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Sample records for infrared laser excitation

  1. Mode-selective phonon excitation in gallium nitride using mid-infrared free-electron laser

    NASA Astrophysics Data System (ADS)

    Kagaya, Muneyuki; Yoshida, Kyohei; Zen, Heishun; Hachiya, Kan; Sagawa, Takashi; Ohgaki, Hideaki

    2017-02-01

    The single-phonon mode was selectively excited in a solid-state sample. A mid-infrared free-electron laser, which was tuned to the target phonon mode, was irradiated onto a crystal cooled to a cryogenic temperature, where modes other than the intended excitation were suppressed. An A 1(LO) vibrational mode excitation on GaN(0001) face was demonstrated. Anti-Stokes Raman scattering was used to observe the excited vibrational mode, and the appearance and disappearance of the scattering band at the target wavenumber were confirmed to correspond to on and off switching of the pump free-electron laser and were fixed to the sample vibrational mode. The sum-frequency generation signals of the pump and probe lasers overlapped the Raman signals and followed the wavenumber shift of the pump laser.

  2. Far-infrared laser magnetic resonance of vibrationally excited CD2

    NASA Technical Reports Server (NTRS)

    Evenson, K. M.; Sears, T. J.; Mckellar, A. R. W.

    1984-01-01

    The detection of 13 rotational transitions in the first excited bending state (010) of CD2 using the technique of far-infrared laser magnetic resonance spectroscopy is reported. Molecular parameters for this state are determined from these new data together with existing infrared observations of the v(2) band. Additional information on the ground vibrational state (000) is also provided by the observation of a new rotational transition, and this is combined with existing data to provide a refined set of molecular parameters for the CD2 ground state. One spectrum has been observed that is assigned as a rotational transition within the first excited symmetric stretching state (100) of CD2. These data will be of use in refining the structure and the potential function of the methylene radical.

  3. Comparative study on atomic and molecular Rydberg-state excitation in strong infrared laser fields

    NASA Astrophysics Data System (ADS)

    Lv, Hang; Zuo, Wanlong; Zhao, Lei; Xu, Haifeng; Jin, Mingxing; Ding, Dajun; Hu, Shilin; Chen, Jing

    2016-03-01

    Rydberg-state excitation of atoms in strong infrared laser fields provides a new complementary aspect of the perspective of atom-strong field interactions. In this article, we perform an experimental and theoretical study on the corresponding process of diatomic molecules, N2 and O2. We show that neutral molecules can also survive strong 800-nm laser fields in high Rydberg states, while their behavior is remarkably different in comparison with their companion atoms, Ar and Xe. The Rydberg excitation of N2 generally behaves similarly to Ar, while that of O2 is more significantly suppressed than the ionization compared to Xe in a high intensity region, which can be understood in the frame of a semiclassical picture, together with their different structures of molecular orbitals. However, distinct quantum features in the Rydberg excitation processes that are apparently beyond the semiclassical picture have been identified, i.e., the less suppressed probability of O2 at low intensity and the oscillation behavior of the ratio between N2 and Ar, indicating that our understanding of the relevant physics is still far from complete.

  4. Laser action in chromium-activated forsterite for near infrared excitation

    NASA Technical Reports Server (NTRS)

    Petricevic, V.; Gayen, S. K.; Alfano, R. R.

    1988-01-01

    This paper reports on laser action in chromium-doped forsterite (Cr:Mg2SiO4) for 1064-nm excitation of the crystal's double-hump absorption band spanning the 850-1200-nm wavelength range. The cavity arrangement used for obtaining laser action in Cr:Mg2SiO2 was similar to that described by Petricevic et al. (1988). The fundamental and second harmonic emissions from a Q-switched Nd:YAG laser operating at a 10-Hz repetition rate were used for excitation of the NIR and visible bands, respectively. Pulsed laser action was readily observed for both the 1064-nm and 532-nm pumping at or above the respective thresholds. The laser parameters of the 532-nm and 1064-nm excitations were similar, indicating that the IR band is responsible for laser action for both excitations.

  5. Laser induced white emission generated by infrared excitation from Eu3+:Sr2CeO4 nanocrystals

    NASA Astrophysics Data System (ADS)

    Stefanski, M.; Lukaszewicz, M.; Hreniak, D.; Strek, W.

