ...resonant optical cavity. TB MED 524 8 b. Lenses , mirrors, cooling systems, shutters, and other accessories may be added to the system to obtain...procedures for laser optical systems (for example, mirrors, prisms, and lenses ) that employ Class 2 and Class 3a lasers, it is always good laser safety
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2002-12-01
surface temperature for a given heat flux [2]. Mudawar and Valentine conducted an experimental study of spray cooling to determine local quenching... Mudawar presented a CHF correlation with suitable dimensionless parameters that accurately predicted data for FC-72, FC-87 and water [5]. The 2...correlation by Estes and Mudawar had a strong dependence of CHF on volumetric flux and Sauter mean diameter. Sehmbey et al. developed a semiempirical
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Laser Cooling of 2-6 Semiconductors
2016-08-12
practical optical refrigeration . The challenge is the stoichiometric defect in bulk crystal which introduces mid-gap states that manifest as broad-band...cooling in semiconductor has stimulated strong interest in further scaling up towards practical optical refrigeration . The challenge is the...energy. The upconversion process is facilitated by the annihilation of phonons and leads to cooling of the matter. The concept of optical refrigeration
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Resolved Sideband Spectroscopy for the Detection of Weak Optical Transitions
2013-08-01
Lett. 81, 317 (1998). [12] T. Baba and I. Waki , “Cooling and Mass-Analysis of Molecules Using Laser-Cooled Atoms,” Jpn. J. Appl. Phys 35, L1134 (1996...fermions,” Phys. Rev. A: At. Mol. Opt. Phys. 65, 043601 (2002). [26] T. Baba and I. Waki , “Spectral shape of in situ mass spectra of sympathetically cooled
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A low cost hermetic packaging for high power industry fiber lasers
NASA Astrophysics Data System (ADS)
Ding, Jianwu; Liu, Jinhui
2018-02-01
For water-cooled fiber lasers, humidity and the resulting water-condensation has always been the biggest threat for laser reliability or power degradation, especially when used in harsh industrial environment. Here we present an innovative fiber laser packaging method featuring cast aluminum frame and an almost screw-free exterior packaging. A CW fiber laser with 1.5KW laser output power in such a compact and light-weight package has been demonstrated with an excellent beam quality and power stability for industry applications.
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NASA Technical Reports Server (NTRS)
1997-01-01
Microcosm, Inc. produced the portable Farfield-2 laser for field applications that require high power pulsed illumination. The compact design was conceived through research at Goddard Space Flight Center on laser instruments for space missions to carry out geoscience studies of Earth. An exclusive license to the key NASA patent for the compact laser design was assigned to Microcosm. The FarField-2 is ideal for field applications, has low power consumption, does not need water cooling or gas supplies, and produces nearly ideal beam quality. The properties of the laser also make it effective over long distances, which is one reason why NASA developed the technology for laser altimeters that can be toted aboard spacecraft. Applications for the FarField-2 include medicine, biology, and materials science and processing, as well as diamond marking, semiconductor line-cutting, chromosome surgery, and fluorescence microscopy.
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980-nm, 15-W cw laser diodes on F-mount-type heat sinks
DOE Office of Scientific and Technical Information (OSTI.GOV)
Bezotosnyi, V V; Krokhin, O N; Oleshchenko, V A
2015-12-31
We have studied the key optical emission parameters of laser diodes (emission wavelength, 980 nm; stripe contact width, 95 μm) mounted directly on F- and C-mount-type copper heat sinks, without intermediate elements (submounts). When effectively cooled by a thermoelectric microcooler, the lasers on the F-mount operated stably at output powers up to 20 W. The lasers were tested for reliable operation at an output power of 15 W for 100 h, and no decrease in output power was detected to within measurement accuracy. The experimentally determined maximum total efficiency is 71.7% and the efficiency at a nominal output power ofmore » 15 W is 61%. We compare parameters of the laser diodes mounted on C- and F-mounts and discuss the advantages of the F-mounts. (lasers)« less
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Current Pulses Momentarily Enhance Thermoelectric Cooling
NASA Technical Reports Server (NTRS)
Snyder, G. Jeffrey; Fleurial, Jean-Pierre; Caillat, Thierry; Chen, Gang; Yang, Rong Gui
2004-01-01
The rates of cooling afforded by thermoelectric (Peltier) devices can be increased for short times by applying pulses of electric current greater than the currents that yield maximum steady-state cooling. It has been proposed to utilize such momentary enhancements of cooling in applications in which diode lasers and other semiconductor devices are required to operate for times of the order of milliseconds at temperatures too low to be easily obtainable in the steady state. In a typical contemplated application, a semiconductor device would be in contact with the final (coldest) somewhat taller stage of a multistage thermoelectric cooler. Steady current would be applied to the stages to produce steady cooling. Pulsed current would then be applied, enhancing the cooling of the top stage momentarily. The principles of operation are straightforward: In a thermoelectric device, the cooling occurs only at a junction at one end of the thermoelectric legs, at a rate proportional to the applied current. However, Joule heating occurs throughout the device at a rate proportional to the current squared. Hence, in the steady state, the steady temperature difference that the device can sustain increases with current only to the point beyond which the Joule heating dominates. If a pulse of current greater than the optimum current (the current for maximum steady cooling) is applied, then the junction becomes momentarily cooled below its lowest steady temperature until thermal conduction brings the resulting pulse of Joule heat to the junction and thereby heats the junction above its lowest steady temperature. A theoretical and experimental study of such transient thermoelectric cooling followed by transient Joule heating in response to current pulses has been performed. The figure presents results from one of the experiments. The study established the essential parameters that characterize the pulse cooling effect, including the minimum temperature achieved, the maximum temperature overshoot, the time to reach minimum temperature, the time while cooled, and the time between pulses. It was found that at large pulse amplitude, the amount of pulse supercooling is about a fourth of the maximum steady-state temperature difference. For the particular thermoelectric device used in one set of the experiments, the practical optimum pulse amplitude was found to be about 3 times the optimum steady-state current. In a further experiment, a pulse cooler was integrated into a small commercial thermoelectric threestage cooler and found to provide several degrees of additional cooling for a time long enough to operate a semiconductor laser in a gas sensor.
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Experimental investigation on the spiral trepanning of K24 superalloy with femtosecond laser
NASA Astrophysics Data System (ADS)
Wang, Maolu; Yang, Lijun; Zhang, Shuai; Wang, Yang
2018-05-01
Film cooling holes are crucial for improving the performance of the aviation engine. In the paper, the processing of the film cooling holes on K24 superalloy by femtosecond laser is investigated. By comparing the three different drilling methods, the spiral trepanning method is chosen, and all the drilling experiments are carried out in this way. The experimental results show that the drilling of femtosecond laser pulses has distinct merits against that of the traditional long pulse laser, which can realize the "cold" processing with less recasting layer and less crack. The influence of each process parameter on roundness and taper, which are the important parameters to measure the quality of holes, is analyzed in detail, and the method to decrease it is proposed. To further reduce the recasting layer, the processing quality of the inner wall of the micro hole is investigated by scanning electron microscopy (SEM) equipped with energy disperse spectroscopy (EDS), the mechanism of the femtosecond laser interaction with K24 superalloy is further revealed. The investigation to the film hole machining by femtosecond laser has important practical significance.
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Awd, Mustafa; Tenkamp, Jochen; Hirtler, Markus; Siddique, Shafaqat; Bambach, Markus; Walther, Frank
2017-12-23
The second-generation aluminum-magnesium-scandium (Al-Mg-Sc) alloy, which is often referred to as Scalmalloy ® , has been developed as a high-strength aluminum alloy for selective laser melting (SLM). The high-cooling rates of melt pools during SLM establishes the thermodynamic conditions for a fine-grained crack-free aluminum structure saturated with fine precipitates of the ceramic phase Al₃-Sc. The precipitation allows tensile and fatigue strength of Scalmalloy ® to exceed those of AlSi10Mg by ~70%. Knowledge about properties of other additive manufacturing processes with slower cooling rates is currently not available. In this study, two batches of Scalmalloy ® processed by SLM and laser metal deposition (LMD) are compared regarding microstructure-induced properties. Microstructural strengthening mechanisms behind enhanced strength and ductility are investigated by scanning electron microscopy (SEM). Fatigue damage mechanisms in low-cycle (LCF) to high-cycle fatigue (HCF) are a subject of study in a combined strategy of experimental and statistical modeling for calculation of Woehler curves in the respective regimes. Modeling efforts are supported by non-destructive defect characterization in an X-ray computed tomography (µ-CT) platform. The investigations show that Scalmalloy ® specimens produced by LMD are prone to extensive porosity, contrary to SLM specimens, which is translated to ~30% lower fatigue strength.
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Awd, Mustafa; Tenkamp, Jochen; Hirtler, Markus; Siddique, Shafaqat; Bambach, Markus; Walther, Frank
2017-01-01
The second-generation aluminum-magnesium-scandium (Al-Mg-Sc) alloy, which is often referred to as Scalmalloy®, has been developed as a high-strength aluminum alloy for selective laser melting (SLM). The high-cooling rates of melt pools during SLM establishes the thermodynamic conditions for a fine-grained crack-free aluminum structure saturated with fine precipitates of the ceramic phase Al3-Sc. The precipitation allows tensile and fatigue strength of Scalmalloy® to exceed those of AlSi10Mg by ~70%. Knowledge about properties of other additive manufacturing processes with slower cooling rates is currently not available. In this study, two batches of Scalmalloy® processed by SLM and laser metal deposition (LMD) are compared regarding microstructure-induced properties. Microstructural strengthening mechanisms behind enhanced strength and ductility are investigated by scanning electron microscopy (SEM). Fatigue damage mechanisms in low-cycle (LCF) to high-cycle fatigue (HCF) are a subject of study in a combined strategy of experimental and statistical modeling for calculation of Woehler curves in the respective regimes. Modeling efforts are supported by non-destructive defect characterization in an X-ray computed tomography (µ-CT) platform. The investigations show that Scalmalloy® specimens produced by LMD are prone to extensive porosity, contrary to SLM specimens, which is translated to ~30% lower fatigue strength. PMID:29295528
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Efficient rotational cooling of Coulomb-crystallized molecular ions by a helium buffer gas.
Hansen, A K; Versolato, O O; Kłosowski, L; Kristensen, S B; Gingell, A; Schwarz, M; Windberger, A; Ullrich, J; López-Urrutia, J R Crespo; Drewsen, M
2014-04-03
The preparation of cold molecules is of great importance in many contexts, such as fundamental physics investigations, high-resolution spectroscopy of complex molecules, cold chemistry and astrochemistry. One versatile and widely applied method to cool molecules is helium buffer-gas cooling in either a supersonic beam expansion or a cryogenic trap environment. Another more recent method applicable to trapped molecular ions relies on sympathetic translational cooling, through collisional interactions with co-trapped, laser-cooled atomic ions, into spatially ordered structures called Coulomb crystals, combined with laser-controlled internal-state preparation. Here we present experimental results on helium buffer-gas cooling of the rotational degrees of freedom of MgH(+) molecular ions, which have been trapped and sympathetically cooled in a cryogenic linear radio-frequency quadrupole trap. With helium collision rates of only about ten per second--that is, four to five orders of magnitude lower than in typical buffer-gas cooling settings--we have cooled a single molecular ion to a rotational temperature of 7.5(+0.9)(-0.7) kelvin, the lowest such temperature so far measured. In addition, by varying the shape of, or the number of atomic and molecular ions in, larger Coulomb crystals, or both, we have tuned the effective rotational temperature from about 7 kelvin to about 60 kelvin by changing the translational micromotion energy of the ions. The extremely low helium collision rate may allow for sympathetic sideband cooling of single molecular ions, and eventually make quantum-logic spectroscopy of buffer-gas-cooled molecular ions feasible. Furthermore, application of the present cooling scheme to complex molecular ions should enable single- or few-state manipulations of individual molecules of biological interest.
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Atom Interferometry in a Warm Vapor
Biedermann, G. W.; McGuinness, H. J.; Rakholia, A. V.; ...
2017-04-17
Here, we demonstrate matter-wave interference in a warm vapor of rubidium atoms. Established approaches to light-pulse atom interferometry rely on laser cooling to concentrate a large ensemble of atoms into a velocity class resonant with the atom optical light pulse. In our experiment, we show that clear interference signals may be obtained without laser cooling. This effect relies on the Doppler selectivity of the atom interferometer resonance. Lastly, this interferometer may be configured to measure accelerations, and we demonstrate that multiple interferometers may be operated simultaneously by addressing multiple velocity classes.
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Füzesi, F; Jornod, A; Thomann, P; Plimmer, M D; Dudle, G; Moser, R; Sache, L; Bleuler, H
2007-10-01
This article describes the design, characterization, and performance of an electrostatic glass actuator adapted to an ultrahigh vacuum environment (10(-8) mbar). The three-phase rotary motor is used to drive a turbine that acts as a velocity-selective light trap for a slow continuous beam of laser-cooled atoms. This simple, compact, and nonmagnetic device should find applications in the realm of time and frequency metrology, as well as in other areas of atomic, molecular physics and elsewhere.
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Trapped-Ion Quantum Simulation of an Ising Model with Transverse and Longitudinal Fields
2013-03-29
resonant λ = 355 nm laser beams which drive stimulated Raman transitions [33, 34]. The beams intersect at right angles so that their wavevector difference...ated by a pair of Raman laser beams with a beatnote frequency of ωS , with the field amplitude determined by the beam intensities. The field directions...cool- ing, followed by optical pumping to the state |↓↓↓ ..〉z and 100 µs of Raman sideband cooling that prepares the motion of all modes along ∆~k in
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Fission fragment excited laser system
McArthur, David A.; Tollefsrud, Philip B.
1976-01-01
A laser system and method for exciting lasing action in a molecular gas lasing medium which includes cooling the lasing medium to a temperature below about 150 K and injecting fission fragments through the lasing medium so as to preferentially excite low lying vibrational levels of the medium and to cause population inversions therein. The cooled gas lasing medium should have a mass areal density of about 5 .times. 10.sup.-.sup.3 grams/square centimeter, relaxation times of greater than 50 microseconds, and a broad range of excitable vibrational levels which are excitable by molecular collisions.
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Optomechanical performance of 3D-printed mirrors with embedded cooling channels and substructures
NASA Astrophysics Data System (ADS)
Mici, Joni; Rothenberg, Bradley; Brisson, Erik; Wicks, Sunny; Stubbs, David M.
2015-09-01
Advances in 3D printing technology allow for the manufacture of topologically complex parts not otherwise feasible through conventional manufacturing methods. Maturing metal and ceramic 3D printing technologies are becoming more adept at printing complex shapes, enabling topologically intricate mirror substrates. One application area that can benefit from additive manufacturing is reflective optics used in high energy laser (HEL) systems that require materials with a low coefficient of thermal expansion (CTE), high specific stiffness, and (most importantly) high thermal conductivity to effectively dissipate heat from the optical surface. Currently, the limits of conventional manufacturing dictate the topology of HEL optics to be monolithic structures that rely on passive cooling mechanisms and high reflectivity coatings to withstand laser damage. 3D printing enables the manufacture of embedded cooling channels in metallic mirror substrates to allow for (1) active cooling and (2) tunable structures. This paper describes the engineering and analysis of an actively cooled composite optical structure to demonstrate the potential of 3D printing on the improvement of optomechanical systems.
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Quantum calculations for one-dimensional cooling of helium
DOE Office of Scientific and Technical Information (OSTI.GOV)
Vredenbregt, E.; Doery, M.; Bergeman, T.
1993-05-01
We report theoretical velocity distributions for sub-Doppler laser cooling of metastable He*(2{sup 3}S), calculated with the Density Matrix and Monte Carlo Wavefunction approaches. For low-field (B = 50 mG) magnetic-field induced laser cooling on the 2{sup 3}S {yields} (2{sup 3}P, J = 2) transition ({lambda} = 1083 nm), we get a narrow, sub-Doppler structure, consisting of three, {approximately}1 photon recoil wide peaks, spaced {approximately}1 recoil apart. With increasing field, this three-peak structure develops into two velocity-selective resonance (VSR) peaks, each {approximately}2 recoils wide. For the 2{sup 3}S {yields} (3{sup 3}P, J = 2) transition ({lambda} 389 nm), VSR peaks aremore » predicted to appear at low field without the third, central peak, which only develops at higher field (B = 200 mG). Additional computations deal with polarization-gradient cooling. In general, we find that for one-dimensional cooling calculations, the Density Matrix method is more efficient than the Monte Carlo Wavefunction approach. Experiments are currently under way to test the results.« less
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Laser cooling of nuclear spin 0 alkali 78Rb
NASA Astrophysics Data System (ADS)
Behr, J. A.; Gorelov, A.; Anholm, M.
2015-05-01
The textbook example for sub-Doppler cooling is a J = 1/2 I = 0 alkali atom in lin ⊥ lin molasses. In the σ+ σ- configuration of a standard MOT, the main sub-Doppler cooling mechanism relies on changing alignment (MF2 population) with the summed linear polarization orientation, but there is no such variation in AC Stark shift for F = 1/2. We have nevertheless looked for signs of sub-Doppler cooling by trapping I = 0 78Rb in a standard MOT and measuring the cloud size as a function of laser detuning and intensity. The 78Rb cloud size does not change significantly with lowered intensity, and expands slightly with detuning, consistent with minimal to no sub-Doppler cooling. Our geometry does show the well-known substantially smaller cloud size with detuning and intensity for I = 3/2 87Rb. Maintaining an I = 0 alkali cloud size with lowered intensity will help our planned β- ν correlation experiments in 38mK decay by suppressing possible production of photoassisted dimers. Supported by NSERC and NRC Canada through TRIUMF.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Xu, Pei-quan; Li, Leijun, E-mail: leijun.li@ualberta.ca; Zhang, Chunbo
The as-welded microstructure of laser-welded Ti-6Al-4V is characterized as a function of CO2 key-hole mode laser welding speed. Martensitic α′ is the predominant phase, with some α and retained β. Phase transformation is affected by the cooling rate through laser welding speed. A higher welding speed of 1.6 to 2.0 m/min produced more martensite α′ and less retained β in the welds. 1.4 m/min welding speed produced small amounts of α, besides the martensite α′. A trace of δ titanium hydride phase seems to have formed in the weld fusion zone. Moiré fringes are a common feature in the TEMmore » microstructure, due to abundance of multi-phase interfaces. Tensile twins and clusters of dislocations indicate that plastic deformation has happened in the as-welded microstructure, indicating the local stress levels to be approaching the yield stress on-cooling during laser welding.« less
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Selective laser melting of hypereutectic Al-Si40-powder using ultra-short laser pulses
NASA Astrophysics Data System (ADS)
Ullsperger, T.; Matthäus, G.; Kaden, L.; Engelhardt, H.; Rettenmayr, M.; Risse, S.; Tünnermann, A.; Nolte, S.
2017-12-01
We investigate the use of ultra-short laser pulses for the selective melting of Al-Si40-powder to fabricate complex light-weight structures with wall sizes below 100 μ {m} combined with higher tensile strength and lower thermal expansion coefficient in comparison to standard Al-Si alloys. During the cooling process using conventional techniques, large primary silicon particles are formed which impairs the mechanical and thermal properties. We demonstrate that these limitations can be overcome using ultra-short laser pulses enabling the rapid heating and cooling in a non-thermal equilibrium process. We analyze the morphology characteristics and micro-structures of single tracks and thin-walled structures depending on pulse energy, repetition rate and scanning velocity utilizing pulses with a duration of 500 {fs} at a wavelength of 1030 {nm}. The possibility to specifically change and optimize the microstructure is shown.
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Gow, A M; McDonald, A V; Pearson, G J; Setchell, D J
1999-01-01
Infrared lasers are reported to have thermal side effects which may damage pulp tissue. This study investigated the thermal effects of the pulsed Nd:YAG laser. Prepared, extracted teeth were measured prior to irradiation. Temperature was recorded using a thermocouple/data logging system. Laser irradiation was carried out with or without water spray for an exposure time of ten seconds. Results indicated that dry irradiation produced unacceptable temperature rises with dentine thicknesses used. Wet irradiation produced a significantly lower temperature rise. It was concluded that the Nd:YAG laser produced thermal effects which could potentially cause pulpal trauma. A water coolant was effective in reducing these thermal effects, but the temperature rise achieved whilst using water coolant may still cause pulpal damage.
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A novel "gain chip" concept for high-power lasers (Conference Presentation)
NASA Astrophysics Data System (ADS)
Li, Min; Li, Mingzhong; Wang, Zhenguo; Yan, Xiongwei; Jiang, Xinying; Zheng, Jiangang; Cui, Xudong; Zhang, Xiaomin
2017-05-01
High-power lasers, including high-peak power lasers (HPPL) and high-average power lasers (HAPL), attract much interest for enormous variety of applications in inertial fusion energy (IFE), materials processing, defense, spectroscopy, and high-field physics research. To meet the requirements of high efficiency and quality, a "gain chip" concept is proposed to properly design the pumping, cooling and lasing fields. The gain chip mainly consists of the laser diode arrays, lens duct, rectangle wave guide and slab-shaped gain media. For the pumping field, the pump light will be compressed and homogenized by the lens duct to high irradiance with total internal reflection, and further coupled into the gain media through its two edge faces. For the cooling field, the coolant travels along the flow channel created by the adjacent slabs in the other two edge-face direction, and cool the lateral faces of the gain media. For the lasing field, the laser beam travels through the lateral faces and experiences minimum thermal wavefront distortions. Thereby, these three fields are in orthogonality offering more spatial freedom to handle them during the construction of the lasers. Transverse gradient doping profiles for HPPL and HAPL have been employed to achieve uniform gain distributions (UGD) within the gain media, respectively. This UGD will improve the management for both amplified spontaneous emission (ASE) and thermal behavior. Since each "gain chip" has its own pump source, power scaling can be easily achieved by placing identical "gain chips" along the laser beam axis without disturbing the gain and thermal distributions. To detail our concept, a 1-kJ pulsed amplifier is designed and optical-to-optical efficiency up to 40% has been obtained. We believe that with proper coolant (gas or liquid) and gain media (Yb:YAG, Nd:glass or Nd:YAG) our "gain chip" concept might provide a general configuration for high-power lasers with high efficiency and quality.
