Self-compensation of thermal lens in high-power diode pumped solid-state lasers

NASA Astrophysics Data System (ADS)

Wang, Xiao-Jun

2010-02-01

We present a comprehensive model to describe the optic-thermal coupling in the diode pumped solid-state lasers (DPSSL). The thermal transition of particles at the upper laser level leads the heat-generation of laser crystals to depend on shape of the laser beam, while the laser field is also influenced by the temperature because of the thermal excitation of doped particles among various Stark levels. These effects, together with the usual thermal-optic effect that induces a fluctuation of the refraction index by an inhomogeneous temperature distribution, cause a complicated coupling between the laser field and the temperature field. We show that the optic-thermal coupling plays an important role in high-power DPSSL with larger size beam. That effect may yield a self-compensation for the thermal lens and improve the beam quality.

Comparative study of upper lip frenectomy with the CO2 laser versus the Er, Cr: YSGG laser

PubMed Central

Pié-Sánchez, Jordi; España-Tost, Antonio J.; Arnabat-Domínguez, Josep

2012-01-01

Objectives: To compare upper lip frenulum reinsertion, bleeding, surgical time and surgical wound healing in frenectomies performed with the CO2 laser versus the Er, Cr:YSGG laser. Study design: A prospective study was carried out on 50 randomized pediatric patients who underwent rhomboidal resection of the upper lip frenulum with either the CO2 laser or the Er,Cr:YSGG laser. Twenty-five patients were assigned to each laser system. All patients were examined at 7, 14, 21 days and 4 months after the operation in order to assess the surgical wound healing. Results: Insertion of the frenulum, which was preoperatively located between the upper central incisors, migrated to the mucogingival junction as a result of using both laser systems in all patients. Only two patients required a single dose of 650 mg of paracetamol, one of either study group. CO2 laser registered improved intraoperative bleeding control results and shorter surgical times. On the other hand, the Er,Cr:YSGG laser achieved faster healing. Conclusions: Upper lip laser frenectomy is a simple technique that results in minimum or no postoperative swelling or pain, and which involves upper lip frenulum reinsertion at the mucogingival junction. The CO2 laser offers a bloodless field and shorter surgical times compared with the Er,Cr:YSGG laser. On the other hand, the Er,Cr:YSGG laser achieved faster wound healing. Key words:Frenectomy, upper lip frenulum, CO2 laser, Er,Cr:YSGG laser, laser. PMID:22143683

Diatomic gasdynamic lasers.

NASA Technical Reports Server (NTRS)

Mckenzie, R. L.

1972-01-01

Predictions from a numerical model of the vibrational relaxation of anharmonic diatomic oscillators in supersonic expansions are used to show the extent to which the small anharmonicity of gases like CO can cause significant overpopulations of upper vibrational states. When mixtures of CO and N2 are considered, radiative gain on many of the vibration-rotation transitions of CO is predicted. Experiments are described that qualitatively verify the predictions by demonstrating laser oscillation in CO-N2 expansions. The resulting CO-N2 gasdynamic laser displays performance characteristics that equal or exceed those of similar CO2 lasers.

Diatomic gasdynamic lasers

NASA Technical Reports Server (NTRS)

Mckenzie, R. L.

1971-01-01

Predictions from a numerical model of the vibrational relaxation of anharmonic diatomic oscillators in supersonic expansions are used to show the extent to which the small anharmonicity of gases like CO can cause significant overpopulations of upper vibrational states. When mixtures of CO and N2 are considered, radiative gain on many of the vibration-rotation transitions of CO is predicted. Experiments are described that qualitatively verify the predictions by demonstrating laser oscillation in CO-N2 expansions. The resulting CO-N2 gasdynamic laser displays performance characteristics that equal or exceed those of similar CO2 lasers.

1.9 THz Quantum-cascade Lasers with One-well Injector

NASA Technical Reports Server (NTRS)

Kumar, Sushil; Williams, Benjamin S.; Hu, Qing; Reno, John L.

2006-01-01

We report terahertz quantum-cascade lasers operating predominantly at 1.90 THz with side modes as low as 1.86 THz (lambda approx. equal to 161 micrometers, planck's constant omega approx. equal to 7.7 meV). This is the longest wavelength to date of any solid-state laser that operates without assistance of a magnetic field. Carriers are injected into the upper radiative state by using a single quantum-well injector, which resulted in a significant reduction of free-carrier losses. The laser operated up to a heat-sink temperature of 110 K in pulsed mode, 95 K in continuous wave (cw) mode, and the threshold current density at 5 K was approx. 140 A per square centimeters.

Terahertz generation in mid-infrared quantum cascade lasers with a dual-upper-state active region

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fujita, Kazuue, E-mail: kfujita@crl.hpk.co.jp; Hitaka, Masahiro; Ito, Akio

2015-06-22

We report the performance of room temperature terahertz sources based on intracavity difference-frequency generation in mid-infrared quantum cascade lasers with a dual-upper-state (DAU) active region. DAU active region design is theoretically expected to produce larger optical nonlinearity for terahertz difference-frequency generation, compared to the active region designs of the bound-to-continuum type used previously. Fabricated buried heterostructure devices with a two-section buried distributed feedback grating and the waveguide designed for Cherenkov difference-frequency phase-matching scheme operate in two single-mode mid-infrared wavelengths at 10.7 μm and 9.7 μm and produce terahertz output at 2.9 THz with mid-infrared to terahertz conversion efficiency of 0.8 mW/W{sup 2}more » at room temperature.« less

New laser materials for laser diode pumping

NASA Technical Reports Server (NTRS)

Jenssen, H. P.

1990-01-01

The potential advantages of laser diode pumped solid state lasers are many with high overall efficiency being the most important. In order to realize these advantages, the solid state laser material needs to be optimized for diode laser pumping and for the particular application. In the case of the Nd laser, materials with a longer upper level radiative lifetime are desirable. This is because the laser diode is fundamentally a cw source, and to obtain high energy storage, a long integration time is necessary. Fluoride crystals are investigated as host materials for the Nd laser and also for IR laser transitions in other rare earths, such as the 2 micron Ho laser and the 3 micron Er laser. The approach is to investigate both known crystals, such as BaY2F8, as well as new crystals such as NaYF8. Emphasis is on the growth and spectroscopy of BaY2F8. These two efforts are parallel efforts. The growth effort is aimed at establishing conditions for obtaining large, high quality boules for laser samples. This requires numerous experimental growth runs; however, from these runs, samples suitable for spectroscopy become available.

A high-pressure carbon dioxide gasdynamic laser

NASA Technical Reports Server (NTRS)

Kuehn, D. M.

1973-01-01

A carbon dioxide gasdynamic laser was operated over a range of reservoir pressure and temperature, test-gas mixture, and nozzle geometry. A significant result is the dominant influence of nozzle geometry on laser power at high pressure. High reservoir pressure can be effectively utilized to increase laser power if nozzle geometry is chosen to efficiently freeze the test gas. Maximum power density increased from 3.3 W/cu cm of optical cavity volume for an inefficient nozzle to 83.4 W/cu cm at 115 atm for a more efficient nozzle. Variation in the composition of the test gas also caused large changes in laser power output. Most notable is the influence of the catalyst (helium or water vapor) that was used to depopulate the lower vibrational state of the carbon dioxide. Water caused an extreme deterioration of laser power at high pressure (100 atm), whereas, at low pressure the laser for the two catalysts approached similar values. It appears that at high pressure the depopulation of the upper laser level of the carbon dioxide by the water predominates over the lower state depopulation, thus destroying the inversion.

Generation of high powers from diode pumped chromium-3+ doped colquiriites

NASA Astrophysics Data System (ADS)

Eichenholz, Jason Matthew

1998-12-01

There is considerable interest in the area of laser diode pumped solid-state lasers. Diode pumped solid-state lasers (DPSSL) operating at high average power levels are attractive light sources for various applications such as materials processing, laser radar, and fundamental physics experiments. These laser systems have become more commonplace because of their efficiency, reliability, compactness, low relative cost, and long operational lifetimes. Induced thermal effects in the solid-state laser medium hinder the scaling of DPSSL's to higher average power levels. Therefore a deep insight into the thermo-mechanical properties of the solid state laser is crucial in order to ensure a laser design which is optimized for high average power operation. A comprehensive study of the factors that contribute to thermal loading of the colquiriites was performed. A three-dimensional thermal model has been created to determine the temperature rise inside the laser crystal. This new model calculates the temperature distribution by considering quantum defect, upconversion, and upper-state lifetime quenching as heating sources. The thermally induced lensing in end pumped Cr3+ doped LiSrAlF6, LiSrGaF6, LiSrCaAlF6, and LiCaAlF6 were experimentally measured. Several diode pumped colquiriite laser systems were assembled to quantitatively observe and identify thermally induced effects. Significant differences in each of the colquiriite materials were observed. These differences are explained by the differences in the thermo-mechanical and thermo-optical properties of the material and are explained by the theoretical thermal model.

Upper Eyelid Fractional CO2 Laser Resurfacing With Incisional Blepharoplasty.

PubMed

Kotlus, Brett S; Schwarcz, Robert M; Nakra, Tanuj

2016-01-01

Laser resurfacing, performed at the same time as blepharoplasty, has most commonly been applied to the lower eyelid skin but can effectively be used on the upper eyelid to reduce rhytidosis and improve skin quality. The authors evaluate the safety and efficacy of this procedure. Fractional CO2 laser resurfacing was performed in conjunction with incisional upper blepharoplasty. The ultrapulsed laser energy was applied to the sub-brow skin, the upper medial canthal skin, and the pretarsal skin in 30 patients. Photos were obtained preoperatively and at 3 months. All patients demonstrated reduction in upper eyelid rhytidosis without any serious complications. Independent rhytidosis grading (0-4) showed a mean improvement of 42%. One patient experienced wound dehiscence that satisfactorily resolved without intervention. Upper eyelid laser resurfacing is effective and can be safely performed at the same time as upper blepharoplasty. This approach reduces or eliminates the need for medial incisions to address medial canthal skin redundancy and rhytidosis and it directly treats upper eyelid wrinkles on residual eyelid and infra-brow skin during blepharoplasty.

Characteristics of AFB interfaces of dissimilar crystal composites as components for solid state lasers

NASA Astrophysics Data System (ADS)

Lee, H. C.; Meissner, O. R.; Meissner, H. E.

2005-06-01

Adhesive-free bonded (AFB®) composite crystals have proven to be useful components in diode-pumped solid-state lasers (DPSSL). The combination of a lasing medium of higher index of refraction with laser-inactive cladding layers of lower index results in light- or wave-guided slab architectures. The cladding layers also serve to provide mechanical support, thermal uniformity and a heat sink during laser operation. Therefore, the optical and mechanical properties of these components are of interest for the design of DPSSL, especially at high laser fluencies and output power. We report on process parameters and material attributes that result in stress-free AFB® composites that are resistant to thermally induced failure. Formation of stress-free and durable bonds between two dissimilar materials requires heat-treatment of composites to a temperature high enough to ensure durable bonds and low enough to prevent forming of permanent chemical bonds. The onset temperature for forming permanent bonds at the interface sets the upper limit for heat treatment. This limiting temperature is dependent on the chemical composition, crystallographic orientation, and surface characteristics. We have determined the upper temperature limits for forming stress-free bonds between YAG and sapphire, YAG and GGG, YAG and spinel, spinel and sapphire, spinel and GGG, and sapphire and GGG composites. We also deduce the relative magnitude of thermal expansion coefficients amongst the respective single crystals as αGGG > αsapp_c > αspinel > αYAG > αsapp_a from interferometric analysis.

Titanium-doped sapphire laser research and design study

NASA Technical Reports Server (NTRS)

Moulton, Peter F.

1987-01-01

Three main topics were considered in this study: the fundamental laser parameters of titanium-doped sapphire, characterization of commercially grown material, and design of a tunable, narrow-linewidth laser. Fundamental parameters investigated included the gain cross section, upper-state lifetime as a function of temperature and the surface-damage threshold. Commercial material was found to vary widely in the level of absorption of the laser wavelength with the highest absorption in Czochralski-grown crystals. Several Yi:sapphire lasers were constructed, including a multimode laser with greater than 50mJ of output energy and a single-transverse-mode ring laser, whose spectral and temporal characteristics were completely characterized. A design for a narrow-linewidth (single-frequency) Ti:sapphire laser was developed, based on the results of the experimental work. The design involves the use of a single-frequency, quasi-cw master oscillator, employed as an injection source for a pulsed ring laser.

Few-mode vertical-cavity surface-emitting laser: Optional emission of transverse modes with different polarizations

NASA Astrophysics Data System (ADS)

Zhong, Chuyu; Zhang, Xing; Hofmann, Werner; Yu, Lijuan; Liu, Jianguo; Ning, Yongqiang; Wang, Lijun

2018-05-01

Few-mode vertical-cavity surface-emitting lasers that can be controlled to emit certain modes and polarization states simply by changing the biased contacts are proposed and fabricated. By directly etching trenches in the p-doped distributed Bragg reflector, the upper mesa is separated into several submesas above the oxide layer. Individual contacts are then deposited. Each contact is used to control certain transverse modes with different polarization directions emitted from the corresponding submesa. These new devices can be seen as a prototype of compact laser sources in mode division multiplexing communications systems.

Aircraft-borne, laser-induced fluorescence instrument for the in situ detection of hydroxyl and hydroperoxyl radicals

NASA Technical Reports Server (NTRS)

Wennberg, P. O.; Cohen, R. C.; Hazen, N. L.; Lapson, L. B.; Allen, N. T.; Hanisco, T. F.; Oliver, J. F.; Lanham, N. W.; Demusz, J. N.; Anderson, J. G.

1994-01-01

The odd-hydrogen radicals OH and HO2 are central to most of the gas-phase chemical transformations that occur in the atmosphere. Of particular interest is the role that these species play in controlling the concentration of stratospheric ozone. This paper describes an instrument that measures both of these species at volume mixing ratios below one part in 10(exp 14) in the upper troposphere and lower stratosphere. The hydroxyl radical (OH) is measured by laser induced fluorescence at 309 nm. Tunable UV light is used to pump OH to the first electric state near 282 nm. the laser light is produced by a high-repetition rate pulsed dye-laser powered with all solid-state pump lasers. HO2 is measured as OH after gas-phase titration with nitric oxide. Measurements aboard a NASA ER-2 aircraft demonstrate the capability of this instrument to perform reliably with very high signal-to-noise ratios (greater than 30) achieved in short integration times (less than 20 sec).

Efficient laser operation of Nd3+:Lu2O3 at various wavelengths between 917 nm and 1463 nm

NASA Astrophysics Data System (ADS)

von Brunn, P.; Heuer, A. M.; Fornasiero, L.; Huber, G.; Kränkel, C.

2016-08-01

Even though the first Nd3+-doped sesquioxide lasers have been realized more than 50 years ago, up to now no reports on efficient laser operation of Nd3+:doped sesquioxides can be found. In this work, we review the favorable spectroscopic properties of the sesquioxide Nd3+:Lu2O3 in terms of ground state absorption, stimulated emission, and excited state absorption cross sections as well as the upper level lifetime. Making use of these properties, we achieved efficient laser performance on eight different laser transitions in the wavelength range between 917 nm and 1463 nm under Ti:sapphire laser pumping using state-of-the-art HEM-grown Nd3+:Lu2O3 crystals with good optical quality. At the strongest transition around 1076 nm we determined a slope efficiency of 69%, which represents the highest efficiency ever obtained for a Nd3+-doped sesquioxide. Furthermore, we could generate watt level output powers and high slope efficiencies for seven other transitions. Lasers at 917 nm, 1053 nm, 1108 nm and 1463 nm were realized for the first time and the latter represents one of the longest laser wavelengths obtained on the 4F3/2  →  4I13/2 transition in Nd3+-doped materials.

Solid State Research.

DTIC Science & Technology

1984-02-15

Diode Lasers 10 - 3. MATERIALS RESEARCH 15 3.1 Role of Oxygen in Zone-Melting Recrystallization of Si Films on Si0 2 -Coated Si Substrates 15 3.2 Triple... Film that Has Been Etch-Delineated to Show Sub- ndaries. Upper Graphite Heater Was Scanned in Direction from top to Bottom of Micrograph. 15 3-2...Operation at 1060 nm with a 5-percent differential power efficiency has been obtained from a flashlamp-pumped laser rod of the sensitized garnet Nd:Cr:Gd 3Sc

Strong Einstein-Podolsky-Rosen steering with unconditional entangled states

NASA Astrophysics Data System (ADS)

Steinlechner, Sebastian; Bauchrowitz, Jöran; Eberle, Tobias; Schnabel, Roman

2013-02-01

In 1935 Schrödinger introduced the terms entanglement and steering in the context of the famous gedanken experiment discussed by Einstein, Podolsky, and Rosen (EPR). Here, we report on a sixfold increase of the observed EPR-steering effect with regard to previous experiments, as quantified by the Reid criterion. We achieved an unprecedented low conditional variance product of about 0.04<1, where 1 is the upper bound below which steering is demonstrated. The steering effect was observed on an unconditional two-mode-squeezed entangled state that contained a total vacuum state contribution of less than 8%, including detection imperfections. Together with the achieved high interference contrast between the entangled state and a bright coherent laser field, our state is compatible with efficient applications in high-power laser interferometers and fiber-based networks for entanglement distribution.

History, instrumentation, and techniques of flexible endoscopic laser surgery in horses.

PubMed

Blikslager, A T; Tate, L P

2000-08-01

There are clearly a number of applications for which flexible endoscopic laser surgery has become the state of the art in equine surgery, and the Nd:YAG laser seems to be the most versatile instrument for this type of surgery. Nevertheless, it is critical to understand the advantages and disadvantages of each laser technique. For example, the Nd:YAG laser used in a noncontact fashion seems to be superior when ablation of tissue is required such as treatment of upper airway masses. Conversely, contact Nd:YAG laser techniques have proven themselves to be superior when more precise cutting is advantageous such as treatment of epiglottic entrapment. Ultimately, it seems that a range of lasers is necessary to ensure selection of the most appropriate technique, adding significantly to the expense of equipment but improving the outcome for a range of equine diseases.

Continuous-wave sodium D2 resonance radiation generated in single-pass sum-frequency generation with periodically poled lithium niobate.

PubMed

Yue, J; She, C-Y; Williams, B P; Vance, J D; Acott, P E; Kawahara, T D

2009-04-01

With two cw single-mode Nd:YAG lasers at 1064 and 1319 nm and a periodically poled lithium niobate crystal, 11 mW of 2 kHz/100 ms bandwidth single-mode tunable 589 nm cw radiation has been detected using single-pass sum-frequency generation. The demonstrated conversion efficiency is approximately 3.2%[W(-1) cm(-1)]. This compact solid-state light source has been used in a solid-state-dye laser hybrid sodium fluorescence lidar transmitter to measure temperatures and winds in the upper atmosphere (80-105 km); it is being implemented into the transmitter of a mobile all-solid-state sodium temperature and wind lidar under construction.

Detection of carbon monoxide (CO) in sooting hydrocarbon flames using femtosecond two-photon laser-induced fluorescence (fs-TPLIF)

NASA Astrophysics Data System (ADS)

Wang, Yejun; Kulatilaka, Waruna D.

2018-01-01

Ultrashort-pulse, femtosecond (fs)-duration, two-photon laser-induced fluorescence (fs-TPLIF) measurements of carbon monoxide (CO) are reported in rich, sooting hydrocarbon flames. CO-TPLIF detection using conventional nanosecond or picosecond lasers are often plagued by photochemical interferences, specifically under fuel-rich flames conditions. In the current study, we investigate the commonly used CO two-photon excitation scheme of the B1Σ+ ← X1Σ+ electronic transition, using approximately 100-fs-duration excitation pulses. Fluorescence emission was observed in the Ångström band originating from directly populated B1Σ+ upper state, as well as, in the third positive band from collisionally populated b3Σ+ upper state. The current work was focused on the Ångström band emission. Interference from nascent C2 emissions originating from hot soot particles in the flame could be reduced to a negligible level using a narrower detection gate width. In contrast, avoiding interferences from laser-generated C2 Swan-band emissions required specific narrowband spectral filtering in sooting flame conditions. The observed less than quadratic laser pulse energy dependence of the TPLIF signal suggests the presence of strong three-photon ionization and stimulated emission processes. In a range of CH4/air and C2H4/air premixed flames investigated, the measured CO fluorescence signals agree well with the calculated equilibrium CO number densities. Reduced-interference CO-TPLIF imaging in premixed C2H4/O2/N2 jet flames is also reported.

A comparative study of highly-ionized Al plasma based on dual pulse laser-induced breakdown spectroscopy

NASA Astrophysics Data System (ADS)

Khalil, A. A. I.; Younis, W. O.; Gandol, M. A.

2017-03-01

We built a collinear dual-pulse laser-induced breakdown spectroscopy (DP-LIBS) system to study the aluminum (Al) plasma emission by installing a pair of Nd: YAG lasers operating at 266 and 1064 nm. The spectral intensities of selected aluminum doubly-ionized lines were employed to evaluate the optical emission spectra. The influences of the energy ratio of two pulsed lasers on the LIBS intensity for different Al doubly-ionized spectral lines were investigated. The de-excitation rate parameters of the excited ion and the electron impact excitation were computed using the analytical formulas proposed by Smeets and Vriens. The transition probabilities and energy states were computed using Hibbert's configuration interaction, computer package (CIV3). By solving the coupled rate equations including 1 s 22 s 22 p 6n s (2S), 1 s 22 s 22 p 6n p (2P), 1 s 22 s 22 p 6n d (2D) (n = 3-5) and 1 s 22 s 22 p 6n f (2F) (n = 4, 5) states, the level population densities were computed. We also proposed a theoretical population model in order to investigate the effectiveness of the various processes that might affect the population of the upper levels in Al plasma by using the rate coefficients. In addition, the population densities for the 19 upper levels were also computed. Good compatibility between the experimental and the theoretical model data had been observed. Our results might be significant as reference data for the optimization of the DP-LIBS spectrometry and diagnostics of laser produced plasmas.

New, efficient, room temperature mid-infrared laser at 3.9 mu m in holmium:barium yttrium fluoride and visible praseodymium:lithium yttrium fluoride laser for holography

NASA Astrophysics Data System (ADS)

Tabirian, Anna Murazian

This dissertation describes a series of experiments and theoretical studies, which led to the development of two new solid state laser systems: efficient, room temperature mid-infrared solid state laser at 3.9 μm in Ho 3+ doped BaY2F8 and visible Pr:LiYF4 laser at 640 mn for holography. The 3.9 μm laser wavelength matches the peak of mid-IR atmospheric transmission window, which makes it very important for multiple applications such as remote sensing, imaging, IR countermeasures, eye-safe lidars and environmental agent detection. We present the results of spectroscopic evaluations and numerical modeling of energy transfer processes between rare earth ions of Ho3+ doped in two host laser materials: BaY2F8 and LiYF 4. The 3.9 μm laser is based on transition with upper laser lifetime considerably shorter than lower level lifetime, which in general leads to self-terminating laser action in the cw mode or at high repetition rates. Therefore, three different pumping and lasing schemes, that could allow overcoming these limitations have been suggested and studied. First, cascade laser action at 1.4 μm and 3.9 μm was achieved with low thresholds and near-theoretical quantum efficiency in Ho3+ doped BaY2F8 pumped at 532 nm by a Q- switched frequency doubled Nd:YAG laser. Next, the feasibility of achieving 3.9 μm laser with cw resonant cascade pumping at 750 mn by a Ti:Sapphire laser was studied. New energy transfer process, such as upconversion from terminal level of the 3.9 μm laser was observed in high concentration Ho3+ doped BaY2F 8. Finally, we proposed to use high-energy flashlamp pumped tunable Cr:LiSAF laser operating in long pulse regime for the direct pumping of the upper level of the 3.9 μm laser. Pulsed laser oscillation at 3.9 μm is demonstrated in Ho3+ doped BaY2F8 with low threshold of 3 mJ and a slope efficiency of 14.5% with maximal energy of 30 mJ. The second part of the thesis describes the design and the development of the visible Pr:LiYF4 laser for holography at 640 nm resonantly pumped by the frequency-doubled flashlamp pumped tunable Cr:LiSAF laser at 444 nm.

Active media for up-conversion diode-pumped lasers

NASA Astrophysics Data System (ADS)

Tkachuk, Alexandra M.

1996-03-01

In this work, we consider the different methods of populating the initial and final working levels of laser transitions in TR-doped crystals under the selective 'up-conversion' and 'avalanche' diode laser pumping. On the basis of estimates of the probabilities of competing non-radiative energy-transfer processes rates obtained from the experimental data and theoretical calculations, we estimated the efficiency of the up-conversion pumping and selfquenching of the upper TR3+ states excited by laser-diode emission. The effect of the host composition, dopant concentration, and temperature on the output characteristics and up-conversion processes in YLF:Er; BaY2F8:Er; BaY2F8:Er,Yb and BaY2F8:Yb,Ho are determined.

Effect of the focal plane position on CO2 laser beam cutting of injection molded polycarbonate sheets

NASA Astrophysics Data System (ADS)

Moradi, Mahmoud; Mehrabi, Omid; Azdast, Taher; Benyounis, Khaled Y.

2016-11-01

In the present research, the effect of laser beam focal plane position (FPP) on the kerf quality of the polycarbonate laser cutting is investigated. Low power CO2 laser is used as the heat source of the cutting runs. In the experiments, FPP is varied from 0 to -4mm while other processing parameters (i.e. laser power, cutting speed and gas pressure) are considered constant. Upper and lower kerf width, kerf taper, upper heat affected zone and surface roughness of the kerf wall are also considered as the responses. Observations signified that reducing the position of the laser beam focal point from zero to - 3mm reduces the upper and lower kerf width. However reducing FPP below -3mm leads to an increase in the kerf width. Results also reveals that upper heat affected zone value reduces by reduction in FPP. Moreover the best kerf wall surface roughness occurred at FPP= -3mm.

Nonradiative relaxation in tunable solid state laser crystals

NASA Technical Reports Server (NTRS)

Gayen, S. K.; Wang, W. B.; Petricevic, V.; Alfano, R. R.

1986-01-01

The characteristics of nonradiative transitions between the 4T2 and 2E excited states of trivalent-chromium-ion-activated ruby (containing 0.04 percent Cr2O3 by weight) and alexandrite (containing 0.4 at. percent chromium ion) laser crystals were studied using the technique described by Gayen et al. (1985). In this technique, a 527-nm pulse excites the 4T2 band of the Cr(3+), and the subsequent population kinetics among excited states is monitored by an IR picosecond probe pulse as a function of pump-probe delay. In ruby, a resolution-limited sharp rise in the excited state population was followed by a long-lifetime decay, leading to an upper limit of 7 ps for the 4T2-state nonradiative lifetime. In alexandrite, a longer rise time was followed by a multicomponent decay. A theoretical model is proposed for explaining the induced absorption and the transition dynamics observed in these crystals.

Controlling Stimulated Brillouin/Raman Scattering in High Power Fiber Lasers

DTIC Science & Technology

2017-08-09

inversion curve (green)……………….……….40 Figure 22: A schematic of the counter-pumped amplifier is shown above………….…..41 Figure 23: A temporal response of...excites electrons to the upper state, N2, and provides inversion for all other signals. The laser 6 Approved for public release. Distribution is...as is the case below, the Stokes light will have its highest fields present at the z = 0 boundary of the fiber where the highest levels of inversion

Improved efficiency of selective photoionization of palladium isotopes via autoionizing Rydberg states

NASA Astrophysics Data System (ADS)

Locke, Clayton R.; Kobayashi, Tohru; Midorikawa, Katsumi

2017-01-01

Odd-mass-selective ionization of palladium for purposes of resource recycling and management of long-lived fission products can be achieved by exploiting transition selection rules in a well-established three-step excitation process. In this conventional scheme, circularly polarized lasers of the same handedness excite isotopes via two intermediate 2D5/2 core states, and a third laser is then used for ionization via autoionizing Rydberg states. We propose an alternative excitation scheme via intermediate 2D3/2 core states before the autoionizing Rydberg state, improving ionization efficiency by over 130 times. We confirm high selectivity and measure odd-mass isotopes of >99.7(3)% of the total ionized product. We have identified and measured the relative ionization efficiency of the series of Rydberg states that converge to upper ionization limit of the 4 d 9(2D3/2) level, and identify the most efficient excitation is via the Rydberg state at 67668.18(10) cm-1.

Spectral gain profile of a multi-stack terahertz quantum cascade laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bachmann, D., E-mail: dominic.bachmann@tuwien.ac.at; Deutsch, C.; Krall, M.

2014-11-03

The spectral gain of a multi-stack terahertz quantum cascade laser, composed of three active regions with emission frequencies centered at 2.3, 2.7, and 3.0 THz, is studied as a function of driving current and temperature using terahertz time-domain spectroscopy. The optical gain associated with the particular quantum cascade stacks clamps at different driving currents and saturates to different values. We attribute these observations to varying pumping efficiencies of the respective upper laser states and to frequency dependent optical losses. The multi-stack active region exhibits a spectral gain full width at half-maximum of 1.1 THz. Bandwidth and spectral position of themore » measured gain match with the broadband laser emission. As the laser action ceases with increasing operating temperature, the gain at the dominant lasing frequency of 2.65 THz degrades sharply.« less

Optimization of end-pumped, actively Q-switched quasi-III-level lasers.

PubMed

Jabczynski, Jan K; Gorajek, Lukasz; Kwiatkowski, Jacek; Kaskow, Mateusz; Zendzian, Waldemar

2011-08-15

The new model of end-pumped quasi-III-level laser considering transient pumping processes, ground-state-depletion and up-conversion effects was developed. The model consists of two parts: pumping stage and Q-switched part, which can be separated in a case of active Q-switching regime. For pumping stage the semi-analytical model was developed, enabling the calculations for final occupation of upper laser level for given pump power and duration, spatial profile of pump beam, length and dopant level of gain medium. For quasi-stationary inversion, the optimization procedure of Q-switching regime based on Lagrange multiplier technique was developed. The new approach for optimization of CW regime of quasi-three-level lasers was developed to optimize the Q-switched lasers operating with high repetition rates. Both methods of optimizations enable calculation of optimal absorbance of gain medium and output losses for given pump rate. © 2011 Optical Society of America

Quantum cascade laser combs: effects of modulation and dispersion.

PubMed

Villares, Gustavo; Faist, Jérôme

2015-01-26

Frequency comb formation in quantum cascade lasers is studied theoretically using a Maxwell-Bloch formalism based on a modal decomposition, where dispersion is considered. In the mid-infrared, comb formation persists in the presence of weak cavity dispersion (500 fs² mm^-1) but disappears when much larger values are used (30'000 fs² mm^-1). Active modulation at the round-trip frequency is found to induce mode-locking in THz devices, where the upper state lifetime is in the tens of picoseconds. Our results show that mode-locking based on four-wave mixing in broadband gain, low dispersion cavities is the most promising way of achieving broadband quantum cascade laser frequency combs.

New stable tunable solid-state dye laser in the red

NASA Astrophysics Data System (ADS)

Gvishi, Raz; Reisfeld, Renata; Burshtein, Zeev; Miron, Eli

1993-08-01

A red perylene derivative was impregnated into a composite silica-gel glass, and characterized as a dye laser material. The absorption spectrum in the range 480 - 600 nm belongs to the S0 - S1 electronic transition, with a structure reflecting the perylene skeletal vibrations, of typical energy 1100 - 1200 cm-1. An additional peak between 400 and 460 nm belongs to the S0 - S2 transition. The fluorescence exhibits a mirror image relative to the S0 - S1 absorption, with a Stokes shift of about 40 nm for the 0 - 0 transition. Laser tunability was obtained in the range 605 - 630 nm using a frequency-doubled Nd:YAG laser for pumping ((lambda) equals 532 nm). This wavelength range is important for medical applications, such as photodynamic therapy of some cancer tumors. Maximum laser efficiency of approximately 2.5% was obtained at 617 nm. Maximum output was approximately 0.36 mJ/pulse at a repetition rate of 10 Hz. Minimum laser threshold obtained was 0.45 mJ/pulse. The medium losses are attributed to an excited-state singlet-singlet absorption, with an upper limit cross-section of approximately 2.5 X 10-16 cm2. The laser output was stable over more than approximately 500,000 pulses, under excitation with the green line of a copper vapor laser (510 nm), of energy density approximately 40 mJ/cm2 per pulse. Good prospects exist for a considerable enhancement in laser output efficiency.

Enhancement of low power CO2 laser cutting process for injection molded polycarbonate

NASA Astrophysics Data System (ADS)

Moradi, Mahmoud; Mehrabi, Omid; Azdast, Taher; Benyounis, Khaled Y.

2017-11-01

Laser cutting technology is a non-contact process that typically is used for industrial manufacturing applications. Laser cut quality is strongly influenced by the cutting processing parameters. In this research, CO2 laser cutting specifications have been investigated by using design of experiments (DOE) with considering laser cutting speed, laser power and focal plane position as process input parameters and kerf geometry dimensions (i.e. top and bottom kerf width, ratio of the upper kerf to lower kerf, upper heat affected zone (HAZ)) and surface roughness of the kerf wall as process output responses. A 60 Watts CO2 laser cutting machine is used for cutting the injection molded samples of polycarbonate sheet with the thickness of 3.2 mm. Results reveal that by decreasing the laser focal plane position and laser power, the bottom kerf width will be decreased. Also the bottom kerf width decreases by increasing the cutting speed. As a general result, locating the laser spot point in the depth of the workpiece the laser cutting quality increases. Minimum value of the responses (top kerf, heat affected zone, ratio of the upper kerf to lower kerf, and surface roughness) are considered as optimization criteria. Validating the theoretical results using the experimental tests is carried out in order to analyze the results obtained via software.

The near-infrared spectrum of ethynyl radical

DOE Office of Scientific and Technical Information (OSTI.GOV)

Le, Anh T., E-mail: anhle@bnl.gov; Hall, Gregory E., E-mail: gehall@bnl.gov; Sears, Trevor J., E-mail: sears@bnl.gov, E-mail: trevor.sears@stonybrook.edu

2016-08-21

Transient diode laser absorption spectroscopy has been used to measure three strong vibronic bands in the near infrared spectrum of the C{sub 2}H, ethynyl, radical not previously observed in the gas phase. The radical was produced by ultraviolet excimer laser photolysis of either acetylene or (1,1,1)-trifluoropropyne in a slowly flowing sample of the precursor diluted in inert gas, and the spectral resolution was Doppler-limited. The character of the upper states was determined from the rotational and fine structure in the observed spectra and assigned by measurement of ground state rotational combination differences. The upper states include a {sup 2}Σ{sup +}more » state at 6696 cm{sup −1}, a second {sup 2}Σ{sup +} state at 7088 cm{sup −1}, and a {sup 2}Π state at 7110 cm{sup −1}. By comparison with published calculations [R. Tarroni and S. Carter, J. Chem. Phys 119, 12878 (2003); Mol. Phys. 102, 2167 (2004)], the vibronic character of these levels was also assigned. The observed states contain both X{sup 2}Σ{sup +} and A{sup 2}Π electronic characters. Several local rotational level perturbations were observed in the excited states. Kinetic measurements of the time-evolution of the ground state populations following collisional relaxation and reactive loss of the radicals formed in a hot, non-thermal, population distribution were made using some of the strong rotational lines observed. The case of C{sub 2}H may be a good place to investigate the behavior at intermediate pressures of inert colliders, where the competition between relaxation and reaction can be tuned and observed to compare with master equation models, rather than deliberately suppressed to measure thermal rate constants.« less

The near-infrared spectrum of ethynyl radical

DOE PAGES

Le, Anh T.; Hall, Gregory E.; Sears, Trevor J.

2016-08-17

We used transient diode laser absorption spectroscopy to measure three strong vibronic bands in the near infrared spectrum of the C 2H, ethynyl, radical not previously observed in the gas phase. The radical was produced by ultraviolet excimer laser photolysis of either acetylene or (1,1,1)-trifluoropropyne in a slowly flowing sample of the precursor diluted in inert gas, and the spectral resolution was Doppler-limited. The character of the upper states was determined from the rotational and fine structure in the observed spectra and assigned by measurement of ground state rotational combination differences. The upper states include a 2Σ + state atmore » 6696 cm -1, a second 2Σ + state at 7088 cm -1, and a 2Π state at 7110 cm -1. By comparison with published calculations [R. Tarroni and S. Carter, J. Chem. Phys 119, 12878 (2003); Mol. Phys. 102, 2167 (2004)], the vibronic character of these levels was also assigned. Moreover, the observed states contain both X 2Σ + and A 2Π electronic characters. Several local rotational level perturbations were observed in the excited states. Kinetic measurements of the time-evolution of the ground state populations following collisional relaxation and reactive loss of the radicals formed in a hot, non-thermal, population distribution were made using some of the strong rotational lines observed. Finally, the case of C 2H may be a good place to investigate the behavior at intermediate pressures of inert colliders, where the competition between relaxation and reaction can be tuned and observed to compare with master equation models, rather than deliberately suppressed to measure thermal rate constants.« less

Quasi-three level Nd:YLF fundamental and Raman laser operating under 872-nm and 880-nm direct diode pumping

NASA Astrophysics Data System (ADS)

Wetter, Niklaus U.; Bereczki, Allan; Paes, João. Pedro Fonseca

2018-02-01

Nd:YLiF4 is the gain material of choice whenever outstanding beam quality or a birefringent gain material is necessary such as in certain applications for terahertz radiation or dual-frequency mode-locking. However, for high power CW applications the material is hampered by a low thermal fracture threshold. This problem can be mitigated by special 2D pump set-ups or by keeping the quantum defect to a minimum. Direct pumping into the upper laser level of Nd:YLiF4 is usually performed at 880 nm. For quasi-three level laser emission at 908 nm, direct pumping at this wavelength provides a high quantum defect of 0.97, which allows for very high CW pump powers. Although the direct pumping transition to the upper laser state at 872 nm has a slightly smaller quantum defect of 0.96, its pump absorption cross section along the c-axis is 50% higher than at 880 nm, leading to a higher absorption efficiency. In this work we explore, for the first time to our knowledge, 908 nm lasing under 872 nm diode pumping and compare the results with 880 nm pumping for quasicw and cw operation. By inserting a KGW crystal in the cavity, Raman lines at 990 nm and 972 nm were obtained for the first time from a directly pumped 908 nm Nd:YLF fundamental laser for both quasi-cw and cw conditions.

Laser vocal cordectomy fails to effectively reduce respiratory noise in horses with laryngeal hemiplegia.

PubMed

Brown, Jennifer A; Derksen, Frederik J; Stick, John A; Hartmann, William M; Robinson, N Edward

2005-01-01

To report the effect of unilateral laser vocal cordectomy on respiratory noise and airway function in horses with experimentally induced laryngeal hemiplegia (LH). Experimental study. Six Standardbred horses without upper airway abnormalities at rest or during high-speed treadmill exercise. Respiratory sounds and inspiratory trans-upper airway pressure (P(Ui)) were measured before (baseline) and 14 days after induction of LH by left recurrent laryngeal neurectomy, and again 30, 60, 90, and 120 days after endoscopically assisted laser cordectomy of the left vocal cord. Data were collected with the horses exercising on a treadmill at a speed producing maximum heart rate (HR(max)). In horses exercising at HR(max), induction of LH caused a significant increase in P(Ui), sound level (SL), and the sound intensity of formant 2 (F(2)) and 3 (F(3)). The sound intensity of formant 1 (F(1)) was unaffected by induction of LH. Laser vocal cordectomy had no effect on SL, or on the sound intensity of F(1) and F(3). At 30, 60, 90, and 120 days after surgery, P(Ui) and the sound intensity of F(2) were significantly reduced, but these variables remained significantly different from baseline values. Unilateral laser vocal cordectomy did not effectively improve upper airway noise in horses with LH. The procedure decreased upper airway obstruction to the same degree as bilateral ventriculocordectomy. Currently, laser vocal cordectomy cannot be recommended for the treatment of upper airway noise in horses with LH.

Semiconductor laser devices having lateral refractive index tailoring

DOEpatents

Ashby, Carol I. H.; Hadley, G. Ronald; Hohimer, John P.; Owyoung, Adelbert

1990-01-01

A broad-area semiconductor laser diode includes an active lasing region interposed between an upper and a lower cladding layer, the laser diode further comprising structure for controllably varying a lateral refractive index profile of the diode to substantially compensate for an effect of junction heating during operation. In embodiments disclosed the controlling structure comprises resistive heating strips or non-radiative linear junctions disposed parallel to the active region. Another embodiment discloses a multi-layered upper cladding region selectively disordered by implanted or diffused dopant impurities. Still another embodiment discloses an upper cladding layer of variable thickness that is convex in shape and symmetrically disposed about a central axis of the active region. The teaching of the invention is also shown to be applicable to arrays of semiconductor laser diodes.

Design strategy for terahertz quantum dot cascade lasers.

PubMed

Burnett, Benjamin A; Williams, Benjamin S

2016-10-31

The development of quantum dot cascade lasers has been proposed as a path to obtain terahertz semiconductor lasers that operate at room temperature. The expected benefit is due to the suppression of nonradiative electron-phonon scattering and reduced dephasing that accompanies discretization of the electronic energy spectrum. We present numerical modeling which predicts that simple scaling of conventional quantum well based designs to the quantum dot regime will likely fail due to electrical instability associated with high-field domain formation. A design strategy adapted for terahertz quantum dot cascade lasers is presented which avoids these problems. Counterintuitively, this involves the resonant depopulation of the laser's upper state with the LO-phonon energy. The strategy is tested theoretically using a density matrix model of transport and gain, which predicts sufficient gain for lasing at stable operating points. Finally, the effect of quantum dot size inhomogeneity on the optical lineshape is explored, suggesting that the design concept is robust to a moderate amount of statistical variation.

The behavior of gain and saturation characteristics versus temperature in a copper bromide laser

NASA Astrophysics Data System (ADS)

Mohammadpour Lima, S.; Behrouzinia, S.; Salem, M. K.; Elahei, M.; Khorasani, K.; Dorranian, D.

2017-05-01

A pair of copper bromide lasers in an oscillator-amplifier configuration was used to investigate the temperature dependence of the small-signal gain, saturation intensity, and output power of the laser. The observations were explained in terms of the electron temperature and energy levels of transition. An optimum electrical input power of 1.6 kW and a corresponding operational temperature of 510 °C were determined for the maximum values of these parameters. The balance between the microscopic parameters, such as stimulated emission cross-section, laser upper-level lifetime, and population inversion, which determine the behavior of the amplifying parameters and laser output power with respect to the operational temperature, has been investigated. We used the steady-state rate equation from the Hargrove model to determine the amplifying parameters, instead of the Frantz-Nodvik formula. The power extracted from the amplifier exceeds that achieved with the same device as the oscillator by more than 60%.

Resonant-phonon-assisted THz quantum cascade lasers with metal-metal waveguides.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Callebaut, Hans; Kohen, Stephen; Kumar, Sushil

2004-06-01

We report our development of terahertz (THz) quantum-cascade lasers (QCLs) based on two novel features. First, the depopulation of the lower radiative level is achieved through resonant longitudinal optical (LO-)phonon scattering. This depopulation mechanism is robust at high temperatures and high injection levels. In contrast to infrared QCLs that also use LO-phonon scattering for depopulation, in our THz lasers the selectivity of the depopulation scattering is achieved through a combination of resonant tunneling and LO-phonon scattering, hence the term resonant phonon. This resonant-phonon scheme allows a highly selective depopulation of the lower radiative level with a sub-picosecond lifetime, while maintainingmore » a relatively long upper level lifetime (>5 ps) that is due to upper-to-ground-state scattering. The second feature of our lasers is that mode confinement is achieved by using a novel double-sided metal-metal waveguide, which yields an essentially unity mode confinement factor and therefore a low total cavity loss at THz frequencies. Based on these two unique features, we have achieved some record performance, including, but not limited to, the highest pulsed operating temperature of 137 K, the highest continuous-wave operating temperature of 97 K, and the longest wavelength of 141 {micro}m (corresponding to 2.1 THz) without the assistance of a magnetic field.« less

Development of a diode laser heterodyne spectrometer and observations of silicon monoxide in sunspots. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Glenar, D. A.

1981-01-01

A state of the art, tunable diode laser infrared heterodyne spectrometer was designed and constructed for ground based observations throughout the 8 to 12 micron atmospheric window. The instrument was optimized for use with presently available tunable diode lasers, and was designed as a flexible field system for use with large reflecting telescopes. The instrument was aligned and calibrated using laboratory and astronomical sources. Observations of SiO fundamental (v = 1-0) and hot band (v = 2-1) absorption features were made in sunspots near 8 microns using the spectrometer. The data permit an unambiguous determination of the temperature pressure relation in the upper layers of the umbral atmosphere, and support the sunspot model suggested by Stellmacher and Wiehr.

High-Resolution Study of the Perturbation in the CO Triplet Band

NASA Astrophysics Data System (ADS)

Momona, M.; Kanamori, H.; Sakurai, K.

1993-05-01

Seven hundred absorption lines have been observed in the discharge plasma of He and CO in the 12600-12 800 cm-1 region with Doppler-limited resolution by a near-infrared diode laser spectrometer. Out of complex spectral patterns, more than 400 lines were assigned to the CO triplet band, d3Δ(v‧ = 2) - a3Π (v″ = 1). The upper state of this transition is known to be severely perturbed. The measurement of all the spin subbands of the 3Δ - 3Π transition allowed us to reanalyze the perturbation of the d3Δ (v = 2) state with the highly vibrationally excited state, v = 9, in the a3Π state. Diode laser spectroscopy with high sensitivity and Doppler-limited resolution revealed the overtone band transition from v = 1 to v = 9 within the a3Π state and the Λ-type doubling in the d3Δ state. Those interesting phenomena can be understood as a result of the perturbation and were successfully reproduced by the eigenvectors determined in this analysis.

Is energy pooling necessary in ultraviolet matrix-assisted laser desorption/ionization?

PubMed

Lin, Hou-Yu; Song, Botao; Lu, I-Chung; Hsu, Kuo-Tung; Liao, Chih-Yu; Lee, Yin-Yu; Tseng, Chien-Ming; Lee, Yuan-Tseh; Ni, Chi-Kung

2014-01-15

Energy pooling has been suggested as the key process for generating the primary ions during ultraviolet matrix-assisted laser desorption/ionization (UV-MALDI). In previous studies, decreases in fluorescence quantum yields as laser fluence increased for 2-aminobenzoic acid, 2,5-dihydroxybenzoic acid (2,5-DHB), and 3-hydroxypicolinic acid were used as evidence of energy pooling. This work extends the research to other matrices and addresses whether energy pooling is a universal property in UV-MALDI. Energy pooling was investigated in a time-resolved fluorescence experiment by using a short laser pulse (355 nm, 20 ps pulse width) for excitation and a streak camera (1 ps time resolution) for fluorescence detection. The excited-state lifetime of 2,5-DHB decreased with increases in laser fluence. This suggests that a reaction occurs between two excited molecules, and that energy pooling may be one of the possible reactions. However, the excited-state lifetime of 2,4,6-trihydroxyacetophenone (THAP) did not change with increases in laser fluence. The upper limit of the energy pooling rate constant for THAP is estimated to be approximately 100-500 times smaller than that of 2,5-DHB. The small energy pooling rate constant for THAP indicates that the potential contribution of the energy pooling mechanism to the generation of THAP matrix primary ions should be reconsidered. Copyright © 2013 John Wiley & Sons, Ltd.

Evaluation of uranium transitions for isotopically-selective laser induced fluorescence with diode lasers (technical report for ST064)

NASA Astrophysics Data System (ADS)

Cannon, B. D.

1993-10-01

Isotopically-selective excitation of uranium atoms by diode lasers can be the basis for a portable instrument to perform uranium isotopic assays in the field. Such an instrument would improve the ability of on-site inspections to detect and deter nuclear proliferation. Published and unpublished spectroscopic data on atomic uranium were examined to identify candidate transitions for isotopically-selective laser excitation with diode lasers. Eleven candidate transitions were identified and evaluated for their potential usefulness for a portable uranium assay instrument. Eight of these transitions are suitable for laser induced fluorescence using different excitation and detection wavelengths, which will improve sensitivity and elemental selectivity. Data sheets on the 25 uranium transitions in the wavelength range 629 nm to 1,000 nm that originate in the ground or first excited states of neutral atomic uranium are included. Each data sheet provides the wavelength, upper and lower energy levels, angular momentum quantum numbers, U-235 isotope shift (relative to U-238, and high-resolution spectra of weapons-grade uranium (93% U-235 and 7% U-238).

Laser induced fluorescence and phosphorescence of matrix isolated glyoxal - Evidence for exciplex formation in the A 1Au and a 3Au states

NASA Technical Reports Server (NTRS)

Van Ijzendoorn, L. J.; Baas, F.; Koernig, S.; Greenberg, J. M.; Allamandola, L. J.

1986-01-01

Laser-induced fluorescence and phosphorescence as well as infrared and visible absorption spectra of glyoxal in Ar, N2, and CO matrices are presented and analyzed. Glyoxal in its first excited electronic state is shown to form an exciplex with its nearest neighbors in all three matrices, and transitions normally forbidden dominate the emission spectra. The spectral characteristics of these complexes are similar to those of the Ar-glyoxal complex found in supersonic beam experiments. Due to the matrix cage effect, no vibrational predissociation is observed. The phosphorescence lifetime is determined and an upper limit is given for the fluorescence lifetime. This, in combination with the relative intensities of fluorescence and phosphorescence, can be used to place limits on the quantum yields of the various relaxation processes.

A 1.3-μm four-channel directly modulated laser array fabricated by SAG-Upper-SCH technology

NASA Astrophysics Data System (ADS)

Guo, Fei; Lu, Dan; Zhang, Ruikang; Liu, Songtao; Sun, Mengdie; Kan, Qiang; Ji, Chen

2017-01-01

A monolithically integrated four-channel directly modulated laser (DML) array working at the 1.3-μm band is demonstrated. The laser was manufactured by using the techniques of selective area growth (SAG) of the upper separate confinement heterostructure (Upper-SCH) and modified butt-joint method. The fabricated device showed stable single mode operation with the side mode suppression ratio (SMSR) >35 dB, and high wavelength accuracy with the deviations from the linear fitted values <±0.03 nm for all channels. Furthermore, small signal modulation bandwidth >7 GHz was obtained, which may be suitable for 40 GbE applications in the 1.3-μm band.

A practical model of thin disk regenerative amplifier based on analytical expression of ASE lifetime

NASA Astrophysics Data System (ADS)

Zhou, Huang; Chyla, Michal; Nagisetty, Siva Sankar; Chen, Liyuan; Endo, Akira; Smrz, Martin; Mocek, Tomas

2017-12-01

In this paper, a practical model of a thin disk regenerative amplifier has been developed based on an analytical approach, in which Drew A. Copeland [1] had evaluated the loss rate of the upper state laser level due to ASE and derived the analytical expression of the effective life-time of the upper-state laser level by taking the Lorentzian stimulated emission line-shape and total internal reflection into account. By adopting the analytical expression of effective life-time in the rate equations, we have developed a less numerically intensive model for predicting and analyzing the performance of a thin disk regenerative amplifier. Thanks to the model, optimized combination of various parameters can be obtained to avoid saturation, period-doubling bifurcation or first pulse suppression prior to experiments. The effective life-time due to ASE is also analyzed against various parameters. The simulated results fit well with experimental data. By fitting more experimental results with numerical model, we can improve the parameters of the model, such as reflective factor which is used to determine the weight of boundary reflection within the influence of ASE. This practical model will be used to explore the scaling limits imposed by ASE of the thin disk regenerative amplifier being developed in HiLASE Centre.

Experience of curing serious obstruction of advanced-stage upper digestive tract tumor using laser under endoscope

NASA Astrophysics Data System (ADS)

Mu, Hai-Bin; Zhang, Man-Ling; Zhang, Xiao-Qiang; Zhang, Feng-Qiu; Kong, De-Jia; Tang, Li-Bin

1998-11-01

The patients who suffer from upper digestive tract tumor, such as cancer of esophagus, cancer of cardia, all have serious obstruction and fail to get nutrition and can not bear the strike of the radiotherapy and chemotherapy. In order to reduce the obstruction symptom and suffering of the patients and to prolong their life time, since 1989, our hospital used the laser to cure the upper digestive tract tumor 11 cases with serious obstruction and got remarkable curative effect.

Energy transfer and up-conversion in rare-earth doped dielectric crystals

NASA Astrophysics Data System (ADS)

Tkachuk, Alexandra M.

1996-01-01

In this work, we consider the prospects of development of the visible, and IR laser-diode pumped lasers based on TR3+-doped double-fluoride crystals. On the basis of estimates of the probabilities of competing non-radiative energy-transfer processes obtained from the experiments and theoretical calculations, the conclusions are drawn on the efficiency of up-conversion pumping and selfquenching of the upper TR3+ states excited by laser-diode emission. The effect of the host composition, dopant concentration, and temperature on the efficiency of up-conversion processes is demonstrated on the example of the YLF:Nd, YLF:Er, BaY2F8:Er, and BaY2F8:Er,Yb crystals. The transfer microparameters for most important cross-relaxation transitions are determined and the conclusions about interaction mechanisms are drawn.

Laser-Induced Fluorescence Measurements of Translational Temperature and Relative Cycle Number by use of Optically Pumped Trace-Sodium Vapor

NASA Technical Reports Server (NTRS)

Dobson, Chris C.

1998-01-01

Sodium fluorescence induced by a narrow bandwidth tunable laser has been used to measure temperature, pressure, axial velocity and species concentrations in wind tunnels, rocket engine exhausts and the upper atmosphere. Optical pumping of the ground states of the sodium, however, can radically alter the shape of the laser induced fluorescence excitation spectrum, complicating such measurements. Here a straightforward extension of rate equations originally proposed to account for the features of the pumped spectrum is to make temperature measurements from spectra taken in pumped vapor. Also determined from the spectrum is the relative fluorescence cycle number, which has application to measurement of diffusion rate and transverse flow velocity. The accuracy of both the temperature and cycle-number measurements is comparable with that of temperature measurements made in the absence of pumping.

Ultraviolet laser spectroscopy of jet-cooled CaNC and SrNC free radicals: Observation of bent excited electronic states

NASA Astrophysics Data System (ADS)

Greetham, Gregory M.; Ellis, Andrew M.

2000-11-01

New electronic transitions of the CaNC and SrNC free radicals have been identified in the near ultraviolet. For CaNC one new system, labeled the D˜-X˜ transition, was observed in the 31 500-33 400 cm-1 region. Two new transitions were found for SrNC, the D˜-X˜ and Ẽ-X˜ systems spanning 29 100-31 000 and 32 750-34 000 cm-1, respectively. Jet-cooled laser excitation spectra yield complex vibrational structure, much of which is attributed to excitation of the bending vibration. This has been used to infer that the molecule adopts a nonlinear equilibrium geometry in the upper electronic state in all three band systems, in contrast to the linear ground electronic state. This structural change is accounted for by the increased diffuseness of the unpaired electron in the excited states, which favors deviation from linearity. All three new excited states are assigned 2A' symmetry and correlate with 2Σ+ states in the linear molecule limit. Tentative estimates for the barriers to linearity in the D˜ 2A' states of CaNC and SrNC have been determined as ˜700 and ˜1050 cm-1, respectively.

Theoretical studies of solar-pumped lasers

NASA Astrophysics Data System (ADS)

Harries, Wynford L.

1988-06-01

The investigation of stimulated emission causing transitions from the B(1) pi sub u state of sodium to the overlapping 2(1) sigma(+) sub g electronic state has been continued. A new method of estimating the Franck-Condon factors has been developed which instead of fitting the molecular potential curves with Morse functions, estimates the V(r) dependence by interpolation from given potential curves. The results for the sum of the rates from one vibrational level in the upper state to all the levels in the lower state show good agreement with the previous method, implying that curve crossing by stimulated emission due to photons from the oven is an important mechanism in sodium.

Enhanced vbasis laser diode package

DOEpatents

Deri, Robert J.; Chen, Diana; Bayramian, Andy; Freitas, Barry; Kotovsky, Jack

2014-08-19

A substrate having an upper surface and a lower surface is provided. The substrate includes a plurality of v-grooves formed in the upper surface. Each v-groove includes a first side and a second side perpendicular to the first side. A laser diode bar assembly is disposed within each of the v-grooves and attached to the first side. The laser diode bar assembly includes a first adhesion layer disposed on the first side of the v-groove, a metal plate attached to the first adhesion layer, a second adhesion layer disposed over the metal plate, and a laser diode bar attached to the second adhesion layer. The laser diode bar has a coefficient of thermal expansion (CTE) substantially similar to that of the metal plate.

Gain and energy storage in holmium YLF

NASA Technical Reports Server (NTRS)

Storm, Mark E.; Deyst, John P.

1991-01-01

It is demonstrated that Q-switched holmium lasers are capable of high-gain and high-energy operation at 300 K. Small-signal gain coefficients of 0.50 and 0.12/cm have been measured in YLF and YAG, respectively. Small-signal gains of 0.50/cm are comparable to those achievable in Nd:YAG and are not typical of low-gain materials. This large gain in the Ho:YLF material is made possible by operating the amplifier in the ground state depletion mode. The amplifier performance data and associated analysis presented demonstrate that efficient energy storage is possible with very high excited state ion densities of the Ho 5I7 upper laser level. This is an important result since upconversion can limit the 5I7 population. Although upconversion was still present in this experiment, it was possible to achieve efficient energy storage, demonstrating that the problem is manageable even at high excitation densities in YLF.

A High Resolution Spectroscopic Study of the Nu2 Band of Hydrogen Sulfide and the 1-0 Band of Hydrogen Iodide. Ph.D. Thesis - Maryland Univ.

NASA Technical Reports Server (NTRS)

Strow, L. L.

1981-01-01

A tunable diode laser spectrometer was constructed and used to study: (1) the effects of centrifugal distortion on the transition frequencies and strengths of the nu sub 2 band of H2S, and (2) nuclear quadrupole hyperfine structure in the 1-0 band of HI. A total of 126 line frequencies and 94 line strengths in the nu sub 2 band of H2S were measured. The average accuracy of the line frequency measurements was + or - 0.0016 cm. The line strengths were measured to an average accuracy of about 3 percent. The effect of the finite spectral width of the diode laser on the measurement of line strengths is discussed. The observed H2S line frequencies were fit to Watson's AS and NS reduced Hamiltonian in both the Ir and IIIr coordinate representations in order to determine the best set of rotation distortion constants for the upper state of the nu sub 2 band. Comparisons of the observed line strengths in this band to rigid rotor line strengths are also presented. Nuclear quadrupole hyperfine structure in the low J lines of the 1-0 band of HI was observed. The upper vibrational state nuclear quadrupole coupling constant, determined from the observed splittings, was -1850 MHz + or - 12 MHz or 1.2 percent + or - 0.7 percent larger than the ground state coupling constant.

III-V semiconductor Quantum Well systems: Physics of Gallium Arsenide two-dimensional hole systems and engineering of mid-infrared Quantum Cascade lasers

NASA Astrophysics Data System (ADS)

Chiu, YenTing

This dissertation examines two types of III-V semiconductor quantum well systems: two-dimensional holes in GaAs, and mid-infrared Quantum Cascade lasers. GaAs holes have a much reduced hyperfine interaction with the nuclei due to the p-like orbital, resulting in a longer hole spin coherence time comparing to the electron spin coherence time. Therefore, holes' spins are promising candidates for quantum computing qubits, but the effective mass and the Lande g-factor, whose product determines the spin-susceptibility of holes, are not well known. In this thesis, we measure the effective hole mass through analyzing the temperature dependence of Shubnikov-de Haas oscillations in a relatively strong interacting two-dimensional hole systems confined to a 20 nm-wide, (311)A GaAs quantum well. The holes in this system occupy two nearly-degenerate spin subbands whose effective mass we measure to be ˜ 0.2 me. We then apply a sufficiently strong parallel magnetic field to fully depopulate one of the spin subbands, and the spin susceptibility of the two-dimensional hole system is deduced from the depopulation field. We also confine holes in closely spaced bilayer GaAs quantum wells to study the interlayer tunneling spectrum as a function of interlayer bias and in-plane magnetic field, in hope of probing the hole's Fermi contour. Quantum Cascade lasers are one of the major mid-infrared light sources well suited for applications in health and environmental sensing. One of the important factors that affect Quantum Cascade laser performance is the quality of the interfaces between the epitaxial layers. What has long been neglected is that interface roughness causes intersubband scattering, and thus affecting the relation between the lifetimes of the upper and lower laser states, which determines if population inversion is possible. We first utilize strategically added interface roughness in the laser design to engineer the intersubband scattering lifetimes. We further experimentally prove the importance of interface roughness on intersubband scattering by measuring the electron transit time of different quantum cascade lasers and comparing them to the calculated upper laser level lifetimes with and without taking into account interface roughness induced intersubband scattering. A significantly better correlation is found between the experimental results and the calculation when the interface roughness scattering is included. Lastly, we study the effect of growth asymmetry on scattering mechanisms in mid-infrared Quantum Cascade lasers. Due to the dopant migration of around 10 nm along the growth direction of InGaAs/InAlAs Quantum Cascade laser structures, ionized impurity scattering is found to have a non-negligible influence on the lifetime of the upper laser level when the laser is biased in the polarity that electrons flow along the growth direction, in sharp contrast to the situation for the opposite polarity.

Testing of Selective Laser Melting Turbomachinery Applicable to Exploration Upper Stage

NASA Technical Reports Server (NTRS)

Calvert, Marty; Turpin, Jason; Nettles, Mindy

2015-01-01

This task is to design, fabricate, and spin test to failure a Ti6-4 hydrogen turbopump impeller that was built using the selective laser melting (SLM) fabrication process (fig. 1). The impeller is sized around upper stage engine requirements. In addition to the spin burst test, material testing will be performed on coupons that are built with the impeller.

Terahertz quantum cascade lasers based on resonant phonon scattering for depopulation.

PubMed

Hu, Qing; Williams, Benjamin S; Kumar, Sushil; Callebaut, Hans; Reno, John L

2004-02-15

We report our development of terahertz (THz) quantum cascade lasers (QCLs), in which the depopulation of the lower radiative level is achieved through resonant longitudinal optical (LO) phonon scattering. This depopulation mechanism, similar to that implemented in all the QCLs operating at mid-infrared frequencies, is robust at high temperatures and high injection levels. The unique feature of resonant LO-phonon scattering in our THz QCL structures allows a highly selective depopulation of the lower radiative level with a sub-picosecond lifetime, while maintaining a relatively long upper level lifetime (more than 5 ps) that is due to upper-to-ground-state scattering. The first QCL based on this mechanism achieved lasing at 3.4 THz (lambda approximately 87 microm) up to 87 K for pulsed operations, with peak power levels exceeding 10 mW at ca. 40 K. Using a novel double-sided metal waveguide for mode confinement, which yields a unity mode confinement factor and therefore a low total cavity loss at THz frequencies, we have also achieved lasing at wavelengths longer than 100 microm.

Laser-Induced Fluorescence Measurements of Translational Temperature and Relative Cycle Number by use of Optically Pumped Trace-Sodium Vapor

NASA Technical Reports Server (NTRS)

Dobson, Chris C.

1999-01-01

Sodium fluorescence induced by a narrow-bandwidth tunable laser has been used to measure temperature, pressure, axial velocity, and species concentrations in wind tunnels, rocket engine exhausts, and the upper atmosphere. Optical pumping of the ground states of the sodium, however, can radically alter the shape of the laser-induced fluorescence excitation spectrum, complicating such measurements. Here a straightforward extension of rate equations originally proposed to account for the features of the pumped spectrum is used to make temperature measurements from spectra taken in pumped vapor. Also determined from the spectrum is the relative fluorescence cycle number, which has application to measurement of diffusion rate and transverse flow velocity, The accuracy of both the temperature and the cycle-number measurements is comparable with that of temperature measurements made in the absence of pumping.

Laser induced fluorescence in Ar and He plasmas with a tunable diode laser

NASA Astrophysics Data System (ADS)

Boivin, R. F.; Scime, E. E.