    2017-03-01

    The laser induced white emission (LIWE) was observed from Eu3+:Sr2CeO4 nanocrystals. The samples were obtained in form of powders by the modified sol-gel route. The structure and morphology of the phosphors were investigated by powder X-ray diffraction and transmission electron microscope techniques. The intense LIWE occurred under reduced pressure and focused beam of near infrared laser excitation. The power and pressure dependencies exhibit evident threshold character typical for the avalanche effect. The photoconductivity of the Eu3+:Sr2CeO4 nanocrystals measured as a function of different powers of excitation source was analyzed.

  6. 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.

  7. 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.

  8. Selective excitation of photosystems in chloroplasts inside plant leaves observed by near-infrared laser-based fluorescence spectral microscopy.

    PubMed

    Hasegawa, Makoto; Shiina, Takashi; Terazima, Masahide; Kumazaki, Shigeichi

    2010-02-01

    In this study, we produced selective images of photosystems in plant chloroplasts in situ. We used a spectroimaging microscope, equipped with a near-infrared (NIR) laser that provided light at wavelengths mainly between 800 and 830 nm, to analyze chlorophyll autofluorescence spectra and images from chloroplasts in leaves of Zea mays at room temperature. Femtosecond laser excitation of chloroplasts in mesophyll cells revealed a spectral shape that was attributable to PSII and its antenna in the centers of grana spots. We found that a continuous wave emitted by the NIR laser at a wavelength as long as 820 nm induced chlorophyll autofluorescence with a high contribution from PSI through a one-photon absorption mechanism. A spectral shape attributable to PSI and its antenna was thus obtained using continuous wave laser excitation of chloroplasts in bundle sheath cells. These highly pure spectra of photosystems were utilized for spectral decomposition at every intrachloroplast space to show distributions of PSI and PSII and their associated antenna. A new methodology using an NIR laser to detect the PSI/PSII ratio in single chloroplasts in leaves at room temperature is described.

  9. Mid-infrared laser-driven broadband water-window supercontinuum generation from pre-excited medium.

    PubMed

    Li, Yang; Hong, Weiyi; Zhang, Qingbin; Wang, Shaoyi; Lu, Peixiang

    2011-11-21

    We theoretically investigate the broadband water-window supercontinuum generation from pre-excited medium with a mid-infrared pulse. We find that the wavelength scaling of the harmonic yield from near-visible (0.8 μm) to mid-infrared (1.8 μm) in single-atom level is λ(-2.7). Using an intense phase-stabilized few-cycle 1.6 μm laser pulse, a broadband water window supercontinuum with bandwidth of approximately 140 eV is obtained. We also investigate the macroscopic effects and find that large initial population of the excited state leads to the high-density of free electrons, which shift the carrier-envelop phase of the driving pulse and further diminish the water-window supercontinuum generation. The highly-ionized medium also results in poor temporal and spatial properties of the attosecond pulse. Instead, small initial population of the excited state can produce well phase-matched xuv supercontinuum in water-window region and an 100-as pulse with central wavelength of 2.8 nm and pulse energy of 0.15 nJ can be filtered out.

  10. Optical Emission Studies of Copper Plasma Induced Using Infrared Transversely Excited Atmospheric (IR TEA) Carbon Dioxide Laser Pulses.

    PubMed

    Momcilovic, Milos; Kuzmanovic, Miroslav; Rankovic, Dragan; Ciganovic, Jovan; Stoiljkovic, Milovan; Savovic, Jelena; Trtica, Milan

    2015-04-01

    Spatially resolved, time-integrated optical emission spectroscopy was applied for investigation of copper plasma produced by a nanosecond infrared (IR) transversely excited atmospheric (TEA) CO2 laser, operating at 10.6 μm. The effect of surrounding air pressure, in the pressure range 0.1 to 1013 mbar, on plasma formation and its characteristics was investigated. A linear dependence of intensity threshold for plasma formation on logarithm of air pressure was found. Lowering of the air pressure reduces the extent of gas breakdown, enabling better laser-target coupling and thus increases ablation. Optimum air pressure for target plasma formation was 0.1 mbar. Under that pressure, the induced plasma consisted of two clearly distinguished and spatially separated regions. The maximum intensity of emission, with sharp and well-resolved spectral lines and negligibly low background emission, was obtained from a plasma zone 8 mm from the target surface. The estimated excitation temperature in this zone was around 7000 K. The favorable signal to background ratio obtained in this plasma region indicates possible analytical application of TEA CO2 laser produced copper plasma. Detection limits of trace elements present in the Cu sample were on the order of 10 ppm (parts per million). Time-resolved measurements of spatially selected plasma zones were used to find a correlation between the observed spatial position and time delay.