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Compact atom interferometer using single laser
NASA Astrophysics Data System (ADS)
Chiow, Sheng-Wey; Yu, Nan
2017-04-01
Atom interferometer (AI) based sensors exhibit precision and accuracy unattainable with classical sensors, thanks to the inherent stability of atomic properties. The complexity of required laser system and the size of vacuum chamber driven by optical access requirement limit the applicability of such technology in size, weight, and power (SWaP) challenging environments, such as in space. For instance, a typical physics package of AI includes six viewports for laser cooling and trapping, two for AI beams, and two more for detection and a vacuum pump. Similarly, a typical laser system for an AI includes two lasers for cooling and repumping, and two for Raman transitions as AI beam splitters. In this presentation, we report our efforts in developing a miniaturized atomic accelerometer for planetary exploration. We will describe a physics package configuration having minimum optical access (thus small volume), and a laser and optics system utilizing a single laser for the sensor operation. Preliminary results on acceleration sensitivity will be discussed. We will also illustrate a path for further packaging and integration based on the demonstrated concepts. This research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
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NASA Technical Reports Server (NTRS)
1990-01-01
The principal method of dealing with coronary artery blockage is bypass surgery. A non-surgical alternative available to some patients is balloon angioplasty. For several years, medical researchers have been exploring another alternative that would help a wider circle of patients than the balloon treatment and entail less risk than bypass surgery. A research group is on the verge of an exciting development: laser angioplasty with a 'cool' type of laser, called an excimer laser, that does not damage blood vessel walls and offers non-surgical cleansing of clogged arteries with extraordinary precision. The system is the Dymer 200+ Excimer Laser Angioplasty System, developed by Advanced Intraventional Systems. Used in human clinical tests since 1987, the system is the first fully integrated 'cool' laser capable of generating the requisite laser energy and delivering the energy to target arteries. Thirteen research hospitals in the U.S. have purchased Dymer 200+ systems and used them in clinical trials in 121 peripheral and 555 coronary artery cases. The success rate in opening blocked coronary arteries is 85 percent, with fewer complications than in balloon angioplasty. Food and Drug Administration approval for the system is hoped for in the latter part of 1990. * Advanced Intraventional Systems became Spectranetics in 1994 and discontinued the product.
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Two dimensional finite element thermal model of laser surface glazing for H13 tool steel
NASA Astrophysics Data System (ADS)
Kabir, I. R.; Yin, D.; Naher, S.
2016-10-01
A two dimensional (2D) transient thermal model with line-heat-source was developed by Finite Element Method (FEM) for laser surface glazing of H13 tool steel using commercial software-ANSYS 15. The geometry of the model was taken as a transverse circular cross-section of cylindrical specimen. Two different power levels (300W, 200W) were used with 0.2mm width of laser beam and 0.15ms exposure time. Temperature distribution, heating and cooling rates, and the dimensions of modified surface were analysed. The maximum temperatures achieved were 2532K (2259°C) and 1592K (1319°C) for laser power 300W and 200W respectively. The maximum cooling rates were 4.2×107 K/s for 300W and 2×107 K/s for 200W. Depths of modified zone increased with increasing laser power. From this analysis, it can be predicted that for 0.2mm beam width and 0.15ms time exposer melting temperature of H13 tool steel is achieved within 200-300W power range of laser beam in laser surface glazing.
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Music, Mark; Finderle, Zarko; Cankar, Ksenija
2011-05-01
The aim of the present study was to investigate the effect of quantitatively measured cold perception (CP) thresholds on microcirculatory response to local cooling as measured by direct and indirect response of laser-Doppler (LD) flux during local cooling at different temperatures. The CP thresholds were measured in 18 healthy males using the Marstock method (thermode placed on the thenar). The direct (at the cooling site) and indirect (on contralateral hand) LD flux responses were recorded during immersion of the hand in a water bath at 20°C, 15°C, and 10°C. The cold perception threshold correlated (linear regression analysis, Pearson correlation) with the indirect LD flux response at cooling temperatures 20°C (r=0.782, p<0.01) and 15°C (r=0.605, p<0.01). In contrast, there was no correlation between the CP threshold and the indirect LD flux response during cooling in water at 10°C. The results demonstrate that during local cooling, depending on the cooling temperature used, cold perception threshold influences indirect LD flux response. Copyright © 2011 Elsevier Inc. All rights reserved.
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Narrow Line Cooling of 88Sr Atoms in the Magneto-optical Trap for Precision Frequency Standard
NASA Astrophysics Data System (ADS)
Strelkin, S. A.; Galyshev, A. A.; Berdasov, O. I.; Gribov, A. Yu.; Sutyrin, D. V.; Khabarova, K. Yu.; Kolachevsky, N. N.; Slyusarev, S. N.
We report on our progress toward the realization of a Strontium optical lattice clock, which is under development at VNIIFTRI as a part of GLONASS program. We've prepared the narrow line width laser system for secondary cooling of 88Sr atoms which allows us to reach atom cloud temperature below 3 μK after second cooling stage.
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Prediction of Skin Temperature Distribution in Cosmetic Laser Surgery
NASA Astrophysics Data System (ADS)
Ting, Kuen; Chen, Kuen-Tasnn; Cheng, Shih-Feng; Lin, Wen-Shiung; Chang, Cheng-Ren
2008-01-01
The use of lasers in cosmetic surgery has increased dramatically in the past decade. To achieve minimal damage to tissues, the study of the temperature distribution of skin in laser irradiation is very important. The phenomenon of the thermal wave effect is significant due to the highly focused light energy of lasers in very a short time period. The conventional Pennes equation does not take the thermal wave effect into account, which the thermal relaxation time (τ) is neglected, so it is not sufficient to solve instantaneous heating and cooling problem. The purpose of this study is to solve the thermal wave equation to determine the realistic temperature distribution during laser surgery. The analytic solutions of the thermal wave equation are compared with those of the Pennes equation. Moreover, comparisons are made between the results of the above equations and the results of temperature measurement using an infrared thermal image instrument. The thermal wave equation could likely to predict the skin temperature distribution in cosmetic laser surgery.
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Two-Dimensional Laser-Speckle Surface-Strain Gauge
NASA Technical Reports Server (NTRS)
Barranger, John P.; Lant, Christian
1992-01-01
Extension of Yamaguchi's laser-speckle surface-strain-gauge method yields data on two-dimensional surface strains in times as short as fractions of second. Laser beams probe rough spot on surface of specimen before and after processing. Changes in speckle pattern of laser light reflected from spot indicative of changes in surface strains during processing. Used to monitor strains and changes in strains induced by hot-forming and subsequent cooling of steel.
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Distributed feedback InGaN/GaN laser diodes
NASA Astrophysics Data System (ADS)
Slight, Thomas J.; Watson, Scott; Yadav, Amit; Grzanka, Szymon; Stanczyk, Szymon; Docherty, Kevin E.; Rafailov, Edik; Perlin, Piotr; Najda, Steve; Leszczyński, Mike; Kelly, Anthony E.
2018-02-01
We have realised InGaN/GaN distributed feedback laser diodes emitting at a single wavelength in the 42X nm wavelength range. Laser diodes based on Gallium Nitride (GaN) are useful devices in a wide range of applications including atomic spectroscopy, data storage and optical communications. To fully exploit some of these application areas there is a need for a GaN laser diode with high spectral purity, e.g. in atomic clocks, where a narrow line width blue laser source can be used to target the atomic cooling transition. Previously, GaN DFB lasers have been realised using buried or surface gratings. Buried gratings require complex overgrowth steps which can introduce epi-defects. Surface gratings designs, can compromise the quality of the p-type contact due to dry etch damage and are prone to increased optical losses in the grating regions. In our approach the grating is etched into the sidewall of the ridge. Advantages include a simpler fabrication route and design freedom over the grating coupling strength.Our intended application for these devices is cooling of the Sr+ ion and for this objective the laser characteristics of SMSR, linewidth, and power are critical. We investigate how these characteristics are affected by adjusting laser design parameters such as grating coupling coefficient and cavity length.
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Novel packaging for CW and QCW diode laser modules for operation with high power and duty cycles
NASA Astrophysics Data System (ADS)
Fassbender, Wilhelm; Lotz, Jens; Kissel, Heiko; Biesenbach, Jens
2018-02-01
Continuous wave (CW) and quasi-continuous wave (QCW) operated diode laser bars and arrays have found a wide range of industrial, medical, scientific, military and space applications with a broad variety in wavelength, pulse energy, pulse duration and beam quality. Recent applications require even higher power, duty cycles and power density. The heat loss will be dissipated by conductive cooling or liquid cooling close to the bars. We present the latest performance and reliability data of two novel high-brightness CW and QCW arrays of customized and mass-production modules, in compact and robust industry design for operation with high power and high duty cycles. All designs are based on single diode packages consisting of 10mm laser bars, soft or hard soldered between expansion matched submounts. The modular components cover a wide span of designs which differ basically in water/conduction (active/passive) cooled, single, linear (horizontal and vertical) arranged designs, as well as housed and unhoused modules. The different assembling technologies of active and passive cooled base plates affect the heat dissipation and therefore the reachable power at different QCW operating conditions, as well as the lifetime. As an example, a package consisting of 8 laser diodes, connected to a 28.8*13.5*7.0mm3 DCB (direct copper bonded) submount, passively or actively cooled is considered. This design is of particular interest for mobile applications seamless module to module building system, with an infinite number of laser bars at 1.7mm pitch. Using 940nm bars we can reach an optical output power per bar of 450W at 25°C base plate temperature with 10Hz, 1.2% duty cycle and 1.2ms pulse duration. As an additional example, micro channel coolers can be vertically stacked up to 50 diodes with a 1,15mm pitch. This design is suitable for all applications, demanding also compactness and light weight and high power density. Using near infrared bars and others, we can reach an optical output power of 250W per bar at 25°C coolant temperature at CW operation.
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NASA Technical Reports Server (NTRS)
Scott, D.; Herman, R.; Webster, C.; May, R.; Flesch, G.; Moyer, E.
1998-01-01
The Airborne Laser Infrared Absorption Spectrometer II (ALIAS-II) is a lightweight, high-resolution (0.0003 cm-1), scanning, mid-infrared absorption spectrometer based on cooled (80 K) lead-salt tunable diode laser sources.
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Simulation of Laser Cooling and Trapping in Engineering Applications
NASA Technical Reports Server (NTRS)
Ramirez-Serrano, Jaime; Kohel, James; Thompson, Robert; Yu, Nan; Lunblad, Nathan
2005-01-01
An advanced computer code is undergoing development for numerically simulating laser cooling and trapping of large numbers of atoms. The code is expected to be useful in practical engineering applications and to contribute to understanding of the roles that light, atomic collisions, background pressure, and numbers of particles play in experiments using laser-cooled and -trapped atoms. The code is based on semiclassical theories of the forces exerted on atoms by magnetic and optical fields. Whereas computer codes developed previously for the same purpose account for only a few physical mechanisms, this code incorporates many more physical mechanisms (including atomic collisions, sub-Doppler cooling mechanisms, Stark and Zeeman energy shifts, gravitation, and evanescent-wave phenomena) that affect laser-matter interactions and the cooling of atoms to submillikelvin temperatures. Moreover, whereas the prior codes can simulate the interactions of at most a few atoms with a resonant light field, the number of atoms that can be included in a simulation by the present code is limited only by computer memory. Hence, the present code represents more nearly completely the complex physics involved when using laser-cooled and -trapped atoms in engineering applications. Another advantage that the code incorporates is the possibility to analyze the interaction between cold atoms of different atomic number. Some properties that cold atoms of different atomic species have, like cross sections and the particular excited states they can occupy when interacting with each other and light fields, play important roles not yet completely understood in the new experiments that are under way in laboratories worldwide to form ultracold molecules. Other research efforts use cold atoms as holders of quantum information, and more recent developments in cavity quantum electrodynamics also use ultracold atoms to explore and expand new information-technology ideas. These experiments give a hint on the wide range of applications and technology developments that can be tackled using cold atoms and light fields. From more precise atomic clocks and gravity sensors to the development of quantum computers, there will be a need to completely understand the whole ensemble of physical mechanisms that play a role in the development of such technologies. The code also permits the study of the dynamic and steady-state operations of technologies that use cold atoms. The physical characteristics of lasers and fields can be time-controlled to give a realistic simulation of the processes involved such that the design process can determine the best control features to use. It is expected that with the features incorporated into the code it will become a tool for the useful application of ultracold atoms in engineering applications. Currently, the software is being used for the analysis and understanding of simple experiments using cold atoms, and for the design of a modular compact source of cold atoms to be used in future research and development projects. The results so far indicate that the code is a useful design instrument that shows good agreement with experimental measurements (see figure), and a Windows-based user-friendly interface is also under development.
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NASA Astrophysics Data System (ADS)
Leers, Michael; Scholz, Christian; Boucke, Konstantin; Poprawe, Reinhart
2006-02-01
The lifetime of high-power diode lasers, which are cooled by standard copper heatsinks, is limited. The reasons are the aging of the indium solder normally employed as well as the mechanical stress caused by the mismatch between the copper heatsink (16 - 17ppm/K) and the GaAs diode laser bars (6 - 7.5 ppm/K). For micro - channel heatsinks corrosion and erosion of the micro channels limit the lifetime additionally. The different thermal behavior and the resulting stress cannot be compensated totally by the solder. Expansion matched heatsink materials like tungsten-copper or aluminum nitride reduce this stress. A further possible solution is a combination of copper and molybdenum layers, but all these materials have a high thermal resistance in common. For high-power electronic or low cost medical applications novel materials like copper/carbon compound, compound diamond or high-conductivity ceramics were developed during recent years. Based on these novel materials, passively cooled heatsinks are designed, and thermal and mechanical simulations are performed to check their properties. The expansion of the heatsink and the induced mechanical stress between laser bar and heatsink are the main tasks for the simulations. A comparison of the simulation with experimental results for different material combinations illustrates the advantages and disadvantages of the different approaches. Together with the boundary conditions the ideal applications for packaging with these materials are defined. The goal of the development of passively-cooled expansion-matched heatsinks has to be a long-term reliability of several 10.000h and a thermal resistance below 1 K/W.
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NASA Astrophysics Data System (ADS)
Kwiatkowski, Jacek; Zendzian, Waldemar; Jabczynski, Jan K.
2016-12-01
A detailed study of a Tm:YAP laser in continuous-wave (CW), single-pass end-pumped by a 793 nm diode laser is presented. The laser based on c-cut 3 at. % Tm:YAP crystal was experimentally examined and presented in the dependence on transmittance and radius of curvature of output coupling mirrors. A detailed spectral analysis was presented. The influence of a heat-sink cooling water temperature on the laser performance was studied. At room temperature, for an output coupling transmission of 19.5%, the maximum CW output power of 4.53 W was achieved, corresponding to a slope efficiency of 41.5% and an optical-to-optical conversion efficiency of 25.7% with respect to the incident pump power, respectively. We have shown that the output spectrum at a certain wavelength (e.g. 1940 nm) for a given pump power can be realized via the change of resonator parameters (OC transmittance, mode size).
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Thermal stress in dentin and enamel under CO2 laser irradiation
NASA Astrophysics Data System (ADS)
Meyer, Dirk H.; Foth, Hans-Jochen
1996-01-01
Ablation of dentin and tartar was studied under carbon dioxide-laser irradiation in cw and pulse mode with pulse length down to 150 microseconds. The specimens had been cut by a diamant blade to slices of thicknesses between 0.8 and 2.8 mm. The laser induced temperature rise was measured by an infrared camera monitoring the backside of the samples. The specimens shape and structure at the laser spot was analyzed by electron microscopy. Of special interest was the testing of the SwiftLaseTM to reducing the heat. The experimental results show the necessity of a water cooling in all application modes. The origin of the cracks which had been observed in many of the samples, is currently under investigation.
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Nelson, J. Stuart; Anvari, Bahman; Tanenbaum, B. Samuel; Milner, Thomas E.
1999-01-01
Cryogen spray cooling of skin surface with millisecond cryogen spurts is an effective method for establishing a controlled temperature distribution in tissue and protecting the epidermis from nonspecific thermal injury during laser mediated dermatological procedures. Control of humidity level, spraying distance and cryogen boiling point is material to the resulting surface temperature. Decreasing the ambient humidity level results in less ice formation on the skin surface without altering the surface temperature during the cryogen spurt. For a particular delivery nozzle, increasing the spraying distance to 85 millimeters lowers the surface temperature. The methodology comprises establishing a controlled humidity level in the theater of operation of the irradiation site of the biological tissues before and/or during the cryogenic spray cooling of the biological tissue. At cold temperatures calibration was achieved by mounting a thermistor on a thermoelectric cooler. The thermal electric cooler was cooled from from 20.degree. C. to about -20.degree. C. while measuring its infrared emission.
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Novel Wavelength Standards in the Near IR
2008-04-15
optical fiber, and dashed lines indicate free-space opti- cal beams. Aspheric lenses are shown as shaded ovals; the vacuum chambers (VC), indicated...shows the laser configuration, with a 10 mm long Brewster -cut crystal of Cr:f, cooled to -5°C and pumped at 1075 nm by 8 W of power from a Yb:fiber...modelocked Cr:f system. EXPERIMENT The laser used in this study is based on a folded bow-tie cavity configuration that uses a 10 mm long Brewster
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Model of Laser-Induced Temperature Changes in Solid-State Optical Refrigerators
2010-01-01
Model of laser-induced temperature changes in solid-state optical refrigerators W. M. Patterson,1,a M. Sheik- Bahae ,1 R. I . Epstein,2 and M. P...Applications of Laser Cooling of Sol- ids, edited by R. I . Epstein and M. Sheik- Bahae Wiley, Weinheim, 2009. 2W. Koechner, Solid-State Laser...2004. 19D. V. Seletskiy, S. D. Melgaard, S. Bigotta, A. Di Lieto, M. Tonelli, R. I . Epstein, and M. Sheik- Bahae , in Conference on Lasers and Electro
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Ultracold Fermions in the P-Orbital Band of an Optical Lattice
2015-07-27
introduces (1) a new degree of freedom due to orbital degeneracy and (2) a tunneling anisotropy which depends on the orientation of the orbital wavefunction...demonstrated this new technique with a diode -pumped solid-state laser operating at 1342 nm that could be frequency doubled to provide 671 nm light for laser...Figure 3: Self-injection locked, diode -pumped solid-state laser for laser cooling of Li atoms. The solid-state Nd:YVO4 laser at the top consists of a
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A High Power Frequency Doubled Fiber Laser
NASA Technical Reports Server (NTRS)
Thompson, Robert J.; Tu, Meirong; Aveline, Dave; Lundblad, Nathan; Maleki, Lute
2003-01-01
This viewgraph presentation reports on the development of a high power 780 nm laser suitable for space applications of laser cooling. A possible solution is to use frequency doubling of high power 1560 nm telecom lasers. The presentation shows a diagram of the frequency conversion, and a graph of the second harmonic generation in one crystal, and the use of the cascading crystals. Graphs show the second harmonic power as a function of distance between crystals, second harmonic power vs. pump power, tunability of laser systems.
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An overview of clinical and experimental treatment modalities for port wine stains
Chen, Jennifer K.; Ghasri, Pedram; Aguilar, Guillermo; van Drooge, Anne Margreet; Wolkerstorfer, Albert; Kelly, Kristen M.; Heger, Michal
2014-01-01
Port wine stains (PWS) are the most common vascular malformation of the skin, occurring in 0.3% to 0.5% of the population. Noninvasive laser irradiation with flashlamp-pumped pulsed dye lasers (selective photothermolysis) currently comprises the gold standard treatment of PWS; however, the majority of PWS fail to clear completely after selective photothermolysis. In this review, the clinically used PWS treatment modalities (pulsed dye lasers, alexandrite lasers, neodymium:yttrium-aluminum-garnet lasers, and intense pulsed light) and techniques (combination approaches, multiple passes, and epidermal cooling) are discussed. Retrospective analysis of clinical studies published between 1990 and 2011 was performed to determine therapeutic efficacies for each clinically used modality/technique. In addition, factors that have resulted in the high degree of therapeutic recalcitrance are identified, and emerging experimental treatment strategies are addressed, including the use of photodynamic therapy, immunomodulators, angiogenesis inhibitors, hypobaric pressure, and site-specific pharmaco-laser therapy. PMID:22305042
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High-power laser phosphor light source with liquid cooling for digital cinema applications
NASA Astrophysics Data System (ADS)
Li, Kenneth
2014-02-01
Laser excited phosphor has been used to excite phosphor material, producing high intensity light output with smaller etendue than that of LEDs with the same long lifetime. But due to the high intensity of the laser light, phosphor with organic binder burns at low power, which requires the phosphor to be deposited on a rotating wheel in practical applications. Phosphor with inorganic binders, commonly known as ceramic phosphor, on the other hand, does not burn, but efficiency goes down as temperature goes up under high power excitation. This paper describes cooling schemes in sealed chambers such that the phosphor materials using organic or inorganic binders can be liquid cooled for high efficiency operations. Confined air bubbles are introduced into the sealed chamber accommodating the differential thermal expansion of the liquid and the chamber. For even higher power operation suitable for digital cinema, a suspension of phosphor in liquid is described suitable for screen brightness of over 30,000 lumens. The aging issues of phosphor can also be solved by using replaceable phosphor cartridges.
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Advanced 2-micron Solid-state Laser for Wind and CO2 Lidar Applications
NASA Technical Reports Server (NTRS)
Yu, Jirong; Trieu, Bo C.; Petros, Mulugeta; Bai, Yingxin; Petzar, Paul J.; Koch, Grady J.; Singh, Upendra N.; Kavaya, Michael J.
2006-01-01
Significant advancements in the 2-micron laser development have been made recently. Solid-state 2-micron laser is a key subsystem for a coherent Doppler lidar that measures the horizontal and vertical wind velocities with high precision and resolution. The same laser, after a few modifications, can also be used in a Differential Absorption Lidar (DIAL) system for measuring atmospheric CO2 concentration profiles. The world record 2-micron laser energy is demonstrated with an oscillator and two amplifiers system. It generates more than one joule per pulse energy with excellent beam quality. Based on the successful demonstration of a fully conductive cooled oscillator by using heat pipe technology, an improved fully conductively cooled 2-micron amplifier was designed, manufactured and integrated. It virtually eliminates the running coolant to increase the overall system efficiency and reliability. In addition to technology development and demonstration, a compact and engineering hardened 2-micron laser is under development. It is capable of producing 250 mJ at 10 Hz by an oscillator and one amplifier. This compact laser is expected to be integrated to a lidar system and take field measurements. The recent achievements push forward the readiness of such a laser system for space lidar applications. This paper will review the developments of the state-of-the-art solid-state 2-micron laser.
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Shock wave loading of a magnetic guide
NASA Astrophysics Data System (ADS)
Kindt, L.