2003-10-01

A diode laser based laser induced fluorescence (LIF) diagnostic that uses an inexpensive diode laser system is described. This LIF diagnostic has been developed on the hot helicon experiment (HELIX) plasma device. The same diode laser is used to alternatively pump Ar II and He I transitions to obtain argon ion and atomic helium temperatures, respectively. The 1.5 MHz bandwidth diode laser has a Littrow external cavity with a mode-hop free tuning range up to 14 GHz (≈0.021 nm) and a total power output of about 12 mW. Wavelength scanning is achieved by varying the voltage on a piezoelectric controlled grating located within the laser cavity. The fluorescence radiation is monitored with a photomultiplier detector. A narrow band interference filter is used to eliminate all but the plasma radiation in the immediate vicinity of the fluorescence wavelength. Lock-in amplification is used to isolate the fluorescence signal from noise and electron-impact induced radiation. For the Ar ion, the laser tuned at 668.43 nm is used to pump the 3d 4F7/2 Ar II metastable level to the 4p 4D5/2 level. The 442.60 nm fluorescence radiation between the 4p 4D5/2 and the 4s 4P3/2 levels is captured by the photomultiplier tube. For atomic He, the laser is tuned at 667.82 nm to pump a fraction of the electron population from the 21P state to the 31D upper level. Although the 21P level is not a metastable, the close proximity of 21S metastable makes this new He I LIF scheme possible. In this scheme, a fraction of the laser-excited electrons undergo collisional excitation transfer from the 31D to the 31P level. In turn, the 31P state decays to the metastable 21S by emitting 501.57 nm fluorescence photons.

Analysis of laser remote fusion cutting based on a mathematical model

NASA Astrophysics Data System (ADS)

Matti, R. S.; Ilar, T.; Kaplan, A. F. H.

2013-12-01

Laser remote fusion cutting is analyzed by the aid of a semi-analytical mathematical model of the processing front. By local calculation of the energy balance between the absorbed laser beam and the heat losses, the three-dimensional vaporization front can be calculated. Based on an empirical model for the melt flow field, from a mass balance, the melt film and the melting front can be derived, however only in a simplified manner and for quasi-steady state conditions. Front waviness and multiple reflections are not modelled. The model enables to compare the similarities, differences, and limits between laser remote fusion cutting, laser remote ablation cutting, and even laser keyhole welding. In contrast to the upper part of the vaporization front, the major part only slightly varies with respect to heat flux, laser power density, absorptivity, and angle of front inclination. Statistical analysis shows that for high cutting speed, the domains of high laser power density contribute much more to the formation of the front than for low speed. The semi-analytical modelling approach offers flexibility to simplify part of the process physics while, for example, sophisticated modelling of the complex focused fibre-guided laser beam is taken into account to enable deeper analysis of the beam interaction. Mechanisms like recast layer generation, absorptivity at a wavy processing front, and melt film formation are studied too.

Predissociation of tif by tunneling

NASA Astrophysics Data System (ADS)

Wolf, U.; Tiemann, E.

1987-01-01

The UV spectra of the B 3Π 1-X 1Σ + transition in TIF were recorded applying frequency-doubled laser radiation and fluorescence or direct absorption detection. The observed J' -dependent predissociation in the upper levels v' = 2 and v' = 3 is explained quantitatively by invoking tunneling through a potential hump. The line positions and widths are fitted to a potential curve of the B 3Π 1 state using the semiclassical approximation for bound and quasibound levels.

186 K Operation of Terahertz Quantum-Cascade Lasers Based on a Diagonal Design

NASA Technical Reports Server (NTRS)

Kumar, Sushil; Hu, Qing; Reno, John L.

2009-01-01

Resonant-phonon terahertz quantum-cascade lasers operating up to a heat-sink temperature of 186 K are demonstrated. This record temperature performance is achieved based on a diagonal design, with the objective to increase the upper-state lifetime and therefore the gain at elevated temperatures. The increased diagonality also lowers the operating current densities by limiting the flow of parasitic leakage current. Quantitatively, the diagonality is characterized by a radiative oscillator strength that is smaller by a factor of two from the least of any previously published designs. At the lasing frequency of 3.9 THz, 63 mW of peak optical power was measured at 5 K, and approximately 5 mW could still be detected at 180 K.

Collisional Removal of OH (X (sup 2)Pi, nu=7) by O2, N2, CO2, and N2O

NASA Technical Reports Server (NTRS)

Knutsen, Karen; Dyer, Mark J.; Copeland, Richard A.

1996-01-01

Collisional removal rate constants for the OH (X 2PI, nu = 7) radical are measured for the colliders O2, CO2, and N2O, and an upper limit is established for N2. OH(nu = 4) molecules, generated in a microwave discharge flow cell by the reaction of hydrogen atoms with ozone, are excited to v = 7 by the output of a pulsed infrared laser via direct vibrational overtone excitation. The temporal evolution of the P = 7 population is probed as a function of the collider gas partial pressure by a time-delayed pulsed ultraviolet laser. Fluorescence from the B 21 + state is detected in the visible spectral region.

Picosecond excite-and-probe absorption measurement of the intra-2E(g)E(3/2)-state vibrational relaxation time in Ti(3+):Al2O3

NASA Technical Reports Server (NTRS)

Gayen, S. K.; Wang, W. B.; Petricevic, V.; Yoo, K. M.; Alfano, R. R.

1987-01-01

The Ti(3+)-doped Al2O3 has been recently demonstrated to be a tunable solid-state laser system with Ti(3+) as the laser-active ion. In this paper, the kinetics of vibrational transitions in the 2E(g)E(3/2) electronic state of Ti(3+):Al2O3a (crucial for characterizing new host materials for the Ti ion) was investigated. A 527-nm 5-ps pulse was used to excite a band of higher vibrational levels of the 2E(g)E(3/2) state, and the subsequent growth of population in the zero vibrational level and lower vibrational levels was monitored by a 3.9-micron picosecond probe pulse. The time evolution curve in the excited 2E(g)E(3/2) state at room temperature was found to be characterized by a sharp rise followed by a long decay, the long lifetime decay reflecting the depopulation of the zero and the lower vibrational levels of the 2E(g)E(3/2) state via radiative transitions. An upper limit of 3.5 ps was estimated for intra-2E(g)E(3/2)-state vibrational relaxation time.

Commercial mode-locked vertical external cavity surface emitting lasers

NASA Astrophysics Data System (ADS)

Lubeigt, Walter; Bialkowski, Bartlomiej; Lin, Jipeng; Head, C. Robin; Hempler, Nils; Maker, Gareth T.; Malcolm, Graeme P. A.

2017-02-01

In recent years, M Squared Lasers have successfully commercialized a range of mode-locked vertical external cavity surface emitting lasers (VECSELs) operating between 920-1050nm and producing picosecond-range pulses with average powers above 1W at pulse repetition frequencies (PRF) of 200MHz. These laser products offer a low-cost, easy-to-use and maintenance-free tool for the growing market of nonlinear microscopy. However, in order to present a credible alternative to ultrafast Ti-sapphire lasers, pulse durations below 200fs are required. In the last year, efforts have been directed to reduce the pulse duration of the Dragonfly laser system to below 200fs with a target average power above 1W at a PRF of 200MHz. This paper will describe and discuss the latest efforts undertaken to approach these targets in a laser system operating at 990nm. The relatively low PRF operation of Dragonfly lasers represents a challenging requirement for mode-locked VECSELs due to the very short upper state carrier lifetime, on the order of a few nanoseconds, which can lead to double pulsing behavior in longer cavities as the time between consecutive pulses is increased. Most notably, the design of the Dragonfly VECSEL cavity was considerably modified and the laser system extended with a nonlinear pulse stretcher and an additional compression stage. The improved Dragonfly laser system achieved pulse duration as short as 130fs with an average power of 0.85W.

Analysis of laser remote fusion cutting based on a mathematical model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matti, R. S.; Department of Mechanical Engineering, College of Engineering, University of Mosul, Mosul; Ilar, T.

Laser remote fusion cutting is analyzed by the aid of a semi-analytical mathematical model of the processing front. By local calculation of the energy balance between the absorbed laser beam and the heat losses, the three-dimensional vaporization front can be calculated. Based on an empirical model for the melt flow field, from a mass balance, the melt film and the melting front can be derived, however only in a simplified manner and for quasi-steady state conditions. Front waviness and multiple reflections are not modelled. The model enables to compare the similarities, differences, and limits between laser remote fusion cutting, lasermore » remote ablation cutting, and even laser keyhole welding. In contrast to the upper part of the vaporization front, the major part only slightly varies with respect to heat flux, laser power density, absorptivity, and angle of front inclination. Statistical analysis shows that for high cutting speed, the domains of high laser power density contribute much more to the formation of the front than for low speed. The semi-analytical modelling approach offers flexibility to simplify part of the process physics while, for example, sophisticated modelling of the complex focused fibre-guided laser beam is taken into account to enable deeper analysis of the beam interaction. Mechanisms like recast layer generation, absorptivity at a wavy processing front, and melt film formation are studied too.« less

Explanation of the cw operation of the Er3+ 3-μm crystal laser

NASA Astrophysics Data System (ADS)

Pollnau, M.; Graf, Th.; Balmer, J. E.; Lüthy, W.; Weber, H. P.

1994-05-01

A computer simulation of the Er3+ 3-μm crystal laser considering the full rate-equation scheme up to the 4F7/2 level has been performed. The influence of the important system parameters on lasing and the interaction of these parameters has been clarified with multiple-parameter variations. Stimulated emission is fed mainly by up-conversion from the lower laser level and in many cases is reduced by the quenching of the lifetime of this level. However, also without up-conversion a set of parameters can be found that allows lasing. Up-conversion from the upper laser level is detrimental to stimulated emission but may be compensated by cross relaxation from the 4S3/2 level. For a typical experimental situation we started with the parameters of Er3+:LiYF4. In addition, the host materials Y3Al5O12 (YAG), YAlO3, Y3Sc2Al3O12 (YSGG), and BaY2F8, as well as the possibilities of codoping, are discussed. In view of the consideration of all excited levels up to 4F7/2, all lifetimes and branching ratios, ground-state depletion, excited-state absorption, three up-conversion processes as well as their inverse processes, stimulated emission, and a realistic resonator design, this is, to our knowledge, the most detailed investigation of the Er3+ 3-μm crystal laser performed so far.

Theoretical investigation of injection-locked high modulation bandwidth quantum cascade lasers.

PubMed

Meng, Bo; Wang, Qi Jie

2012-01-16

In this study, we report for the first time to our knowledge theoretical investigation of modulation responses of injection-locked mid-infrared quantum cascade lasers (QCLs) at wavelengths of 4.6 μm and 9 μm, respectively. It is shown through a three-level rate equations model that the direct intensity modulation of QCLs gives the maximum modulation bandwidths of ~7 GHz at 4.6 μm and ~20 GHz at 9 μm. By applying the injection locking scheme, we find that the modulation bandwidths of up to ~30 GHz and ~70 GHz can be achieved for QCLs at 4.6 μm and 9 μm, respectively, with an injection ratio of 5 dB. The result also shows that an ultrawide modulation bandwidth of more than 200 GHz is possible with a 10 dB injection ratio for QCLs at 9 μm. An important characteristic of injection-locked QCLs is the nonexistence of unstable locking region in the locking map, in contrast to their diode laser counterparts. We attribute this to the ultra-short upper laser state lifetimes of QCLs.

Investigating the CO 2 laser cutting parameters of MDF wood composite material

NASA Astrophysics Data System (ADS)

Eltawahni, H. A.; Olabi, A. G.; Benyounis, K. Y.

2011-04-01

Laser cutting of medium density fibreboard (MDF) is a complicated process and the selection of the process parameters combinations is essential to get the highest quality cut section. This paper presents a means for selecting the process parameters for laser cutting of MDF based on the design of experiments (DOE) approach. A CO 2 laser was used to cut three thicknesses, 4, 6 and 9 mm, of MDF panels. The process factors investigated are: laser power, cutting speed, air pressure and focal point position. In this work, cutting quality was evaluated by measuring the upper kerf width, the lower kerf width, the ratio between the upper kerf width to the lower kerf width, the cut section roughness and the operating cost. The effect of each factor on the quality measures was determined. The optimal cutting combinations were presented in favours of high quality process output and in favours of low cutting cost.

Rate equation modeling of the frequency noise and the intrinsic spectral linewidth in quantum cascade lasers.

PubMed

Wang, Xing-Guang; Grillot, Frédéric; Wang, Cheng

2018-02-05

This work theoretically investigates the frequency noise (FN) characteristics of quantum cascade lasers (QCLs) through a three-level rate equation model, which takes into account both the carrier noise and the spontaneous emission noise through the Langevin approach. It is found that the power spectral density of the FN exhibits a broad peak due to the carrier noise induced carrier variation in the upper laser level, which is enhanced by the stimulated emission process. The peak amplitude is strongly dependent on the gain stage number and the linewidth broadening factor. In addition, an analytical formula of the intrinsic spectral linewidth of QCLs is derived based on the FN analysis. It is demonstrated that the laser linewidth can be narrowed by reducing the gain coefficient and/or accelerating the carrier scattering rates of the upper and the lower laser levels.

Fluoride crystals: materials for near-infrared solid state lasers

NASA Astrophysics Data System (ADS)

Parisi, Daniela; Veronesi, Stefano; Volpi, Azzurra; Gemmi, Mauro; Tonelli, Mauro; Cassanho, Arlete; Jenssen, Hans P.

2013-07-01

In this work we present an overview of the best 2μm laser results obtained in Tm-doped fluoride hosts LiYF4(YLF), LiLuF4 (LLF) and BaY2F8 (BYF) and we report on the growth, spectroscopy and first laser test emission of a novel mixed material BaYLuF8 (BYLF), interesting as a variant of BYF material with a partial substitution of Y3+ ions by Lu3+. The novel host is interesting mainly because indications are that the mixed crystal would be sturdier than BYF. The addition of Lutetium would improve the thermo-mechanical properties going into the direction of high power applications, as suggest from works on YLF and its isomorph LLF. A detailed description of Czochralski growth of fluoride laser materials is provided, focusing on the growth parameters of the novel BYLF:Tm3+12% material grown. With regard of spectroscopy analysis, we report on the results obtained with BYLF host. Detailed absorption, fluorescence and lifetime measurements have been performed focusing on the 3H4 and 3F4 manifolds, the pumping and upper laser level. Moreover diode pumped CW laser emission at 2 μm has been achieved in BYLF: Tm3+12% sample obtaining a slope efficiency of about 28% with respect to the absorbed power.

1.88 Micrometers InGaAsP Pumped, Room Temperature Ho: LuAG Laser

NASA Technical Reports Server (NTRS)

Barnes, Norman P.; Amzajerdian, Farzin; Reichle, Donald J.; Busch, George; Leisher, Paul

2009-01-01

A room temperature, directly diode pumped Ho:LuAG laser oscillated for the first time. Direct pumping of the Ho upper laser manifold maximizes efficiency, minimizes heating, and eliminates Ho:Tm energy sharing. Design and performance are presented.

Comparison of positive-pressure, passive ultrasonic, and laser-activated irrigations on smear-layer removal from the root canal surface.

PubMed

Sahar-Helft, Sharonit; Sarp, Ayşe Sena Kabaş; Stabholtz, Adam; Gutkin, Vitaly; Redenski, Idan; Steinberg, Doron

2015-03-01

The purpose of this study was to compare the efficacy of three irrigation techniques for smear-layer removal with 17% EDTA. Cleaning and shaping the root canal system during endodontic treatment produces a smear layer and hard tissue debris. Three irrigation techniques were tested for solution infiltration of this layer: positive-pressure irrigation, passive ultrasonic irrigation, and laser-activated irrigation. Sixty extracted teeth were divided into six equal groups; 17% EDTA was used for 60 sec irrigation of five of the groups. The groups were as follows: Group 1, treated only with ProTaper™ F3 Ni-Ti files; Group 2, positive-pressure irrigation, with a syringe; Group 3, passive ultrasonic irrigation, inserted 1 mm short of the working length; Group 4, passive ultrasonic irrigation, inserted in the upper coronal third of the root; Group 5, Er:YAG laser-activated irrigation, inserted 1 mm short of the working length; and Group 6, Er:YAG laser-activated irrigation, inserted in the upper coronal third of the root. Scanning electron microscopy showed that the smear layer is removed most efficiently using laser-activated irrigation at low energy with 17% EDTA, inserted either at the working length or only in the coronal upper third of the root. Amounts of Ca, P, and O were not significantly different on all treated dentin surfaces. Smear-layer removal was most effective when the root canals were irrigated using Er:YAG laser at low energy with 17% EDTA solution. Interestingly, removal of the smear layer along the entire canal was similar when the laser was inserted in the upper coronal third and at 1 mm short of the working length of the root canal. This effect was not observed with the ultrasonic and positive-pressure techniques.

Absorption of the laser radiation by the laser plasma with gas microjet targets

NASA Astrophysics Data System (ADS)

Borisevichus, D. A.; Zabrodskii, V. V.; Kalmykov, S. G.; Sasin, M. E.; Seisyan, R. P.

2017-01-01

An upper limit of absorption of the laser radiation in the plasma produced in a gas jet Xe target with the average density of (3-6) × 1018 cm-3 and the effective diameter of 0.7 mm is found. It is equal to ≈50% and remains constant under any variation in this range of densities. This result contradicts both theoretical assessments that have predicted virtually complete absorption and results of earlier experiments with the laser spark in an unlimited stationary Xe gas with the same density, where the upper limit of absorption was close to 100%. An analysis shows that nonlinearity of absorption and plasma nonequilibrium lead to the reduction of the absorption coefficient that, along with the limited size of plasma, can explain the experimental results.

Spectroscopic investigations of ThF and ThF+.

PubMed

Barker, Beau J; Antonov, Ivan O; Heaven, Michael C; Peterson, Kirk A

2012-03-14

The electronic spectra of ThF and ThF(+) have been examined using laser induced fluorescence and resonant two-photon ionization techniques. The results from high-level ab initio calculations have been used to guide the assignment of these data. Spectra for ThF show that the molecule has an X (2)Δ(3/2) ground state. The upper spin-orbit component, X (2)Δ(5/2) was found at an energy of 2575(15) cm(-1). The low-lying states of ThF(+) were probed using dispersed fluorescence and pulsed field ionization-zero kinetic energy (PFI-ZEKE) photoelectron spectroscopy. Vibronic progressions belonging to four electronic states were identified. The lowest energy states were clearly (1)Σ(+) and (3)Δ(1). Although the energy ordering could not be rigorously determined, the evidence favors assignment of (1)Σ(+) as the ground state. The (3)Δ(1) state, of interest for investigation of the electron electric dipole moment, is just 315.0(5) cm(-1) above the ground state. The PFI-ZEKE measurements for ThF yielded an ionization energy of 51 581(3) cm(-1). Molecular constants show that the vibrational constant increases and the bond length shortens on ionization. This is consistent with removal of a non-bonding Th-centered 6d or 7s electron. Laser excitation of ThF(+) was used to probe electronically excited states in the range of 19,000-21,500 cm(-1).

Laser beam joining of optical fibers in silicon V-grooves

NASA Astrophysics Data System (ADS)

Kaufmann, Stefan; Otto, Andreas; Luz, Gerhard

2000-06-01

The increasing use of optical data transmission systems and the development of new optical components require adjustment-insensitive and reliable joining and assembling techniques. The state of the art includes the utilization of silicon submounts with anisotropically etched V-grooves. Several glass fibers are fixed in these V-grooves with adhesive. Adhesive bonds tend towards degradation under the influence of temperature and moisture. For this reason, the alternative joining processes laser beam welding and laser beam soldering are relevant. The goal is a reliable joining of optical fibers in V-grooves without damage to the fibers or the silicon submount. Because of the anomaly of silicon during phase transformation, a positive joining can be realized by laser beam welding. A melt pool is created through the energy of a Nd:YAG-laser pulse. During solidification, the volume of silicon increases and a bump is formed in the center. Experiments have shown that this phenomenon can be used for joining optical fibers in silicon-V-grooves. With suitable parameters the silicon flows half around the fiber during solidification. For each fiber, several welding points are necessary. Another promising joining method is laser bema soldering. In this case, a second silicon sheet with a solder deposit is placed on the fibers which lie in the V-grooves of the metallized silicon submount. The laser heats the upper silicon until the solder metals by heat conduction.

Magnetic field effect on the energy levels of an exciton in a GaAs quantum dot: Application for excitonic lasers.

PubMed

Jahan, K Luhluh; Boda, A; Shankar, I V; Raju, Ch Narasimha; Chatterjee, Ashok

2018-03-22

The problem of an exciton trapped in a Gaussian quantum dot (QD) of GaAs is studied in both two and three dimensions in the presence of an external magnetic field using the Ritz variational method, the 1/N expansion method and the shifted 1/N expansion method. The ground state energy and the binding energy of the exciton are obtained as a function of the quantum dot size, confinement strength and the magnetic field and compared with those available in the literature. While the variational method gives the upper bound to the ground state energy, the 1/N expansion method gives the lower bound. The results obtained from the shifted 1/N expansion method are shown to match very well with those obtained from the exact diagonalization technique. The variation of the exciton size and the oscillator strength of the exciton are also studied as a function of the size of the quantum dot. The excited states of the exciton are computed using the shifted 1/N expansion method and it is suggested that a given number of stable excitonic bound states can be realized in a quantum dot by tuning the quantum dot parameters. This can open up the possibility of having quantum dot lasers using excitonic states.

Temperature-controlled two-wavelength laser soldering of tissues.

PubMed

Gabay, Ilan; Abergel, Avraham; Vasilyev, Tamar; Rabi, Yaron; Fliss, Dan M; Katzir, Abraham

2011-11-01

Laser tissue soldering is a method for bonding of incisions in tissues. A biological solder is spread over the cut, laser radiation heats the solder and the underlying cut edges and the incision is bonded. This method offers many advantages over conventional techniques (e.g., sutures). Past researches have shown that laser soldering, using a single laser, does not provide sufficient strength for bonding of cuts in thick (>1 mm) tissues. This study introduces a novel method for laser soldering of thick tissues, under temperature control, using two lasers, emitting two different wavelengths. An experimental system was built, using two lasers: (i) a CO(2) laser, whose radiation heated the upper surface of the tissue and (ii) a GaAs laser that heated an albumin layer under the tissue. An infrared fiber-optic radiometer monitored the temperature of the tissue. All three devices were connected to a computer that controlled the process. A computer simulation was written to optimize the system parameters. The system was tested on tissue phantoms, to validate the simulation and ensure that both the upper and lower sides of the cut were heated, and that the temperature could be controlled on both sides. The system was then used ex vivo to bond longitudinal cuts of lengths ∼12 mm in the esophagi of large farm pigs. The theoretical simulations showed a good stabilization of the temperatures at the upper and lower tissue surfaces at the target values. Experiments on tissue phantom showed a good agreement with these simulations. Incisions in esophagi, removed from large farm pigs, were then successfully bonded. The mean burst pressure was ∼3.6 m of water. This study demonstrated the capability of soldering cuts in thick tissues, paving the way for new types of surgical applications. Copyright © 2010 Wiley Periodicals, Inc.

Endoscopic Carbon Dioxide Laser Photocoagulation Of Bleeding Canine Gastric Ulcers

NASA Astrophysics Data System (ADS)

Gal, Dov; Ron, Nimrod; Orgad, Uri; Katzir, Abraham

1987-04-01

This is the first report which describes carbon dioxide laser photocoagulation of upper gastrointestinal bleeding via a flexible endoscope, using an infrared transmitting siver nalide fiber. Various laser parameters were checked to determine the optimal conditions for hemostasis. Both the acute effects of laser irradiation on tissue and the chronic effects on healing process were examined. Preliminary results indicate that carbon dioxide laser beam can successfully photocoagulate moderately bleeding ulcers.

Optical microwave interactions in semiconductor devices

NASA Astrophysics Data System (ADS)

Figueroa, L.; Slayman, C. W.; Yen, H. W.

1980-11-01

The results of an extensive characterization of high speed analog modulation of (GaAl)As injection lasers, high speed optical detectors, and mode locking of (GaAl)As injection lasers are presented. Commercial injection lasers were successfully modulated up to 5 GHz. The 5 GHz value represents a practical upper limit to the modulation bandwith of existing commercial lasers. The laser equivalent circuit was characterized and the parasitics were found to play a significant role in the high speed modulation of the injection laser.

Producing coherent excitations in pumped Mott antiferromagnetic insulators

NASA Astrophysics Data System (ADS)

Wang, Yao; Claassen, Martin; Moritz, B.; Devereaux, T. P.

2017-12-01

Nonequilibrium dynamics in correlated materials has attracted attention due to the possibility of characterizing, tuning, and creating complex ordered states. To understand the photoinduced microscopic dynamics, especially the linkage under realistic pump conditions between transient states and remnant elementary excitations, we performed nonperturbative simulations of various time-resolved spectroscopies. We used the Mott antiferromagnetic insulator as a model platform. The transient dynamics of multiparticle excitations can be attributed to the interplay between Floquet virtual states and a modification of the density of states, in which interactions induce a spectral weight transfer. Using an autocorrelation of the time-dependent spectral function, we show that resonance of the virtual states with the upper Hubbard band in the Mott insulator provides the route towards manipulating the electronic distribution and modifying charge and spin excitations. Our results link transient dynamics to the nature of many-body excitations and provide an opportunity to design nonequilibrium states of matter via tuned laser pulses.

[The new potentials of magneto-laser therapy and electrostimulation in children with cleft palate and upper lip].

PubMed

Gerasimenko, M Iu; Filatova, E V; Borisenko, O V; Levchenkova, V D; Grishina, N V; Spiridonova, N Z; Shevchenko, E Iu; Goncharenko, L L

2000-01-01

The paper presents rationale for design of new procedures of physiotherapy in children with expanded palate and upper lip; morphofunctional features of prenatal and early postnatal formation of central nervous system; a multilayer technique of magneto-laser radiation to the projection of the anterior central gyrus and the technique of electrostimulation by the system of the wink reflex which can influence central mechanisms of regulation and adaptation before and early after uranoplasty and cheiloplasty.

An Experimental Study on Micro Clinching of Metal Foils with Cutting by Laser Shock Forming.

PubMed

Wang, Xiao; Li, Cong; Ma, Youjuan; Shen, Zongbao; Sun, Xianqing; Sha, Chaofei; Gao, Shuai; Li, Liyin; Liu, Huixia

2016-07-13

This paper describes a novel technique for joining similar and dissimilar metal foils, namely micro clinching with cutting by laser shock forming. A series of experiments were conducted to study the deformation behavior of single layer material, during which many important process parameters were determined. The process window of the 1060 pure aluminum foils and annealed copper foils produced by micro clinching with cutting was analyzed. Moreover, similar material combination (annealed copper foils) and dissimilar material combination (1060 pure aluminum foils and 304 stainless steel foils) were successfully achieved. The effect of laser energy on the interlock and minimum thickness of upper foils was investigated. In addition, the mechanical strength of different material combinations joined by micro clinching with cutting was measured in single lap shearing tests. According to the achieved results, this novel technique is more suitable for material combinations where the upper foil is thicker than lower foil. With the increase of laser energy, the interlock increased while the minimum thickness of upper foil decreased gradually. The shear strength of 1060 pure aluminum foils and 304 stainless steel foils combination was three times as large as that of 1060 pure aluminum foils and annealed copper foils combination.

Measurement of subcutaneous adipose tissue blood flow in the morbidly obese using a laser Doppler velocimeter

NASA Astrophysics Data System (ADS)

Klassen, Gerald A.; Paton, Barry E.; Maksym, Geoff; Janigan, David; Perey, Bernard

1992-08-01

Using a laser Doppler velocimeter (LDV) subcutaneous adipose tissue blood flow (AF) was recorded in the upright and supine positions in the upper and lower abdomen in 22 morbidly obese patients before gastroplasty. Age was 42 +/- 3 (mean +/- SEM), weight 135 +/- 7 kg, and body mass index (BMI) 51 +/- 3. Adipose flow expressed as mV was: supine, upper abdomen 647 +/- 23, lower abdomen 604 +/- 24; upright, upper abdomen 621 +/- 27, lower abdomen 607 +/- 29. AF was significantly more in the upper than lower abdomen (supine position) and AF was significantly lower in the lower abdomen upright than the upper abdomen supine. Regression analysis of age indicates that blood flow decreases in the lower abdomen so that in the supine position the difference between upper and lower abdomen AF increases. Similar analysis of BMI did not indicate significant trends. These data indicate that with morbid obesity there is lower tissue blood flow to the lower abdomen. This may explain why such patients may develop areas of painful ischemic necrosis in the dependent region of their anterior abdominal pannus.

Active space debris removal by using laser propulsion

NASA Astrophysics Data System (ADS)

Rezunkov, Yu. A.

2013-03-01

At present, a few projects on the space debris removal by using highpower lasers are developed. One of the established projects is the ORION proposed by Claude Phipps from Photonics Associates Company and supported by NASA (USA) [1]. But the technical feasibility of the concept is limited by sizes of the debris objects (from 1 to 10 cm) because of a small thrust impulse generated at the laser ablation of the debris materials. At the same time, the removal of rocket upper stages and satellites, which have reached the end of their lives, has been carried out only in a very small number of cases and most of them remain on the Low Earth Orbits (LEO). To reduce the amount of these large-size objects, designing of space systems allowing deorbiting upper rocket stages and removing large-size satellite remnants from economically and scientifically useful orbits to disposal ones is considered. The suggested system is based on high-power laser propulsion. Laser-Orbital Transfer Vehicle (LOTV) with the developed aerospace laser propulsion engine is considered as applied to the problem of mitigation of man-made large-size space debris in LEO.

Method and device for controlling plume during laser welding

DOEpatents

Fuerschbach, Phillip W.; Jellison, James L.; Keicher, David M.; Oberkampf, William L.

1991-01-01

A method and apparatus for enhancing the weldment of a laser welding system is provided. The laser weld plume control device includes a cylindrical body defining an upside-down cone cavity; the upper surface of the body circumscribes the base of the cone cavity, and the vertex of the cone cavity forms an orifice concentrically located with respect to the laser beam and the plume which forms as a result of the welding operation. According to the method of the invention, gas is directed radially inward through inlets in the upper surface of the body into and through channels in the wall of the body and finally through the orifice of the body, and downward onto the surface of the weldment. The gas flow is then converted by the orifice of the device from radial flow to an axisymmetric gas jet flowing away from the weldment surface in a direction perpendicular to the surface and opposite to that of the laser.

Air Vehicle Integration and Technology Research (AVIATR). Delivery Order 0002: Condition-Based Maintenance Plus Structural Integrity (CBM+SI) Strategy Development

DTIC Science & Technology

2010-11-01

material. The rubber is laser -etched with rows of tiny, interconnected channels or galleries, to which air pressure is applied. Any propagating crack... clad one side. The Upper Lobe has a radius of approximately 85” (compound curvature) in the region of interest. As stated previously, the skin is...7079-T6 sheet; clad one side with a varying thickness of 0.050” to 0.071” (varies according to stability requirements for compression combined with

Study of the relaxation rate of photoexcited indole molecules by the interferometric pump-and-probe method at picosecond resolution

NASA Astrophysics Data System (ADS)

Glazov, A. L.; Il'ina, A. D.; Sukharev, A. A.; Vasyutinskii, O. S.

2017-09-01

We present a new interferometric method that can be used for studying the dynamics of photoinduced processes in biologically important molecules at ultrahigh temporal resolution. The method is based upon the detection of changes in the refractive index of a substance excited by pulsed radiation of a femtosecond laser, which are measured by the pump-and-probe technique using time-delayed pulses of the same laser. The high sensitivity and stability of the interferometer allow this method to be used for monitoring variation of the concentration of short-lived excited states of biomolecules in solution. The proposed method has been verified by application to indole solutions in propylene glycol. The upper estimate of the lifetime of photoexcited indole molecules in solution amounted to about 40 ps.

The near infrared spectrum of ozone by CW-cavity ring down spectroscopy between 5850 and 7000 cm(-1): new observations and exhaustive review.

PubMed

Campargue, A; Barbe, A; De Backer-Barilly, M-R; Tyuterev, Vl G; Kassi, S

2008-05-28

Weak vibrational bands of (16)O(3) could be detected in the 5850-7030 cm(-1) spectral region by CW-cavity ring down spectroscopy using a set of fibered DFB diode lasers. As a result of the high sensitivity (noise equivalent absorption alpha(min) approximately 3 x 10(-10) cm(-1)), bands reaching a total of 16 upper vibrational states have been previously reported in selected spectral regions. In the present report, the analysis of the whole investigated region is completed by new recordings in three spectral regions which have allowed: (i) a refined analysis of the nu(1) + 3nu(2) + 3nu(3) band from new spectra in the 5850-5900 cm(-1) region; (ii) an important extension of the assignments of the 2nu(1)+5nu(3) and 4nu(1) + 2nu(2) + nu(3) bands in the 6500-6600 cm(-1) region, previously recorded by frequency modulation diode laser spectroscopy. The rovibrational assignments of the weak 4nu(1) + 2nu(2) + nu(3) band were fully confirmed by the new observation of the 4nu(1) + 2nu(2) + nu(3)- nu(2) hot band near 5866.9 cm(-1) reaching the same upper state; (iii) the observation and modelling of three A-type bands at 6895.51, 6981.87 and 6990.07 cm(-1) corresponding to the highest excited vibrational bands of ozone detected so far at high resolution. The upper vibrational states were assigned by comparison of their energy values with calculated values obtained from the ground state potential energy surface of (16)O(3). The vibrational mixing and consequently the ambiguities in the vibrational labelling are discussed. For each band or set of interacting bands, the spectroscopic parameters were determined from a fit of the corresponding line positions in the frame of the effective Hamiltonian (EH) model. A set of selected absolute line intensities was measured and used to derive the parameters of the effective transition moment operator. The exhaustive review of the previous observations gathered with the present results is presented and discussed. It leads to a total number of 3863 energy levels belonging to 21 vibrational states and corresponding to 7315 transitions. In the considered spectral region corresponding to up to 82% of the dissociation energy, the increasing importance of the "dark" states is illustrated by the occurrence of frequent rovibrational perturbations and the observation of many weak lines still unassigned.

High-resolution spectroscopy of the C-N stretching band of methylamine

NASA Astrophysics Data System (ADS)

Lees, Ronald M.; Sun, Zhen-Dong; Billinghurst, B. E.

2011-09-01

The C-N stretching infrared fundamental of CH3NH2 has been investigated by high-resolution laser sideband and Fourier transform synchrotron spectroscopy to explore the energy level structure and to look for possible interactions with high-lying torsional levels of the ground state and other vibrational modes. The spectrum is complicated by two coupled large-amplitude motions in the molecule, the CH3 torsion and the NH2 inversion, which lead to rich spectral structure with a wide range of energy level splittings and relative line intensities. Numerous sub-bands have been assigned for K values ranging up to 12 for the stronger a inversion species for the vt = 0 torsional state, along with many of the weaker sub-bands of the s species. The C-N stretching sub-state origins have been determined by fitting the upper-state term values to J(J + 1) power-series expansions. For comparison with the ground-state behaviour, both ground and C-N stretch origins have been fitted to a phenomenological Fourier series model that produces an interesting pattern with the differing periodicities of the torsional and inversion energies. The amplitude of the torsional energy oscillation increases substantially for the C-N stretch, while the amplitude of the inversion energy oscillation is relatively unchanged. Independent inertial scale factors ρ were fitted for the torsion and the inversion and differ significantly in the upper state. The C-N stretching vibrational energy is determined to be 1044.817 cm-1, while the effective upper state B-value is 0.7318 cm-1. Several anharmonic resonances with vt = 4 ground-state levels have been observed and partially characterized. A variety of J-localized level-crossing resonances have also been seen, five of which display forbidden transitions arising from intensity borrowing that allow determination of the interaction coupling constants.

2.5 MHz Line-Width High-energy, 2 Micrometer Coherent Wind Lidar Transmitter

NASA Technical Reports Server (NTRS)

Petros, Mulugeta; Yu, Jirong; Trieu, Bo; Bai, Yingxin; Petzar, Paul; Singh, Upendra N.; Reithmaier, Karl

2007-01-01

2 micron solid-state lasers are the primary choice for coherent Doppler wind detection. As wind lidars, they are used for wake vortex and clear air turbulence detection providing air transport safety. In addition, 2 micron lasers are one of the candidates for CO2 detection lidars. The rich CO2 absorption line around 2 micron, combined with the long upper state life of time, has made Ho based 2 micron lasers a viable candidate for CO2 sensing DIAL instrument. The design and fabrication of a compact coherent laser radar transmitter for Troposphere wind sensing is under way. This system is hardened for ground as well as airborne applications. As a transmitter for a coherent wind lidar, this laser has stringent spectral line width and beam quality requirements. Although the absolute wavelength does not have to be fixed for wind detection, to maximize return signal, the output wavelength should avoid atmospheric CO2 and H2O absorption lines. The base line laser material is Ho:Tm:LuLF which is an isomorph of Ho:Tm:YLF. LuLF produces 20% more output power than Ho:Tm:YLF. In these materials the Tm absorption cross-section, the Ho emission cross-section, the Tm to Ho energy transfer parameters and the Ho (sup 5) I (sub 7) radiative life time are all identical. However, the improved performance of the LuLF is attributed to the lower thermal population in the (sup 5) I (sub 8) manifold. It also provides higher normal mode to Q-switch conversion than YLF at high pump energy indicating a lower up-conversion. The laser architecture is composed of a seed laser, a ring oscillator, and a double pass amplifier. The seed laser is a single longitudinal mode with a line width of 13 KHz. The 100mJ class oscillator is stretched to 3 meters to accommodate the line-width requirement without compromising the range resolution of the instrument. The amplifier is double passed to produce greater than 300mJ energy.

A new laboratory source of ozone and its potential atmospheric implications

NASA Astrophysics Data System (ADS)

Slanger, T. G.; Jusinski, L. E.; Black, G.; Gadd, G. E.

1988-08-01

Although 248-nm radiation falls 0.12 eV short of the energy needed to dissociate O2, large densities of ozone (O3) can be produced from unfocused 248-nm KrF excimer laser irradiation of pure O2. As soon as any O3 is present, it strongly absorbs the 248-nanometer radiation and dissociates to vibrationally excited ground state O2 (among other products), with a quantum yield of 0.1 to 0.15. During the laser pulse, a portion of these molecules absorb a photon and dissociate, which results in the production of three oxygen atoms for one O3 molecule destroyed. Recombination then converts these atoms to O3, and thus O3 production in the system is autocatalytic. A deficiency exists in current models of O3 photochemistry in the upper stratosphere and mesosphere, in that more O3 is found than can be explained. A detailed analysis of the system as it applies to the upper atmosphere is not yet possible, but with reasonable assumptions about O2 vibrational distributions resulting from O3 photodissociation and about relaxation rates of vibrationally excited O2, a case can be made for the importance of including this mechanism in the models.

Laser Induced Fluorescence Spectroscopy of Jet-Cooled CaOCa

NASA Astrophysics Data System (ADS)

Sullivan, Michael N.; Frohman, Daniel J.; Heaven, Michael; Fawzy, Wafaa M.

2016-06-01

The group IIA metals have stable hypermetallic oxides of the general form MOM. Theoretical interest in these species is associated with the multi-reference character of the ground states. It is now established that the ground states can be formally assigned to the M+O^{2-M+} configuration, which leaves two electrons in orbitals that are primarily metal-centered ns orbitals. Hence the MOM species are diradicals with very small energy spacings between the lowest energy singlet and triplet states. Previously, we have characterized the lowest energy singlet transition (1Σ^{+u← X1Σ+g}) of BeOBe. In this study we obtained the first electronic spectrum of CaOCa. Jet-cooled laser induced fluorescence spectra were recorded for multiple bands that occured within the 14,800 - 15,900 cm-1 region. Most of the bands exhibited simple P/R branch rotational line patterns that were blue-shaded. Only even rotational levels were observed, consistent with the expected X 1Σ^{+g} symmetry of the ground state (40Ca has zero nuclear spin). A progression of excited bending modes was evident in the spectrum, indicating that the transition is to an upper state that has a bent equilibrium geometry. Molecular constants were extracted from the rovibronic bands using PGOPHER. The experimental results and interpretation of the spectrum, which was guided by the predictions of electronic structure calculation, will be presented.

An Experimental Study on Micro Clinching of Metal Foils with Cutting by Laser Shock Forming

PubMed Central

Wang, Xiao; Li, Cong; Ma, Youjuan; Shen, Zongbao; Sun, Xianqing; Sha, Chaofei; Gao, Shuai; Li, Liyin; Liu, Huixia

2016-01-01

This paper describes a novel technique for joining similar and dissimilar metal foils, namely micro clinching with cutting by laser shock forming. A series of experiments were conducted to study the deformation behavior of single layer material, during which many important process parameters were determined. The process window of the 1060 pure aluminum foils and annealed copper foils produced by micro clinching with cutting was analyzed. Moreover, similar material combination (annealed copper foils) and dissimilar material combination (1060 pure aluminum foils and 304 stainless steel foils) were successfully achieved. The effect of laser energy on the interlock and minimum thickness of upper foils was investigated. In addition, the mechanical strength of different material combinations joined by micro clinching with cutting was measured in single lap shearing tests. According to the achieved results, this novel technique is more suitable for material combinations where the upper foil is thicker than lower foil. With the increase of laser energy, the interlock increased while the minimum thickness of upper foil decreased gradually. The shear strength of 1060 pure aluminum foils and 304 stainless steel foils combination was three times as large as that of 1060 pure aluminum foils and annealed copper foils combination. PMID:28773692

The effects of magnesium doping on the modal loss in AlGaN-based deep UV lasers

NASA Astrophysics Data System (ADS)

Martens, M.; Kuhn, C.; Simoneit, T.; Hagedorn, S.; Knauer, A.; Wernicke, T.; Weyers, M.; Kneissl, M.

2017-02-01

Absorption losses in the Mg-doped layers significantly contribute to the modal losses in group-III-nitride-based lasers. In this paper, we investigate the influence of Mg-doping on the modal absorption of optically pumped UVC lasers grown on epitaxially laterally overgrown AlN/sapphire substrates with an averaged threading dislocation density of 1 × 109 cm-2. By varying the setback of the Mg-doping (˜1 × 1020 cm-3) within the upper Al0.70Ga0.30N waveguide layer, the overlap of the optical mode with the Mg-doped region increases. For all structures, internal losses were derived from gain spectra obtained by the variable stripe length method. The internal losses increase from 10 cm-1 for lasers without Mg-doping to 28 cm-1 for lasers with a fully Mg-doped upper waveguide layer. The overlap of the optical mode with the Mg-doped waveguide ΓMg clearly correlates with the modal losses. This allows to calculate the Mg-induced losses in current injection laser diodes by αm o d M g = Γ M g × 50 cm - 1 .

Atomic Processes for XUV Lasers: Alkali Atoms and Ions

NASA Astrophysics Data System (ADS)

Dimiduk, David Paul

The development of extreme ultraviolet (XUV) lasers is dependent upon knowledge of processes in highly excited atoms. Described here are spectroscopy experiments which have identified and characterized certain autoionizing energy levels in core-excited alkali atoms and ions. Such levels, termed quasi-metastable, have desirable characteristics as upper levels for efficient, powerful XUV lasers. Quasi -metastable levels are among the most intense emission lines in the XUV spectra of core-excited alkalis. Laser experiments utilizing these levels have proved to be useful in characterizing other core-excited levels. Three experiments to study quasi-metastable levels are reported. The first experiment is vacuum ultraviolet (VUV) absorption spectroscopy on the Cs 109 nm transitions using high-resolution laser techniques. This experiment confirms the identification of transitions to a quasi-metastable level, estimates transition oscillator strengths, and estimates the hyperfine splitting of the quasi-metastable level. The second experiment, XUV emission spectroscopy of Ca II and Sr II in a microwave-heated plasma, identifies transitions from quasi-metastable levels in these ions, and provides confirming evidence of their radiative, rather than autoionizing, character. In the third experiment, core-excited Ca II ions are produced by inner-shell photoionization of Ca with soft x-rays from a laser-produced plasma. This preliminary experiment demonstrated a method of creating large numbers of these highly-excited ions for future spectroscopic experiments. Experimental and theoretical evidence suggests the CA II 3{ rm p}^5 3d4s ^4 {rm F}^circ_{3/2 } quasi-metastable level may be directly pumped via a dipole ionization process from the Ca I ground state. The direct process is permitted by J conservation, and occurs due to configuration mixing in the final state and possibly the initial state as well. The experiments identifying and characterizing quasi-metastable levels are compared to calculations using the Hartree-Fock code RCN/RCG. Calculated parameters include energy levels, wavefunctions, and transition rates. Based on an extension of this code, earlier unexplained experiments showing strong two-electron radiative transitions from quasi-metastable levels are now understood.

Excitation of photosystem I by 760 nm femtosecond laser pulses: transient absorption spectra and intermediates

NASA Astrophysics Data System (ADS)

Cherepanov, Dmitry A.; Shelaev, Ivan V.; Gostev, Fedor E.; Mamedov, Mahir D.; Petrova, Anastasia A.; Aybush, Arseniy V.; Shuvalov, Vladimir A.; Semenov, Alexey Yu; Nadtochenko, Victor A.

2017-09-01

Excitation of photosystem I (PS I) by a femtosecond 760 nm pump leads to one- and two-photon absorption. The one-photon excitation produces intermediates with transient absorption spectra similar to the spectra of the primary [{{{P}}700}+{{{A}}0}-{{A}}1] and secondary [{{{P}}700}+{{A}}0{{{A}}1}-] ion-radical pairs in the PS I reaction center. The two-photon absorption generates the upper level excited states of chlorophyll (Chl) and carotenoid molecules in the antenna. These excited states are converted into the long-lived intermediates and can be tentatively attributed to the excited and charge-transfer ion-radical states of Chl molecules and to the excited states of carotenoids in the antenna. The transient spectra of intermediates generated by two-photon excitation differ from the transient one-photon spectra of the primary and secondary ion-radical pairs.

Comparison of different laser systems in the treatment of hypertrophic and atrophic scars and keloids

NASA Astrophysics Data System (ADS)

Scharschmidt, D.; Algermissen, Bernd; Willms-Jones, J.-C.; Philipp, Carsten M.; Berlien, Hans-Peter

1997-12-01

Different laser systems and techniques are used for the treatment of hypertrophic scars, keloids and acne scars. Significant criteria in selecting a suitable laser system are the scar's vascularization, age and diameter. Flashlamp- pumped dye-lasers, CO2-lasers with scanner, Argon and Nd:YAG-lasers are used. Telangiectatic scars respond well to argon lasers, erythematous scars and keloids to dye-laser treatment. Using interstitial Nd:YAG-laser vaporization, scars with a cross-section over 1 cm can generally be reduced. For the treatment of atrophic and acne scars good cosmetic results are achieved with a CO2-laser/scanner system, which allows a precise ablation of the upper dermis with low risk of side-effects.

Structure Formation in Complex Plasma

DTIC Science & Technology

2011-08-24

Dewer bottle (upper figures) or in the vapor of liquid helium (lower figures). Liq. He Ring electrode Particles Green Laser RF Plasma ... Ring electrode CCD camera Prism mirror Liq. He Glass Tube Liq. N2 Glass Dewar Acrylic particles Gas Helium Green Laser CCD camera Pressure

Transendoscopic Nd:YAG ablation of cystic lesions in 27 large animals: 1986-1995

NASA Astrophysics Data System (ADS)

Tate, Lloyd P.

1997-05-01

Hospital medical surgery records and laser logs were examined to determine the population of large animals presented to the College of Veterinary Medicine treated by laser and conventional means for cystic lesions. Cystic lesions were most frequently found in 2 anatomical locations: endometrial cysts and upper respiratory cysts. The majority of endometrial cysts were considered to be acquired, whereas the most frequently encountered upper respiratory cysts were believed to be congenital due to the fact they were most frequently seen in young animals. Nine mares, totaling 42 endometrial cysts, were presented to the Veterinary Teaching Hospital (VTH), all of which had been treated by transendoscopic Nd:YAG laser ablation. Eighteen of the respiratory cysts in the same time period were presented to the VTH, of which 10 received conventional surgery and 8 were laser photoablated. Respiratory cysts treated by conventional surgery were generally found in locations inaccessible to visualization by transendoscopic technique, and thus required a surgical approach under general anesthesia. All mares with endometrial cysts were presented with a history of conception failure. After laser ablation, a majority of the mares were able to carry a foal to term and none represented with recurrence of endometrial cysts. Horses that presented with upper respiratory cysts also did not experience recurrence of cysts; although several horses, 1 treated by laser ablation and 4 treated by conventional surgery for frontal and/or maxillary sinus cysts, had transitory sinusitis. Transendoscopic Nd:YAG photoablation of cysts appears to be a very satisfactory means of treating this particular form of lesion in large animals with minimal complications and it can be performed with the animal in a standing position as an outpatient.

Dermal Remodeling of Burn Scar by Fractional CO2 Laser.

PubMed

Lee, Sang-Jun; Suh, Dong-Hye; Lee, Ji Min; Song, Kye-Yong; Ryu, Hwa Jung

2016-10-01

Ablative CO2 fractional lasers have recently been introduced for burn scar treatment because of pronounced clinical outcomes with fewer treatment sessions than nonablative fractional laser. This study was conducted to observe clinical as well as histologic changes of burn scars after treatment with CO2 fractional laser. Eleven patients (one female and 10 males, aged 31-59 years) with skin phototypes III to V with burn scars received 10 sessions of fractional CO2 laser treatments (UltraPulse(®) Encore; Lumenis, Santa Clara, CA, USA) over an average 5-week interval. Two passes were performed using the following parameters: deep FX mode, 12.5-30 mJ, with a density setting of 5-10 %. Clinical evaluations by three blinded dermatologists were obtained at baseline and at 6 months after the final treatment via photographs using the Vancouver scar scale (VSS). Skin biopsies were done on four patients before and after treatment. All patients showed clinical improvement in their scars with significant decrease in VSS. Histologic findings showed the changes in the upper dermis with newly formed dermal papilla. This characteristic upper dermis change was presented as improvement in surface smoothness and skin tension clinically. Postinflammatory hyperpigmentation and itching sensation were the most common adverse effects. Burn scar treatment by fractional CO2 laser is effective by forming new collagen fibers mainly in the upper dermis. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Observation of the fluorescence spectrum for a driven cascade model system in atomic beam.

PubMed

Tian, Si-Cong; Wang, Chun-Liang; Tong, Cun-Zhu; Wang, Li-Jun; Wang, Hai-Hua; Yang, Xiu-Bin; Kang, Zhi-Hui; Gao, Jin-Yue

2012-10-08

We experimentally study the resonance fluorescence from an excited two-level atom when the atomic upper level is coupled by a nonresonant field to a higher-lying state in a rubidium atomic beam. The heights, widths and positions of the fluorescence peaks can be controlled by modifying the detuning of the auxiliary field. We explain the observed spectrum with the transition properties of the dressed states generated by the coupling of the two laser fields. We also attribute the line narrowing to the effects of Spontaneously Generated Coherence between the close-lying levels in the dressed state picture generated by the auxiliary field. And the corresponding spectrum can be viewed as the evidence of Spontaneously Generated Coherence. The experimental results agree well with calculations based on the density-matrix equations.

Toward a New Capability for Upper Atmospheric Research using Atomic Oxygen Lidar

NASA Astrophysics Data System (ADS)

Clemmons, J. H.; Steinvurzel, P.; Mu, X.; Beck, S. M.; Lotshaw, W. T.; Rose, T. S.; Hecht, J. H.; Westberg, K. R.; Larsen, M. F.; Chu, X.; Fritts, D. C.

2017-12-01

Progress on development of a lidar system for probing the upper atmosphere based on atomic oxygen resonance is presented and discussed. The promise of a fully-developed atomic oxygen lidar system, which must be based in space to measure the upper atmosphere, for yielding comprehensive new insights is discussed in terms of its potential to deliver global, height-resolved measurements of winds, temperature, and density at a high cadence. An overview of the system is given, and its measurement principles are described, including its use of 1) a two-photon transition to keep the optical depth low; 2) laser tuning to provide the Doppler information needed to measure winds; and 3) laser tuning to provide a Boltzmann temperature measurement. The current development status is presented with a focus on what has been done to demonstrate capability in the laboratory and its evolution to a funded sounding rocket investigation designed to make measurements of three-dimensional turbulence in the upper mesosphere and lower thermosphere.

Ultrafast studies of the excited-state dynamics of copper and nickel phthalocyanine tetrasulfonates: potential sensitizers for the two-photon photodynamic therapy of tumors.

PubMed

Fournier, Michel; Pépin, Claude; Houde, Daniel; Ouellet, René; van Lier, Johan E

2004-01-01

In order to evaluate the potential of copper and nickel phthalocyanine tetrasulfonates as sensitizers for two-photon photodynamic therapy, we conducted kinetic femtosecond measurements of transient absorption and bleaching of their excited state dynamics in aqueous solution. Samples were pumped with 620 nm and 310 nm laser light, which allowed us to study relaxation processes from both the first and second singlet (or doublet for the copper phthalocyanine) excited states. A second excitation from the first excited triplet state, approximately 685 and 105 ps after the first excitation for copper and nickel phthalocyanine tetrasulfonate respectively, was the most efficient way to bring the molecules to an upper triplet state. Presumably this highest triplet state can inflict molecular damage on adjacent biomolecules int eh absence of oxygen, resulting in the desired cytotoxic cellular response. Transient absorption spectra at different fixed delays indicate that optimum efficiency would require that the second photon has a wavelength of approximately 750 nm.

Producing coherent excitations in pumped Mott antiferromagnetic insulators

DOE PAGES

Wang, Yao; Claassen, Martin; Moritz, B.; ...

2017-12-15

Nonequilibrium dynamics in correlated materials has attracted attention due to the possibility of characterizing, tuning, and creating complex ordered states. To understand the photoinduced microscopic dynamics, especially the linkage under realistic pump conditions between transient states and remnant elementary excitations, we performed nonperturbative simulations of various time-resolved spectroscopies. We used the Mott antiferromagnetic insulator as a model platform. The transient dynamics of multi-particle excitations can be attributed to the interplay between Floquet virtual states and a modification of the density of states, in which interactions induce a spectral weight transfer. Using an autocorrelation of the time-dependent spectral function, we showmore » that resonance of the virtual states with the upper Hubbard band in the Mott insulator provides the route towards manipulating the electronic distribution and modifying charge and spin excitations. In conclusion, our results link transient dynamics to the nature of many-body excitations and provide an opportunity to design nonequilibrium states of matter via tuned laser pulses.« less

Imprinting on empty hard gelatin capsule shells containing titanium dioxide by application of the UV laser printing technique.

PubMed

Hosokawa, Akihiro; Kato, Yoshiteru; Terada, Katsuhide

2014-08-01

The purpose of this study was to examine the application of ultraviolet (UV) laser irradiation to printing hard gelatin capsule shells containing titanium dioxide (TiO2) and to clarify how the color strength of the printing by the laser could be controlled by the power of the irradiated laser. Hard gelatin capsule shells containing 3.5% TiO2 were used in this study. The capsules were irradiated with pulsed UV laser at a wavelength of 355 nm. The color strength of the printed capsule was determined by a spectrophotometer as total color difference (dE). The capsules could be printed gray by the UV laser. The formation of many black particles which were agglomerates of oxygen-defected TiO2 was associated with the printing. In the relationship between laser peak power of a pulse and dE, there were two inflection points. The lower point was the minimal laser peak power to form the black particles and was constant regardless of the dosage forms, for example film-coated tablets, soft gelatin capsules and hard gelatin capsules. The upper point was the minimal laser peak power to form micro-bubbles in the shells and was variable with the formulation. From the lower point to the upper point, the capsules were printed gray and the dE of the printing increased linearly with the laser peak power. Hard gelatin capsule shells containing TiO2 could be printed gray using the UV laser printing technique. The color strength of the printing could be controlled by regulating the laser energy between the two inflection points.

A multi-wavelength fiber-optic temperature-controlled laser soldering system for upper aerodigestive tract reconstruction: an animal model.

PubMed

Abergel, Avraham; Gabay, Ilan; Fliss, Dan M; Katzir, Abraham; Gil, Ziv

2011-06-01

Laser soldering of a thick multilayer organ using conventional CO(2) lasers is ineffective. The purpose of this work was to develop a method for bonding the multilayer tissue of the upper aerodigestive tracts (UADT) without the need of sutures or stapling. Animal model. Academic research laboratory. The authors developed a multi-wavelength laser system, based on 2 fiber-optic lasers applied simultaneously. A highly absorbable CO(2) laser interacts with the muscular layer, and a nonabsorbable GaAs laser interacts with indocyanine-green solid albumin, placed between the mucosa and the muscular layer. The authors used an ex vivo porcine model to examine the capability of this system to effectively correct esophageal tears. The soldered esophagi burst pressure was >175 cm H(2)O (98% success rate) in 88 of the 90 experiments. A conventional CO(2) laser soldering resulted in insufficient bonding (mean burst pressure of 40 ± 7 cm H(2)O, n = 5), while the multi-wavelength laser system provided an ~9-fold tighter seal (359 ± 75.4 cm H(2)O, P < .0001, n = 15). Burst pressures after conventional suturing of the defect was significantly lower (106 ± 65.8 cm H(2)O, P < .001) than in the multi-wavelength laser system. Bonding of the UADT mucosa using a multi-wavelength, temperature-controlled laser soldering system can support significantly higher pressures then conventional CO(2) laser soldering and suture repair. The mean bonding pressure was 3.5-fold higher than the maximal swallowing pressure. Our findings provide a basis for implementation of new surgical tools for repair of esophageal perforations.

Development of ultraviolet lasers

NASA Technical Reports Server (NTRS)

Walters, G. K.

1974-01-01

The pulsed electron accelerator selected for use in the development of ultraviolet laser capability suitable for use in photoexcitation and photoionization studies of the upper atmosphere is reported. Performance figures, installation specifications, and total cost of the equipment are briefly shown, and plans for further studies are outlined.

Extraction-controlled terahertz frequency quantum cascade lasers with a diagonal LO-phonon extraction and injection stage.

PubMed

Han, Y J; Li, L H; Grier, A; Chen, L; Valavanis, A; Zhu, J; Freeman, J R; Isac, N; Colombelli, R; Dean, P; Davies, A G; Linfield, E H

2016-12-12

We report an extraction-controlled terahertz (THz)-frequency quantum cascade laser design in which a diagonal LO-phonon scattering process is used to achieve efficient current injection into the upper laser level of each period and simultaneously extract electrons from the adjacent period. The effects of the diagonality of the radiative transition are investigated, and a design with a scaled oscillator strength of 0.45 is shown experimentally to provide the highest temperature performance. A 3.3 THz device processed into a double-metal waveguide configuration operated up to 123 K in pulsed mode, with a threshold current density of 1.3 kA/cm² at 10 K. The QCL structures are modeled using an extended density matrix approach, and the large threshold current is attributed to parasitic current paths associated with the upper laser levels. The simplicity of this design makes it an ideal platform to investigate the scattering injection process.

Treatment of patients with OSAS using Nd-YAG laser

NASA Astrophysics Data System (ADS)

Kukwa, Andrzej; Tulibacki, Marek P.; Zajac, Andrzej; Dudziec, Katarzyna

2000-06-01

The authors present their clinical experience regarding the possibilities of application of Nd:YAG and Ho:YAG lasers for the treatment of disorders in the are of the upper respiratory tract. The patients with symptoms of Obstructive Sleep Aphnoe Syndrom need a various operations techniques. Lasers techniques makes it possible to perform a number of procedures in local anesthesia which considerably improves the economic effectiveness of the treatment. The surgeries performed using laser beam enabled very good effect of treatment.

Application of the UV laser printing technique to soft gelatin capsules containing titanium dioxide in the shells.

PubMed

Hosokawa, Akihiro; Kato, Yoshiteru

2012-03-01

The purpose of this study was to examine application of ultraviolet (UV) laser irradiation to printing soft gelatin capsules containing titanium dioxide (TiO(2)) in the shells and to study effect of UV laser power on the color strength of printing on the soft gelatin capsules. Size 6 Oval type soft gelatin capsules of which shells contained 0.685% TiO(2) and 0.005% ferric dioxide were used in this study. The capsules were irradiated pulsed UV laser at a wavelength 355 nm. The color strength of the printed capsules was determined by a spectrophotometer as total color difference (dE). The soft gelatin capsules which contained TiO(2) in the shells could be printed gray by the laser. Many black particles, which were associated with the printing, were formed at the colored parts of the shells. It was found that there were two inflection points in relationship between output laser energy of a pulse and dE. Below the lower point, the capsules were not printed. From the lower point to the upper point, the capsules were printed gray and total color difference of the printing increased linearly in proportion with the output laser energy. Beyond the upper point, total color difference showed saturation because of micro-bubbles formation at the laser irradiated spot. Soft gelatin capsules containing TiO(2) in the shells could be performed stable printing using the UV laser printing technique. Color strength of the printing could be controlled by regulating the laser energy between the two inflection points.

Electronic structure, irreversibility line and magnetoresistance of Cu 0.3Bi 2Se 3 superconductor

DOE PAGES

Hemian, Yi; Gu, Genda; Chen, Chao -Yu; ...

2015-06-01

Cu xBi 2Se 3 is a superconductor that is a potential candidate for topological superconductors. We report our laser-based angle-resolved photoemission measurement on the electronic structure of the Cu xBi 2Se 3 superconductor, and a detailed magneto-resistance measurement in both normal and superconducting states. We find that the topological surface state of the pristine Bi 2Se 3 topological insulator remains robust after the Cu-intercalation, while the Dirac cone location moves downward due to electron doping. Detailed measurements on the magnetic field-dependence of the resistance in the superconducting state establishes an irreversibility line and gives a value of the upper criticalmore » field at zero temperature of ~4000 Oe for the Cu 0.3Bi 2Se 3 superconductor with a middle point T c of 1.9K. The relation between the upper critical field Hc2 and temperature T is different from the usual scaling relation found in cuprates and in other kinds of superconductors. Small positive magneto-resistance is observed in Cu 0.3Bi 2Se 3 superconductors up to room temperature. As a result, these observations provide useful information for further study of this possible candidate for topological superconductors.« less

Effect of Carbon Dioxide Laser on Increasing Vestibular Depth in Cleft Lip and Palate Patients.

PubMed

Yassaei, Sogra; Aghili, Hossein; Azam, Alireza Navab; Moghadam, Mahjobeh Gholdani; Safari, Isa

2017-09-01

Shallow upper buccal sulcus deformity in cleft lip and palate patients is one of the common secondary deformities after primary cleft lip and palate repair; this deformity may prevent or complicate orthodontic and prosthodontic procedures causing aesthetic and functional problems. A number of methods are described to increase the anterior maxillary sulcus in these patients. This study assessed the use of a carbon dioxide laser (CO 2 ) to increase the sulcus depth. Fifteen patients with cleft lip and palate (eight unilateral and seven bilateral) were studied. The surgical procedure was performed using CO 2 laser. The vestibular depth and lip length were measured at three time points namely before surgery (T0), 1 week following surgery (T1), and 4 months following surgery (T2). After data collection, statistical analyses were done using PASW ® version 18 SPSS. The mean values of vestibular depth were 9.46 ± 1.92, 13.83 ± 1.88, and 13.23 ± 1.76 mm for T0, T1, and T2, respectively. The vestibular depth significantly increased after 4 months of follow-up (p = 0.001). The mean amount of vestibular depth gain was not significantly different in unilateral and bilateral cleft groups (p = 0.908). The mean value of upper lip length increased by a mean of 1.23 mm and was statistically significant (p = 0.001). Upper buccal sulcus reconstruction with CO 2 laser provides successful and stable results. CO 2 laser application is suggested as an alternative to conventional vestibuloplasty.

Lasers in the management of calcified urinary tract stents

NASA Astrophysics Data System (ADS)

Nseyo, Unyime O.; Tunuguntla, Hari S. G. R.; Crone, Michael

2003-06-01

Indwelling double J ureteral stents are used for internal urinary diversion for ureteral obstruction and post-surgical drainage of the upper urinary tract. Stent calcification is a serious complication especially in those with forgotten stents. In a retrospective review of 16 patients (10 male and 6 female) we found holmium laser to be highly effective in the management of calcified stents. Encrustations/calcifications were noted on the distal end of the sent in 6 patiens (37.5%), middle and distal portions in 2 patients (12.5%), along the entire length of the stent in 3 patients (18.75%), lower portion of the stent in 4 patients (25%) and at the upper and lower ends of the stent in one patient (6.25%). Cystolitholapaxy, retrograde ureteroscopy (URS) with holmium: YAG (yttrium-aluminum-garnet) laser intracorporeal lithotripsy, percutaneous nephrostolithotomy (PNL) and antegrade URS with holmium: YAG laser intracorporeal lithotripsy were effectively performed without intraoperative complications. Lithotripsy became necessary before stent removal in 11 patients (68.75%). Holmium laser lithotripsy was useful in managing 7 patients (43.75%), and shockwave lithotripsy (SWL) in 6 patients (37.5%). In two patients (12.5%) both holmium and SWL were used before the stent can be removed.