  11. Development of infrared sensors using energy transfer/energy upconversion processes: Study of laser excited fluorescence in rare Earth ion doped crystals

    NASA Technical Reports Server (NTRS)

    Nash-Stevenson, S. K.; Reddy, B. R.; Venkateswarlu, P.

    1994-01-01

    A summary is presented of the spectroscopic study of three systems: LaF3:Ho(3+), LaF3:Er(3+) and CaF2:Nd(3+). When the D levels of Ho(3+) in LaF3 were resonantly excited with a laser beam of 640 nm, upconverted emissions were detected from J (416 nm), F (485 nm), and E (546 nm) levels. Energy upconverted emissions were also observed from F and E levels of Ho(3+) when the material was excited with an 800 nm near infrared laser. When the D levels of Er(3+) in LaF3 were resonantly excited with a laser beam of 637 nm, upconverted emissions were detected from the E (540 nm) and P (320, 400, and 468 nm) levels. Energy upconverted emissions were also observed from F, E, and D levels of Er(3+) when the material was resonantly excited with an 804 nm near infrared laser. When the D levels of Nd(3+) in CaF2 were resonantly excited with a laser beam of 577 nm, upconverted emissions were detected from the L (360 and 382 nm), K (418 nm), and I (432 nm) levels. Very weak upconverted emissions were detected when this system was irradiated with a near infrared laser. The numbers in parentheses are the wavelengths of the emissions.

  12. Single photon infrared emission spectroscopy: a study of IR emission from UV laser excited PAHs between 3 and 15 micrometers

    NASA Technical Reports Server (NTRS)

    Cook, D. J.; Schlemmer, S.; Balucani, N.; Wagner, D. R.; Harrison, J. A.; Steiner, B.; Saykally, R. J.

    1998-01-01

    Single-photon infrared emission spectroscopy (SPIRES) has been used to measure emission spectra from polycyclic aromatic hydrocarbons (PAHs). A supersonic free-jet expansion has been used to provide emission spectra of rotationally cold and vibrationally excited naphthalene and benzene. Under these conditions, the observed width of the 3.3-micrometers (C-H stretch) band resembles the bandwidths observed in experiments in which emission is observed from naphthalene with higher rotational energy. To obtain complete coverage of IR wavelengths relevant to the unidentified infrared bands (UIRs), UV laser-induced desorption was used to generate gas-phase highly excited PAHs. Lorentzian band shapes were convoluted with the monochromator-slit function in order to determine the widths of PAH emission bands under astrophysically relevant conditions. Bandwidths were also extracted from bands consisting of multiple normal modes blended together. These parameters are grouped according to the functional groups mostly involved in the vibration, and mean bandwidths are obtained. These bandwidths are larger than the widths of the corresponding UIR bands. However, when the comparison is limited to the largest PAHs studied, the bandwidths are slightly smaller than the corresponding UIR bands. These parameters can be used to model emission spectra from PAH cations and cations of larger PAHs, which are better candidate carriers of the UIRs.

  13. Observation of two-photon photoemission from cesium telluride photocathodes excited by a near-infrared laser

    NASA Astrophysics Data System (ADS)

    Panuganti, H.; Piot, P.

    2017-02-01

    We explore the nonlinear photoemission in cesium telluride (Cs2Te) photocathodes where an ultrashort (˜100 fs full width at half max) 800-nm infrared laser is used as the drive-laser in lieu of the typical ˜266-nm ultraviolet laser. An important figure of merit for photocathodes, the quantum efficiency, we define here for nonlinear photoemission processes in order to compare with linear photoemission. The charge against drive-laser (infrared) energy is studied for different laser energy and intensity values and cross-compared with previously performed similar studies on copper [P. Musumeci et al., Phys. Rev. Lett. 104, 084801 (2010)], a metallic photocathode. We particularly observe two-photon photoemission in Cs2Te using the infrared laser in contrast to the anticipated three-photon process as observed for metallic photocathodes.