2011-10-01
The atom laser has long been a holy grail within atom physics and with the creation of an atom laser we hope to bring a similar revolution in to the field of atom optics. With the creation of the Bose-Einstein Condensate (BEC) in 1995 the path to an atom laser was initiated. An atom laser is continues source of BEC. In a Bose condensate all the atoms occupy the same quantum state and can be described by the same wave function and phase. With an atom laser the De Broglie wavelength of atoms can be much smaller than the wavelength of light. Due to the ultimate control over the atoms the atom laser is very interesting for atom optics, lithography, metrology, etching and deposition of atoms on a surface. All previous atom lasers have been created from atoms coupled out from an existing Bose-Einstein Condensate. There are different approaches but common to them all is that the duration of the output of the atom laser is limited by the size of the initial BEC and they all have a low flux. This leaves the quest to build a continuous high flux atom laser. An alternative approach to a continuous BEC beam is to channel a continuous ultra cold atomic beam into a magnetic guide and then cool this beam down to degeneracy. Cooling down a continuous beam of atoms faces three large problems: The collision rate has to be large enough for effective rethermalization, since evaporative cooling in 2D is not as effective as in 3D and a large thermal conductivity due to atoms with a high angular momentum causes heating downstream in the guide. We have built a 4 meter magnetic guide that is placed on a downward slope with a magnetic barrier in the end. In the guide we load packets of ultra cold rubidium atoms with a frequency rate large enough for the packets to merge together to form a continuous atomic beam. The atomic beam is supersonic and when the beam reaches the end barrier it will return and collide with itself. The collisions lowers the velocity of the beam into subsonic velocities and a shock wave is created between the two velocity regions. In order to conserve number of particle, momentum and enthalpy the density of the atomic beam passing through the shock wave must increase. We have build such a shock wave in an atomic beam and observed the density increase due to this. As an extra feature having a subsonic beam on a downward slope adds an extra density increase due to gravitational compression. Loading ultra cold atoms into a 3D trap from the dense subsonic beam overcomes the problem with 2D cooling and thermal conductivity. This was done and evaporative cooling was applied creating an unprecedented large number rubidium BEC.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Nicolaie, Ph.; Stenz, C.; Tikhonchuk, V.
2008-08-15
The interaction of laser driven jets with gas puffs at various pressures is investigated experimentally and is analyzed by means of numerical tools. In the experiment, a combination of two complementary diagnostics allowed to characterize the main structures in the interaction zone. By changing the gas composition and its density, the plasma cooling time can be controlled and one can pass from a quasiadiabatic outflow to a strongly radiation cooling jet. This tuning yields hydrodynamic structures very similar to those seen in astrophysical objects; the bow shock propagating through the gas, the shocked materials, the contact discontinuity, and the Machmore » disk. From a dimensional analysis, a scaling is made between both systems and shows the study relevance for the jet velocity, the Mach number, the jet-gas density ratio, and the dissipative processes. The use of a two-dimensional radiation hydrodynamic code, confirms the previous analysis and provides detailed structure of the interaction zone and energy repartition between jet and surrounding gases.« less
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Recirculation of Laser Power in an Atomic Fountain
NASA Technical Reports Server (NTRS)
Enzer, Daphna G.; Klipstein, WIlliam M.; Moore, James D.
2007-01-01
A new technique for laser-cooling atoms in a cesium atomic fountain frequency standard relies on recirculation of laser light through the atom-collection region of the fountain. The recirculation, accomplished by means of reflections from multiple fixed beam-splitter cubes, is such that each of two laser beams makes three passes. As described below, this recirculation scheme offers several advantages over prior designs, including simplification of the laser system, greater optical power throughput, fewer optical and electrical connections, and simplification of beam power balancing. A typical laser-cooled cesium fountain requires the use of six laser beams arranged as three orthogonal pairs of counter-propagating beams to decelerate the atoms and hold them in a three-dimensional optical trap in vacuum. Typically, these trapping/cooling beams are linearly polarized and are positioned and oriented so that (1) counter-propagating beams in each pair have opposite linear polarizations and (2) three of the six orthogonal beams have the sum of their propagation directions pointing up, while the other three have the sum of their propagation directions pointing down. In a typical prior design, two lasers are used - one to generate the three "up" beams, the other to generate the three "down" beams. For this purpose, the output of each laser is split three ways, then the resulting six beams are delivered to the vacuum system, independently of each other, via optical fibers. The present recirculating design also requires two lasers, but the beams are not split before delivery. Instead, only one "up" beam and one oppositely polarized "down" beam are delivered to the vacuum system, and each of these beams is sent through the collection region three times. The polarization of each beam on each pass through the collection region is set up to yield the same combination of polarization and propagation directions as described above. In comparison with the prior design, the present recirculating design utilizes the available laser light more efficiently, making it possible to trap more atoms at a given laser power or the same number of atoms at a lower laser power. The present design is also simpler in that it requires fewer optical fibers, fiber couplings, and collimators, and fewer photodiodes for monitoring beam powers. Additionally, the present design alleviates the difficulty of maintaining constant ratios among power levels of the beams within each "up" or "down" triplet.
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Tunnell, James W; Chang, David W; Johnston, Carol; Torres, Jorge H; Patrick, Charles W; Miller, Michael J; Thomsen, Sharon L; Anvari, Bahman
2003-06-01
Increasing radiant exposure offers a means to increase treatment efficacy during laser-mediated treatment of vascular lesions, such as port-wine stains; however, excessive radiant exposure decreases selective vascular injury due to increased heat generation within the epidermis and collateral damage to perivascular collagen. To determine if cryogen spray cooling could be used to maintain selective vascular injury (ie, prevent epidermal and perivascular collagen damage) when using high radiant exposures (16-30 J/cm2). Observational study. Academic hospital and research laboratory. Twenty women with normal abdominal skin (skin phototypes I-VI). Skin was irradiated with a pulsed dye laser (wavelength = 585 nm; pulse duration = 1.5 milliseconds; 5-mm-diameter spot) using various radiant exposures (8-30 J/cm2) without and with cryogen spray cooling (50- to 300-millisecond cryogen spurts). Hematoxylin-eosin-stained histologic sections from each irradiated site were examined for the degree of epidermal damage, maximum depth of red blood cell coagulation, and percentage of vessels containing perivascular collagen coagulation. Long cryogen spurt durations (>200 milliseconds) protected the epidermis in light-skinned individuals (skin phototypes I-IV) at the highest radiant exposure (30 J/cm2); however, epidermal protection could not be achieved in dark-skinned individuals (skin phototypes V-VI) even at the lowest radiant exposure (8 J/cm2). The red blood cell coagulation depth increased with increasing radiant exposure (to >2.5 mm for skin phototypes I-IV and to approximately 1.2 mm for skin phototypes V-VI). In addition, long cryogen spurt durations (>200 milliseconds) prevented perivascular collagen coagulation in all skin types. Cryogen spurt durations much longer than those currently used in therapy (>200 milliseconds) may be clinically useful for protecting the epidermis and perivascular tissues when using high radiant exposures during cutaneous laser therapies. Additional studies are necessary to prove clinical safety of these protocols.
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Building one molecule from a reservoir of two atoms.
Liu, L R; Hood, J D; Yu, Y; Zhang, J T; Hutzler, N R; Rosenband, T; Ni, K-K
2018-05-25
Chemical reactions typically proceed via stochastic encounters between reactants. Going beyond this paradigm, we combined exactly two atoms in a single, controlled reaction. The experimental apparatus traps two individual laser-cooled atoms [one sodium (Na) and one cesium (Cs)] in separate optical tweezers and then merges them into one optical dipole trap. Subsequently, photoassociation forms an excited-state NaCs molecule. The discovery of previously unseen resonances near the molecular dissociation threshold and measurement of collision rates are enabled by the tightly trapped ultracold sample of atoms. As laser-cooling and trapping capabilities are extended to more elements, the technique will enable the study of more diverse, and eventually more complex, molecules in an isolated environment, as well as synthesis of designer molecules for qubits. Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.
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High-efficiency cavity-dumped micro-chip Yb:YAG laser
NASA Astrophysics Data System (ADS)
Nishio, M.; Maruko, A.; Inoue, M.; Takama, M.; Matsubara, S.; Okunishi, H.; Kato, K.; Kyomoto, K.; Yoshida, T.; Shimabayashi, K.; Morioka, M.; Inayoshi, S.; Yamagata, S.; Kawato, S.
2014-09-01
High-efficiency cavity-dumped ytterbium-doped yttrium aluminum garnet (Yb:YAG) laser was developed. Although the high quantum efficiency of ytterbium-doped laser materials is appropriate for high-efficiency laser oscillation, the efficiency is decreased by their quasi-three/four laser natures. High gain operation by high intensity pumping is suitable for high efficiency oscillation on the quasi-three/four lasers without extremely low temperature cooling. In our group, highest efficiency oscillations for continuous wave, nanosecond to picosecond pulse lasers were achieved at room temperature by the high gain operation in which pump intensities were beyond 100 kW/cm2.
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[The design of all solid-state tunable pulsed Ti:sapphire laser system].
Chen, Zhe; Ku, Geng; Wan, Junchao; Wang, Wei; Zhou, Chuanqing
2013-05-01
This paper presented a design of broadly all solid-state tunable pulsed Ti:sapphire laser with high power and stable performance. The laser was pumped by custom-made Nd:YAG laser which had water cooling system and amplified by two stage amplifier. The method accomplished tunable output of all solid-state tunable pulsed Ti:sapphire laser by modifying the reflection angle of the back mirror. We investigated the relationship between the power of the pumping laser and the all solid-state tunable pulsed Ti: sapphire laser by changing the power of the pumping source.
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Hosten, N; Stier, A; Weigel, C; Kirsch, M; Puls, R; Nerger, U; Jahn, D; Stroszczynski, C; Heidecke, C-D; Speck, U
2003-03-01
A thin-caliber applicator system was developed for introducing a laser fiber under CT guidance into lung metastases with only minimal complications. A space-saving 5.5 French Teflon cannula with a titanium trocar and connectors for a laser light guide (2 or 3 cm Dornier Diffusor-Tip H-6111-T2 or H-6111-T3 coupled to a Dornier Medilas Fibertom 5100 laser, wavelength of 1064 nm) and a perfusion line for physiologic saline solution were developed. After puncture the laser Diffusor-Tip remains in the cannula and is cooled during its tissue passage by slowly flowing saline solution. The miniaturized applicator system (Monocath) was calibrated in nonperfused bovine liver for maximum energy supply and necessary flow of the cooling saline solution in reference to a commercially available 9 French laser catheter with an 11.5 French inducer sheath (Power-Applicator). The new applicator system was used for treating lung metastases in 10 patients over a period of 21 months. The size of heat coagulation in bovine liver was 24 +/- 2 ml using the miniaturized system with application of 15 W for 20 min and a saline flow of 0.75 ml/min, in comparison to a size of 29 +/- 7 ml for the commercial applicator (30 W, 20 min, 60 ml/min). All metastases could be safely approached with the miniaturized applicator, except for two metastatic lesions at the lung base in two patients. A minor pneumothorax developed in three patients and intrapulmonary bleeding in two. Contrast-enhanced CT demonstrated necrosis of the treated metastatic areas in 6 patients. Follow-up of three patients after 5, 6, and 8 months showed complete tumor regression with minimal scarring in one patient. The miniaturized applicator system enables the introduction of a laser fiber into pulmonary metastases with only minor complications. Complete ablation seems to be achievable in suitable patients with the applied laser energy and a slow cooling fluid flow rate.
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Solid state optical refrigeration using stark manifold resonances in crystals
Seletskiy, Denis V.; Epstein, Richard; Hehlen, Markus P.; Sheik-Bahae, Mansoor
2017-02-21
A method and device for cooling electronics is disclosed. The device includes a doped crystal configured to resonate at a Stark manifold resonance capable of cooling the crystal to a temperature of from about 110K to about 170K. The crystal host resonates in response to input from an excitation laser tuned to exploit the Stark manifold resonance corresponding to the cooling of the crystal.
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Investigation of the Fermi-Hubbard model with 6Li in an optical lattice
NASA Astrophysics Data System (ADS)
Hart, R. A.; Duarte, P. M.; Yang, T.-L.; Hulet, R. G.
2013-05-01
We present our results on investigation of the physics of the Fermi-Hubbard model using an ultracold gas of 6Li loaded into an optical lattice. We use all-optical methods to efficiently cool and load the lattice beginning with laser cooling on the 2S1 / 2 --> 2P3 / 2 transition and then further cooling using the narrow 2S1 / 2 --> 3P3 / 2 transition to T ~ 59 μK. The second stage of laser cooling greatly enhances loading to an optical dipole trap where a two spin state mixture of atoms is evaporatively cooled to degeneracy. We then adiabatically load ~106 degenerate fermions into a 3D optical lattice formed by three orthogonal standing waves of 1064 nm light. Overlapped with each of the three lattice beams is a non-retroreflected beam at 532 nm. This light cancels the harmonic trapping caused by the lattice beams, which extends the number of lattice sites over which a Néel phase can exist and may allow evaporative cooling in the lattice. By using Bragg scattering of light, we investigate the possibility of observing long-range antiferromagnetic ordering of spins in the lattice. Supported by NSF, ONR, DARPA, and the Welch Foundation.
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Micron-size hydrogen cluster target for laser-driven proton acceleration
NASA Astrophysics Data System (ADS)
Jinno, S.; Kanasaki, M.; Uno, M.; Matsui, R.; Uesaka, M.; Kishimoto, Y.; Fukuda, Y.
2018-04-01
As a new laser-driven ion acceleration technique, we proposed a way to produce impurity-free, highly reproducible, and robust proton beams exceeding 100 MeV using a Coulomb explosion of micron-size hydrogen clusters. In this study, micron-size hydrogen clusters were generated by expanding the cooled high-pressure hydrogen gas into a vacuum via a conical nozzle connected to a solenoid valve cooled by a mechanical cryostat. The size distributions of the hydrogen clusters were evaluated by measuring the angular distribution of laser light scattered from the clusters. The data were analyzed mathematically based on the Mie scattering theory combined with the Tikhonov regularization method. The maximum size of the hydrogen cluster at 25 K and 6 MPa in the stagnation state was recognized to be 2.15 ± 0.10 μm. The mean cluster size decreased with increasing temperature, and was found to be much larger than that given by Hagena’s formula. This discrepancy suggests that the micron-size hydrogen clusters were formed by the atomization (spallation) of the liquid or supercritical fluid phase of hydrogen. In addition, the density profiles of the gas phase were evaluated for 25 to 80 K at 6 MPa using a Nomarski interferometer. Based on the measurement results and the equation of state for hydrogen, the cluster mass fraction was obtained. 3D particles-in-cell (PIC) simulations concerning the interaction processes of micron-size hydrogen clusters with high power laser pulses predicted the generation of protons exceeding 100 MeV and accelerating in a laser propagation direction via an anisotropic Coulomb explosion mechanism, thus demonstrating a future candidate in laser-driven proton sources for upcoming multi-petawatt lasers.
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Khoshnevis, Sepideh; Craik, Natalie K; Matthew Brothers, R; Diller, Kenneth R
2016-03-01
The goal of this study was to investigate the persistence of cold-induced vasoconstriction following cessation of active skin-surface cooling. This study demonstrates a hysteresis effect that develops between skin temperature and blood perfusion during the cooling and subsequent rewarming period. An Arctic Ice cryotherapy unit (CTU) was applied to the knee region of six healthy subjects for 60 min of active cooling followed by 120 min of passive rewarming. Multiple laser Doppler flowmetry perfusion probes were used to measure skin blood flow (expressed as cutaneous vascular conductance (CVC)). Skin surface cooling produced a significant reduction in CVC (P < 0.001) that persisted throughout the duration of the rewarming period. In addition, there was a hysteresis effect between CVC and skin temperature during the cooling and subsequent rewarming cycle (P < 0.01). Mixed model regression (MMR) showed a significant difference in the slopes of the CVC-skin temperature curves during cooling and rewarming (P < 0.001). Piecewise regression was used to investigate the temperature thresholds for acceleration of CVC during the cooling and rewarming periods. The two thresholds were shown to be significantly different (P = 0.003). The results show that localized cooling causes significant vasoconstriction that continues beyond the active cooling period despite skin temperatures returning toward baseline values. The significant and persistent reduction in skin perfusion may contribute to nonfreezing cold injury (NFCI) associated with cryotherapy.
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Khoshnevis, Sepideh; Craik, Natalie K.; Matthew Brothers, R.; Diller, Kenneth R.
2016-01-01
The goal of this study was to investigate the persistence of cold-induced vasoconstriction following cessation of active skin-surface cooling. This study demonstrates a hysteresis effect that develops between skin temperature and blood perfusion during the cooling and subsequent rewarming period. An Arctic Ice cryotherapy unit (CTU) was applied to the knee region of six healthy subjects for 60 min of active cooling followed by 120 min of passive rewarming. Multiple laser Doppler flowmetry perfusion probes were used to measure skin blood flow (expressed as cutaneous vascular conductance (CVC)). Skin surface cooling produced a significant reduction in CVC (P < 0.001) that persisted throughout the duration of the rewarming period. In addition, there was a hysteresis effect between CVC and skin temperature during the cooling and subsequent rewarming cycle (P < 0.01). Mixed model regression (MMR) showed a significant difference in the slopes of the CVC–skin temperature curves during cooling and rewarming (P < 0.001). Piecewise regression was used to investigate the temperature thresholds for acceleration of CVC during the cooling and rewarming periods. The two thresholds were shown to be significantly different (P = 0.003). The results show that localized cooling causes significant vasoconstriction that continues beyond the active cooling period despite skin temperatures returning toward baseline values. The significant and persistent reduction in skin perfusion may contribute to nonfreezing cold injury (NFCI) associated with cryotherapy. PMID:26632263
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Preclinical Assessment of a 980-nm Diode Laser Ablation System in a Large Animal Tumor Model
Ahrar, Kamran; Gowda, Ashok; Javadi, Sanaz; Borne, Agatha; Fox, Matthew; McNichols, Roger; Ahrar, Judy U.; Stephens, Clifton; Stafford, R. Jason
2010-01-01
Purpose To characterize the performance of a 980-nm diode laser ablation system in an in vivo tumor model. Materials and Methods This study was approved by the Institutional Animal Care and Use Committee. The ablation system consisted of a 15-W, 980-nm diode laser, flexible diffusing tipped fiber optic, and 17-gauge internally cooled catheter. Ten immunosuppressed dogs were inoculated subcutaneously with canine transmissible venereal tumor fragments in eight dorsal locations. Laser ablations were performed at 79 sites where inoculations were successful (99%) using powers of 10 W, 12.5 W, and 15 W, with exposure times between 60 and 180 seconds. In 20 cases, multiple overlapping ablations were performed. After the dogs were euthanized, the tumors were harvested, sectioned along the applicator track, measured and photographed. Measurements of ablation zone were performed on gross specimen. Histopathology and viability staining was performed using hematoxylin and eosin (H&E) and nicotinamide adenine dinucleotide hydrogen (NADH) staining. Results Gross pathology confirmed well-circumscribed ablation zone with sharp boundaries between thermally ablated tumor in the center surrounded by viable tumor tissue. When a single applicator was used, the greatest ablation diameters ranged from 12 mm at the lowest dose (10 W, 60 sec) to 26 mm at the highest dose (15 W, 180 sec). Multiple applicators created ablation zones of up to 42 mm in greatest diameter (with the lasers operating at 15 W for 120 sec). Conclusions The new 980-nm diode laser and internally cooled applicator effectively creates large ellipsoid thermal ablations in less than 3 minutes. PMID:20346883
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Alq3 coated silicon nanomembranes for cavity optomechanics
NASA Astrophysics Data System (ADS)
Fogliano, Francesco; Ortu, Antonio; Camposeo, Andrea; Pisignano, Dario; Ciampini, Donatella; Fuso, Francesco; Arimondo, E.
2016-09-01
The optomechanical properties of a silicon-nitride membrane mirror covered by Alq3 and Silver layers are investigated. Excitation at two laser wavelengths, 780 and 405 nm, corresponding to different absorptions of the multilayer, is examined. Such dual driving will lead to a more flexible optomechanical operation. Topographic reconstruction of the whole static membrane deformation and cooling of the membrane oscillations are reported. The cooling, observed for blue laser detuning and produced by bolometric forces, is deduced from the optomechanical damping of the membrane eigenfrequency. We determine the presence of different contributions to the photothermal response of the membrane.
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NASA Astrophysics Data System (ADS)
Stroke, H. Henry; Linnartz, Harold
2012-04-01
Comments on Atomic, Molecular and Optical Physics (CAMOP) endeavors periodically to devote an issue to the life and accomplishments of physicists who have made significant contributions to the fields represented in this journal. Vladilen Letokhov is certainly one of them. For a number of years he was also a CAMOP Correspondent. We are grateful to Professor Victor Balykin for having organized this CAMOP special section. It is particularly significant to one of us (HHS) to remember a person who has made seminal advances in so many areas which to this day are at the forefront of studies by a number of physicists. But over the years this acquaintance developed into friendship and gave the wife of one of us, Norma, and HHS the opportunity to host Tina and Vladik in their home, and get to know both a bit better. There was also the seminal International School on Laser Applications in Physics in Vilnius organized by Letokhov, and then a visit to Troitsk and his group at the Institute of Spectroscopy (and even the organization of a couple of piano recitals by one of our daughters, Marija, who accompanied her parents in the then USSR). Our interests crossed in a couple of fields: laser interactions with atoms and sensitive spectroscopy of radioactive atoms. Letokhov was a participant in the early organization of laser spectroscopy at CERN and was instrumental in providing copper vapour lasers to the isotope separator facility, ISOLDE. To this day laser ion sources are under the aegis of Valentin Fedoseyev who came to CERN from Troitsk. The interaction of lasers with atoms, in particular the process of slowing atoms, is discussed by Balykin. It was Christmas time when a card arrived from Oleg Tumanov of the Institute of Spectroscopy: it included a graph of temperature achieved by laser cooling as a function of calendar date. The results of Letokhov's group were the earliest (see figure 1), even though lower temperatures achieved subsequently by others extended our knowledge. To many, the lack of formal recognition was a bit puzzling, and this will have to await the usual number of decades before relevant discussions become publicSee, for example, Friedman R M 2001 The Politics of Excellence (New York: Henry Holt).. But, as can be attested by the most prolific, diverse and creative contributions presented in the bibliography, Letokhov's work will leave a long-lasting legacy. Progress in laser cooling Figure 1. Progress in laser cooling.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Raja, R. Subramaniyan; Babu, G. Anandha; Ramasamy, P., E-mail: E-mail-ramasamyp@ssn.edu.in
2016-05-23
Good quality single crystals of pure hydrocarbon 1,3,5-Triphenylbenzene (TPB) have been successfully grown using toluene as a solvent using controlled slow cooling solution growth technique. TPB crystallizes in orthorhombic structure with the space group Pna2{sub 1}. The structural perfection of the grown crystal has been analysed by high resolution X-ray diffraction measurements. The range and percentage of the optical transmission are ascertained by recording the UV-vis spectrum. Thermo gravimetric analysis (TGA) and differential thermal analysis (DTA) were used to study its thermal properties. Powder second harmonic generation studies were carried out to explore its NLO properties. Laser damage threshold valuemore » has been determined using Nd:YAG laser operating at 1064 nm.« less
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High energy diode-pumped solid-state laser development at the Central Laser Facility
NASA Astrophysics Data System (ADS)
Mason, Paul D.; Banerjee, Saumyabrata; Ertel, Klaus; Phillips, P. Jonathan; Butcher, Thomas; Smith, Jodie; De Vido, Mariastefania; Chekhlov, Oleg; Hernandez-Gomez, Cristina; Edwards, Chris; Collier, John
2016-04-01
In this paper we review the development of high energy, nanosecond pulsed diode-pumped solid state lasers within the Central Laser Facility (CLF) based on cryogenic gas cooled multi-slab ceramic Yb:YAG amplifier technology. To date two 10J-scale systems, the DiPOLE prototype amplifier and an improved DIPOLE10 system, have been developed, and most recently a larger scale system, DiPOLE100, designed to produce 100 J pulses at up to 10 Hz. These systems have demonstrated amplification of 10 ns duration pulses at 1030 nm to energies in excess of 10 J at 10 Hz pulse repetition rate, and over 100 J at 1 Hz, with optical-to-optical conversion efficiencies of up to 27%. We present an overview of the cryo-amplifier concept and compare the design features of these three systems, including details of the amplifier designs, gain media, diode pump lasers and the cryogenic gas cooling systems. The most recent performance results from the three systems are presented along with future plans for high energy DPSSL development within the CLF.