Current Laser Resurfacing Technologies: A Review that Delves Beneath the Surface

PubMed Central

Preissig, Jason; Hamilton, Kristy; Markus, Ramsey

2012-01-01

Numerous laser platforms exist that rejuvenate the skin by resurfacing its upper layers. In varying degrees, these lasers improve the appearance of lentigines and rhytides, eliminate photoaging, soften scarring due to acne and other causes, and treat dyspigmentation. Five major classes of dermatologic lasers are currently in common use: ablative and nonablative lasers in both fractionated and unfractionated forms as well as radiofrequency technologies. The gentler nonablative lasers allow for quicker healing, whereas harsher ablative lasers tend to be more effective. Fractionating either laser distributes the effect, increasing the number of treatments but minimizing downtime and complications. In this review article, the authors seek to inform surgeons about the current laser platforms available, clarify the differences between them, and thereby facilitate the identification of the most appropriate laser for their practice. PMID:23904818

The observation of ultrafast excited-state dynamical evolution in B800- partially or completely released LH2 of Rhodobacter sphaeroides 601 at room temperature.

PubMed

Liu, Weimin; Liu, Yuan; Yan, Yongli; Liu, Kangjun; Guo, Lijun; Xu, Chunhe; Qian, Shixiong

2006-04-01

Photodynamics of two kinds of peripheral antenna complexes (LH2 of Rhodobacter sphaeroides, native LH2 (RS601) and B800-released LH2 where B800-BChls were partially or completely removed with different pH treatments), were studied using femtosecond pump-probe technique at different laser wavelengths. The obtained results for these samples with different B800/B850 ratios demonstrated that under the excitation around B800 nm, the photoabsorption and photobleaching dynamics were caused by the direct excitation of upper excitonic levels of B850 and excited state of B800 pigments, respectively. Furthermore, the removal of B800 pigments had little effect on the energy transfer processes of B850 interband/intraband transfer.

A simple kinetic model of a Ne-H2 Penning-plasma laser

NASA Astrophysics Data System (ADS)

Petrov, G. M.; Stefanova, M. S.; Pramatarov, P. M.

1995-09-01

A simple kinetic model of the Ne-H2 Penning-Plasma Laser (PPL) (NeI 585.3 nm) is proposed. The negative glow of a hollow cathode discharge at intermediate pressures is considered as the active medium. The balance equations for the upper and lower laser levels, electrons, ions and electron energy are solved. The dependences of the laser gain on the discharge conditions (Ne and H2 partial pressures, discharge current) are calculated and measured. The calculated values are in a good agreement with the experimental data.

The laser-induced fluorescence spectroscopy of TiF in the ultraviolet region

NASA Astrophysics Data System (ADS)

Zhang, Zhaoxia; Guo, Jingru; Yu, Xufeng; Zhen, Junfeng; Chen, Yang

2009-02-01

The laser-induced fluorescence (LIF) spectrum of jet-cooled 48TiF has been obtained in the wavelength region of 245-270 nm for the first time. Six pairs of vibronic bands were observed and assigned to two new transitions [37.8] 4Φ-X 4Φ and 4Δ-X 4Φ. Rotational analysis was carried out for the ( ν' = 0-3 to ν″ = 0) vibrational bands of the [37.8] 4Φ 3/2-X 4Φ 3/2 and [37.8] 4Φ 5/2-X 4Φ 5/2 subbands, and also, the ( ν', 0) and ( ν'+1, 0) vibrational bands of the 4Δ 1/2-X 4Φ 3/2 and 4Δ 3/2-X 4Φ 5/2 subbands. The effective equilibrium molecular constants for the [37.8] 4Φ 3/2 and [37.8] 4Φ 3/2 upper states were determined. In addition, lifetime measurements were carried out for all of the observed bands under collision-free conditions. On the basis of the spectroscopic constants and lifetime measurements, the electronic transitions involved in the observed high-lying electronic states are discussed.

Prevention of pharyngocutaneous fistulas by means of laser-weld techniques.

PubMed

Shohet, J A; Reinisch, L; Ossoff, R H

1995-07-01

Although much has been written on methods of dealing with pharyngocutaneous fistulas once they have formed, there are few reports of methods of preventing fistula formation from occurring. We examined the use of laser-weld techniques with the neodymium:yttrium aluminum garnet (Nd:YAG) and diode lasers to seal pharyngotomy closures. Laser-weld techniques have been used successfully in many other tissues, but reports documenting use in the upper aerodigestive tract are minimal. Indocyanine-green dye-enhanced collagen and fibrinogen were studied as laser solder materials for the diode laser. Twenty-nine experimental animals were studied. Neither the Nd:YAG nor the diode laser was successful in preventing fistula formation. Tensiometric studies documented significant strength of the laser welds ex vivo, but this finding was not clinically significant.

Conductive Channel for Energy Transmission

NASA Astrophysics Data System (ADS)

Apollonov, Victor V.

2011-11-01

For many years the attempts to create conductive channels of big length were taken in order to study the upper atmosphere and to settle special tasks, related to energy transmission. There upon the program of creation of "Impulsar" represents a great interest, as this program in a combination with high-voltage high repetition rate electrical source can be useful to solve the above mentioned problems (N. Tesla ideas for the days of high power lasers). The principle of conductive channel production can be shortly described as follows. The "Impulsar"—laser jet engine vehicle—propulsion take place under the influence of powerful high repetition rate pulse-periodic laser radiation. In the experiments the CO2—laser and solid state Nd:YAG laser systems had been used. Active impulse appears thanks to air breakdown (<30 km) or to the breakdown of ablated material on the board (>30 km), placed in the vicinity of the focusing mirror-acceptor of the breakdown waves. With each pulse of powerful laser the device rises up, leaving a bright and dense trace of products with high degree of ionization and metallization by conductive nano-particles due to ablation. Conductive dust plasma properties investigation in our experiments was produced by two very effective approaches: high power laser controlled ablation and by explosion of wire. Experimental and theoretical results of conductive canal modeling will be presented. The estimations show that with already experimentally demonstrated figures of specific thrust impulse the lower layers of the Ionosphere can be reached in several ten seconds that is enough to keep the high level of channel conductivity and stability with the help of high repetition rate high voltage generator. Some possible applications for new technology are highlighted.

Improved power and efficiency for tapered lasers with optimized photonic crystal structures

NASA Astrophysics Data System (ADS)

Ma, Xiaolong; Qu, Hongwei; Zhao, Shaoyu; Zhou, Xuyan; Lin, Yuzhe; Zheng, Wanhua

2017-10-01

High power and high beam quality laser sources are required in numerous applications such as nonlinear frequency conversion, optical pumping of solid-state and fiber lasers, material processing and others. Tapered lasers can provide a high output power while keeping a high beam quality. However, the conventional tapered lasers suffer from a large vertical beam divergence. We have demonstrated 2-mm long tapered lasers with photonic crystal structures. A high beam quality and a narrow vertical divergence are achieved. In this paper, we optimized the photonic crystal structure and fabricated a 4-mm long tapered laser to further increase the output power and the wall-plug efficiency. Compared with our precious wafer, the optimized structure has a lower doping level to reduce the internal loss. The period of the photonic crystal structure and the thickness of the upper cladding are also reduced. The device has a 1-mm long ridge-waveguide section and a 3-mm long tapered section. The taper angle is 4°. An output power of 7.3 W is achieved with a peak wall-plug efficiency of 46% in continuous-wave mode. The threshold current is around 500 mA and the slope efficiency is 0.93 W/A. In pulsed mode, the output power is 15.6 W and the maximum wall-plug efficiency is 48.1%. The far-field divergence with full width at half maximum is 6.3° for the lateral direction at 3 A. The vertical far-field beam divergence is around 11° at different injection levels. High beam qualities are demonstrated by beam quality factor M2 of 1.52 for the lateral direction and 1.54 for the vertical direction.

CEO stabilization of a femtosecond laser using a SESAM as fast opto-optical modulator.

PubMed

Hoffmann, Martin; Schilt, Stéphane; Südmeyer, Thomas

2013-12-02

We present a new method for intra-cavity control of the carrier-envelope offset (CEO) frequency of ultrafast lasers that combines high feedback bandwidth with low loss, low nonlinearity, and low dispersion. A semiconductor saturable-absorber mirror (SESAM) inside a modelocked laser is optically pumped with a continuous-wave (cw) laser. In this way, the SESAM acts as intra-cavity opto-optical modulator (OOM): the optical power of the cw-laser corresponds to a high-bandwidth modulation channel for CEO frequency control. We experimentally verified this method for a femtosecond Er:Yb:glass oscillator (ERGO), in which one SESAM is in parallel used for modelocking and as intra-cavity OOM for achieving a tight CEO lock. This laser can also be CEO-stabilized in the usual scheme, in which the laser pump current is modulated, i.e., the gain element acts as intra-cavity OOM. We compare the performance with gain and SESAM OOM measuring CEO transfer function, frequency noise power spectral density (PSD), and Allan deviation for integration times up to 1000 s. In the case of the gain OOM, the millisecond upper-state lifetime of the Er:Yb:glass limits the achievable CEO-control bandwidth to <10 kHz. The feedback bandwidth of the SESAM OOM was more than a factor of 10 higher than the gain OOM bandwidth and was mainly limited by the used current driver. The residual integrated phase noise (1 Hz - 100 kHz) of the ~20-MHz CEO beat was improved by more than an order of magnitude (from 720 mrad to less than 65 mrad), and the fractional frequency stability by a factor of 4 (from 1∙10

Interband optical pulse injection locking of quantum dot mode-locked semiconductor laser.

PubMed

Kim, Jimyung; Delfyett, Peter J

2008-07-21

We experimentally demonstrate optical clock recovery from quantum dot mode-locked semiconductor lasers by interband optical pulse injection locking. The passively mode-locked slave laser oscillating on the ground state or the first excited state transition is locked through the injection of optical pulses generated via the opposite transition bands, i.e. the first excited state or the ground state transition from the hybridly mode-locked master laser, respectively. When an optical pulse train generated via the first excited state from the master laser is injected to the slave laser oscillating via ground state, the slave laser shows an asymmetric locking bandwidth around the nominal repetition rate of the slave laser. In the reverse injection case of, i.e. the ground state (master laser) to the first excited state (slave laser), the slave laser does not lock even though both lasers oscillate at the same cavity frequency. In this case, the slave laser only locks to higher injection rates as compared to its own nominal repetition rate, and also shows a large locking bandwidth of 6.7 MHz.

Nitride-based stacked laser diodes with a tunnel junction

NASA Astrophysics Data System (ADS)

Okawara, Satoru; Aoki, Yuta; Kuwabara, Masakazu; Takagi, Yasufumi; Maeda, Junya; Yoshida, Harumasa

2018-01-01

We report on nitride-based two-stack laser diodes with a tunnel junction for the first time. The stacked laser diode was monolithically grown by metalorganic vapor phase epitaxy. It was confirmed that the two-stack InGaN/GaN multiple-quantum-well laser diode with an emission wavelength of 394 nm exhibited laser oscillation up to a peak output power of over 10 W in the pulsed current mode. The upper and lower emitters of the device were capable of lasing at different threshold currents of 2.4 and 5.2 A with different slope efficiencies of 0.8 and 0.3 W/A, respectively.

[The frequency-doubled double-pulse Neodym:YAG laser lithotripter (FREDDY) in lithotripsy of urinary stones. First clinical experience].

PubMed

Ebert, A; Stangl, J; Kühn, R; Schafhauser, W

2003-06-01

Laser lithotripsy does not play an important role in urinary stone treatment, mostly due to ineffective fragmentation efficiency, and high purchase and maintenance costs. The aim of the following retrospective study was to show the clinical significance and efficiency of an innovative laser lithotripsy system for urinary stone treatment. Between November 1998 and October 1999, 48 patients were treated with the innovative frequency- doubled double-pulse Neodym: YAG laser lithotripter FREDDY. A total of 50 renal units were treated, 43 ureteroscopically, four ureterorenoscopically, three percutaneous-nephroscopically, and one bladder stone cystoscopically. With a median laser operation time of 5 min (range: 1-30 min) and a total procedure duration of 60 min (range: 15-180 min), a stone-free rate of upper ureteral stones of 62%, middle ureteral stones of 91% and distal ureteral stones of 100% were documented on the first day after treatment. In an observation period of 6 months, no complications were seen. In our experience Laser lithotripsy with FREDDY is an effective, simple and reliable method for the treatment of ureteral stones, with low purchase and maintenance costs. The extremely thin and highly flexible quartz fibre may extend the endoscopic spectrum to otherwise poorly accessible upper ureteral stones, the renal pelvis and renal calix stones. Therefore, a prospective validation study for comparison with ballistic lithotriptors is of great interest.

Tunable solid state lasers for remote sensing; Proceedings of the Conference, Stanford University, CA, October 1-3, 1984

NASA Technical Reports Server (NTRS)

Byer, R. L. (Editor); Trebino, R. (Editor); Gustafson, E. K. (Editor)

1985-01-01

Papers are presented on solid-state lasers for remote sensing, diode-pumped Nd:YAG lasers, and tunable solid-state-laser systems. Topics discussed include titanium-sapphire tunable laser systems, the performance of slab geometry, and the development of slab lasers. Consideration is given to garnet host solid-state lasers, the growth of lasers and nonlinear materials, and nonlinear frequency conversion and tunable sources.

Lithotripsy

MedlinePlus

... Laser lithotripsy; Percutaneous lithotripsy; Endoscopic lithotripsy; ESWL; Renal calculi-lithotripsy ... Lingeman JE. Surgical management of upper urinary tract calculi. In: Wein AJ, Kavoussi LR, Partin AW, Peters ...

Aircraft laser sensing of sound velocity in water - Brillouin scattering

NASA Technical Reports Server (NTRS)

Hickman, G. D.; Harding, John M.; Carnes, Michael; Pressman, AL; Kattawar, George W.; Fry, Edward S.

1991-01-01

A real-time data source for sound speed in the upper 100 m has been proposed for exploratory development. This data source is planned to be generated via a ship- or aircraft-mounted optical pulsed laser using the spontaneous Brillouin scattering technique. The system should be capable (from a single 10 ns 500 mJ pulse) of yielding range resolved sound speed profiles in water to depths of 75-100 m to an accuracy of 1 m/s. The 100 m profiles will provide the capability of rapidly monitoring the upper-ocean vertical structure. They will also provide an extensive, subsurface-data source for existing real-time, operational ocean nowcast/forecast systems.

Resonant intersubband polariton-LO phonon scattering in an optically pumped polaritonic device

NASA Astrophysics Data System (ADS)

Manceau, J.-M.; Tran, N.-L.; Biasiol, G.; Laurent, T.; Sagnes, I.; Beaudoin, G.; De Liberato, S.; Carusotto, I.; Colombelli, R.

2018-05-01

We report experimental evidence of longitudinal optical (LO) phonon-intersubband polariton scattering processes under resonant injection of light. The scattering process is resonant with both the initial (upper polariton) and final (lower polariton) states and is induced by the interaction of confined electrons with longitudinal optical phonons. The system is optically pumped with a mid-IR laser tuned between 1094 cm-1 and 1134 cm-1 (λ = 9.14 μm and λ = 8.82 μm). The demonstration is provided for both GaAs/AlGaAs and InGaAs/AlInAs doped quantum well systems whose intersubband plasmon lies at a wavelength of ≈10 μm. In addition to elucidating the microscopic mechanism of the polariton-phonon scattering, it is found to differ substantially from the standard single particle electron-LO phonon scattering mechanism, and this work constitutes an important step towards the hopefully forthcoming demonstration of an intersubband polariton laser.

Room temperature negative differential resistance in terahertz quantum cascade laser structures

DOE PAGES

Albo, Asaf; Hu, Qing; Reno, John L.

2016-08-24

The mechanisms that limit the temperature performance of GaAs/Al 0.15GaAs-based terahertz quantum cascade lasers (THz-QCLs) have been identified as thermally activated LO-phonon scattering and leakage of charge carriers into the continuum. Consequently, the combination of highly diagonal optical transition and higher barriers should significantly reduce the adverse effects of both mechanisms and lead to improved temperature performance. Here, we study the temperature performance of highly diagonal THz-QCLs with high barriers. Our analysis uncovers an additional leakage channel which is the thermal excitation of carriers into bounded higher energy levels, rather than the escape into the continuum. Based on this understanding,more » we have designed a structure with an increased intersubband spacing between the upper lasing level and excited states in a highly diagonal THz-QCL, which exhibits negative differential resistance even at room temperature. Furthermore, this result is a strong evidence for the effective suppression of the aforementioned leakage channel.« less

980 nm diode lasers in oral and facial practice: current state of the science and art.

PubMed

Desiate, Apollonia; Cantore, Stefania; Tullo, Domenica; Profeta, Giovanni; Grassi, Felice Roberto; Ballini, Andrea

2009-11-24

To evaluate the safety and efficacy of a 980 nm diode laser for the treatment of benign facial pigmented and vascular lesions, and in oral surgery. 20 patients were treated with a 980 nm diode laser. Oral surgery: 5 patients (5 upper and lower frenulectomy). Fluence levels were 5-15 J/cm(2); pulse lengths were 20-60 ms; spot size was 1 mm. Vascular lesions: 10 patients (5 small angiomas, 5 telangiectases). Fluences were 6-10 J/cm(2); pulse lengths were 10-50 ms; spot size was 2 mm. In all cases the areas surrounding the lesions were cooled. Pigmented lesions: 5 patients (5 keratoses). All the lesions were evaluated by dermatoscopy before the treatment. Fluence levels were 7-15 J/cm(2); pulse lengths were 20-50 ms; spot size was 1 mm. All the patients were followed at 1, 4 and 8 weeks after the procedure. Healing in oral surgery was within 10 days. The melanoses healed completely within four weeks. All the vascular lesions healed after 15 days without any residual scarring. The end results for the use of the 980 nm diode laser in oral and facial surgery appears to be justified on the grounds of efficacy and safety of the device, and good degree of acceptance by the patients, without compromising their health and function.

Explosive laser

DOEpatents

Robinson, C.P.; Jensen, R.J.; Davis, W.C.; Sullivan, J.A.

1975-09-01

This patent relates to a laser system wherein reaction products from the detonation of a condensed explosive expand to form a gaseous medium with low translational temperature but high vibration population. Thermal pumping of the upper laser level and de-excitation of the lower laser level occur during the expansion, resulting in a population inversion. The expansion may be free or through a nozzle as in a gas-dynamic configuration. In one preferred embodiment, the explosive is such that its reaction products are CO$sub 2$ and other species that are beneficial or at least benign to CO$sub 2$ lasing. (auth)

[Microcirculatory blood and lymph flow examination in eyelid skin by laser Doppler flowmetry].

PubMed

Safonova, T N; Kintyukhina, N P; Sidorov, V V; Gladkova, O V; Reyn, E S

to study normal blood and lymph microcirculation of the upper and lower eyelids in different age groups. The study included 108 volunteers (216 eyes) aged from 20 to 80 years with no signs of changes in anterior segment structures, who were grouped by age ranges (20-30 years, 31-40 years, 41-50 years, 51-60 years, 61-70 years, and 71-80 years) into 6 groups equal in gender and quantitative composition. In all volunteers, microcirculation of the upper and lower eyelids was examined by laser Doppler flowmetry (LDF) ('LASMA MC-1' peripheral blood and lymph flow analyzer and 'LASMA MC' laser diagnostic complex, LASMA LLC). The average perfusion changes in blood and lymph flow as well as blood and lymph flow oscillations were analyzed. Blood and lymph flow in the microvasculature of the upper and lower eyelids is variable and depends on neither the age, nor gender of the test subject. On LDF-gram, every increase in amplitude of blood flow corresponds to a decrease in that of lymph flow. The non-invasive method of LDF expands our diagnostic capabilities as it enables assessment of not only blood, but also lymph flow. The data obtained can serve as a starting point for exploring microcirculation in different age groups in the presence of different pathological processes.

Characterization of particle deformation during compression measured by confocal laser scanning microscopy.

PubMed

Guo, H X; Heinämäki, J; Yliruusi, J

1999-09-20

Direct compression of riboflavin sodium phosphate tablets was studied by confocal laser scanning microscopy (CLSM). The technique is non-invasive and generates three-dimensional (3D) images. Tablets of 1% riboflavin sodium phosphate with two grades of microcrystalline cellulose (MCC) were individually compressed at compression forces of 1.0 and 26.8 kN. The behaviour and deformation of drug particles on the upper and lower surfaces of the tablets were studied under compression forces. Even at the lower compression force, distinct recrystallized areas in the riboflavin sodium phosphate particles were observed in both Avicel PH-101 and Avicel PH-102 tablets. At the higher compression force, the recrystallization of riboflavin sodium phosphate was more extensive on the upper surface of the Avicel PH-102 tablet than the Avicel PH-101 tablet. The plastic deformation properties of both MCC grades reduced the fragmentation of riboflavin sodium phosphate particles. When compressed with MCC, riboflavin sodium phosphate behaved as a plastic material. The riboflavin sodium phosphate particles were more tightly bound on the upper surface of the tablet than on the lower surface, and this could also be clearly distinguished by CLSM. Drug deformation could not be visualized by other techniques. Confocal laser scanning microscopy provides valuable information on the internal mechanisms of direct compression of tablets.

Fluorescence kinetics of emission from a small finite volume of a biological system

NASA Astrophysics Data System (ADS)

Dagen, A. J.; Alfano, R. R.; Zilinskas, B. A.; Swenberg, C. E.

1985-07-01

The fluorescence decay, apparent quantum yield and transmission from chromophores constrained to a microscopic volume using a single picosecond laser excitation were measured as a function of incident intensity. The β subunit of phycoeryhthrin aggregate isolated from the photosynthetic antenna system of Nostoc sp. was selected since it contains only four chromophores in a volume of less than 5.6×10 4 Å 3. The non-exponential fluorescence decay profiles were intensity independent for the intensity range studied (5 × 10 13 - 2 × 10 15 photon cm -2 per pulse). The apparent decrease in the relative fluorescence quantum yield and increase of the relative transmission with increasing excitation intensity is attributed to the combined effects of ground state depletion and upper excited state absorption. Evidence suggests that exciton annihilation is absent within isolated β subunits.

Quantum heat engine power can be increased by noise-induced coherence

PubMed Central

Scully, Marlan O.; Chapin, Kimberly R.; Dorfman, Konstantin E.; Kim, Moochan Barnabas; Svidzinsky, Anatoly

2011-01-01

Laser and photocell quantum heat engines (QHEs) are powered by thermal light and governed by the laws of quantum thermodynamics. To appreciate the deep connection between quantum mechanics and thermodynamics we need only recall that in 1901 Planck introduced the quantum of action to calculate the entropy of thermal light, and in 1905 Einstein’s studies of the entropy of thermal light led him to introduce the photon. Then in 1917, he discovered stimulated emission by using detailed balance arguments. Half a century later, Scovil and Schulz-DuBois applied detailed balance ideas to show that maser photons were produced with Carnot quantum efficiency (see Fig. 1A). Furthermore, Shockley and Quiesser invoked detailed balance to obtain the efficiency of a photocell illuminated by “hot” thermal light (see Fig. 2A). To understand this detailed balance limit, we note that in the QHE, the incident light excites electrons, which can then deliver useful work to a load. However, the efficiency is limited by radiative recombination in which the excited electrons are returned to the ground state. But it has been proven that radiatively induced quantum coherence can break detailed balance and yield lasing without inversion. Here we show that noise-induced coherence enables us to break detailed balance and get more power out of a laser or photocell QHE. Surprisingly, this coherence can be induced by the same noisy (thermal) emission and absorption processes that drive the QHE (see Fig. 3A). Furthermore, this noise-induced coherence can be robust against environmental decoherence.Fig. 1.(A) Schematic of a laser pumped by hot photons at temperature Th (energy source, blue) and by cold photons at temperature Tc (entropy sink, red). The laser emits photons (green) such that at threshold the laser photon energy and pump photon energy is related by Carnot efficiency (4). (B) Schematic of atoms inside the cavity. Lower level b is coupled to the excited states a and β. The laser power is governed by the average number of hot and cold thermal photons, and . (C) Same as B but lower b level is replaced by two states b1 and b2, which can double the power when there is coherence between the levels.Fig. 2.(A) Schematic of a photocell consisting of quantum dots sandwiched between p and n doped semiconductors. Open circuit voltage and solar photon energy ℏνh are related by the Carnot efficiency factor where Tc is the ambient and Th is the solar temperature. (B) Schematic of a quantum dot solar cell in which state b is coupled to a via, e.g., solar radiation and coupled to the valence band reservoir state β via optical phonons. The electrons in conduction band reservoir state α pass to state β via an external circuit, which contains the load. (C) Same as B but lower level b is replaced by two states b1 and b2, and when coherently prepared can double the output power.Fig. 3.(A) Photocell current j = Γραα (laser photon flux Pl/ℏνl) (in arbitrary units) generated by the photovoltaic cell QHE (laser QHE) of Fig. 1C (Fig. 2C) as a function of maximum work (in electron volts) done by electron (laser photon) Eα - Eβ + kTc log(ραα/ρββ) with full (red line), partial (brown line), and no quantum interference (blue line). (B) Power of a photocell of Fig. 2C as a function of voltage for different decoherence rates , 100γ1c. Upper curve indicates power acquired from the sun. PMID:21876187

Quantum heat engine power can be increased by noise-induced coherence.

PubMed

Scully, Marlan O; Chapin, Kimberly R; Dorfman, Konstantin E; Kim, Moochan Barnabas; Svidzinsky, Anatoly

2011-09-13

Laser and photocell quantum heat engines (QHEs) are powered by thermal light and governed by the laws of quantum thermodynamics. To appreciate the deep connection between quantum mechanics and thermodynamics we need only recall that in 1901 Planck introduced the quantum of action to calculate the entropy of thermal light, and in 1905 Einstein's studies of the entropy of thermal light led him to introduce the photon. Then in 1917, he discovered stimulated emission by using detailed balance arguments. Half a century later, Scovil and Schulz-DuBois applied detailed balance ideas to show that maser photons were produced with Carnot quantum efficiency (see Fig. 1A). Furthermore, Shockley and Quiesser invoked detailed balance to obtain the efficiency of a photocell illuminated by "hot" thermal light (see Fig. 2A). To understand this detailed balance limit, we note that in the QHE, the incident light excites electrons, which can then deliver useful work to a load. However, the efficiency is limited by radiative recombination in which the excited electrons are returned to the ground state. But it has been proven that radiatively induced quantum coherence can break detailed balance and yield lasing without inversion. Here we show that noise-induced coherence enables us to break detailed balance and get more power out of a laser or photocell QHE. Surprisingly, this coherence can be induced by the same noisy (thermal) emission and absorption processes that drive the QHE (see Fig. 3A). Furthermore, this noise-induced coherence can be robust against environmental decoherence.Fig. 1.(A) Schematic of a laser pumped by hot photons at temperature T(h) (energy source, blue) and by cold photons at temperature T(c) (entropy sink, red). The laser emits photons (green) such that at threshold the laser photon energy and pump photon energy is related by Carnot efficiency (4). (B) Schematic of atoms inside the cavity. Lower level b is coupled to the excited states a and β. The laser power is governed by the average number of hot and cold thermal photons, and . (C) Same as B but lower b level is replaced by two states b(1) and b(2), which can double the power when there is coherence between the levels.Fig. 2.(A) Schematic of a photocell consisting of quantum dots sandwiched between p and n doped semiconductors. Open circuit voltage and solar photon energy ℏν(h) are related by the Carnot efficiency factor where T(c) is the ambient and T(h) is the solar temperature. (B) Schematic of a quantum dot solar cell in which state b is coupled to a via, e.g., solar radiation and coupled to the valence band reservoir state β via optical phonons. The electrons in conduction band reservoir state α pass to state β via an external circuit, which contains the load. (C) Same as B but lower level b is replaced by two states b(1) and b(2), and when coherently prepared can double the output power.Fig. 3.(A) Photocell current j = Γρ(αα) (laser photon flux P(l)/ℏ(ν(l))) (in arbitrary units) generated by the photovoltaic cell QHE (laser QHE) of Fig. 1C (Fig. 2C) as a function of maximum work (in electron volts) done by electron (laser photon) E(α) - E(β) + kT(c) log(ρ(αα)/ρ(ββ)) with full (red line), partial (brown line), and no quantum interference (blue line). (B) Power of a photocell of Fig. 2C as a function of voltage for different decoherence rates , 100γ(1c). Upper curve indicates power acquired from the sun.

The evolution of lasers in urology

PubMed Central

Zarrabi, Amir; Gross, Andreas J.

2011-01-01

The world’s first laser was developed by Theodore Maiman in 1960. Over the course of the past five decades, this technology has evolved into a highly specialized entity, also finding a niche market in the field of urology. Lasers obtained from various lasing mediums producing amplified light of different wavelengths have been tested for urological applications. Today, these lasers are most commonly used in the surgical management of benign prostatic hyperplasia and as intracorporeal lithotripters. Other uses include ablation of various urologic tumors and incising strictures of the upper- and lower urinary tract. A continuous process of evolution of this technology is taking place, resulting in surgical lasers becoming ever safer, more effective, and more affordable. PMID:21869908

Multi-temporal UAV-borne LiDAR point clouds for vegetation analysis - a case study

NASA Astrophysics Data System (ADS)

Mandlburger, Gottfried; Wieser, Martin; Hollaus, Markus; Pfennigbauer, Martin; Riegl, Ursula

2016-04-01

In the recent past the introduction of compact and lightweight LiDAR (Light Detection And Ranging) sensors together with progress in UAV (Unmanned Aerial Vehicle) technology allowed the integration of laser scanners on remotely piloted multicopter, helicopter-type and even fixed-wing platforms. The multi-target capabilities of state-of-the-art time-of-flight full-waveform laser sensors operated from low flying UAV-platforms has enabled capturing of the entire 3D structure of semi-transparent objects like deciduous forests under leaf-off conditions in unprecedented density and completeness. For such environments it has already been demonstrated that UAV-borne laser scanning combines the advantages of terrestrial laser scanning (high point density, short range) and airborne laser scanning (bird's eye perspective, homogeneous point distribution). Especially the oblique looking capabilities of scanners with a large field of view (>180°) enable capturing of vegetation from different sides resulting in a constantly high point density also in the sub canopy domain. Whereas the findings stated above were drawn based on a case study carried out in February 2015 with the Riegl VUX-1UAV laser scanner system mounted on a Riegl RiCopter octocopter UAV-platform over an alluvial forest at the Pielach River (Lower Austria), the site was captured a second time with the same sensor system and mission parameters at the end of the vegetation period on October 28th, 2015. The main goal of this experiment was to assess the impact of the late autumn foliage on the achievable 3D point density. Especially the entire understory vegetation and certain tree species (e.g. willow) were still in full leaf whereas the bigger trees (poplar) where already partly defoliated. The comparison revealed that, although both campaigns featured virtually the same laser shot count, the ground point density dropped from 517 points/m2 in February (leaf-off) to 267 points/m2 end of October (leaf-on). The decrease of ca. 50% is compensated by an increase in the upper canopy area (>20 m a.g.l.; Feb: 348 points/m2, Oct: 757 points/m2, increase rate: 118%). The greater leaf area in October results in more laser echoes from the canopy but the density decrease on the ground is not entirely attributed to shadowing from the upper canopy as the point distribution is nearly constant in the medium (10-20 m) and lower (0-10 m) sub-canopy area. The lower density on the ground is rather caused by a densely foliated shrub layer (0.15-3 m; Feb: 178 points/m2, Oct: 259 points/m2, increase rate: 46%). A sharp ground point density drop could be observed in areas covered by an invasive weed species (Fallopia japonica) which keeps its extremely dense foliage till late in the year. In summary, the preliminary point density study has shown the potential of UAV-borne, multi-temporal LiDAR for characterization of seasonal vegetation changes in deciduous environments. It is remarkable that even under leaf-on conditions a very high terrain point density is achievable. Except for the dense shrub layer, the case study has shown a similar 3D point distribution in the sub-canopy area for leaf-off and leaf-on data acquisition.

Diode pumped solid-state laser oscillators for spectroscopic applications

NASA Technical Reports Server (NTRS)

Byer, R. L.; Basu, S.; Fan, T. Y.; Kozlovsky, W. J.; Nabors, C. D.; Nilsson, A.; Huber, G.

1987-01-01

The rapid improvement in diode laser pump sources has led to the recent progress in diode laser pumped solid state lasers. To date, electrical efficiencies of greater than 10 percent were demonstrated. As diode laser costs decrease with increased production volume, diode laser and diode laser array pumped solid state lasers will replace the traditional flashlamp pumped Nd:YAG laser sources. The use of laser diode array pumping of slab geometry lasers will allow efficient, high peak and average power solid state laser sources to be developed. Perhaps the greatest impact of diode laser pumped solid state lasers will be in spectroscopic applications of miniature, monolithic devices. Single-stripe diode-pumped operation of a continuous-wave 946 nm Nd:YAG laser with less than 10 m/w threshold was demonstrated. A slope efficiency of 16 percent near threshold was shown with a projected slope efficiency well above a threshold of 34 percent based on results under Rhodamine 6G dye-laser pumping. Nonlinear crystals for second-harmonic generation of this source were evaluated. The KNbO3 and periodically poled LiNbO3 appear to be the most promising.

Development and validation of a microchip pulsed laser for ESA space altimeters

NASA Astrophysics Data System (ADS)

Couto, Bruno; Abreu, Hernâni; Gordo, Paulo; Amorim, António

2016-10-01

The development and validation of small size laser sources for space based range finding is of crucial importance to the development of miniature LIDAR devices for European space missions, particularly for planet lander probes. In this context, CENTRA-SIM is developing a passively q-switched microchip laser in the 1.5μm wavelength range. Pulses in the order of 2 ns and 100μJ were found to be suitable for range finding for small landing platforms. Both glass and crystalline Yb-Er doped active media are commonly available. Crystalline media present higher thermal conductivity and hardness, which allows for higher pumping intensities. However, glass laser media present longer laser upper-state lifetime and 99% Yb-Er transfer efficiency make phosphate glasses the typically preferred host for this type of application. In addition to this, passively q-switched microchip lasers with Yb-Er doped phosphate glass have been reported to output >100μJ pulses while their crystalline host counterparts achieve a few tens of μJ at best. Two different types of rate equation models have been found: microscopic quantities based models and macroscopic quantities based models. Based on the works of Zolotovskaya et al. and Spühler et al, we have developed a computer model that further exploits the equivalence between the two types of approaches. The simulation studies, using commercial available components allowed us to design a compact laser emitting 80μJ pulses with up to 30kW peak power and 1 to 2 ns pulse width. We considered EAT14 Yb-Er doped glass as active medium and Co2+:MgAl2O4 as saturable absorber. The active medium is pumped by a 975nm semiconductor laser focused into a 200μm spot. Measurements on an experimental test bench to validate the numerical model were carried out. Several different combinations of, saturable absorber length and output coupling were experimented.

Advances in solid state laser technology for space and medical applications

NASA Technical Reports Server (NTRS)

Byvik, C. E.; Buoncristiani, A. M.

1988-01-01

Recent developments in laser technology and their potential for medical applications are discussed. Gas discharge lasers, dye lasers, excimer lasers, Nd:YAG lasers, HF and DF lasers, and other commonly used lasers are briefly addressed. Emerging laser technology is examined, including diode-pumped lasers and other solid state lasers.

Low charge state heavy ion production with sub-nanosecond laser.

PubMed

Kanesue, T; Kumaki, M; Ikeda, S; Okamura, M

2016-02-01

We have investigated laser ablation plasma of various species using nanosecond and sub-nanosecond lasers for both high and low charge state ion productions. We found that with sub-nanosecond laser, the generated plasma has a long tail which has low charge state ions determined by an electrostatic ion analyzer even under the laser irradiation condition for highly charged ion production. This can be caused by insufficient laser absorption in plasma plume. This property might be suitable for low charge state ion production. We used a nanosecond laser and a sub-nanosecond laser for low charge state ion production to investigate the difference of generated plasma using the Zirconium target.

Low charge state heavy ion production with sub-nanosecond laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kanesue, T., E-mail: tkanesue@bnl.gov; Okamura, M.; Kumaki, M.

2016-02-15

We have investigated laser ablation plasma of various species using nanosecond and sub-nanosecond lasers for both high and low charge state ion productions. We found that with sub-nanosecond laser, the generated plasma has a long tail which has low charge state ions determined by an electrostatic ion analyzer even under the laser irradiation condition for highly charged ion production. This can be caused by insufficient laser absorption in plasma plume. This property might be suitable for low charge state ion production. We used a nanosecond laser and a sub-nanosecond laser for low charge state ion production to investigate the differencemore » of generated plasma using the Zirconium target.« less

Diode laser heterodyne observations of silicon monoxide in sunspots - A test of three sunspot models

NASA Technical Reports Server (NTRS)

Glenar, D. A.; Deming, D.; Jennings, D. E.; Kostiuk, T.; Mumma, M. J.

1983-01-01

Absorption features from the 8 micron SiO fundamental (upsilon = 1-0) and hot bands (upsilon = 2-1) have been observed in sunspots at sub-Doppler resolution using a ground-based tunable diode laser heterodyne spectrometer. The observed line widths suggest an upper limit of 0.5 km/s for the microturbulent velocity in sunspot umbrae. Since the silicon monoxide abundance is very sensitive to sunspot temperature, the measured equivalent widths permit an unambiguous determination of the temperature-pressure relation in the upper layers of the umbral atmosphere. In the region of SiO line formation (log P sub g = 3.0-4.5), the results support the sunspot model suggested by Stellmacher and Wiehr (1970).

On the possibility of developing quasi-CW high-power high-pressure laser on 4p-4s transition of ArI with electron beam—optical pumping: quenching of 4s (3P2) lower laser level

NASA Astrophysics Data System (ADS)

Ionin, A. A.; Kholin, I. V.; L'dov, A. Yu; Seleznev, L. V.; Ustinovskii, N. N.; Zayarnyi, D. A.

2017-12-01

A new electron beam-optical procedure is proposed for quasi-cw pumping of high-pressure large-volume He-Ar laser on the 4p[1/2]1-4s[3/2]20 argon atom transition at the wavelength of 912.5 nm. It consists of creation and maintenance of a necessary density of the 4s[3/2]20 metastable state in the gain medium by a fast electron beam and subsequent optical pumping of the upper laser level via the classical three-level scheme using a laser diode. Absorption probing is used to study collisional quenching of Ar* metastable in electron-beam-excited high-pressure He-Ar mixtures with a low content of argon. The rate constants for plasma-chemical reactions Ar*  +  He  +  Ar  >  Ar2*   +  He (3.6  ±  0.4)  ×  10-33 cm6 s-1, Ar*  +  2He  >  HeAr*  +  He (4.4  ±  0.9)  ×  10-36 cm6 s-1 and Ar*  +  He  >  Products  +  He (2.4  ±  0.3)  ×  10-15 cm3 s-1 were for the first time measured.

INTERNATIONAL CONFERENCE ON SEMICONDUCTOR INJECTION LASERS SELCO-87: Relationship between the p-n junction position and the threshold current of stripe lasers emitting in the 1.3-μm range

NASA Astrophysics Data System (ADS)

Walachová, J.; Zelinka, J.

1988-11-01

The method of profiling with a probe was used to determine the p-n junction position in the active layer InP/GaInAsP double heterostructure lasers designed for operation in the region of 1.3 μm. Double heterostructures with different Zn concentrations in the upper GaInAsP layer were investigated. An explanation was provided of the shift or lack of shift of the p-n junction in different heterostructure lasers. The average threshold current was correlated with the p-n junction position.

50-mJ, 1-kHz Yb:YAG thin-disk regenerative amplifier with 969-nm pulsed pumping

NASA Astrophysics Data System (ADS)

Chyla, Michal; Miura, Taisuke; Smrž, Martin; Severova, Patricie; Novak, Ondrej; Endo, Akira; Mocek, Tomas

2014-02-01

We are developing a 100-mJ Yb:YAG thin-disk regenerative amplifier operating at 1-kHz repetition rate pumped at zero-phonon-line (968.825-nm1) and delivering 1-2 ps pulses for EUV plasma sources applicable in science and industry. Recently we achieved the output energy of nearly 50-mJ from a single laser-head cavity with good beam quality (M2<1.2) as well as stable beam-pointing (<4μrad). Applying pulsed pumping with the pulse duration shorter than the upper state lifetime of Yb:YAG helps to reduce the ASE and thermal loading of the thin-disk.

Proposal of laser-driven automobile

NASA Astrophysics Data System (ADS)

Yabe, Takashi; Oozono, Hirokazu; Taniguchi, Kazumoto; Ohkubo, Tomomasa; Miyazaki, Sho; Uchida, Shigeaki; Baasandash, Choijil

2004-09-01

We propose an automobile driven by piston motion, which is driven by water-laser coupling. The automobile can load a solar-pumped fiber laser or can be driven by ground-based lasers. The vehicle is much useful for the use in other planet in which usual combustion engine cannot be used. The piston is in a closed system and then the water will not be exhausted into vacuum. In the preliminary experiment, we succeeded to drive the cylindrical piston of 0.2g (6mm in diameter) on top of water placed inside the acrylic pipe of 8 mm in inner diameter and the laser is incident from the bottom and focused onto the upper part of water by the lens (f=8mm) attached to the bottom edge.

Lidar investigations of ozone in the upper troposphere - lower stratosphere: technique and results of measurements

NASA Astrophysics Data System (ADS)

Romanovskii, Oleg A.; Nevzorov, Alexey A.; Nevzorov, Alexey V.; Kharchenko, Olga V.

2018-04-01

The main aim of the research is to develop the technique for laser remote ozone sensing in the upper troposphere - lower stratosphere by differential absorption method for temperature and aerosol correction and analysis of measurement results. The authors have determined wavelengths, promising to measure ozone profiles in the upper troposphere - lower stratosphere. We present the results of DIAL measurements of the vertical ozone distribution at the Siberian lidar station in Tomsk. The recovered ozone profiles were compared with IASI satellite data and Kruger model.

Ab initio multiple spawning dynamics study of dimethylnitramine and dimethylnitramine-Fe complex to model their ultrafast nonadiabatic chemistry

NASA Astrophysics Data System (ADS)

Bera, Anupam; Ghosh, Jayanta; Bhattacharya, Atanu

2017-07-01

Conical intersections are now firmly established to be the key features in the excited electronic state processes of polyatomic energetic molecules. In the present work, we have explored conical intersection-mediated nonadiabatic chemical dynamics of a simple analogue nitramine molecule, dimethylnitramine (DMNA, containing one N-NO2 energetic group), and its complex with an iron atom (DMNA-Fe). For this task, we have used the ab initio multiple spawning (AIMS) dynamics simulation at the state averaged-complete active space self-consistent field(8,5)/6-31G(d) level of theory. We have found that DMNA relaxes back to the ground (S0) state following electronic excitation to the S1 excited state [which is an (n,π*) excited state] with a time constant of approximately 40 fs. This AIMS result is in very good agreement with the previous surface hopping-result and femtosecond laser spectroscopy result. DMNA does not dissociate during this fast internal conversion from the S1 to the S0 state. DMNA-Fe also undergoes extremely fast relaxation from the upper S1 state to the S0 state; however, this relaxation pathway is dissociative in nature. DMNA-Fe undergoes initial Fe-O, N-O, and N-N bond dissociations during relaxation from the upper S1 state to the ground S0 state through the respective conical intersection. The AIMS simulation reveals the branching ratio of these three channels as N-N:Fe-O:N-O = 6:3:1 (based on 100 independent simulations). Furthermore, the AIMS simulation reveals that the Fe-O bond dissociation channel exhibits the fastest (time constant 24 fs) relaxation, while the N-N bond dissociation pathway features the slowest (time constant 128 fs) relaxation. An intermediate time constant (30 fs) is found for the N-O bond dissociation channel. This is the first nonadiabatic chemical dynamics study of metal-contained energetic molecules through conical intersections.

Holmium:YAG laser lithotripsy for upper urinary tract calculi in 598 patients.

PubMed

Sofer, Mario; Watterson, James D; Wollin, Timothy A; Nott, Linda; Razvi, Hassan; Denstedt, John D

2002-01-01

We assessed the effectiveness and safety of holmium:YAG laser lithotripsy for managing upper urinary tract calculi in a prospective cohort of 598 patients. Ureteroscopic holmium:YAG laser lithotripsy was performed in 598 patients between 1993 and 1999. Calculi were located in the distal ureter in 39.6% of cases, mid ureter in 18.6%, proximal ureter in 32.4% and kidney in 9.4%. Patients were treated on an outpatient basis with various flexible and semirigid endoscopes. Of the cases 59% were referred as previous treatment failures. Patients were assessed 6 to 12 weeks postoperatively with repeat plain x-ray and ultrasound or excretory urography for late obstructive complications. The overall stone-free rate was 97%. As stratified by location, the stone-free rate was 98% in the distal ureter, 100% in the mid ureter, 97% in the proximal ureter and 84% in the kidney. Fragmentation was incomplete in 6% of cases and secondary intervention was required in 6%. The overall complication rate was 4%. New onset ureteral stricture developed postoperatively in 0.35% of patients. Holmium:YAG laser lithotripsy is a highly effective and safe treatment modality for managing ureteral and a proportion of intrarenal calculi on an outpatient basis. The effectiveness and versatility of the holmium laser combined with small rigid or flexible endoscopes make it our modality of choice for ureteroscopic lithotripsy.

Frequency stabilization of diode-laser-pumped solid state lasers

NASA Technical Reports Server (NTRS)

Byer, Robert L.

1988-01-01

The goal of the NASA Sunlite program is to fly two diode-laser-pumped solid-state lasers on the space shuttle and while doing so to perform a measurement of their frequency stability and temporal coherence. These measurements will be made by combining the outputs of the two lasers on an optical radiation detector and spectrally analyzing the beat note. Diode-laser-pumped solid-state lasers have several characteristics that will make them useful in space borne experiments. First, this laser has high electrical efficiency. Second, it is of a technology that enables scaling to higher powers in the future. Third, the laser can be made extremely reliable, which is crucial for many space based applications. Fourth, they are frequency and amplitude stable and have high temporal coherence. Diode-laser-pumped solid-state lasers are inherently efficient. Recent results have shown 59 percent slope efficiency for a diode-laser-pumped solid-state laser. As for reliability, the laser proposed should be capable of continuous operation. This is possible because the diode lasers can be remote from the solid state gain medium by coupling through optical fibers. Diode lasers are constructed with optical detectors for monitoring their output power built into their mounting case. A computer can actively monitor the output of each diode laser. If it sees any variation in the output power that might indicate a problem, the computer can turn off that diode laser and turn on a backup diode laser. As for stability requirements, it is now generally believed that any laser can be stabilized if the laser has a frequency actuator capable of tuning the laser frequency as far as it is likely to drift in a measurement time.

Medicaid program; revision to Medicaid upper payment limit requirements for hospital services, nursing facility services, intermediate care facility services for the mentally retarded, and clinic services. Health Care Financing Administration (HCFA), HHS. Final rule.

PubMed

2001-01-12

This final rule modifies the Medicaid upper payment limits for inpatient hospital services, outpatient hospital services, nursing facility services, intermediate care facility services for the mentally retarded, and clinic services. For each type of Medicaid inpatient service, existing regulations place an upper limit on overall aggregate payments to all facilities and a separate aggregate upper limit on payments made to State-operated facilities. This final rule establishes an aggregate upper limit that applies to payments made to government facilities that are not State government-owned or operated, and a separate aggregate upper limit on payments made to privately-owned and operated facilities. This rule also eliminates the overall aggregate upper limit that had applied to these services. With respect to outpatient hospital and clinic services, this final rule establishes an aggregate upper limit on payments made to State government-owned or operated facilities, an aggregate upper limit on payments made to government facilities that are not State government-owned or operated, and an aggregate upper limit on payments made to privately-owned and operated facilities. These separate upper limits are necessary to ensure State Medicaid payment systems promote economy and efficiency. We are allowing a higher upper limit for payment to non-State public hospitals to recognize the higher costs of inpatient and outpatient services in public hospitals. In addition, to ensure continued beneficiary access to care and the ability of States to adjust to the changes in the upper payment limits, the final rule includes a transition period for States with approved rate enhancement State plan amendments.

The LIFE Laser Design in Context: A Comparison to the State-of-the-Art

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deri, R J; Bayramian, A J; Erlandson, A C

2011-03-21

The current point design for the LIFE laser leverages decades of solid-state laser development in order to achieve the performance and attributes required for inertial fusion energy. This document provides a brief comparison of the LIFE laser point design to other state-of-the-art solid-state lasers. Table I compares the attributes of the current LIFE laser point design to other systems. the state-of-the-art for single-shot performance at fusion-relevant beamline energies is exemplified by performance observed on the National Ignition Facility. The state-of-the-art for high average power is exemplified by the Northrup Grumman JHPSSL laser. Several items in Table I deal with themore » laser efficiency; a more detailed discussion of efficiency can be found in reference 5. The electrical-to-optical efficiency of the LIFE design exceeds that of reference 4 due to the availability of higher efficiency laser diode pumps (70% vs. {approx}50% used in reference 4). LIFE diode pumps are discussed in greater detail in reference 6. The 'beam steering' state of the art is represented by the deflection device that will be used in the LIFE laser, not a laser system. Inspection of Table I shows that most LIFE laser attributes have already been experimentally demonstrated. The two cases where the LIFE design is somewhat better than prior experimental work do not involve the development of new concepts: beamline power is increased simply by increasing aperture (as demonstrated by the power/aperture comparison in Table I), and efficiency increases are achieved by employing state-of-the-art diode pumps. In conclusion, the attributes anticipated for the LIFE laser are consistent with the demonstrated performance of existing solid-state lasers.« less

Copper vapor laser precision processing

NASA Astrophysics Data System (ADS)

Nikonchuk, Michail O.

1991-05-01

Copper vapor laser (CVL) was designed on the basis master oscillator (MO) - spatial filter - amplifier (AMP) system which is placed in thermostable volume. Processing material is moved by means of CNC system GPM-AP-400 with +/- 5 micrometers accuracy. Several cutting parameters are considered which define the quality and productivity of vaporization cutting: efficiency, cutwidth, height of upper and lower burr, roughness, laser and heat affected zones. Estimates are made for some metals with thickness 0.02 - 0.3 mm and cutwidth 0.01 - 0.03 mm. The examples of workpieces produced by CVL are presented.

Investigation of Ba, BaO, Sr and SrO Pulsed Laser-Induced Vapor Plumes in N2, O2, Microwave Discharged O2, and Vacuum at Low Laser Fluence.

DTIC Science & Technology

1996-12-01

Physics and chemistry of the upper atmosphere. Great Britain: Cambridge University Press, 1989. Serway , Raymond A . Physics for Scientists and Engineers...Results ... ......... .69 4.2 Summary of the Spectral Data ..... ........... 70 4.3 Recommendations for Future Study ... ......... .71 Appendix A ...calibration curve to correlate the laser energy setting with the actual output pulse energy. A linear regression resulted in the relation "output" = 1.77 x

Spatiotemporal closure of fractional laser-ablated channels imaged by optical coherence tomography and reflectance confocal microscopy.

PubMed

Banzhaf, Christina A; Wind, Bas S; Mogensen, Mette; Meesters, Arne A; Paasch, Uwe; Wolkerstorfer, Albert; Haedersdal, Merete

2016-02-01

Optical coherence tomography (OCT) and reflectance confocal microscopy (RCM) offer high-resolution optical imaging of the skin, which may provide benefit in the context of laser-assisted drug delivery. We aimed to characterize postoperative healing of ablative fractional laser (AFXL)-induced channels and dynamics in their spatiotemporal closure using in vivo OCT and RCM techniques. The inner forearm of healthy subjects (n = 6) was exposed to 10,600 nm fractional CO2 laser using 5 and 25% densities, 120 μm beam diameter, 5, 15, and 25 mJ/microbeam. Treatment sites were scanned with OCT to evaluate closure of AFXL-channels and RCM to evaluate subsequent re-epithelialization. OCT and RCM identified laser channels in epidermis and upper dermis as black, ablated tissue defects surrounded by characteristic hyper-and hyporeflective zones. OCT imaged individual laser channels of the entire laser grid, and RCM imaged epidermal cellular and structural changes around a single laser channel to the depth of the dermoepidermal junction (DEJ) and upper papillary dermis. OCT images visualized a heterogeneous material in the lower part of open laser channels, indicating tissue fluid. By OCT the median percentage of open channels was evaluated at several time points within the first 24 hours and laser channels were found to gradually close, depending on the used energy level. Thus, at 5 mJ/microbeam, 87% (range 73-100%) of channels were open one hour after laser exposure, which declined to 27% (range 20-100%) and 20% (range 7-93%) at 12 and 24 hours after laser exposure, respectively. At 25 mJ/microbeam, 100% (range 100-100%) of channels were open 1 hour after laser exposure while 53% (range 33-100%) and 40% (range 0-100%) remained open at 12 and 24 hours after exposure. Median depth and width of open channels decreased over time depending of applied energy. RCM verified initial re-epithelialization from day 2 for all energy levels used. Morphology of ablation defects by OCT and RCM corresponded to histological assessments. OCT and RCM enabled imaging of AFXL-channels and their spatiotemporal closure. Laser channels remained open up to 24 hours post laser, which may be important for the time perspective to deliver topical substances through AFXL channels. © 2015 Wiley Periodicals, Inc.

Visible light surface emitting semiconductor laser

DOEpatents

Olbright, Gregory R.; Jewell, Jack L.

1993-01-01

A vertical-cavity surface-emitting laser is disclosed comprising a laser cavity sandwiched between two distributed Bragg reflectors. The laser cavity comprises a pair of spacer layers surrounding one or more active, optically emitting quantum-well layers having a bandgap in the visible which serve as the active optically emitting material of the device. The thickness of the laser cavity is m .lambda./2n.sub.eff where m is an integer, .lambda. is the free-space wavelength of the laser radiation and n.sub.eff is the effective index of refraction of the cavity. Electrical pumping of the laser is achieved by heavily doping the bottom mirror and substrate to one conductivity-type and heavily doping regions of the upper mirror with the opposite conductivity type to form a diode structure and applying a suitable voltage to the diode structure. Specific embodiments of the invention for generating red, green, and blue radiation are described.

A new direct absorption tunable diode laser spectrometer for high precision measurement of water vapor in the upper troposphere and lower stratosphere.

PubMed

Sargent, M R; Sayres, D S; Smith, J B; Witinski, M; Allen, N T; Demusz, J N; Rivero, M; Tuozzolo, C; Anderson, J G

2013-07-01

We present a new instrument for the measurement of water vapor in the upper troposphere and lower stratosphere (UT∕LS), the Harvard Herriott Hygrometer (HHH). HHH employs a tunable diode near-IR laser to measure water vapor via direct absorption in a Herriott cell. The direct absorption technique provides a direct link between the depth of the observed absorption line and the measured water vapor concentration, which is calculated based on spectroscopic parameters in the HITRAN database. While several other tunable diode laser (TDL) instruments have been used to measure water vapor in the UT∕LS, HHH is set apart by its use of an optical cell an order of magnitude smaller than those of other direct absorption TDLs in operation, allowing for a more compact, lightweight instrument. HHH is also unique in its integration into a common duct with the Harvard Lyman-α hygrometer, an independent photo-fragment fluorescence instrument which has been thoroughly validated over 19 years of flight measurements. The instrument was flown for the first time in the Mid-latitude Airborne Cirrus Properties Experiment (MACPEX) on NASA's WB-57 aircraft in spring, 2011, during which it demonstrated in-flight precision of 0.1 ppmv (1 s) with 1-sigma uncertainty of 5% ± 0.7 ppmv. Since the campaign, changes to the instrument have lead to improved accuracy of 5% ± 0.2 ppmv as demonstrated in the laboratory. During MACPEX, HHH successfully measured water vapor at concentrations from 3.5 to 600 ppmv in the upper troposphere and lower stratosphere. HHH and Lyman-α, measuring independently but under the same sampling conditions, agreed on average to within 1% at water vapor mixing ratios above 20 ppmv and to within 0.3 ppmv at lower mixing ratios. HHH also agreed with a number of other in situ water vapor instruments on the WB-57 to within their stated uncertainties, and to within 0.7 ppmv at low water. This agreement constitutes a significant improvement over past in situ comparisons, in which differences of 1.5-2 ppmv were routinely observed, and demonstrates that the accuracy of HHH is consistent with other instruments which use a range of detection methods and sampling techniques.

A Kennedy-Thorndike experiment using LLR data

NASA Astrophysics Data System (ADS)

Müller, J.; Soffel, M. H.

1995-02-01

We have analyzed data from Lunar Laser Ranging to determine the combination / vbζ1- ζ0-1/ vb of Robertson-Mansouri-Sexl parameters of special relativity. In such a Kennedy-Thorndike experiments we obtained a realistic upper limit for this combination of 1.5 × 10 -4 only a factor of two or so worse than that obtained with modern laser techniques in the laboratory.

Laser isotope separation of erbium and other isotopes

DOEpatents

Haynam, Christopher A.; Worden, Earl F.

1995-01-01

Laser isotope separation is accomplished using at least two photoionization pathways of an isotope simultaneously, where each pathway comprises two or more transition steps. This separation method has been applied to the selective photoionization of erbium isotopes, particularly for the enrichment of .sup.167 Er. The hyperfine structure of .sup.167 Er was used to find two three-step photoionization pathways having a common upper energy level.

Rate constants of quenching and vibrational relaxation in the OH({{A}^{2}}{{ \\Sigma }^{+}},v=0,1 ), manifold with various colliders

NASA Astrophysics Data System (ADS)

Martini, L. M.; Gatti, N.; Dilecce, G.; Scotoni, M.; Tosi, P.

2017-03-01

Laser induced fluorescence is intensively used for the detection of OH in many atmospheric pressure discharge devices. At this pressure, a quantitative knowledge of the collision phenomena in the upper excited state is critical. Here we report the measurement at T  =  300 K of a set of rate constants of electronic quenching and vibrational relaxation of the OH≤ft({{A}2}{{ Σ }+},{{v}\\prime}=0,1\\right) electronic state, by collision with N2, O2, H2O, CO2, CO, H2, D2, CH4, C2H2, C2H4, C2H6. These are the main gases in applications like plasma medicine, hydrocarbons reforming and CO2 conversion. Available literature data are revisited, and new data are added, mostly relevant to {{v}\\prime}=1 quenching and vibrational relaxation.

[The design of all solid-state tunable pulsed Ti:sapphire laser system].

PubMed

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.

Solid state laser technology - A NASA perspective

NASA Technical Reports Server (NTRS)

Allario, F.

1985-01-01

NASA's program for developing solid-state laser technology and applying it to the Space Shuttle and Space Platform is discussed. Solid-state lasers are required to fulfill the Earth Observation System's requirements. The role of the Office of Aeronautics and Space Technology in developing a NASA tunable solid-state laser program is described. The major goals of the program involve developing a solid-state pump laser in the green, using AlGaAs array technology, pumping a Nd:YAG/SLAB crystal or glass, and fabricating a lidar system, with either a CO2 laser at 10.6 microns or a Nd:YAG laser at 1.06 microns, to measure tropospheric winds to an accuracy of + or - 1 m/s and a vertical resolution of 1 km. The procedures to be followed in order to visualize this technology plan include: (1) material development and characterization, (2) laser development, and (3) implementation of the lasers.

Commercial mode-locked vertical external cavity surface emitting lasers

NASA Astrophysics Data System (ADS)

Head, C. Robin; Paboeuf, David; Ortega, Tiago; Lubeigt, Walter; Bialkowski, Bartlomiej; Lin, Jipeng; Hempler, Nils; Maker, Gareth T.; Malcolm, Graeme P. A.

2018-02-01

This paper presents the latest efforts in the development of commercial optically-pumped semiconductor disk lasers (SDLs) at M Squared Lasers. Two types of SDLs are currently being developed: an ultrafast system and a continuous wave single frequency system under the names of Dragonfly and Infinite, respectively. Both offer a compact, low-cost, easy-to-use and maintenance-free tool for a range of growing markets including nonlinear microscopy and quantum technology. To facilitate consumer uptake of the SDL technology, the performance specifications aim to closely match the currently employed systems. An extended Dragonfly system is being developed targeting the nonlinear microscopy market, which typically requires 1-W average power pulse trains with pulse durations below 200 fs. The pulse repetition frequency (PRF) of the commonly used laser systems, typically Titanium-sapphire lasers, is 80 MHz. This property is particularly challenging for mode-locked SDLs which tend to operate at GHz repetition rates, due to their short upper state carrier lifetime. Dragonfly has found a compromise at 200 MHz to balance mode-locking instabilities with a low PRF. In the ongoing development of Dragonfly, additional pulse compression and nonlinear spectral broadening stages are used to obtain pulse durations as short as 130 fs with an average power of 0.85 W, approaching the required performance. A variant of the Infinite system was adapted to provide a laser source suitable for the first stage of Sr atom cooling at 461 nm. Such a source requires average powers of approximately 1 W with a sub-MHz linewidth. As direct emission in the blue is not a viable approach at this stage, an SDL emitting at 922 nm followed by an M Squared Lasers SolTiS ECD-X doubler is currently under development. The SDL oscillator delivered >1 W of single frequency (RMS frequency noise <150kHz) light at 922 nm.

Security of two quantum cryptography protocols using the same four qubit states

DOE Office of Scientific and Technical Information (OSTI.GOV)

Branciard, Cyril; Ecole Nationale Superieure des Telecommunications, 46, rue Barrault, 75013 Paris; Gisin, Nicolas

2005-09-15

The first quantum cryptography protocol, proposed by Bennett and Brassard in 1984 (BB84), has been widely studied in recent years. This protocol uses four states (more precisely, two complementary bases) for the encoding of the classical bit. Recently, it has been noticed that by using the same four states, but a different encoding of information, one can define a protocol which is more robust in practical implementations, specifically when attenuated laser pulses are used instead of single-photon sources [V. Scarani et al., Phys. Rev. Lett. 92, 057901 (2004), referred to as the SARG04 protocol]. We present a detailed study ofmore » SARG04 in two different regimes. In the first part, we consider an implementation with a single-photon source: we derive bounds on the error rate Q for security against all possible attacks by the eavesdropper. The lower and the upper bound obtained for SARG04 (Q < or approx. 10.95% and Q > or approx. 14.9%, respectively) are close to those obtained for BB84 (Q < or approx. 12.4% and Q > or approx. 14.6%, respectively). In the second part, we consider a realistic source consisting of an attenuated laser and improve on previous analysis by allowing Alice to optimize the mean number of photons as a function of the distance. The SARG04 protocol is found to perform better than BB84, both in secret-key rate and in maximal achievable distance, for a wide class of Eve's attacks.« less

Path toward a high-energy solid-state laser

NASA Astrophysics Data System (ADS)

Wood, Gary L.; Merkle, Larry D.; Dubinskii, Mark; Zandi, Bahram

2004-04-01

Lasers have come a long way since the first demonstration by Maiman of a ruby crystal laser in 1960. Lasers are used as scientific tools as well as for a wide variety of applications for both commercial industry and the military. Today lasers come in all types, shapes and sizes depending on their application. The solid-state laser has some distinct advantages in that it can be rugged, compact, and self contained, making it reliable over long periods of time. With the advent of diode laser pumping a ten times increase in overall laser efficiency has been realized. This significant event, and others, is changing the way solid-state lasers are applied and allows new possibilities. One of those new areas of exploration is the high energy laser. Solid-state lasers for welding are already developed and yield energies in the 0.5 to 6 kilojoule range. These lasers are at the forefront of what is possible in terms of high energy solid-state lasers. It is possible to achieve energies of greater than 100 kJ. These sorts of energies would allow applications, in addition to welding, such as directed energy weapons, extremely remote sensing, power transfer, propulsion, biological and chemical agent neutralization and unexploded and mine neutralization. This article will review these new advances in solid-state lasers and the different paths toward achieving a high energy laser. The advantages and challenges of each approach will be highlighted.

Study of the functional state of peripheral vessels in fingers of rheumatological patients by means of laser Doppler flowmetry and cutaneous thermometry measurements

NASA Astrophysics Data System (ADS)

Zherebtsova, Angelina I.; Zherebtsov, Evgeny A.; Dunaev, Andrey V.; Podmasteryev, Konstantin V.; Pilipenko, Olga V.; Krupatkin, Alexander I.; Khakhicheva, Lyudmila S.; Muradyan, Vadim F.