  14. Infrared Lasers in Chemistry.

    ERIC Educational Resources Information Center

    John, Phillip

    1982-01-01

    Selected infrared laser chemistry topics are discussed including carbon dioxide lasers, infrared quanta and molecules, laser-induced chemistry, structural isomerization (laser purification, sensitized reactions, and dielectric breakdown), and fundamental principles of laser isotope separation, focusing on uranium isotope separation. (JN)

  15. Experimental demonstration of mode-selective phonon excitation of 6H-SiC by a mid-infrared laser with anti-Stokes Raman scattering spectroscopy

    SciTech Connect

    Yoshida, Kyohei; Hachiya, Kan; Okumura, Kensuke; Mishima, Kenta; Inukai, Motoharu; Torgasin, Konstantin; Omer, Mohamed; Sonobe, Taro; Zen, Heishun; Negm, Hani; Kii, Toshiteru; Masuda, Kai; Ohgaki, Hideaki

    2013-10-28

    Mode-selective phonon excitation by a mid-infrared laser (MIR-FEL) is demonstrated via anti-Stokes Raman scattering measurements of 6H-silicon carbide (SiC). Irradiation of SiC with MIR-FEL and a Nd-YAG laser at 14 K produced a peak where the Raman shift corresponds to a photon energy of 119 meV (10.4 μm). This phenomenon is induced by mode-selective phonon excitation through the irradiation of MIR-FEL, whose photon energy corresponds to the photon-absorption of a particular phonon mode.

  16. Efficient blue upconversion emission due to confined radiative energy transfer in Tm 3+-Nd 3+ co-doped Ta 2O 5 waveguides under infrared-laser excitation

    NASA Astrophysics Data System (ADS)

    Lahoz, F.; Shepherd, D. P.; Wilkinson, J. S.; Hassan, M. A.

    2008-07-01

    Intense blue upconversion emission at 480 nm has been obtained at room temperature in Tm 3+-Nd 3+ co-doped Ta 2O 5 channel waveguides fabricated on a Si substrate, when the sample is excited with an infrared laser at 793 nm. The upconversion mechanism is based on the radiative relaxation of the Nd 3+ ions ( 4F 3/2 → 4I 11/2) at about 1064 nm followed by the absorption of the emitted photons by Tm 3+ ions in the 3H 4 excited state. A coefficient of energy transfer rate as high as 3 × 10 -16 cm 3/s has been deduced using a rate equation analysis, which is the highest reported for Tm-Nd co-doped systems. The confinement of the 1064 nm emitted radiation in the waveguide structure is the main reason of the high energy transfer probability between Nd 3+ and Tm 3+ ions.

  17. Infrared diode laser spectroscopy

    NASA Astrophysics Data System (ADS)

    Civiš, S.; Cihelka, J.; Matulková, I.

    2010-12-01

    Three types of lasers (double-heterostructure 66 K InAsSb/InAsSbP laser diode, room temperature, multi quantum wells with distributed feedback (MQW with DFB) (GaInAsSb/AlGaAsSb based) diode laser and vertical cavity surface emitting lasers (VCSELs) (GaSb based) have been characterized using Fourier transform emission spectroscopy and compared. The photoacoustic technique was employed to determine the detection limit of formaldehyde (less than 1 ppmV) for the strongest absorption line of the v3 + v5 band in the emission region of the GaInAsSb/AlGaAsSb diode laser. The detection limit (less than 10 ppbV) of formaldehyde was achieved in the 2820 cm-1 spectral range in case of InAsSb/InAsSbP laser (fundamental bands of v1, v5). Laser sensitive detection (laser absorption together with high resolution Fourier transform infrared technique including direct laser linewidth measurement, infrared photoacoustic detection of neutral molecules (methane, form-aldehyde) is discussed. Additionally, very sensitive laser absorption techniques of such velocity modulation are discussed for case of laser application in laboratory research of molecular ions. Such sensitive techniques (originally developed for lasers) contributed very much in identifying laboratory microwave spectra of a series of anions (C6H-, C4H-, C2H-, CN-) and their discovery in the interstellar space (C6H-, C4H-).