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Laser for high frequency modulated interferometry
Mansfield, D.K.; Vocaturo, M.; Guttadora, L.J.
1991-07-23
A Stark-tuned laser operating in the 119 micron line of CH[sub 3]OH has an output power of several tens of milliwatts at 30 Watts of pump power while exhibiting a doublet splitting of about ten MHz with the application of a Stark field on the order of 500 volts/cm. This output power allows for use of the laser in a multi-channel interferometer, while its high operating frequency permits the interferometer to measure rapid electron density changes in a pellet injected or otherwise fueled plasma such as encountered in magnetic fusion devices. The laser includes a long far-infrared (FIR) pyrex resonator tube disposed within a cylindrical water jacket and incorporating charged electrodes for applying the Stark field to a gas confined therein. With the electrodes located within the resonator tube, the resonator tube walls are cooled by a flowing coolant without electrical breakdown in the coolant liquid during application of the Stark field. Wall cooling allows for substantially increased FIR output powers. Provision is made for introducing a buffer gas into the resonator tube for increasing laser output power and its operating bandwidth. 10 figures.
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Laser for high frequency modulated interferometry
Mansfield, Dennis K.; Vocaturo, Michael; Guttadora, Lawrence J.
1991-01-01
A Stark-tuned laser operating in the 119 micron line of CH.sub.3 OH has an output power of several tens of milliwatts at 30 Watts of pump power while exhibiting a doublet splitting of about ten MHz with the application of a Stark field on the order of 500 volts/cm. This output power allows for use of the laser in a multi-channel interferometer, while its high operating frequency permits the interferometer to measure rapid electron density changes in a pellet injected or otherwise fueled plasma such as encountered in magnetic fusion devices. The laser includes a long far-infrared (FIR) pyrex resonator tube disposed within a cylindrical water jacket and incorporating charged electrodes for applying the Stark field to a gas confined therein. With the electrodes located within the resonator tube, the resonator tube walls are cooled by a flowing coolant without electrical breakdown in the coolant liquid during application of the Stark field. Wall cooling allows for substantially increased FIR output powers. Provision is made for introducing a buffer gas into the resonator tube for increasing laser output power and its operating bandwidth.
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Effect of Heat Treatment on the Properties of CoCrMo Alloy Manufactured by Selective Laser Melting
NASA Astrophysics Data System (ADS)
Guoqing, Zhang; Junxin, Li; Xiaoyu, Zhou; Jin, Li; Anmin, Wang
2018-04-01
To obtain medical implants with better mechanical properties, it is necessary to conduct studies on the heat treatment process of the selective laser melting (SLM) manufacturing parts. The differential scanning calorimetry method was used to study the heat treatment process of the phase transition of SLM CoCrMo alloy parts. The tensile properties were tested with a tensile test machine, the quantity of carbide precipitated after heat treatment was measured by energy-dispersive x-ray spectroscopy, and the tensile fracture morphology of the parts was investigated using SEM. The obtained results were: Mechanical properties in terms of elongation and tensile strength of CoCrMo alloy manufactured by SLM that had been heat-treated at 1200 °C for 2 h followed by cooling with water were not only higher than the national standard but also higher than the experimental results of the same batch of castings. The mechanism of fracture of parts manufactured by SLM without heat treatment was brittle fracture, whereas parts which had been heat-treated at 1200 °C for 2 h combined with water cooling and at 1200 °C for 1 h with furnace cooling suffered ductile fracture. This study provides the basis for defining the applications for which CoCrMo alloys manufactured by SLM are suitable within the field of medical implants.
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Effect of Heat Treatment on the Properties of CoCrMo Alloy Manufactured by Selective Laser Melting
NASA Astrophysics Data System (ADS)
Guoqing, Zhang; Junxin, Li; Xiaoyu, Zhou; Jin, Li; Anmin, Wang
2018-05-01
To obtain medical implants with better mechanical properties, it is necessary to conduct studies on the heat treatment process of the selective laser melting (SLM) manufacturing parts. The differential scanning calorimetry method was used to study the heat treatment process of the phase transition of SLM CoCrMo alloy parts. The tensile properties were tested with a tensile test machine, the quantity of carbide precipitated after heat treatment was measured by energy-dispersive x-ray spectroscopy, and the tensile fracture morphology of the parts was investigated using SEM. The obtained results were: Mechanical properties in terms of elongation and tensile strength of CoCrMo alloy manufactured by SLM that had been heat-treated at 1200 °C for 2 h followed by cooling with water were not only higher than the national standard but also higher than the experimental results of the same batch of castings. The mechanism of fracture of parts manufactured by SLM without heat treatment was brittle fracture, whereas parts which had been heat-treated at 1200 °C for 2 h combined with water cooling and at 1200 °C for 1 h with furnace cooling suffered ductile fracture. This study provides the basis for defining the applications for which CoCrMo alloys manufactured by SLM are suitable within the field of medical implants.
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Three-dimensional laser cooling at the Doppler limit
NASA Astrophysics Data System (ADS)
Chang, R.; Hoendervanger, A. L.; Bouton, Q.; Fang, Y.; Klafka, T.; Audo, K.; Aspect, A.; Westbrook, C. I.; Clément, D.
2014-12-01
Many predictions of Doppler-cooling theory of two-level atoms have never been verified in a three-dimensional geometry, including the celebrated minimum achievable temperature ℏ Γ /2 kB , where Γ is the transition linewidth. Here we show that, despite their degenerate level structure, we can use helium-4 atoms to achieve a situation in which these predictions can be verified. We make measurements of atomic temperatures, magneto-optical trap sizes, and the sensitivity of optical molasses to a power imbalance in the laser beams, finding excellent agreement with Doppler theory. We show that the special properties of helium, particularly its small mass and narrow transition linewidth, prevent effective sub-Doppler cooling with red-detuned optical molasses. This discussion can be generalized to identify when a given species is likely to be subject to the same limitation.
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NASA Astrophysics Data System (ADS)
Wang, Boxue; Jia, Yangtao; Zhang, Haoyu; Jia, Shiyin; Liu, Jindou; Wang, Weifeng; Liu, Xingsheng
2018-02-01
An insulation micro-channel cooling (IMCC) has been developed for packaging high power bar-based vertical stack and horizontal array diode lasers, which eliminates many issues caused in its congener packaged by commercial copper formed micro-channel cooler(MCC), such as coefficient of thermal expansion (CTE) mismatch between cooler and diode laser bar, high coolant quality requirement (DI water) and channel corrosion and electro-corrosion induced by DI water if the DI-water quality is not well maintained The IMCC cooler separates water flow route and electrical route, which allows tap-water as coolant without electro-corrosion and therefore prolongs cooler lifetime dramatically and escalated the reliability of these diode lasers. The thickness of ceramic and copper in an IMCC cooler is well designed to minimize the CTE mismatch between laser bar and cooler, consequently, a very low "SMILE" of the laser bar can be achieved for small fast axis divergence after collimation. In additional, gold-tin hard solder bonding technology was also developed to minimize the risk of solder electromigration at high current density and thermal fatigue under hard-pulse operation mode. Testing results of IMCC packaged diode lasers are presented in this report.
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Optical Cooling in Er3+:KPb2Cl5
2009-01-01
and C. .E. Mungan, “Observation of laser- induced fluorescent cooling of a solid,” Nature 377, 500-503 (1995). 4. C. W. Hoyt, M. Sheik- Bahae , R. I ...cooling by spontaneous anti-Stokes scattering,” Phys. Rev. Lett. 46, 236-239 (1981). 3. R. I . Epstein, M. I . Buchwald, B. C. Edwards, T. R. Gosnell...2000). 5. S. R. Bowman and C. E. Mungan, “New materials for optical cooling,” Appl. Phys. B 71, 807-811 (2000). 6. R. I . Epstein, J. J. Brown, B. C
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Solid-state optical refrigeration to sub-100 Kelvin regime
DOE Office of Scientific and Technical Information (OSTI.GOV)
Melgaard, Seth D.; Albrecht, Alexander R.; Hehlen, Markus P.
We report that since the first demonstration of net cooling twenty years ago, optical refrigeration of solids has progressed to outperform all other solid-state cooling processes. It has become the first and only solid-state refrigerator capable of reaching cryogenic temperatures, and now the first solid-state cooling below 100 K. Such substantial progress required a multi-disciplinary approach of pump laser absorption enhancement, material characterization and purification, and thermal management. Here we present the culmination of two decades of progress, the record cooling to ≈91K from room temperature.
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Solid-state optical refrigeration to sub-100 Kelvin regime
Melgaard, Seth D.; Albrecht, Alexander R.; Hehlen, Markus P.; ...
2016-02-05
We report that since the first demonstration of net cooling twenty years ago, optical refrigeration of solids has progressed to outperform all other solid-state cooling processes. It has become the first and only solid-state refrigerator capable of reaching cryogenic temperatures, and now the first solid-state cooling below 100 K. Such substantial progress required a multi-disciplinary approach of pump laser absorption enhancement, material characterization and purification, and thermal management. Here we present the culmination of two decades of progress, the record cooling to ≈91K from room temperature.
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Solid-state optical refrigeration to sub-100 Kelvin regime
Melgaard, Seth D.; Albrecht, Alexander R.; Hehlen, Markus P.; Sheik-Bahae, Mansoor
2016-01-01
Since the first demonstration of net cooling twenty years ago, optical refrigeration of solids has progressed to outperform all other solid-state cooling processes. It has become the first and only solid-state refrigerator capable of reaching cryogenic temperatures, and now the first solid-state cooling below 100 K. Such substantial progress required a multi-disciplinary approach of pump laser absorption enhancement, material characterization and purification, and thermal management. Here we present the culmination of two decades of progress, the record cooling to ≈ 91 K from room temperature. PMID:26847703
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Static Mixer for Heat Transfer Enhancement for Mold Cooling Application
NASA Astrophysics Data System (ADS)
Becerra, Rodolfo; Barbosa, Raul; Lee, Kye-Hwan; Park, Younggil
Injection molding is the process by which a material is melted in a barrel and then it is injected through a nozzle in the mold cavity. When it cools down, the material solidifies into the shape of the cavity. Typical injection mold has cooling channels to maintain constant mold temperature during injection molding process. Even and constant temperature throughout the mold are very critical for a part quality and productivity. Conformal cooling improves the quality and productivity of injection molding process through the implementation of cooling channels that ``conform'' to the shape of the molded part. Recent years, the use of conformal cooling increases with advance of 3D printing technology such as Selective Laser Melting (SLM). Although it maximizes cooling, material and dimension limitations make SLM methods highly expensive. An alternative is the addition of static mixers in the molds with integrated cooling channels. A static mixer is a motionless mixing device that enhances heat transfer by producing improved flow mixing in the pipeline. In this study, the performance of the cooling channels will be evaluated with and without static mixers, by measuring temperature, pressure drop, and flow rate. The following question is addressed: Can a static mixer effectively enhance heat transfer for mold cooling application processes? This will provide insight on the development of design methods and guidelines that can be used to increase cooling efficiency at a lower cost.
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NASA Astrophysics Data System (ADS)
Su, Rui; Mironov, Andrey; Houlahan, Thomas, Jr.; Eden, J. Gary; LaboratoryOptical Physics; Engineering Team
2016-09-01
Laser-induced fluorescence (LIF) resulting from transitions between different electronic states of helium dimers generated within a microcavity plasma jet was studied with rotational resolution. In particular, the d3Σu+ , e3Πg and f3Σu+ states, all having electronic energies above 24 eV, are populated by a microplasma in 4 bar of helium gas and rotationally cooled through supersonic expansion. Analysis of two dimensional maps (spectrograms) of dimer emission spectra as a function of distance from the nozzle orifice indicates collisional coupling during the expansion between the lowest rotational levels of the e3Πg , f3Σu+ states and high rotational levels (around N=11) of the d3Σu+ state (all of which are in the v = 0 vibrational state). In an attempt to verify the coupling, a scanning dye laser (centered near 596 nm) pumps the b3Πg -> f3Σu+ transition of the molecule several hundred micrometers downstream of the nozzle. As a result, the emission intensities of relevant rotational lines are observed to be enhanced. This research shows the potential of utilizing microcavity plasma jets as a tool to study and manipulate the collisional dynamics of highly-excited diatomic molecules.
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Novel high-energy physics studies using intense lasers and plasmas
DOE Office of Scientific and Technical Information (OSTI.GOV)
Leemans, Wim P.; Bulanov, Stepan; Esarey, Eric
2015-06-29
In the framework of the project “Novel high-energy physics studies using intense lasers and plasmas” we conducted the study of ion acceleration and “flying mirrors” with high intensity lasers in order to develop sources of ion beams and high frequency radiation for different applications. Since some schemes of laser ion acceleration are also considered a good source of “flying mirrors”, we proposed to investigate the mechanisms of “mirror” formation. As a result we were able to study the laser ion acceleration from thin foils and near critical density targets. We identified several fundamental factors limiting the acceleration in the RPAmore » regime and proposed the target design to compensate these limitations. In the case of near critical density targets, we developed a concept for the laser driven ion source for the hadron therapy. Also we studied the mechanism of “flying mirror” generation during the intense laser interaction with thin solid density targets. As for the laser-based positron creation and capture we initially proposed to study different regimes of positron beam generation and positron beam cooling. Since the for some of these schemes a good quality electron beam is required, we studied the generation of ultra-low emittance electron beams. In order to understand the fundamental physics of high energy electron beam interaction with high intensity laser pulses, which may affect the efficient generation of positron beams, we studied the radiation reaction effects.« less
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Cryogenic Tm:YAP microchip laser
NASA Astrophysics Data System (ADS)
Hubka, Zbyněk.; Å ulc, Jan; Jelínková, Helena; Nejezchleb, Karel; Å koda, Václav
2016-04-01
The spectral characteristics of laser active media, and thus those of the laser output, are temperature dependent. Specifically, in almost every crystal host, cooling to low temperatures leads to better heat removal, a higher efficiency and output power, and a reduced lasing threshold. Tm-ion doped lasers have an emission wavelength around 2 μm and are important in medicine for soft tissue cutting and hemostasis, as well as in LIDAR or atmosphere sensing technology. This paper presents the performance-temperature dependency of a 4 at. % doped Tm:YAP microchip. During the experiment the Tm:YAP crystal was placed inside an evacuated liquid nitrogen cryostat on a cooling finger. As its temperature was varied from 80 K to 340 K, changes were observed in the absorption spectrum, ranging from 750 nm to 2000 nm and in the fluorescence spectrum from 1600 nm to 2050 nm. Fluorescence lifetime was seen to rise and fall with decreasing temperature. The laser was pumped by a 792 nm laser diode and at 80 K the maximum output peak power of the laser was 4.6 W with 23 % slope efficiency and 0.6 W threshold, compared to 2.4 W output peak power, 13 % slope efficiency and 3.3 W threshold when at 340 K. The laser emission wavelength changed from 1883 nm to 1993 nm for 80 K and 300 K, respectively.
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NASA Astrophysics Data System (ADS)
Karwi, Abbas Ali Mahmmod
2018-04-01
Laser has many attractive specifications which made it adaptable for material processing. Laser has been taken as a modern heat treatment source to prevent the formation of non-protective oxide layer with intensity equals to (1.31×105 w/cm2), lasing time equals to (300 µs), wave length equals to (1.063 µm), and the spot radius equals to (125 µm). Lithium is depleted through the conventional heat treatment processes. The main factors affected on lithium depletion are temperature and time. Lithium kept as a solid solution at casting method. Micro hardness of the affected zone reaches to acceptable values for various ageing times and hardening depths. The main conventional heat treatment processes are; homogenization, solution heat treatment, and ageing. Alloys prepared with the specific amounts of lithium concentration (2-2.5%). Oxides with different shapes are formed. Temperature distribution, heating, and cooling rates used externally and internally to see the effect of pulse generation by laser on bulk body.
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Laser welding process in PP moulding parts: Evaluation of seam performance
NASA Astrophysics Data System (ADS)
Oliveira, N.; Pontes, A. J.
2015-12-01
The Polypropylene is one of the most versatile polymer materials used in the industry. Due to this versatility, it is possible to use it in different products. This material can also be mixed with several additives namely glass fiber, carbon nanotubes, etc. This compatibility with different additives allows also obtaining products with characteristics that goes from an impact absorber to an electricity conductor. When is necessary to join components in PP they could be welded through hot plate, ultrasonic weld and also by laser. This study had the objective of study the influence of several variables, capable of influence the final quality of the seam. In this case were studied variables of the injection molding process as mold temperature and cooling time. Was also studied laser welding variables and different materials. The results showed that the variables that have the most influence were mould temperature, laser velocity and laser diameter. The seams were analyzed using Optical Microscopy technique. The seams showed perfect contact between the materials analyzed, despite the high standard variation presented in the mechanical testes.
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A novel experimental system of high stability and lifetime for the laser-desorption of biomolecules.
Taherkhani, Mehran; Riese, Mikko; BenYezzar, Mohammed; Müller-Dethlefs, Klaus
2010-06-01
A novel laser desorption system, with improved signal stability and extraordinary long lifetime, is presented for the study of jet-cooled biomolecules in the gas phase using vibrationally resolved photoionization spectroscopy. As a test substance tryptophane is used to characterize this desorption source. A usable lifetime of above 1 month (for a laser desorption repetition rate of 20 Hz) has been observed by optimizing the pellets (graphite/tryptophane, 3 mm diameter and 6 mm length) from which the substance is laser-desorbed. Additionally, the stability and signal-to-noise ratio has been improved by averaging the signal over the entire sample pellet by synchronizing the data acquisition with the rotation of the sample rod. The results demonstrate how a combination of the above helps to produce stable and conclusive spectra of tryptophane using one-color and two-color resonant two-photon ionization studies.
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Some recent studies on laser cladding and dissimilar welding
NASA Astrophysics Data System (ADS)
Kaul, Rakesh; Ganesh, P.; Paul, C. P.; Albert, S. K.; Mudali, U. Kamachi; Nath, A. K.
2006-01-01
Indigenous development of high power CO II laser technology and industrial application of lasers represent two important mandates of the laser program, being pursued at Centre for Advanced Technology (CAT), India. The present paper describes some of the important laser material processing studies, involving cladding and dissimilar welding, performed in authors' laboratory. The first case study describes how low heat input characteristics of laser cladding process has been successfully exploited for suppressing dilution in "Colmonoy6" (a nickel-base hardfacing alloy) deposits on austenitic stainless steel components. Crack free hardfaced deposits were obtained by controlling heating and cooling rates associated with laser treatment. The results show significant advantage over Colmonoy 6 deposits made by GTAW, where a 2.5 mm thick region of dilution (with reduced hardness) develops next to substrateiclad interface. The next work involves laser-assisted deposition of graded "Stellite6" (a Co-base hardfacing alloy) with smooth transition in chemical composition and hardness for enhanced resistance against cracking, esp. under thermal cycling conditions. The following two case studies demonstrate significant improvement in corrosion properties of type 304L stainless steel by laser surface alloying, achieved through cladding route. The following case study demonstrates engineering of fusion zone microstructure of end plug dissimilar weld (between alloy D9 and type 3 16M stainless steel) by controlled preferential displacement of focused laser beam, which, in-turn, enhanced its resistance against solidification cracking. Crater appearing at the termination point of laser weld is also eliminated by ramping of laser power towards the end of laser welding. The last case study involves engineering of fusion zone microstructure of dissimilar laser weld between type 304 austenitic stainless steel and stabilized 17%Cr ferritic stainless steel by controlling welding parameters.
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NASA Astrophysics Data System (ADS)
Shan, Ning; Wang, Zhijing; Liu, Xia
2014-11-01
Laser is widely applied in military and medicine fields because of its excellent capability. In order to effectively defend excess damage by laser, the thermal processing theory of skin tissue generated by laser should be carried out. The heating rate and thermal damage area should be studied. The mathematics model of bio-tissue heat transfer that is irradiated by laser is analyzed. And boundary conditions of bio-tissue are discussed. Three layer FEM grid model of bio-tissue is established. The temperature rising inducing by pulse laser in the tissue is modeled numerically by adopting ANSYS software. The changing trend of temperature in the tissue is imitated and studied under the conditions of different exposure dose pulse laser. The results show that temperature rising in the tissue depends on the parameters of pulse laser largely. In the same conditions, the pulse width of laser is smaller and its instant power is higher. And temperature rising effect in the tissue is very clear. On the contrary, temperature rising effect in the tissue is lower. The cooling time inducing by temperature rising effect in the tissue is longer along with pulse separation of laser is bigger. And the temperature difference is bigger in the pulse period.
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High-power diode-side-pumped rod Tm:YAG laser at 2.07 μm.