2016-04-01

Vasospastic disorders are a common class of rheumatic disease. These include syndromes such as vegetative dystonia, Raynaud's syndrome, vibration disease and rheumatoid arthritis among others. The aim of this work is to develop an original method of diagnosing the functional state of peripheral vessels of the fingers, based on the simultaneous recording of LDF- and thermograms during the occlusion test, for determining vascular disorders of rheumatological patients. A diagnostic method was developed for assessing the functional state of the peripheral vessels of fingers, based on carrying out occlusion test in a thermally stabilized environment, with simultaneous recording of signals of laser Doppler flowmetry and skin thermometry. To verify the diagnostic value of the proposed method, a series of experiments were carried out on 41 rheumatological patients: 5 male and 36 females (average age 56.0+/-12.2 years). The most common diagnoses in the patient group were rheumatoid arthritis, arthrosis, gout and systemic lupus erythematosus. The laser analyser of blood microcirculation "LAKK-02" (SPE "LAZMA" Ltd, Russia) and a custom developed multi-channel thermometry device for low inertia thermometry were used for experimental measurements. The measurements of cutaneous temperature and the index of microcirculation were performed on the distal phalanx of the third finger of the right hand. Occlusion tests were performed with water baths at 25 and 42 °C and a tonometer cuff with a pressure of 200-220 mmHg for 3 min on the upper arm. The results of experimental studies are presented and interpreted. These data indicate a violation of the blood supply regulation in the form of a pronounced tendency towards microvascular vasoconstriction in the fingers. Thus, the response displaying a tendency toward angiospasm among patients in the rheumatological diseases profile group was observed mainly in the most severe cases (49 % of this group). The prospects of the developed diagnostic method of microcirculatory disorders in rheumatic diseases are evaluated. Thus, cutaneous blood microcirculation and temperature measurements performed together can help in diagnosis of the functional state of peripheral vessels both in a healthy state and when expressing pathology.

Laser Spectroscopic Study of CaH in the B^2σ^+ and D^2σ^+ States

NASA Astrophysics Data System (ADS)

Watanabe, Kyohei; Uchida, Kanako; Kobayashi, Kaori; Matsushima, Fusakazu; Moriwaki, Yoshiki

2015-06-01

Calcium hydride is one of the abundant molecules in the stellar environment, and is considered as a probe of stellar analysis. Ab initio calculations have shown that the electronic excited states of CaH have complex potential curves. It is suggested that the B^2σ^+ state has an interesting double minimum potential due to the avoided crossing. Such a potential leads to drastic change of the rotational constants when the vibrational energy level goes across the potential barrier. Spectroscopic studies on CaH began in the 1920's, and many studies have been carried out since then. Bell et al. extensively assigned the D^2σ^+-X^2σ^+ bands in the UV region. Bernath's group has observed transitions in the IR and visible regions and identified their upper states as the A^2σ^+, B^2σ^+ and E^2σ^+ states. We have carried out a laser induced fluorescence (LIF) study in the UV region between 360 and 430 nm. We have produced CaH by using laser ablation of a calcium target in a hydrogen gas environment, then molecules have been excited by a second harmonic pulse of dye laser and the fluorescence from molecules have been detected through a monochromator. Detection of the D^2σ^+-X^2σ^+ bands already identified by Bell et al. indicates the production of CaH. In addition, many other bands have been also found and a few bands have been assigned by using the combination differences, the lower state of these bands have been confirmed to the vibrational ground state of X^2σ^+ state. We have tentatively assigned these bands as the B^2σ^+ -X^2σ^+ transition. We will discuss the assignment of these bands, together with the rotational constants comparing with those calculated from the ab initio potential. B. Barbuy, R. P. Schiavon, J. Gregorio-Hetem, P. D. Singh C. Batalha , Astron. Astrophys. Sippl. Ser. 101, 409 (1993). P. F. Weck and P. C .Stabcil, J. Chem. Phys. {118}, 9997 (2003). R. S. Mulliken, Phys. Rev. {25}, 509 (1925). G. D. Bell, M, Herman, J. W. C. Johns, and E. R. Peck, Physica Scripta {20}, 609 (1979). A. Shayesteh, K. A. Walker, I. Gordon, D. R. T. Appadoo, and P. F. Bernath, J. Mol. Struct. {695-696}, 23 (2004). R. S. Ram, K. Tereszchuk, I. E. Gordon, K. A. Walker, and P. F. Bernath, J. Mol. Spec. {266}, 86 (2011). G. Li, J. J. Harrison, R. S. Ram, C. M. Western, and P. F. Bernath Quant. Spectrosc. Rad. Transfer. {113}, 67 (2012). A. Shayesteh, R. S. Ram, and P. F. Bernath, J. Mol. Spec. {288}, 46 (2013).

Influence of laser radiation on structure and properties of steels and alloys

NASA Astrophysics Data System (ADS)

Tarasova, T.; Popova, E.

2013-03-01

In present study, and laser alloying of different steels and laser cladding of Ti and SiC powders mixtures was carried out, and microstructure, as well as microhardness profile and wear properties were examined. Research of the influence of lasers alloying modes on the elastic and plastic characteristics of the surface was conducted. As a result of chemical reactions in the cladded layer, a new phase (TiC) was synthesized during cladding process. The results showed that, in the clad layer, TiC was solidified to form dendrites in the clad zone. Produced coatings have high microhardness values in the upper and middle clad areas, about two time higher than clad matrix microhardness.

Hair ignition by dye laser for port-wine stain: risk factors evaluated.

PubMed

Molin, L; Hallgren, S

1999-04-01

Flashlamp-pumped pulsed dye laser is the preferred treatment for port-wine stain. Vascular hemoglobin and epidermal melanin are competing sites for dye laser absorption and damage. The case presented illustrates the potential hazard of ignition induced by dye laser treatment on the face of a patient receiving inhalation anesthesia. A 6-year-old girl with almost black hair was treated for a port-wine stain covering most of the right half of her face. She was treated with dye laser under general anesthesia administered by mask. A laser pulse close to the upper part of the eyebrow induced a blaze and the eyebrow was instantly destroyed by the fire. Regrowth of the eyebrow was complete after a few months. Hair specimens of various colors were exposed experimentally to dye laser irradiation in room and oxygen-saturated atmospheres. Risk factors of ignition are high laser dosage, a high oxygen level, repeated pulses and dark colored hair.

Successful Treatment of Congenital Lymphangioma Circumscriptum of the Vulva with CO2 and Long-Pulsed Nd:YAG Lasers.

PubMed

Sasaki, Ryosuke; Negishi, Kei; Akita, Hirotaka; Suzuki, Kayoko; Matsunaga, Kayoko

2014-01-01

A 16-year-old girl presented with a 9-year history of vesicles on the vulva. She had initially taken a wait-and-see approach, but required treatment because of bleeding. Histological examination of a biopsied vesicle revealed dilated lymph channels in the upper dermis, suggesting lymphangioma circumscriptum (LC). The challenge for this pathology has been to find a conservative treatment with low morbidity and better results than those reported for surgical excision, which has been the mainstay of therapy. In this case, LC of the vulva was successfully treated using a 10,600-nm CO2 laser and long-pulsed Nd:YAG laser. Use of the 10,600-nm CO2 laser and long-pulsed Nd:YAG laser appeared effective for treating LC.

Laser isotope separation of erbium and other isotopes

DOEpatents

Haynam, C.A.; Worden, E.F.

1995-08-22

Laser isotope separation is accomplished using at least two photoionization pathways of an isotope simultaneously, where each pathway comprises two or more transition steps. This separation method has been applied to the selective photoionization of erbium isotopes, particularly for the enrichment of {sup 167}Er. The hyperfine structure of {sup 167}Er was used to find two three-step photoionization pathways having a common upper energy level. 3 figs.

Treatment of infraorbital dark circles using 694-nm fractional Q-switched ruby laser.

PubMed

Xu, Tian-Hua; Li, Yuan-Hong; Chen, John Z S; Gao, Xing-Hua; Chen, Hong-Duo

2016-12-01

The objective of this study was to evaluate the efficacy and safety of using a 694-nm fractional Q-switched ruby laser to treat infraorbital dark circles. Thirty women with infraorbital dark circles (predominant color: dark/brown) participated in this open-labeled study. The participants received eight sessions of 694-nm fractional Q-switched ruby laser treatment using a fluence of 3.0-3.5 J/cm 2 , at an interval of 7 days. The melanin deposition in the lesional skin was observed in vivo using reflectance confocal microscopy (RCM). The morphological changes were evaluated using a global evaluation, an overall self-assessment, and a Mexameter. Twenty-eight of the 30 patients showed global improvements that they rated as excellent or good. Twenty-six patients rated their overall satisfaction as excellent or good. The melanin index indicated a substantial decrease from 240.44 (baseline) to 194.56 (P < 0.05). The RCM results showed a dramatic decrease in melanin deposition in the upper dermis. The adverse effects were minimal. The characteristic finding of dark/brown infraorbital dark circles is caused by increased melanin deposition in the upper dermis. The treatment of these infraorbital dark circles using a 694-nm fractional QSR laser is safe and effective.

Circulation Control Model Experimental Database for CFD Validation

NASA Technical Reports Server (NTRS)

Paschal, Keith B.; Neuhart, Danny H.; Beeler, George B.; Allan, Brian G.

2012-01-01

A 2D circulation control wing was tested in the Basic Aerodynamic Research Tunnel at the NASA Langley Research Center. A traditional circulation control wing employs tangential blowing along the span over a trailing-edge Coanda surface for the purpose of lift augmentation. This model has been tested extensively at the Georgia Tech Research Institute for the purpose of performance documentation at various blowing rates. The current study seeks to expand on the previous work by documenting additional flow-field data needed for validation of computational fluid dynamics. Two jet momentum coefficients were tested during this entry: 0.047 and 0.114. Boundary-layer transition was investigated and turbulent boundary layers were established on both the upper and lower surfaces of the model. Chordwise and spanwise pressure measurements were made, and tunnel sidewall pressure footprints were documented. Laser Doppler Velocimetry measurements were made on both the upper and lower surface of the model at two chordwise locations (x/c = 0.8 and 0.9) to document the state of the boundary layers near the spanwise blowing slot.

Nonlinear regression method for estimating neutral wind and temperature from Fabry-Perot interferometer data.

PubMed

Harding, Brian J; Gehrels, Thomas W; Makela, Jonathan J

2014-02-01

The Earth's thermosphere plays a critical role in driving electrodynamic processes in the ionosphere and in transferring solar energy to the atmosphere, yet measurements of thermospheric state parameters, such as wind and temperature, are sparse. One of the most popular techniques for measuring these parameters is to use a Fabry-Perot interferometer to monitor the Doppler width and breadth of naturally occurring airglow emissions in the thermosphere. In this work, we present a technique for estimating upper-atmospheric winds and temperatures from images of Fabry-Perot fringes captured by a CCD detector. We estimate instrument parameters from fringe patterns of a frequency-stabilized laser, and we use these parameters to estimate winds and temperatures from airglow fringe patterns. A unique feature of this technique is the model used for the laser and airglow fringe patterns, which fits all fringes simultaneously and attempts to model the effects of optical defects. This technique yields accurate estimates for winds, temperatures, and the associated uncertainties in these parameters, as we show with a Monte Carlo simulation.

Measurement of the electron shake-off in the β-decay of laser-trapped 6He atoms

NASA Astrophysics Data System (ADS)

Hong, Ran; Bagdasarova, Yelena; Garcia, Alejandro; Storm, Derek; Sternberg, Matthew; Swanson, Erik; Wauters, Frederik; Zumwalt, David; Bailey, Kevin; Leredde, Arnaud; Mueller, Peter; O'Connor, Thomas; Flechard, Xavier; Liennard, Etienne; Knecht, Andreas; Naviliat-Cuncic, Oscar

2016-03-01

Electron shake-off is an important process in many high precision nuclear β-decay measurements searching for physics beyond the standard model. 6He being one of the lightest β-decaying isotopes, has a simple atomic structure. Thus, it is well suited for testing calculations of shake-off effects. Shake-off probabilities from the 23S1 and 23P2 initial states of laser trapped 6He matter for the on-going beta-neutrino correlation study at the University of Washington. These probabilities are obtained by analyzing the time-of-flight distribution of the recoil ions detected in coincidence with the beta particles. A β-neutrino correlation independent analysis approach was developed. The measured upper limit of the double shake-off probability is 2 ×10-4 at 90% confidence level. This result is ~100 times lower than the most recent calculation by Schulhoff and Drake. This work is supported by DOE, Office of Nuclear Physics, under Contract Nos. DE-AC02-06CH11357 and DE-FG02-97ER41020.

Optimal parameters for marking upper blepharoplasty incisions: a 10-year experience.

PubMed

Halvorson, Eric G; Husni, Nicholas R; Pandya, Sonal N; Seckel, Brooke R

2006-05-01

Although a variety of techniques for upper blepharoplasty have been described, few studies illustrate and clinically evaluate a system for marking incisions. Presented is a 10-year experience using a specific method for marking upper blepharoplasty incisions that consistently yielded excellent esthetic results. All upper blepharoplasties performed by the senior author between April, 1994 and April, 2004 were reviewed. Markings were designed to end the medial incision 6 mm from the angular vein, end the lateral incision 12 mm from the palpebral fissure, and to extend the incisions superiorly at 45 degrees. Over 10 years, 476 patients underwent cosmetic upper blepharoplasty. There were 22 (4.6%) revisions. Eighteen (3.8%) were performed in clinic using CO2 laser, and 4 (0.8%) patients required surgical revision. Patient satisfaction was high, and no scars were visible outside the brow. Excellent outcomes can be expected using this simple, reproducible, and widely applicable system for marking upper blepharoplasty incisions.

A Laser-Induced Fluorescence Instrument for Aircraft Measurements of Sulfur Dioxide in the Upper Troposphere and Lower Stratosphere

NASA Technical Reports Server (NTRS)

Rollins, Andrew W.; Thornberry, Troy D.; Ciciora, Steven J.; McLaughlin, Richard J.; Watts, Laurel A.; Hanisco, Thomas F.; Baumann, Esther; Giorgetta, Fabrizio R.; Bui, Thaopaul V.; Fahey, David W.

2016-01-01

This work describes the development and testing of a new instrument for in situ measurements of sulfur dioxide (SO2) on airborne platforms in the upper troposphere and lower stratosphere (UTLS). The instrument is based on the laser-induced fluorescence technique and uses the fifth harmonic of a tunable fiber-amplified semiconductor diode laser system at 1084.5 nm to excite SO2 at 216.9 nm. Sensitivity and background checks are achieved in flight by additions of SO2 calibration gas and zero air, respectively. Aircraft demonstration was performed during the NASA Volcano Plume Investigation Readiness and Gas-Phase and Aerosol Sulfur (VIRGAS) experiment, which was a series of flights using the NASA WB-57F during October 2015 based at Ellington Field and Harlingen, Texas. During these flights, the instrument successfully measured SO2 in the UTLS at background (non-volcanic) conditions with a precision of 2 ppt at 10 s and an overall uncertainty determined primarily by instrument drifts of +/- (16% + 0.9 ppt).

Lasers in otorhinolaryngology

NASA Astrophysics Data System (ADS)

Pais Clemente, Manuel P.

1992-03-01

Lasers are now commonly accepted and widely used surgical instruments in otorhinolaryngology. There have been a great number of technological advances with lasers that have contributed to the expansion of this new surgical modality with an increased number of medical applications. Surgical strategies have also changed and are more favorable toward conservative surgery in which less tissues is removed than with more radical resections. This combination of improving technology and medical attitudes has changed the field of otorhinolaryngology, and resulted in an expanding use of laser surgery. Since 1973 we have been using the carbon dioxide laser in the treatment of diseases of the upper aero digestive systems, learning this new surgical technique from the pioneer work of Strong, Jako, and Vaughan. It is our conviction that a laser surgeon must have a thorough knowledge of laser biophysics, instrumentation, safety protocols, and surgical indications, and have the technical skills to perform laser surgery. Laser technology continues to improve at an increased speed, and it is imperative to update knowledge of current and potential applications of lasers in our specialty. It is the purpose of this article to present our clinical experience of 18 years with the use of lasers in surgery of ORL, emphasizing the carbon dioxide laser.

Optical amplifier operating at 1.3 microns useful for telecommunications and based on dysprosium-doped metal chloride host materials

DOEpatents

Page, R.H.; Schaffers, K.I.; Payne, S.A.; Krupke, W.F.; Beach, R.J.

1997-12-02

Dysprosium-doped metal chloride materials offer laser properties advantageous for use as optical amplifiers in the 1.3 {micro}m telecommunications fiber optic network. The upper laser level is characterized by a millisecond lifetime, the host material possesses a moderately low refractive index, and the gain peak occurs near 1.31 {micro}m. Related halide materials, including bromides and iodides, are also useful. The Dy{sup 3+}-doped metal chlorides can be pumped with laser diodes and yield 1.3 {micro}m signal gain levels significantly beyond those currently available. 9 figs.

Optical amplifier operating at 1.3 microns useful for telecommunications and based on dysprosium-doped metal chloride host materials

DOEpatents

Page, Ralph H.; Schaffers, Kathleen I.; Payne, Stephen A.; Krupke, William F.; Beach, Raymond J.

1997-01-01

Dysprosium-doped metal chloride materials offer laser properties advantageous for use as optical amplifiers in the 1.3 .mu.m telecommunications fiber optic network. The upper laser level is characterized by a millisecond lifetime, the host material possesses a moderately low refractive index, and the gain peak occurs near 1.31 .mu.m. Related halide materials, including bromides and iodides, are also useful. The Dy.sup.3+ -doped metal chlorides can be pumped with laser diodes and yield 1.3 .mu.m signal gain levels significantly beyond those currently available.

Gingiva laser welding: preliminary study on an ex vivo porcine model.

PubMed

Rasca, Emilia; Nyssen-Behets, Catherine; Tielemans, Marc; Peremans, André; Hendaoui, Nordine; Heysselaer, Daniel; Romeo, Umberto; Nammour, Samir

2014-08-01

The use of lasers to fuse different tissues has been studied for 50 years. As none of these experiments concerned the oral soft tissues, our objective was to assess the feasibility of laser gingiva welding. Porcine full-thickness gingival flaps served to prepare calibrated samples in the middle of which a 2 cm long incision was closed, either by conventional suture or by laser tissue welding (LTW). To determine the irradiation conditions yielding the best tensile strength, 13 output power values, from 0.5 to 5 W, delivered either at 10 Hz or in continuous wave mode, were tested on six indocyanine green (ICG) concentrations, from 8% to 13% (588 samples). Then, some samples served to compare the tensile strength between the laser welded and the sutured gingiva; the other samples were histologically processed in order to evaluate the thermal damage extent. The temperature rise during the LTW was measured by thermocouples. Another group of 12 samples was used to measure the temperature elevation by thermal camera. In the laser welding groups, the best tensile strength (p<0.05) was yielded by the 9% ICG saline solution (117 mM) at 4.5 W, 10 Hz, and a fluence of 31.3 kJ/cm(2). The apposition strength revealed no statistically significant difference (p<0.05) between the sutured and the laser welded gingiva at 4.5 W, 10 Hz, and 9% ICG solution. The mean temperature was 74±5.4°C at the upper surface and 42±8.9°C at the lower surface. The damaged zone averaged 333 μm at the upper surface. The 808 nm diode laser associated with ICG can achieve oral mucosa LTW, which is conceivable as a promising technique of gingival repair.

Improving Reliability of High Power Quasi-CW Laser Diode Arrays for Pumping Solid State Lasers

NASA Technical Reports Server (NTRS)

Amzajerdian, Farzin; Meadows, Byron L.; Baker, Nathaniel R.; Barnes, Bruce W.; Baggott, Renee S.; Lockard, George E.; Singh, Upendra N.; Kavaya, Michael J.

2005-01-01

Most Lidar applications rely on moderate to high power solid state lasers to generate the required transmitted pulses. However, the reliability of solid state lasers, which can operate autonomously over long periods, is constrained by their laser diode pump arrays. Thermal cycling of the active regions is considered the primary reason for rapid degradation of the quasi-CW high power laser diode arrays, and the excessive temperature rise is the leading suspect in premature failure. The thermal issues of laser diode arrays are even more drastic for 2-micron solid state lasers which require considerably longer pump pulses compared to the more commonly used pump arrays for 1-micron lasers. This paper describes several advanced packaging techniques being employed for more efficient heat removal from the active regions of the laser diode bars. Experimental results for several high power laser diode array devices will be reported and their performance when operated at long pulsewidths of about 1msec will be described.

Efficiency at maximum power of a laser quantum heat engine enhanced by noise-induced coherence

NASA Astrophysics Data System (ADS)

Dorfman, Konstantin E.; Xu, Dazhi; Cao, Jianshu

2018-04-01

Quantum coherence has been demonstrated in various systems including organic solar cells and solid state devices. In this article, we report the lower and upper bounds for the performance of quantum heat engines determined by the efficiency at maximum power. Our prediction based on the canonical three-level Scovil and Schulz-Dubois maser model strongly depends on the ratio of system-bath couplings for the hot and cold baths and recovers the theoretical bounds established previously for the Carnot engine. Further, introducing a fourth level to the maser model can enhance the maximal power and its efficiency, thus demonstrating the importance of quantum coherence in the thermodynamics and operation of the heat engines beyond the classical limit.

Using airborne lidar as a sampling tool for estimating forest biomass resources in the upper Tanana Valley of interior Alaska

Treesearch

Hans-Erik Andersen; Jacob Strunk; Hailemariam Temesgen

2011-01-01

Airborne laser scanning, collected in a sampling mode, has the potential to be a valuable tool for estimating the biomass resources available to support bioenergy production in rural communities of interior Alaska. In this study, we present a methodology for estimating forest biomass over a 201,226-ha area (of which 163,913 ha are forested) in the upper Tanana valley...

ADVANCED MANUFACTURING TEAM

NASA Image and Video Library

2014-01-16

ZACK JONES AND JIM LYDON OF MSFC’S ADVANCED MANUFACTURING TEAM, WITH MSFC’S M2 SELECTIVE LASER MELTING SYSTEM. THE M2 IS CURRENTLY DEDICATED TO ADVANCED COPPER MATERIAL DEVELOPMENT FOR THE LOW COST UPPER STAGE PROGRAM.

Rapid estimation of characteristics of gas dynamic lasers

NASA Technical Reports Server (NTRS)

Murty, S. S. R.

1974-01-01

Sudden-freeze approximation is applied to the flow of a CO2-N2-He mixture in wedge-type nozzles. This approximation permits rapid estimation of the freezing temperature of the upper laser level as a function of the stagnation pressure and the nozzle geometry. The stagnation temperature and the composition of the mixture appear as parameters. Gain and power output may then be estimated and calculations are presented for two cases.

Experimental study on magnetically insulated transmission line electrode surface evolution process under MA/cm current density

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, PengFei; Qiu, Aici; State Key Laboratory of Intense Pulse Radiation of Simulation and Effect, Northwest Institute of Nuclear Technology, Xi'an 710024

The design of high-current density magnetically insulated transmission line (MITL) is a difficult problem of current large-scale Z-pinch device. In particular, a thorough understanding of the MITL electrode surface evolution process under high current density is lacking. On the “QiangGuang-I” accelerator, the load area possesses a low inductance short-circuit structure with a diameter of 2.85 mm at the cathode, and three reflux columns with a diameter of 3 mm and uniformly distributed circumference at the anode. The length of the high density MITL area is 20 mm. A laser interferometer is used to assess and analyze the state of the MITL cathode andmore » anode gap, and their evolution process under high current density. Experimental results indicate that evident current loss is not observed in the current density area at pulse leading edge, and peak when the surface current density reaches MA/cm. Analysis on electrode surface working conditions indicates that when the current leading edge is at 71.5% of the peak, the total evaporation of MITL cathode structure can be realized by energy deposition caused by ohmic heating. The electrode state changes, and diffusion conditions are reflected in the laser interferometer image. The MITL cathode area mainly exists in metal vapor form. The metal vapor density in the cathode central region is higher than the upper limit of laser penetration density (∼4 × 10{sup 21}/cm{sup 3}), with an expansion velocity of ∼0.96 km/s. The metal vapor density in the electrode outer area may lead to evident distortion of fringes, and its expansion velocity is faster than that in the center area (1.53 km/s).« less

Double fillet lap of laser welding of thin sheet AZ31B Mg alloy

NASA Astrophysics Data System (ADS)

Ishak, Mahadzir; Salleh, M. N. M.

2018-05-01

In this paper, we describe the experimental laser welding of thin sheet AZ31B using double fillet lap joint method. Laser welding is capable of producing high quality weld seams especially for small weld bead on thin sheet product. In this experiment, both edges for upper and lower sheets were subjected to the laser beam from the pulse wave (PW) mode of fiber laser. Welded sample were tested their joint strength by tensile-shear strength method and the fracture loads were studied. Strength for all welded samples were investigated and the effect of laser parameters on the joint strength and appearances were studied. Pulsed energy (EP) from laser process give higher effect on joint strength compared to the welding speed (WS) and angle of irradiation (AOI). Highest joint strength was possessed by sample with high EP with the same value of WS and AOI. The strength was low due to the crack defect at the centre of weld region.

Holmium:YAG laser: 12-year study of indications for use and outcomes in benign and malignant otolaryngological conditions.

PubMed

Joseph, J; Jaberoo, M-C; Dilkes, M

2010-08-01

We present the largest recorded case series of holmium:YAG laser use in otolaryngology. This laser's hand-held delivery device is easier to manipulate compared with other ENT lasers, and its pulsed delivery mode gives it enhanced cutting and coagulation properties. We conducted a 12-year, retrospective study of holmium:YAG laser use in a tertiary referral centre. Sixty-eight patients were included. Nineteen received primary laser treatment of squamous cell carcinoma of the upper aerodigestive tract (nine with simultaneous neck dissection), and 49 underwent either palatine or lingual tonsillectomy for benign disease. One cancer patient developed a pharyngo-cutaneous fistula, and a second suffered a secondary haemorrhage. No other complications were recorded. There were no local recurrences. The holmium:YAG laser is safe and effective for benign and malignant otolaryngological conditions. In cancer treatment, it may be best to delay neck dissection until the primary site has healed, in order to avoid fistula formation.

Excimer laser correction of hyperopia, hyperopic and mixed astigmatism: past, present, and future.

PubMed

Lukenda, Adrian; Martinović, Zeljka Karaman; Kalauz, Miro

2012-06-01

The broad acceptance of "spot scanning" or "flying spot" excimer lasers in the last decade has enabled the domination of corneal ablative laser surgery over other refractive surgical procedures for the correction of hyperopia, hyperopic and mixed astigmatism. This review outlines the most important reasons why the ablative laser correction of hyperopia, hyperopic and mixed astigmatism for many years lagged behind that of myopia. Most of today's scanning laser systems, used in the LASIK and PRK procedures, can safely and effectively perform low, moderate and high hyperopic and hyperopic astigmatic corrections. The introduction of these laser platforms has also significantly improved the long term refractive stability of hyperopic treatments. In the future, further improvements in femtosecond and nanosecond technology, eye-tracker systems, and the development of new customized algorithms, such as the ray-tracing method, could additionally increase the upper limit for the safe and predictable corneal ablative laser correction ofhyperopia, hyperopic and mixed astigmatism.

Space Operation of the MOLA Laser

NASA Technical Reports Server (NTRS)

Afzal, Robert S.

2000-01-01

Interest in lasers for space applications such as active remote sensing in Earth orbit, planetary science, and inter-satellite laser communications is growing. These instruments typically use diode-pumped solid state lasers for the laser transmitter. The mission specifications and constraints of space qualification, place strict requirements on the design and operation of the laser. Although a laser can be built in the laboratory to meet performance specifications relatively routinely, tile mission constraints demand unique options and compromises in the materials used, and design to ensure the success of the mission. Presently, the best laser architecture for a light weight, rugged, high peak power and efficient transmitter is a diode laser pumped ND:YAG laser. Diode lasers can often obviate the need for water cooling, reduce the size and weight of the laser, increase the electrical to optical efficiency, system reliability, and lifetime. This paper describes the in-space operation and performance of the Mars Orbiter Laser Altimeter (MOLA) laser transmitter, representing the current state-of-the-art in space-based solid- state lasers.

O2 Herzberg State Reaction with N2: A Possible Source of Stratospheric N2O

NASA Technical Reports Server (NTRS)

Slanger, Tom G.; Copeland, Richard A.

1997-01-01

The goal of this one-year investigation was to determine whether N2O is formed in atmospherically significant quantities by the reaction of vibrationally excited levels of the O2((A3 Sigma(sub u)(sup +)) state with nitrogen. O2(A3 Sigma(sub u)(sup +)) is made throughout the upper stratosphere in considerable amounts by solar photoabsorption, and only a very small reactive yield is necessary for this mechanism to be a major N2O source. By long-term 245-252 nm irradiation of O2/N2 mixtures on- and off-resonance with absorption lines in the O2(A3 Sigma(sub u)(sup +) - X3 Sigma(sub g)(sup -)) transition, followed by N2O analysis by frequency-modulated diode laser absorption spectroscopy, we determined an upper limit for the N2O yield of the candidate reaction. This limit, 3 x 10(exp -5), eliminates O2(A3 Sigma(sub u)(sup +)) + N2 as a significant channel for the generation of stratospheric N2O. In further measurements, we established that N2O is stable under our photolysis conditions, showing that the small amounts of ozone generated from the reaction of O2(A) and O2 do not indirectly lead to destruction of N2O.

Contaminant Monitor Laser

NASA Technical Reports Server (NTRS)

1997-01-01

Under a Small Business Innovation Research contract from Langley Research Center, OPOTEK, Inc. developed a laser transmitter for remote sensing of water vapor in the upper atmosphere. As a leader in developing and using Differential Absorption Lidar, a remote sensing technique to monitor ozone and water vapor in the atmosphere, NASA was interested in upgrading the capabilities of its airborn laser systems. The laser transmitter developed for NASA was used for measuring water vapor in the infrared region. By broadening this concept to other wavelengths, OPOTEK believes a range of industrial applications can be met. In addition, the tunable laser system can be used by the Drug Enforcement Administration to discern the by-products from illegal drug manufacturing. A host of other government, university, and industrial laboratory uses for the technology are also being examined as follow-up by the company.

Tunable diode laser-pumped Tm,Ho:YLF laser operated in continuous-wave and Q-switched modes

NASA Technical Reports Server (NTRS)

Mcguckin, B. T.; Hemmati, H.; Menzies, R. T.

1992-01-01

Tunable continuous-wave and pulsed laser output was obtained from a Tm-sensitized Ho:YLiF4 crystal at subambient temperatures when longitudinally pumped with a diode laser array. A conversion efficiency of 42 percent and slope efficiency of approximately 60 percent relative to the absorbed pumped power have been achieved at a crystal temperature of 275 K. The emission spectrum was etalon tunable over a range of 16/cm centered at 2067 nm with fine tuning capability of the transition frequency with crystal temperature at measured rate of -0.03/cm/K. Output energies of 0.22 mJ per pulse and 22 ns pulse duration were recorded at Q-switch frequencies that correspond to an effective upper laser level lifetime of 6 ms, and a pulse energy extraction efficiency of 64 percent.

Frequency dependence of the maximum operating temperature for quantum-cascade lasers up to 5.4 THz

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wienold, M.; Humboldt Universität zu Berlin, Institut für Physik, Newtonstr. 15, 12489 Berlin; Deutsches Zentrum für Luft und Raumfahrt, Rutherfordstr. 2, 12489 Berlin

2015-11-16

We report on the observation of an approximately linear reduction in the maximum operating temperature with an increasing emission frequency for terahertz quantum-cascade lasers between 4.2 and 5.4 THz. These lasers are based on the same design type, but vary in period length and barrier height for the cascade structure. The sample emitting at the highest frequency around 5.4 THz can be operated in pulsed mode up to 56 K. We identify an additional relaxation channel for electrons by longitudinal optical phonon scattering from the upper to the lower laser level and increasing optical losses toward higher frequencies as major processes,more » leading to the observed temperature behavior.« less

Watching the Real-time Evolution of a Laser Modified Atom Using Attosecond Pulses

NASA Astrophysics Data System (ADS)

Shivaram, Niranjan; Timmers, Henry; Tong, Xiao-Min; Sandhu, Arvinder

2011-10-01

In the presence of even moderately strong laser fields, atomic states are heavily modified and develop rich structure. Such a laser dressed atom can be described using the Floquet theory in which the laser dressed states called Floquet states are composed of different Fourier components. In this work we use XUV attosecond pulses to excite a He atom from its ground state to near-infrared (NIR) laser dressed Floquet states, which are ionized by the dressing laser field. Quantum interferences between Fourier components of these Floquet states lead to oscillations in He ion yield as a function of time-delay between the XUV and NIR pulses. From the ion yield signal we measure the quantum phase difference between transition matrix elements to two different Fourier components as a function of both time-delay (instantaneous NIR intensity) and NIR pulse peak intensity. These measurements along with information from time-dependent Schrodinger equation simulations enable us to observe the real-time evolution of the laser modified atom as the dominant Floquet state mediating the ionization changes from the 5p Floquet state to the 2p Floquet state with increasing NIR intensity.

Helium in chirped laser fields as a time-asymmetric atomic switch

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaprálová-Žďánská, Petra Ruth, E-mail: kapralova@jh-inst.cas.cz; J. Heyrovsky Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Dolejškova 3, 182 23 Prague 8; Moiseyev, Nimrod, E-mail: nimrod@tx.technion.ac.il

2014-07-07

Tuning the laser parameters exceptional points in the spectrum of the dressed laser helium atom are obtained. The weak linearly polarized laser couples the ground state and the doubly excited P-states of helium. We show here that for specific chirped laser pulses that encircle an exceptional point one can get the time-asymmetric phenomenon, where for a negative chirped laser pulse the ground state is transformed into the doubly excited auto-ionization state, while for a positive chirped laser pulse the resonance state is not populated and the neutral helium atoms remains in the ground state as the laser pulse is turnedmore » off. Moreover, we show that the results are very sensitive to the closed contour we choose. This time-asymmetric state exchange phenomenon can be considered as a time-asymmetric atomic switch. The optimal time-asymmetric switch is obtained when the closed loop that encircles the exceptional point is large, while for the smallest loops, the time-asymmetric phenomenon does not take place. A systematic way for studying the effect of the chosen closed contour that encircles the exceptional point on the time-asymmetric phenomenon is proposed.« less

Laser resonance ionization spectroscopy of antimony

NASA Astrophysics Data System (ADS)

Li, R.; Lassen, J.; Ruczkowski, J.; Teigelhöfer, A.; Bricault, P.

2017-02-01

The resonant ionization laser ion source is an element selective, efficient and versatile ion source to generate radioactive ion beams at on-line mass separator facilities. For some elements with complex atomic structures and incomplete spectroscopic data, laser spectroscopic investigations are required for ionization scheme development. Laser resonance ionization spectroscopy using Ti:Sa lasers has been performed on antimony (Sb) at TRIUMF's off-line laser ion source test stand. Laser light of 230.217 nm (vacuum wavelength) as the first excitation step and light from a frequency-doubled Nd:YVO4 laser (532 nm) as the nonresonant ionization step allowed to search for suitable second excitation steps by continuous wavelength scans from 720 nm to 920 nm across the wavelength tuning range of a grating-tuned Ti:Sa laser. Upon the identification of efficient SES, the third excitation steps for resonance ionization were investigated by laser scans across Rydberg states, the ionization potential and autoionizing states. One Rydberg state and six AI states were found to be well suitable for efficient resonance ionization.

In-vivo experimental evaluation of nonablative skin remodeling using a 1.54-μm laser with surface cooling

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.

First collaborative experience with thulium laser ablation of localized upper urinary tract urothelial tumors using retrograde intra-renal surgery.

PubMed

Defidio, Lorenzo; De Dominicis, Mauro; Di Gianfrancesco, Luca; Fuchs, Gerhard; Patel, Anup

2011-09-01

Thulium laser ablation (TLA) outcomes with blinded performance evaluation after retrograde intra-renal surgical (RIRS) treatment of upper urinary tract transitional cell carcinomas (UUT-TCC). A UUT-TCC patient cohort undergoing RIRS-TLA by an international endoscopic surgical collaboration in a European center (April 2005-July 2009), underwent outcomes evaluation. All 4 surgeons were blinded and independently scored both TLA and Holmium:YAG laser ablation performance aspects annually using a Likert scoring system (0-10). All patients (n = 59, median age 66 years, 9 with solitary kidney) had complete UUT inspection. Presenting lesion(s) were intra-renal (n = 30, 51%), ureteral (n = 13, 22%), and combined (n = 16, 27%). Single-stage TLA sufficed in 81.4% (tumors < 1.5 cm). Significant recurrence free survival differences occurred according to primary tumor size >/< 1.5 cm and multi-focality, but location made no difference. Median Likert scores were i) fiber-tip stability --5.5/8.75, p = 0.016; ii) reduced bleeding--5/8.5, p = 0.004; iii)fiber-tip precision--5.5/8.5, p = 0.003; iv) mucosal perforation reduction--3.5/7.5, p = 0.001; v) ablation efficiency tumors < 1.5 cm--6/9, p = 0.017; tumors > 1.5 cm--6.75/6.75, p = 1, and vi) overall efficiency--6/7.5, p = 0.09, for Holmium:YAG and TLA, respectively. The Thulium laser delivered non-inferior recurrence free survival to RIRS-UUT-TCC Holmium:YAG laser ablation, but better median parameter performance scores in fiber-tip stability, precision, reduced bleeding and mucosal perforation reduction in expert ratings. Despite improved photothermal coagulation, and endo-visualization for tumors < 1.5 cm, both ablation and overall efficiency remained challenging for larger tumors with both existing laser technologies.

Tooth Whitening And Temperature Rise With Two Bleaching Activation Methods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abu-ElMagd, D. M.; El-Sayad, I. I.; Abd El-Gawad, L. M.

2009-09-27

To measure the tooth whitening and the surface and Intrapulpal temperature increase in vitro on freshly extracted upper human central incisors after chemical, Zoom AP light and diode laser activated bleaching. Thirty caries-free upper human incisors were selected. Teeth were divided into three equal groups according to the methods of activation of the bleaching agent (n = 10). A whitening gel containing hydrogen peroxide was applied to the buccal surface of all teeth. Group I was bleached using chemically activated hydrogen peroxide gel, for three applications of 15 min each. Group II was bleached with high intensity advanced power Zoommore » activation light (Zoom AP), for three applications of 15 min each. Group III was bleached with diode laser activation technique, where the teeth were irradiated with 2 Watt diode laser for three applications of 30 sec each. The whitening degree was assessed using an image analysis system, while temperature rise was recorded using a thermocouple on the external tooth surface and Intrapulpal. The degree of whitening increased significantly in all groups. However, the percentage of whitening was not statistically significantly different between the three groups. In addition, group II showed statistically significant higher mean rise in both surface and pulp temperatures than group I and group III. Chemical bleaching produces the same whitening effect as Zoom AP light and laser, with no surface or pulpal temperature rise. Laser application is faster and produces less surface and pulp temperature increase than Zoom AP light. Diode laser used to activate bleaching gels is not considered dangerous to the vitality of dental pulp using power settings of 2 W.« less

High power diode and solid state lasers

NASA Astrophysics Data System (ADS)

Eichler, H. J.; Fritsche, H.; Lux, O.; Strohmaier, S. G.

2017-01-01

Diode lasers are now basic pump sources of crystal, glass fiber and other solid state lasers. Progress in the performance of all these lasers is related. Examples of recently developed diode pumped lasers and Raman frequency converters are described for applications in materials processing, Lidar and medical surgery.

ADVANCED MANUFACTURING TEAM

NASA Image and Video Library

2014-01-16

QUINCY BEAN, JIM LYDON, AND ZACK JONES OF MSFC’S ADVANCED MANUFACTURING TEAM, WITH MSFC’S M2 SELECTIVE LASER MELTING SYSTEM. THE M2 IS CURRENTLY DEDICATED TO ADVANCED COPPER MATERIAL DEVELOPMENT FOR THE LOW COST UPPER STAGE PROGRAM.

The Effect of Intense Laser Radiation on Atomic Collisions

NASA Astrophysics Data System (ADS)

Young, Stephen Michael Radley

1991-02-01

Available from UMI in association with The British Library. Requires signed TDF. We have carried out theoretical and experimental studies into the effect of intense laser radiation on atomic collisions. The first experiment used neon. Excitation by electron impact in a gas discharge demanded a pressure of at least 0.075 Torr. Measurement of the intensity of 3^1S_0to 3^1P_1 fluorescence has been made for the case where high intensity ASE wings in the laser profile and background laser scatter are unimportant, with the laser tuned to resonance. The field intensity required to produce strong field fluorescence (exemplified by the Mollow triplet) was found to give rise to complications capable of screening the effects sought. Our theoretical model has suggested that at finite detunings, line-centre fluorescence will dominate Rayleigh scatter and omega_3 fluorescence. Our measurements provide information on the saturation of neon fluorescence but not of the variation of the intense field collision rate. Absorption of weak field 253.7 nm laser photons by ground state mercury atoms yielded a high 6 ^3P_1 population at a lower pressure of 0.02 Torr. The Mollow triplet has been observed in the self-broadened mercury system. Dressing of the upper transition (6^3P_1rightarrow 7^3S_1) by an intense laser close to 435.8 nm yielded the strong field signal. Polarisation studies were made possible by the 3-level mercury system (radiation trapping in a 2-level system would depolarise fluorescence) perturbed by argon. The studies yielded results that were explainable in terms of the selective population of Stark shifted dressed states by a detuned, weak probe field. Use has been made of the electric-dipole radiation selection rule m_{J}=0 rightarrow m_{J^' } = 0 unless J=J^' to devise a 'Stark shift collision switch'. The competition between collision and radiation induced transitions within the mercury atom has then been studied. The resonant, strong lambda 435.8 nm field was used in conjunction with the weak lambda 253.7 nm field detuned by 0 to 6 cm^ {-1}. Measurement of fluorescence intensity in two perpendicular planes of polarisation has revealed the dominant | e_1> to | e_2> excitation channel as a function of the Stark shift by way of the U.V. detuning. Competition between the channels was dependent on the generalised Rabi frequency. However, we could only monitor the relative strength of the channels and were thus unable to say that the Stark shift switched collisions off. (Abstract shortened by UMI.).

Fundamental characteristics of degradation-recoverable solid-state DFB polymer laser.

PubMed

Yoshioka, Hiroaki; Yang, Yu; Watanabe, Hirofumi; Oki, Yuji

2012-02-13

A novel solid-state dye laser with degradation recovery was proposed and demonstrated. Polydimethylsiloxane was used as a nanoporous solid matrix to enable the internal circulation of dye molecules in the solid state. An internal circulation model for the dye molecules was also proposed and verified numerically by assuming molecular mobility and using a proposed diffusion equation. The durability of the laser was increased 20.5-fold compared with that of a conventional polymethylmethacrylate laser. This novel laser solves the low-durability problem of dye-doped polymer lasers.

Using airborne light detection and ranging as a sampling tool for estimating forest biomass resources in the upper Tanana Valley of interior Alaska

Treesearch

Hans-Erik Andersen; Jacob Strunk; Hailemariam Temesgen

2011-01-01

Airborne laser scanning, collected in a sampling mode, has the potential to be a valuable tool for estimating the biomass resources available to support bioenergy production in rural communities of interior Alaska. In this study, we present a methodology for estimating forest biomass over a 201,226-ha area (of which 163,913 ha are forested) in the upper Tanana valley...

Compact Ozone Differential Absorption Lidar (DIAL) Transmitter Using Solid-State Dye Polymers

NASA Technical Reports Server (NTRS)

Jones, Alton L., Jr.; DeYoung, Russell J.; Elsayid-Ele, Hani

2001-01-01

A new potential DIAL laser transmitter is described that uses solid-state dye laser materials to make a simpler, more compact, lower mass laser system. Two solid-state dye laser materials were tested to evaluate their performance in a laser oscillator cavity end pumped by a pulsed Nd:YAG laser at 532 nm. The polymer host polymethyl-methacrylate was injected with a pyrromethene laser dye, PM 580, or PM 597. A narrowband laser oscillator cavity was constructed to produce visible wavelengths of 578 and 600 nm which were frequency doubled into the UV region (299 or 300 nm) by using a BBO crystal, resulting in a maximum energy of 11 mJ at a wavelength of 578 nm when pumped by the Nd:YAG laser at an energy of 100 mJ (532 nm). A maximum output energy of 378 microJ was achieved in the UV region at a wavelength of 289 nm but lasted only 2000 laser shots at a repetition rate of 10 Hz. The results are promising and show that a solid-state dye laser based ozone DIAL system is possible with improvements in the design of the laser transmitter.

Bibliography of Soviet Laser Developments, Number 66, July-August 1983.

DTIC Science & Technology

1984-09-01

7 5. Glass : Nd............................................8 6. Glass : Er............................................9 7. Glass ...upper lasing level of neodymium in y-La2S 3 semiconductor crystals and _a2S_ 2Ga20 3 glass . KE, no. 8, 1983, 1560-1564. 7. Kaminskiy, A.A., N.R. Agamalyan...injection semiconductor lasers. FTP, no. 7, 1983, 1353-1355. 5. Glass : Nd 44. Gvatua, Sh.Sh., Z.V. Katselashvili, V.N. Polukhin, S.N. Popov, T.V. Prangishvili

O2(a1Δ) vibrational kinetics in oxygen-iodine laser

NASA Astrophysics Data System (ADS)

Torbin, A. P.; Pershin, A. A.; Heaven, M. C.; Azyazov, V. N.; Mebel, A. M.

2018-04-01

Kinetics of vibrationally-excited singlet oxygen O2(a1Δ,ν) in gas mixture O3/N2/CO2 was studied using a pulse laser technique. Molecules O2(a1Δ,ν) were produced by laser photolysis of ozone at 266 nm. The O3 molecules number density was followed using time-resolved absorption spectroscopy. It was found that an upper bound for the rate constant of chemical reaction O2(a1Δ,ν)+ O3 is about 10-15 cm3/s. The rate constants of O2(a1Δ,ν= 1, 2 and 3) quenching by CO2 are presented.

Development of optical laser balloon and drainage from radiation vulcanized natural rubber latex

NASA Astrophysics Data System (ADS)

Shimamura, Yoshiyuki

Rubber film made of radiation vulcanized natural rubber latex (RVNRL) has better transparency and lower toxicity compared with sulfur-vulcanized latex film. Optical laser balloon (optical endoscopical balloon) and drainage were developed by using RVNRL. An endoscope was equipped with a saline-filled latex rubber balloon at its tip to displace contaminating blood, bile, or gastric contents during operative portoscopy, biliary endoscopy, or upper gastrointestinal endoscopy. The transmission of Nd-Yag laser through the balloon is 98%, higher than the sulfur-vulcanized latex rubber (75%). High transparency of the drainage bag facilitated easy observation of discharged fluids without detaching the bag from the tube.

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

This viewgraph presentation shows the development of 2-micron solid state lasers. The topics covered include: 1) Overview 2-micron solid state lasers; 2) Modeling and population inversion measurement; 3) Side pump oscillator; and 4) One Joule 2-m Laser.

Solar-pumped solid state Nd lasers

NASA Technical Reports Server (NTRS)

Williams, M. D.; Zapata, L.

1985-01-01

Solid state neodymium lasers are considered candidates for space-based polar-pumped laser for continuous power transmission. Laser performance for three different slab laser configurations has been computed to show the excellent power capability of such systems if heat problems can be solved. Ideas involving geometries and materials are offered as potential solutions to the heat problem.

High power multiple wavelength diode laser stack for DPSSL application without temperature control

NASA Astrophysics Data System (ADS)

Hou, Dong; Yin, Xia; Wang, Jingwei; Chen, Shi; Zhan, Yun; Li, Xiaoning; Fan, Yingmin; Liu, Xingsheng

2018-02-01

High power diode laser stack is widely used in pumping solid-state laser for years. Normally an integrated temperature control module is required for stabilizing the output power of solid-state laser, as the output power of the solid-state laser highly depends on the emission wavelength and the wavelength shift of diode lasers according to the temperature changes. However the temperature control module is inconvenient for this application, due to its large dimension, high electric power consumption and extra adding a complicated controlling system. Furthermore, it takes dozens of seconds to stabilize the output power when the laser system is turned on. In this work, a compact hard soldered high power conduction cooled diode laser stack with multiple wavelengths is developed for stabilizing the output power of solid-state laser in a certain temperature range. The stack consists of 5 laser bars with the pitch of 0.43mm. The peak output power of each bar in the diode laser stack reaches as much as 557W and the combined lasing wavelength spectrum profile spans 15nm. The solidstate laser, structured with multiple wavelength diode laser stacks, allows the ambient temperature change of 65°C without suddenly degrading the optical performance.

Free-beam and contact laser soft-tissue ablation in urology.

PubMed

Tan, Andrew H H; Gilling, Peter J

2003-10-01

The ablation of tissue by laser has several applications in urology. Most of the published research has been concerned with the treatment of benign prostatic hyperplasia (BPH). Other applications studied include superficial upper- and lower-tract transitional-cell carcinoma, urethral and ureteral strictures, ureteropelvic junction stenosis, and posterior urethral valves. The attraction of laser ablation for the treatment of BPH lies with the decreased morbidity in comparison with standard transurethral electrocautery resection of the prostate and the ability to remove tissue immediately and therefore allow a more rapid progression to catheter removal and early voiding. The three main laser wavelengths used in urology for tissue ablation are the neodymium:yttrium-aluminum-garnet when used with contact tips or high-density power settings, the potassium-titanyl-phosphate, and the holmium:YAG. This article reviews the published literature on the use of these laser wavelengths in soft-tissue ablation, focusing on the treatment of BPH.

Model of Laser-Induced Temperature Changes in Solid-State Optical Refrigerators

DTIC Science & Technology

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

Diagnosis of Plasma States in X-Ray Laser Experiments

DTIC Science & Technology

1992-10-01

J e AD-A256 909 FOREIGN AEROSPACE SCIENCE AND TECHNOLOGY CENTER DTIC 4 OCT 2 6 1992’ DIAGNOSIS OF PLASMA STATES IN X-RAY LASER EXPERIMENTS by Yang ...0619-92 HUMAN TRANSLATION FASTC-ID(RS)T-0619-92 8 October 1992 DIAGNOSIS OF PLASMA STATES IN X-RAY LASER EXPERIMENTS By: Yang Shangjin, Cai Yuqin, Chunyu... Yang Shangjin, Cai Yuqin, and Chunyu Shutai China Academy of Engineering Physics Abstract At an LF-12 laser installation, an Nd glass laser of

Ultracold Fermions in the P-Orbital Band of an Optical Lattice

DTIC Science & Technology

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

EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Investigation of the populations of excited states of barium atoms in a laser plasma

NASA Astrophysics Data System (ADS)

Burimov, V. N.; Zherikhin, A. N.; Popkov, V. L.

1995-02-01

Laser-induced fluorescence was used in an investigation of the populations of the ground and excited (6s5d 3D1 and 3D2) states of Ba atoms in a plasma formed by laser ablation of Y—Ba—Cu—O target. A nonequilibrium velocity distribution of the atoms was detected. At large distances from the target about 4% of the atoms were in an excited state.

A new solid-state, frequency-doubled neodymium-YAG photocoagulation system.

PubMed

Jalkh, A E; Pflibsen, K; Pomerantzeff, O; Trempe, C L; Schepens, C L

1988-06-01

We have developed a solid-state laser system that produces a continuous green monochromatic laser beam of 532 nm by doubling the frequency of a neodymium-YAG laser wavelength of 1064 nm with a potassium-titamyl-phosphate crystal. Photocoagulation burns of equal size and intensity were placed in two rabbit eyes with the solid-state laser system and the regular green argon laser system, respectively, using the same slit-lamp mode of delivery. Histologic findings of lesion sections revealed no important differences between the two systems. In theory, the longer wavelength of the solid-state laser offers the advantages of less scattering in ocular media, higher absorption by oxyhemoglobin, and less absorption by macular xanthophyll than the 514-nm wavelength of the regular green argon laser. The solid-state laser has impressive technical advantages: it contains no argon-ion gas tube that wears out and is expensive to replace; it is much more power efficient, and thus considerably smaller and compact; it is sturdier and easily movable; it does not require external cooling; it uses a 220-V monophasic alternating current; and it requires little maintenance.

Phase-transition oscillations induced by a strongly focused laser beam

NASA Astrophysics Data System (ADS)

Devailly, Clémence; Crauste-Thibierge, Caroline; Petrosyan, Artyom; Ciliberto, Sergio

2015-11-01

We report the observation of a surprising phenomenon consisting in a oscillating phase transition which appears in a binary mixture when this is enlightened by a strongly focused infrared laser beam. The mixture is poly-methyl-meth-acrylate (PMMA)-3-octanone, which has an upper critical solution temperature at Tc=306.6 K and volume fraction ϕc=12.8 % [Crauste et al., arXiv:1310.6720, 2013]. We describe the dynamical properties of the oscillations, which are produced by a competition between various effects: the local accumulation of PMMA produced by the laser beam, thermophoresis, and nonlinear diffusion. We show that the main properties of this kind of oscillations can be reproduced in the Landau theory for a binary mixture in which a local driving mechanism, simulating the laser beam, is introduced.

Growth and spectral-luminescent study of SrMoO4 crystals doped with Tm3+ ions

NASA Astrophysics Data System (ADS)

Dunaeva, E. E.; Zverev, P. G.; Doroshenko, M. E.; Nekhoroshikh, A. V.; Ivleva, L. I.; Osiko, V. V.

2016-03-01

SrMoO4 crystals doped with Tm3+ ions have been produced from a melt using the Czochralski method; their spectral-luminescent characteristics have been studied, and laser radiation has been generated at the wavelength of 1.94 μm using laser-diode excitation. The high absorption section at the wavelength of 795 nm, the fairly high luminescence section, the long lifetime at the upper laser level 3F4 of 1.5 ms, and a wide luminescence band allow one to hope for developing efficient tunable Tm3+: SrMoO4 crystal lasers with diode pumping in the range of 1.7-2.0 μm, which are capable of implementing SRS self-transformation of radiation into the middle IR band.

Multistabilities and symmetry-broken one-color and two-color states in closely coupled single-mode lasers.

PubMed

Clerkin, Eoin; O'Brien, Stephen; Amann, Andreas

2014-03-01

We theoretically investigate the dynamics of two mutually coupled, identical single-mode semi-conductor lasers. For small separation and large coupling between the lasers, symmetry-broken one-color states are shown to be stable. In this case the light outputs of the lasers have significantly different intensities while at the same time the lasers are locked to a single common frequency. For intermediate coupling we observe stable symmetry-broken two-color states, where both lasers lase simultaneously at two optical frequencies which are separated by up to 150 GHz. Using a five-dimensional model, we identify the bifurcation structure which is responsible for the appearance of symmetric and symmetry-broken one-color and two-color states. Several of these states give rise to multistabilities and therefore allow for the design of all-optical memory elements on the basis of two coupled single-mode lasers. The switching performance of selected designs of optical memory elements is studied numerically.

Multistabilities and symmetry-broken one-color and two-color states in closely coupled single-mode lasers

NASA Astrophysics Data System (ADS)

Clerkin, Eoin; O'Brien, Stephen; Amann, Andreas

2014-03-01

We theoretically investigate the dynamics of two mutually coupled, identical single-mode semi-conductor lasers. For small separation and large coupling between the lasers, symmetry-broken one-color states are shown to be stable. In this case the light outputs of the lasers have significantly different intensities while at the same time the lasers are locked to a single common frequency. For intermediate coupling we observe stable symmetry-broken two-color states, where both lasers lase simultaneously at two optical frequencies which are separated by up to 150 GHz. Using a five-dimensional model, we identify the bifurcation structure which is responsible for the appearance of symmetric and symmetry-broken one-color and two-color states. Several of these states give rise to multistabilities and therefore allow for the design of all-optical memory elements on the basis of two coupled single-mode lasers. The switching performance of selected designs of optical memory elements is studied numerically.

Synthetic laser medium

DOEpatents

Stokowski, S.E.

1987-10-20

A laser medium is particularly useful in high average power solid state lasers. The laser medium includes a chromium dopant and preferably neodymium ions as codopant, and is primarily a gadolinium scandium gallium garnet, or an analog thereof. Divalent cations inhibit spiral morphology as large boules from which the laser medium is derived are grown, and a source of ions convertible between a trivalent state and a tetravalent state at a low ionization energy are in the laser medium to reduce an absorption coefficient at about one micron wavelength otherwise caused by the divalent cations. These divalent cations and convertible ions are dispersed in the laser medium. Preferred convertible ions are provided from titanium or cerium sources.

Synthetic laser medium

DOEpatents

Stokowski, Stanley E.

1989-01-01

A laser medium is particularly useful in high average power solid state lasers. The laser medium includes a chormium dopant and preferably neodymium ions as codopant, and is primarily a gadolinium scandium gallium garnet, or an analog thereof. Divalent cations inhibit spiral morphology as large boules from which the laser medium is derived are grown, and a source of ions convertible between a trivalent state and a tetravalent state at a low ionization energy are in the laser medium to reduce an absorption coefficient at about one micron wavelength otherwise caused by the divalent cations. These divalent cations and convertible ions are dispersed in the laser medium. Preferred convertible ions are provided from titanium or cerium sources.

Solid-state coherent laser radar wind shear measuring systems

NASA Technical Reports Server (NTRS)

Huffaker, R. Milton

1992-01-01

Coherent Technologies, Inc. (CTI) was established in 1984 to engage in the development of coherent laser radar systems and subsystems with applications in atmospheric remote sensing, and in target tracking, ranging and imaging. CTI focuses its capabilities in three major areas: (1) theoretical performance and design of coherent laser radar system; (2) development of coherent laser radar systems for government agencies such as DoD and NASA; and (3) development of coherent laser radar systems for commercial markets. The topics addressed are: (1) 1.06 micron solid-state coherent laser radar system; (2) wind measurement using 1.06 micron system; and flashlamp-pumped 2.09 micron solid-state coherent laser radar system.

CW and Q-switched GGG/Er:Pr:GGG/GGG composite crystal laser at 2.7 µm

NASA Astrophysics Data System (ADS)

You, Z. Y.; Wang, Y.; Sun, Y. J.; Xu, J. L.; Zhu, Z. J.; Li, J. F.; Wang, H. Y.; Tu, C. Y.

2017-04-01

We report the continuous-wave (CW) and passively Q-switched laser operations of a GGG/Er:Pr:GGG/GGG composite crystal at about 2.7 µm. Owing to the alleviation of the thermal lensing effect, the CW laser with a maximum output power of 463 mW was obtained with a slope efficiency of 15.5%. Based on the broadband saturable absorption property, a graphene saturable absorber (SA) mirror was fabricated and employed for realizing the Q-switched mid-infrared laser. Under an absorbed pump power of 2.47 W, an average output power of 186 mW was generated with a slope efficiency of 12.3%. The pulse width and the repetition rate of the laser were 360 ns and 120.5 kHz, respectively. These results indicate that the Er:Pr:GGG crystal, with the relatively lower upper-level lifetime, shows great promise for generating a short pulsed 2.7 µm mid-infrared laser using the graphene SA.

Experimental Results from a Resonant Dielectric Laser Accelerator

NASA Astrophysics Data System (ADS)

Yoder, Rodney; McNeur, Joshua; Sozer, Esin; Travish, Gil; Hazra, Kiran Shankar; Matthews, Brian; England, Joel; Peralta, Edgar; Wu, Ziran

2015-04-01

Laser-powered accelerators have the potential to operate with very large accelerating gradients (~ GV/m) and represent a path toward extremely compact colliders and accelerator technology. Optical-scale laser-powered devices based on field-shaping structures (known as dielectric laser accelerators, or DLAs) have been described and demonstrated recently. Here we report on the first experimental results from the Micro-Accelerator Platform (MAP), a DLA based on a slab-symmetric resonant optical-scale structure. As a resonant (rather than near-field) device, the MAP is distinct from other DLAs. Its cavity resonance enhances its accelerating field relative to the incoming laser fields, which are coupled efficiently through a diffractive optic on the upper face of the device. The MAP demonstrated modest accelerating gradients in recent experiments, in which it was powered by a Ti:Sapphire laser well below its breakdown limit. More detailed results and some implications for future developments will be discussed. Supported in part by the U.S. Defense Threat Reduction Agency (UCLA); U.S. Dept of Energy (SLAC); and DARPA (SLAC).

Partial ablation of Ti/Al nano-layer thin film by single femtosecond laser pulse

NASA Astrophysics Data System (ADS)

Gaković, B.; Tsibidis, G. D.; Skoulas, E.; Petrović, S. M.; Vasić, B.; Stratakis, E.

2017-12-01

The interaction of ultra-short laser pulses with Titanium/Aluminium (Ti/Al) nano-layered thin film was investigated. The sample composed of alternating Ti and Al layers of a few nanometres thick was deposited by ion-sputtering. A single pulse irradiation experiment was conducted in an ambient air environment using focused and linearly polarized femtosecond laser pulses for the investigation of the ablation effects. The laser induced morphological changes and the composition were characterized using several microscopy techniques and energy dispersive X-ray spectroscopy. The following results were obtained: (i) at low values of pulse energy/fluence, ablation of the upper Ti layer only was observed; (ii) at higher laser fluence, a two-step ablation of Ti and Al layers takes place, followed by partial removal of the nano-layered film. The experimental observations were supported by a theoretical model accounting for the thermal response of the multiple layered structure upon irradiation with ultra-short laser pulses.

New capability for ozone dial profiling measurements in the troposphere and lower stratosphere from aircraft

NASA Astrophysics Data System (ADS)

Hair, Johnathan; Hostetler, Chris; Cook, Anthony; Harper, David; Notari, Anthony; Fenn, Marta; Newchurch, Mike; Wang, Lihua; Kuang, Shi; Knepp, Travis; Burton, Sharon; Ferrare, Richard; Butler, Carolyn; Collins, Jim; Nehrir, Amin

2018-04-01

Recently, we successfully demonstrated a new compact and robust ozone DIAL lidar for smaller aircraft such as the NASA B200 and the ER-2 high-altitude aircraft. This is the first NASA airborne lidar to incorporate advanced solid-state lasers to produce the required power at the required ultraviolet wavelengths, and is compact and robust enough to operate nearly autonomously on the high-altitude ER-2 aircraft. This technology development resulted in the first new NASA airborne ozone DIAL instrument in more than 15 years. The combined ozone, aerosol, and clouds measurements provide valuable information on the chemistry, radiation, and dynamics of the atmosphere. In particular, from the ER-2 it offers a unique capability to study the upper troposphere and lower stratosphere.

Magneto-optical trap for thulium atoms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sukachev, D.; Sokolov, A.; Chebakov, K.

2010-07-15

Thulium atoms are trapped in a magneto-optical trap using a strong transition at 410 nm with a small branching ratio. We trap up to 7x10{sup 4} atoms at a temperature of 0.8(2) mK after deceleration in a 40-cm-long Zeeman slower. Optical leaks from the cooling cycle influence the lifetime of atoms in the magneto-optical trap which varies between 0.3 and 1.5 s in our experiments. The lower limit for the leaking rate from the upper cooling level is measured to be 22(6) s{sup -1}. The repumping laser transferring the atomic population out of the F=3 hyperfine ground-state sublevel gives amore » 30% increase for the lifetime and the number of atoms in the trap.« less

Equation of State of Fe3C and Implications for the Carbon Content of Earth's Core

NASA Astrophysics Data System (ADS)

Davis, A.; Brauser, N.; Thompson, E. C.; Chidester, B.; Greenberg, E.; Prakapenka, V. B.; Campbell, A.

2017-12-01

Carbon is a common component in protoplanetary cores, as represented by iron meteorites. Therefore, along with silicon, oxygen, and other light elements, it is likely to be an alloying component with iron in Earth's core. Previous studies of the densities of iron carbides have not reached the combined pressure and temperature conditions relevant to Earth's core. To better understand the geophysical implications of carbon addition to Earth's core, we report P-V-T measurements of Fe3C to pressures and temperatures exceeding 110 GPa and 2500 K, using synchrotron X-ray diffraction in a laser heated diamond anvil cell. Fitting these measurements to an equation of state and assuming 1.5% density change upon melting and a 4000 K core-mantle boundary temperature, we report a value of 6 wt% carbon necessary to match the PREM density in the outer core. This value should be considered an upper bound due to the likely presence of other light elements.

Upper atmosphere research: Reaction rate and optical measurements

NASA Technical Reports Server (NTRS)

Stief, L. J.; Allen, J. E., Jr.; Nava, D. F.; Payne, W. A., Jr.

1990-01-01

The objective is to provide photochemical, kinetic, and spectroscopic information necessary for photochemical models of the Earth's upper atmosphere and to examine reactions or reactants not presently in the models to either confirm the correctness of their exclusion or provide evidence to justify future inclusion in the models. New initiatives are being taken in technique development (many of them laser based) and in the application of established techniques to address gaps in the photochemical/kinetic data base, as well as to provide increasingly reliable information.

Coherent laser radar at 2 microns using solid-state lasers

NASA Technical Reports Server (NTRS)

Henderson, Sammy W.; Suni, Paul J. M.; Hale, Charley P.; Hannon, Stephen M.; Magee, James R.; Bruns, Dale L.; Yuen, Eric H.

1993-01-01

Coherent laser radar systems using 2-micron Tm- and Tm, Ho-doped solid-state lasers are useful for the remote range-resolved measurement of atmospheric winds, aerosol backscatter, and DIAL measurements of atmospheric water vapor and CO2 concentrations. Recent measurements made with a 2-micron coherent laser radar system, advances in the laser technology, and atmospheric propagation effects on 2-micron coherent lidar performance are described.

The solid state detector technology for picosecond laser ranging

NASA Technical Reports Server (NTRS)

Prochazka, Ivan

1993-01-01

We developed an all solid state laser ranging detector technology, which makes the goal of millimeter accuracy achievable. Our design and construction philosophy is to combine the techniques of single photon ranging, ultrashort laser pulses, and fast fixed threshold discrimination while avoiding any analog signal processing within the laser ranging chain. The all solid state laser ranging detector package consists of the START detector and the STOP solid state photon counting module. Both the detectors are working in an optically triggered avalanche switching regime. The optical signal is triggering an avalanche current buildup which results in the generation of a uniform, fast risetime output pulse.

Development of a Free-Electron Laser Center and Research in Medicine, Biology and Materials Science,

DTIC Science & Technology

1992-05-14

Elastin Production in Tissue Culture", Debra A.Gonzalez MD, David L. Zealear, PhD., J.M. Davidson, PhD., Robert H. Ossoff, MD, DMD , August 1990...Otolaryngoloty-Head and Neck Surgery. K. "CO2 Laser Micromanipulator Parallax Error Resolved, Jay Werkhaven,MD, Jerri Tribble, and Robert H. Ossoff, MD, DMD ...of the Upper Aerodigestive Tract, Robert H. Ossoff, MD, DMD , Al Aly, MD, Nick Houchin, AAS, and Debra Gonzalez, MD, Vanderbilt University, Nashville

Introduction to Special Section on Recent Advances in the Study of Optical Variability in the Near-Surface and Upper Ocean

DTIC Science & Technology

2012-06-30

laser wave height ( lidar ) measurement system was deployed from a boom connected between the bows of the R/V Kilo Moana’s twin hulls [Zappa et al...Robbins et al., 2006], and a surfactant skimmer called the Lil KM (Figure 1). Also, a small aircraft equipped with lidar instrumentation made...c) R/P FLIP starboard boom during the Hawaii Exper- iment in September 2009. The air-sea flux package, orthogonal scanning laser altimeters

Detectability limit and uncertainty considerations for laser induced fluorescence spectroscopy in flames

NASA Technical Reports Server (NTRS)

Daily, J. W.

1978-01-01

Laser induced fluorescence spectroscopy of flames is discussed, and derived uncertainty relations are used to calculate detectability limits due to statistical errors. Interferences due to Rayleigh scattering from molecules as well as Mie scattering and incandescence from particles have been examined for their effect on detectability limits. Fluorescence trapping is studied, and some methods for reducing the effect are considered. Fluorescence trapping places an upper limit on the number density of the fluorescing species that can be measured without signal loss.

ARPA/NRL X-Ray Laser Program - Semiannual Technical Report to Defense Advanced Research Projects Agency, 1 Jul 1974-31 December 1974

DTIC Science & Technology

1975-05-01

Finally, diagnostics for quantitative measurements of all these properties are necessary for meaningful comparison of the experiments with theoretical ...width (FWHM) of 120 ^rad. For comparison, a beam which fills the last amplifier rod has a corresponding theoretical divergence angle of 108 urad...hydrogen the protons produced by photoionization do not absorb). Also shown are the spontaneous lifetimes tu of the upper laser level, of use for self

Dye-impregnated polymer-filled porous glass: a new composite material for solid state dye lasers and laser beam control optical elements (Abstract Only)

NASA Astrophysics Data System (ADS)

Koldunov, M. F.; Manenkov, Alexander A.; Sitnikov, N. M.; Dolotov, S. M.

1994-07-01

Polymer-filled microporous glass (PFMG) composite materials have been recently proposed as a proper host for dyes to create solid-state dye lasers and laser beam control elements (Q-switchers, etc.) [1,2]. In this paper we report investigation of some laser-related properties of Polymethilmethacrylate (PMAA) - filled porous glass doped with Rhodamine 6G perchiorate (active lasing dye) and 1055 dye (passive bleachable dye): laser induced damage threshold, lasmg efficiency, bleaching efficiency, and microhardness have been measured. All these characteristics have been found to be rather high indicating that PFMG composite materials are perspective hosts for dye impregnation and fabrication highly effective solid-state dye lasers and other laser related elements (Q-switchers, mode-lockers, modeselectors, spatial filters).

Tunable solid-state laser technology for applications to scientific and technological experiments from space

NASA Technical Reports Server (NTRS)

Allario, F.; Taylor, L. V.

1986-01-01

Current plans for the Earth Observing System (EOS) include development of a lidar facility to conduct scientific experiments from a polar orbiting platforms. A recommended set of experiments were scoped, which includes techniques of atmospheric backscatter (Lidar), Differential Absorption Lidar (DIAL), altimetry, and retroranging. Preliminary assessments of the resources (power, weight, volume) required by the Eos Lidar Facility were conducted. A research program in tunable solid state laser technology was developed, which includes laser materials development, modeling and experiments on the physics of solid state laser materials, and development of solid state laser transmitters with a strong focus on Eos scientific investigations. Some of the system studies that were conducted which highlight the payoff of solid state laser technology for the Eos scientific investigations will be discussed. Additionally, a summary of some promising research results which have recently emerged from the research program will be presented.

Nitrous Oxide In The Antarctic Stratosphere

NASA Technical Reports Server (NTRS)

Podolske, J. R.; Loewenstein, M.; Strahan, S. E.; Chan, K. R.

1991-01-01

Paper reports on measurements of nitrous oxide (N2O) in upper atmosphere of Southern Hemisphere, made by tunable-laser absorption spectrometer on airplane. Measurements fill gap in information about distribution of N2O over Antarctic while ozone hole forming.

Blue-green upconversion laser

DOEpatents

Nguyen, D.C.; Faulkner, G.E.

1990-08-14

A blue-green laser (450--550 nm) uses a host crystal doped with Tm[sup 3+]. The Tm[sup 3+] is excited through upconversion by a red pumping laser and an IR pumping laser to a state which transitions to a relatively lower energy level through emissions in the blue-green band, e.g., 450.20 nm at 75 K. The exciting laser may be tunable dye lasers or may be solid-state semiconductor laser, e.g., GaAlAs and InGaAlP. 3 figs.

Blue-green upconversion laser

DOEpatents

Nguyen, Dinh C.; Faulkner, George E.

1990-01-01

A blue-green laser (450-550 nm) uses a host crystal doped with Tm.sup.3+. The Tm.sup.+ is excited through upconversion by a red pumping laser and an IR pumping laser to a state which transitions to a relatively lower energy level through emissions in the blue-green band, e.g., 450.20 nm at 75 K. The exciting laser may be tunable dye lasers or may be solid-state semiconductor laser, e.g., GaAlAs and InGaAlP.

Highly efficient dual-wavelength mid-infrared CW Laser in diode end-pumped Er:SrF2 single crystals

PubMed Central

Ma, Weiwei; Qian, Xiaobo; Wang, Jingya; Liu, Jingjing; Fan, Xiuwei; Liu, Jie; Su, Liangbi; Xu, Jun

2016-01-01

The spectral properties and laser performance of Er:SrF2 single crystals were investigated and compared with Er:CaF2. Er:SrF2 crystals have larger absorption cross-sections at the pumping wavelength, larger mid-infrared stimulated emission cross-sections and much longer fluorescence lifetimes of the upper laser level (Er3+:4I11/2 level) than those of Er:CaF2 crystals. Dual-wavelength continuous-wave (CW) lasers around 2.8 μm were demonstrated in both 4at.% and 10at.% Er:SrF2 single crystals under 972 nm laser diode (LD) end pumping. The laser wavelengths are 2789.3 nm and 2791.8 nm in the former, and 2786.4 nm and 2790.7 nm in the latter, respectively. The best laser performance has been demonstrated in lightly doped 4at.% Er:SrF2 with a low threshold of 0.100 W, a high slope efficiency of 22.0%, an maximum output power of 0.483 W. PMID:27811994

Highly efficient dual-wavelength mid-infrared CW Laser in diode end-pumped Er:SrF2 single crystals.

PubMed

Ma, Weiwei; Qian, Xiaobo; Wang, Jingya; Liu, Jingjing; Fan, Xiuwei; Liu, Jie; Su, Liangbi; Xu, Jun

2016-11-04

The spectral properties and laser performance of Er:SrF 2 single crystals were investigated and compared with Er:CaF 2 . Er:SrF 2 crystals have larger absorption cross-sections at the pumping wavelength, larger mid-infrared stimulated emission cross-sections and much longer fluorescence lifetimes of the upper laser level (Er 3+ : 4 I 11/2 level) than those of Er:CaF 2 crystals. Dual-wavelength continuous-wave (CW) lasers around 2.8 μm were demonstrated in both 4at.% and 10at.% Er:SrF 2 single crystals under 972 nm laser diode (LD) end pumping. The laser wavelengths are 2789.3 nm and 2791.8 nm in the former, and 2786.4 nm and 2790.7 nm in the latter, respectively. The best laser performance has been demonstrated in lightly doped 4at.% Er:SrF 2 with a low threshold of 0.100 W, a high slope efficiency of 22.0%, an maximum output power of 0.483 W.

Highly efficient dual-wavelength mid-infrared CW Laser in diode end-pumped Er:SrF2 single crystals

NASA Astrophysics Data System (ADS)

Ma, Weiwei; Qian, Xiaobo; Wang, Jingya; Liu, Jingjing; Fan, Xiuwei; Liu, Jie; Su, Liangbi; Xu, Jun

2016-11-01

The spectral properties and laser performance of Er:SrF2 single crystals were investigated and compared with Er:CaF2. Er:SrF2 crystals have larger absorption cross-sections at the pumping wavelength, larger mid-infrared stimulated emission cross-sections and much longer fluorescence lifetimes of the upper laser level (Er3+:4I11/2 level) than those of Er:CaF2 crystals. Dual-wavelength continuous-wave (CW) lasers around 2.8 μm were demonstrated in both 4at.% and 10at.% Er:SrF2 single crystals under 972 nm laser diode (LD) end pumping. The laser wavelengths are 2789.3 nm and 2791.8 nm in the former, and 2786.4 nm and 2790.7 nm in the latter, respectively. The best laser performance has been demonstrated in lightly doped 4at.% Er:SrF2 with a low threshold of 0.100 W, a high slope efficiency of 22.0%, an maximum output power of 0.483 W.

A study of narrow gap laser welding for thick plates using the multi-layer and multi-pass method

NASA Astrophysics Data System (ADS)

Li, Ruoyang; Wang, Tianjiao; Wang, Chunming; Yan, Fei; Shao, Xinyu; Hu, Xiyuan; Li, Jianmin

2014-12-01

This paper details a new method that combines laser autogenous welding, laser wire filling welding and hybrid laser-GMAW welding to weld 30 mm thick plate using a multi-layer, multi-pass process. A “Y” shaped groove was used to create the joint. Research was also performed to optimize the groove size and the processing parameters. Laser autogenous welding is first used to create the backing weld. The lower, narrowest part of the groove is then welded using laser wire filling welding. Finally, the upper part of the groove is welded using laser-GMAW hybrid welding. Additionally, the wire feeding and droplet transfer behaviors are observed by high speed photography. The two main conclusions from this work are: the wire is often biased towards the side walls, resulting in a lack of fusion at the joint and the creation of other defects for larger groove sizes. Additionally, this results in the droplet transfer behavior becoming unstable, leading to a poor weld appearance for smaller groove sizes.

Emerging solid-state laser technology by lidar/DIAL remote sensing

NASA Technical Reports Server (NTRS)

Killinger, Dennis

1992-01-01

Significant progress has been made in recent years in the development of new, solid-state laser sources. This talk will present an overview of some of the new developments in solid-state lasers, and their application toward lidar/DIAL measurements of the atmosphere. Newly emerging lasers such as Ho:YAG, Tm:YAG, OPO, and Ti:Sapphire will be covered, along with the spectroscopic parameters required for differential operational modes of atmospheric remote sensing including Doppler-Windshear lidar, Tunable laser detection of water/CO2, and broad linewidth OPO's for open path detection of pollutant hydrocarbon gases. Additional considerations of emerging laser technology for lidar/DIAL will also be covered.

Solid State Laser

NASA Technical Reports Server (NTRS)

1990-01-01

The Titan-CW Ti:sapphire (titanium-doped sapphire) tunable laser is an innovation in solid-state laser technology jointly developed by the Research and Solid State Laser Divisions of Schwartz Electro-optics, Inc. (SEO). SEO is producing the laser for the commercial market, an outgrowth of a program sponsored by Langley Research Center to develop Ti:sapphire technology for space use. SEO's Titan-CW series of Ti:sapphire tunable lasers have applicability in analytical equipment designed for qualitative analysis of carbohydrates and proteins, structural analysis of water, starch/sugar analyses, and measurements of salt in meat. Further applications are expected in semiconductor manufacture, in medicine for diagnosis and therapy, and in biochemistry.

Color speckle in laser displays

NASA Astrophysics Data System (ADS)

Kuroda, Kazuo

2015-07-01

At the beginning of this century, lighting technology has been shifted from discharge lamps, fluorescent lamps and electric bulbs to solid-state lighting. Current solid-state lighting is based on the light emitting diodes (LED) technology, but the laser lighting technology is developing rapidly, such as, laser cinema projectors, laser TVs, laser head-up displays, laser head mounted displays, and laser headlamps for motor vehicles. One of the main issues of laser displays is the reduction of speckle noise1). For the monochromatic laser light, speckle is random interference pattern on the image plane (retina for human observer). For laser displays, RGB (red-green-blue) lasers form speckle patterns independently, which results in random distribution of chromaticity, called color speckle2).

Solid State Lasers from an Efficiency Perspective

NASA Technical Reports Server (NTRS)

Barnes, Norman P.

2007-01-01

Solid state lasers have remained a vibrant area of research because several major innovations expanded their capability. Major innovations are presented with emphasis focused on the laser efficiency. A product of efficiencies approach is developed and applied to describe laser performance. Efficiency factors are presented in closed form where practical and energy transfer effects are included where needed. In turn, efficiency factors are used to estimate threshold and slope efficiency, allowing a facile estimate of performance. Spectroscopic, thermal, and mechanical data are provided for common solid state laser materials.

Saturation amplitude of the f-mode instability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kastaun, Wolfgang; Willburger, Beatrix; Kokkotas, Kostas D.

2010-11-15

We investigate strong nonlinear damping effects which occur during high amplitude oscillations of neutron stars, and the gravitational waves they produce. For this, we use a general relativistic nonlinear hydrodynamics code in conjunction with a fixed spacetime (Cowling approximation) and a polytropic equation of state (EOS). Gravitational waves are estimated using the quadrupole formula. Our main interest are l=m=2 f modes subject to the CFS (Chandrasekhar, Friedman, Schutz) instability, but we also investigate axisymmetric and quasiradial modes. We study various models to determine the influence of rotation rate and EOS. We find that axisymmetric oscillations at high amplitudes are predominantlymore » damped by shock formation, while the nonaxisymmetric f modes are mainly damped by wave breaking and, for rapidly rotating models, coupling to nonaxisymmetric inertial modes. From the observed nonlinear damping, we derive upper limits for the saturation amplitude of CFS-unstable f modes. Finally, we estimate that the corresponding gravitational waves for an oscillation amplitude at the upper limit should be detectable with the advanced LIGO (Laser Interferometer Gravitational Wave Observatory) and VIRGO interferometers at distances above 10 Mpc. This strongly depends on the stellar model, in particular, on the mode frequency.« less

Charge displacement in bacteriorhodopsin during the forward and reverse bR-K phototransition.

PubMed Central

Groma, G I; Hebling, J; Ludwig, C; Kuhl, J

1995-01-01

Dried oriented purple membrane samples of Halobacterium salinarium were excited by 150 fs laser pulses of 620 nm with a 7 kHz repetition rate. An unusual complex picosecond electric response signal consisting of a positive and a negative peak was detected by a sampling oscilloscope. The ratio of the two peaks was changed by 1) reducing the repetition rate, 2) varying the intensity of the excitation beam, and 3) applying background illumination by light of 647 nm or 511 nm. All of these features can be explained by the simultaneous excitation of the bacteriorhodopsin ground form and the K intermediate. The latter was populated by the (quasi)continuous excitation attributable to its prolonged lifetime in a dehydrated state. Least-square analysis resulted in a 5 ps upper and 2.5 ps lower limit for the time constant of the charge displacement process, corresponding to the forward reaction. That is in good agreement with the formation time of K. The charge separation driven by the reverse phototransition was faster, having a time constant of a 3.5 ps upper limit. The difference in the rates indicates the existence of different routes for the forward and the reverse photoreactions. PMID:8580349

Water vapor measurements in- and outside cirrus with the novel water vapor mass spectrometer AIMS-H2O

NASA Astrophysics Data System (ADS)

Kaufmann, Stefan; Schlage, Romy; Voigt, Christiane; Jurkat, Tina; Krämer, Martina; Rolf, Christian; Zöger, Martin; Schäfler, Andreas; Dörnbrack, Andreas

2015-04-01

Water vapor plays a crucial role for the earth's climate both directly via its radiative properties and indirectly due to its ability to form clouds. However, accurate measurements of especially low water vapor concentrations prevalent in the upper troposphere and lower stratosphere are difficult and exhibit large discrepancies between different instruments and methods. In order to address this issue and to provide a comprehensive water vapor data set necessary to gather a complete picture of cloud formation processes, four state-of-the-art hygrometers including the novel water vapor mass spectrometer AIMS-H2O were deployed on the DLR research aircraft HALO during the ML-Cirrus campaign in March/April 2014 over Europe. Here, we present first water vapor measurements of AIMS-H2O on HALO. The instrument performance is validated by intercomparison with the fluorescence hygrometer FISH and the laser hygrometer SHARC, both also mounted in the aircraft. This intercomparison shows good agreement between the instruments from low stratospheric mixing ratios up to higher H2O concentrations at upper tropospheric conditions. Gathering data from over 24 flight hours, no significant offsets between the instruments were found (mean of relative deviation

Single-frequency Ince-Gaussian mode operations of laser-diode-pumped microchip solid-state lasers.

PubMed

Ohtomo, Takayuki; Kamikariya, Koji; Otsuka, Kenju; Chu, Shu-Chun

2007-08-20

Various single-frequency Ince-Gaussian mode oscillations have been achieved in laser-diode-pumped microchip solid-state lasers, including LiNdP(4)O(12) (LNP) and Nd:GdVO(4), by adjusting the azimuthal symmetry of the short laser resonator. Ince-Gaussian modes formed by astigmatic pumping have been reproduced by numerical simulation.

Large laser projection displays utilizing all-solid-state RGB lasers

NASA Astrophysics Data System (ADS)

Xu, Zuyan; Bi, Yong

2005-01-01

RGB lasers projection displays have the advantages of producing large color triangle, high color saturation and high image resolution. In this report, with more than 4W white light synthesized by red (671nm), green (532nm) and blue (473nm) lasers, a RGB laser projection display system based on diode pumped solid-state lasers is developed and the performance of brilliant and vivid DVD dynamitic pictures on 60 inch screen is demonstrated.

Free-flying experiment to measure the Schawlow-Townes linewidth limit of a 300 THz laser oscillator

NASA Technical Reports Server (NTRS)

Byer, R. L.; Byvik, C. E.

1988-01-01

Recent advances in laser diode-pumped solid state laser sources permit the design and testing of laser sources with linewidths that approach the Schawlow-Townes limit of 1 Hz/mW of output power. Laser diode pumped solid state ring oscillators have been operated with CW output power levels of 25 mW at electrical efficiencies that exceed 6 percent. These oscillators are expected to operate for lifetimes that approach those of the laser diode sources which is now approaching 20,000 hours. The efficiency and lifetime of these narrow linewidth laser sources will enable space measurements of gravity waves, remote sensing applications (including local range rate and measurements), and laser sources for frequency and time standards. A free-flight experiment, 'SUNLITE', is being designed to measure the linewidth of this all-solid-state laser system.

Small Business Innovations

NASA Technical Reports Server (NTRS)

1994-01-01

A Small Business Innovation Research (SBIR) contract resulted in a series of commercially available lasers, which have application in fiber optic communications, difference frequency generation, fiber optic sensing and general laboratory use. Developed under a Small Business Innovation Research (SBIR) contract, the Phase Doppler Particles Analyzer is a non-disruptive, highly accurate laser-based method of determining particle size, number density, trajectory, turbulence and other information about particles passing through a measurement probe volume. The system consists of an optical transmitter and receiver, signal processor and computer with data acquisition and analysis software. A variety of systems are offered for applications including spray characterization for paint, and agricultural and other sprays. The Microsizer, a related product, is used in medical equipment manufacturing and analysis of contained flows. High frequency components and subsystems produced by Millitech Corporation are marketed for both research and commercial use. These systems, which operate in the upper portion of the millimeter wave, resulted from a number of Small Business Innovation Research (SBIR) projects. By developing very high performance mixers and multipliers, the company has advanced the state of the art in sensitive receiver technology. Components are used in receivers and transceivers for monitoring chlorine monoxides, ozone, in plasma characterization and in material properties characterization.

The 12 micron band of ethane: A spectral catalog from 765 cm(-1) to 900 cm(-1)

NASA Technical Reports Server (NTRS)

Atakan, A. K.; Blass, W. E.; Brault, J. W.; Daunt, S. J.; Halsey, G. W.; Jennings, D. E.; Reuter, D. C.; Susskind, J.

1983-01-01

The high resolution laboratory absorption spectrum of the 12 micro band of ethane gas is studied. The data were obtained using the McMath Solar Telescope 1 meter Fourier Transform interferometer at Kitt Peak National Observatory and tunable diode laser spectrometers at the University of Tennessee and NASA/Goddard Space Flight Center. Over 200 individual vibration rotation transitions were analyzed taking into account many higher order effects including torsional splitting. Line positions were reproduced to better than 0.001/cm. Both ground and upper state molecular constants were determined in the analysis. The experimental details, the analysis procedures and the results are addressed. A list of ethane transitions occurring near (14)CO2 laser lines needed for heterodyne searches for C2H6 in extraterrestrial sources is also included. A spectral catalog of the ethane nu sub g fundamental from 765/cm to 900/cm is provided. A high dispersion (1/cm 12 in.) plot of both the Kitt Peak interferometric data and a simulated spectrum with Doppler limited resolution, a table of over 8500 calculated transitions listed quantum number assignments, frequencies and intensities are provided.

Endoscopic laser arytenoidectomy with the use of CO2 laser

NASA Astrophysics Data System (ADS)

Malandrakis, S.; Prokopakis, E. P.; Sidoris, M.; Karatzanis, A.; Velegrakis, G.; Helidonis, Emmanuel S.

2004-06-01

Upper airway obstruction due to bilateral vocal cord paralysis presents a serious challenge to the Otolaryngologist. Various surgical techniques have been advocated for the management of patients with vocal cord patients with vocal cord paralysis. Among these techniques, the individual use of laser CO2 arytenoidectomy and posterior cordotomy has gained wide acceptance. In this report, we describe our experience in the management of bilateral vocal cord paralysis by combining posterior partial cordotomy as described by Dennis and Kashima with total arytenoidectomy as described by Ossoff. We report the long term results in the management of 24 patients with bilateral vocal cord paralysis treated in our Department during the last 9 years.

Effects of contaminants in CO2 lasers.

NASA Technical Reports Server (NTRS)

Smith, N. S.

1973-01-01

A theoretical model which includes the effects of contaminants is developed for the high flow electric discharge CO2-N2-He laser. The model couples the excitation and relaxation processes, CO2 dissociation, and negative ion formation with the flow processes. An analysis of the effects of CO, O2, NO, and N2O impurities on the average small signal gain is presented. CO decreases the gain by collisional depopulation of the upper laser level, and O2, NO, and N2O reduce the gain by decreasing the electron density by forming stable negative ions. In particular, N2O exhibits a strong quenching effect because of its large dissociation cross section for the formation of O(-).

Tunable laser heterodyne spectrometer measurements of atmospheric species

NASA Technical Reports Server (NTRS)

Allario, F.; Katzberg, S. J.; Hoell, J. M.

1983-01-01

It is pointed out that spectroscopic measurements conducted with the aid of tunable laser heterodyne spectrometers in the 3-30 micron range of the electromagnetic spectrum have the potential to measure the vertical profiles of tenuous gas molecules in the atmosphere with ultra high spectral resolution and great sensitivity. Programs related to the realization of this potential have been conducted for some time, and a Laser Heterodyne Spectrometer (LHS) experiment was developed. The present investigation has the objective to provide an overview of the LHS concept for measuring the vertical profiles of tenuous gas molecules in the upper atmosphere from space and airborne platforms, and to discuss the sensitivity ranges for this technique.

980-nm diode laser and fiber optic resectoscope in endourological surgery

NASA Astrophysics Data System (ADS)

Cecchetti, Walter; Guazzieri, Stefano; Tasca, Andrea; Dal Bianco, M.; Zattoni, Filiberto; Pagano, Francesco

1996-12-01

The 980 nm Ceralas D50 diode laser, produces homogeneous lesions on tissues of different nature. In our endourological tests we used the Ceralas D50 coupled with Comeg 24 ch laser resectoscope, and we treated 22 patients: n.5 bladder cancers, n.3 uretero pelvic junction obstructions, with hydronephrosis, n.3 urethra stenosis, n1 ureter stenosis, n.4 multiple upper tract transitional cell carcinomas, n.6 BPH treatments with VLAP modalities. Using the 1000 micrometers delivery fibers with different shaped tips, we obtained a bloodless sharp cut and easily vaporizations with minimum carbonizations, with power output in the range of 8-12 W, and 18-24W for VLAP.

1 kW peak power passively Q-switched Nd(3+)-doped glass integrated waveguide laser.

PubMed

Charlet, B; Bastard, L; Broquin, J E

2011-06-01

Embedded optical sensors always require more compact, stable, and powerful laser sources. In this Letter, we present a fully integrated passively Q-switched laser, which has been realized by a Ag(+)/Na(+) ion exchange on a Nd(3+)-doped phosphate glass. A BDN-doped cellulose acetate thick film is deposited on the waveguide, acting as an upper cladding and providing a distributed saturable absorption. At λ=1054 nm, the device emits pulses of 1.3 ns FWHM with a repetition rate of 28 kHz. These performances, coupled with the 1 kW peak power, are promising for applications such as supercontinuum generation. © 2011 Optical Society of America

Novel application of an established technique for removing a knotted ureteric stent.

PubMed

Tempest, Heidi; Turney, Ben; Kumar, Sunil

2011-04-13

This report describes a case whereby a ureteric stent became knotted during removal and lodged within the upper ureter. The authors describe a novel minimally invasive technique to remove the knotted ureteric stent using the holmium laser.

Effect of nuclear motion on molecular high order harmonic pump probe spectroscopy.

PubMed

Bredtmann, Timm; Chelkowski, Szczepan; Bandrauk, André D

2012-11-26

We study pump-probe schemes for the real time observation of electronic motion on attosecond time scale in the molecular ion H(2)(+) and its heavier isotope T(2)(+) while these molecules dissociate on femtosecond time scale by solving numerically the non-Born-Oppenheimer time-dependent Schrödinger equation. The UV pump laser pulse prepares a coherent superposition of the three lowest lying quantum states and the time-delayed mid-infrared, intense few-femtosecond probe pulse subsequently generates molecular high-order harmonics (MHOHG) from this coherent electron-nuclear wavepacket (CENWP). Varying the pump-probe time delay by a few hundreds of attoseconds, the MHOHG signal intensity is shown to vary by orders of magnitude. Due to nuclear movement, the coherence of these two upper states and the ground state is lost after a few femtoseconds and the MHOHG intensity variations as function of pump-probe delay time are shown to be equal to the period of electron oscillation in the coherent superposition of the two upper dissociative quantum states. Although this electron oscillation period and hence the periodicity of the harmonic spectra are quite constant over a wide range of internuclear distances, a strong signature of nuclear motion is seen in the actual shapes and ways in which these spectra change as a function of pump-probe delay time, which is illustrated by comparison of the MHOHG spectra generated by the two isotopes H(2)(+) and T(2)(+). Two different regimes corresponding roughly to internuclear distances R < 4a(0) and R > 4a(0) are identified: For R < 4a(0), the intensity of a whole range of frequencies in the plateau region is decreased by orders of magnitude when the delay time is changed by a few hundred attoseconds whereas in the cutoff region the peaks in the MHOHG spectra are red-shifted with increasing pump-probe time delay. For R > 4a(0), on the other hand, the peaks both in the cutoff and plateau region are red-shifted with increasing delay times with only slight variations in the peak intensities. A time-frequency analysis shows that in the case of a two-cycle probe pulse the sole contribution of one long and associated short trajectory correlates with the attenuation of a whole range of frequencies in the plateau region for R < 4a(0) whereas the observed red shift for R > 4a(0), even in the plateau region, correlates with a single electron return within one-half laser cycle.

Flexible ureterorenoscopy and laser lithotripsy in children

PubMed Central

Yeow, When-Chan; Pemberton, Richard; Barker, Andrew

2009-01-01

Background: Flexible ureterorenoscopy (FUR) and laser lithotripsy (LL) are techniques used in the management of upper urinary tract disorders. These techniques, so far established in adults, are now being used in children as well. We report our experience with 26 cases of pediatric upper urinary tract disorders treated using these techniques. Methods: In the period from 1997 to 2006, FUR was performed in 26 children (14 males and 12 females) in the age group of three months to 15 years with a mean age of 8.2 years. Twenty five were stented prior to undergoing FUR and 24 presented with suspected upper tract stones (17 pelvicalyceal and seven midureteric). Two cases showed JJ stent migration post-pyeloplasty. Results: Eight cases involved diagnostic procedures. Six excluded the presence of renal calculi, one had focal medullary sponge kidney, and one had calcified papillae. There were 15 cases of therapeutic FUR. Of these, 12 had LL with only one had incomplete stone fragmentation which subsequently passed spontaneously. Other therapeutic procedures included removal of migrated JJ stents and FUR with the basket removal of a midureteric calculus. Three cases failed ureterorenoscopy due to technical difficulties. The overall success rate was 88.5% for FUR. Conclusion: FUR and LL are valuable minimally invasive techniques for the examination and treatment of pediatric upper urinary tract conditions. Preoperative stenting improves passage of the ureteroscope and with progressive miniaturization of instruments, the lower weight limit will decrease. PMID:20671848

Monolithic solid-state lasers for spaceflight

NASA Astrophysics Data System (ADS)

Krainak, Michael A.; Yu, Anthony W.; Stephen, Mark A.; Merritt, Scott; Glebov, Leonid; Glebova, Larissa; Ryasnyanskiy, Aleksandr; Smirnov, Vadim; Mu, Xiaodong; Meissner, Stephanie; Meissner, Helmuth

2015-02-01

A new solution for building high power, solid state lasers for space flight is to fabricate the whole laser resonator in a single (monolithic) structure or alternatively to build a contiguous diffusion bonded or welded structure. Monolithic lasers provide numerous advantages for space flight solid-state lasers by minimizing misalignment concerns. The closed cavity is immune to contamination. The number of components is minimized thus increasing reliability. Bragg mirrors serve as the high reflector and output coupler thus minimizing optical coatings and coating damage. The Bragg mirrors also provide spectral and spatial mode selection for high fidelity. The monolithic structure allows short cavities resulting in short pulses. Passive saturable absorber Q-switches provide a soft aperture for spatial mode filtering and improved pointing stability. We will review our recent commercial and in-house developments toward fully monolithic solid-state lasers.

50W CW output power and 12mJ pulses from a quasi-2-level Yb:YAG ceramic rod laser end-pumped at the 969nm zero-phonon line

NASA Astrophysics Data System (ADS)

Fries, Christian; Weitz, Marco; Theobald, Christian; v. Löwis of Menar, Patric; Bartschke, Jürgen; L'huillier, Johannes A.

2015-02-01

With the advent of high power and narrow bandwidth 969 nm pump diodes, direct pumping into the upper laser level of Yb:YAG and hence quasi-2-level lasers became possible. Pumping directly into the emitting level leads to higher quantum efficiency and reduction of non-radiative decay. Consequently, thermal load, thermal lensing and risk of fracture are reduced significantly. Moreover pump saturation and thermal population of uninvolved energy-levels in ground and excited states are benefical for a homogenous distribution of the pump beam as well as the reduction of reabsorption loss compared to 3-level systems, which allows for high-power DPSS lasers. Beside continuous-wave (cw) operation, nanosecond pulses with a repetition rate between 1 and 5 kHz are an attractive alternative to flashlamp-pumped systems (10-100 Hz) in various measurement applications that require higher data acquisition rates because of new faster detectors. Based on measurements of the absorption and a detailed numerical model for pump beam distribution, including beam propagation and saturation factors, power-scaling of a ceramic rod Yb:YAG oscillator was possible. Finally a cw output power of 50 W with 33 % pump efficiency at 1030 nm has been demonstrated (M2 < 1.2). Nanosecond pulses have been produced by cavity-dumping of this system. The cavity-dumped setup allowed for 3-10 ns pulses with a pulse energy of 12.5 mJ at 1 kHz (M2 < 1.1). In order to achieve these results a systematic experimental and numerical investigation on gain dynamics and the identification of different stable operating regimes has been carried out.

Optimum conditions for producing Cs2 molecular condensates by stimulated Raman adiabatic passage

NASA Astrophysics Data System (ADS)

Feng, Zhifang; Li, Weidong; Wang, Lirong; Xiao, Liantuan; Jia, Suotang

2009-10-01

The optimum conditions for producing Cs2 molecular condensates from Cs atomic condensates with high transfer efficiency by stimulated Raman adiabatic passage are presented. Under the extended “two-photon” resonance condition, including the two-photon process, the mean-field correction, and the tunneling coupling between two upper excited molecular levels, a high and stable conversion efficiency is realized. The high conversion efficiency could be achieved by following two methods under experimentally less demanding conditions (relatively small effective Rabi frequency for pump laser pulse). One is adjusting the detuning difference between two laser pulses for same effective Rabi frequencies with up to 87.2% transfer efficiency. Another one is adjusting the effective Rabi frequency, the detuning of dump laser for given effective Rabi frequency, and the detuning of pump laser with up to 80.7% transfer efficiency.

Potassium titanyl arsenate based cascaded optical parametric oscillator emit at 2.5 µm derived by neodymium-doped yttrium lithium fluoride laser

NASA Astrophysics Data System (ADS)

Duan, Yanmin; Zhang, Jing; Guo, Junhong; Zhu, Haiyong; Zhang, Yongchang; Xu, Changwen; Wang, Hongyan; Zhang, Yaoju

2018-04-01

We reported a potassium titanyl arsenate (KTA) based cascaded optical parametric oscillator (OPO). The secondary OPO signal light at 2.5 µm was obtained with two OPO processes in one non-critical phase matching cut KTA crystal. This cascaded OPO was driven by a Q-switched neodymium-doped yttrium lithium fluoride (Nd:YLF) laser at 1047 nm. Making full use of the negative thermal lens effect and long upper level fluorescence lifetime of Nd:YLF, signal power of 605 mW at 2503 nm was achieved with a pulse repetition frequency of 15 kHz and an incident diode pump power of 9.7 W. Therefore, the cascaded OPO derived by Q-switched Nd:YLF laser could provide high peak power pulsed laser emission in mid-infrared band.

Craterlike structures on the laser cut surface

NASA Astrophysics Data System (ADS)

Shulyatyev, V. B.; Orishich, A. M.

2017-10-01

Analysis of the laser cut surface morphology remain topical. It is related with the fact that the surface roughness is the main index of the cut quality. The present paper deals with the experimental study of the relatively unstudied type of defects on the laser cut surface, dimples, or craters. According to the measurement results, amount of craters per unit of the laser cut surface area rises as the sheet thickness rises. The crater diameter rises together with the sheet thickness and distance from the upper sheet edge. The obtained data permit concluding that the defects like craters are observed predominantly in the case of thick sheets. The results agree with the hypothesis of crater formation as impact structures resulting from the melt drops getting on the cut channel walls upon separation from the cut front by the gas flow.

Process Properties of Electronic High Voltage Discharges Triggered by Ultra-short Pulsed Laser Filaments

NASA Astrophysics Data System (ADS)

Cvecek, Kristian; Gröschel, Benjamin; Schmidt, Michael

Remote processing of metallic workpieces by techniques based on electric arc discharge or laser irradiation for joining or cutting has a long tradition and is still being intensively investigated in present-day research. In applications that require high power processing, both approaches exhibit certain advantages and disadvantages that make them specific for a given task. While several hybrid approaches exist that try to combine the benefits of both techniques, none were as successful in providing a fixed electric discharge direction as discharges triggered by plasma filaments generated by ultra-short pulsed lasers. In this work we investigate spatial and temporal aspects of laser filament guided discharges and give an upper time delay between the filament creation and the electrical build-up of a dischargeable voltage for a successful filament triggered discharge.

Endoscopic palliation of esophageal and cardial cancer: Nd:YAG laser and prosthesis

NASA Astrophysics Data System (ADS)

Norberto, Lorenzo; Ranzato, Riccardo; Marino, Saverio; Angriman, Imerio; Vella, Vincenzo; Donadi, Michele; D'Amico, D. F.

1997-12-01

From November 1, 1992 to January 31, 1997, 227 patients with inoperable esophageal and cardial carcinomas were treated with Nd:YAG laser therapy and prosthesis intubation. The retrograde technique was used in most cases. The tumor involved in 75 pts the Cardia, in 65 the middle thoracic esophagus, in 47 pts the lower thoracic esophagus, in 23 in the upper thoracic esophagus and in 17 in the cervical esophagus. The indications for palliative Nd:YAG laser and prosthesis intubation were a locally advanced or metastatic tumor in 146 pts (64.4%) and poor surgical risk in 81 pts (35.6%). The quality of palliation was evaluated according to the ability to swallow. The mean survival rate of the patients during the follow up was 22 weeks for the laser therapy and 16 weeks for the prosthesis intubation.

Two-color surface-emitting lasers by a GaAs-based coupled multilayer cavity structure for coherent terahertz light sources

NASA Astrophysics Data System (ADS)

Lu, Xiangmeng; Ota, Hiroto; Kumagai, Naoto; Minami, Yasuo; Kitada, Takahiro; Isu, Toshiro

2017-11-01

Two-color surface-emitting lasers were fabricated using a GaAs-based coupled multilayer cavity structure grown by molecular beam epitaxy. InGaAs/GaAs multiple quantum wells were introduced only in the upper cavity for two-mode emission in the near-infrared region. Two-color lasing of the device was successfully demonstrated under pulsed current operations at room temperature. We also observed good temporal coherence of the two-color laser light using a Michelson interferometer. A coherent terahertz source is expected when a wafer-bonded coupled cavity consisting of (0 0 1) and non-(0 0 1) epitaxial films is used for the two-color laser device, in which the difference-frequency generation can be enabled by the second-order nonlinear response in the lower cavity.

Infrared technique for decoding of invisible laser markings

NASA Astrophysics Data System (ADS)

Haferkamp, Heinz; Jaeschke, Peter; Stein, Johannes; Goede, Martin

2002-03-01

Counterfeiting and product piracy continues to be an important issue not only for the Western industry, but also for the society in general. Due to the drastic increase in product imitation and the request for plagiarism protection as well as for reducing thefts there is a high interest in new protection methods providing new security features. The method presented here consists of security markings which are included below paint layers. These markings are invisible for the human eye due to the non-transparency of the upper layers in the visible spectral range. However, the markings can be detected by an infrared technique taking advantage on the partial transparency of the upper paint layers in the IR-region. Metal sheets are marked using laser radiation. The beam of a Nd:YAG-laser provides a modification of the surface structure, resulting in dark markings due to the annealing effect. After coating of the laser-marked material, the markings are invisible for the bare eye. In order to read out the invisible information below the coating, an infrared reflection technique is used. The samples are illuminated with halogen lamps or infrared radiators. Many coating materials (i. e. paints) show a certain transparency in the mid-infrared region, especially between 3 - 5 micrometers . The reflected radiation is detected using an IR-camera with a sensitivity range from 3.4 - 5 micrometers . Due to the different reflection properties between the markings and their surrounding, the information can be detected.

Development of laser-based techniques for in situ characterization of the first wall in ITER and future fusion devices

NASA Astrophysics Data System (ADS)

Philipps, V.; Malaquias, A.; Hakola, A.; Karhunen, J.; Maddaluno, G.; Almaviva, S.; Caneve, L.; Colao, F.; Fortuna, E.; Gasior, P.; Kubkowska, M.; Czarnecka, A.; Laan, M.; Lissovski, A.; Paris, P.; van der Meiden, H. J.; Petersson, P.; Rubel, M.; Huber, A.; Zlobinski, M.; Schweer, B.; Gierse, N.; Xiao, Q.; Sergienko, G.

2013-09-01

Analysis and understanding of wall erosion, material transport and fuel retention are among the most important tasks for ITER and future devices, since these questions determine largely the lifetime and availability of the fusion reactor. These data are also of extreme value to improve the understanding and validate the models of the in vessel build-up of the T inventory in ITER and future D-T devices. So far, research in these areas is largely supported by post-mortem analysis of wall tiles. However, access to samples will be very much restricted in the next-generation devices (such as ITER, JT-60SA, W7-X, etc) with actively cooled plasma-facing components (PFC) and increasing duty cycle. This has motivated the development of methods to measure the deposition of material and retention of plasma fuel on the walls of fusion devices in situ, without removal of PFC samples. For this purpose, laser-based methods are the most promising candidates. Their feasibility has been assessed in a cooperative undertaking in various European associations under EFDA coordination. Different laser techniques have been explored both under laboratory and tokamak conditions with the emphasis to develop a conceptual design for a laser-based wall diagnostic which is integrated into an ITER port plug, aiming to characterize in situ relevant parts of the inner wall, the upper region of the inner divertor, part of the dome and the upper X-point region.

TerraHertz Free Electron Laser Applications for Satellite Remote Sensing

NASA Technical Reports Server (NTRS)

Heaps, William S.

2003-01-01

The development of a Free Electron Laser (EL) operating in the terahertz frequency regime by the group at the University of Hawaii (Elias et al.) represents a significant new opportunity in the area of atmospheric remote sensing. The FEL has 2 salient features that create a unique opportunity. First of all it represents the only source in this frequency range with sufficient power to enable lidar instrumentation. Secondly its very high electrical efficiency (several times more efficient than any currently employed spaceborne laser) renders it a strong candidate for use in satellite remote sensing. On the negative side the atmosphere is rather strongly absorbing throughout this frequency range due primarily to the water vapor continuum absorption. This means that the instruments using this laser will not be able to access the lower troposphere because of its very high water concentration.. However the instrument will be very capable of measurements in the upper troposphere and stratosphere. A passive instrument, the Microwave Limb Sounder on the UARS satellite operated by Jet Propulsion Laboratory, has already demonstrated that this wavelength region can be used for chemical species with strong emission lines. A lidar would complement the capabilities of this instrument by providing the capability to measure absorbing species in the upper atmosphere. I will discuss the design of such an instrument in greater detail and estimate its performance in measuring a number of chemical species of interest to the Earth Science community.

Littrow-type external-cavity blue laser for holographic data storage.

PubMed

Tanaka, Tomiji; Takahashi, Kazuo; Sako, Kageyasu; Kasegawa, Ryo; Toishi, Mitsuru; Watanabe, Kenjiro; Samuels, David; Takeya, Motonobu

2007-06-10

An external-cavity laser with a wavelength of 405 nm and an output of 80 mW has been developed for holographic data storage. The laser has three states: the first is a perfect single mode, whose coherent length is 14 m; the second is a three-mode state with a coherent length of 3 mm; and the third is a six-mode state with a coherent length of 0.3 mm. The first and second states are available for angular-multiplexing recording; all states are available for coaxial multiplexing recording. Due to its short wavelength, the recording density is higher than that of a 532 nm laser.

[Technique of thulium laser in managing bladder cuff in nephroureterectomy for upper urinary tract urothelium carcinoma].

PubMed

Pang, Kun; Sun, Xiao-Wen; Liu, Shi-Bo; Li, Wei-Guo; Shao, Yi; Zhuo, Jian; Wei, Hai-Bin; Xia, Shu-Jie

2012-11-13

To explore the application of thulium laser (2 µm laser) in managing bladder cuff in nephroureterectomy for upper urinary tract urothelium carcinoma (UUT-UC). The medical records of 56 patients undergoing nephroureterectomy at our hospital were reviewed retrospectively. The operative indicators, oncologic outcomes and clinicopathologic data were compared among the groups of open surgery (Group A), electric coagulation (Group B) and thulium laser technique (Group C). Furthermore a model of burst pressure measurement was built to measure the different burst pressures of sealing distal ureter. The follow-up results: when the indicators of operative duration, intraoperative blood loss volume, removal time of drainage tube, removal time of catheter and hospital stays were compared among three groups, Group A had no statistical differences with Group B/C in terms of removal time of drainage tube and removal time of catheter. But significant statistical differences existed in terms of operative duration, intraoperative blood loss volume and hospital stays ((232 ± 52) vs (148 ± 47) and (130 ± 49) min, (358 ± 81) vs (136 ± 74) and (145 ± 70) ml, (13 ± 3) vs (11 ± 4) and (10 ± 3) d, all P < 0.05). No statistical differences existed between Groups B and C in terms of all the above indicators. Burst pressure measurement results: no statistical differences existed between Group C and B ((116 ± 21) vs (139 ± 32) cm H2O, P > 0.05). For the surgical treatment of UUT-UC, thulium laser technique has no difference in operation indicators and oncologic outcomes compared to open surgery. Besides, it has the advantages of improved spatial beam quality and more precise tissue incision.

Development of automatic pre-tracking system for fillet weld based on laser trigonometry

NASA Astrophysics Data System (ADS)

Shen, Xiaoqin; Yu, Fusheng

2005-01-01

In this paper, an automatic fillet weld pre-tracking system for welding the work piece of lorry back boards with several bend in haul automobile is developed basing on laser trigonometry. The optical measuring head based on laser-PSD trigonometry is used as position sensor. It is placed in front of the traveling direction of welding wire to get the distances from welding wire to the two side boards of the welding lines, upper board and bottom board of the fillet weld respectively. A chip of AT89S52 is used as the micro controller in this system. The AC servomotors, ball-screws and straight guide rails constitute the sliding table to take welding wire move. The laser-PSD sensors pass through the vertical board, upper board and bottom board of the fillet weld when welding wire moves and then get the distance. The laser-PSD sensors output the analog signals. After A/D conversion, the digital signal is input into AT89S52 and calculated. Then the information of the position and lateral deviation of the welding wire when welding a certain position are gotten to control welding wires. So the weld pre-tracking for welding the work piece with long distance and large bend in haul automobile is realized. The position information is input into EEPROM to be saved for short time after handled by AT89S52. The information is as the welding position information as well as the speed adjusting data of the welding wire when it welds the several bend of the work piece. The practice indicates that this system has high pre-tracking precision, good anti-disturb ability, excellent reliability, easy operating ability and good adaptability to the field of production.

The HALNA project: Diode-pumped solid-state laser for inertial fusion energy

NASA Astrophysics Data System (ADS)

Kawashima, T.; Ikegawa, T.; Kawanaka, J.; Miyanaga, N.; Nakatsuka, M.; Izawa, Y.; Matsumoto, O.; Yasuhara, R.; Kurita, T.; Sekine, T.; Miyamoto, M.; Kan, H.; Furukawa, H.; Motokoshi, S.; Kanabe, T.

2006-06-01

High-enery, rep.-rated, diode-pumped solid-state laser (DPSSL) is one of leading candidates for inertial fusion energy driver (IFE) and related laser-driven high-field applications. The project for the development of IFE laser driver in Japan, HALNA (High Average-power Laser for Nuclear Fusion Application) at ILE, Osaka University, aims to demonstrate 100-J pulse energy at 10 Hz rep. rate with 5 times diffraction limited beam quality. In this article, the advanced solid-state laser technologies for one half scale of HALNA (50 J, 10 Hz) are presented including thermally managed slab amplifier of Nd:phosphate glass and zig-zag optical geometry, and uniform, large-area diode-pumping.

Mode transition of plasma expansion for laser induced breakdown in Air

NASA Astrophysics Data System (ADS)

Shimamura, Kohei; Matsui, Kohei; Ofosu, Joseph A.; Yokota, Ippei; Komurasaki, Kimiya

2017-03-01

High-speed shadowgraph visualization experiments conducted using a 10 J pulse transversely excited atmospheric (TEA) CO2 laser in ambient air provided a state transition from overdriven to Chapman-Jouguet in the laser-supported detonation regime. At the state transition, the propagation velocity of the laser-supported detonation wave and the threshold laser intensity were 10 km/s and 1011 W/m2, respectively. State transition information, such as the photoionization caused by plasma UV radiation, of the avalanche ionization ahead of the ionization wave front can be elucidated from examination of the source seed electrons.

Grating enhanced solid-state laser amplifiers

DOEpatents

Erlandson, Alvin C.; Britten, Jerald A.

2010-11-09

A novel method and apparatus for suppressing ASE and parasitic oscillation modes in a high average power laser is introduced. Such an invention, as disclosed herein, uses diffraction gratings to increase gain, stored energy density, and pumping efficiency of solid-state laser gain media, such as, but not limited to rods, disks and slabs. By coupling predetermined gratings to solid-state gain media, such as crystal or ceramic laser gain media, ASE and parasitic oscillation modes can be effectively suppressed.

Partial ablation of stratum corneum by UV (193-nm) or IR (2.94-μm) pulsed lasers to enhance transdermal drug delivery rate

NASA Astrophysics Data System (ADS)

Fujiwara, Ai; Hinokitani, Toshihiro; Goto, Kenichi; Arai, Tsunenori

2004-07-01

To develop the noninvasive transdermal drug delivery system, pulsed lasers (argon-fluoride excimer laser (ArF laser) and erbium:yittrium aluminum garnet laser (Er:YAG laser)) were used to partially ablate the stratum corneum (SC), the upper layer of the skin. Because of the barrier function of the SC to drug permeation, the number of drugs especially macromolecules used in transdermal drug delivery system without skin irritation has been limited. Ultrastructural changes on the SC surface of ablated Yucatan micropig skin in vitro were observed with Environmental Scanning Electron Microscope. The result indicated that the structural changes varied according to each laser sources and irradiation conditions (laser fluences and numbers of pulses). Many granular structures of about 2 μm in diameter were observed in the ablated sites on ArF laser with lower fluence exposure (30 mJ/cm2, 200 pulses), and plane structures in the sites with higher fluence exposure (80 mJ/cm2, 80 pulses). In contrast, the ablation of Er:YAG laser created some pores of about 20 μm across on the surface of the SC. Under the irradiation condition of partial ablation, the skin permeability of macromolecule compound was enhanced. This partial SC ablation by pulsed laser could be possible candidate of the noninvasive transdermal drug delivery system with good physiological conditions of skin.

On pulse duration of self-terminating lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bokhan, P A

2011-02-28

The problem of the maximum pulse duration {tau}{sub max} of self-terminating lasers is considered. It is shown that the duration depends on the transition probability in the laser channel, on the decay rate of the resonant state in all other channels, and on the excitation rate of the metastable state. As a result, {tau}{sub max} is found to be significantly shorter than previously estimated. The criteria for converting the 'self-terminating' lasing to quasi-cw lasing are determined. It is shown that in the case of nonselective depopulation of the metastable state, for example in capillary lasers or in a fast flowmore » of the active medium gas, it is impossible to obtain continuous lasing. Some concrete examples are considered. It is established that in several studies of barium vapour lasers ({lambda} = 1.5 {mu}m) and nitrogen lasers ({lambda} = 337 nm), collisional lasing is obtained by increasing the relaxation rate of the metastable state in collisions with working particles (barium atoms and nitrogen molecules). (lasers)« less

Electron-hydrogen collisions in a laser field. (Reannouncement with new availability information)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, P.H.; Flannery, M.R.

1991-12-31

The Floquet treatment has already been successfully employed (Chu, Potvliege and Shakeshaft) in calculations of laser-induced multiphoton ionizations, where it provides dressed states for an atom in a laser field. The (perturbative) dressing of target states can have important consequences in laser-assisted scattering was illustrated by Byron and Joachain. These dressed states are useful, not only for laser-induced phenomena, but also as a collisional basis set for laser-assisted collisions. In this role they are in fact very appealing, since the Floquet treatment naturally lends itself to a time-independent analysis, and hence are compatible with present field-free scattering theories. Despite themore » apparent applicability of this approach, work along these lines has only just recently appeared (Sharma and Mohan, Smith and Flannery, Burke et al). Byron and Joachain have illustrated that perturbative dressing of the target states can have important consequences in laser-assisted scattering. Floquet dressing however provides a more complete description (Smith and Flannery).« less

Rapid Prototyping: State of the Art

DTIC Science & Technology

2003-10-23

Rapid Prototyping SCS Solid Creation System SLM Selective Laser Melting SLP Solid Laser diode Plotter SLS Selective Laser Sintering SOAR State of the...121,000, respectively. SLP stands for Sold Laser Diode Plotter. The machines are relatively slow and parts are small, so, to date, the products have been...Gigerenzer, H., “Directed Laser Welding of Metal Matrix Composite Structures for Space Based Applications,“ Triton Systems Inc., Chelmsford, MA., 1

Observation of motion of colloidal particles undergoing flowing Brownian motion using self-mixing laser velocimetry with a thin-slice solid-state laser.

PubMed

Sudo, S; Ohtomo, T; Otsuka, K

2015-08-01

We achieved a highly sensitive method for observing the motion of colloidal particles in a flowing suspension using a self-mixing laser Doppler velocimeter (LDV) comprising a laser-diode-pumped thin-slice solid-state laser and a simple photodiode. We describe the measurement method and the optical system of the self-mixing LDV for real-time measurements of the motion of colloidal particles. For a condensed solution, when the light scattered from the particles is reinjected into the solid-state laser, the laser output is modulated in intensity by the reinjected laser light. Thus, we can capture the motion of colloidal particles from the spectrum of the modulated laser output. For a diluted solution, when the relaxation oscillation frequency coincides with the Doppler shift frequency, f_d, which is related to the average velocity of the particles, the spectrum reflecting the motion of the colloidal particles is enhanced by the resonant excitation of relaxation oscillations. Then, the spectral peak reflecting the motion of colloidal particles appears at 2×f_d. The spectrum reflecting the motion of colloidal particles in a flowing diluted solution can be measured with high sensitivity, owing to the enhancement of the spectrum by the thin-slice solid-state laser.

High power diode lasers for solid-state laser pumps

NASA Technical Reports Server (NTRS)

Linden, Kurt J.; Mcdonnell, Patrick N.

1994-01-01

The development and commercial application of high power diode laser arrays for use as solid-state laser pumps is described. Such solid-state laser pumps are significantly more efficient and reliable than conventional flash-lamps. This paper describes the design and fabrication of diode lasers emitting in the 780 - 900 nm spectral region, and discusses their performance and reliability. Typical measured performance parameters include electrical-to-optical power conversion efficiencies of 50 percent, narrow-band spectral emission of 2 to 3 nm FWHM, pulsed output power levels of 50 watts/bar with reliability values of over 2 billion shots to date (tests to be terminated after 10 billion shots), and reliable operation to pulse lengths of 1 ms. Pulse lengths up to 5 ms have been demonstrated at derated power levels, and CW performance at various power levels has been evaluated in a 'bar-in-groove' laser package. These high-power 1-cm stacked-bar arrays are now being manufactured for OEM use. Individual diode laser bars, ready for package-mounting by OEM customers, are being sold as commodity items. Commercial and medical applications of these laser arrays include solid-state laser pumping for metal-working, cutting, industrial measurement and control, ranging, wind-shear/atmospheric turbulence detection, X-ray generation, materials surface cleaning, microsurgery, ophthalmology, dermatology, and dental procedures.

Light-driven phase shifter

DOEpatents

Early, James W.

1990-01-01

A light-driven phase shifter is provided for modulating a transmission light beam. A gaseous medium such as argon is provided with electron energy states excited to populate a metastable state. A tunable dye laser is selected with a wavelength effective to deplete the metastable electron state and may be intensity modulated. The dye laser is directed through the gaseous medium to define a first optical path having an index of refraction determined by the gaseous medium having a depleted metastable electron state. A transmission laser beam is also directed through the gaseous medium to define a second optical path at least partially coincident with the first optical path. The intensity of the dye laser beam may then be varied to phase modulate the transmission laser beam.

Integrated semiconductor twin-microdisk laser under mutually optical injection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zou, Ling-Xiu; Liu, Bo-Wen; Lv, Xiao-Meng

2015-05-11

We experimentally study the characteristics of an integrated semiconductor twin-microdisk laser under mutually optical injection through a connected optical waveguide. Based on the lasing spectra, four-wave mixing, injection locking, and period-two oscillation states are observed due to the mutually optical injection by adjusting the injected currents applied to the two microdisks. The enhanced 3 dB bandwidth is realized for the microdisk laser at the injection locking state, and photonic microwave is obtained from the electrode of the microdisk laser under the period-two oscillation state. The plentifully dynamical states similar as semiconductor lasers subject to external optical injection are realized due tomore » strong optical interaction between the two microdisks.« less

Novel application of an established technique for removing a knotted ureteric stent

PubMed Central

Tempest, Heidi; Turney, Ben; Kumar, Sunil

2011-01-01

This report describes a case whereby a ureteric stent became knotted during removal and lodged within the upper ureter. The authors describe a novel minimally invasive technique to remove the knotted ureteric stent using the holmium laser. PMID:22701009

Complex therapeutic-diagnostic endoscopy with laser irradiation and in-Situ spectrophotometry of erosive-ulcerative impairments of upper part of the gastrointestinal tract

NASA Astrophysics Data System (ADS)

Rogatkin, Dmitrii A.; Tereschenko, Sergey G.; Lapaeva, Ludmila G.; Gorenkov, Roman V.

2002-05-01

Today in the world there are a lot of effective methods to treat different disease with the use of low-level laser (LLL) radiation. And there are a number of well-known effective noninvasive optical diagnostic techniques, such as a laser fluorescence spectroscopy (LFS), elastic-scattering spectroscopy (ESS), absorption spectroscopy (ABSS), etc. In this paper the first experience of the complex laser-optical therapeutic-diagnostic treatment for the erosive-ulcerative impairments (EUI) of the upper part of the gastrointestinal tract (UPGT) are discussed. The EUI of the UPGT very often have a resistance to a medicamentous therapy and the treatment of that is very difficult in this case. The method of LLL irradiation through an endoscope has been used to increase the efficiency of LLL-therapy and to monitor a general process of recovery respectively. The standard biopsy was investigated to estimate the effect of care as well. As it is shown in this paper the in-situ ABSS allows to optimize the LLL treatment parameters for each patient and for each procedure if the laser has effect on a blood circulation in the irradiated zone. In this case the doctors can see the considerable effect and the reduction period of the cure for EUI. Otherwise, the ABSS indicates that there will be no any effect of LLL therapy for such patient and another methods of treatment are needed. The LFS in this case shows the absence of effect during the care course too. On the basis of analysis of the obtained results this paper presents our current understanding of mechanisms of the laser-induced fluorescence diagnostics and LLL therapy effect for EUI of the UPGT. Today this technique has the official approval of the Ministry of Health of Russian Federation.

Single-treatment skin tightening by radiofrequency and long-pulsed, 1064-nm Nd: YAG laser compared.

PubMed

Key, Douglas J

2007-02-01

To compare single-treatment facial skin tightening achieved with the current radiofrequency (RF) protocol with single-treatment tightening achieved with the long-pulsed, 1064-nm Nd:YAG laser. A total of 12 patients were treated with RF energy on one side of the face and laser energy on the other. Results were evaluated on a numerical scale (0-12 with 12 = greatest enhancement) from pre- and posttreatment photographs by a blinded panel. Upper face improvement (posttreatment score minus pretreatment score) was essentially the same on both sides (30.2 and 31.3% improvement for laser and RF, respectively, P=0.89). Lower face improvement was greater in the laser-treated side (35.7 and 23.8% improvement for laser and RF, respectively), but the difference was not significant (P=0.074). Overall face improvement was significantly greater on the laser-treated side (47.5 and 29.8% improvement for laser and RF, respectively, P=0.028). A single high-fluence treatment with the long-pulse 1064-nm Nd:YAG laser may improve skin laxity more than a single treatment with the RF device. Further controlled split-face or very large non-self controlled studies are needed to conclusively determine the relative efficacies of the two technologies. (c) 2007 Wiley-Liss, Inc.

Far-infrared vibration--rotation-tunneling spectroscopy of Ar--NH sub 3 : Intermolecular vibrations and effective angular potential energy surface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schmuttenmaer, C.A.; Cohen, R.C.; Loeser, J.G.

Two new intermolecular vibration--rotation-tunneling (VRT) bands of Ar--NH{sub 3} have been measured using tunable far infrared laser spectroscopy. We have unambiguously assigned these and a previously measured FIR band (Gwo {ital et} {ital al}., Mol. Phys. {bold 71}, 453 (1990)) as {Pi}(1{sub 0}, {ital n}=0){l arrow}{Sigma}(0{sub 0}, {ital n}=0), {Sigma}(1{sub 0}, {ital n}=0){l arrow}{Sigma}(0{sub 0}, {ital n}=0), and {Sigma}(0{sub 0}, {ital n}=1){l arrow}{Sigma}(0{sub 0}, {ital n}=0). The three upper states of these are found to be strongly mixed by anisotropy and Coriolis effects. A simultaneous least squares fit of all transitions has yielded vibrational frequencies, rotational and centrifugal distortion constants,more » and a Coriolis parameter as well as quadrupole hyperfine coupling constants for the upper states. An effective angular potential energy surface for Ar--NH{sub 3} in its lowest stretching state has been determined from these data, after explicitly accounting for the effects of bend stretch interactions. Features of the surface include a global minimum at the near T-shaped configuration ({theta}=90{degree}), a 30 cm{sup {minus}1} to 60 cm{sup {minus}1} barrier to rotation at {theta}=180{degree} (or 0{degree}), and a very low barrier or possibly a secondary minimum at {theta}=0{degree} (or 180{degree}). Both attractive and repulsive interactions are shown to contribute significantly to the anisotropic forces in the complex. Comparison with {ital ab} {ital initio} calculations are presented.« less

Theoretical studies of solar-pumped lasers

NASA Technical Reports Server (NTRS)

Harries, W. L.

1982-01-01

Solar-pumped lasers were investigated by comparing experimental results from pulse experiments with steady state calculations. The time varying behavior of an IBr laser is studied. The analysis is only approximate, but indicates that conditions occurring in a pulsed experiment are quite different from those at steady state. The possibility of steady-state lasing in an IBr laser is determined. The effects of high temperatures on the quenching and recombination rates are examined. Although uncertainties in the values of the rate coefficients make it difficult to draw firm conclusions, it seems steady state running may be possible at high temperatures.

Tunable femtosecond lasers with low pump thresholds

NASA Astrophysics Data System (ADS)

Oppo, Karen

The work in this thesis is concerned with the development of tunable, femtosecond laser systems, exhibiting low pump threshold powers. The main motive for this work was the development of a low threshold, self-modelocked Ti:Al2O3 laser in order to replace the conventional large-frame argon-ion pump laser with a more compact and efficient all-solid-state alternative. Results are also presented for an all-solid-state, self-modelocked Cr:LiSAF laser, however most of this work is concerned with self-modelocked Ti:Al2O3 laser systems. In chapter 2, the operation of a regeneratively-initiated, and a hard-aperture self- modelocked Ti:Al2O3 laser, pumped by an argon-ion laser, is discussed. Continuous- wave oscillation thresholds as low as 160mW have been demonstrated, along with self-modelocked threshold powers as low as 500mW. The measurement and suppression of phase noise on modelocked lasers is discussed in chapter 3. This is followed by a comparison of the phase noise characteristics of the regeneratively-initiated, and hard-aperture self-modelocked Ti:Al2O3 lasers. The use of a synchronously-operating, high resolution electron-optical streak camera in the evaluation of timing jitter is also presented. In chapter 4, the construction and self-modelocked operation of an all-solid-state Ti:Al2O3 laser is described. The all-solid-state alternative to the conventional argon-ion pump laser was a continuous-wave, intracavity-frequency doubled, diode-laser pumped Nd:YLF ring laser. At a total diode-laser pump power of 10W, this minilaser was capable of producing a single frequency output of 1W, at 523.5nm in a TEM00 beam. The remainder of this thesis looks at the operation of a self-modelocked Ti:Al2O3 laser generating ultrashort pulses at wavelengths as long as 1053nm. The motive for this work was the development of an all-solid-state, self- modelocked Ti:Al2O3 laser operating at 1053nm, for use as a master oscillator in a Nd:glass power chain.