Wang, Caili; Niu, Yanxiong; Du, Shifeng; Zhang, Chao; Wang, Zhichao; Li, Fangqin; Xu, Jialin; Bo, Yong; Peng, Qinjun; Cui, Dafu; Zhang, Jingyuan; Xu, Zuyan
2013-11-01
We report a high-power diode-laser (LD) side-pumped rod Tm:YAG laser of around 2 μm. The laser was water-cooled at 8°C and yielded a maximum output power of 267 W at 2.07 μm, which is the highest output power for an all solid-state cw 2.07 μm rod Tm:YAG laser reported as far as we know. The corresponding optical-optical conversion efficiency was 20.7%, and the slope efficiency was about 29.8%, respectively.
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Scalable Loading of a Two-Dimensional Trapped-Ion Array
2015-11-25
ion -trap array based on two crossed photo-ionization laser beams . With the use of a continuous flux of pre-cooled neutral...push laser Atomic beam Dierential pumping tube Push laser 2D-MOT 50 K Shield 4 K Shield 4 K stage Trap chip MOT laser Ion To ion pump 5s2 1S0 461...conducted a series of Ramsey experiments on a single trapped ion in the presence and absence of neu- tral atom flux as well as each of the PI laser
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A Transportable Gravity Gradiometer Based on Atom Interferometry
NASA Technical Reports Server (NTRS)
Yu, Nan; Thompson, Robert J.; Kellogg, James R.; Aveline, David C.; Maleki, Lute; Kohel, James M.
2010-01-01
A transportable atom interferometer-based gravity gradiometer has been developed at JPL to carry out measurements of Earth's gravity field at ever finer spatial resolutions, and to facilitate high-resolution monitoring of temporal variations in the gravity field from ground- and flight-based platforms. Existing satellite-based gravity missions such as CHAMP and GRACE measure the gravity field via precise monitoring of the motion of the satellites; i.e. the satellites themselves function as test masses. JPL's quantum gravity gradiometer employs a quantum phase measurement technique, similar to that employed in atomic clocks, made possible by recent advances in laser cooling and manipulation of atoms. This measurement technique is based on atomwave interferometry, and individual laser-cooled atoms are used as drag-free test masses. The quantum gravity gradiometer employs two identical atom interferometers as precision accelerometers to measure the difference in gravitational acceleration between two points (Figure 1). By using the same lasers for the manipulation of atoms in both interferometers, the accelerometers have a common reference frame and non-inertial accelerations are effectively rejected as common mode noise in the differential measurement of the gravity gradient. As a result, the dual atom interferometer-based gravity gradiometer allows gravity measurements on a moving platform, while achieving the same long-term stability of the best atomic clocks. In the laboratory-based prototype (Figure 2), the cesium atoms used in each atom interferometer are initially collected and cooled in two separate magneto-optic traps (MOTs). Each MOT, consisting of three orthogonal pairs of counter-propagating laser beams centered on a quadrupole magnetic field, collects up to 10(exp 9) atoms. These atoms are then launched vertically as in an atom fountain by switching off the magnetic field and introducing a slight frequency shift between pairs of lasers to create a moving rest frame for the trapped atoms. While still in this moving-frame molasses, the laser frequencies are further detuned from the atomic resonance (while maintaining this relative frequency shift) to cool the atom cloud's temperature to 2 K or below, corresponding to an rms velocity of less than 2 cm/s. After launch, the cold atoms undergo further state and velocity selection to prepare for atom interferometry. The atom interferometers are then realized using laser-induced stimulated Raman transitions to perform the necessary manipulations of each atom, and the resulting interferometer phase is measured using laser-induced fluorescence for state-normalized detection. More than 20 laser beams with independent controls of frequency, phase, and intensity are required for this measurement sequence. This instrument can facilitate the study of Earth's gravitational field from surface and air vehicles, as well as from space by allowing gravity mapping from a low-cost, single spacecraft mission. In addition, the operation of atom interferometer-based instruments in space offers greater sensitivity than is possible in terrestrial instruments due to the much longer interrogation times available in the microgravity environment. A space-based quantum gravity gradiometer has the potential to achieve sensitivities similar to the GRACE mission at long spatial wavelengths, and will also have resolution similar to GOCE for measurement at shorter length scales.
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Development of Weld Metal Microstructures in Pulsed Laser Welding of Duplex Stainless Steel
NASA Astrophysics Data System (ADS)
Mirakhorli, F.; Malek Ghaini, F.; Torkamany, M. J.
2012-10-01
The microstructure of the weld metal of a duplex stainless steel made with Nd:YAG pulsed laser is investigated at different travel speeds and pulse frequencies. In terms of the solidification pattern, the weld microstructure is shown to be composed of two distinct zones. The presence of two competing heat transfer channels to the relatively cooler base metal and the relatively hotter previous weld spot is proposed to develop two zones. At high overlapping factors, an array of continuous axial grains at the weld centerline is formed. At low overlapping factors, in the zone of higher cooling rate, a higher percentage of ferrite is transformed to austenite. This is shown to be because with extreme cooling rates involved in pulsed laser welding with low overlapping, the ferrite-to-austenite transformation can be limited only to the grain boundaries.
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Lewicki, Rafał; Doty, James H.; Curl, Robert F.; Tittel, Frank K.; Wysocki, Gerard
2009-01-01
A transportable prototype Faraday rotation spectroscopic system based on a tunable external cavity quantum cascade laser has been developed for ultrasensitive detection of nitric oxide (NO). A broadly tunable laser source allows targeting the optimum Q3/2(3/2) molecular transition at 1875.81 cm−1 of the NO fundamental band. For an active optical path of 44 cm and 1-s lock-in time constant minimum NO detection limits (1σ) of 4.3 parts per billion by volume (ppbv) and 0.38 ppbv are obtained by using a thermoelectrically cooled mercury–cadmium–telluride photodetector and liquid nitrogen-cooled indium–antimonide photodetector, respectively. Laboratory performance evaluation and results of continuous, unattended monitoring of atmospheric NO concentration levels are reported. PMID:19625625
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Simulation and Preliminary Design of a Cold Stream Experiment on Omega EP
NASA Astrophysics Data System (ADS)
Coffing, Shane; Angulo, Adrianna; Trantham, Matt; Malamud, Guy; Kuranz, Carolyn; Drake, R. P.
2017-10-01
Galaxies form within dark matter halos, accreting gas that may clump and eventually form stars. Infalling matter gradually increases the density of the halo, and, if cooling is insufficient, rising pressure forms a shock that slows the infalling gas, reducing star formation. However, galaxies with sufficient cooling become prolific star formers. A recent theory suggests that so called ``stream fed galaxies'' are able to acquire steady streams of cold gas via galactic ``filaments'' that penetrate the halo. The cold, dense filament flowing into a hot, less dense environment is potentially Kelvin-Helmholtz unstable. This instability may hinder the ability of the stream to deliver gas deeply enough into the halo. To study this process, we have begun preliminary design of a well-scaled laser experiment on Omega EP. We present here early simulation results and the physics involved. This work is funded by the U.S. Department of Energy, through the NNSA-DS and SC-OFES Joint Program in High-Energy-Density Laboratory Plasmas, Grant Number DE-NA0002956, and the National Laser User Facility Program, Grant Number DE-NA0002719, and through the Laboratory for Laser Energetics, University of Rochester by the NNSA/OICF under Cooperative Agreement No. DE-NA0001944.
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Laser system for natural gas detection. Phase 1: Laboratory feasibility studies
NASA Technical Reports Server (NTRS)
Grant, W. B.; Hinkley, E. D., Jr.
1982-01-01
This project demonstrated the feasibility of using laser remote sensing technology as a tool for leak survey work in natural gas distribution systems. A laboratory device was assembled using a pair of helium neon (HeNe) lasers to measure methane. One HeNe laser emits radiation at a wavelength of 3.3922 micrometers, which corresponds to a strong absorption feature of methane, while the other emits radiation at a wavelength of 3.3911 micrometers, which corresponds to a weak absorption by methane. As a particular area is scanned for leaks, the laser is pointed at convenient topographic targets within its operating range, about 25 m. A portion of the backscattered radiation is collected by a receiver and focused onto an indium antimonide (InSb) photodetector, cooled to 77K. Methane concentrations were determined from the differential absorption at the two wavelengths for the backscattered radiation.
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QED cascade saturation in extreme high fields.
Luo, Wen; Liu, Wei-Yuan; Yuan, Tao; Chen, Min; Yu, Ji-Ye; Li, Fei-Yu; Del Sorbo, D; Ridgers, C P; Sheng, Zheng-Ming
2018-05-30
Upcoming ultrahigh power lasers at 10 PW level will make it possible to experimentally explore electron-positron (e - e + ) pair cascades and subsequent relativistic e - e + jets formation, which are supposed to occur in extreme astrophysical environments, such as black holes, pulsars, quasars and gamma-ray bursts. In the latter case it is a long-standing question as to how the relativistic jets are formed and what their temperatures and compositions are. Here we report simulation results of pair cascades in two counter-propagating QED-strong laser fields. A scaling of QED cascade growth with laser intensity is found, showing clear cascade saturation above threshold intensity of ~10 24 W/cm 2 . QED cascade saturation leads to pair plasma cooling and longitudinal compression along the laser axis, resulting in the subsequent formation of relativistic dense e - e + jets along transverse directions. Such laser-driven QED cascade saturation may open up the opportunity to study energetic astrophysical phenomena in laboratory.
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NASA Astrophysics Data System (ADS)
An, N. T. M.; Lien, N. T. H.; Hoang, N. D.; Hoa, D. Q.
2018-04-01
Energy transfer between spherical gold nanoparticles with size of more than 15 nm and molecules of organic dye 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4 H-pyran (DCM) has been studied. Such radiative energy transfer led to high local temperature, giving rise to a bleaching effect that resulted in rapid degradation of the laser medium. Gold nanoparticles were dispersed at concentrations from 5 × 109 particles/mL to 5 × 1010 particles/mL in DCM polymethylmethacrylate polymer using a radical polymerization process with 2,2'-azobis(isobutyronitrile) (AIBN) as initiator. Using the fast thermoelectric cooling method, the laser medium stability was significantly improved. The output stability of a distributed feedback dye laser pumped by second-harmonic generation from a neodymium-doped yttrium aluminum garnet (Nd:YAG) laser was investigated. Moreover, bidirectional energy transfer between gold nanoparticles and dye molecules was observed.
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Threshold ionization spectroscopic investigation of supersonic jet-cooled, laser-desorbed Tryptophan
NASA Astrophysics Data System (ADS)
Taherkhani, Mehran; Armentano, Antonio; Černý, Jiří; Müller-Dethlefs, Klaus
2016-07-01
Tryptophan (Trp) was studied by two-colour Photoionization Efficiency (PIE) and Mass Analysed Threshold Ionization (MATI) spectroscopy using a laser desorption apparatus. Conformer A of Trp was excited into the S1 state (34,878 cm-1) and the second laser was scanned around the D0 cation ground and the D1 excited state. No ionization signal into the D0 state could be found, but a clear threshold was observed for the D1 state with an ionization energy of 66,704 ± 3 cm-1 (8.27 eV). This observation is explained in terms of the electronic configurations of the S1 and cationic states.
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Structural, mechanical and optical studies on ultrafast laser inscribed chalcogenide glass waveguide
NASA Astrophysics Data System (ADS)
Ayiriveetil, Arunbabu; Varma, G. Sreevidya; Chaturvedi, Abhishek; Sabapathy, Tamilarasan; Ramamurty, Upadrasta; Asokan, Sundarrajan
2017-04-01
Multi-scan waveguides have been inscribed in GeS2 glass sample with different pulse energies and translation speeds. Mechanical and structural changes on GeS2 binary glass in response to irradiation to 1047 nm femto-second laser pulses have been investigated. The optical characterization of these waveguides has been done at 1550 nm of laser wavelength and the material response to laser exposure is characterized by both nanoindentation studies and micro-Raman spectroscopy. Nanoindentation investigations show a decrease in hardness (H) and elastic modulus (E) upon laser irradiation. The change in E and H are found to be varying with the translational speed, pulse energy and hence the net-fluence at the sample. These changes are correlated with variations in the Raman response of photo-exposed glass which is interpreted in terms of structural modifications made by the laser inscriptions to the glassy network. The mechanical behavior and local structural changes on waveguide writing is found to be dependent on net-fluence and it is correlated with the preparation conditions like melt temperature and cooling rate.
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White, James D; Scholten, Robert E
2012-11-01
We describe a compact laser wavelength measuring instrument based on a small diffraction grating and a consumer-grade webcam. With just 1 pW of optical power, the instrument achieves absolute accuracy of 0.7 pm, sufficient to resolve individual hyperfine transitions of the rubidium absorption spectrum. Unlike interferometric wavemeters, the instrument clearly reveals multimode laser operation, making it particularly suitable for use with external cavity diode lasers and atom cooling and trapping experiments.
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Tunable UV Laser Photolysis of NF2: Quantum Yield for NF(a1 delta) Production.
1988-05-25
UV Laser Photolysis of NF2: Quantum Yield for NF(a A) Production ’v0 LR. F. HEIDNER, H . HELVAJIAN , 4and J. B. KOFFEND Aerophysics Laboratory...experiments, the chemistry of NF2 with various hydrocarbons has been studied. It has also been shown that the addition-elimination reaction between H and NF2...COMPLI R LEN SP, 3 ,HAND L BE AM~ H O [ I , , i 1 CAIHOC IAM COOLED GaAs CAPACITANCE PHOTOTUIBE MANOMETER _ LENS /’~ ~L + . ANMEE _.... BANDPASS FILTER
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Nonequilibrium synthesis of NbAl3 and Nb-Al-V alloys by laser cladding. I - Microstructure evolution
NASA Technical Reports Server (NTRS)
Sircar, S.; Chattopadhyay, K.; Mazumder, J.
1992-01-01
The evolution of the microstructure in NbAl3 synthesized by a laser cladding technique (a rapid solidification process, with cooling rates up to 10 exp 6 C/sec) is investigated, and the phases are identified using convergent beam electron diffraction. Two new metastable phases were identified and characterized in detail. The effect of adding V on the final microstructure was also investigated, and the various phase chemistries and the partitioning of different elements into different phases were studied.
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High data-rate atom interferometers through high recapture efficiency
Biedermann, Grant; Rakholia, Akash Vrijal; McGuinness, Hayden
2015-01-27
An inertial sensing system includes a magneto-optical trap (MOT) that traps atoms within a specified trapping region. The system also includes a cooling laser that cools the trapped atoms so that the atoms remain within the specified region for a specified amount of time. The system further includes a light-pulse atom interferometer (LPAI) that performs an interferometric interrogation of the atoms to determine phase changes in the atoms. The system includes a controller that controls the timing of MOT and cooling laser operations, and controls the timing of interferometric operations to substantially recapture the atoms in the specified trapping region. The system includes a processor that determines the amount inertial movement of the inertial sensing system based on the determined phase changes in the atoms. Also, a method of inertial sensing using this inertial sensing system includes recapture of atoms within the MOT following interferometric interrogation by the LPAI.
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NASA Astrophysics Data System (ADS)
Park, Jun-Yong; Ryu, Jae Wook; Sohn, Il
2014-08-01
The in situ crystallization behavior of highly volatile commercial mold fluxes for medium carbon steels was investigated using the confocal laser scanning microscope (CLSM) equipped with an optimized isolated observation system. The highly volatile compounds of the mold flux were suppressed during heating allowing direct observation in the CLSM. Cooling rates of 25, 50, 100, 400, and 800 K/min were incorporated and continuous cooling transformation (CCT) diagrams of 4 different commercial mold fluxes for medium carbon steels were developed. Identification of the crystalline phase was conducted with XRD and SEM-EDS analysis. A cuspidine crystalline was observed in all samples at various cooling rates. With higher basicity, CaF2, and NaF, the crystallization of the fluxes was enhanced according to the CCT diagram. As the slag structure becomes depolymerized, the diffusion rate of the cathodic ions seems to increase.
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High-stability compact atomic clock based on isotropic laser cooling
DOE Office of Scientific and Technical Information (OSTI.GOV)
Esnault, Francois-Xavier; Holleville, David; Rossetto, Nicolas
2010-09-15
We present a compact cold-atom clock configuration where isotropic laser cooling, microwave interrogation, and clock signal detection are successively performed inside a spherical microwave cavity. For ground operation, a typical Ramsey fringe width of 20 Hz has been demonstrated, limited by the atom cloud's free fall in the cavity. The isotropic cooling light's disordered properties provide a large and stable number of cold atoms, leading to a high signal-to-noise ratio limited by atomic shot noise. A relative frequency stability of 2.2x10{sup -13{tau}-1/2} has been achieved, averaged down to 4x10{sup -15} after 5x10{sup 3} s of integration. Development of such amore » high-performance compact clock is of major relevance for on-board applications, such as satellite-positioning systems. As a cesium clock, it opens the door to a new generation of compact primary standards and timekeeping devices.« less
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Random aspects of beam physics and laser-plasma interactions
NASA Astrophysics Data System (ADS)
Charman, Andrew Emile
Aspects of the dynamics of charged particle and radiation beams, and of the interaction of plasmas with radiation are investigated, informed by concerns of classical and quantum mechanical uncertainty and noise, and related by notions of particle and radiation phase space manipulation, overlap, and control. We begin by studying questions of optimal longitudinal pulse-shaping in laser wakefield accelerators, based on a one-dimensional model with prescribed laser drive and either a linearized or fully nonlinear quasi-static plasma response. After discussing various figures of-merit, we advocate maximizing the peak wake amplitude instead of the transformer ratio. A number of new results are demonstrated, certain conjectures are rigorously proved for the first time, and some erroneous claims corrected. Instead of using short laser pulses to excite plasma waves, one can employ the beat wave between two co-propagating lasers to excite a Langmuir wave with high phase velocity suitable for acceleration of relativistic electrons. A modified version of this plasma beat-wave accelerator scheme is introduced and analyzed, which is based on autoresonant phase-locking of the nonlinear Langmuir wave to the slowly chirped beat frequency of the driving lasers via adiabatic passage through resonance. This new scheme is designed to overcome some of the well-known limitations of previous approaches, such as relativistic detuning and nonlinear modulation of the driven Langmuir wave amplitude, as well as sen sitivity to frequency mismatch due to measurement uncertainties and density fluctuations or inhomogeneities. From radiation exciting plasmas, we turn to issues of plasmas or beams emitting radiation. We develop a Hilbert-space and operator-based approach to electromagnetic radiation, and use this formalism to derive a maximum-power variational principle (MPVP) for spontaneous radiation from prescribed classical harmonic sources. Results are first derived in the paraxial limit, based on well-known analogies between paraxial optics and the Schrodinger equation for a single non-relativistic particle, and then generalized to non-paraxial situations. In essence, the variational principle says that prescribed classical charges radiate "as much as possible," consistent with energy conservation. The techniques are developed to model undulator radiation from relativistic electron beams, for which an example involving high harmonic generation is reviewed. We next study a situation where wiggler radiation is both emitted from particles and reapplied to them. In stochastic cooling, information in the radiation induced from a particle bunch, if suitably amplified and fed back on the beam, can decrease entropy and increase phase space density. Specifically, we analyze and assess possible quantum mechanical effects in optical stochastic cooling. Fast stochastic cooling (i.e., on microsecond time-scales) would be desirable in certain applications, for example, to boost final luminosity in the proposed muon collider, where the short particle lifetimes severely limit the total time available to reduce beam phase space. But fast cooling requires very high-bandwidth amplifiers to limit the incoherent heating effects from neighboring particles. Transit-time optical stochastic cooling employs high-gain, high-bandwidth, solid-state lasers to amplify the spontaneous radiation from the charged particle bunch in a strong-field magnetic wiggler. This amplified light is then fed back onto the same bunch inside a second wiggler, with appropriate phase delay to effect cooling. Prior to amplification, the usable coherent signal from any one particle is quite small, on average much less than one photon for each pass through the wiggler. This fact suggests that the radiation must be treated quantum mechanically, and raises doubts as to whether this weak signal even contains sufficient phase information for cooling and whether it can be reliably amplified to provide cooling on each pass. Further examining the possibility of quantum mechanical effects of charges and their radiation, we turn to quantum treatments of Electromagnetically-Induced-Transparency (EIT) in magnetized plasmas, in which the medium---normally opaque to a resonantly-polarized EM probe field at the cyclotron frequency---can be made transparent by the application of an intense EM pump at a frequency detuned below the cyclotron frequency by the plasma frequency. This raises fundamental questions as to how and to what extent a seemingly classical phenomena in plasma can mimic a quantum mechanical effect in atoms. We address these questions by describing both systems in a common quantum mechanical language, where in the cold, unsaturated limit, the relevant excitations are associated with collective Bosonic modes, or quasi-particles. EIT can be understood in terms of the dressing of these modes via the pump-mediated interaction, leading to a dark-state polariton coherently combining both field and particle excitations that is largely immune to the cyclotron resonance. (Abstract shortened by UMI.)
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Jet-cooled laser-induced fluorescence spectroscopy of ScH: Observation of an Ω‧=2-Ω″=1 transition
NASA Astrophysics Data System (ADS)
Mukund, Sheo; Bhattacharyya, Soumen; Nakhate, S. G.
2014-11-01
New bands of scandium monohydride at origins 17,914.5 and 17,942.3 cm-1 have been observed in a jet-cooled beam with laser-induced fluorescence spectroscopy. Mass-selected resonant photoionization spectroscopy also confirmed the carrier of the band as ScH. The rotational analysis indicated that both transitions at 17,914.5 and 17,942.3 cm-1 are of Ω‧=2-Ω″=1 type with vibrational assignments (0,0) and (1,1) respectively. The assigned g3Φ2-a3Δ1 excitation is the first observed triplet-triplet transition in ScH.
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Bright focused ion beam sources based on laser-cooled atoms
McClelland, J. J.; Steele, A. V.; Knuffman, B.; Twedt, K. A.; Schwarzkopf, A.; Wilson, T. M.
2016-01-01
Nanoscale focused ion beams (FIBs) represent one of the most useful tools in nanotechnology, enabling nanofabrication via milling and gas-assisted deposition, microscopy and microanalysis, and selective, spatially resolved doping of materials. Recently, a new type of FIB source has emerged, which uses ionization of laser cooled neutral atoms to produce the ion beam. The extremely cold temperatures attainable with laser cooling (in the range of 100 μK or below) result in a beam of ions with a very small transverse velocity distribution. This corresponds to a source with extremely high brightness that rivals or may even exceed the brightness of the industry standard Ga+ liquid metal ion source. In this review we discuss the context of ion beam technology in which these new ion sources can play a role, their principles of operation, and some examples of recent demonstrations. The field is relatively new, so only a few applications have been demonstrated, most notably low energy ion microscopy with Li ions. Nevertheless, a number of promising new approaches have been proposed and/or demonstrated, suggesting that a rapid evolution of this type of source is likely in the near future. PMID:27239245
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Bright focused ion beam sources based on laser-cooled atoms
DOE Office of Scientific and Technical Information (OSTI.GOV)
McClelland, J. J.; Wilson, T. M.; Steele, A. V.