Infrared laser system

DOEpatents

Cantrell, Cyrus D.; Carbone, Robert J.; Cooper, Ralph S.

1977-01-01

An infrared laser system and method for isotope separation may comprise a molecular gas laser oscillator to produce a laser beam at a first wavelength, Raman spin flip means for shifting the laser to a second wavelength, a molecular gas laser amplifier to amplify said second wavelength laser beam to high power, and optical means for directing the second wavelength, high power laser beam against a desired isotope for selective excitation thereof in a mixture with other isotopes. The optical means may include a medium which shifts the second wavelength high power laser beam to a third wavelength, high power laser beam at a wavelength coincidental with a corresponding vibrational state of said isotope and which is different from vibrational states of other isotopes in the gas mixture.

Infrared laser system

DOEpatents

Cantrell, Cyrus D.; Carbone, Robert J.; Cooper, Ralph

1982-01-01

An infrared laser system and method for isotope separation may comprise a molecular gas laser oscillator to produce a laser beam at a first wavelength, Raman spin flip means for shifting the laser to a second wavelength, a molecular gas laser amplifier to amplify said second wavelength laser beam to high power, and optical means for directing the second wavelength, high power laser beam against a desired isotope for selective excitation thereof in a mixture with other isotopes. The optical means may include a medium which shifts the second wavelength high power laser beam to a third wavelength, high power laser beam at a wavelength coincidental with a corresponding vibrational state of said isotope and which is different from vibrational states of other isotopes in the gas mixture.

In-Flight Performance of the Mercury Laser Altimeter Laser Transmitter

NASA Technical Reports Server (NTRS)

Yu, Anthony W.; Sun, Xiaoli; Li, Steven X.; Cavanaugh, John F.; Neumann, Gregory A.

2014-01-01

The Mercury Laser Altimeter (MLA) is one of the payload instruments on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft, which was launched on August 3, 2004. MLA maps Mercury's shape and topographic landforms and other surface characteristics using a diode-pumped solid-state laser transmitter and a silicon avalanche photodiode receiver that measures the round-trip time of individual laser pulses. The laser transmitter has been operating nominally during planetary flyby measurements and in orbit about Mercury since March 2011. In this paper, we review the MLA laser transmitter telemetry data and evaluate the performance of solid-state lasers under extended operation in a space environment.

High energy bursts from a solid state laser operated in the heat capacity limited regime

DOEpatents

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.

High energy bursts from a solid state laser operated in the heat capacity limited regime

DOEpatents

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.

Fault Scarp Detection Beneath Dense Vegetation Cover: Airborne Lidar Mapping of the Seattle Fault Zone, Bainbridge Island, Washington State

NASA Technical Reports Server (NTRS)

Harding, David J.; Berghoff, Gregory S.

2000-01-01

The emergence of a commercial airborne laser mapping industry is paying major dividends in an assessment of earthquake hazards in the Puget Lowland of Washington State. Geophysical observations and historical seismicity indicate the presence of active upper-crustal faults in the Puget Lowland, placing the major population centers of Seattle and Tacoma at significant risk. However, until recently the surface trace of these faults had never been identified, neither on the ground nor from remote sensing, due to cover by the dense vegetation of the Pacific Northwest temperate rainforests and extremely thick Pleistocene glacial deposits. A pilot lidar mapping project of Bainbridge Island in the Puget Sound, contracted by the Kitsap Public Utility District (KPUD) and conducted by Airborne Laser Mapping in late 1996, spectacularly revealed geomorphic features associated with fault strands within the Seattle fault zone. The features include a previously unrecognized fault scarp, an uplifted marine wave-cut platform, and tilted sedimentary strata. The United States Geologic Survey (USGS) is now conducting trenching studies across the fault scarp to establish ages, displacements, and recurrence intervals of recent earthquakes on this active fault. The success of this pilot study has inspired the formation of a consortium of federal and local organizations to extend this work to a 2350 square kilometer (580,000 acre) region of the Puget Lowland, covering nearly the entire extent (approx. 85 km) of the Seattle fault. The consortium includes NASA, the USGS, and four local groups consisting of KPUD, Kitsap County, the City of Seattle, and the Puget Sound Regional Council (PSRC). The consortium has selected Terrapoint, a commercial lidar mapping vendor, to acquire the data.

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.

A differential absorption lidar instrument for the measurment of carbon dioxide and methane in the lower troposphere (Conference Presentation)

NASA Astrophysics Data System (ADS)

Budinov, Daniel; Clements, Robert; Rae, Cameron F.; Moncrieff, John B.; Jack, James W.

2016-12-01

Developments in the remote detection of trace gases in the atmosphere using Differential Absorption Lidar have been driven largely by improvements in two key technologies: lasers and detectors. We have designed and built a narrow linewidth pulsed laser source with a well-controlled output wavelength and sufficient pulse energy to measure the concentration profile of CO2 and CH4 to a range in excess of 4km. We describe here the initial measurements of concentration profiles recorded with this instrument. The system is built around a custom-designed Newtonian telescope with a 40cm diameter primary mirror. Laser sources and detectors attach directly to the side of the telescope allowing for flexible customization with a range of additional equipment. The instrument features an all-solid-state laser source based on an optical parametric oscillator (OPO) pumped by an YLF based diode-laser pumped solid-state laser and seeded by a tuned DFB seed. This provides a range of available wavelengths suitable for DIAL within the 1.5-1.6 μm spectral region. The output of the OPO is beam expanded and transmitted coaxially from the receiver telescope. A gas cell within the laser source controls the seed wavelength and allows the wavelength to be tuned to match a specific absorption feature of the selected gas species. The source can be rapidly tuned between the on-line and off-line wavelengths to make a DIAL measurement of either CO2 or CH4 The receiver is based on an InGaAs avalanche photodetector. Whilst photodiode detectors are a low-cost solution their limited sensitivity restricts the maximum range over which a signal can be detected. The receiver signal is digitised for subsequent processing to produce a sightline concentration profile. The instrument is mounted on a robust gimballed mount providing full directional movement within the upper hemisphere. Both static pointing and angular scan modes are available. Accurate angular position is available giving the sightline vector and supporting the interpretation of the concentration profile. Initial measurements have been made in the planetary boundary layer above the City of Edinburgh and these will be presented and discussed. Earlier measurements demonstrated that the signal from atmospheric scatter could be detected at ranges in excess of 6km. The later measurements have shown scatter signals at greater ranges, but with increasing noise at the longer ranges. This is expected as the signal decreases with the inverse of the range whereas the noise remains effectively constant. Range resolved concentration profiles for sightline vectors lying within an angular sector have been used to create a 3D map of concentration for that volume. This will be presented and discussed.

Neural Control of the Upper Airway: Respiratory and State-Dependent Mechanisms

PubMed Central

Kubin, Leszek

2017-01-01

Upper airway muscles subserve many essential for survival orofacial behaviors, including their important role as accessory respiratory muscles. In the face of certain predisposition of craniofacial anatomy, both tonic and phasic inspiratory activation of upper airway muscles is necessary to protect the upper airway against collapse. This protective action is adequate during wakefulness, but fails during sleep which results in recurrent episodes of hypopneas and apneas, a condition known as the obstructive sleep apnea syndrome (OSA). Although OSA is almost exclusively a human disorder, animal models help unveil the basic principles governing the impact of sleep on breathing and upper airway muscle activity. This article discusses the neuroanatomy, neurochemistry, and neurophysiology of the different neuronal systems whose activity changes with sleep-wake states, such as the noradrenergic, serotonergic, cholinergic, orexinergic, histaminergic, GABAergic and glycinergic, and their impact on central respiratory neurons and upper airway motoneurons. Observations of the interactions between sleep-wake states and upper airway muscles in healthy humans and OSA patients are related to findings from animal models with normal upper airway, and various animal models of OSA, including the chronic-intermittent hypoxia model. Using a framework of upper airway motoneurons being under concurrent influence of central respiratory, reflex and state-dependent inputs, different neurotransmitters, and neuropeptides are considered as either causing a sleep-dependent withdrawal of excitation from motoneurons or mediating an active, sleep-related inhibition of motoneurons. Information about the neurochemistry of state-dependent control of upper airway muscles accumulated to date reveals fundamental principles and may help understand and treat OSA. PMID:27783860

Lidar investigations of ozone in the upper troposphere - lower stratosphere: technique and results of measurements

NASA Astrophysics Data System (ADS)

Romanovskii, O. A.; Burlakov, V. D.; Dolgii, S. I.; Nevzorov, A. A.; Nevzorov, A. V.; Kharchenko, O. V.

2016-12-01

Prediction of atmospheric ozone layer, which is the valuable and irreplaceable geo asset, is currently the important scientific and engineering problem. The relevance of the research is caused by the necessity to develop laser remote methods for sensing ozone to solve the problems of controlling the environment and climatology. The main aim of the research is to develop the technique for laser remote ozone sensing in the upper troposphere - lower stratosphere by differential absorption method for temperature and aerosol correction and analysis of measurement results. The report introduces the technique of recovering profiles of ozone vertical distribution considering temperature and aerosol correction in atmosphere lidar sounding by differential absorption method. The temperature correction of ozone absorption coefficients is introduced in the software to reduce the retrieval errors. The authors have determined wavelengths, promising to measure ozone profiles in the upper troposphere - lower stratosphere. We present the results of DIAL measurements of the vertical ozone distribution at the Siberian lidar station in Tomsk. Sensing is performed according to the method of differential absorption at wavelength pair of 299/341 nm, which are, respectively, the first and second Stokes components of SRS conversion of 4th harmonic of Nd:YAG laser (266 nm) in hydrogen. Lidar with receiving mirror 0.5 m in diameter is used to implement sensing of vertical ozone distribution in altitude range of 6-18 km. The recovered ozone profiles were compared with IASI satellite data and Kruger model. The results of applying the developed technique to recover the profiles of ozone vertical distribution considering temperature and aerosol correction in the altitude range of 6-18 km in lidar atmosphere sounding by differential absorption method confirm the prospects of using the selected wavelengths of ozone sensing 341 and 299 nm in the ozone lidar.

Intense Plasma Waveguide Terahertz Sources for High-Field THz Probe Science with Ultrafast Lasers for Solid State Physics

DTIC Science & Technology

2016-08-25

AFRL-AFOSR-UK-TR-2016-0029 Intense Plasma-Waveguide Terahertz Sources for High-Field THz probe science with ultrafast lasers for Solid State Physics...Plasma-Waveguide Terahertz Sources for High-Field THz probe science with ultrafast lasers for Solid State Physics, 5a.  CONTRACT NUMBER 5b.  GRANT...an existing high energy laser system, has been applied to the study of intense terahertz radiation generated in gaseous plasmas in purpose

Laser-assisted lipolysis for arm contouring in Teimourian grades I and II: a prospective study of 45 patients.

PubMed

Leclère, Franck Marie; Alcolea, Justo M; Vogt, Peter; Moreno-Moraga, Javier; Mordon, Serge; Casoli, Vincent; Trelles, Mario A

2015-04-01

Upper arm deformities secondary to weight loss or senile elastosis have led to an increased demand for aesthetic contouring procedures. We conducted this study to objectively assess if, in Teimourian low-grade upper arm remodelling, one session of laser-assisted lypolisis (LAL) could result in full patient satisfaction. Between 2011 and 2013, 45 patients were treated for unsightly fat arm Teimourian grade I (15 patients), grade IIa (15 patients) and grade IIb (15 patients) with one session of LAL. The laser used in this study was a 1470-nm diode laser (Alma Lasers, Cesarea, Israel) with the following parameters: continuous mode, 15 W power and transmission through a 600-μm optical fibre. Previous mathematical modelling suggested that 0.1 kJ was required in order to destroy 1 ml of fat. Treatment parameters and adverse effects were recorded.The arm circumference and skin pinch measurements were assessed pre and postoperatively. Patients were asked to file a satisfaction questionnaire. Pain during the anaesthesia and discomfort after the procedure were minimal. Complications included prolonged oedema in 11 patients. The average arm circumference decreased by 4.9 ± 0.4 cm in the right arm (p < 0.01) and 4.7 ± 0.5 cm in the left arm (p < 0.01) in grade I patients, 5.5 ± 0.6 cm in the right arm (p < 0.01) and 5.2 ± 0.5 cm in the left arm (p < 0.01) in grade IIa patients and 5.4 ± 0.5 cm in the right arm (p < 0.01) and 5.3 ± 0.5 cm in the left arm (p < 0.01) in grade IIB patients. The skin tightening effect was confirmed by the reduction of the skin calliper measurements in all three groups. Overall mean opinion of treatment was high for both patients and investigators. Of the 45 patients, all but one would recommend this treatment. A single session of LAL in upper arm remodelling for Teimourian grades I to IIb is a safe and reproducible technique. The procedure allows reduction in the amount of adipose deposits while providing full skin tightening.

Chaotic dynamics and synchronization in microchip solid-state lasers with optoelectronic feedback.

PubMed

Uchida, Atsushi; Mizumura, Keisuke; Yoshimori, Shigeru

2006-12-01

We experimentally observe the dynamics of a two-mode Nd:YVO4 microchip solid-state laser with optoelectronic feedback. The total laser output is detected and fed back to the injection current of the laser diode for pumping. Chaotic oscillations are observed in the microchip laser with optoelectronic self-feedback. We also observe the dynamics of two microchip lasers coupled mutually with optoelectronic link. The output of one laser is detected by a photodiode and the electronic signal converted from the laser output is sent to the pumping of the other laser. Chaotic fluctuation of the laser output is observed when the relaxation oscillation frequency is close to each other between the two microchip lasers. Synchronization of periodic wave form is also obtained when the microchip lasers have a single-longitudinal mode.

Exhaled ethane concentration in patients with cancer of the upper gastrointestinal tract - a proof of concept study.

PubMed

Abela, Jo Etienne; Skeldon, Kenneth D; Stuart, Robert C; Padgett, Miles J

2009-06-01

There has been growing interest in the measurement of breath ethane as an optimal non-invasive marker of oxidative stress. High concentrations of various breath alkanes including ethane have been reported in a number of malignancies. Our aim was to investigate the use of novel laser spectroscopy for rapid reporting of exhaled ethane and to determine whether breath ethane concentration is related to a diagnosis of upper gastrointestinal malignancy. Two groups of patients were recruited. Group A (n = 20) had a histo-pathological diagnosis of either esophageal or gastric malignancy. Group B (n = 10) was made up of healthy controls. Breath samples were collected from these subjects and the ethane concentration in these samples was subsequently measured to an accuracy of 0.2 parts per billion, ppb. Group A patients had a corrected exhaled breath ethane concentration of 2.3 +/- 0.8 (mean +/- SEM) ppb. Group B patients registered a mean of 3.1 +/- 0.5 ppb. There was no statistically significant difference between the two groups (p = 0.39). In conclusion, concentrations of ethane in collected breath samples were not significantly elevated in upper gastrointestinal malignancy. The laser spectroscopy system provided a reliable and rapid turnaround for breath sample analysis.

Make or Buy: An Analysis of the Impacts of 3D Printing Operations, 3D Laser Scanning Technology, and Collaborative Product Life-Cycle Management on Ship Maintenance and Modernization Cost Savings

DTIC Science & Technology

2015-04-30

team from the Naval Postgraduate School conducted a trade -off analysis of in-sourcing (i.e., make) versus outsourcing (i.e., buy) the production of... outsourced , fabricating parts involves an extensive acquisition process in addition to reverse engineering and manufacturing legacy replacement parts...upper left in Figure 1) is outsourcing to the original equipment manufacturer , “Organic” (upper right in Figure 1) is in-sourcing by the U.S

Confocal endomicroscopy for in vivo microscopic analysis of upper gastrointestinal tract premalignant and malignant lesions.

PubMed

Gheorghe, Cristian; Iacob, Razvan; Becheanu, Gabriel; Dumbrav Abreve, Mona

2008-03-01

Confocal LASER endomicroscopy (CLE) is a new endoscopic technique which allows subsurface in vivo microscopic analysis during ongoing endoscopy, using systemically or topically administered fluorescent agents. It allows targeted biopsies to be taken, potentially improving the diagnostic rate in certain gastrointestinal diseases. Worldwide experience with CLE for upper gastrointestinal malignant and premalignant lesions is still reduced. Potential clinical applications are presented, including diagnosis of NERD, Barrett's esophagus, atrophic gatritis, gastric intestinal metaplasia and dysplasia, gastric adenomatous or hyperplastic polyps, gastric cancer.

Generation of high-order Hermite-Gaussian modes in end-pumped solid-state lasers for square vortex array laser beam generation.

PubMed

Chu, Shu-Chun; Chen, Yun-Ting; Tsai, Ko-Fan; Otsuka, Kenju

2012-03-26

This study reports the first systematic approach to the excitation of all high-order Hermite-Gaussian modes (HGMs) in end-pumped solid-state lasers. This study uses a metal-wire-inserted laser resonator accompanied with the "off axis pumping" approach. This study presents numerical analysis of the excitation of HGMs in end-pumped solid-state lasers and experimentally generated HGM patterns. This study also experimentally demonstrates the generation of an square vortex array laser beams by passing specific high-order HGMs (HGn,n + 1 or HGn + 1,n modes) through a Dove prism-embedded unbalanced Mach-Zehnder interferometer [Optics Express 16, 19934-19949]. The resulting square vortex array laser beams with embedded vortexes aligned in a square array can be applied to multi-spot dark optical traps in the future.

Photorejuvenation: still not a fully established clinical tool for cosmetic treatment

NASA Astrophysics Data System (ADS)

Gong, Wei; Xie, Shusen; Li, Hui

2006-01-01

Several methods have been used to improve the esthetic appearance of photodamaged skin including dermabrasion, chemical peels and laser resurfacing using CO2 and Er:YAG laser. These procedures sacrifice epidermis, resulting in a long recuperation period and potential complications including persistent scarring, infection, hyperpigmentation, etc. Compared to ablative CO2 or Er:YAG laser resurfacing, non-ablative photorejuvenation technologies are playing an increasing role in the treatment of photodamaged skin. The clinical objective of which is to maximize thermal damage to upper dermis while minimizing injury to overlying skin. A variety of laser and non-laser systems have been used in the initial stage for this treatment. In our review, different treatment modalities have resulted in varying degrees of clinical effects. The basic mechanisms relate to improvement in employing non-ablative technologies are also discussed. Photorejuvenation is still not a fully established clinical tool for cosmetic treatment according to our review, therefore more research on basic mechanisms should be made.

Ablation of dermal and mucosal lesions with a new CO2 laser application system

NASA Astrophysics Data System (ADS)

Jovanovic, Sergije; Sedlmaier, Benedikt W.; Fuehrer, Ariane

1997-05-01

Laser treatment of skin changes has become common practice in recent years. The high absorption of the wavelength of the carbon-dioxide laser (10600 nm) is responsible for its low penetration depth in biological tissue. Shortening the exposure time minimizes thermic side effects such as carbonization and coagulation. This effect can be achieved with the SilkTouchTM scanner 767, since the focused laser beam is moved over a defined area by rapidly rotating mirrors. This enables controlled and reliable removal of certain dermal lesions, particularly hypertrophic scars, scars after common acne, wrinkles, rhinophyma and benign neoplasms like verruca vulgaris. Cosmetically favorable reepithelialization of the lasered surfaces results within a very short period of time. Benign mucosal changes of the upper aerodigestive tract can also be treated. Ablation is less traumatic for papillomas, fibromas, hyperplasias in the area of Waldeyer's tonsillar ring and certain laryngotracheal pathologies. Clinical examples demonstrate the advantages of this new mode of application.

Fabrication and optimization of 1.55-μm InGaAsP/InP high-power semiconductor diode laser

NASA Astrophysics Data System (ADS)

Qing, Ke; Shaoyang, Tan; Songtao, Liu; Dan, Lu; Ruikang, Zhang; Wei, Wang; Chen, Ji

2015-09-01

A comprehensive design optimization of 1.55-μm high power InGaAsP/InP board area lasers is performed aiming at increasing the internal quantum efficiency (ηi) while maintaining the low internal loss (αi) of the device, thereby achieving high power operation. Four different waveguide structures of broad area lasers were fabricated and characterized in depth. Through theoretical analysis and experiment verifications, we show that laser structures with stepped waveguide and thin upper separate confinement layer will result in high ηi and overall slope efficiency. A continuous wave (CW) single side output power of 160 mW was obtained for an uncoated laser with a 50-μm active area width and 1 mm cavity length. Project supported by the National Natural Science Foundation of China (Nos. 61274046, 61201103) and the National High Technology Research and Development Program of China (No. 2013AA014202).

Bernstein wave aided laser third harmonic generation in a plasma

NASA Astrophysics Data System (ADS)

Tyagi, Yachna; Tripathi, Deepak; Kumar, Ashok

2016-09-01

The process of Bernstein wave aided resonant third harmonic generation of laser in a magnetized plasma is investigated. The extra-ordinary mode (X-mode) laser of frequency ω 0 and wave number k → 0 , travelling across the magnetic field in a plasma, exerts a second harmonic ponderomotive force on the electrons imparting them an oscillatory velocity v → 2 ω0 , 2 k → 0 . This velocity beats with the density perturbation due to the Bernstein wave to produce a density perturbation at cyclotron frequency shifted second harmonic. The density perturbation couples with the oscillatory velocity v → ω0 , k → 0 of X-mode of the laser to produce the cyclotron frequency shifted third harmonic current density leading to harmonic radiation. The phase matching condition for the up shifted frequency is satisfied when the Bernstein wave is nearly counter-propagating to the laser. As the transverse wave number of the Bernstein wave is large, it is effective in the phase matched third harmonic generation, when the laser frequency is not too far from the upper hybrid frequency.

Bactericidal effect of Nd:YAG laser irradiation in endodontics

NASA Astrophysics Data System (ADS)

Aun, Carlos E.; Barberini, Alexandre F.; Camargo, Selma C. C.; Silva Kfouri, Luciana; Lorenzetti Simionato, Maria R.

1999-05-01

The success of endodontic therapy is based on the elimination of bacterial colonization from the endodontic system and periapical tissues. Recent studies have been showing the bactericidal effect of laser in root canal treatment. The propose of the study is to evaluate the effect of Nd:YAG laser irradiation in contaminated root canal treatment. The propose of the study is to evaluate the effect of Nd:YAG laser irradiation in contaminated root canals from upper central incisor. For the experiment 12 teeth were selected, respect at the apical third, sterilized, and 10 μm Streptococcus sanguis liquid culture were inoculated in the root canals. The laser test groups were irradiated with Nd:YAG laser at standard setting of 15Hz, 100mj and 1,5 W for 10, 20 and 30 seconds each in slow helicoidal movements from the apex to the top using a 300 micrometers fiber. After the procedure the specimens were placed in Tryptic Soy Agar, the number of colony forming units was evaluated. The experiment showed a significant reduction on viability of Streptococcus sanguis at the respective time of 20 and 30 seconds.

Radiation reabsorption in a laser-produced plasma

NASA Astrophysics Data System (ADS)

Brunner, W.; John, R. W.; Paul, H.; Steudel, H.

1988-11-01

Taking into account the emission and absorption of resonance radiation in a recombining laser-produced plasma of intermediate density, the system of rate equations for the population densities coupled with the radiative transfer equation is approximately treated. In the case of spatially varying absorption, an approximate form of the rate equation determining the population density of the upper resonance level is derived. By applying this relation to an axially symmetric plasma, a simple formula that describes the effect of radiation reabsorption on the spatial behavior of the population density is obtained.

Femtosecond laser-induced formation of submicrometer spikes on a semiconductor substrate

DOEpatents

Mazur, Eric [Concord, MA; Shen, Mengyan [Arlington, MA

2008-10-28

The present invention generally provides semiconductor substrates having submicron-sized surface features generated by irradiating the surface with ultra short laser pulses. In one aspect, a method of processing a semiconductor substrate is disclosed that includes placing at least a portion of a surface of the substrate in contact with a fluid, and exposing that surface portion to one or more femtosecond pulses so as to modify the topography of that portion. The modification can include, e.g., generating a plurality of submicron-sized spikes in an upper layer of the surface.

Femtosecond laser-induced formation of submicrometer spikes on a semiconductor substrate

DOEpatents

Mazur, Eric; Shen, Mengyan

2015-09-15

The present invention generally provides semiconductor substrates having submicronsized surface features generated by irradiating the surface with ultra short laser pulses. In one aspect, a method of processing a semiconductor substrate is disclosed that includes placing at least a portion of a surface of the substrate in contact with a fluid, and exposing that surface portion to one or more femtosecond pulses so as to modify the topography of that portion. The modification can include, e.g., generating a plurality of submicron-sized spikes in an upper layer of the surface.

Femtosecond laser-induced formation of submicrometer spikes on a semiconductor substrate

DOEpatents

Mazur, Eric , Shen; Mengyan, [Belmont, MA

2011-02-08

The present invention generally provides semiconductor substrates having submicron-sized surface features generated by irradiating the surface with ultra short laser pulses. In one aspect, a method of processing a semiconductor substrate is disclosed that includes placing at least a portion of a surface of the substrate in contact with a fluid, and exposing that surface portion to one or more femtosecond pulses so as to modify the topography of that portion. The modification can include, e.g., generating a plurality of submicron-sized spikes in an upper layer of the surface.

Materials Characterization of Additively Manufactured Components for Rocket Propulsion

NASA Technical Reports Server (NTRS)

Carter, Robert; Draper, Susan; Locci, Ivan; Lerch, Bradley; Ellis, David; Senick, Paul; Meyer, Michael; Free, James; Cooper, Ken; Jones, Zachary

2015-01-01

To advance Additive Manufacturing (AM) technologies for production of rocket propulsion components the NASA Glenn Research Center (GRC) is applying state of the art characterization techniques to interrogate microstructure and mechanical properties of AM materials and components at various steps in their processing. The materials being investigated for upper stage rocket engines include titanium, copper, and nickel alloys. Additive manufacturing processes include laser powder bed, electron beam powder bed, and electron beam wire fed processes. Various post build thermal treatments, including Hot Isostatic Pressure (HIP), have been studied to understand their influence on microstructure, mechanical properties, and build density. Micro-computed tomography, electron microscopy, and mechanical testing in relevant temperature environments has been performed to develop relationships between build quality, microstructure, and mechanical performance at temperature. A summary of GRC's Additive Manufacturing roles and experimental findings will be presented.

Material Characterization of Additively Manufactured Components for Rocket Propulsion

NASA Technical Reports Server (NTRS)

Carter, Robert; Draper, Susan; Locci, Ivan; Lerch, Bradley; Ellis, David; Senick, Paul; Meyer, Michael; Free, James; Cooper, Ken; Jones, Zachary

2015-01-01

To advance Additive Manufacturing (AM) technologies for production of rocket propulsion components the NASA Glenn Research Center (GRC) is applying state of the art characterization techniques to interrogate microstructure and mechanical properties of AM materials and components at various steps in their processing. The materials being investigated for upper stage rocket engines include titanium, copper, and nickel alloys. Additive manufacturing processes include laser powder bed, electron beam powder bed, and electron beam wire fed processes. Various post build thermal treatments, including Hot Isostatic Pressure (HIP), have been studied to understand their influence on microstructure, mechanical properties, and build density. Micro-computed tomography, electron microscopy, and mechanical testing in relevant temperature environments has been performed to develop relationships between build quality, microstructure, and mechanical performance at temperature. A summary of GRCs Additive Manufacturing roles and experimental findings will be presented.

Wetting properties of hybrid structure with hydrophilic ridges and hydrophobic channels

NASA Astrophysics Data System (ADS)

Lee, Dong-Ki; Choi, Su Young; Park, Min Soo; Cho, Young Hak

2018-02-01

In the present study, we fabricated a hybrid structure where the upper surface of the ridge is hydrophilic and the inner surface of the channel is hydrophobic. Laser-induced backside wet etching (LIBWE) process was performed to machine the hybrid structure on a Pyrex glass substrate. Wetting properties were evaluated from static contact angles (CAs) measurement in parallel and orthogonal directions. The water droplet on the hybrid structure was in the Cassie-Baxter state and showed anisotropic wetting property along groove lines. Moisture condensation studies under humid condition indicated that water droplets grew and coalesced on the ridge with hydrophilicity. Furthermore, water-oil separation was tested using a microfluidic chip with the developed hybrid structure. In case of hybrid microfluidic chip, the water could not flow into channel but the hexadecane could flow due to the capillary pressure difference.

Relict Landscape Response to Knickpoint Migration on the Roan Plateau, Western Colorado, Explored Through ALSM Data Analysis

NASA Astrophysics Data System (ADS)

Berlin, M. M.; Anderson, R. S.

2007-12-01

The unprecedented spatial resolution of Digital Elevation Models (DEMs) derived from Airborne Laser Swath Mapping (ALSM) makes them ideal for detecting subtle morphologic features. We explore to what extent information about knickpoint migration is communicated upstream by analyzing an ASLM-derived DEM in a transient landscape. We target the Roan Plateau in western Colorado, a landscape developed in flat-lying Eocene shales, in which multiple upstream-migrating waterfalls triggered by base level fall have incised dramatic canyons in their wake. The waterfalls separate low-gradient, bedrock-floored reaches above the waterfalls from steep, boulder-choked canyons below. Similarly, a sheer canyon rim separates a smooth, relict landscape above the canyon walls from the steep cliffs and talus-mantled slopes below. Waterfall and canyon rim elevations correlate well with the outcrop of a resistant oil-shale layer. We use a 1-meter DEM to develop two simple metrics that detect channel and hillslope response of the upper landscape to knickpoint migration. The first metric is stream profile analysis of upper plateau tributaries. In a steady-state stream channel, slope should decrease with distance downstream, as drainage area and the associated water discharge increase. Departures from this trend can be attributed to either lithologic variation, or transient oversteepening that may be associated with the presence of the waterfall. Oversteepening of the channel can incite hillslope response, and give rise to a box canyon upstream of the waterfall. We document the slope of channels as they approach the free overfall, and the presence and lengths of box canyons upstream of the waterfall lip. The second metric is the curvature of plateau hilltops. In a steady state landscape, hilltops should be roughly parabolic in cross-section, reflecting a balance between a uniform rate of regolith production and diffusive transport at all points along the hillslope. Departure from this parabolic form can reflect lithologic variation, transient hillslope response to increased rates of stream incision, or transport processes that are not linearly dependent on slope. Isolation of roughly the upper 100 m of hilltops and evaluation of the curvature of these crests provides constraint on the ratio of weathering rate to transport efficiency in the landscape most likely to be in steady state. Changes in crest curvature with distance from the canyon rim can be used to document transient hillslope response of the upper plateau surface in areas with uniform lithology. Paired with field observations and mapped bedrock contacts, analysis of an ASLM-derived DEM allows us to evaluate the extent to which the upper plateau channels and hillslopes have responded to knickpoint migration and the carving of canyons downstream. Morphologic evidence for significant upper plateau response to this incision event would suggest that the timescale for landscape adjustment to base level fall may be shorter than that required to propagate a knickpoint upstream.

Development of State of the Art Solid State Lasers for Altimetry and other LIDAR Applications

NASA Technical Reports Server (NTRS)

Kay, Richard B.

1997-01-01

This report describes work performed and research accomplished through the end of 1997. During this time period, we have designed and fabricated two lasers for flight LIDAR applications to medium altitudes (Laser Vegetation Imaging System designs LVIS 1 and LVIS 2), designed one earth orbiting LIDAR transmitter (VCL-Alt), and continued work on a high rep-rate LIDAR laser (Raster Scanned Altimeter, RASCAL). Additionally, a 'White Paper' was prepared which evaluates the current state of the art of Nd:YAG lasers and projects efficiencies to the year 2004. This report is attached as Appendix 1 of this report.

Distribution Analysis of Anthocyanins, Sugars, and Organic Acids in Strawberry Fruits Using Matrix-Assisted Laser Desorption/Ionization-Imaging Mass Spectrometry.

PubMed

Enomoto, Hirofumi; Sato, Kei; Miyamoto, Koji; Ohtsuka, Akira; Yamane, Hisakazu

2018-05-16

Anthocyanins, sugars, and organic acids contribute to the appearance, health benefits, and taste of strawberries. However, their spatial distribution in the ripe fruit has been fully unrevealed. Therefore, we performed matrix-assisted laser desorption/ionization, MALDI-IMS, analysis to investigate their spatial distribution in ripe strawberries. The detection sensitivity was improved by using the TM-Sprayer for matrix application. In the receptacle, pelargonidins were distributed in the skin, cortical, and pith tissues, whereas cyanidins and delphinidins were slightly localized in the skin. In the achene, mainly cyanidins were localized in the outside of the skin. Citric acid was mainly distributed in the upper and bottom side of cortical tissue. Although hexose was distributed almost equally throughout the fruits, sucrose was mainly distributed in the upper side of cortical and pith tissues. These results suggest that using the TM-Sprayer in MALDI-IMS was useful for microscopic distribution analysis of anthocyanins, sugars, and organic acids in strawberries.

Search for gravitational waves from compact binary coalescence in LIGO and Virgo data from S5 and VSR1

NASA Astrophysics Data System (ADS)

Abadie, J.; Abbott, B. P.; Abbott, R.; Abernathy, M.; Accadia, T.; Acernese, F.; Adams, C.; Adhikari, R.; Ajith, P.; Allen, B.; Allen, G.; Amador Ceron, E.; Amin, R. S.; Anderson, S. B.; Anderson, W. G.; Antonucci, F.; Arain, M. A.; Araya, M.; Aronsson, M.; Arun, K. G.; Aso, Y.; Aston, S.; Astone, P.; Atkinson, D. E.; Aufmuth, P.; Aulbert, C.; Babak, S.; Baker, P.; Ballardin, G.; Ballinger, T.; Ballmer, S.; Barker, D.; Barnum, S.; Barone, F.; Barr, B.; Barriga, P.; Barsotti, L.; Barsuglia, M.; Barton, M. A.; Bartos, I.; Bassiri, R.; Bastarrika, M.; Bauchrowitz, J.; Bauer, Th. S.; Behnke, B.; Beker, M. G.; Belletoile, A.; Benacquista, M.; Bertolini, A.; Betzwieser, J.; Beveridge, N.; Beyersdorf, P. T.; Bigotta, S.; Bilenko, I. A.; Billingsley, G.; Birch, J.; Birindelli, S.; Biswas, R.; Bitossi, M.; Bizouard, M. A.; Black, E.; Blackburn, J. K.; Blackburn, L.; Blair, D.; Bland, B.; Blom, M.; Boccara, C.; Bock, O.; Bodiya, T. P.; Bondarescu, R.; Bondu, F.; Bonelli, L.; Bonnand, R.; Bork, R.; Born, M.; Bose, S.; Bosi, L.; Bouhou, B.; Boyle, M.; Braccini, S.; Bradaschia, C.; Brady, P. R.; Braginsky, V. B.; Brau, J. E.; Breyer, J.; Bridges, D. O.; Brillet, A.; Brinkmann, M.; Brisson, V.; Britzger, M.; Brooks, A. F.; Brown, D. A.; Budzyński, R.; Bulik, T.; Bulten, H. J.; Buonanno, A.; Burguet–Castell, J.; Burmeister, O.; Buskulic, D.; Buy, C.; Byer, R. L.; Cadonati, L.; Cagnoli, G.; Cain, J.; Calloni, E.; Camp, J. B.; Campagna, E.; Campsie, P.; Cannizzo, J.; Cannon, K. C.; Canuel, B.; Cao, J.; Capano, C.; Carbognani, F.; Caudill, S.; Cavaglià, M.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cepeda, C.; Cesarini, E.; Chalermsongsak, T.; Chalkley, E.; Charlton, P.; Chassande-Mottin, E.; Chelkowski, S.; Chen, Y.; Chincarini, A.; Christensen, N.; Chua, S. S. Y.; Chung, C. T. Y.; Clark, D.; Clark, J.; Clayton, J. H.; Cleva, F.; Coccia, E.; Colacino, C. N.; Colas, J.; Colla, A.; Colombini, M.; Conte, R.; Cook, D.; Corbitt, T. R.; Cornish, N.; Corsi, A.; Costa, C. A.; Coulon, J.-P.; Coward, D.; Coyne, D. C.; Creighton, J. D. E.; Creighton, T. D.; Cruise, A. M.; Culter, R. M.; Cumming, A.; Cunningham, L.; Cuoco, E.; Dahl, K.; Danilishin, S. L.; Dannenberg, R.; D'Antonio, S.; Danzmann, K.; Das, K.; Dattilo, V.; Daudert, B.; Davier, M.; Davies, G.; Davis, A.; Daw, E. J.; Day, R.; Dayanga, T.; de Rosa, R.; Debra, D.; Degallaix, J.; Del Prete, M.; Dergachev, V.; Derosa, R.; Desalvo, R.; Devanka, P.; Dhurandhar, S.; di Fiore, L.; di Lieto, A.; di Palma, I.; di Paolo Emilio, M.; di Virgilio, A.; Díaz, M.; Dietz, A.; Donovan, F.; Dooley, K. L.; Doomes, E. E.; Dorsher, S.; Douglas, E. S. D.; Drago, M.; Drever, R. W. P.; Driggers, J. C.; Dueck, J.; Dumas, J.-C.; Eberle, T.; Edgar, M.; Edwards, M.; Effler, A.; Ehrens, P.; Ely, G.; Engel, R.; Etzel, T.; Evans, M.; Evans, T.; Fafone, V.; Fairhurst, S.; Fan, Y.; Farr, B. F.; Fazi, D.; Fehrmann, H.; Feldbaum, D.; Ferrante, I.; Fidecaro, F.; Finn, L. S.; Fiori, I.; Flaminio, R.; Flanigan, M.; Flasch, K.; Foley, S.; Forrest, C.; Forsi, E.; Fotopoulos, N.; Fournier, J.-D.; Franc, J.; Frasca, S.; Frasconi, F.; Frede, M.; Frei, M.; Frei, Z.; Freise, A.; Frey, R.; Fricke, T. T.; Friedrich, D.; Fritschel, P.; Frolov, V. V.; Fulda, P.; Fyffe, M.; Galimberti, M.; Gammaitoni, L.; Garofoli, J. A.; Garufi, F.; Gemme, G.; Genin, E.; Gennai, A.; Ghosh, S.; Giaime, J. A.; Giampanis, S.; Giardina, K. D.; Giazotto, A.; Gill, C.; Goetz, E.; Goggin, L. M.; González, G.; Goßler, S.; Gouaty, R.; Graef, C.; Granata, M.; Grant, A.; Gras, S.; Gray, C.; Greenhalgh, R. J. S.; Gretarsson, A. M.; Greverie, C.; Grosso, R.; Grote, H.; Grunewald, S.; Guidi, G. M.; Gustafson, E. K.; Gustafson, R.; Hage, B.; Hall, P.; Hallam, J. M.; Hammer, D.; Hammond, G.; Hanks, J.; Hanna, C.; Hanson, J.; Harms, J.; Harry, G. M.; Harry, I. W.; Harstad, E. D.; Haughian, K.; Hayama, K.; Hayau, J.-F.; Hayler, T.; Heefner, J.; Heitmann, H.; Hello, P.; Heng, I. S.; Heptonstall, A.; Hewitson, M.; Hild, S.; Hirose, E.; Hoak, D.; Hodge, K. A.; Holt, K.; Hosken, D. J.; Hough, J.; Howell, E.; Hoyland, D.; Huet, D.; Hughey, B.; Husa, S.; Huttner, S. H.; Huynh–Dinh, T.; Ingram, D. R.; Inta, R.; Isogai, T.; Ivanov, A.; Jaranowski, P.; Johnson, W. W.; Jones, D. I.; Jones, G.; Jones, R.; Ju, L.; Kalmus, P.; Kalogera, V.; Kandhasamy, S.; Kanner, J.; Katsavounidis, E.; Kawabe, K.; Kawamura, S.; Kawazoe, F.; Kells, W.; Keppel, D. G.; Khalaidovski, A.; Khalili, F. Y.; Khazanov, E. A.; Kim, H.; King, P. J.; Kinzel, D. L.; Kissel, J. S.; Klimenko, S.; Kondrashov, V.; Kopparapu, R.; Koranda, S.; Kowalska, I.; Kozak, D.; Krause, T.; Kringel, V.; Krishnamurthy, S.; Krishnan, B.; Królak, A.; Kuehn, G.; Kullman, J.; Kumar, R.; Kwee, P.; Landry, M.; Lang, M.; Lantz, B.; Lastzka, N.; Lazzarini, A.; Leaci, P.; Leong, J.; Leonor, I.; Leroy, N.; Letendre, N.; Li, J.; Li, T. G. F.; Lin, H.; Lindquist, P. E.; Lockerbie, N. A.; Lodhia, D.; Lorenzini, M.; Loriette, V.; Lormand, M.; Losurdo, G.; Lu, P.; Luan, J.; Lubiński, M.; Lucianetti, A.; Lück, H.; Lundgren, A.; Machenschalk, B.; Macinnis, M.; Mageswaran, M.; Mailand, K.; Majorana, E.; Mak, C.; Maksimovic, I.; Man, N.; Mandel, I.; Mandic, V.; Mantovani, M.; Marchesoni, F.; Marion, F.; Márka, S.; Márka, Z.; Maros, E.; Marque, J.; Martelli, F.; Martin, I. W.; Martin, R. M.; Marx, J. N.; Mason, K.; Masserot, A.; Matichard, F.; Matone, L.; Matzner, R. A.; Mavalvala, N.; McCarthy, R.; McClelland, D. E.; McGuire, S. C.; McIntyre, G.; McIvor, G.; McKechan, D. J. A.; Meadors, G.; Mehmet, M.; Meier, T.; Melatos, A.; Melissinos, A. C.; Mendell, G.; Menéndez, D. F.; Mercer, R. A.; Merill, L.; Meshkov, S.; Messenger, C.; Meyer, M. S.; Miao, H.; Michel, C.; Milano, L.; Miller, J.; Minenkov, Y.; Mino, Y.; Mitra, S.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Moe, B.; Mohan, M.; Mohanty, S. D.; Mohapatra, S. R. P.; Moraru, D.; Moreau, J.; Moreno, G.; Morgado, N.; Morgia, A.; Mors, K.; Mosca, S.; Moscatelli, V.; Mossavi, K.; Mours, B.; Mowlowry, C.; Mueller, G.; Mukherjee, S.; Mullavey, A.; Müller-Ebhardt, H.; Munch, J.; Murray, P. G.; Nash, T.; Nawrodt, R.; Nelson, J.; Neri, I.; Newton, G.; Nishida, E.; Nishizawa, A.; Nocera, F.; Nolting, D.; Ochsner, E.; O'Dell, J.; Ogin, G. H.; Oldenburg, R. G.; O'Reilly, B.; O'Shaughnessy, R.; Osthelder, C.; Ottaway, D. J.; Ottens, R. S.; Overmier, H.; Owen, B. J.; Page, A.; Pagliaroli, G.; Palladino, L.; Palomba, C.; Pan, Y.; Pankow, C.; Paoletti, F.; Papa, M. A.; Pardi, S.; Pareja, M.; Parisi, M.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Patel, P.; Pathak, D.; Pedraza, M.; Pekowsky, L.; Penn, S.; Peralta, C.; Perreca, A.; Persichetti, G.; Pichot, M.; Pickenpack, M.; Piergiovanni, F.; Pietka, M.; Pinard, L.; Pinto, I. M.; Pitkin, M.; Pletsch, H. J.; Plissi, M. V.; Poggiani, R.; Postiglione, F.; Prato, M.; Predoi, V.; Price, L. R.; Prijatelj, M.; Principe, M.; Prix, R.; Prodi, G. A.; Prokhorov, L.; Puncken, O.; Punturo, M.; Puppo, P.; Quetschke, V.; Raab, F. J.; Rabeling, D. S.; Radke, T.; Radkins, H.; Raffai, P.; Rakhmanov, M.; Rankins, B.; Rapagnani, P.; Raymond, V.; Re, V.; Reed, C. M.; Reed, T.; Regimbau, T.; Reid, S.; Reitze, D. H.; Ricci, F.; Riesen, R.; Riles, K.; Roberts, P.; Robertson, N. A.; Robinet, F.; Robinson, C.; Robinson, E. L.; Rocchi, A.; Roddy, S.; Röver, C.; Rolland, L.; Rollins, J.; Romano, J. D.; Romano, R.; Romie, J. H.; Rosińska, D.; Rowan, S.; Rüdiger, A.; Ruggi, P.; Ryan, K.; Sakata, S.; Sakosky, M.; Salemi, F.; Sammut, L.; Sancho de La Jordana, L.; Sandberg, V.; Sannibale, V.; Santamaría, L.; Santostasi, G.; Saraf, S.; Sassolas, B.; Sathyaprakash, B. S.; Sato, S.; Satterthwaite, M.; Saulson, P. R.; Savage, R.; Schilling, R.; Schnabel, R.; Schofield, R.; Schulz, B.; Schutz, B. F.; Schwinberg, P.; Scott, J.; Scott, S. M.; Searle, A. C.; Seifert, F.; Sellers, D.; Sengupta, A. S.; Sentenac, D.; Sergeev, A.; Shaddock, D.; Shapiro, B.; Shawhan, P.; Shoemaker, D. H.; Sibley, A.; Siemens, X.; Sigg, D.; Singer, A.; Sintes, A. M.; Skelton, G.; Slagmolen, B. J. J.; Slutsky, J.; Smith, J. R.; Smith, M. R.; Smith, N. D.; Somiya, K.; Sorazu, B.; Speirits, F. C.; Sperandio, L.; Stein, A. J.; Stein, L. C.; Steinlechner, S.; Steplewski, S.; Stochino, A.; Stone, R.; Strain, K. A.; Strigin, S.; Stroeer, A.; Sturani, R.; Stuver, A. L.; Summerscales, T. Z.; Sung, M.; Susmithan, S.; Sutton, P. J.; Swinkels, B.; Talukder, D.; Tanner, D. B.; Tarabrin, S. P.; Taylor, J. R.; Taylor, R.; Thomas, P.; Thorne, K. A.; Thorne, K. S.; Thrane, E.; Thüring, A.; Titsler, C.; Tokmakov, K. V.; Toncelli, A.; Tonelli, M.; Torre, O.; Torres, C.; Torrie, C. I.; Tournefier, E.; Travasso, F.; Traylor, G.; Trias, M.; Trummer, J.; Tseng, K.; Turner, L.; Ugolini, D.; Urbanek, K.; Vahlbruch, H.; Vaishnav, B.; Vajente, G.; Vallisneri, M.; van den Brand, J. F. J.; van den Broeck, C.; van der Putten, S.; van der Sluys, M. V.; van Veggel, A. A.; Vass, S.; Vaulin, R.; Vavoulidis, M.; Vecchio, A.; Vedovato, G.; Veitch, J.; Veitch, P. J.; Veltkamp, C.; Verkindt, D.; Vetrano, F.; Viceré, A.; Villar, A.; Vinet, J.-Y.; Vocca, H.; Vorvick, C.; Vyachanin, S. P.; Waldman, S. J.; Wallace, L.; Wanner, A.; Ward, R. L.; Was, M.; Wei, P.; Weinert, M.; Weinstein, A. J.; Weiss, R.; Wen, L.; Wen, S.; Wessels, P.; West, M.; Westphal, T.; Wette, K.; Whelan, J. T.; Whitcomb, S. E.; White, D. J.; Whiting, B. F.; Wilkinson, C.; Willems, P. A.; Williams, L.; Willke, B.; Winkelmann, L.; Winkler, W.; Wipf, C. C.; Wiseman, A. G.; Woan, G.; Wooley, R.; Worden, J.; Yakushin, I.; Yamamoto, H.; Yamamoto, K.; Yeaton-Massey, D.; Yoshida, S.; Yu, P. P.; Yvert, M.; Zanolin, M.; Zhang, L.; Zhang, Z.; Zhao, C.; Zotov, N.; Zucker, M. E.; Zweizig, J.

2010-11-01

We report the results of the first search for gravitational waves from compact binary coalescence using data from the Laser Interferometer Gravitational-Wave Observatory and Virgo detectors. Five months of data were collected during the Laser Interferometer Gravitational-Wave Observatory’s S5 and Virgo’s VSR1 science runs. The search focused on signals from binary mergers with a total mass between 2 and 35M⊙. No gravitational waves are identified. The cumulative 90%-confidence upper limits on the rate of compact binary coalescence are calculated for nonspinning binary neutron stars, black hole-neutron star systems, and binary black holes to be 8.7×10-3yr-1L10-1, 2.2×10-3yr-1L10-1, and 4.4×10-4yr-1L10-1, respectively, where L10 is 1010 times the blue solar luminosity. These upper limits are compared with astrophysical expectations.

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.

High-energy long duration frequency-doubled Nd:YAG laser and application to venous occlusion

NASA Astrophysics Data System (ADS)

Zhang, Laiming; Yang, Guilong; Li, Dianjun; Lu, Qipeng; Gu, Huadong; Zhu, Linlin; Zhao, Zhenwu; Li, Xin; Tang, Yuguo; Guo, Jin

2005-01-01

Laser treatment represents an attractive option to other methods of vessel diseases especially varicose veins. A long pulse (30~50ms) 532nm laser (Fig.1) is used in our experiments with the pulse duration matching the thermal relaxation time of the vessels and the green laser matching the absorption spectrum peak of the blood. Laser irradiates nude vein vessels directly or exterior skin to finish operation faster and to acquire the practical data for upper enteron varicose vein treatment in several animal experiments performed in vivo. The 5J-energy pulse allows us to finely occlude rabbit or dog"s vein vessels up to 2 mm in diameter when irradiating them off external skin (Fig.2). Blood vessels are occluded at once and later biopsy specimens show the immediate and long-term lasting occlusion effect. While irradiating vessels directly (Fig.3), the vessels are usually irradiated to perforate, detailed causes are still under investigation. Animal experiments show long pulse green laser therapy is a safe and effective solution to the vein"s occlusion, which promises such laser with high energy of each pulse and 30~50 ms duration is an ideal candidate for vessel diseases treatment.

Stability of quantum-dot excited-state laser emission under simultaneous ground-state perturbation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaptan, Y., E-mail: yuecel.kaptan@physik.tu-berlin.de; Herzog, B.; Schöps, O.

2014-11-10

The impact of ground state amplification on the laser emission of In(Ga)As quantum dot excited state lasers is studied in time-resolved experiments. We find that a depopulation of the quantum dot ground state is followed by a drop in excited state lasing intensity. The magnitude of the drop is strongly dependent on the wavelength of the depletion pulse and the applied injection current. Numerical simulations based on laser rate equations reproduce the experimental results and explain the wavelength dependence by the different dynamics in lasing and non-lasing sub-ensembles within the inhomogeneously broadened quantum dots. At high injection levels, the observedmore » response even upon perturbation of the lasing sub-ensemble is small and followed by a fast recovery, thus supporting the capacity of fast modulation in dual-state devices.« less

Generation of bound states of pulses in a SESAM mode-locked Cr:ZnSe laser

NASA Astrophysics Data System (ADS)

Bu, Xiangbao; Shi, Yuhang; Xu, Jia; Li, Huijuan; Wang, Pu

2018-06-01

We report on the generation of bound states of pulses in a SESAM mode-locked Cr:ZnSe laser around 2415 nm. A thulium-doped double-clad fiber laser at 1908 nm was used as the pump source. Bound states with various pulse separations at different dispersion regimes were obtained. Especially, in the anomalous dispersion regime, vibrating bound state of solitons exhibiting an evolving phase was obtained.

Probing defect states in polycrystalline GaN grown on Si(111) by sub-bandgap laser-excited scanning tunneling spectroscopy

NASA Astrophysics Data System (ADS)

Hsiao, F.-M.; Schnedler, M.; Portz, V.; Huang, Y.-C.; Huang, B.-C.; Shih, M.-C.; Chang, C.-W.; Tu, L.-W.; Eisele, H.; Dunin-Borkowski, R. E.; Ebert, Ph.; Chiu, Y.-P.

2017-01-01

We demonstrate the potential of sub-bandgap laser-excited cross-sectional scanning tunneling microscopy and spectroscopy to investigate the presence of defect states in semiconductors. The characterization method is illustrated on GaN layers grown on Si(111) substrates without intentional buffer layers. According to high-resolution transmission electron microscopy and cathodoluminescence spectroscopy, the GaN layers consist of nanoscale wurtzite and zincblende crystallites with varying crystal orientations and hence contain high defect state densities. In order to discriminate between band-to-band excitation and defect state excitations, we use sub-bandgap laser excitation. We probe a clear increase in the tunnel current at positive sample voltages during sub-bandgap laser illumination for the GaN layer with high defect density, but no effect is found for high quality GaN epitaxial layers. This demonstrates the excitation of free charge carriers at defect states. Thus, sub-bandgap laser-excited scanning tunneling spectroscopy is a powerful complimentary characterization tool for defect states.

Carrier Envelope Phase Effect of a Long Duration Pulse in the Low Frequency Region

NASA Astrophysics Data System (ADS)

Zhao, Xi; Yang, Yu-Jun; Liu, Xue-Shen; Wang, Bing-Bing

2014-04-01

Using the characteristic of small energy difference between two high Rydberg states, we theoretically investigate the carrier envelope phase (CEP) effect in a bound-bound transition of an atom in a low-frequency long laser pulse with tens of optical cycles. Particularly, we first prepare a Rydberg state of a hydrogen-like atom by a laser field with the resonant frequency between this state and the ground state. Then by using a low-frequency long laser pulse interacting with this Rydberg atom, we calculate the population of another Rydberg state nearby this Rydberg state at the end of the laser pulse and find that the population changes dramatically with the CEP of the low-frequency pulse. This CEP effect is attributed to the interference between the positive-frequency and negative-frequency components in one-photon transition. These results may provide a method to measure the CEP value of a long laser pulse with low frequency.

Single-resonance optical pumping spectroscopy and application in dressed-state measurement with atomic vapor cell at room temperature.

PubMed

Liang, Qiangbing; Yang, Baodong; Zhang, Tiancai; Wang, Junmin

2010-06-21

By monitoring the transmission of probe laser beam (also served as coupling laser beam) which is locked to a cycling hyperfine transition of cesium D(2) line, while pumping laser is scanned across cesium D(1) or D(2) lines, the single-resonance optical pumping (SROP) spectra are obtained with atomic vapor cell. The SROP spectra indicate the variation of the zero-velocity atoms population of one hyperfine fold of ground state, which is optically pumped into another hyperfine fold of ground state by pumping laser. With the virtue of Doppler-free linewidth, high signal-to-noise ratio (SNR), flat background and elimination of crossover resonance lines (CRLs), the SROP spectra with atomic vapor cell around room temperature can be employed to measure dressed-state splitting of ground state, which is normally detected with laser-cooled atomic sample only, even if the dressed-state splitting is much smaller than the Doppler-broaden linewidth at room temperature.

Measurement of neutron energy spectra for Eg=23.1 and 26.6 MeV mono-energetic photon induced reaction on natC using laser electron photon beam at NewSUBARU

NASA Astrophysics Data System (ADS)

Itoga, Toshiro; Nakashima, Hiroshi; Sanami, Toshiya; Namito, Yoshihito; Kirihara, Yoichi; Miyamoto, Shuji; Takemoto, Akinori; Yamaguchi, Masashi; Asano, Yoshihiro

2017-09-01

Photo-neutron energy spectra for Eg=23.1 and 26.6 MeV mono-energetic photons on natC were measured using laser Compton scattering facility at NewSUBARU BL01. The photon energy spectra were evaluated through measurements and simulations with collimator sizes and arrangements for the laser electron photon. The neutron energy spectra for the natC(g,xn) reaction were measured at 60 degrees in horizontal and 90 degrees in horizontal and vertical with respect to incident photon. The spectra show almost isotropic angular distribution and flat energy distribution from detection threshold to upper limit defined by reaction Q-value.

Tradeoffs between oscillator strength and lifetime in terahertz quantum cascade lasers

DOE PAGES

Chan, Chun Wang I.; Albo, Asaf; Hu, Qing; ...

2016-11-14

Contemporary research into diagonal active region terahertz quantum cascade lasers for high temperature operation has yielded little success. We present evidence that the failure of high diagonality alone as a design strategy is due to a fundamental trade-off between large optical oscillator strength and long upper-level lifetime. Here, we hypothesize that diagonality needs to be paired with increased doping in order to succeed, and present evidence that highly diagonal designs can benefit from much higher doping than normally found in terahertz quantum cascade lasers. In assuming the benefits of high diagonality paired with high doping, we also highlight important challengesmore » that need to be overcome, specifically the increased importance of carrier induced band-bending and impurity scattering.« less

Low Emittance, High Brilliance Relativistic Electron Beams from a Laser-Plasma Accelerator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brunetti, E.; Shanks, R. P.; Manahan, G. G.

2010-11-19

Progress in laser wakefield accelerators indicates their suitability as a driver of compact free-electron lasers (FELs). High brightness is defined by the normalized transverse emittance, which should be less than 1{pi} mm mrad for an x-ray FEL. We report high-resolution measurements of the emittance of 125 MeV, monoenergetic beams from a wakefield accelerator. An emittance as low as 1.1{+-}0.1{pi} mm mrad is measured using a pepper-pot mask. This sets an upper limit on the emittance, which is comparable with conventional linear accelerators. A peak transverse brightness of 5x10{sup 15} A m{sup -1} rad{sup -1} makes it suitable for compact XUVmore » FELs.« less

Solid state lasers for use in non-contact temperature measurements

NASA Technical Reports Server (NTRS)

Buoncristiani, A. M.

1989-01-01

The last decade has seen a series of dramatic developments in solid state laser technology. Prominent among these has been the emergence of high power semiconductor laser diode arrays and a deepening understanding of the dynamics of solid state lasers. Taken in tandem these two developments enable the design of laser diode pumped solid state lasers. Pumping solid state lasers with semiconductor diodes relieves the need for cumbersome and inefficient flashlamps and results in an efficient and stable laser with the compactness and reliability. It provides a laser source that can be reliably used in space. These new coherent sources are incorporated into the non-contact measurement of temperature. The primary focus is the development and characterization of new optical materials for use in active remote sensors of the atmosphere. In the course of this effort several new materials and new concepts were studied which can be used for other sensor applications. The general approach to the problem of new non-contact temperature measurements has had two components. The first component centers on passive sensors using optical fibers; an optical fiber temperature sensor for the drop tube was designed and tested at the Marshall Space Flight Center. Work on this problem has given insight into the use of optical fibers, especially new IR fibers, in thermal metrology. The second component of the effort is to utilize the experience gained in the study of passive sensors to examine new active sensor concepts. By active sensor are defined as a sensing device or mechanism which is interrogated in some way be radiation, usually from a laser. The status of solid state lasers as sources for active non-contact temperature sensors are summarized. Some specific electro-optic techniques are described which are applicable to the sensor problems at hand. Work on some of these ideas is in progress while other concepts are still being worked out.

High Power Laser Diode Arrays for 2-Micron Solid State Coherent Lidars Applications

NASA Technical Reports Server (NTRS)

Amzajerdian, Farzin; Meadows, Byron; Kavaya, Michael J.; Singh, Upendra; Sudesh, Vikas; Baker, Nathaniel

2003-01-01

Laser diode arrays are critical components of any diode-pumped solid state laser systems, constraining their performance and reliability. Laser diode arrays (LDAs) are used as the pump source for energizing the solid state lasing media to generate an intense coherent laser beam with a high spatial and spectral quality. The solid state laser design and the characteristics of its lasing materials define the operating wavelength, pulse duration, and power of the laser diodes. The pump requirements for high pulse energy 2-micron solid state lasers are substantially different from those of more widely used 1-micron lasers and in many aspects more challenging [1]. Furthermore, the reliability and lifetime demanded by many coherent lidar applications, such as global wind profiling from space and long-range clear air turbulence detection from aircraft, are beyond the capability of currently available LDAs. In addition to the need for more reliable LDAs with longer lifetime, further improvement in the operational parameters of high power quasi-cw LDAs, such as electrical efficiency, brightness, and duty cycle, are also necessary for developing cost-effective 2-micron coherent lidar systems for applications that impose stringent size, heat dissipation, and power constraints. Global wind sounding from space is one of such applications, which is the main driver for this work as part of NASA s Laser Risk Reduction Program. This paper discusses the current state of the 792 nm LDA technology and the technology areas being pursued toward improving their performance. The design and development of a unique characterization facility for addressing the specific issues associated with the LDAs for pumping 2-micron coherent lidar transmitters and identifying areas of technological improvement will be described. Finally, the results of measurements to date on various standard laser diode packages, as well as custom-designed packages with potentially longer lifetime, will be reported.

3D atom microscopy in the presence of Doppler shift

NASA Astrophysics Data System (ADS)

Rahmatullah; Chuang, You-Lin; Lee, Ray-Kuang; Qamar, Sajid

2018-03-01

The interaction of hot atoms with laser fields produces a Doppler shift, which can severely affect the precise spatial measurement of an atom. We suggest an experimentally realizable scheme to address this issue in the three-dimensional position measurement of a single atom in vapors of rubidium atoms. A three-level Λ-type atom-field configuration is considered where a moving atom interacts with three orthogonal standing-wave laser fields and spatial information of the atom in 3D space is obtained via an upper-level population using a weak probe laser field. The atom moves with velocity v along the probe laser field, and due to the Doppler broadening the precision of the spatial information deteriorates significantly. It is found that via a microwave field, precision in the position measurement of a single hot rubidium atom can be attained, overcoming the limitation posed by the Doppler shift.

Non-Topographic Space-Based Laser Remote Sensing

NASA Technical Reports Server (NTRS)

Yu, Anthony W.; Abshire, James B.; Riris, Haris; Purucker, Michael; Janches, Diego; Getty, Stephanie; Krainak, Michael A.; Stephen, Mark A.; Chen, Jeffrey R.; Li, Steve X.;

Sturge-Weber syndrome type II treated with PDL 595 nm laser.

PubMed

Kowalska-Brocka, Joanna; Brocki, Maciej; Uczniak, Sebastian; Uczniak, Kamila; Kaszuba, Andrzej; Jurowski, Piotr

2015-02-01

Sturge-Weber syndrome (SWS) is rare congenital disorder presenting facial port-wine stains (PWS) eye abnormalities and cerebrovascular malformations. The frequency of SWS is estimated at 1 in 50 000. Cerebrovascular abnormalities can be responsible for seizures, hemiparesis, mental retardation and ophthalmologic abnormalities cause intraocular pressure, glaucoma. Etiopathogenesis of SWS remains elusive. We present a case of a 7-year-old girl with SWS type II. A port-wine stain involves the upper right part of half face and has been associated with glaucoma of both eyes. In the Department of Dermatology in 2009-2012 we performed 23 procedures within 2 months. We have been using PDL laser at wavelength 595 nm and very good cosmetic results were achieved. Given positive treatment effects, the laser therapy of port-wine stains is a method of selection. Port-wine stains in the course of SWS requires a large number of laser treatment.

Sturge-Weber syndrome type II treated with PDL 595 nm laser

PubMed Central

Brocki, Maciej; Uczniak, Sebastian; Uczniak, Kamila; Kaszuba, Andrzej; Jurowski, Piotr

2015-01-01

Sturge-Weber syndrome (SWS) is rare congenital disorder presenting facial port-wine stains (PWS) eye abnormalities and cerebrovascular malformations. The frequency of SWS is estimated at 1 in 50 000. Cerebrovascular abnormalities can be responsible for seizures, hemiparesis, mental retardation and ophthalmologic abnormalities cause intraocular pressure, glaucoma. Etiopathogenesis of SWS remains elusive. We present a case of a 7-year-old girl with SWS type II. A port-wine stain involves the upper right part of half face and has been associated with glaucoma of both eyes. In the Department of Dermatology in 2009–2012 we performed 23 procedures within 2 months. We have been using PDL laser at wavelength 595 nm and very good cosmetic results were achieved. Given positive treatment effects, the laser therapy of port-wine stains is a method of selection. Port-wine stains in the course of SWS requires a large number of laser treatment. PMID:25821431

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blankenship, H.Lee; Thompson, Dan; United States. Bonneville Power Administration. Division of Fish and Wildlife

The first year of work with development of lasers as a mass marking technique provided both disappointing and encouraging results. A Coumarin Dye 480 laser was used to mark coho salmon in a variety of body locations and with varying energy levels. A ``bleached`` white mark was made void of any pigment. Areas marked included the nape area behind the head and in front of the dorsal fin, slightly above the anal fin, the upper lobe of the caudal fin, the dorsal fin and on the operculum. The mark appeared immediately after being lasered but started to gradually fade aftermore » one month and was fairly completely re-pigmented after three months. Complete removal and notching of the adipose fin was also attempted with a Carbon Dioxide laser. This surgical method of fin removal appears to have advantages over scissor excision (no bleeding or regeneration), and has possible application as part of a device or system which could be employed for mass marking.« less

Determining the Absorbance Spectra of Photochromic Materials From Measured Spectrophotometer Data

NASA Technical Reports Server (NTRS)

Downie, John D.

1998-01-01

If a two-state photochromic material is optically bleached, the absorbance spectrum data measured by a spectrophotometer is in general comprised of components from both the ground state and the upper state. Under general conditions, it may be difficult to extract the actual upper state spectrum from the spectrum of the bleached material. A simple algorithm is presented here for the recovery of the pure absorbance spectra of the upper state of a material such as bacteriorhodopsin, given single wavelength bleaching illumination, steady-state conditions, and accurate knowledge of phototransition rates and thermal decay rates.

Theoretical and experimental analysis of injection seeding a Q-switched alexandrite laser

NASA Technical Reports Server (NTRS)

Prasad, C. R.; Lee, H. S.; Glesne, T. R.; Monosmith, B.; Schwemmer, G. K.

1991-01-01

Injection seeding is a method for achieving linewidths of less than 500 MHz in the output of broadband, tunable, solid state lasers. Dye lasers, CW and pulsed diode lasers, and other solid state lasers have been used as injection seeders. By optimizing the fundamental laser parameters of pump energy, Q-switched pulse build-up time, injection seed power and mode matching, one can achieve significant improvements in the spectral purity of the Q-switched output. These parameters are incorporated into a simple model for analyzing spectral purity and pulse build-up processes in a Q-switched, injection-seeded laser. Experiments to optimize the relevant parameters of an alexandrite laser show good agreement.

Hyperfine rather than spin splittings dominate the fine structure of the B (4)Σ(-)-X (4)Σ(-) bands of AlC.

PubMed

Clouthier, Dennis J; Kalume, Aimable

2016-01-21

Laser-induced fluorescence and wavelength resolved emission spectra of the B (4)Σ(-)-X (4)Σ(-) band system of the gas phase cold aluminum carbide free radical have been obtained using the pulsed discharge jet technique. The radical was produced by electron bombardment of a precursor mixture of trimethylaluminum in high pressure argon. High resolution spectra show that each rotational line of the 0-0 and 1-1 bands of AlC is split into at least three components, with very similar splittings and intensities in both the P- and R-branches. The observed structure was reproduced by assuming bβS magnetic hyperfine coupling in the excited state, due to a substantial Fermi contact interaction of the unpaired electron in the aluminum 3s orbital. Rotational analysis has yielded ground and excited state equilibrium bond lengths in good agreement with the literature and our own ab initio values. Small discrepancies in the calculated intensities of the hyperfine lines suggest that the upper state spin-spin constant λ' is of the order of ≈ 0.025-0.030 cm(-1).

Fractional laser skin resurfacing.

PubMed

Alexiades-Armenakas, Macrene R; Dover, Jeffrey S; Arndt, Kenneth A

2012-11-01

Laser skin resurfacing (LSR) has evolved over the past 2 decades from traditional ablative to fractional nonablative and fractional ablative resurfacing. Traditional ablative LSR was highly effective in reducing rhytides, photoaging, and acne scarring but was associated with significant side effects and complications. In contrast, nonablative LSR was very safe but failed to deliver consistent clinical improvement. Fractional LSR has achieved the middle ground; it combined the efficacy of traditional LSR with the safety of nonablative modalities. The first fractional laser was a nonablative erbium-doped yttrium aluminum garnet (Er:YAG) laser that produced microscopic columns of thermal injury in the epidermis and upper dermis. Heralding an entirely new concept of laser energy delivery, it delivered the laser beam in microarrays. It resulted in microscopic columns of treated tissue and intervening areas of untreated skin, which yielded rapid reepithelialization. Fractional delivery was quickly applied to ablative wavelengths such as carbon dioxide, Er:YAG, and yttrium scandium gallium garnet (2,790 nm), providing more significant clinical outcomes. Adjustable laser parameters, including power, pitch, dwell time, and spot density, allowed for precise determination of percent surface area, affected penetration depth, and clinical recovery time and efficacy. Fractional LSR has been a significant advance to the laser field, striking the balance between safety and efficacy.

QCL seeded, ns-pulse, multi-line, CO2 laser oscillator for laser-produced-plasma extreme-UV source

NASA Astrophysics Data System (ADS)

Nowak, Krzysztof Michał; Suganuma, Takashi; Kurosawa, Yoshiaki; Ohta, Takeshi; Kawasuji, Yasufumi; Nakarai, Hiroaki; Saitou, Takashi; Fujimoto, Junichi; Mizoguchi, Hakaru; Sumitani, Akira; Endo, Akira

2017-01-01

Successful merger of state-of-the-art, semiconductor quantum-cascade lasers (QCL), with the mature CO2 laser technology, resulted in a delivery of highly-desired qualities of CO2 laser output that were not available previously without much effort. These qualities, such as multi-line operation, excellent spectro-temporal stability and pulse waveform control, became available from a single device of moderate complexity. This paper describes the operation principle and the unique properties of the solid{state seeded CO2 laser, invented for an application in laser-produced-plasma (LPP), extreme-UV (EUV) light source.

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.

Design of laser-driven SiO2-YAG:Ce composite thick film: Facile synthesis, robust thermal performance, and application in solid-state laser lighting

NASA Astrophysics Data System (ADS)

Xu, Jian; Liu, Bingguo; Liu, Zhiwen; Gong, Yuxuan; Hu, Baofu; Wang, Jian; Li, Hui; Wang, Xinliang; Du, Baoli

2018-01-01

In recent times, there have been rapid advances in the solid-state laser lighting technology. Due to the large amounts of heat accumulated from the high flux laser radiation, color conversion materials used in solid-state laser lighting devices should possess high durability, high thermal conductivity, and low thermal quenching. The aim of this study is to develop a thermally robust SiO2-YAG:Ce composite thick film (CTF) for high-power solid-state laser lighting applications. Commercial colloidal silica which was used as the source of SiO2, played the roles of an adhesive, a filler, and a protecting agent. Compared to the YAG:Ce powder, the CTF exhibits remarkable thermal stability (11.3% intensity drop at 200 °C) and durability (4.5% intensity drop after 1000 h, at 85 °C and 85% humidity). Furthermore, the effects of the substrate material and the thickness of the CTF on the laser lighting performance were investigated in terms of their thermal quenching and luminescence saturation behaviors, respectively. The CTF with a thickness of 50 μm on a sapphire substrate does not show luminescence saturation, despite a high-power density of incident radiation i.e. 20 W/mm2. These results demonstrate the potential applicability of the CTF in solid-state laser lighting devices.

Rogue waves generation via nonlinear soliton collision in multiple-soliton state of a mode-locked fiber laser.

PubMed

Peng, Junsong; Tarasov, Nikita; Sugavanam, Srikanth; Churkin, Dmitry

2016-09-19

We report for the first time, rogue waves generation in a mode-locked fiber laser that worked in multiple-soliton state in which hundreds of solitons occupied the whole laser cavity. Using real-time spatio-temporal intensity dynamics measurements, it is unveiled that nonlinear soliton collision accounts for the formation of rogue waves in this laser state. The nature of interactions between solitons are also discussed. Our observation may suggest similar formation mechanisms of rogue waves in other systems.

Ultrafast Physics Behind the Nonradiative Relaxation Process of Chromium Ions in Forsterite Crystals.

NASA Astrophysics Data System (ADS)

Demos, Stavros Gregorios

The nonradiative relaxation following photoexcitation has been studied in Cr^{4+} -doped forsterite (Mg_2SiO _4) using picosecond laser excitation and ultrasensitive photon counting detection. The experimental techniques utilized were time resolved antiStokes Raman scattering and up-converted hot and ordinary luminescence. The up-converted hot luminescence technique allowed the investigation of the upper state nonradiative relaxation of the excited state manifold of Cr^{4+ }-doped forsterite. The excitation involves the absorption of two photons per photoexcited ion in a two-step absorption. Discrete peaks are observed in the hot up-converted luminescence spectrum and are attributed to the population of nonequilibrium vibronic levels during the deexcitation of the ions by phonon emission. This work reveals that the phonon modes participating in the initial steps of the nonradiative relaxation of the photoexcited ions have energies 218 +/- 20, 325 +/- 20, 365 +/- 20 and 513 +/- 12 cm^ {-1}. The shape of the luminescence spectral envelope suggests two electronic bottlenecks at ~2.1 and ~2.45 eV associated with slower rates of vibrational relaxation at different parts of the excited state manifold. Time resolved measurements indicated that the average time for phonon emission is of the order of hundreds of fs. Information on the nonequilibrium phonon dynamics of the 225, 335 and 370 cm^{-1} modes of forsterite has been obtained using time resolved Raman scattering. Laser pulses of 450 fs in duration and 590 nm in wavelength were used to excite the Cr ions 2.1 eV above the ground state. The probe pulses (obtained from the same laser) are monitoring the nonequilibrium phonon population through the intensity of the antiStokes Raman lines at various pump-probe delay times. Experiments were performed at room and liquid nitrogen temperatures. The observed nonequilibrium phonon populations are associated with the overall complex nonradiative decay following the excitation of the impurity Cr^{4+} ions. Using rate equations to describe the electron -lattice system, the nonradiative relaxation time and the phonon lifetimes were estimated by fitting to the experimental data. The nonradiative relaxation time is estimated to be in the order of few ps while the phonon lifetimes are of the order of 10 ps. Best fit suggests the presence of an electronic bottleneck immediately after photoexcitation with an estimated lifetime of 3 ps at room temperature.

Theoretical derivation of laser-dressed atomic states by using a fractal space

NASA Astrophysics Data System (ADS)

Duchateau, Guillaume

2018-05-01

The derivation of approximate wave functions for an electron submitted to both a Coulomb and a time-dependent laser electric fields, the so-called Coulomb-Volkov (CV) state, is addressed. Despite its derivation for continuum states does not exhibit any particular problem within the framework of the standard theory of quantum mechanics (QM), difficulties arise when considering an initially bound atomic state. Indeed the natural way of translating the unperturbed momentum by the laser vector potential is no longer possible since a bound state does not exhibit a plane wave form explicitly including a momentum. The use of a fractal space permits to naturally define a momentum for a bound wave function. Within this framework, it is shown how the derivation of laser-dressed bound states can be performed. Based on a generalized eikonal approach, a new expression for the laser-dressed states is also derived, fully symmetric relative to the continuum or bound nature of the initial unperturbed wave function. It includes an additional crossed term in the Volkov phase which was not obtained within the standard theory of quantum mechanics. The derivations within this fractal framework have highlighted other possible ways to derive approximate laser-dressed states in QM. After comparing the various obtained wave functions, an application to the prediction of the ionization probability of hydrogen targets by attosecond XUV pulses within the sudden approximation is provided. This approach allows to make predictions in various regimes depending on the laser intensity, going from the non-resonant multiphoton absorption to tunneling and barrier-suppression ionization.

Quadrupole splittings in the near-infrared spectrum of 14NH 3

DOE PAGES

Twagirayezu, Sylvestre; Hall, Gregory E.; Sears, Trevor J.

2016-10-13

Sub-Doppler, saturation dip, spectra of lines in the v 1 + v 3, v 1 + 2v 4 and v 3 + 2v 4 bands of 14NH 3 have been measured by frequency comb-referenced diode laser absorption spectroscopy. The observed spectral line widths are dominated by transit time broadening, and show resolved or partially-resolved hyperfine splittings that are primarily determined by the 14N quadrupole coupling. Modeling of the observed line shapes based on the known hyperfine level structure of the ground state of the molecule shows that, in nearly all cases, the excited state level has hyperfine splittings similar tomore » the same rotational level in the ground state. The data provide accurate frequencies for the line positions and easily separate lines overlapped in Doppler-limited spectra. The observed hyperfine splittings can be used to make and confirm rotational assignments and ground state combination differences obtained from the measured frequencies are comparable in accuracy to those obtained from conventional microwave spectroscopy. Furthermore, several of the measured transitions do not show the quadrupole hyperfine splittings expected based on their existing rotational assignments. Either the assignments are incorrect or the upper levels involved are perturbed in a way that affects the nuclear hyperfine structure.« less

Laser demonstration and performance characterization of optically pumped Alkali Laser systems

NASA Astrophysics Data System (ADS)

Sulham, Clifford V.

Diode Pumped Alkali Lasers (DPALs) offer a promising approach for high power lasers in military applications that will not suffer from the long logistical trails of chemical lasers or the thermal management issues of diode pumped solid state lasers. This research focuses on characterizing a DPAL-type system to gain a better understanding of using this type of laser as a directed energy weapon. A rubidium laser operating at 795 nm is optically pumped by a pulsed titanium sapphire laser to investigate the dynamics of DPALs at pump intensities between 1.3 and 45 kW/cm2. Linear scaling as high as 32 times threshold is observed, with no evidence of second order kinetics. Comparison of laser characteristics with a quasi-two level analytic model suggests performance near the ideal steady-state limit, disregarding the mode mis-match. Additionally, the peak power scales linearly as high as 1 kW, suggesting aperture scaling to a few cm2 is sufficient to achieve tactical level laser powers. The temporal dynamics of the 100 ns pump and rubidium laser pulses are presented, and the continually evolving laser efficiency provides insight into the bottlenecking of the rubidium atoms in the 2P3/2 state. Lastly, multiple excited states of rubidium and cesium were accessed through two photon absorption in the red, yielding a blue and an IR photon through amplified stimulated emission. Threshold is modest at 0.3 mJ/pulse, and slope efficiencies increase dramatically with alkali concentrations and peak at 0.4%, with considerable opportunity for improvement. This versatile system might find applications for IR countermeasures or underwater communications.

Minimally invasive management with holmium laser in total urinary tract calculi.

PubMed

Zhang, Xiao; Yu, Jianjun; Yang, Ranxing

2013-05-01

The purpose of this article was to study the management of total urinary tract calculi using holmium laser minimally invasive techniques. It is rare for patients to present kidney stones, ureteral stones, and bladder stones simultaneously, and their treatment is considered to be complicated and difficult, specifically by minimally invasive techniques. We collected seven cases of total urinary tract calculi from May 2007 to September 2012. Three cases were unilateral, and the others were bilateral. All of the cases presented calculus in the bladder, ureter, and kidney, which were secondary to the long-term indwelling double J stent or lower urinary obstruction. Extracorporeal shock-wave lithotripsy (SWL) was administered first, followed by the operation. For patients with bilateral calculi, at one stage, ureteroscopic lithotripsy (URL) with holmium laser was performed in all four cases to remove the bladder and bilateral ureter stones. Then, all patients underwent percutaneous nephrolithotomy (PCNL) with holmium procedures to address the bilateral kidney and upper ureter stones at the second stage. The indwelling double J stents were removed at the same time. For the patients with unilateral calculi, we performed a single operation, but it was conducted using the same treatment sequence as the bilateral procedure. The related symptoms in all cases disappeared after the operation. Re-examination showed that the stones were nearly dissolved and that renal function was recovered. URL with holmium laser for the bladder and ureters combined with PCNL to dissolve kidney and upper ureteral stones could be the ideal choice for the treatment of total urinary tract calculi.

Recent advances and challenges for diode-pumped solid-state lasers as an inertial fusion energy driver candidate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Payne, S.A.; Beach, R.J.; Bibeau, C.

We discuss how solid-state laser technology can serve in the interests of fusion energy beyond the goals of the National Ignition Facility (NIF), which is now being constructed to ignite a deuterium-tritium target to fusion conditions in the laboratory for the first time. We think that advanced solid-state laser technology can offer the repetition-rate and efficiency needed to drive a fusion power plant, in contrast to the single-shot character of NIF. As discuss below, we propose that a gas-cooled, diode-pumped Yb:S-FAP laser can provide a new paradigm for fusion laser technology leading into the next century.

Influence of Photobiomodulation Therapy on Gingivitis Induced by Multi-Bracket Appliances: A Split-Mouth Randomized Controlled Trial.

PubMed

Stein, Steffen; Schauseil, Michael; Hellak, Andreas; Korbmacher-Steiner, Heike; Braun, Andreas

2018-05-18

The objective of this split-mouth trial was to investigate the influence of photobiomodulation therapy (PBMT) on adjuvant treatment of gingivitis induced by multi-bracket appliances, after bracket debonding and professional tooth cleaning. Thirteen patients (mean age 16.15 years; standard deviation ±2.12 years) who had completed active orthodontic treatment with fixed orthodontic appliances in an orthodontic clinic were included on a randomized basis. At time point T0, after bracket debonding and professional tooth cleaning, the papilla bleeding index (PBI) and bleeding on probing (BOP) were assessed in the upper jaw by the blinded investigator (M.S.), who was not aware at any time of which quadrant received PBMT. The study was based on a patient-blinded split-mouth design. In each patient, PBMT was administered by a practitioner (S.S.) in one upper quadrant (wavelength: 660 nm; Power: 100 mW; Power density: 100 mW/cm 2 ; Energy density per application point = 2 J/cm 2 ; Energy per application point = 2 J; Total dose = 52 J/cm 2 ; Total energy = 52 J; Irradiation time: 26 × 20 sec), while the other upper quadrant received a simulated laser application with the laser system turned off. Randomized equal allocation of the sides was accomplished. The second PBI and BOP assessment followed 4-6 days after laser irradiation (T1) by M.S. No statistical differences were observed between the sides with regard to PBI and BOP values at T0 (p > 0.05). The PBI and BOP values decreased significantly between T0 and T1 on both sides (p < 0.05). At T1, the PBI and BOP values were significantly lower in the laser side in comparison with the control side (p < 0.05). On the basis of these results and study parameters, adjuvant PBMT is able to accelerate the healing process in patients with gingivitis induced by multi-bracket appliances.

Silica-coated gold nanorods as saturable absorber for bound-state pulse generation in a fiber laser with near-zero dispersion

NASA Astrophysics Data System (ADS)

Wang, Xude; Luo, Aiping; Luo, Zhichao; Liu, Meng; Zou, Feng; Zhu, Yanfang; Xue, Jianping; Xu, Wencheng

2017-11-01

We presented a bound-state operation in a fiber laser with near-zero anomalous dispersion based on a silica-coated gold nanorods (GNRs@SiO2) saturable absorber (SA). Using a balanced twin detector measurement technique, the modulation depth and nonsaturable loss of the GNRs@SiO2 SA were measured to be approximately 3.5% and 39.3%, respectively. By virtue of the highly nonlinear effect of the GNRs@SiO2 SA, the bound-state pulses could be easily observed. Besides the lower-order bound-state pulses with two, three, and four solitons, the higher-order bound states with up to 12 solitons were also obtained in the laser cavity. The pulse profiles of the higher-order bound states were further reconstructed theoretically. The experimental results would give further insight towards understanding the complex nonlinear dynamics of bound-state pulses in fiber lasers.

Pulsed solid state lasers for medicine

NASA Astrophysics Data System (ADS)

Kertesz, Ivan; Danileiko, A. Y.; Denker, Boris I.; Kroo, Norbert; Osiko, Vyacheslav V.; Prokhorov, Alexander M.

1994-02-01

The effect on living tissues of different pulsed solid state lasers: Nd:YAG ((lambda) equals 1.06 micrometers ) Er:glass (1.54 micrometers ), Ho:YAG (2.1 micrometers ) and Er:YAG (2.94 micrometers ) is compared with the continuous wave Nd:YAG- and CO2-lasers used in operating theaters. Portable Er:glass- and Er:YAG-lasers are developed for surgery/cosmetics and HIV-safe blood testing.

Solid state laser media driven by remote nuclear powered fluorescence

DOEpatents

Prelas, Mark A.

1992-01-01

An apparatus is provided for driving a solid state laser by a nuclear powered fluorescence source which is located remote from the fluorescence source. A nuclear reaction produced in a reaction chamber generates fluorescence or photons. The photons are collected from the chamber into a waveguide, such as a fiber optic waveguide. The waveguide transports the photons to the remote laser for exciting the laser.

Component-Level Selection and Qualification for the Global Ecosystem Dynamics Investigation (GEDI) Laser Altimeter Transmitter

NASA Technical Reports Server (NTRS)

Frese, Erich A.; Chiragh, Furqan L.; Switzer, Robert; Vasilyev, Aleksey A.; Thomes, Joe; Coyle, D. Barry; Stysley, Paul R.

2018-01-01

Flight quality solid-state lasers require a unique and extensive set of testing and qualification processes, both at the system and component levels to insure the laser's promised performance. As important as the overall laser transmitter design is, the quality and performance of individual subassemblies, optics, and electro-optics dictate the final laser unit's quality. The Global Ecosystem Dynamics Investigation (GEDI) laser transmitters employ all the usual components typical for a diode-pumped, solid-state laser, yet must each go through their own individual process of specification, modeling, performance demonstration, inspection, and destructive testing. These qualification processes and results for the laser crystals, laser diode arrays, electro-optics, and optics, will be reviewed as well as the relevant critical issues encountered, prior to their installation in the GEDI flight laser units.

Correlation of histological findings of single session Er:YAG skin fractional resurfacing with various passes and energies and the possible clinical implications.

PubMed

Trelles, Mario A; Vélez, Mariano; Mordon, Serge

2008-03-01

Ablative fractional resurfacing shows promise for skin resurfacing and tightening and also to improve treatment of epidermal and dermal pigmentary disorders. This study aimed at determining any correlation between epidermal ablation and effects on the dermis when using an Er:YAG laser in ablative fractional resurfacing mode. Ten female subjects participated in the study, mean age 52 years, Skin phototypes: 1 Fitzpatrick type II; 8 type III and 1 type IV. The degree of wrinkles (Glogau scale II or III) was similar in all cases. The laser used was the Pixel Er:YAG system (Alma Lasertrade mark, Israel) which delivers the laser beam via a hand-piece equipped with a beam splitter to divide the 2,940 nm beam into various microbeams of 850 microm in diameter in an 11 mmx11 mm treatment area. Using a constant energy of 1,400 mJ/cm(2), on a test area of 4 cmx2 cm. Two, 4, 6, and 8 passes on the preauricular area of the face were evaluated immediately after treatment. In all cases, the handpiece was kept in the same position, and rotated slightly around its perpendicular axis between passes, then moved on to the next spot. Biopsies were performed and tissue samples were routinely processed and stained with hematoxylin and eosin (H&E). No patient reported any noticeable discomfort, even at 8 passes. The histological findings revealed that, independent of the degree of the wrinkles, more laser passes produced more ablative removal of the epidermis. Residual thermal damage (RTD) with 2 laser passes was not observed but with 4 and 6 passes increased thermal effects and vacuole formation in the epidermal cells were noticed. With 8 laser passes, total epidermal removal was seen together with frank RTD-related changes in the upper part of the papillary dermis. In this study, we have demonstrated that high density fractional Er:YAG laser energy in a single session with multiple passes targeted not only the skin surface with elimination of the epidermis, but could also achieve heat deposition in the upper dermis. When performing ablative fractional resurfacing with an Er:YAG laser, treatment of varying degrees of damage could be achieved by varying the number of passes. (c) 2008 Wiley-Liss, Inc.

Direct diode lasers with comparable beam quality to fiber, CO2, and solid state lasers

NASA Astrophysics Data System (ADS)

Huang, Robin K.; Chann, Bien; Burgess, James; Kaiman, Michael; Overman, Robert; Glenn, John D.; Tayebati, Parviz

2012-03-01

TeraDiode has produced kW-class ultra-high brightness fiber-coupled direct diode lasers. A fiber-coupled direct diode laser with a power level of 2,040 W from a 50 μm core diameter, 0.15 numerical aperture (NA) output fiber at a single center wavelength was demonstrated. This was achieved with a novel beam combining and shaping technique using COTS diode lasers. The fiber-coupled output corresponds to a Beam Parameter Product (BPP) of 3.75 mm-mrad and is the lowest BPP kW-class direct diode laser yet reported. This laser is suitable for industrial materials processing applications, including sheet metal cutting and welding. This 2-kW fiber-coupled direct diode laser has comparable brightness to that of industrial fiber lasers and CO2 lasers, and is over 10x brighter than state-of-the-art direct diode lasers.

An All-Solid-State High Repetiton Rate Titanium:Sapphire Laser System For Resonance Ionization Laser Ion Sources

NASA Astrophysics Data System (ADS)

Mattolat, C.; Rothe, S.; Schwellnus, F.; Gottwald, T.; Raeder, S.; Wendt, K.

2009-03-01

On-line production facilities for radioactive isotopes nowadays heavily rely on resonance ionization laser ion sources due to their demonstrated unsurpassed efficiency and elemental selectivity. Powerful high repetition rate tunable pulsed dye or Ti:sapphire lasers can be used for this purpose. To counteract limitations of short pulse pump lasers, as needed for dye laser pumping, i.e. copper vapor lasers, which include high maintenance and nevertheless often only imperfect reliability, an all-solid-state Nd:YAG pumped Ti:sapphire laser system has been constructed. This could complement or even replace dye laser systems, eliminating their disadvantages but on the other hand introduce shortcomings on the side of the available wavelength range. Pros and cons of these developments will be discussed.

Laser interaction with tissue

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berns, M.W.

These proceedings collect papers on laser biomedicine. Topics include: light distributions on tissue; chemical byproducts of laser/tissue interactions; laser applications in ophthalmology; phododynamic therapy; diode pumped solid state lasers at two and three micrometers; and applications of excimer lasers to peripheral nerve repair.

Simultaneous multi-state stimulated emission in quantum dot lasers: experiment and analytical approach

NASA Astrophysics Data System (ADS)

Korenev, V. V.; Savelyev, A. V.; Zhukov, A. E.; Omelchenko, A. V.; Maximov, M. V.; Shernyakov, Yu. M.

2012-06-01

The theoretical investigation of the double-state lasing phenomena in InAs/InGaAs quantum dot lasers has been carried out. The new mechanism of the ground-state lasing quenching, which takes place in quantum dot (QD) laser operating in double-state lasing regime at high pump level, was proposed. The difference between electron and hole capture rates causes the depletion of the hole levels and consequently leads to the decrease of an output lasing power via QD ground state with the growth of injection. Moreover, it was shown that the hole-to-electron capture rates ratio strongly affects both the light-current curve and the key laser parameters. The model of the simultaneous lasing through the ground and excited QD states was developed which allows to describe the observed quenching quantitatively.

Quantum dynamics of charge state in silicon field evaporation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Silaeva, Elena P.; Uchida, Kazuki; Watanabe, Kazuyuki, E-mail: kazuyuki@rs.kagu.tus.ac.jp

2016-08-15

The charge state of an ion field-evaporating from a silicon-atom cluster is analyzed using time-dependent density functional theory coupled to molecular dynamics. The final charge state of the ion is shown to increase gradually with increasing external electrostatic field in agreement with the average charge state of silicon ions detected experimentally. When field evaporation is triggered by laser-induced electronic excitations the charge state also increases with increasing intensity of the laser pulse. At the evaporation threshold, the charge state of the evaporating ion does not depend on the electrostatic field due to the strong contribution of laser excitations to themore » ionization process both at low and high laser energies. A neutral silicon atom escaping the cluster due to its high initial kinetic energy is shown to be eventually ionized by external electrostatic field.« less

Numerical study on the selective excitation of Helmholtz-Gauss beams in end-pumped solid-state digital lasers with the control of the laser gain transverse position provided by off-axis end pumping

NASA Astrophysics Data System (ADS)

Tsai, Ko-Fan; Chu, Shu-Chun

2018-03-01

This study proposes a complete and unified method for selective excitation of any specified nearly nondiffracting Helmholtz-Gauss (HzG) beam in end-pumped solid-state digital lasers. Four types of the HzG beams: cosine-Gauss beams, Bessel-Gauss beams, Mathieu-Gauss beams, and, in particular, parabolic-Gauss beams are successfully demonstrated to be generated with the proposed methods. To the best of the authors’ knowledge, parabolic-Gauss beams have not yet been directly generated from any kind of laser system. The numerical results of this study show that one can successfully achieve any lasing HzG beams directly from the solid-state digital lasers with only added control of the laser gain transverse position provided by off-axis end pumping. This study also presents a practical digital laser set-up for easily manipulating off-axis pumping in order to achieve the control of the laser gain transverse gain position in digital lasers. The reported results in this study provide advancement of digital lasers in dynamically generating nondiffracting beams. The control of the digital laser cavity gain position creates the possibility of achieving real-time selection of more laser modes in digital lasers, and it is worth further investigation in the future.

Tunable solid-state lasers - An emerging technology for remote sensing of planetary atmospheres

NASA Technical Reports Server (NTRS)

Barnes, Norman P.; Allario, Frank

1988-01-01

The present development status and prospective (1990s) performance-improvement evaluation of tunable solid-state laser technology notes recent trends toward spectrum coverage over the 0.20-14.0 microns range, in addition to dramatic increases in efficiency, service life, and reliability. It is judged that the Ti:Al2O3 laser and the AgGaSe2 optical parametric oscillator pumped by a Ho:YAG laser could cover the near-IR and mid-IR regions of the spectrum. Laser diodes operating at 0.78 microns should provide an excellent pump for a Ho:YAG laser.

Solid-state lasers for coherent communication and remote sensing

NASA Technical Reports Server (NTRS)

Byer, Robert L.

1991-01-01

Work in the stabilization of monolithic Nd:YAG lasers and the application of these lasers to nonlinear optical frequency conversion is discussed. The intrinsic stability of semiconductor diode laser pumped solid state lasers has facilitated a number of demonstration in external resonant cavity harmonic generation and stable optical parametric oscillation. Relative laser frequency stabilization of 0.3 Hz was achieved, and absolute stability of a few hundred hertz is anticipated. The challenge is now to reproduce this frequency stability in the output of tunable nonlinear optical devices. Theoretical and experimental work toward this goal are continuing.

EFFECTS OF LASER RADIATION ON MATTER: Spectrum of the barium atom in a laser radiation field

NASA Astrophysics Data System (ADS)

Bondar', I. I.; Suran, V. V.

1990-08-01

An experimental investigation was made of the influence of a laser radiation field on the spectrum of barium atoms. The investigation was carried out by the method of three-photon ionization spectroscopy using dye laser radiation (ω = 14 800-18 700 cm - 1). The electric field intensity of the laser radiation was 103-106 V/cm. This laser radiation field had a strong influence on a number of bound and autoionizing states. The nature of this influence depended on the ratio of the excitation frequencies of bound and autoionizing states.

Detailed Balance Limit of Efficiency of Broadband-Pumped Lasers.

PubMed

Nechayev, Sergey; Rotschild, Carmel

2017-09-13

Broadband light sources are a wide class of pumping schemes for lasers including LEDs, sunlight and flash lamps. Recently, efficient coupling of broadband light to high-quality micro-cavities has been demonstrated for on-chip applications and low-threshold solar-pumped lasers via cascade energy transfer. However, the conversion of incoherent to coherent light comes with an inherent price of reduced efficiency, which has yet to be assessed. In this paper, we derive the detailed balance limit of efficiency of broadband-pumped lasers and discuss how it is affected by the need to maintain a threshold population inversion and thermodynamically dictated minimal Stokes' shift. We show that lasers' slope efficiency is analogous to the nominal efficiency of solar cells, limited by thermalisation losses and additional unavoidable Stokes' shift. The lasers' power efficiency is analogous to the detailed balance limit of efficiency of solar cells, affected by the cavity mirrors and impedance matching factor, respectively. As an example we analyze the specific case of solar-pumped sensitized Nd 3+ :YAG-like lasers and define the conditions to reach their thermodynamic limit of efficiency. Our work establishes an upper theoretical limit for the efficiency of broadband-pumped lasers. Our general, yet flexible model also provides a way to incorporate other optical and thermodynamic losses and, hence, to estimate the efficiency of non-ideal broadband-pumped lasers.

High-Resolution Microwave and Infrared Molecular-Beam Studies of the Conformers of 1,1,2,2-Tetrafluoroethane

NASA Astrophysics Data System (ADS)

Stone, Stephen C.; Philips, Laura A.; Fraser, G. T.; Lovas, F. J.; Xu, Li-Hong; Sharpe, S. W.

1998-11-01

High-resolution microwave and infrared molecular-beam spectra have been measured for 1,1,2,2-tetrafluoroethane (HFC134). For the higher energy, polar,C2symmetry,gaucheconformer, microwave spectra have been recorded for the normal and mono-13C isotopomers and analyzed to determine a C-C bond length of 1.512(4) Å, in good agreement with a recentab initiovalue (MP2/6-31G**) of 1.515 Å [S. Papasavva, K. H. Illinger, and J. E. Kenny,J. Phys. Chem.100, 10100-10110 (1996)]. A tunable microwave-sideband CO2laser and electric-resonance optothermal spectrometer have been used to measure the infrared spectrum of the ν6, C-C stretch of thegaucheconformer near 906 cm-1. Microwave-infrared double resonance and precise ground state combination differences provided by the microwave measurements guide the assignment of the spectrum. The observation of ac-type spectrum definitively establishes that the upper state vibration is ofAsymmetry in theC2point group. The spectrum is fit to a Watson asymmetric-top Hamiltonian to a standard deviation of 0.24 MHz. A weak perturbation shifts the line positions for transitions nearJ = Kc= 20 by as much as 12 MHz. The identity of the perturber is unknown. Pulsed slit-jet diode-laser spectra have been recorded for the ν16vibration of theanticonformer near 1127 cm-1. Ana- andc-type hybrid band is observed, consistent with aBusymmetry mode. Previous low-resolution studies have attributed the 1127-cm-1mode to either aBuor anAusymmetry vibration. A total of 522 nonblended transitions were assigned and fit to determine ground and excited state constants. The ground state constants ofA= 5134.952(65) MHz,B= 3148.277(27) MHz, andC= 2067.106(43) MHz are the first experimental determinations of the rotational constants for this conformer. Here, typeAstandard uncertainties are given in the parentheses.

Lasers '92; Proceedings of the International Conference on Lasers and Applications, 15th, Houston, TX, Dec. 7-10, 1992

NASA Technical Reports Server (NTRS)

Wang, Charles P. (Editor)

1993-01-01

Papers from the conference are presented, and the topics covered include the following: x-ray lasers, excimer lasers, chemical lasers, high power lasers, blue-green lasers, dye lasers, solid state lasers, semiconductor lasers, gas and discharge lasers, carbon dioxide lasers, ultrafast phenomena, nonlinear optics, quantum optics, dynamic gratings and wave mixing, laser radar, lasers in medicine, optical filters and laser communication, optical techniques and instruments, laser material interaction, and industrial and manufacturing applications.

Self-Mixing Thin-Slice Solid-State Laser Metrology

PubMed Central

Otsuka, Kenju

2011-01-01

This paper reviews the dynamic effect of thin-slice solid-state lasers subjected to frequency-shifted optical feedback, which led to the discovery of the self-mixing modulation effect, and its applications to quantum-noise-limited versatile laser metrology systems with extreme optical sensitivity. PMID:22319406

Use of a novel tunable solid state disk laser as a diagnostic system for laser-induced fluorescence

NASA Astrophysics Data System (ADS)

Paa, Wolfgang; Triebel, Wolfgang

2004-09-01

An all solid state disk laser system-named "Advanced Disk Laser (ADL)" -particularly tailored for laser induced fluorescence (LIF) in combustion processes is presented. The system currently under development comprises an Yb:YAG-seedlaser and a regenerative amplifier. Both are based on the disk laser concept as a new laser architecture. This allows a tunable, compact, efficient diode pumped solid state laser (DPSSL) system with repetition rates in the kHz region. After frequency conversion to the UV-spectral region via third and fourth harmonics generation, this laser-due to its unique properties such as single-frequency operation, wavelength tuneability and excellent beam profile-is well suited for excitation of small molecules such as formaldehyde, OH, NO or O2, which are characteristic for combustion processes. Using the method of planar laser induced fluorescence (PLIF) we observed concentration distributions of formaldehyde in cool and hot flames of a specially designed diethyl-ether burner. The images recorded with 1 kHz repetition rate allow visualizing the distribution of formaldehyde on a 1 ms time scale. This demonstrates for the first time the usability of this novel laser for LIF measurements and is the first step towards integration of the ADL into capsules for drop towers and the international space station.

Applicability of post-ionization theory to laser-assisted field evaporation of magnetite

DOE PAGES

Schreiber, Daniel K.; Chiaramonti, Ann N.; Gordon, Lyle M.; ...

2014-12-15

Analysis of the mean Fe ion charge state from laser-assisted field evaporation of magnetite (Fe3O4) reveals unexpected trends as a function of laser pulse energy that break from conventional post-ionization theory for metals. For Fe ions evaporated from magnetite, the effects of post-ionization are partially offset by the increased prevalence of direct evaporation into higher charge states with increasing laser pulse energy. Therefore the final charge state is related to both the field strength and the laser pulse energy, despite those variables themselves being intertwined when analyzing at a constant detection rate. Comparison of data collected at different base temperaturesmore » also show that the increased prevalence of Fe2+ at higher laser energies is possibly not a direct thermal effect. Conversely, the ratio of 16O+:16O2+ is well-correlated with field strength and unaffected by laser pulse energy on its own, making it a better overall indicator of the field evaporation conditions than the mean Fe charge state. Plotting the normalized field strength versus laser pulse energy also elucidates a non-linear dependence, in agreement with previous observations on semiconductors, that suggests a field-dependent laser absorption efficiency. Together these observations demonstrate that the field evaporation process for laser-pulsed oxides exhibits fundamental differences from metallic specimens that cannot be completely explained by post-ionization theory. Further theoretical studies, combined with detailed analytical observations, are required to understand fully the field evaporation process of non-metallic samples.« less

Raman-laser spectroscopy of Wannier-Stark states

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tackmann, G.; Pelle, B.; Hilico, A.

2011-12-15

Raman lasers are used as a spectroscopic probe of the state of atoms confined in a shallow one-dimensional (1D) vertical lattice. For sufficiently long laser pulses, resolved transitions in the bottom band of the lattice between Wannier Stark states corresponding to neighboring wells are observed. Couplings between such states are measured as a function of the lattice laser intensity and compared to theoretical predictions, from which the lattice depth can be extracted. Limits to the linewidth of these transitions are investigated. Transitions to higher bands can also be induced, as well as between transverse states for tilted Raman beams. Allmore » these features allow for a precise characterization of the trapping potential and for an efficient control of the atomic external degrees of freedom.« less

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.

An integrated autonomous rendezvous and docking system architecture using Centaur modern avionics

NASA Technical Reports Server (NTRS)

Nelson, Kurt

1991-01-01

The avionics system for the Centaur upper stage is in the process of being modernized with the current state-of-the-art in strapdown inertial guidance equipment. This equipment includes an integrated flight control processor with a ring laser gyro based inertial guidance system. This inertial navigation unit (INU) uses two MIL-STD-1750A processors and communicates over the MIL-STD-1553B data bus. Commands are translated into load activation through a Remote Control Unit (RCU) which incorporates the use of solid state relays. Also, a programmable data acquisition system replaces separate multiplexer and signal conditioning units. This modern avionics suite is currently being enhanced through independent research and development programs to provide autonomous rendezvous and docking capability using advanced cruise missile image processing technology and integrated GPS navigational aids. A system concept was developed to combine these technologies in order to achieve a fully autonomous rendezvous, docking, and autoland capability. The current system architecture and the evolution of this architecture using advanced modular avionics concepts being pursued for the National Launch System are discussed.

Method and system for compact, multi-pass pulsed laser amplifier

DOEpatents

Erlandson, Alvin Charles

2014-11-25

A laser amplifier includes an input aperture operable to receive laser radiation having a first polarization, an output aperture coupled to the input aperture by an optical path, and a polarizer disposed along an optical path. A transmission axis of the polarizer is aligned with the first polarization. The laser amplifier also includes n optical switch disposed along the optical path. The optical switch is operable to pass the laser radiation when operated in a first state and to reflect the laser radiation when operated in a second state. The laser amplifier further includes an optical gain element disposed along the optical path and a polarization rotation device disposed along the optical path.

Magnesium Chemistry in the Upper Atmosphere

DTIC Science & Technology

2010-12-20

17,20 Unlike the other prominent meteoric metals (Fe, Na, K and Ca), neither Mg nor Mg+ can be observed by ground-based lidar (laser radar ) as...with a 1200 groove mm-1 grating (resolution 0.12 nm FWHM). Absorption spectra were recorded with a photodiode array (EG&G, PARC 1412) and converted

Solid State Research

DTIC Science & Technology

2005-06-21

266-nm, l-,W, 500-ps laser pulse from a frequency-quadrupled Nd:YAG microchip laser operating at 10 kHz. Fluorescence and elastic scattering from the...on Solid State Research xv Organization xxiii QUANTUM ELECTRONICS 1.1 Fluorescence-Cued Laser -Induced Breakdown Spectroscopy Detection of Bioaerosols...2. ELECTRO-OfI’ICAL MATERIALS AND DEVICES 2.1 Narrow-Linewidth, High-Power 1556-nm Slab-Coupled Optical Waveguide External-Cavity Laser 7 3

[Classification of results of studying blood plasma with laser correlation spectroscopy based on semiotics of preclinical and clinical states].

PubMed

Ternovoĭ, K S; Kryzhanovskiĭ, G N; Musiĭchuk, Iu I; Noskin, L A; Klopov, N V; Noskin, V A; Starodub, N F

1998-01-01

The usage of laser correlation spectroscopy for verification of preclinical and clinical states is substantiated. Developed "semiotic" classifier for solving the problems of preclinical and clinical states is presented. The substantiation of biological algorithms as well as the mathematical support and software for the proposed classifier for the data of laser correlation spectroscopy of blood plasma are presented.

Nanocrystal waveguide (NOW) laser

DOEpatents

Simpson, John T.; Simpson, Marcus L.; Withrow, Stephen P.; White, Clark W.; Jaiswal, Supriya L.

2005-02-08

A solid state laser includes an optical waveguide and a laser cavity including at least one subwavelength mirror disposed in or on the optical waveguide. A plurality of photoluminescent nanocrystals are disposed in the laser cavity. The reflective subwavelength mirror can be a pair of subwavelength resonant gratings (SWG), a pair of photonic crystal structures (PC), or a distributed feedback structure. In the case of a pair of mirrors, a PC which is substantially transmissive at an operating wavelength of the laser can be disposed in the laser cavity between the subwavelength mirrors to improve the mode structure, coherence and overall efficiency of the laser. A method for forming a solid state laser includes the steps of providing an optical waveguide, creating a laser cavity in the optical waveguide by disposing at least one subwavelength mirror on or in the waveguide, and positioning a plurality of photoluminescent nanocrystals in the laser cavity.

Collisional Dynamics, Lasing and Stimulated Raman Scattering in Optically Pumped Cesium and Potassium Vapors

DTIC Science & Technology

2012-03-22

10 4. Three level energy diagram of an OPAL . N0 is a ground S1/2 state, and N1 and N2 are the 2P1/2 and 2P3/2 states, respectively...refer to these lasers by the more general term, OPAL for Optically-Pumped Alkali Laser. An OPAL is a three level laser where the ground state , N0, is...contains the buffer gas and alkali metal vapor. The temperature of OPAL lasers is typically in the range of 90 to 130 ◦C which amounts to a density of about

Extreme plasma states in laser-governed vacuum breakdown.

PubMed

Efimenko, Evgeny S; Bashinov, Aleksei V; Bastrakov, Sergei I; Gonoskov, Arkady A; Muraviev, Alexander A; Meyerov, Iosif B; Kim, Arkady V; Sergeev, Alexander M

2018-02-05

Triggering vacuum breakdown at laser facility is expected to provide rapid electron-positron pair production for studies in laboratory astrophysics and fundamental physics. However, the density of the produced plasma may cease to increase at a relativistic critical density, when the plasma becomes opaque. Here, we identify the opportunity of breaking this limit using optimal beam configuration of petawatt-class lasers. Tightly focused laser fields allow generating plasma in a small focal volume much less than λ 3 and creating extreme plasma states in terms of density and produced currents. These states can be regarded to be a new object of nonlinear plasma physics. Using 3D QED-PIC simulations we demonstrate a possibility of reaching densities over 10 25  cm -3 , which is an order of magnitude higher than expected earlier. Controlling the process via initial target parameters provides an opportunity to reach the discovered plasma states at the upcoming laser facilities.

The harmonic state of quantum cascade lasers: origin, control, and prospective applications [Invited].

PubMed

Piccardo, Marco; Chevalier, Paul; Mansuripur, Tobias S; Kazakov, Dmitry; Wang, Yongrui; Rubin, Noah A; Meadowcroft, Lauren; Belyanin, Alexey; Capasso, Federico

2018-04-16

The recently discovered ability of the quantum cascade laser to produce a harmonic frequency comb has attracted new interest in these devices for both applications and fundamental laser physics. In this review we present an extensive experimental phenomenology of the harmonic state, including its appearance in mid-infrared and terahertz quantum cascade lasers, studies of its destabilization induced by delayed optical feedback, and the assessment of its frequency comb nature. A theoretical model explaining its origin as due to the mutual interaction of population gratings and population pulsations inside the laser cavity will be described. We explore different approaches to control the spacing of the harmonic state, such as optical injection seeding and variation of the device temperature. Prospective applications of the harmonic state include microwave and terahertz generation, picosecond pulse generation in the mid-infrared, and broadband spectroscopy.

Advancement of High Power Quasi-CW Laser Diode Arrays For Space-based Laser Instruments

NASA Technical Reports Server (NTRS)

Amzajerdian, Farzin; Meadows, Byron L.; Baker, nathaniel R.; Baggott, Renee S.; Singh, Upendra N.; Kavaya, Michael J.

2004-01-01

Space-based laser and lidar instruments play an important role in NASA s plans for meeting its objectives in both Earth Science and Space Exploration areas. Almost all the lidar instrument concepts being considered by NASA scientist utilize moderate to high power diode-pumped solid state lasers as their transmitter source. Perhaps the most critical component of any solid state laser system is its pump laser diode array which essentially dictates instrument efficiency, reliability and lifetime. For this reason, premature failures and rapid degradation of high power laser diode arrays that have been experienced by laser system designers are of major concern to NASA. This work addresses these reliability and lifetime issues by attempting to eliminate the causes of failures and developing methods for screening laser diode arrays and qualifying them for operation in space.

Passively Q-switched Nd3+ solid-state lasers with antimonene as saturable absorber.

PubMed

Wang, Mengixa; Zhang, Fang; Wang, Zhengping; Wu, Zhixin; Xu, Xinguang

2018-02-19

Based on the saturable absorption feature of a two-dimensional (2D) nano-material, antimonene, the passively Q-switched operation for solid-state laser was realized for the first time. For the 946 and 1064 nm laser emissions of the Nd:YAG crystal, the Q-switched pulse widths were 209 and 129 ns, and the peak powers were 1.48, 1.77 W, respectively. For the 1342 nm laser emission of the Nd:YVO 4 crystal, the Q-switched pulse width was 48 ns, giving a peak power of 28.17 W. Our research shows that antimonene can be used as a stable, broadband optical modulating device for a solid-state laser, which will be particularly effective for long wavelength operation.

Ultrafast Pulse Sequencing for Fast Projective Measurements of Atomic Hyperfine Qubits

NASA Astrophysics Data System (ADS)

Ip, Michael; Ransford, Anthony; Campbell, Wesley

2015-05-01

Projective readout of quantum information stored in atomic hyperfine structure typically uses state-dependent CW laser-induced fluorescence. This method requires an often sophisticated imaging system to spatially filter out the background CW laser light. We present an alternative approach that instead uses simple pulse sequences from a mode-locked laser to affect the same state-dependent excitations in less than 1 ns. The resulting atomic fluorescence occurs in the dark, allowing the placement of non-imaging detectors right next to the atom to improve the qubit state detection efficiency and speed. We also discuss methods of Doppler cooling with mode-locked lasers for trapped ions, where the creation of the necessary UV light is often difficult with CW lasers.

Elevation scanning laser/multi-sensor hazard detection system controller and mirror/mast speed control components. [roving vehicle electromechanical devices

NASA Technical Reports Server (NTRS)

Craig, J.; Yerazunis, S. W.

1978-01-01

The electro-mechanical and electronic systems involved with pointing a laser beam from a roving vehicle along a desired vector are described. A rotating 8 sided mirror, driven by a phase-locked dc motor servo system, and monitored by a precision optical shaft encoder is used. This upper assembly is then rotated about an orthogonal axis to allow scanning into all 360 deg around the vehicle. This axis is also driven by a phase locked dc motor servo-system, and monitored with an optical shaft encoder. The electronics are realized in standard TTL integrated circuits with UV-erasable proms used to store desired coordinates of laser fire. Related topics such as the interface to the existing test vehicle are discussed.

Effects of Anisotropic Excitation in Laser-Induced Fluorescence Spectroscopy (LIFS)

NASA Astrophysics Data System (ADS)

Fujimoto, Takashi; Goto, Chiaki; Uetani, Yasunori; Fukuda, Kuniya

1985-07-01

Various features of the effect of alignment in the upper-level population on the observed emission-line intensity, i.e., the spatially-anisotropic intensity distribution and polarization, are demonstrated using laser-induced fluorescence spectroscopy on the neon 2p53s-2p53p transitions in a plasma. Disalignment by atomic collision is observed on the 2p2 level, and its rate coefficient is determined as (1.70± 0.03)× 10-10 cm3s-1. The case of hyperfine-structure lines is discussed. Polarization is observed in the hydrogen Balmer α line fluorescence following the laser excitation of the same transition. Conditions are given under which the alignment effect is eliminated or can be neglected. Cases of unpolarized-light excitation and high-intensity excitation are discussed.

Novel Optical SETI Observations of Three Exoplanets

NASA Astrophysics Data System (ADS)

Welsh, Barry; Vallerga, John; Kotze, Marissa; Wheatley, Jonathan

2018-01-01

We report on observations of three nearby stars (Trappist-1, GJ 422 and Wolf 1061) that possess exoplanets located in their respective habitable zones to search for optical signals generated by an advanced alien civilization. Using the photon data collected with the Berkeley Visible Image Tube attached to the 10m Southern African Large Telescope, we searched for very high amplitude events in the pulse height distributions that statistically could only be produced by non-astrophysical means such as an optical laser used for communications purposes.Assuming that a purported ET civilization has access to an orbiting 10m mirror and an optical laser to send signals over the three sight-lines to Earth, we derive upper limits to the output power of their l lasers which might be used for inter-stellar communication.

A 4 U Laser Heterodyne Radiometer for Methane (CH4) and Carbon Dioxide (CO2) Measurements from an Occultation-Viewing CubSat

NASA Technical Reports Server (NTRS)

Wilson, Emily L.; DiGregorio, A. J.; Riot, Vincent J.; Ammons, Mark S.; Bruner, WIlliam W.; Carter, Darrell; Mao, Jianping; Ramanathan, Anand; Strahan, Susan E.; Oman, Luke D.;

Experimental and Simulative Investigation of Laser Transmission Welding under Consideration of Scattering

NASA Astrophysics Data System (ADS)

Devrient, M.; Da, X.; Frick, T.; Schmidt, M.

Laser transmission welding is a well known joining technology for thermoplastics. Because of the needs of lightweight, cost effective and green production thermoplastics are usually filled with glass fibers. These lead to higher absorption and more scattering within the upper joining partner with a negative influence on the welding process. Here an experimental method for the characterization of the scattering behavior of semi crystalline thermoplastics filled with short glass fibers and a finite element model of the welding process capable to consider scattering as well as an analytical model are introduced. The experimental data is used for the numerical and analytical investigation of laser transmission welding under consideration of scattering. The scattering effects of several thermoplastics onto the calculated temperature fields as well as weld seam geometries are quantified.

Laser-induced vibration of a thin soap film.

PubMed

Emile, Olivier; Emile, Janine

2014-09-21

We report on the vibration of a thin soap film based on the optical radiation pressure force. The modulated low power laser induces a counter gravity flow in a vertical free-standing draining film. The thickness of the soap film is then higher in the upper region than in the lower region of the film. Moreover, the lifetime of the film is dramatically increased by a factor of 2. Since the laser beam only acts mechanically on the film interfaces, such a film can be employed in an optofluidic diaphragm pump, the interfaces behaving like a vibrating membrane and the liquid in-between being the fluid to be pumped. Such a pump could then be used in delicate micro-equipment, in chips where temperature variations are detrimental and even in biological systems.

Blue Laser Induced Retinal Injury in a Commercial Pilot at 1300 ft.

PubMed

Gosling, Daniel B; O'Hagan, John B; Quhill, Fahd M

2016-01-01

We report what may be the first evidence-based report of a retinal laser injury to a pilot during commercial flight from a laser device on the ground. Given the significant subjective (blind spot) and objective evidence of focal retinal damage, coupled with the distance involved, we suspect the laser had a radiant power of several watts, known to be injurious to the human retina. An airline pilot presented to our department complaining of a blind spot in the upper left area of his visual field in the right eye (right supero-nasal scotoma) following exposure to a laser beam while performing a landing maneuver of a commercial aircraft. At around 1300 ft (396 m), a blue laser beam from the ground directly entered his right eye, with immediate flash blindness and pain. Spectral domain ocular coherence tomography highlighted a localized area of photoreceptor disruption corresponding to a well demarcated area of hypofluorescence on fundus autofluorescence, representing a focal outer retinal laser injury. Fundus examination a fortnight later revealed a clinically identifiable lesion in the pilot's right eye commensurate with a retinal-laser burn. The case reports highlights the growing threat to the ocular health of airline crew and, potentially, passenger safety due to the lack of regulatory oversight of high powered laser devices obtained from the internet. We strongly believe high powered handheld laser devices should not be in the possession of the general public.

Advances in High Energy Solid-State 2-micron Laser Transmitter Development for Ground and Airborne Wind and CO2 Measurements

NASA Technical Reports Server (NTRS)

Singh, Upendra N.; Yu, Jirong; Petros, Mulugeta; Chen, Songsheng; Kavaya, Michael J.; Trieu, Bo; Bai, Yingxin; Petzar, Paul; Modlin, Edward A.; Koch, Grady;

Progress on High-Energy 2-micron Solid State Laser for NASA Space-Based Wind and Carbon Dioxide Measurements

NASA Technical Reports Server (NTRS)

Singh, Upendra N.

2011-01-01

Sustained research efforts at NASA Langley Research Center during last fifteen years have resulted in significant advancement of a 2-micron diode-pumped, solid-state laser transmitter for wind and carbon dioxide measurements from ground, air and space-borne platforms. 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 system for measuring atmospheric CO2 concentration profiles. Researchers at NASA Langley Research Center have developed a compact, flight capable, high energy, injection seeded, 2-micron laser transmitter for ground and airborne wind and carbon dioxide measurements. It is capable of producing 250 mJ at 10 Hz by an oscillator and one amplifier. This compact laser transmitter was integrated into a mobile trailer based coherent Doppler wind and CO2 DIAL system and was deployed during field measurement campaigns. This paper will give an overview of 2-micron solid-state laser technology development and discuss results from recent ground-based field measurements.

Femtosecond laser-induced formation of submicrometer spikes on a semiconductor substrate

DOEpatents

Mazur, Eric; Shen, Mengyan

2013-12-03

The present invention generally provides a semiconductor substrates having submicron-sized surface features generated by irradiating the surface with ultra short laser pulses. In one aspect, a method of processing a semiconductor substrate is disclosed that includes placing at least a portion of a surface of the substrate in contact with a fluid, and exposing that surface portion to one or more femtosecond pulses so as to modify the topography of that portion. The modification can include, e.g., generating a plurality of submicron-sized spikes in an upper layer of the surface.

UV diode-pumped solid state laser for medical applications

NASA Astrophysics Data System (ADS)

Apollonov, Victor V.; Konstantinov, K. V.; Sirotkin, A. A.

1999-07-01

A compact, solid-state, high-efficiency, and safe UV laser medical system with optical fiber output was created for treatment of destructive forms of pulmonary tuberculosis. A frequency-quadruped quasi-CW Nd:YVO4 laser system pumped by laser-diode array is investigated with various resonator configurations. A longitudinal end-pumping scheme was used in a compact acousto-optical Q-switched laser for producing stable pulses of UV radiation at the repetition frequency 10-20 kHz and the duration 7-10 ns with the fiber-guide output power exceeding 10 mW.

High-power pulse repetitive HF(DF) laser with a solid-state pump generator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Velikanov, S D; Domazhirov, A P; Zaretskiy, N A

2015-11-30

Operation of a repetitively pulsed electric-discharge HF(DF) laser with an all-solid-state pump generator based on FID switches is demonstrated. The energy stored in the pump generator capacitors was 880 J at an open-circuit voltage of 240 kV and a discharge pulse repetition rate of 25 Hz. The specific energy extractions were 3.8 and 3.4 J L{sup -1} for the HF and DF lasers, respectively. The possibilities of improving the output laser characteristics are discussed. (lasers)

Small lasers in flow cytometry.

PubMed

Telford, William G

2004-01-01

Laser technology has made tremendous advances in recent years, particularly in the area of diode and diode-pumped solid state sources. Flow cytometry has been a direct beneficiary of these advances, as these small, low-maintenance, inexpensive lasers with reasonable power outputs are integrated into flow cytometers. In this chapter we review the contribution and potential of solid-state lasers to flow cytometry, and show several examples of these novel sources integrated into production flow cytometers. Technical details and critical parameters for successful application of these lasers for biomedical analysis are reviewed.

Laser interferometric studies of thermal effects of diode-pumped solid state lasing medium

NASA Astrophysics Data System (ADS)

Peng, Xiaoyuan; Asundi, Anand K.; Xu, Lei; Chen, Yihong; Xiong, Zhengjun; Lim, Gnian Cher

2000-04-01

Thermal effects dramatically influence the laser performance of diode-pumped solid state lasers (DPSSL). There are three factors accounting for thermal effects in diode-pumped laser medium: the change of the refractive index due to temperature gradient, the change of the refractive index due to thermal stress, and the change of the physical length due to thermal expansion (end effect), in which the first two effects can be called as thermal parts. A laser interferometer is proposed to measure both the bulk and physical messages of solid-state lasing medium. There are two advantages of the laser interferometry to determine the thermal lensing effect. One is that it allows separating the average thermal lens into thermal parts and end effect. Another is that the laser interferometry provides a non- invasive, full field, high-resolution means of diagnosing such effects by measuring the optical path difference induced by thermal loading in a lasing crystal reliable without disturbing the normal working conditions of the DPSS laser. Relevant measurement results are presented in this paper.

Provenance of upper Triassic sandstone, southwest Iberia (Alentejo and Algarve basins): tracing variability in the sources

NASA Astrophysics Data System (ADS)

Pereira, M. F.; Ribeiro, C.; Gama, C.; Drost, K.; Chichorro, M.; Vilallonga, F.; Hofmann, M.; Linnemann, U.

2017-01-01

Laser ablation ICP-MS U-Pb analyses have been conducted on detrital zircon of Upper Triassic sandstone from the Alentejo and Algarve basins in southwest Iberia. The predominance of Neoproterozoic, Devonian, Paleoproterozoic and Carboniferous detrital zircon ages confirms previous studies that indicate the locus of the sediment source of the late Triassic Alentejo Basin in the pre-Mesozoic basement of the South Portuguese and Ossa-Morena zones. Suitable sources for the Upper Triassic Algarve sandstone are the Upper Devonian-Lower Carboniferous of the South Portuguese Zone (Phyllite-Quartzite and Tercenas formations) and the Meguma Terrane (present-day in Nova Scotia). Spatial variations of the sediment sources of both Upper Triassic basins suggest a more complex history of drainage than previously documented involving other source rocks located outside present-day Iberia. The two Triassic basins were isolated from each other with the detrital transport being controlled by two independent drainage systems. This study is important for the reconstruction of the late Triassic paleogeography in a place where, later, the opening of the Central Atlantic Ocean took place separating Europe from North America.

Laser Program annual report 1987

DOE Office of Scientific and Technical Information (OSTI.GOV)

O'Neal, E.M.; Murphy, P.W.; Canada, J.A.

1989-07-01

This report discusses the following topics: target design and experiments; target materials development; laboratory x-ray lasers; laser science and technology; high-average-power solid state lasers; and ICF applications studies.

Rapid prototyping of reflectors for vehicle lighting using laser activated remote phosphor

NASA Astrophysics Data System (ADS)

Lachmayer, Roland; Kloppenburg, Gerolf; Wolf, Alexander

2015-03-01

Bright white light sources are of significant importance for automotive front lighting systems. Today's upper class vehicles mainly use HID or LED as light source. As a further step in this development laser diode based systems offer high luminance, efficiency and allow the realization of new styling concepts and new dynamic lighting functions. These white laser diode systems can either be realized by mixing different spectral sources or by combining diodes with specific phosphors. Based on the approach of generating light using a laser and remote phosphor, lighting modules are manufactured. Four blue laser diodes (450 nm) are used to activate a phosphor coating and thus to achieve white light. A segmented paraboloid reflector generates the desired light distribution for an additional car headlamp. We use high speed milling and selective laser melting to build the reflector system for this lighting module. We compare the spectral reflection grade of these materials. Furthermore the generated modules are analyzed regarding their efficiency and light distribution. The use of Rapid Prototyping technologies allows an early validation of the chosen concept and is supposed to reduce cost and time in the product development process significantly. Therefor we discuss costs and times of the applied manufacturing technologies.

Computing Radiative Transfer in a 3D Medium

NASA Technical Reports Server (NTRS)

Von Allmen, Paul; Lee, Seungwon

2012-01-01

A package of software computes the time-dependent propagation of a narrow laser beam in an arbitrary three- dimensional (3D) medium with absorption and scattering, using the transient-discrete-ordinates method and a direct integration method. Unlike prior software that utilizes a Monte Carlo method, this software enables simulation at very small signal-to-noise ratios. The ability to simulate propagation of a narrow laser beam in a 3D medium is an improvement over other discrete-ordinate software. Unlike other direct-integration software, this software is not limited to simulation of propagation of thermal radiation with broad angular spread in three dimensions or of a laser pulse with narrow angular spread in two dimensions. Uses for this software include (1) computing scattering of a pulsed laser beam on a material having given elastic scattering and absorption profiles, and (2) evaluating concepts for laser-based instruments for sensing oceanic turbulence and related measurements of oceanic mixed-layer depths. With suitable augmentation, this software could be used to compute radiative transfer in ultrasound imaging in biological tissues, radiative transfer in the upper Earth crust for oil exploration, and propagation of laser pulses in telecommunication applications.

Theoretical study of the characteristics of a continuous wave iron-doped ZnSe laser

NASA Astrophysics Data System (ADS)

Pan, Qikun; Chen, Fei; Xie, Jijiang; Wang, Chunrui; He, Yang; Yu, Deyang; Zhang, Kuo

2018-03-01

A theoretical model describing the dynamic process of a continuous-wave Fe2+:ZnSe laser is presented. The influence of some of the operating parameters on the output characteristics of an Fe2+:ZnSe laser is studied in detail. The results indicate that the temperature rise of the Fe2+:ZnSe crystal is significant with the use of a high power pump laser, especially for a high doped concentration of crystal. The optimal crystal length increases with decreasing the doped concentration of crystal, so an Fe2+:ZnSe crystal with simultaneous doping during growth is an attractive choice, which usually has a low doped concentration and long length. The laser pumping threshold is almost stable at low temperatures, but increases exponentially with a working temperature in the range of 180 K to room temperature. The main reason for this phenomenon is the short upper level lifetime and serious thermal temperature rise when the working temperature is higher than 180 K. The calculated optimum output mirror transmittance is about 35% and the performance of a continuous-wave Fe2+:ZnSe laser is more efficient at a lower operating temperature.

[Analysis of antibiotic diffusion from agarose gel by spectrophotometry and laser interferometry methods].