2016-03-15
Nanoscale focused ion beams (FIBs) represent one of the most useful tools in nanotechnology, enabling nanofabrication via milling and gas-assisted deposition, microscopy and microanalysis, and selective, spatially resolved doping of materials. Recently, a new type of FIB source has emerged, which uses ionization of laser cooled neutral atoms to produce the ion beam. The extremely cold temperatures attainable with laser cooling (in the range of 100 μK or below) result in a beam of ions with a very small transverse velocity distribution. This corresponds to a source with extremely high brightness that rivals or may even exceed the brightness of themore » industry standard Ga{sup +} liquid metal ion source. In this review, we discuss the context of ion beam technology in which these new ion sources can play a role, their principles of operation, and some examples of recent demonstrations. The field is relatively new, so only a few applications have been demonstrated, most notably low energy ion microscopy with Li ions. Nevertheless, a number of promising new approaches have been proposed and/or demonstrated, suggesting that a rapid evolution of this type of source is likely in the near future.« less
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Microstructure and corrosion behavior of laser processed NiTi alloy.
Marattukalam, Jithin J; Singh, Amit Kumar; Datta, Susmit; Das, Mitun; Balla, Vamsi Krishna; Bontha, Srikanth; Kalpathy, Sreeram K
2015-12-01
Laser Engineered Net Shaping (LENS™), a commercially available additive manufacturing technology, has been used to fabricate dense equiatomic NiTi alloy components. The primary aim of this work is to study the effect of laser power and scan speed on microstructure, phase constituents, hardness and corrosion behavior of laser processed NiTi alloy. The results showed retention of large amount of high-temperature austenite phase at room temperature due to high cooling rates associated with laser processing. The high amount of austenite in these samples increased the hardness. The grain size and corrosion resistance were found to increase with laser power. The surface energy of NiTi alloy, calculated using contact angles, decreased from 61 mN/m to 56 mN/m with increase in laser energy density from 20 J/mm(2) to 80 J/mm(2). The decrease in surface energy shifted the corrosion potentials to nobler direction and decreased the corrosion current. Under present experimental conditions the laser power found to have strong influence on microstructure, phase constituents and corrosion resistance of NiTi alloy. Copyright © 2015 Elsevier B.V. All rights reserved.
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Modeling of plasma and thermo-fluid transport in hybrid welding
NASA Astrophysics Data System (ADS)
Ribic, Brandon D.
Hybrid welding combines a laser beam and electrical arc in order to join metals within a single pass at welding speeds on the order of 1 m min -1. Neither autonomous laser nor arc welding can achieve the weld geometry obtained from hybrid welding for the same process parameters. Depending upon the process parameters, hybrid weld depth and width can each be on the order of 5 mm. The ability to produce a wide weld bead increases gap tolerance for square joints which can reduce machining costs and joint fitting difficulty. The weld geometry and fast welding speed of hybrid welding make it a good choice for application in ship, pipeline, and aerospace welding. Heat transfer and fluid flow influence weld metal mixing, cooling rates, and weld bead geometry. Cooling rate affects weld microstructure and subsequent weld mechanical properties. Fluid flow and heat transfer in the liquid weld pool are affected by laser and arc energy absorption. The laser and arc generate plasmas which can influence arc and laser energy absorption. Metal vapors introduced from the keyhole, a vapor filled cavity formed near the laser focal point, influence arc plasma light emission and energy absorption. However, hybrid welding plasma properties near the opening of the keyhole are not known nor is the influence of arc power and heat source separation understood. A sound understanding of these processes is important to consistently achieving sound weldments. By varying process parameters during welding, it is possible to better understand their influence on temperature profiles, weld metal mixing, cooling rates, and plasma properties. The current literature has shown that important process parameters for hybrid welding include: arc power, laser power, and heat source separation distance. However, their influence on weld temperatures, fluid flow, cooling rates, and plasma properties are not well understood. Modeling has shown to be a successful means of better understanding the influence of processes parameters on heat transfer, fluid flow, and plasma characteristics for arc and laser welding. However, numerical modeling of laser/GTA hybrid welding is just beginning. Arc and laser welding plasmas have been previously analyzed successfully using optical emission spectroscopy in order to better understand arc and laser plasma properties as a function of plasma radius. Variation of hybrid welding plasma properties with radial distance is not known. Since plasma properties can affect arc and laser energy absorption and weld integrity, a better understanding of the change in hybrid welding plasma properties as a function of plasma radius is important and necessary. Material composition influences welding plasma properties, arc and laser energy absorption, heat transfer, and fluid flow. The presence of surface active elements such as oxygen and sulfur can affect weld pool fluid flow and bead geometry depending upon the significance of heat transfer by convection. Easily vaporized and ionized alloying elements can influence arc plasma characteristics and arc energy absorption. The effects of surface active elements on heat transfer and fluid flow are well understood in the case of arc and conduction mode laser welding. However, the influence of surface active elements on heat transfer and fluid flow during keyhole mode laser welding and laser/arc hybrid welding are not well known. Modeling has been used to successfully analyze the influence of surface active elements during arc and conduction mode laser welding in the past and offers promise in the case of laser/arc hybrid welding. A critical review of the literature revealed several important areas for further research and unanswered questions. (1) The understanding of heat transfer and fluid flow during hybrid welding is still beginning and further research is necessary. (2) Why hybrid welding weld bead width is greater than that of laser or arc welding is not well understood. (3) The influence of arc power and heat source separation distance on cooling rates during hybrid welding are not known. (4) Convection during hybrid welding is not well understood despite its importance to weld integrity. (5) The influence of surface active elements on weld geometry, weld pool temperatures, and fluid flow during high power density laser and laser/arc hybrid welding are not known. (6) Although the arc power and heat source separation distance have been experimentally shown to influence arc stability and plasma light emission during hybrid welding, the influence of these parameters on plasma properties is unknown. (7) The electrical conductivity of hybrid welding plasmas is not known, despite its importance to arc stability and weld integrity. In this study, heat transfer and fluid flow are analyzed for laser, gas tungsten arc (GTA), and laser/GTA hybrid welding using an experimentally validated three dimensional phenomenological model. By evaluating arc and laser welding using similar process parameters, a better understanding of the hybrid welding process is expected. The role of arc power and heat source separation distance on weld depth, weld pool centerline cooling rates, and fluid flow profiles during CO2 laser/GTA hybrid welding of 321 stainless steel are analyzed. Laser power is varied for a constant heat source separation distance to evaluate its influence on weld temperatures, weld geometry, and fluid flow during Nd:YAG laser/GTA hybrid welding of A131 structural steel. The influence of oxygen and sulfur on keyhole and weld bead geometry, weld temperatures, and fluid flow are analyzed for high power density Yb doped fiber laser welding of (0.16 %C, 1.46 %Mn) mild steel. Optical emission spectroscopy was performed on GTA, Nd:YAG laser, and Nd:YAG laser/GTA hybrid welding plasmas for welding of 304L stainless steel. Emission spectroscopy provides a means of determining plasma temperatures and species densities using deconvoluted measured spectral intensities, which can then be used to calculate plasma electrical conductivity. In this study, hybrid welding plasma temperatures, species densities, and electrical conductivities were determined using various heat source separation distances and arc currents using an analytical method coupled calculated plasma compositions. As a result of these studies heat transfer by convection was determined to be dominant during hybrid welding of steels. The primary driving forces affecting hybrid welding fluid flow are the surface tension gradient and electromagnetic force. Fiber laser weld depth showed a negligible change when increasing the (0.16 %C, 1.46 %Mn) mild steel sulfur concentration from 0.006 wt% to 0.15 wt%. Increasing the dissolved oxygen content in weld pool from 0.0038 wt% to 0.0257 wt% increased the experimental weld depth from 9.3 mm to 10.8 mm. Calculated partial pressure of carbon monoxide increased from 0.1 atm to 0.75 atm with the 0.0219 wt% increase in dissolved oxygen in the weld metal and may explain the increase in weld depth. Nd:YAG laser/GTA hybrid welding plasma temperatures were calculated to be approximately between 7927 K and 9357 K. Increasing the Nd:YAG laser/GTA hybrid welding heat source separation distance from 4 mm to 6 mm reduced plasma temperatures between 500 K and 900 K. Hybrid welding plasma total electron densities and electrical conductivities were on the order of 1 x 1022 m-3 and 3000 S m-1, respectively.
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Laser micro-processing of amorphous and partially crystalline Cu45Zr48Al7 alloy
NASA Astrophysics Data System (ADS)
Aqida, S. N.; Brabazon, D.; Naher, S.; Kovacs, Z.; Browne, D. J.
2010-11-01
This paper presents a microstructural study of laser micro-processed high-purity Cu45Zr48Al7 alloys prepared by arc melting and Cu-mould casting. Microprocessing of the Cu45Zr48Al7 alloy was performed using a Rofin DC-015 diffusion-cooled CO2 slab laser system with 10.6-μm wavelength. The laser was defocused to a spot size of 0.2 mm on the sample surface. The laser parameters were set to give 300- and 350-W peak power, 30% duty cycle and a 3000-Hz laser pulse repetition frequency (PRF). About 100-micrometer-wide channels were scribed on the surfaces of disk-shaped amorphous and partially crystalline samples at traverse speeds of 500 and 5000 mm/min. These channels were analysed using scanning electron microscopy (SEM) and 2D stylus profilometry. The metallographic study and profile of these processed regions are discussed in terms of the applied laser processing parameters. The SEM micrographs showed that striation marks developed at the edge and inside these regions as a result of the laser processing. The results from this work showed that microscale features can be produced on the surface of amorphous Cu-Zr-Al alloys by CO2 laser processing.
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Fusion welding studies using laser on Ti-SS dissimilar combination
NASA Astrophysics Data System (ADS)
Shanmugarajan, B.; Padmanabham, G.
2012-11-01
Laser welding investigations were carried out on dissimilar Ti-SS combination. The study is aimed to improve the weld strength and ductility by minimizing harmful intermetallics and taking advantage of high cooling rates in laser welding. Results of continuous wave 3.5 kW CO2 laser welding of totally dissimilar combination of Titanium and stainless steel (304) have been discussed. Bead on plate welding experiments were conducted to identify the laser welding parameters using depth of penetration as criteria. The welding of dissimilar combination has been attempted both autogenously and with interlayers such as Vanadium (V) and Tantalum (Ta) in the form of laser cladding as well as strip. Autogenous welds were carried out by varying the laser power, welding speed and position of the laser beam with respect to the joint centre. The resultant welds are characterized by macrostructure analysis, SEM/EDAX and XRD and as welded tensile test in UTM. The autogenous welds have exhibited extensive cracking even when welded at high speeds or by manipulating the beam position with respect to the joint. Similarly Vandaium as interlayer could not achieve crack free joint. A joint with 40 MPa strength could be made with Ta as interlayer. Results and analysis of these variants of laser welded joints are reported and discussed.
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Non-ablative 1,450-nm diode laser treatment of striae distensae.
Tay, Yong-Kwang; Kwok, Colin; Tan, Eileen
2006-03-01
Striae distensae are dermal scars with flattening and atrophy of the epidermis. Successful treatment of these stretch marks has been disappointing. The non-ablative 1,450-nm diode laser has been shown to improve atrophic scars and may be expected to improve striae. As yet, no study has been published to document the effects of this laser on striae. Our aim is to evaluate the efficacy of the 1,450-nm diode laser in the treatment of striae rubra and striae alba in Asian patients with skin types 4-6. Striae on one half of the body in 11 patients were treated with the 1,450-nm diode laser with cryogen cooling spray with the other half serving as a control. The following parameters were used: 6 mm spot size and dynamic cooling device (DCD) for 40 milliseconds to protect the epidermis. Patients were randomly assigned to receive either 4, 8, or 12 J/cm2. A total of three treatments were given at 6-week intervals. The following sites were treated: abdomen, arms, back, buttocks, and thighs. Two patients had striae rubra and nine striae alba. Clinical photographs were taken before and after each treatment and analysis was undertaken through photographic evaluation by non-treating physicians. At 2 months after the last treatment, no patients showed any noticeable improvement in the striae on the treated side compared to baseline and to the control areas. Side effects were limited to transient erythema and postinflammatory hyperpigmentation (PIH), which occurred in seven (64%) patients. The non-ablative 1,450-nm diode laser is not useful in the treatment of striae in patients with skin types 4, 5, and 6. 2006 Wiley-Liss, Inc.
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NASA Astrophysics Data System (ADS)
Frevert, C.; Bugge, F.; Knigge, S.; Ginolas, A.; Erbert, G.; Crump, P.
2016-03-01
Both high-energy-class laser facilities and commercial high-energy pulsed laser sources require reliable optical pumps with the highest pulse power and electro-optical efficiency. Although commercial quasi-continuous wave (QCW) diode laser bars reach output powers of 300…500 W further improvements are urgently sought to lower the cost per Watt, improve system performance and reduce overall system complexity. Diode laser bars operating at temperatures of around 200 K show significant advances in performance, and are particularly attractive in systems that use cryogenically cooled solid state lasers. We present the latest results on 940 nm, passively cooled, 4 mm long QCW diode bars which operate under pulse conditions of 1.2 ms, 10 Hz at an output power of 1 kW with efficiency of 70% at 203 K: a two-fold increase in power compared to 300 K, without compromising efficiency. We discuss how custom low-temperature design of the vertical layers can mitigate the limiting factors such as series resistance while sustaining high power levels. We then focus on the remaining obstacles to higher efficiency and power, and use a detailed study of multiple vertical structures to demonstrate that the properties of the active region are a major performance limit. Specifically, one key limit to series resistance is transport in the layers around the active region and the differential internal efficiency is closely correlated to the threshold current. Tailoring the barriers around the active region and reducing transparency current density thus promise bars with increased performance at temperatures of 200 K as well as 300 K.
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Process of making cryogenically cooled high thermal performance crystal optics
Kuzay, Tuncer M.
1992-01-01
A method for constructing a cooled optic wherein one or more cavities are milled, drilled or formed using casting or ultrasound laser machining techniques in a single crystal base and filled with porous material having high thermal conductivity at cryogenic temperatures. A non-machined strain-free single crystal can be bonded to the base to produce superior optics. During operation of the cooled optic, N.sub.2 is pumped through the porous material at a sub-cooled cryogenic inlet temperature and with sufficient system pressure to prevent the fluid bulk temperature from reaching saturation.
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Process of making cryogenically cooled high thermal performance crystal optics
Kuzay, T.M.
1992-06-23
A method is disclosed for constructing a cooled optic wherein one or more cavities are milled, drilled or formed using casting or ultrasound laser machining techniques in a single crystal base and filled with porous material having high thermal conductivity at cryogenic temperatures. A non-machined strain-free single crystal can be bonded to the base to produce superior optics. During operation of the cooled optic, N[sub 2] is pumped through the porous material at a sub-cooled cryogenic inlet temperature and with sufficient system pressure to prevent the fluid bulk temperature from reaching saturation. 7 figs.
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Laser-Induced Breakdown Spectroscopy Infrared Emission From Inorganic and Organic Substances
2006-11-01
using a liquid-nitrogen cooled indium antimonide (InSb) detector and the signal was recorded using a gated electronic circuit (boxcar averager). All...contaminants by analyzing the atomic spectral emission lines that result subsequent to plasmas generated by laser power. The ultraviolet-visible-near infrared...UV- Vis-NIR) spectral region exploited in conventional LIBS largely elucidates the elemental composition of the laser target by profiling these
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The Microstructural and Property Changes of Laser Treated Electrodeposits
1981-01-01
corresponds to the center of the LASER beam path. Examination of the underlying steel reveals a transformation which appears to be untempered martensite ...specimen after LASER interaction time of 50 ms. Phase transformations have advanced through the complete thickness of the specimen. ii. Hardness plot through...cooling. 13 This technique of achieving homogeneous phase transformations in the surface with sufficient control of surface depth has formed the basis
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12 mJ Yb:YAG/Cr:YAG microchip laser.
Guo, Xiaoyang; Tokita, Shigeki; Kawanaka, Junji
2018-02-01
We have developed a quasi-continuous wave diode end-pumped cryogenically cooled Yb:YAG/Cr:YAG passively Q-switched microchip laser. A maximum energy of 12.1 mJ with 3.7 MW of peak power was obtained. To the best of our knowledge, this is the highest energy and peak power obtained by an Yb:YAG/Cr:YAG microchip laser so far.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Gong, W.; Peng, X., E-mail: xiangpeng@pku.edu.cn; Li, W.
2014-07-15
Two kinds of optical heterodyne saturation spectroscopies, namely, frequency modulation spectroscopy (FMS) and modulation transfer spectroscopy (MTS), are demonstrated for locking a fiber laser to the transition lines of metastable {sup 4}He atoms around 1083 nm. The servo-loop error signals of FMS and MTS for stabilizing laser frequency are optimized by studying the dependence of the peak-to-peak amplitude and slope on the optical power of pump and probe beams. A comparison of the stabilization performances of FMS/MTS and polarization spectroscopy (PS) is presented, which shows that MTS exhibits relatively superior performance with the least laser frequency fluctuation due to itsmore » flat-background dispersive signal, originated from the four-wave mixing process. The Allan deviation of the stabilized laser frequency is 5.4 × 10{sup −12}@100 s with MTS for data acquired in 1000 s, which is sufficiently applicable for fields like laser cooling, optical pumping, and optical magnetometry.« less
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NASA Astrophysics Data System (ADS)
Xiang, Zhaowei; Yin, Ming; Dong, Guanhua; Mei, Xiaoqin; Yin, Guofu
2018-06-01
A finite element model considering volume shrinkage with powder-to-dense process of powder layer in selective laser melting (SLM) is established. Comparison between models that consider and do not consider volume shrinkage or powder-to-dense process is carried out. Further, parametric analysis of laser power and scan speed is conducted and the reliability of linear energy density as a design parameter is investigated. The results show that the established model is an effective method and has better accuracy allowing for the temperature distribution, and the length and depth of molten pool. The maximum temperature is more sensitive to laser power than scan speed. The maximum heating rate and cooling rate increase with increasing scan speed at constant laser power and increase with increasing laser power at constant scan speed as well. The simulation results and experimental result reveal that linear energy density is not always reliable using as a design parameter in the SLM.
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An overview of clinical and experimental treatment modalities for port wine stains.
Chen, Jennifer K; Ghasri, Pedram; Aguilar, Guillermo; van Drooge, Anne Margreet; Wolkerstorfer, Albert; Kelly, Kristen M; Heger, Michal
2012-08-01
Port wine stains (PWS) are the most common vascular malformation of the skin, occurring in 0.3% to 0.5% of the population. Noninvasive laser irradiation with flashlamp-pumped pulsed dye lasers (selective photothermolysis) currently comprises the gold standard treatment of PWS; however, the majority of PWS fail to clear completely after selective photothermolysis. In this review, the clinically used PWS treatment modalities (pulsed dye lasers, alexandrite lasers, neodymium:yttrium-aluminum-garnet lasers, and intense pulsed light) and techniques (combination approaches, multiple passes, and epidermal cooling) are discussed. Retrospective analysis of clinical studies published between 1990 and 2011 was performed to determine therapeutic efficacies for each clinically used modality/technique. In addition, factors that have resulted in the high degree of therapeutic recalcitrance are identified, and emerging experimental treatment strategies are addressed, including the use of photodynamic therapy, immunomodulators, angiogenesis inhibitors, hypobaric pressure, and site-specific pharmaco-laser therapy. Copyright © 2011 American Academy of Dermatology, Inc. Published by Mosby, Inc. All rights reserved.
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Stabilized 1762 nm Laser for Barium Ion Qubit Readout via Adiabatic Passage
NASA Astrophysics Data System (ADS)
Salacka, Joanna
2008-05-01
Trapped ions are one of the most promising candidates for the implementation of quantum computation. We are trapping single ions of Ba^137 to serve as our qubit, because the hyperfine structure of its ground state and its various visible-wavelength transitions make it favorable for quantum computation. The two hyperfine ground levels will serve as our |1> and |0> qubit states. The readout of the qubit will be accomplished by first selectively shelving the ion directly to the metastable 5D5/2 state using a 1762 nm narrow band fiber laser. Next, the cooling and repumping lasers are turned on and the fluorescence of the ion is measured. Since the 5D5/2 state is decoupled from the laser cooling transitions, the ion will remain dark when shelved. Thus if fluorescence is seen we know that the qubit was in the |0> state, and if no fluorescence is seen it was in the |1> state. The laser is actively stabilized to a temperature-controlled, high-finesse 1.76 um Zerodur optical cavity. The shelving to the 5D5/2 state is most efficiently achieved with adiabatic passage, which requires a smooth scan of the laser frequency across the transition resonance. To accomplish this, the laser frequency is modulated by an AOM driven by a smooth frequency sweep of adjustable amplitude and duration.
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Shear test of composite bonded to dentin: Er:YAG laser versus dental handpiece preparations
NASA Astrophysics Data System (ADS)
Visuri, Steven R.; Gilbert, Jeremy L.; Walsh, Joseph T., Jr.; Wigdor, Harvey A.
1995-05-01
The erbium:YAG laser coupled with a cooling stream of water appears to be an effective means of removing dental hard tissues. However, before the procedure is deemed clinically viable, there are several important issues of safety and efficacy that need to be explored. In this study we investigated the surface that remains following laser ablation of dentin and compared the results to the use of a dental handpiece. Specifically, we studied the effect the laser radiation had on the bonding of composite to dentin. The crowns of extracted human molars were removed revealing the underlying dentin. An additional thickness of material was removed with either a dental handpiece or an Er:YAG laser by raster scanning the samples under a fixed handpiece or laser. Comparable surface roughnesses were achieved. A cylinder of composite was bonded onto the prepared surfaces following the manufacturer's directions. The dentin-composite bond was then shear stressed to failure on a universal testing apparatus and the maximum load recorded. Preliminary results indicated that laser irradiated samples had improved bond strengths. SEM photographs of the surfaces were also taken to compare the two methods of tooth preparation.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Veselov, D. A.; Shashkin, I. S.; Bobretsova, Yu. K.
2016-10-15
Pulse-pumped MOVPE-fabricated (metal-organic vapor-phase epitaxy) semiconductor lasers emitting in the spectral ranges 1000–1100 and 1400–1600 nm at temperatures of 110–120 K are studied. It is found that cooling the lasers for both spectral ranges to low temperature results in their light–current curves approaching linearity, and an optical power of, respectively, 110 and 20 W can be attained. The low-temperature effect is reduced for lasers emitting in the spectral range 1400–1600 nm. The processes affecting a rise in the internal optical loss in semiconductor lasers are considered. It is shown that an increase in the carrier concentration in the waveguide ofmore » a laser structure greatly depends on temperature and is determined by the noninstantaneous capture (capture rate) of carriers from the waveguide into the active region. It is demonstrated that, upon lowering the temperature to 115K, the concentration of electrons and holes in the waveguide becomes lower, which leads to a significant decrease in the internal optical loss and to an increase in the output optical power of the semiconductor laser.« less
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Laser Surface Modification of H13 Die Steel using Different Laser Spot Sizes
NASA Astrophysics Data System (ADS)
Aqida, S. N.; Naher, S.; Brabazon, D.
2011-05-01
This paper presents a laser surface modification process of AISI H13 tool steel using three sizes of laser spot with an aim to achieve reduced grain size and surface roughness. A Rofin DC-015 diffusion-cooled CO2 slab laser was used to process AISI H13 tool steel samples. Samples of 10 mm diameter were sectioned to 100 mm length in order to process a predefined circumferential area. The parameters selected for examination were laser peak power, overlap percentage and pulse repetition frequency (PRF). Metallographic study and image analysis were done to measure the grain size and the modified surface roughness was measured using two-dimensional surface profilometer. From metallographic study, the smallest grain sizes measured by laser modified surface were between 0.51 μm and 2.54 μm. The minimum surface roughness, Ra, recorded was 3.0 μm. This surface roughness of the modified die steel is similar to the surface quality of cast products. The grain size correlation with hardness followed the findings correlate with Hall-Petch relationship. The potential found for increase in surface hardness represents an important method to sustain tooling life.
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NASA Astrophysics Data System (ADS)
Alekseev, V. A.; Krylova, D. D.
1996-02-01
The analytical investigation of Bloch equations is used to describe the main features of the 1D velocity selective coherent population trapping cooling scheme. For the initial stage of cooling the fraction of cooled atoms is derived in the case of a Gaussian initial velocity distribution. At very long times of interaction the fraction of cooled atoms and the velocity distribution function are described by simple analytical formulae and do not depend on the initial distribution. These results are in good agreement with those of Bardou, Bouchaud, Emile, Aspect and Cohen-Tannoudji based on statistical analysis in terms of Levy flights and with Monte-Carlo simulations of the process.
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NASA Astrophysics Data System (ADS)
Horne, A.; Hodges, K. V.; Van Soest, M. C.
2015-12-01
The newly developed 'laser ablation double dating' (LADD) technique, an integrated laser microprobe U/Pb and (U-Th)/He dating method, could be an exceptionally valuable tool in detrital thermochronology for identifying sedimentary provenance and evaluating the exhumation history of a source region. A recent proof-of-concept study has used LADD to successfully date both zircon and titanite crystals from the well-characterized Fish Canyon tuff, but we also believe that another accessory mineral, rutile, could be amenable to dating via the LADD technique. To continue the development of the method, we present an application of LADD to detrital zircon, titanite, and rutile from a sample collected on the lower Naryani River of central Nepal. Preliminary analyses of the sample have yielded zircon U/Pb dates ranging from 31.4 to 2405 Ma; zircon (U-Th)/He from 1.8 to 15.4 Ma; titanite U/Pb between 18 and 110 Ma; titanite (U-Th)/He between 1 and 16 Ma; rutile U/Pb from 6 to 45 Ma; and rutile (U-Th)/He from 2 to 25 Ma. In addition to the initial data, we can use Ti-in-zircon, Zr-in-titanite, and Zr-in-rutile thermometers to determine the range of possible long-term cooling rates from grains with U/Pb ages younger than collision. Thus far our results from zircon analyses imply a cooling rate of approximately 15°C/Myr; titanite analyses imply between 10 and 67°C/Myr; and rutile between 9 and 267°C/Myr. This spread in potential cooling rates, especially in the order of magnitude differences of cooling rates calculated from the rutile grains, suggests that the hinterland source regions of the Naryani river experienced dramatically different exhumation histories during Himalayan orogenisis. Ongoing analyses will expand the dataset such that we can more adequately characterize the range of possibilities represented in the sample.
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Highly reliable high-power AlGaAs/GaAs 808 nm diode laser bars
NASA Astrophysics Data System (ADS)
Hülsewede, R.; Schulze, H.; Sebastian, J.; Schröder, D.; Meusel, J.; Hennig, P.
2007-02-01
There are strong demands at the market to increase power and reliability for 808 nm diode laser bars. Responding to this JENOPTIK Diode Lab GmbH developed high performance 808 nm diode laser bars in the AlGaAs/GaAs material system with special emphasis to high power operation and long term stability. Optimization of the epitaxy structure and improvements in the diode laser bar design results in very high slope efficiency of >1.2 W/A, low threshold current and small beam divergence in slow axis direction. Including low serial resistance the overall wall plug efficiency is up to 65% for our 20%, 30% and 50% filling factor 10 mm diode laser bars. With the JENOPTIK Diode Lab cleaving and coating technique the maximum output power is 205 W in CW operation and 377 W in QCW operation (200 μs, 2% duty cycle) for bars with 50% filling factor. These bars mounted on micro channel cooled package are showing a very high reliability of >15.000 h. Mounted on conductive cooled package high power operation at 100 W is demonstrated for more than 5000h.
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Pulse length of ultracold electron bunches extracted from a laser cooled gas
Franssen, J. G. H.; Frankort, T. L. I.; Vredenbregt, E. J. D.; Luiten, O. J.
2017-01-01
We present measurements of the pulse length of ultracold electron bunches generated by near-threshold two-photon photoionization of a laser-cooled gas. The pulse length has been measured using a resonant 3 GHz deflecting cavity in TM110 mode. We have measured the pulse length in three ionization regimes. The first is direct two-photon photoionization using only a 480 nm femtosecond laser pulse, which results in short (∼15 ps) but hot (∼104 K) electron bunches. The second regime is just-above-threshold femtosecond photoionization employing the combination of a continuous-wave 780 nm excitation laser and a tunable 480 nm femtosecond ionization laser which results in both ultracold (∼10 K) and ultrafast (∼25 ps) electron bunches. These pulses typically contain ∼103 electrons and have a root-mean-square normalized transverse beam emittance of 1.5 ± 0.1 nm rad. The measured pulse lengths are limited by the energy spread associated with the longitudinal size of the ionization volume, as expected. The third regime is just-below-threshold ionization which produces Rydberg states which slowly ionize on microsecond time scales. PMID:28396879
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NASA Astrophysics Data System (ADS)
Hutzler, Nicholas R.; Doyle, John M.
2014-06-01
Cryogenic buffer gas cooled beams and cells can be used to study many species, from atoms and polar molecules to biomolecules. We report on recent applications of this technique to improve the limit on the electron electric dipole moment [1], load polar molecules into a magnetic trap through optical pumping [2], perform chirally sensitive microwave spectroscopy on polyatomic molecules [3], progress towards magneto-optical trapping of polar molecules [4], and studies of atom-molecule sticking [5]. [1] The ACME Collaboration: J. Baron et al., Science 343, p. 269 (2014) [2] B. Hemmerling et al., arXiv:1310.2669, to appear in Phys. Rev. Lett. [3] D. Patterson, M. Schnell, & J. M. Doyle, Nature 497, p. 475 (2013) [4] H. Lu et al., arXiv:1310.3239, to appear in New. J. Phys. [5] J. Piskorski et al., under preparation
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NASA Astrophysics Data System (ADS)
Kuptsov, G. V.; Petrov, V. V.; Petrov, V. A.; Laptev, A. V.; Kirpichnikov, A. V.; Pestryakov, E. V.
2018-04-01
The source of instabilities in the multidisk diode-pumped high power Yb:YAG laser amplifier with cryogenic closed-loop cooling in the laser amplification channel of the high-intensity laser system with 1 kHz repetition rate was determined. Dissected copper mounts were designed and used to suppress instabilities and to achieve repeatability of the system. The equilibrium temperature dependency of the active elements on average power was measured. The seed laser for the multidisk amplifier was numerically simulated and designed to allow one to increase pulses output energy after the amplifier up to 500 mJ.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Walters, C.T.; Dulaney, J.L.; Campbell, B.E.
Demonstrations of operation of a compact neodymium glass laser with average output powers greater than 1 kW for several seconds are reported. The laser is based on the thermal inertia laser (TIL) concept wherein a neodymium-doped glass rod is pumped uniformly without cooling during a burst mode of laser operation. Design principles for TIL devices and scaling to 100 kW class lasers are discussed. Experimental results for a low repetition-rate proof-of-concept pulsed device (30 J, 0.2 Hz) and a high repetition-rate pulsed prototype (40 J, 36 Hz) are presented and compared to numerical solutions for the laser rate equations withmore » temperature dependent cross-sections.« less
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A cryo-cooled high-energy DPSSL system delivering ns-pulses at 10 J and 10 Hz
NASA Astrophysics Data System (ADS)
Ertel, Klaus; Banerjee, Saumyabrata; Butcher, Thomas J.; De Vido, Mariastefania; Mason, Paul D.; Phillips, P. J.; Richards, David; Shaikh, Waseem; Smith, Jodie M.; Greenhalgh, R. Justin S.; Hernandez-Gomez, Cristina; Collier, John L.
2015-02-01
Lasers generating multi-J to kJ ns-pulses are required for many types of laser-plasma interactions. Such lasers are either used directly for compressing matter to extreme densities or they serve as pump lasers for short-pulses laser chains based on large-aperture Ti:sapphire or parametric amplifiers. The thus generated high-energy fs-pulses are most useful for laser driven secondary sources of particles (electrons, protons) or photons (from THz to gamma). While proof-of-principle experiments have been carried out with flashlamp-pumped glass lasers, lasers with much higher efficiency and repetition rate are required to make this applications practically viable. We have developed a scalable new laser concept called DiPOLE (diode pumped optical laser for experiments) based on a gas-cooled ceramic Yb:YAG multi-slab architecture operating at cryogenic temperatures. While the viability of this concept has been shown earlier [1], we have now reached our target performance of 10 J pulse energy at 10 Hz repetition rate at an optical-to-optical efficiency of 21%. To the best of our knowledge, these are record values for average power and efficiency for lasers of this type. We have also upgraded the system by adding a fibre-based front-end system with arbitrary pulse shaping capability and by installing an image-relayed multipass system enabling up to eight passes of the main amplifier. We have then used this system to demonstrate frequency doubling with 65 % conversion efficiency and a long-term shot-to-shot stability of 0.5% rms over a total of nearly 2 million shots, achieved in runs extending over 4 to 6 hours.
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Quenches across the self-organization transition in multimode cavities
NASA Astrophysics Data System (ADS)
Keller, Tim; Torggler, Valentin; Jäger, Simon B.; Schütz, Stefan; Ritsch, Helmut; Morigi, Giovanna
2018-02-01
A cold dilute atomic gas in an optical resonator can be radiatively cooled by coherent scattering processes when the driving laser frequency is tuned close to but below the cavity resonance. When the atoms are sufficiently illuminated, their steady state undergoes a phase transition from a homogeneous distribution to a spatially organized Bragg grating. We characterize the dynamics of this self-ordering process in the semi-classical regime when distinct cavity modes with commensurate wavelengths are quasi-resonantly driven by laser fields via scattering by the atoms. The lasers are simultaneously applied and uniformly illuminate the atoms; their frequencies are chosen so that the atoms are cooled by the radiative processes, and their intensities are either suddenly switched or slowly ramped across the self-ordering transition. Numerical simulations for different ramp protocols predict that the system will exhibit long-lived metastable states, whose occurrence strongly depends on the initial temperature, ramp speed, and the number of atoms.
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NASA Astrophysics Data System (ADS)
Arsenault, D. L.; Tokaryk, D. W.; Adam, A. G.; Linton, C.
2016-06-01
We have taken laser-induced fluorescence spectra of jet-cooled nickel monofluoride formed in a laser-ablation molecular beam source. Dispersed-fluorescence spectroscopy confirms predictions by Hougen (2011) that the parity assignments of levels in the Ω = 1 / 2 state 1570 cm-1 above the ground state should be reversed from those given in Krouti et al. (2002). The quality of the high-resolution spectra was sufficient to measure the [22.9]1.5-X1.5 band for five isotopologues of nickel and the [22.9]1.5-[0.25]0.5 band for molecules containing 58Ni and 60Ni. The spectral line positions for each isotopologue were fit to the Hamiltonian model given by Hougen, which was extended to allow for calculation of the parity-splitting parameter in the ground state.
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Telle, J.M.
1984-05-01
Apparatus and method for generating continuous wave 16 ..mu..m laser radiation using gaseous CF/sub 4/. Laser radiation at 16 ..mu..m has been observed in a cooled static cell containing low pressure CF/sub 4/ optically pumped by an approximately 3 W output power c-w CO/sub 2/ laser. The laser cavity employed was a multiple-pass off-axis-path two spherical mirror ring resonator. Unidirectional CF/sub 4/ laser output power at 615 cm/sup -1/ exceeded 2 mW. Computer calculations indicate that for modest pump powers of about 40 W, approximately 1 W of emitted laser radiation at 16 ..mu..m might be obtained.
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Apparatus and method for generating continuous wave 16 .mu.m laser radiation using gaseous CF.sub.4
Telle, John M.
1986-01-01
Apparatus and method for generating continuous wave 16 .mu.m laser radiation using gaseous CF.sub.4. Laser radiation at 16 .mu.m has been observed in a cooled static cell containing low pressure CF.sub.4 optically pumped by an approximately 3 W output power cw CO.sub.2 laser. The laser cavity employed was a multiple-pass off-axis-path two spherical mirror ring resonator. Unidirectional CF.sub.4 laser output power at 615 cm.sup.-1 exceeded 2 mW. Computer calculations indicate that for modest pump powers of about 40 W, approximately 1 W of emitted laser radiation at 16 .mu.m might be obtained.
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NASA Astrophysics Data System (ADS)
Dulieu, O.; Hall, F. H. J.; Eberle, P.; Hegi, G.; Raoult, M.; Aymar, M.; Willitsch, S.
2013-05-01
Cold chemical reactions between laser-cooled Ca+ or Ba+ ions and Rb atoms were studied in an ion-atom hybrid trap. Reaction rate constants were determined in the collision energy range Ecoll /kB = 20 mK-20 K. Product branching ratios were studied using resonant-excitation mass spectrometry. The dynamics of the reactive processes including the radiative formation of CaRb+ and BaRb+ molecular ions has been analyzed using accurate potential energy curves and quantum-scattering calculations for the radiative channels. It is shown that the energy dependence of the reaction rates is governed by long-range interactions, while its magnitude is determined by short-range non-adiabatic and radiative couplings. The quantum character of the collisions is predicted to manifest itself in the occurrence of narrow shape resonances at well-defined collision energies. The present results highlight both universal and system-specific phenomena in cold ion-neutral collisions. This work was supported by the Swiss National Science Foundation and the COST Action ''Ion Traps for Tomorrow's Applications''.
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Effects of the Atmosphere on the Propagation of 10.6-micro Laser Beams.
Hayes, J N; Ulrich, P B; Aitken, A H
1972-02-01
This paper gives an overview of the use of a wave optics computer code to model the propagation of high power CO(2) laser beams in the atmosphere. The nonlinear effects of atmospheric heating and kinetic cooling phenomena are included in the analysis. Only steady-state, nonturbulent cases are studied. Thermal conduction and free convection are assumed negligible compared to other effects included in the calculation. Results showing the important effect of water vapor concentration on beam quality are given. Beam slewing is also studied. Comparison is made with geometrical optics results, and good agreement is found with laboratory experiments that simulate atmospheric propagation.
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Study of Injection of Helium into Supersonic Air Flow Using Rayleigh Scattering
NASA Technical Reports Server (NTRS)
Seaholtz, Richard G.; Buggele, Alvin E.
1997-01-01
A study of the transverse injection of helium into a Mach 3 crossflow is presented. Filtered Rayleigh scattering is used to measure penetration and helium mole fraction in the mixing region. The method is based on planar molecular Rayleigh scattering using an injection-seeded, frequency-doubled ND:YAG pulsed laser and a cooled CCD camera. The scattered light is filtered with an iodine absorption cell to suppress stray laser light. Preliminary data are presented for helium mole fraction and penetration. Flow visualization images obtained with a shadowgraph and wall static pressure data in the vicinity of the injection are also presented.
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Laser Slowing of CaF Molecules and Progress towards a Dual-MOT for Li and CaF
NASA Astrophysics Data System (ADS)
Chae, Eunmi
Diatomic molecules are considered good candidates for the study of strongly correlated systems and precision measurement searches due to their combination of complex internal states and strong long-range interactions. Cooling molecules down to ultracold temperatures is often a necessary step for fully utilizing the power of the molecule. This requires a trap for molecules and the ability to cool molecules to the mK regime and below. A magneto-optical trap (MOT) is a good tool for achieving mK temperatures. However, extra care is needed for molecules to form the necessary quasi-closed cycling transitions due to molecule's complicated energy structure. In our work with CaF, we use two repump lasers to block vibrational leakage and selection rules for the rotational degree of freedom to achieve about 105 photon cycles. The two-stage buffer gas beam source is a general method to generate a cold and slow beam of molecules with a forward velocity of about 50 m/s. The compatibility of the buffer-gas source with a MOT is studied and we confirm that such beams can be nicely compatible with MOTs using various atomic species. In order to load molecules into a MOT from even such a slow beam, additional slowing is required due to the low capture velocity of a molecular MOT (< 10 m/s). We apply a frequency-broadened "white-light" slowing on CaF from a two-stage source, demonstrating slowing of CaF below 10 m/s. An AC MOT, which provides active remixing of dark substates, is also developed and Li atoms are slowed and trapped. These are crucial ingredients for co-trapping CaF molecules and Li atoms and study their collisional properties, which would lead to sympathetic cooling of molecules down to ultracold temperatures. The achievement of slowing and development of this system allowed for the detailed study of the CaF laser cooling system, as well as physical processes involved with AC MOTs and the proposed MOT for CaF. Crucial knowledge of this archetypal system provides significant progress toward manipulation and control of molecules similar to what has been achieved with atoms and what is necessary for searches for new physics with ultracold molecules.
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Development of thermally controlled HALNA DPSSL for inertial fusion energy
NASA Astrophysics Data System (ADS)
Matsumoto, Osamu; Yasuhara, Ryo; Kurita, Takashi; Ikegawa, Tadashi; Sekine, Takashi; Kawashima, Toshiyuki; Kawanaka, Junji; Norimatsu, Takayoshi; Miyanaga, Noriaki; Izawa, Yasukazu; Nakatsuka, Masahiro; Miyamoto, Masahiro; Kan, Hirofumi; Furukawa, Hiroyuki; Motokoshi, Shinji
2006-02-01
We have been developing a high average-power laser system for science and industry applications that can generate an output of 20 J per pulse at 10-Hz operation. Water-cooled Nd:glass zig-zag slab is pumped with 803-nm AlGaAs laser-diode modules. To efficiently extract energy from the laser medium, the laser beam alternately passes through dual zig-zag slab amplifier modules. Twin LD modules equipped on each slab amplifier module pump the laser medium with a peak power density of 2.5 kW/cm2. In high power laser system, thermal load in the laser medium causes serious thermal effects. We arranged cladding glasses on the top and bottom of the laser slab to reduce thermal effects.
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3D Printing Optical Engine for Controlling Material Microstructure
NASA Astrophysics Data System (ADS)
Huang, Wei-Chin; Chang, Kuang-Po; Wu, Ping-Han; Wu, Chih-Hsien; Lin, Ching-Chih; Chuang, Chuan-Sheng; Lin, De-Yau; Liu, Sung-Ho; Horng, Ji-Bin; Tsau, Fang-Hei
Controlling the cooling rate of alloy during melting and resolidification is the most commonly used method for varying the material microstructure and consequently the resuling property. However, the cooling rate of a selective laser melting (SLM) production is restricted by a preset optimal parameter of a good dense product. The head room for locally manipulating material property in a process is marginal. In this study, we invent an Optical Engine for locally controlling material microstructure in a SLM process. It develops an invovative method to control and adjust thermal history of the solidification process to gain desired material microstucture and consequently drastically improving the quality. Process parameters selected locally for specific materials requirement according to designed characteristics by using thermal dynamic principles of solidification process. It utilize a technique of complex laser beam shape of adaptive irradiation profile to permit local control of material characteristics as desired. This technology could be useful for industrial application of medical implant, aerospace and automobile industries.
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Neutral atom traps of rare isotopes
NASA Astrophysics Data System (ADS)
Mueller, Peter
2016-09-01
Laser cooling and trapping techniques offer exquisite control of an atom's external and internal degrees of freedom. The species of interest can be selectively captured, cooled close to absolute zero temperatures, and observed with high signal-to-noise ratio. Moreover, the atom's electronic and magnetic state populations can be precisely manipulated and interrogated. Applied in nuclear physics, these techniques are ideal for precision measurements in the fields of fundamental interactions and symmetries, nuclear structure studies, and isotopic trace analysis. In particular, they offer unique opportunities in the quest for physics beyond the standard model. I will shortly review the basics of this approach and the state of the field and then cover in more details recent results from two such efforts: the search for a permanent electric dipole moment in 225Ra and the beta-neutrino angular correlation measurement with laser trapped 6He. This work is supported by the U.S. DOE, Office of Science, Office of Nuclear Physics, under Contract DE-AC02-06CH11357.
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Laser cooling and control of excitations in superfluid helium
NASA Astrophysics Data System (ADS)
Harris, G. I.; McAuslan, D. L.; Sheridan, E.; Sachkou, Y.; Baker, C.; Bowen, W. P.
2016-08-01
Superfluidity is a quantum state of matter that exists macroscopically in helium at low temperatures. The elementary excitations in superfluid helium have been probed with great success using techniques such as neutron and light scattering. However, measurements of phonon excitations have so far been limited to average thermodynamic properties or the driven response far out of thermal equilibrium. Here, we use cavity optomechanics to probe the thermodynamics of phonon excitations in real time. Furthermore, strong light-matter interactions allow both laser cooling and amplification. This represents a new tool to observe and control superfluid excitations that may provide insight into phonon-phonon interactions, quantized vortices and two-dimensional phenomena such as the Berezinskii-Kosterlitz-Thouless transition. The third sound modes studied here also offer a pathway towards quantum optomechanics with thin superfluid films, including the prospect of femtogram masses, high mechanical quality factors, strong phonon-phonon and phonon-vortex interactions, and self-assembly into complex geometries with sub-nanometre feature size.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Jaeger, C.; Huisken, F.; Henning, Th.