PubMed

Arabski, Michał; Wasik, Sławomir; Piskulak, Patrycja; Góźdź, Natalia; Slezak, Andrzej; Kaca, Wiesław

2011-01-01

The aim of this study was to analysis of antibiotics (ampicilin, streptomycin, ciprofloxacin or colistin) release from agarose gel by spectrophotmetry and laser interferometry methods. The interferometric system consisted of a Mach-Zehnder interferometer with a He-Ne laser, TV-CCD camera, computerised data acquisition system and a gel system. The gel system under study consists of two cuvettes. We filled the lower cuvette with an aqueous 1% agarose solution with the antibiotics at initial concentration of antibiotics in the range of 0.12-2 mg/ml for spectrophotmetry analysis or 0.05-0.5 mg/ml for laser interferometry methods, while in the upper cuvette there was pure water. The diffusion was analysed from 120 to 2400 s with a time interval of deltat = 120 s by both methods. We observed that 0.25-1 mg/ml and 0,05 mg/ml are minimal initial concentrations detected by spectrophotometric and laser interferometry methods, respectively. Additionally, we observed differences in kinetic of antibiotic diffusion from gel measured by both methods. In conclusion, the laser interferometric method is a useful tool for studies of antibiotic release from agarose gel, especially for substances are not fully soluble in water, for example: colistin.

Intensity-dependent atomic-phase effects in high-order harmonic generation

NASA Astrophysics Data System (ADS)

Peatross, J.; Meyerhofer, D. D.

1995-11-01

The far-field angular distributions of high-order harmonics of a 1054-nm laser, with orders ranging from the lower teens to the upper thirties, have been measured in thin, low-density Ar, Kr, and Xe targets. The 1.25-times-diffraction-limited, 1.4-ps-duration, Gaussian laser pulses were focused to intensities ranging from 3×1013 to 3×1014 W/cm2, using f/70 optics. A gas target localized the gas distribution near the laser focus to a thickness of about 1 mm at pressures as low as 0.3 Torr. The weak focusing geometry and the low gas pressures created experimental conditions for which the harmonics could be thought of as emerging from a plane at the laser focus rather than a three-dimensional volume. The far-field distributions of nearly all of the harmonics exhibit narrow central peaks surrounded by broad wings of about the same angular divergence as the emerging laser beam. The spatial wings are due to an intensity-dependent phase variation among the dipole moments of the individual target atoms. This phase variation gives rise to broad spatial interferences in the scattered light due to the radial and temporal variation of the laser intensity.

Laser-direct-drive program: Promise, challenge, and path forward

DOE Office of Scientific and Technical Information (OSTI.GOV)

Campbell, E. M.; Goncharov, V. N.; Sangster, T. C.

Along with laser-indirect (x-ray)-drive and magnetic-drive target concepts, laser direct drive is a viable approach to achieving ignition and gain with inertial confinement fusion. In the United States, a national program has been established to demonstrate and understand the physics of laser direct drive. The program utilizes the Omega Laser Facility to conduct implosion and coupling physics at the nominally 30-kJ scale and laser–plasma interaction and coupling physics at the MJ scale at the National Ignition Facility. This paper will discuss the motivation and challenges for laser direct drive and the broad-based program presently underway in the United States.

Laser-direct-drive program: Promise, challenge, and path forward

DOE PAGES

Campbell, E. M.; Goncharov, V. N.; Sangster, T. C.; ...

2017-03-19

Along with laser-indirect (x-ray)-drive and magnetic-drive target concepts, laser direct drive is a viable approach to achieving ignition and gain with inertial confinement fusion. In the United States, a national program has been established to demonstrate and understand the physics of laser direct drive. The program utilizes the Omega Laser Facility to conduct implosion and coupling physics at the nominally 30-kJ scale and laser–plasma interaction and coupling physics at the MJ scale at the National Ignition Facility. This paper will discuss the motivation and challenges for laser direct drive and the broad-based program presently underway in the United States.

Transoral laser surgery for laryngeal carcinoma: has Steiner achieved a genuine paradigm shift in oncological surgery?

PubMed

Harris, A T; Tanyi, A; Hart, R D; Trites, J; Rigby, M H; Lancaster, J; Nicolaides, A; Taylor, S M

2018-01-01

Transoral laser microsurgery applies to the piecemeal removal of malignant tumours of the upper aerodigestive tract using the CO 2 laser under the operating microscope. This method of surgery is being increasingly popularised as a single modality treatment of choice in early laryngeal cancers (T1 and T2) and occasionally in the more advanced forms of the disease (T3 and T4), predominantly within the supraglottis. Thomas Kuhn, the American physicist turned philosopher and historian of science, coined the phrase 'paradigm shift' in his groundbreaking book The Structure of Scientific Revolutions. He argued that the arrival of the new and often incompatible idea forms the core of a new paradigm, the birth of an entirely new way of thinking. This article discusses whether Steiner and colleagues truly brought about a paradigm shift in oncological surgery. By rejecting the principle of en block resection and by replacing it with the belief that not only is it oncologically safe to cut through the substance of the tumour but in doing so one can actually achieve better results, Steiner was able to truly revolutionise the management of laryngeal cancer. Even though within this article the repercussions of his insight are limited to the upper aerodigestive tract oncological surgery, his willingness to question other peoples' dogma makes his contribution truly a genuine paradigm shift.

Efficiency and threshold pump intensity of CW solar-pumped solid-state lasers

NASA Technical Reports Server (NTRS)

Hwang, In H.; Lee, Ja H.

1991-01-01

The authors consider the relation between the threshold pumping intensity, the material properties, the resonator parameters, and the ultimate slope efficiencies of various solid-state laser materials for solar pumping. They clarify the relation between the threshold pump intensity and the material parameters and the relation between the ultimate slope efficiency and the laser resonator parameters such that a design criterion for the solar-pumped solid-state laser can be established. Among the laser materials evaluated, alexandrite has the highest slope efficiency of about 12.6 percent; however, it does not seem to be practical for a solar-pumped laser application because of its high threshold pump intensity. Cr:Nd:GSGG is the most promising for solar-pumped lasing. Its threshold pump intensity is about 100 air-mass-zero (AM0) solar constants and its slope efficiency is about 12 percent when thermal deformation is completely prevented.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Albo, Asaf, E-mail: asafalbo@gmail.com; Hu, Qing; Reno, John L.

The mechanisms that limit the temperature performance of GaAs/Al{sub 0.15}GaAs-based terahertz quantum cascade lasers (THz-QCLs) have been identified as thermally activated LO-phonon scattering and leakage of charge carriers into the continuum. Consequently, the combination of highly diagonal optical transition and higher barriers should significantly reduce the adverse effects of both mechanisms and lead to improved temperature performance. Here, we study the temperature performance of highly diagonal THz-QCLs with high barriers. Our analysis uncovers an additional leakage channel which is the thermal excitation of carriers into bounded higher energy levels, rather than the escape into the continuum. Based on this understanding,more » we have designed a structure with an increased intersubband spacing between the upper lasing level and excited states in a highly diagonal THz-QCL, which exhibits negative differential resistance even at room temperature. This result is a strong evidence for the effective suppression of the aforementioned leakage channel.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Albo, Asaf; Hu, Qing; Reno, John L.

The mechanisms that limit the temperature performance of GaAs/Al 0.15GaAs-based terahertz quantum cascade lasers (THz-QCLs) have been identified as thermally activated LO-phonon scattering and leakage of charge carriers into the continuum. Consequently, the combination of highly diagonal optical transition and higher barriers should significantly reduce the adverse effects of both mechanisms and lead to improved temperature performance. Here, we study the temperature performance of highly diagonal THz-QCLs with high barriers. Our analysis uncovers an additional leakage channel which is the thermal excitation of carriers into bounded higher energy levels, rather than the escape into the continuum. Based on this understanding,more » we have designed a structure with an increased intersubband spacing between the upper lasing level and excited states in a highly diagonal THz-QCL, which exhibits negative differential resistance even at room temperature. Furthermore, this result is a strong evidence for the effective suppression of the aforementioned leakage channel.« less

New CO2 laser waveguide systems: advances in surgery of tracheal stenosis

NASA Astrophysics Data System (ADS)

Stasche, Norbert; Bernecker, Frank; Hoermann, Karl

1996-01-01

The carbon dioxide laser is a well established tool in the surgical treatment of laryngeal and tracheal stenosis. Usually the laser beam is applied by a microscope/micromanipulator device. Different types of rigid laryngoscopes and bronchoscopes provide access to nearly every area of larynx, trachea and main bronchi. In order to be treated with this equipment the target tissue has to be in a straight optical axis with the laser beam output at the micromanipulator. We report about one patient who presented with severe dyspnea due to granulation tissue directly below his left vocal cord. He was suffering from tracheomalacia for several years and was successfully treated by tracheostomy and a Montgomery's silicone T-tube as a stent. Then granulation tissue blocked the upper orifice of the Montgomery's T-tube. First removal by a carbon dioxide laser beam through the laryngoscope would have required sacrificing his intact left vocal cord. We removed the obstructing tissue by using the ArthroLaseTM System: the carbon dioxide laser beam was conducted through a 90 degree bent rigid probe, using the tracheostomy as an access. This ArthroLaseTM System was originally designed for arthroscopic surgery. In this special case however it successfully extends the use of the carbon dioxide laser in otolaryngology.

Growth, spectroscopy, and laser performance of a 2.79 μm Cr,Er,Pr:GYSGG radiation-resistant crystal.

PubMed

Luo, Jianqiao; Sun, Dunlu; Zhang, Huili; Guo, Qiang; Fang, Zhongqing; Zhao, Xuyao; Cheng, Maojie; Zhang, Qingli; Yin, Shaotang

2015-09-15

We demonstrate the growth, spectroscopy, and laser performance of a 2.79 μm Cr,Er,Pr:GYSGG radiation-resistant crystal. The lifetimes for the upper laser level (4)I(11/2) and lower laser level (4)I(13/2) are 0.59 and 0.84 ms, respectively, which are due to the doping of the Pr(3+) ions. A maximum pulse energy of 278 mJ operated at 10 Hz and 2.79 μm is obtained when pumped with a flash lamp, which corresponds to the electrical-to-optical efficiency of 0.6% and a slope efficiency of 0.7%. A maximum average power of 2.9 W at 60 Hz is achieved, which corresponds to the electrical-to-optical efficiency of 0.4% and slope efficiency of 0.8%. Compared with a Cr,Er:YSGG crystal, the Cr,Er,Pr:GYSGG crystal can be operated at a higher pulse repetition rate. These results suggest that doping deactivator Pr(3+) ions can effectively decrease the lower laser level lifetime and improve the laser repetition rate. Therefore, the application fields and range of the Cr,Er,Pr:GYSGG laser can be extended greatly due to its properties of radiation resistance and high repetition frequency.

Fractionated laser resurfacing corrects the inappropriate UVB response in geriatric skin.

PubMed

Spandau, Dan F; Lewis, Davina A; Somani, Ally-Khan; Travers, Jeffrey B

2012-06-01

Non-melanoma skin cancer is a disease primarily afflicting geriatric patients as evidenced by the fact that 80% of all non-melanoma skin cancers are diagnosed in patients over the age of 60 years. As such, geriatric skin responds to cancer-inducing UVB irradiation in a manner that allows the establishment of tumor cells. Currently, the only effective treatment for non-melanoma skin cancer is the removal of the tumors after they appear, indicating the need for a more cost-effective prophylactic therapy. Geriatric volunteers were treated with fractionated laser resurfacing therapy on either sun-protected (upper buttocks) or chronically sun-exposed (dorsal forearm) skin. Fractionated laser resurfacing therapy was shown to decrease the occurrence of senescent fibroblasts in geriatric dermis, increase the dermal expression of IGF-1, and correct the inappropriate UVB response observed in untreated geriatric skin. These responses to fractionated laser resurfacing were equal to the effects seen previously using the more aggressive wounding following dermabrasion. Furthermore, fractionated laser resurfacing was equally effective in both sun-protected and sun-exposed skin. The ability of fractionated laser resurfacing treatment to protect against the occurrence of UVB-damaged proliferating keratinocytes indicates the potential of fractionated laser resurfacing to reduce or prevent aging-associated non-melanoma skin cancer.

Fractionated laser resurfacing corrects the inappropriate UVB response in geriatric skin

PubMed Central

Spandau, Dan F; Lewis, Davina A.; Somani, Ally-Khan; Travers, Jeffrey B.

2012-01-01

Non-melanoma skin cancer is a disease primarily afflicting geriatric patients as evidenced by the fact that 80% of all non-melanoma skin cancers are diagnosed in patients over the age of 60 years. As such, geriatric skin responds to cancer-inducing UVB irradiation in a manner that allows the establishment of tumor cells. Currently, the only effective treatment for non-melanoma skin cancer is the removal of the tumors after they appear, indicating the need for a more cost-effective prophylactic therapy. Geriatric volunteers were treated with fractionated laser resurfacing therapy on either sun-protected (upper buttocks) or chronically sun-exposed (dorsal forearm) skin. Fractionated laser resurfacing therapy was demonstrated to decrease the occurrence of senescent fibroblasts in geriatric dermis, increase the dermal expression of insulin-like growth factor-1, and correct the inappropriate UVB response observed in untreated geriatric skin. These responses to fractionated laser resurfacing were equal to the effects seen previously using the more aggressive wounding following dermabrasion. Furthermore, fractionated laser resurfacing was equally effective in both sun-protected and sun-exposed skin. The ability of fractionated laser resurfacing treatment to protect against the occurrence of UVB-damaged proliferating keratinocytes indicates the potential of fractionated laser resurfacing to reduce or prevent aging-associated non-melanoma skin cancer. PMID:22377757

Apparatus for testing high pressure injector elements

NASA Technical Reports Server (NTRS)

Myers, William Neill (Inventor); Scott, Ewell M. (Inventor); Forbes, John C. (Inventor); Shadoan, Michael D. (Inventor)

1995-01-01

An apparatus for testing and evaluating the spray pattern of high pressure fuel injector elements for use in supplying fuel to combustion engines is presented. Prior art fuel injector elements were normally tested by use of low pressure apparatuses which did not provide a purge to prevent mist from obscuring the injector element or to prevent frosting of the view windows; could utilize only one fluid during each test; and had their viewing ports positioned one hundred eighty (180 deg) apart, thus preventing optimum use of laser diagnostics. The high pressure fluid injector test apparatus includes an upper hub, an upper weldment or housing, a first clamp and stud/nut assembly for securing the upper hub to the upper weldment, a standoff assembly within the upper weldment, a pair of window housings having view glasses within the upper weldment, an injector block assembly and purge plate within the upper weldment for holding an injector element to be tested and evaluated, a lower weldment or housing, a second clamp and stud/nut assembly for securing the lower weldment to the upper hub, a third clamp and stud/nut assembly for securing the lower hub to the lower weldment, mechanisms for introducing fluid under high pressure for testing an injector element, and mechanisms for purging the apparatus to prevent frosting of view glasses within the window housings and to permit unobstructed viewing of the injector element.

Apparatus for testing high pressure injector elements

NASA Technical Reports Server (NTRS)

Myers, William Neill (Inventor); Scott, Ewell M. (Inventor); Forbes, John C. (Inventor); Shadoan, Michael D. (Inventor)

1993-01-01

An apparatus for testing and evaluating the spray pattern of high pressure fuel injector elements for use in supplying fuel to combustion engines is presented. Prior art fuel injector elements were normally tested by use of low pressure apparatuses which did not provide a purge to prevent mist from obscuring the injector element or to prevent frosting of the view windows; could utilize only one fluid during each test; and had their viewing ports positioned one hundred eighty (180 deg) apart, thus preventing optimum use of laser diagnostics. The high pressure fluid injector test apparatus includes an upper hub, an upper weldment or housing, a first clamp and stud/nut assembly for securing the upper hub to the upper weldment, a standoff assembly within the upper weldment, a pair of window housings having view glasses within the upper weldment, an injector block assembly and purge plate within the upper weldment for holding an injector element to be tested and evaluated, a lower weldment or housing, a second clamp and stud/nut assembly for securing the lower weldment to the upper weldment, a lower hub, a third clamp and stud/nut assembly for securing the lower hub to the lower weldment, mechanisms for introducing fluid under high pressure for testing an injector element, and mechanisms for purging the apparatus to prevent frosting of view glasses within the window housings and to permit unobstructed viewing of the injector element.

Multiple polarization states of vector soliton in fiber laser

NASA Astrophysics Data System (ADS)

Chen, Weicheng; Xu, Wencheng; Cao, Hui; Han, Dingan

2007-11-01

Vector soliton is obtained in erbium-doped fiber laser via nonlinear polarization rotation techniques. In experiment, we observe the every 4- and 7-pulse sinusoidal peak modulation. Temporal pulse sinusoidal peak modulation owes to evolution behavior of vector solitons in multiple polarization states. The polarizer in the laser modulates the mode-locked pulses with different polarization states into periodical pulse train intensities modulation. Moreover, the increasing pumping power lead to the appearance of the harmonic pulses and change the equivalent beat length to accelerate the polarization rotation. When the laser cavity length is the n-th multiple ratios to the beat length to maintain the mode-locking, the mode-locked vector soliton is in n-th multiple polarization states, exhibiting every n-pulse sinusoidal peak modulation.

Femtosecond solid-state laser based on a few-layered black phosphorus saturable absorber.

PubMed

Su, Xiancui; Wang, Yiran; Zhang, Baitao; Zhao, Ruwei; Yang, Kejian; He, Jingliang; Hu, Qiangqiang; Jia, Zhitai; Tao, Xutang

2016-05-01

In this Letter, a high-quality, few-layered black phosphorus (BP) saturable absorber (SA) was fabricated successfully, and a femtosecond solid-state laser modulated by BP-SA was experimentally demonstrated for the first time, to the best of our knowledge. Pulses as short as 272 fs were achieved with an average output power of 0.82 W, corresponding to the pulse energy of 6.48 nJ and peak power of 23.8 MW. So far, these represent the shortest pulse duration and highest output power ever obtained with a BP-based mode-locked solid-state laser. The results indicate the promising potential of few-layered BP-SA for applications in solid-state femtosecond mode-locked lasers.

Two-photon excitation of 2,5-diphenyloxazole using a low power green solid state laser

NASA Astrophysics Data System (ADS)

Luchowski, Rafal

2011-01-01

This Letter concerns two-photon excitation of 2,5-diphenyloxazole (PPO) upon illumination from a pulsed 532 nm solid state laser, with an average power of 30 mW, and a repetition rate of 20 MHz. A very agreeable emission spectrum position and shape has been achieved for PPO receiving one- and two-photon excitation, which suggests that the same excited state is involved for both excitation modes. Also, a perfect quadratic dependence of laser power in the emission intensity function has been recorded. We tested the application of a small solid state green laser to two-photon induced time-resolved fluorescence, revealing the emission anisotropy of PPO to be considerably higher for two-photon than for one-photon excitation.

Noncontact Acousto-Ultrasonics for Material Characterization

NASA Technical Reports Server (NTRS)

Kautz, Harold E.

1998-01-01

A NdYAG 1064 nm, laser pulse was employed to produce ultrasonic waves in specimens of SiC/SiC and SiC/Ti 6-4 composites which are high temperature materials of interest for aerospace applications. Air coupled transducers were used to detect and collect the signals used for acousto-ultrasonic analysis. Conditions for detecting ultrasonic decay signals were examined. The results were compared to those determined on the same specimens with contact coupling. Some non-contact measurements were made employing conventional air focused detectors. Others were performed with a more novel micromachined capacitance transducer. Concerns of the laser-in technology include potential destructiveness of the laser pulse. Repeated laser pulsing at the same location does lead to deterioration of the ultrasonic signal in some materials, but seems to recover with time. Also, unlike contact AU, the frequency regime employed is a function of laser-material interaction rather than the choice of transducers. Concerns of the air coupled-out technology include the effect of air attenuation. This imposes a practical upper limit to frequency of detection. In the case of the experimental specimens studied ultrasonic decay signals could be imaged satisfactorily.

Application of a compact diode pumped solid-state laser source for quantitative laser-induced breakdown spectroscopy analysis of steel

NASA Astrophysics Data System (ADS)

Tortschanoff, Andreas; Baumgart, Marcus; Kroupa, Gerhard

2017-12-01

Laser-induced breakdown spectroscopy (LIBS) technology holds the potential for onsite real-time measurements of steel products. However, for a mobile and robust LIBS measurement system, an adequate small and ruggedized laser source is a key requirement. In this contribution, we present tests with our compact high-power laser source, which, initially, was developed for ignition applications. The CTR HiPoLas® laser is a robust diode pumped solid-state laser with a passive Q-switch with dimensions of less than 10 cm3. The laser generates 2.5-ns pulses with 30 mJ at a maximum continuous repetition rate of about 30 Hz. Feasibility of LIBS experiments with the laser source was experimentally verified with steel samples. The results show that the laser with its current optical output parameters is very well-suited for LIBS measurements. We believe that the miniaturized laser presented here will enable very compact and robust portable high-performance LIBS systems.

Designing Birefringent Filters For Solid-State Lasers

NASA Technical Reports Server (NTRS)

Monosmith, Bryan

1992-01-01

Mathematical model enables design of filter assembly of birefringent plates as integral part of resonator cavity of tunable solid-state laser. Proper design treats polarization eigenstate of entire resonator as function of wavelength. Program includes software modules for variety of optical elements including Pockels cell, laser rod, quarter- and half-wave plates, Faraday rotator, and polarizers.

Miniature solid-state lasers for pointing, illumination, and warning devices

NASA Astrophysics Data System (ADS)

Brown, D. C.; Singley, J. M.; Yager, E.; Kowalewski, K.; Lotito, B.; Guelzow, J.; Hildreth, J.; Kuper, J. W.

2008-04-01

In this paper we review the current status of and progress towards higher power and more wavelength diverse diode-pumped solid-state miniature lasers. Snake Creek Lasers now offers unprecedented continuous wave (CW) output power from 9.0 mm and 5.6 mm TO type packages, including the smallest green laser in the world, the MicroGreen TM laser, and the highest density green laser in the world, the MiniGreen TM laser. In addition we offer an infrared laser, the MiniIR TM, operating at 1064 nm, and have just introduced a blue Mini laser operating at 473 nm in a 9.0 mm package. Recently we demonstrated over 1 W of output power at 1064 nm from a 12 mm TO type package, and green output power from 300-500 mW from the same 12 mm package. In addition, the company is developing a number of other innovative new miniature CW solid-state lasers operating at 750 nm, 820 nm, 458 nm, and an eye-safe Q-switched laser operating at 1550 nm. We also review recently demonstrated combining volume Bragg grating (VBG) technology has been combined with automatic power control (APC) to produce high power MiniGreen TM lasers whose output is constant to +/- 10 % over a wide temperature range, without the use of a thermoelectric cooler (TEC). This technology is expected to find widespread application in military and commercial applications where wide temperature operation is particularly important. It has immediate applications in laser pointers, illuminators, and laser flashlights, and displays.

Comparative research on medicine application with 0.53-um, 1.06-um, and 1.32-um Nd:YAG lasers

NASA Astrophysics Data System (ADS)

Li, Yahua; Li, Zhenjia; Zhu, Changhong; Huang, Yizhong

1996-09-01

Because of its high power and excellent optical features, laser has almost been applied to everywhere of medical research and clinic. Over the past several years, laser medical has achieved a rapid progress, and laser medical instruments has developed promptly, each new wavelength can be successfully applied in diagnostic and treatment of diseases. Among the medical lasers, Nd:YAG solid-state laser systems have proven useful in surgical use operate, such as neurosurgery, gastroenterology, cardioangiology, urology, gynecology, dermatology and ENT. As with other solid-state lasers, the Nd:YAG laser can be made to emit various wavelengths by means of suitable resonator configurations and some newest solid-state laser technology, pumped by the Krypton lamp, the Nd:YAG laser at room temperature exhibits transition at 1.06 micrometer Nd:YAG, using nonlinear crystal and Q-switch to double its frequency can attain 0.53 micrometer green beam. In our laser systems, the efficiency at 1.06 micrometer is more than 3 percent, an efficiency of 0.5 percent at 1.32 micrometer and 0.53 micrometer can be attained. For a power of 100w at 1.06 micrometer, 15w at 1.32 micrometer and 0.53 micrometer can therefore be produced. All of three kinds Nd:YAG laser hold these characteristics: high output power; optical fiber transition that can be cooperated with endoscope. The paper mainly discusses laser operating characteristics and clinic applications of three kinds wavelengths at 0.53 micrometer 1.06 micrometer and 1.32 micrometer Nd:YAG laser systems.

Experimental AMO physics in undergraduate optics and lasers courses

NASA Astrophysics Data System (ADS)

Hoyt, Chad

2017-04-01

This talk will describe experimental AMO research projects in undergraduate Lasers and Optics courses at Bethel University. The courses, which include a comprehensive lecture portion, are built on open-ended projects that have a novel aspect. Classes begin with four weeks of small student groups rotating between several standard laser and optics laboratory exercises. These may include, for example, alignment and characterization of a helium neon laser and measurements with a Michelson interferometer or a scanning Fabry-Pérot optical cavity. During the following seven weeks of the course, student groups (2-4 people) choose and pursue research questions in the lab. Their work culminates in a group manuscript and a twenty-minute presentation to the class. Projects in the spring, 2016 Optics course included experiments with ultracold lithium atoms in a magneto-optical trap, a prototype, portable, mode-locked erbium fiber laser, a home-built fiber laser frequency comb, double-slit imaging with single photons, and digital holographic tweezers (led by Nathan Lindquist). Projects in the spring, 2015 Lasers course included ultrafast optics with a mode-locked erbium fiber laser, quantum optics, surface plasmon lasers (led by Nathan Lindquist) and a low-cost, near-infrared spectrometer. Several of these projects are related to larger scale, funded research in the physics department. The format and experience in Lasers and Optics is representative of other upper-level courses at Bethel, including Fluid Mechanics and Computer Methods. A physics education research group from the University of Colorado evaluated the spring, 2015 Lasers and 2016 Optics courses. They focused on student experimental attitudes and measurements of student project ownership.

Laser ignition of an experimental combustion chamber with a multi-injector configuration at low pressure conditions

NASA Astrophysics Data System (ADS)

Börner, Michael; Manfletti, Chiara; Kroupa, Gerhard; Oschwald, Michael

2017-09-01

In search of reliable and light-weight ignition systems for re-ignitable upper stage engines, a laser ignition system was adapted and tested on an experimental combustion chamber for propellant injection into low combustion chamber pressures at 50-80 mbar. The injector head pattern consisted of five coaxial injector elements. Both, laser-ablation-driven ignition and laser-plasma-driven ignition were tested for the propellant combination liquid oxygen and gaseous hydrogen. The 122 test runs demonstrated the reliability of the ignition system for different ignition configurations and negligible degradation due to testing. For the laser-plasma-driven scheme, minimum laser pulse energies needed for 100% ignition probability were found to decrease when increasing the distance of the ignition location from the injector faceplate with a minimum of 2.6 mJ. For laser-ablation-driven ignition, the minimum pulse energy was found to be independent of the ablation material tested and was about 1.7 mJ. The ignition process was characterized using both high-speed Schlieren and OH* emission diagnostics. Based on these findings and on the increased fiber-based pulse transport capabilities recently published, new ignition system configurations for space propulsion systems relying on fiber-based pulse delivery are formulated. If the laser ignition system delivers enough pulse energy, the laser-plasma-driven configuration represents the more versatile configuration. If the laser ignition pulse power is limited, the application of laser-ablation-driven ignition is an option to realize ignition, but implies restrictions concerning the location of ignition.

Effects of Penning reactions and excitation rate on the pulsed transverse-discharge neon laser for photodynamic therapy

NASA Astrophysics Data System (ADS)

Yang, C.-H.; Itoh, K.; Tomita, H.; Obara, M.

1995-07-01

Theoretical analysis of the output performance of a transverse discharge pumped neon Penning laser (585.3 nm) using a mixture of Ne/H2 is described. The validity of the kinetic model is confirmed by comparing the results to the experimental discharge and laser performance. It is theoretically shown that the optimum mixing ratio of the Ne/H2 mixture is 1:2.5, and the optimum operating pressure is about 56 Torr. The model also predicts that the intrinsic efficiency reaches a peak of 8.5×10-6 at an excitation rate of 0.5 MW/cm3 under the optimum mixing ratio and operating pressure conditions. At excitation rates in excess of 0.5 MW/cm3 the laser output power is slowly increasing and then saturates due to electron collisional quenching of the upper laser level. The laser power extraction is increased by laser injection seeding in order to rapidly build up the lasing. The improved intrinsic efficiency is about two times higher than without the injection seeding. The improved specific laser output is 8 W/cm3, therefore, a discharge volume of 125 cm3 will be able to generate the peak laser power reaching 1 kW. This power value is sufficient to obtain the same treatment effect as the gold vapor laser used in photodynamic therapy. Moreover, by fitting this model to the experimental results of the laser output energy with a Ne/D2 mixture, it is shown that the Penning ionization rate constant of H2 is larger than that of D2.

Laser technology and applications in gynaecology.

PubMed

Adelman, M R; Tsai, L J; Tangchitnob, E P; Kahn, B S

2013-04-01

The term 'laser' is an acronym for Light Amplification by Stimulated Emission of Radiation. Lasers are commonly described by the emitted wavelength, which determines the colour of the light, as well as the active lasing medium. Currently, over 40 types of lasers have been developed with a wide range of both industrial and medical uses. Gas and solid-state lasers are frequently used in surgical applications, with CO2 and Ar being the most common examples of gas lasers, and the Nd:YAG and KTP:YAG being the most common examples of solid-state lasers. At present, it appears that the CO2, Nd:YAG, and KTP lasers provide alternative methods for achieving similar results, as opposed to superior results, when compared with traditional endoscopic techniques, such as cold-cutting monopolar and bipolar energy. This review focuses on the physics, tissue interaction, safety and applications of commonly used lasers in gynaecological surgery.

An experimental and theoretical study of the A˜ 2A″Π -X˜ 2A' band system of the jet-cooled HBBr/DBBr free radical

NASA Astrophysics Data System (ADS)

Gharaibeh, Mohammed; Clouthier, Dennis J.; Tarroni, Riccardo

2016-06-01

The electronic spectra of the HBBr and DBBr free radicals have been studied in depth. These species were prepared in a pulsed electric discharge jet using a precursor mixture of BBr3 vapor and H2 or D2 in high pressure argon. Transitions to the electronic excited state of the jet-cooled radicals were probed with laser-induced fluorescence and the ground state energy levels were measured from the single vibronic level emission spectra. HBBr has an extensive band system in the red which involves a linear-bent transition between the two Renner-Teller components of what would be a 2Π state at linearity. We have used high level ab initio theory to calculate potential energy surfaces for the bent 2A' ground state and the linear A˜ 2A″Π excited state and we have determined the ro-vibronic energy levels variationally, including spin orbit effects. The correspondence between the computed and experimentally observed transition frequencies, upper state level symmetries, and H and B isotope shifts was used to make reliable assignments. We have shown that the ground state barriers to linearity, which range from 10 000 cm-1 in HBF to 2700 cm-1 in BH2, are inversely related to the energy of the first excited 2Σ (2A') electronic state. This suggests that a vibronic coupling mechanism is responsible for the nonlinear equilibrium geometries of the ground states of the HBX free radicals.

Infrared radiative decay dynamics from the γ 1u (3P2), H 1u (3P1), and 1u (1D2) ion-pair states of I2 observed by a perturbation facilitated optical-optical double resonance technique

NASA Astrophysics Data System (ADS)

Hoshino, Shoma; Araki, Mitsunori; Nakano, Yukio; Ishiwata, Takashi; Tsukiyama, Koichi

2016-01-01

We report the spectroscopic and temporal analyses on the amplified spontaneous emission (ASE) from the single rovibrational levels of the Ω = 1u ion-pair series, γ 1u (3P2), H 1u (3P1), and 1u (1D2), of I2 by using a perturbation facilitated optical-optical double resonance technique through the c 1 Π g ˜ B 3 Π ( 0u + ) hyperfine mixed valence state as the intermediate state. The ASE detected in the infrared region was assigned to the parallel transitions from the Ω = 1u ion-pair states down to the nearby Ω = 1g ion-pair states. The subsequent ultraviolet (UV) fluorescence from the Ω = 1g states was also observed and the relative vibrational populations in the Ω = 1g states were derived through the Franck-Condon simulation of the intensity pattern of the vibrational progression. In the temporal profiles of the UV fluorescence, an obvious delay in the onset of the fluorescence was recognized after the excitation laser pulse. These results revealed that ASE is a dominant energy relaxation process between the Ω = 1u and 1g ion-pair states of I2. Finally, the lifetimes of the relevant ion-pair states were evaluated by temporal analyses of the UV fluorescence. The propensity was found which was the longer lifetime in the upper level of the ASE transitions tends to give intense ASE.

Periodontal treatment with the frequency-doubled Alexandrite laser in dogs

NASA Astrophysics Data System (ADS)

Rechmann, Peter; Hennig, Thomas; Reichart, Peter

2000-03-01

While earlier periodontal investigations have proved the frequency doubled Alexandrite laser to eliminate efficiently and selectively dental calculus as well as bacteria the aim of this study was to demonstrate the safety of this laser for removal of dental calculus with respect to the dental pulp. Four adult Labrador dogs were treated with a frequency doubled Alexandrite laser (laboratory prototype, q-switched, fiber guided, wavelength 377 nm, pulse duration 1 microsecond, pulse repetition rate 70 Hz, water cooling) to remove dental calculus. After performing a modified Widman flap procedure the buccal surface of nine teeth in the lower and upper right jaw were irradiated for four minutes per tooth. Three different laser fluences up to four times higher than the fluence required for calculus removal were used (1.5, 3 and 6 J/cm2). At three other sites of the right jaw deep cavities were prepared with a dental drill and filled with compomere material (DyractR, Dentsply, Germany) to serve as a positive control with regard to possible pulpal reactions. The corresponding teeth of the lower and upper left jaw served as controls. Animals were sacrificed one day, one week, four weeks and six weeks after treatment. Teeth were separated, fixed in formalin and decalcified. After embedding and sectioning the histological sections were stained and investigated by a totally blinded investigator (P.A.R). Histological investigations revealed that irradiation with the frequency doubled Alexandrite laser for periodontal treatment with fluences of 1.5 J/cm2 -- those fluences necessary for the selective removal of dental calculus and microbial plaque -- had no adverse side effects to the pulpal tissues. Moreover this pulpal safety study demonstrated that even applying fluences two or four times higher than those suggested for calculus removal do not lead to observable changes or alterations in the odontoblast cell layer or the pulpal tissues. No inflammatory reactions and no differences between irradiated and control teeth occurred, while the positive controls showed reactions in the odontoblast cell layer and the connective pulpal tissue.

Remote sensing of atmospheric pressure and sea state using laser altimeters

NASA Technical Reports Server (NTRS)

Gardner, C. S.

1985-01-01

Short-pulse multicolor laser ranging systems are currently being developed for satellite ranging applications. These systems use Q-switched pulsed lasers and streak-tube cameras to provide timing accuracies approaching a few picoseconds. Satellite laser ranging systems have been used to evaluate many important geophysical phenomena such as fault motion, polar motion and solid earth tides, by measuring the orbital perturbations of retroreflector equipped satellites. Some existing operational systems provide range resolution approaching a few millimeters. There is currently considerable interest in adapting these highly accurate systems for use as airborne and satellite based altimeters. Potential applications include the measurement of sea state, ground topography and atmospheric pressure. This paper reviews recent progress in the development of multicolor laser altimeters for use in monitoring sea state and atmospheric pressure.

The effect of p-doping on multi-state lasing in InAs/InGaAs quantum dot lasers for different cavity lengths

NASA Astrophysics Data System (ADS)

Korenev, V. V.; Savelyev, A. V.; Maximov, M. V.; Zubov, F. I.; Shernyakov, Yu M.; Zhukov, A. E.

2017-11-01

The effect of modulation p-doping on multi-state lasing in InAs/InGaAs quantum dot (QD) lasers is studied for different levels of acceptor concentration. It is shown that in case of the short laser cavities, p-doping results in higher output power of the ground-state optical transitions of InAs/InGaAs QDs whereas in longer samples p-doping may result in the decrease of this power component. On the basis of this observation, the optimal design of laser active region and optimal doping level are discussed in details.

Parasitic oscillation suppression in solid state lasers using absorbing thin films

DOEpatents

Zapata, L.E.

1994-08-02

A thin absorbing film is bonded onto at least certain surfaces of a solid state laser gain medium. An absorbing metal-dielectric multilayer film is optimized for a broad range of incidence angles, and is resistant to the corrosive/erosive effects of a coolant such as water, used in the forced convection cooling of the film. Parasitic oscillations hamper the operation of solid state lasers by causing the decay of stored energy to amplified rays trapped within the gain medium by total and partial internal reflections off the gain medium facets. Zigzag lasers intended for high average power operation require the ASE absorber. 16 figs.

Parasitic oscillation suppression in solid state lasers using absorbing thin films

DOEpatents

Zapata, Luis E.

1994-01-01

A thin absorbing film is bonded onto at least certain surfaces of a solid state laser gain medium. An absorbing metal-dielectric multilayer film is optimized for a broad range of incidence angles, and is resistant to the corrosive/erosive effects of a coolant such as water, used in the forced convection cooling of the film. Parasitic oscillations hamper the operation of solid state lasers by causing the decay of stored energy to amplified rays trapped within the gain medium by total and partial internal reflections off the gain medium facets. Zigzag lasers intended for high average power operation require the ASE absorber.

Nuclear-Pumped Lasers. [efficient conversion of energy liberated in nuclear reactions to coherent radiation

NASA Technical Reports Server (NTRS)

1979-01-01

The state of the art in nuclear pumped lasers is reviewed. Nuclear pumped laser modeling, nuclear volume and foil excitation of laser plasmas, proton beam simulations, nuclear flashlamp excitation, and reactor laser systems studies are covered.

High energy efficient solid state laser sources

NASA Technical Reports Server (NTRS)

Byer, Robert L.

1987-01-01

Diode-laser-pumped solid-state laser oscillators and nonlinear processes were investigated. A new generation on nonplanar oscillator was fabricated, and it is anticipated that passive linewidths will be pushed to the kilohertz regime. A number of diode-pumped laser transitions were demonstrated in the rod configuration. Second-harmonic conversion efficiencies as high as 15% are routinely obtained in a servo-locked external resonant doubling crystal at 15 mW cw input power levels at 1064 nm.

Quantification of incisal tooth wear in upper anterior teeth: conventional vs new method using toolmakers microscope and a three-dimensional measuring technique.

PubMed

Al-Omiri, Mahmoud K; Sghaireen, Mohd G; Alzarea, Bader K; Lynch, Edward

2013-12-01

This study aimed to quantify tooth wear in upper anterior teeth using a new CAD-CAM Laser scanning machine, tool maker microscope and conventional tooth wear index. Fifty participants (25 males and 25 females, mean age = 25 ± 4 years) were assessed for incisal tooth wear of upper anterior teeth using Smith and Knight clinical tooth wear index (TWI) on two occasions, the study baseline and 1 year later. Stone dies for each tooth were prepared and scanned using the CAD-CAM Laser Cercon System. Scanned images were printed and examined under a toolmaker microscope to quantify tooth wear and then the dies were directly assessed under the microscope to measure tooth wear. The Wilcoxon Signed Ranks Test was used to analyze the data. TWI scores for incisal edges were 0-3 and were similar at both occasions. Score 4 was not detected. Wear values measured by directly assessing the dies under the toolmaker microscope (range = 113 - 150 μm, mean = 130 ± 20 μm) were significantly more than those measured from Cercon Digital Machine images (range=52-80 μm, mean = 68 ± 23 μm) and both showed significant differences between the two occasions. Wear progression in upper anterior teeth was effectively detected by directly measuring the dies or the images of dies under toolmaker microscope. Measuring the dies of worn dentition directly under tool maker microscope enabled detection of wear progression more accurately than measuring die images obtained with Cercon Digital Machine. Conventional method was the least sensitive for tooth wear quantification and was unable to identify wear progression in most cases. Copyright © 2013 Elsevier Ltd. All rights reserved.

How does multilevel upper airway surgery influence the lives of dogs with severe brachycephaly? Results of a structured pre- and postoperative owner questionnaire.

PubMed

Pohl, Sabine; Roedler, Frauke S; Oechtering, Gerhard U

2016-04-01

Brachycephalic airway syndrome in dogs is typified by a variety of anatomical abnormalities causing a diverse spectrum of clinical signs of varying intensity. This variability makes the assessment of the surgical outcome after upper airway surgery difficult. Using a structured questionnaire, the present study investigated the dog owner-perceived severity and frequency of a broad spectrum of welfare-relevant impairments 2 weeks before and 6 months after brachycephalic dogs underwent a recently developed multi-level upper airway surgery. All dogs underwent surgical treatment of stenotic nares (ala-vestibuloplasty), the nasal cavity (laser-assisted turbinectomy, LATE), the pharynx (palatoplasty and tonsillotomy), and if indicated, laryngeal surgery (laser-assisted ablation of everted ventricles and partial cuneiformectomy). Owners of brachycephalic dogs (n = 102) referred for upper airway surgery were eligible to participate. Questionnaire data from owners of 37 Pugs and 25 French bulldogs were evaluated. In all dogs, the clinical signs associated with brachycephaly improved markedly after surgery. Most encouraging was the striking reduction in life-threatening events by 90% (choking fits decreased from 60% to 5% and collapse from 27% to 3%). The incidence of sleeping problems decreased from 55% to 3%, and the occurrence of breathing sounds declined by approximately 50%. There was a marked improvement in exercise tolerance and a modest improvement in heat tolerance. Dogs with severe brachycephaly benefitted substantially from multi-level surgery, and there were particular improvements in the incidences of severe impairment and life-threatening events. However, despite the marked improvement perceived by dog owners, these dogs remained clinically affected and continued to show welfare-relevant impairments caused by these hereditary disorders. Copyright © 2016 Elsevier Ltd. All rights reserved.

The selective and efficient laser ion source and trap project LIST for on-line production of exotic nuclides

NASA Astrophysics Data System (ADS)

Wendt, Klaus; Gottwald, Tina; Hanstorp, Dag; Mattolat, Christoph; Raeder, Sebastian; Rothe, Sebastian; Schwellnus, Fabio; Havener, Charles; Lassen, Jens; Liu, Yuan

2010-02-01

Laser ion sources based on resonant excitation and ionization of atoms are well-established tools for selective and efficient production of radioactive ion beams. A recent trend is the complementary installation of reliable state-of-the-art all solid-state Ti:Sapphire laser systems. To date, 35 elements of the Periodic Table are available at laser ion sources by using these novel laser systems, which complements the overall accessibility to 54 elements including use of traditional dye lasers. Recent progress in the field concerns the identification of suitable optical excitation schemes for Ti:Sapphire laser excitation as well as technical developments of the source in respect to geometry, cavity material as well as by incorporation of an ion guide system in the form of the laser ion source trap LIST.

How to manage continuing education and retraining programs on optical physics and laser technology at a university: Moscow State experience

NASA Astrophysics Data System (ADS)

Zadkov, Victor N.; Koroteev, Nikolai I.

1995-10-01

An experience of managing the continuing education and retraining programs at the International Laser Center (ILC) of Moscow State University is discussed. The offered programs are in a wide range of areas, namely laser physics and technology, laser biophysics and biomedicine, laser chemistry, and computers in laser physics. The attendees who are presumably scientists, engineers, technical managers, and graduate students can join these programs through the annual ILC term (6 months), individual training and research programs (up to a year), annual ILC Laser Graduate School, graduate study, and post-docs program, which are reviewed in the paper. A curriculum that includes basic and specialized courses is described in detail. A brief description of the ILC Laser Teaching and Computer Labs that support all the educational courses is given as well.

Coherent Doppler lidar for automated space vehicle, rendezvous, station-keeping and capture

NASA Technical Reports Server (NTRS)

Dunkin, James A.

1991-01-01

Recent advances in eye-safe, short wavelength solid-state lasers offer real potential for the development of compact, reliable, light-weight, efficient coherent lidar. Laser diode pumping of these devices has been demonstrated, thereby eliminating the need for flash lamp pumping, which has been a major drawback to the use of these lasers in space based applications. Also these lasers now have the frequency stability required to make them useful in coherent lidar, which offers all of the advantages of non-coherent lidar, but with the additional advantage that direct determination of target velocity is possible by measurement of the Doppler shift. By combining the Doppler velocity measurement capability with the inherent high angular resolution and range accuracy of lidar it is possible to construct Doppler images of targets for target motion assessment. A coherent lidar based on a Tm,Ho:YAG 2-micrometer wavelength laser was constructed and successfully field tested on atmospheric targets in 1990. This lidar incorporated an all solid state (laser diode pumped) master oscillator, in conjunction with a flash lamp pumped slave oscillator. Solid-state laser technology is rapidly advancing, and with the advent of high efficiency, high power, semiconductor laser diodes as pump sources, all-solid-state, coherent lidars are a real possibility in the near future. MSFC currently has a feasibility demonstration effort under way which will involve component testing, and preliminary design of an all-solid-state, coherent lidar for automatic rendezvous, and capture. This two year effort, funded by the Director's Discretionary Fund is due for completion in 1992.

Multi-pulse operation of a dissipative soliton fibre laser based on nonlinear polarisation rotation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yu, H L; Wang, X L; Zhou, P

We report an experimental observation of multiple dissipative soliton (DS) operation states in an all-normal-dispersion passively mode-locked Yb-doped fibre laser, including DS bound and oscillating states. In the bound state, multiple DSs up to 11 can coexist in the cavity. In the oscillating state, the DSs' movements are not purely random and three typical states are generalised and illustrated. A single-pulse mode-locked state is established at a high pump power by carefully adjusting the polarisation controllers. The broad spectrum indicates that it may be noise-like pulses, which can serve as a pump to generate a supercontinuum. (control of laser radiationmore » parameters)« less

Workshop on Squeezed States and Uncertainty Relations

NASA Technical Reports Server (NTRS)

Han, Daesoo (Editor); Kim, Y. S. (Editor); Zachary, W. W. (Editor)

1992-01-01

The proceedings from the workshop are presented, and the focus was on the application of squeezed states. There are many who say that the potential for industrial applications is enormous, as the history of the conventional laser suggests. All those who worked so hard to produce squeezed states of light are continuing their efforts to construct more efficient squeezed-state lasers. Quite naturally, they are looking for new experiments using these lasers. The physical basis of squeezed states is the uncertainty relation in Fock space, which is also the basis for the creation and annihilation of particles in quantum field theory. Indeed, squeezed states provide a unique opportunity for field theoreticians to develop a measurement theory for quantum field theory.

Thulium Laser Treatment of Upper Urinary Tract Carcinoma: A Multi-Institutional Analysis of Surgical and Oncological Outcomes.

PubMed

Musi, Gennaro; Mistretta, Francesco A; Marenghi, Carlo; Russo, Andrea; Catellani, Michele; Nazzani, Sebastiano; Conti, Andrea; Luzzago, Stefano; Ferro, Matteo; Matei, Deliu V; Carmignani, Luca; de Cobelli, Ottavio

2018-03-01

To evaluate the efficacy and safety of ureteroscopic thulium laser (TL) treatment of upper urinary tract carcinoma (UTUC). Forty-two consecutive patients underwent conservative TL treatment for UTUC at two referral institutions. All patients underwent preliminary biopsy and then laser vaporization. A 272 μm and 365 μm laser fibers were used with a flexible and semirigid scope, respectively. Ablation was carried out with a 10 to 20 W power. Mean age at surgery was 68 years (SD 10.7). Mean tumor size was 14.3 mm (range 2-30 mm). Preliminary biopsy revealed the presence of low-grade disease in 29 (69.1%) patients, high-grade disease in 4 (9.5%) and 1 carcinoma in situ 1 (2.4%), whereas it was not conclusive in 8 (19%) cases. Final stage was pTa and pTis in 41 (97.6%) and 1 (2.4%) patients, respectively. Thirty eight percent (16) experienced Clavien-Dindo grade I complication, 47.6% (20) grade II, and 2.4% (1) grade III. Five (12%) patients underwent a second-look procedure due to residual disease. Eight (19%) patients experienced clinical recurrence. The median estimated recurrence-free survival was 44 months (SE 3.68). Four patients (9.5%) underwent a nephroureterectomy. Final pathological stage was pTis, pT3 high grade, pTa low grade, and pT0. Median follow-up was 26.3 months (range 2-54 months), and no progression or upstaging of disease occurred. TL management of UTUC is a safe and efficacious conservative treatment. Our experience shows optimal vaporization and hemostatic control in the absence of major complications.

Direct control of transitions between different mode-locking states of a fiber laser

NASA Astrophysics Data System (ADS)

Ilday, Fatih; Teamir, Tesfay; Iegorov, Roman; Makey, Ghaith

Mode-locking corresponds to a far-from-equilibrium steady state of a laser, whereby extremely short pulses can be produced. Capability to directly control mode-locking states can be used to improve laser performance with numerous applications, as well as shed light on their far-from-equilibrium physics using the laser as an experimental platform. Here, we demonstrate direct control of the mode-locking state using spectral pulse shaping by incorporating a spatial light modulator at a Fourier plane inside the cavity of an Yb-doped fiber laser. We show that we can halt and restart mode-locking, suppress instabilities, induce controlled reversible and irreversible transitions between mode-locking states, and perform advanced pulse shaping on pulses as short as 40 fs. This capability can be used to experimentally investigate bifurcations, reversible and irreversible transitions, by selecting, steering, and even competing various mode-locking states. Such studies can explore collective dynamics of dissipative soliton molecules, and ultimately test emerging theories about far-from-equilibrium physics, where there is an acute lack of experimental systems that are sufficiently well controlled. ERC CoG 617521, TUBITAK 113F319.

Imunolocalization of delta-giardin within the ventral disc of Giardia duodenalis using laser scanning confocal microscopy

USDA-ARS?s Scientific Manuscript database

Giardia duodenalis is a ubiquitous protozoan parasite that colonizes the upper small intestine of humans and animals causing diarrheal disease. To maintain infection within the small intestine, trophozoites (the replicative stage of the parasite) attach to the epithelial layer of the gut and resist ...

Particle-image Velocimetry (PIV)

NASA Image and Video Library

2015-05-12

Particle-image velocimetry (PIV) is performed on the upper surface of a pitching airfoil in the NASA Glenn Icing Research Tunnel. PIV is a laser-based flow velocity measurement technique used widely in wind tunnels. These experiments were conducted as part of a research project focused on enhancing rotorcraft speed, efficiency and maneuverability by suppressing dynamic stall.

Search for gravitational waves from compact binary coalescence in LIGO and Virgo data from S5 and VSR1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abadie, J.; Abbott, B. P.; Abbott, R.

We report the results of the first search for gravitational waves from compact binary coalescence using data from the Laser Interferometer Gravitational-Wave Observatory and Virgo detectors. Five months of data were collected during the Laser Interferometer Gravitational-Wave Observatory's S5 and Virgo's VSR1 science runs. The search focused on signals from binary mergers with a total mass between 2 and 35M{sub {center_dot}}. No gravitational waves are identified. The cumulative 90%-confidence upper limits on the rate of compact binary coalescence are calculated for nonspinning binary neutron stars, black hole-neutron star systems, and binary black holes to be 8.7x10{sup -3} yr{sup -1} L{submore » 10}{sup -1}, 2.2x10{sup -3} yr{sup -1} L{sub 10}{sup -1}, and 4.4x10{sup -4} yr{sup -1} L{sub 10}{sup -1}, respectively, where L{sub 10} is 10{sup 10} times the blue solar luminosity. These upper limits are compared with astrophysical expectations.« less

New primordial-magnetic-field limit from the latest LIGO S5 data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, S.

Since the energy momentum tensor of a magnetic field always contains a spin-2 component in its anisotropic stress, stochastic primordial magnetic field (PMF) in the early universe must generate stochastic gravitational-wave (GW) background. This process will greatly affect the relic gravitational wave (RGW), which is one of the major scientific goals of the laser interferometer GW detections. Recently, the fifth science (S5) run of laser interferometer gravitational-wave observatory (LIGO) gave a latest upper limit {Omega}{sub GW}<6.9x10{sup -6} on the RGW background. Utilizing this upper limit, we derive new PMF limits: for a scale of galactic cluster {lambda}=1 Mpc, the amplitudemore » of PMF, that produced by the electroweak phase transition, has to be weaker than B{sub {lambda}{<=}4}x10{sup -7} G; for a scale of supercluster {lambda}=100 Mpc, the amplitude of PMF has to be weaker than B{sub {lambda}{<=}9}x10{sup -11} G. In this manner, GW observation has potential to make interesting contributions to the study of primordial magnetic field.« less

Preservation of Gaussian state entanglement in a quantum beat laser by reservoir engineering

NASA Astrophysics Data System (ADS)

Qurban, Misbah; Islam, Rameez ul; Ge, Guo-Qin; Ikram, Manzoor

2018-04-01

Quantum beat lasers have been considered as sources of entangled radiation in continuous variables such as Gaussian states. In order to preserve entanglement and to minimize entanglement degradation due to the system’s interaction with the surrounding environment, we propose to engineer environment modes through insertion of another system in between the laser resonator and the environment. This makes the environment surrounding the two-mode laser a structured reservoir. It not only enhances the entanglement among two modes of the laser but also preserves the entanglement for sufficiently longer times, a stringent requirement for quantum information processing tasks.

Microchip solid-state cylindrical vector lasers with orthogonally polarized dual laser-diode end pumping.

PubMed

Otsuka, Kenju; Chu, Shu-Chun

2013-05-01

We report a simple method for generating cylindrical vector beams directly from laser-diode (LD)-pumped microchip solid-state lasers by using dual end-pumping beams. Radially as well as azimuthally polarized vector field emissions have been generated from the common c-cut Nd:GdVO4 laser cavity merely by controlling the focus positions of orthogonally polarized LD off-axis pump beams. Hyperbolically polarized vector fields have also been observed, in which the cylindrical symmetry of vector fields is broken. Experimental results have been well reproduced by numerical simulations.

Open-ended projects in undergraduate optics and lasers courses

NASA Astrophysics Data System (ADS)

Hoyt, Chad

This talk will describe the format and experience of undergraduate Lasers and Optics courses at Bethel University. The courses, which include a rigorous lecture portion, are built on open-ended research projects that have a novel aspect. They begin with four weeks of small student groups rotating between several standard laser and optics laboratory exercises. These may include, for example, alignment and characterization of a helium neon laser and measurements with a Michelson interferometer or a scanning Fabry-Pérot optical cavity. During the following seven weeks of the course, student groups (2-4 people) choose and pursue research questions in the lab. Their work culminates in a group manuscript typeset in and a twenty-minute presentation to the class. Projects in the spring, 2014 Optics course included experiments with ultracold lithium atoms in a magneto-optical trap, optical tweezers, digital holography and adaptive optics. Projects in the spring, 2015 Lasers course included ultrafast optics with a mode-locked erbium fiber laser, quantum optics, surface plasmon lasers (led by Nathan Lindquist) and a low-cost, near-infrared spectrometer. Several of these projects are related to larger scale, funded research in the physics department. The format and experience in Lasers and Optics is representative of other upper-level courses at Bethel, including Fluid Mechanics and Computer Methods. A physics education research group from the University of Colorado evaluated the spring, 2015 Lasers course. They focused on student experimental attitudes and measurements of student project ownership.

Diagnosis and kidney-sparing treatments for upper tract urothelial carcinoma: state of the art.

PubMed

Territo, Angelo; Foerster, Bear; Shariat, Shahrokh F; Rouprêt, Morgan; Gaya, Jose M; Palou, Joan; Breda, Alberto

2018-02-01

Conservative management of upper tract urothelial cancer (UTUC) is becoming increasingly popular: the key to success is correct selection of patients with low-risk UTUC based on size (≤ 2 cm), focality (single lesion), stage (< T2), and grade (low grade). Despite the recent growing interest in the conservative approach to UTUC, the diagnostic process is still a challenge, and kidney-sparing surgery (KSS) is traditionally reserved for patients with contraindications to radical nephroureterectomy. In order to explore the "state of the art" in the diagnosis and conservative treatment of UTUC, a systematic review of the literature was performed. A PubMed, Scopus, and Cochrane search for peer-reviewed studies was performed using the keywords "upper tract urothelial carcinoma" OR "UTUC" OR "upper urinary tract" AND "biopsy" OR "diagnosis" OR "endomicroscopy" OR "imaging" AND "URS" OR "ureteroscopy" OR "kidney-sparing surgery" OR "laser ablation" OR "ureterectomy". We considered as relevant comparative prospective studies (randomized, quasi-randomized, no randomized), retrospective studies, meta-analyses, systematic reviews, and case report series written in the English language. Letters to the editor and contributions written in languages other than English were not considered of value for this review. Eligible articles were reviewed according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) criteria. Two hundred and sixty-three (263) records were identified using the above-mentioned keywords. Overall, 30 studies were considered relevant for the purpose of this systematic review and for the evidence evaluation process during qualitative synthesis. The outcomes evaluated in this review were the current diagnostic methods and the KSS approaches in UTUC. Furthermore, we included in the review the emerging technology for distinguishing between normal tissue, low-grade UTUC, and high-grade UTUC. Conclusive diagnosis is fundamental to the decision-making process in patients who could benefit from conservative treatment of UTUC. The most relevant diagnostic modalities are computed tomography urography, local urine cytology, and ureteroscopy with acquisition of an adequate biopsy sample for histology. KSS includes the endourological approach and segmental ureterectomy. Promising technology in the endourological management of UTUC helps in providing intraoperative information on UTUC grading and staging, with a high accuracy. Patients treated conservatively have to undergo stringent postoperative follow-up in order to detect and, if necessary, treat any recurrence promptly. Further larger and multicenter studies are needed to confirm these findings.

Solid-State Laser Source of Tunable Narrow-Bandwidth Ultraviolet Radiation

NASA Technical Reports Server (NTRS)

Goldberg, Lew; Kliner, Dahv A.; Koplow, Jeffrey P.

1998-01-01

A solid-state laser source of tunable and narrow-bandwidth UV light is disclosed. The system relies on light from a diode laser that preferably generates light at infrared frequencies. The light from the seed diode laser is pulse amplified in a light amplifier, and converted into the ultraviolet by frequency tripling, quadrupling, or quintupling the infrared light. The narrow bandwidth, or relatively pure light, of the seed laser is preserved, and the pulse amplifier generates high peak light powers to increase the efficiency of the nonlinear crystals in the frequency conversion stage. Higher output powers may be obtained by adding a fiber amplifier to power amplify the pulsed laser light prior to conversion.

A model for the kinetics of a solar-pumped long path laser experiment

NASA Technical Reports Server (NTRS)

Stock, L. V.; Wilson, J. W.; Deyoung, R. J.

1986-01-01

A kinetic model for a solar-simulator pumped iodine laser system is developed and compared to an experiment in which the solar simulator output is dispersed over a large active volume (150 cu cm) with low simulator light intensity (approx. 200 solar constants). A trace foreign gas which quenches the upper level is introduced into the model. Furthermore, a constant representing optical absorption of the stimulated emission is introduced, in addition to a constant representing the scattering at each of the mirrors, via the optical cavity time constant. The non-uniform heating of the gas is treated as well as the pressure change as a function of time within the cavity. With these new phenomena introduced into the kinetic model, a best reasonable fit to the experimental data is found by adjusting the reaction rate coefficients within the range of known uncertainty by numerical methods giving a new bound within this range of uncertainty. The experimental parameters modeled are the lasing time, laser pulse energy, and time to laser threshold.

Analysis of a 10 megawatt space-based solar-pumped neodymium laser system

NASA Technical Reports Server (NTRS)

Kurweg, U. H.

1984-01-01

A ten megawatt solar-pumped continuous liquid laser system for space applications is examined. It is found that a single inflatable mirror of 434 m diameter used in conjunction with a conical secondary concentrator is sufficient to side pump a liquid neodymium lasant in an annular tube of 6 m length and 1 m outer and 0.8 m inner diameter. About one fourth of intercepted radiation converging on the laser tube is absorbed and one fifth of this radiation is effective in populating the upper levels. The liquid lasant is flowed through the annular laser cavity at 1.9 m/s and is cooled via a heat exchanger and a large radiator surface comparable in size to the concentrating mirror. The power density of incident light within the lasant of approximately 68 watt/cu cm required for cw operation is exceeded in the present annular configuration. Total system weight corresponds to 20,500 kg and is thus capable of being transported to near Earth orbit by a single shuttle flight.

Effect of pumping delay on the modulation bandwidth in double tunneling-injection quantum dot lasers.

PubMed

Asryan, Levon V

2017-01-01

The modulation bandwidth of double tunneling-injection (DTI) quantum dot (QD) lasers is studied, taking into account noninstantaneous pumping of QDs. In this advanced type of semiconductor lasers, carriers are first captured from the bulk waveguide region into two-dimensional regions (quantum wells [QWs]); then they tunnel from the QWs into zero-dimensional regions (QDs). The two processes are noninstantaneous and, thus, could delay the delivery of the carriers to the QDs. Here, the modulation bandwidth of DTI QD lasers is calculated as a function of two characteristic times (the capture time from the waveguide region into the QW and the tunneling time from the QW into the QD ensemble) and is shown to increase as either of these times is reduced. The capture and tunneling times of 1 and 0.1 ps, respectively, are shown to characterize fast capture and tunneling processes; as the capture and tunneling times are brought below 1 and 0.1 ps, the bandwidth remains almost unchanged and close to its upper limit.

The operations of quantum logic gates with pure and mixed initial states.

PubMed

Chen, Jun-Liang; Li, Che-Ming; Hwang, Chi-Chuan; Ho, Yi-Hui

2011-04-07

The implementations of quantum logic gates realized by the rovibrational states of a C(12)O(16) molecule in the X((1)Σ(+)) electronic ground state are investigated. Optimal laser fields are obtained by using the modified multitarget optimal theory (MTOCT) which combines the maxima of the cost functional and the fidelity for state and quantum process. The projection operator technique together with modified MTOCT is used to get optimal laser fields. If initial states of the quantum gate are pure states, states at target time approach well to ideal target states. However, if the initial states are mixed states, the target states do not approach well to ideal ones. The process fidelity is introduced to investigate the reliability of the quantum gate operation driven by the optimal laser field. We found that the quantum gates operate reliably whether the initial states are pure or mixed.

Pulp histology after Er:YAG laser cavity preparation in subhuman primates--a pilot study.

PubMed

Louw, N P; Pameijer, C H; Ackermann, W D; Ertl, T; Cappius, H J; Norval, G

2002-08-01

The aim of the study was to make a direct comparison of the pulpal effects of laser and turbine preparations in subhuman primates. One female baboon (Papio Ursinus ursinus), weighing 15 kg, was used. General anaesthesia was administered (ketamine 100 mg/ml/kg body weight) and maintained with acepromazine (10 mg/ml/kg body weight). Class V cavities were prepared buccally in a total of 28 teeth (7 in each quadrant). Teeth in the upper right and lower left quadrants were prepared using a conventional 330 carbide bur in a high-speed fibre-optic handpiece with copious water spray. Teeth in the upper left and lower right quadrants were prepared using an Er:YAG laser drill (Fotona Twinlight, Llubljana, Slovenia) delivering 500 mJ at a pulse rate of 10 Hz and a wavelength of 2940 nm. The animal was sacrificed after 25 days. After general anaesthesia as described before, perfusion fixation of the head was accomplished with 10% neutral buffered formalin, pumped through a catheter inserted into the left carotid artery. The jaws were removed and, using a 330 carbide bur in a high speed handpiece, a continuous groove was cut through the bone and the roots at the level of the middle third of all the roots to promote thorough fixation of pulpal tissue. Decalcification and grading of the severity of the pulpal responses were conducted according to standard procedures. Owing to procedural errors seven teeth, FDI numbers 23, 24, 31, 34, 35, 44 and 45, had to be eliminated. The turbine-prepared teeth (N = 11) had a mean remaining dentine thickness (RDT) of 0.77 mm (SD = 0.42) and the laser-prepared teeth (N = 10) had a mean RDT of 0.81 mm (SD = 0.60). All pulps appeared normal except in one turbine-prepared tooth (12 with RDT = 0.20) and one laser-prepared tooth (27 with RDT = 0.30, where irreversible damage was caused. The only other deviations from normal were seen in the laser-treated 41 (RDT = 0.69) and the turbine-treated 36 (RDT = 0.77) where moderate hyperaemia was seen. Within the limitations of this study it can be concluded that there is no significant difference between dental pulp of teeth where Class V cavities were prepared with an Er:YAG laser drill compared with those prepared with a standard turbine drill.

Research Laboratory of Electronic Progress Report Number 135.

DTIC Science & Technology

1993-06-01

78 @ 1.12 Ultrashort Pulse Generation in Solid State Lasers ...generation the use of intracavity self-phase-modulation and of ultrashort laser pulses is essential for studies of negative group velocity dispersion... pulses . Our studies focus on exploiting mode locked solid state lasers . While the dominant the short pulse durations and high peak intensity of effect of