2009-05-01
Carbonaceous grains represent a major component of cosmic dust. In order to understand their formation pathways, they have been prepared in the laboratory by gas-phase condensation reactions such as laser pyrolysis and laser ablation. Our studies demonstrate that the temperature in the condensation zone determines the formation pathway of carbonaceous particles. At temperatures lower than 1700 K, the condensation by-products are mainly polycyclic aromatic hydrocarbons (PAHs) that are also the precursors or building blocks for the condensing soot grains. The low-temperature condensates contain PAH mixtures that are mainly composed of volatile three to five ring systems. At condensation temperatures highermore » than 3500 K, fullerene-like carbon grains and fullerene compounds are formed. Fullerene fragments or complete fullerenes equip the nucleating particles. Fullerenes can be identified as soluble components. Consequently, condensation products in cool and hot astrophysical environments such as cool and hot asymptotic giant branch stars or Wolf-Rayet stars should be different and should have distinct spectral properties.« less
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Adaptive metal mirror for high-power CO2 lasers
NASA Astrophysics Data System (ADS)
Jarosch, Uwe-Klaus
1996-08-01
Spherical mirrors with a variable radius of curvature are used inside laser resonators as well as in the beam path between the laser and the workpiece. Commercially-available systems use piezoelectric actuators, or the pressure of the coolant, to deform the mirror surface. In both cases, the actuator and the cooling system influence each other. This interaction is avoided through the integration of the cooling system with the flexible mirror membrane. A multi- channel design leads to an optimized cooling effect, which is necessary for high power applications. The contour of the variable metal mirror depends on the mounting between the membrane and the mirror body and on the distribution of forces. Four cases of deformation can be distinguished for a circular elastic membrane. The realization of an adaptive metal mirror requires a technical compromise to be made. A mechanical construction is presented which combines an elastic hinge with the inlet and outlet of the coolant. For the deformation of the mirror membranes two actuators with different character of deformation are used. The superposition of the two deformations results in smaller deviations from the spherical surface shape than can be achieved using a single actuator. DC proportional magnets have been introduced as cheap and rigid actuators. The use of this adaptive mirror, either in a low pressure atmosphere of a gas laser resonator, or in an extra-cavity beam path is made possible through the use of a ventilation system.
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Linear lesions in heart tissue using diffused laser radiation
NASA Astrophysics Data System (ADS)
Fried, Nathaniel M.; Lardo, Albert C.; Berger, Ronald D.; Calkins, Hugh; Halperin, Henry R.
2000-05-01
Transmural, continuous, and linear lesions may be necessary for successful catheter ablation of cardiac arrythmias such as atrial fibrillation. Laser ablation was studied as an alternative to radiofrequency ablation, which is noted to produce superficial and discontinuous lesions as well as tissue charring and vaporization. Samples of canine myocardium were placed in a saline bath and irradiated with an 1.06- micrometer Nd:YAG laser operated in either pulsed or continuous mode. For pulsed mode, the laser pulse duration was 10 s with 10 s cooling between pulses. Laser radiation was delivered radially through diffusing optical fiber tips oriented parallel to the endocardial surface. In CW mode, transmural (6-mm-deep), linear (16-mm-long), and continuous lesions were produced using a laser power of 30 W and an irradiation time of 180 s. Peak tissue temperatures measured 51 plus or minus 1 degree Celsius at the endocardial surface, 61 plus or minus 6 degrees Celsius in the mid-myocardium, and 55 plus or minus 6 degree Celsius at the epicardial surface. There was no evidence of tissue charring or vaporization. Pulsed laser irradiation produced comparable lesion depths to CW irradiation with more uniform heating of the subsurface myocardium, but at the expense of longer operation times. Further in vivo study of laser ablation is warranted for possible clinical applications.
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Wittig, Curt; Tiee, Joe J.
1979-01-01
A CF.sub.4 laser for producing near 16 .mu.m radiation utilizing a line tunable CO.sub.2 laser as an optical pumping source. The device uses a cryogenically cooled optically pumped cell containing molecular CF.sub.4 gas. An optical resonant cavity formed around the optically pumped cell induces oscillations of near 16 .mu.m radiation from the .nu..sub.2 +.nu..sub.4 .fwdarw..nu..sub.2 transition in the molecular CF.sub.4 gas.
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Stackable air-cooled heatsinks for diode lasers
NASA Astrophysics Data System (ADS)
Crum, T. R.; Harrison, J.; Srinivasan, R.; Miller, R. L.
2007-02-01
Micro-channel heatsink assemblies made from bonding multi-layered etched metal sheets are commercially available and are often used for removing the high waste heat loads generated by the operation of diode-laser bars. Typically, a diode-laser bar is bonded onto a micro-channel (also known as mini-channel) heatsink then stacked in an array to create compact high power diode-laser sources for a multitude of applications. Under normal operation, the diode-laser waste heat is removed by passing coolant (typically de-ionized water) through the channels of the heatsink. Because of this, the heatsink internal structure, including path length and overall channel size, is dictated by the liquid coolant properties. Due to the material characteristics of these conductive heatsinks, and the necessary electrically serial stacking geometry, there are several restrictions imparted on the coolant liquid to maintain performance and lifetime. Such systems require carefully monitored and conductive limited de-ionized water, as well as require stable pH levels, and suitable particle filtration. These required coolant systems are either stand alone, or heat exchangers are typically costly and heavy restricting certain applications where minimal weight to power ratios are desired. In this paper, we will baseline the existing water cooled Spectra-Physics Monsoon TM heatsink technology utilizing compressed air, and demonstrate a novel modular stackable heatsink concept for use with gaseous fluids that, in some applications may replace the existing commercially available water-cooled heatsink technology. We will explain the various benefits of utilizing air while maintaining mechanical form factors and packing densities. We will also show thermal-fluid modeling results and predictions as well as operational performance curves for efficiency and power and compare these data to the existing commercially available technology.
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Superconducting thin films of Bi-Sr-Ca-Cu-O by laser ablation
NASA Astrophysics Data System (ADS)
Bedekar, M. M.; Safari, A.; Wilber, W.
1992-11-01
Superconducting thin films of Bi-Sr-Ca-Cu-O have been deposited by KrF excimer laser ablation. The best in situ films showed a Tc onset of 110 K and a Tc(0) of 76 K. A study of the laser plume revealed the presence of two distinct regimes. The forward directed component increased with fluence and the film composition was stoichiometric in this region. This is in agreement with the results on the 123 system by Venkatesan et al. [1]. The film properties were found to be critically dependent on the substrate temperature and temperatures close to melting gave rise to 2212 and 2223 phases. At lower temperatures, 2201 and amorphous phases were obtained. The film morphology and superconducting properties were a function of the target to substrate distance and the oxygen pressure during deposition and cooling. An increase in the target to substrate distance led to a deterioration of the properties due to the energy consideration for the formation of 2212 and 2223 phases. The best films were obtained using cooling pressures of 700 Torr. The microwave surface resistance of the films measured at 35 GHz dropped below that of copper at 30 K. Film growth was studied using X-ray diffraction and STM/AFM. This work is a discussion of the role of the different variables on the film properties.
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Picosecond lasers: the next generation of short-pulsed lasers.
Freedman, Joshua R; Kaufman, Joely; Metelitsa, Andrea I; Green, Jeremy B
2014-12-01
Selective photothermolysis, first discussed in the context of targeted microsurgery in 1983, proposed that the optimal parameters for specific thermal damage rely critically on the duration over which energy is delivered to the tissue. At that time, nonspecific thermal damage had been an intrinsic limitation of all commercially available lasers, despite efforts to mitigate this by a variety of compensatory cooling mechanisms. Fifteen years later, experimental picosecond lasers were first reported in the dermatological literature to demonstrate greater efficacy over their nanosecond predecessors in the context of targeted destruction of tattoo ink. Within the last 4 years, more than a decade after those experiments, the first commercially available cutaneous picosecond laser unit became available (Cynosure, Westford, Massachusetts), and several pilot studies have demonstrated its utility in tattoo removal. An experimental picosecond infrared laser has also recently demonstrated a nonthermal tissue ablative capability in soft tissue, bone, and dentin. In this article, we review the published data pertaining to dermatology on picosecond lasers from their initial reports to the present as well as discuss forthcoming technology.
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Selective ablation of dental calculus with a frequency-doubled Alexandrite laser
NASA Astrophysics Data System (ADS)
Rechmann, Peter; Hennig, Thomas
1996-01-01
The aim of the study was the selective removal of dental calculus by means of pulsed lasers. In a first approach the optical characteristics of subgingival calculus were calculated using fluorescence emission spectroscopy (excitation laser: N2-laser, wavelength 337 nm, pulse duration 4 ns). Subgingival calculus seems to absorb highly in the ultraviolet spectral region up to 420 nm. According to these measurements a frequency doubled Alexandrite-laser (wavelength 377 nm, pulse duration 100 ns, repetition rate 110 Hz) was used to irradiate calculus located on enamel, at the cementum enamel junction and on the root surface (located on dentin or on cementum). Irradiation was performed perpendicular to the root surface with a laser fluence of 1 Jcm-2. During the irradiation procedure an effective water cooling-system was engaged. Histological investigations were done on undecalcified sections. As a result, engaging low fluences allows a fast and strictly selective removal of subgingival calculus. Even more the investigations revealed that supragingival calculus can be removed in a strictly selective manner engaging a frequency doubled Alexandrite-laser. No adverse side effects to the surrounding tissues could be found.
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Why Aren’t Lightsabers Real Yet? Get the Lowdown from a Laser Physicist
DOE Office of Scientific and Technical Information (OSTI.GOV)
Hunsberger, Maren; Liao, Zhi
The release of "Star Wars: The Force Awakens" begs the obvious question: Why aren't lightsabers real yet? LLNL science communicator Maren Hunsberger gets the lowdown from laser physicist Zhi Liao in this first installment of "Inside the Lab," a new YouTube series exploring crazy-cool science questions.
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3D analysis of thermal and stress evolution during laser cladding of bioactive glass coatings.
Krzyzanowski, Michal; Bajda, Szymon; Liu, Yijun; Triantaphyllou, Andrew; Mark Rainforth, W; Glendenning, Malcolm
2016-06-01
Thermal and strain-stress transient fields during laser cladding of bioactive glass coatings on the Ti6Al4V alloy basement were numerically calculated and analysed. Conditions leading to micro-cracking susceptibility of the coating have been investigated using the finite element based modelling supported by experimental results of microscopic investigation of the sample coatings. Consecutive temperature and stress peaks are developed within the cladded material as a result of the laser beam moving along the complex trajectory, which can lead to micro-cracking. The preheated to 500°C base plate allowed for decrease of the laser power and lowering of the cooling speed between the consecutive temperature peaks contributing in such way to achievement of lower cracking susceptibility. The cooling rate during cladding of the second and the third layer was lower than during cladding of the first one, in such way, contributing towards improvement of cracking resistance of the subsequent layers due to progressive accumulation of heat over the process. Copyright © 2016 Elsevier Ltd. All rights reserved.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Gumenyuk, Regina; Okhotnikov, Oleg G.; Golant, Konstantin
2011-05-09
The experimental evidence of laser transition type in bismuth-doped silica fibers operating at different spectral bands is presented. Spectrally resolved transient (relaxation) oscillations studied for a Bi-doped fiber laser at room and liquid-nitrogen temperatures allow to identify the three- and four-level energy bands. 1.18 {mu}m short-wavelength band is found to be a three-level system at room temperature with highly populated terminal energy level of laser transition. The depopulation of ground level by cooling the fiber down to liquid-nitrogen temperature changes the transition to four-level type. Four-level energy transition distinguished at 1.32 {mu}m exhibits the net gain at room temperature.
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NASA Astrophysics Data System (ADS)
Werth, Alexandra; Liakat, Sabbir; Dong, Anqi; Woods, Callie M.; Gmachl, Claire F.
2018-05-01
An integrating sphere is used to enhance the collection of backscattered light in a noninvasive glucose sensor based on quantum cascade laser spectroscopy. The sphere enhances signal stability by roughly an order of magnitude, allowing us to use a thermoelectrically (TE) cooled detector while maintaining comparable glucose prediction accuracy levels. Using a smaller TE-cooled detector reduces form factor, creating a mobile sensor. Principal component analysis has predicted principal components of spectra taken from human subjects that closely match the absorption peaks of glucose. These principal components are used as regressors in a linear regression algorithm to make glucose concentration predictions, over 75% of which are clinically accurate.
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Spectroscopic Properties and Laser Performance of Resonantly-Pumped Cryo-Cooled Er3+:GdVO4
2012-03-12
measured at 77 K. The results for the entire temperature range of 77-300K, presented in Fig. 2(a), were consistent with those measured by Bertini et al ...also consistent with that reported by Bertini et al [15]. 3. Cryogenic laser experiments Laser experiments were carried out on an anti-reflection...Dinndorf, J. A. Beattie, and E. P. Chicklis, “A 400 W cryogenic Er:YAG slab laser at 1645 nm,” Proc. SPIE 7686, 76860C, C7 ( 2010 ). 2. N. Ter
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Investigation on the optimized heat treatment procedure for laser fabricated IN718 alloy
NASA Astrophysics Data System (ADS)
Zhang, Yaocheng; Yang, Li; Chen, Tingyi; Zhang, Weihui; Huang, Xiwang; Dai, Jun
2017-12-01
The laser fabricated IN718 alloys were prepared by laser cladding system. The microstructure and microhardness of laser fabricated IN718 alloys were investigated after heat treatment. The microstructure and the elevated temperature mechanical properties of laser fabricated IN718 alloys were analyzed. The results showed that the microstructure of laser fabricated IN718 alloy consisted of austenitic matrix and dendritic Laves/γ eutectic. Most all Laves/γ eutectic was dissolved into austenitic matrix, and the complete recrystallization and the large grains occurred in the laser fabricated IN718 alloy after homogenization at 1080-1140 °C for 1 h, the dendritic Laves/γ eutectic was refined and the partial recrystallization occurred during the solid solution at 940-1000 °C for 1.5 h, the microhardness of the double aging (DA) alloys was about more than twice that of as-fabricated IN718 alloy. The recrystallized microstructure was obtained in the heat-treated laser fabricated IN718 alloy after 1100 °C/1 h air cooling (AC), 980 °C/1.5 h (AC), 700 °C/8 h furnace cooling (FC, 100 °C/h) to 600 °C/8 h (AC). The microhardness and the elevated temperature tensile strength were more than twice that of as-fabricated IN718 alloy due to a large concentration of γ″ phase precipitation to improve the transgranular strength and large grain to guarantee the grain boundary strength. The fracture morphologies of as-fabricated and heat-treated laser fabricated IN718 alloys were presented as the fiber dimples, the fracture mechanism of as-fabricated and heat-treated laser fabricated IN718 alloys was ductile fracture.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Khabibullin, R. A., E-mail: khabibullin@isvch.ru; Shchavruk, N. V.; Klochkov, A. N.
The dependences of the electronic-level positions and transition oscillator strengths on an applied electric field are studied for a terahertz quantum-cascade laser (THz QCL) with the resonant-phonon depopulation scheme, based on a cascade consisting of three quantum wells. The electric-field strengths for two characteristic states of the THz QCL under study are calculated: (i) “parasitic” current flow in the structure when the lasing threshold has not yet been reached; (ii) the lasing threshold is reached. Heat-transfer processes in the THz QCL under study are simulated to determine the optimum supply and cooling conditions. The conditions of thermocompression bonding of themore » laser ridge stripe with an n{sup +}-GaAs conductive substrate based on Au–Au are selected to produce a mechanically stronger contact with a higher thermal conductivity.« less
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Torres, J H; Tunnell, J W; Pikkula, B M; Anvari, B
2001-01-01
Cryogen spray cooling (CSC) is a method used to protect the epidermis from non-specific thermal injury that may occur as a result of various dermatological laser procedures. However, better understanding of cryogen deposition and skin thermal response to CSC is needed to optimize the technique. Temperature measurements and video imaging were carried out on an epoxy phantom as well as human skin during CSC with and without simultaneous application of airflow which was intended to accelerate cryogen evaporation from the substrate surface. An inverse thermal conduction model was used to estimate heat flux and total heat removed. Lifetime of the cryogen film deposited on the surface of skin and epoxy phantom lasted several hundred milliseconds beyond the spurt, but could be reduced to the spurt duration by application of airflow. Values over 100 J/cm(3) were estimated for volumetric heat removed from the epidermis using CSC. "Film cooling" instead of "evaporative cooling" appears to be the dominant mode of CSC on skin. Estimated values of heat removed from the epidermis suggest that a cryogen spurt as long as 200 milliseconds is required to counteract heat generated by high laser fluences (e.g., in treatment of port wine stains) in patients with high concentration of epidermal melanin. Additional cooling beyond spurt termination can be avoided by simultaneous application of airflow, although it is unclear at the moment if avoiding the additional cooling would be beneficial in the actual clinical situation. Copyright 2001 Wiley-Liss, Inc.
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"Application of Tunable Diode Laser Spectrometry to Isotopic Studies for Exobiology"
NASA Technical Reports Server (NTRS)
Sauke, Todd B.
1999-01-01
Computer-controlled electrically-activated valves for rapid gas-handling have been incorporated into the Stable Isotope Laser Spectrometer (SILS) which now permits rapid filling and evacuating of the sample and reference gas cells, Experimental protocols have been developed to take advantage of the fast gas handling capabilities of the instrument and to achieve increased accuracy which results from reduced instrumental drift during rapid isotopic ratio measurements. Using these protocols' accuracies of 0.5 del (0.05%) have been achieved in measurements of 13C/12C in carbon dioxide. Using the small stable isotope laser spectrometer developed in a related PIDDP project of the Co-I, protocols for acquisition of rapid sequential calibration spectra were developed which resulted in 0.5 del accuracy also being achieved in this less complex instrument. An initial version of software for automatic characterization of tunable diode lasers has been developed and diodes have been characterized in order to establish their spectral output properties. A new state-of-the-art high operating temperature (200 K) mid infrared diode laser was purchased (through NASA procurement) and characterized. A thermo-electrically cooled mid infrared tunable diode laser system for use with high temperature operation lasers was developed. In addition to isotopic ratio measurements of carbon and oxygen, measurements of a third biologically important element (15N/14N in N2O gas) have been achieved to a preliminary accuracy of about 0.2%. Transfer of the basic SILS technology to the commercial sector is proceeding under an unfunded Space Act Agreement between NASA and SpiraMed, a medical diagnostic instrument company. Two patents have been issued. Foreign patents based on these two US patents have been applied for and are expected to be issued. A preliminary design was developed for a thermo-electrically cooled SILS instruments for application to planetary space flight exploration missions.
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Analysis of violet-excited fluorochromes by flow cytometry using a violet laser diode.
Telford, William G; Hawley, Teresa S; Hawley, Robert G
2003-07-01
Low power violet laser diodes (VLDs) have been evaluated as potential replacements for water-cooled argon-ion and krypton-ion ultraviolet and violet lasers for DNA content analysis using the Hoechst dyes and 4,6-diamidino-2-phenylindole (Shapiro HMN, Perlmutter NG: Cytometry 44:133-136, 2001). In this study, we used a VLD to excite a variety of violet-excited fluorescent molecules important in biomedical analysis, including the fluorochromes Cascade Blue and Pacific Blue, the expressible fluorescent protein cyan fluorescent protein (CFP), and the fluorogenic alkaline phosphatase (AP) substrate 2-(5'-chloro-2'-phosphoryloxyphenyl)-6-chloro-4-(3H)-quinazoline (ELF-97; for endogenous AP detection and cell surface labeling with AP-conjugated antibodies). Comparisons were made between VLD excitation and a krypton-ion laser emitting at 407 nm (both at higher power levels and with the beam attenuated at levels approximating the VLD) on the same FACSVantage SE stream-in-air flow cytometer. We evaluated a Power Technology 408-nm VLD (30 mW) equipped with circularization optics (18 mW maximum output, set to 15 mW) and a Coherent I-302C krypton-ion laser emitting at power levels ranging from 15 to 75 mW. Cascade Blue, Pacific Blue, and CFP showed comparable signal-to-noise ratios and levels of sensitivity with VLD excitation versus the krypton-ion laser at high and VLD-matched power outputs. Multicolor fluorescent protein analysis with 488-nm excitation of green fluorescent protein and DsRed and VLD excitation of CFP was therefore feasible and was demonstrated. Similar levels of excitation efficiency between krypton-ion and VLD sources also were observed for ELF-97 detection. These evaluations confirmed that VLDs may be cost- and maintenance-effective replacements for water-cooled gas lasers for applications requiring violet excitation in addition to DNA binding dyes. Published 2003 Wiley-Liss, Inc.
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NASA Astrophysics Data System (ADS)
Melgaard, Seth D.; Seletskiy, Denis V.; Di Lieto, Alberto; Tonelli, Mauro; Sheik-Bahae, Mansoor
2012-03-01
Since recent demonstration of cryogenic optical refrigeration, a need for reliable characterization tools of cooling performance of different materials is in high demand. We present our experimental apparatus that allows for temperature and wavelength dependent characterization of the materials' cooling efficiency and is based on highly sensitive spectral differencing technique or two-band differential spectral metrology (2B-DSM). First characterization of a 5% w.t. ytterbium-doped YLF crystal showed quantitative agreement with the current laser cooling model, as well as measured a minimum achievable temperature (MAT) at 110 K. Other materials and ion concentrations are also investigated and reported here.
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Efficient cooling of quantized vibrations using a four-level configuration
NASA Astrophysics Data System (ADS)
Yan, Lei-Lei; Zhang, Jian-Qi; Zhang, Shuo; Feng, Mang
2016-12-01
Cooling vibrational degrees of freedom down to ground states is essential to observation of quantum properties of systems with mechanical vibration. We propose two cooling schemes employing four internal levels of the systems, which achieve the ground-state cooling in an efficient fashion by completely deleting the carrier and first-order blue-sideband transitions. The schemes, based on quantum interference and Stark-shift gates, are robust to fluctuations of laser intensity and frequency. The feasibility of the schemes is justified using current laboratory technology. In practice, our proposal readily applies to a nanodiamond nitrogen-vacancy center levitated in an optical trap or attached to a cantilever.