  18. Near infrared lasers in flow cytometry.

    PubMed

    Telford, William G

    2015-07-01

    Technology development in flow cytometry has closely tracked laser technology, the light source that flow cytometers almost exclusively use to excite fluorescent probes. The original flow cytometers from the 1970s and 1980s used large water-cooled lasers to produce only one or two laser lines at a time. Modern cytometers can take advantage of the revolution in solid state laser technology to use almost any laser wavelength ranging from the ultraviolet to the near infrared. Commercial cytometers can now be equipped with many small solid state lasers, providing almost any wavelength needed for cellular analysis. Flow cytometers are now equipped to analyze 20 or more fluorescent probes simultaneously, requiring multiple laser wavelengths. Instrument developers are now trying to increase this number by designing fluorescent probes that can be excited by laser wavelength at the "edges" of the visible light range, in the near ultraviolet and near-infrared region. A variety of fluorescent probes have been developed that excite with violet and long wavelength ultraviolet light; however, the near-infrared range (660-800 nm) has yet seen only exploitation in flow cytometry. Fortunately, near-infrared laser diodes and other solid state laser technologies appropriate for flow cytometry have been in existence for some time, and can be readily incorporated into flow cytometers to accelerate fluorescent probe development. The near infrared region represents one of the last "frontiers" to maximize the number of fluorescent probes that can be analyzed by flow cytometry. In addition, near infrared fluorescent probes used in biomedical tracking and imaging could also be employed for flow cytometry with the correct laser wavelengths. This review describes the available technology, including lasers, fluorescent probes and detector technology optimal for near infrared signal detection.

  19. Fine tunable red-green upconversion luminescence from glass ceramic containing 5%Er{sup 3+}:NaYF{sub 4} nanocrystals under excitation of two near infrared femtosecond lasers

    SciTech Connect

    Shang, Xiaoying; Cheng, Wenjing; Zhou, Kan; Ma, Jing; Feng, Donghai; Zhang, Shian; Sun, Zhenrong; Jia, Tianqing; Chen, Ping; Qiu, Jianrong

    2014-08-14

    In this paper, we report fine tunable red-green upconversion luminescence of glass ceramic containing 5%Er{sup 3+}: NaYF{sub 4} nanocrystals excited simultaneously by two near infrared femtosecond lasers. When the glass ceramic was irradiated by 800 nm femtosecond laser, weak red emission centered at 670 nm was detected. Bright red light was observed when the fs laser wavelength was tuned to 1490 nm. However, when excited by the two fs lasers simultaneously, the sample emitted bright green light centered at 550 nm, while the red light kept the same intensity. The dependences of the red and the green light intensities on the two pump lasers are much different, which enables us to manipulate the color emission by adjusting the two pump laser intensities, respectively. We present a theoretical model of Er{sup 3+} ions interacting with two fs laser fields, and explain well the experimental results.

  20. Infrared laser bone ablation

    SciTech Connect

    Nuss, R.C.; Fabian, R.L.; Sarkar, R.; Puliafito, C.A.

    1988-01-01

    The bone ablation characteristics of five infrared lasers, including three pulsed lasers (Nd:YAG, lambda = 1064 micron; Hol:YSGG, lambda = 2.10 micron; and Erb:YAG, lambda = 2.94 micron) and two continuous-wave lasers (Nd:YAG, lambda = 1.064 micron; and CO/sub 2/, lambda = 10.6 micron), were studied. All laser ablations were performed in vitro, using moist, freshly dissected calvarium of guinea pig skulls. Quantitative etch rates of the three pulsed lasers were calculated. Light microscopy of histologic sections of ablated bone revealed a zone of tissue damage of 10 to 15 micron adjacent to the lesion edge in the case of the pulsed Nd:YAG and the Erb:YAG lasers, from 20 to 90 micron zone of tissue damage for bone ablated by the Hol:YSGG laser, and 60 to 135 micron zone of tissue damage in the case of the two continuous-wave lasers. Possible mechanisms of bone ablation and tissue damage are discussed.

  1. Laser mass spectrometry at high vibrational excitation density

    NASA Astrophysics Data System (ADS)

    Haglund, R. F., Jr.; Baltz-Knorr, M.; Ermer, D. R.; Papantonakis, M. R.; Schriver, K. E.

    2003-06-01

    We describe a novel approach to infrared matrix-assisted laser desorption-ionization mass spectrometry using a tunable, picosecond pulse laser to selectively excite specific modes of a solid, thereby creating a high local density of vibrational quanta. The concept is based on recent results from our experiments employing a free-electron laser to explore 'matrix-less' mass spectrometry in which an infrared chromophore intrinsic to the sample, rather than an exogenous matrix, is excited by the laser. Examples from both environmental mass spectrometry and a proteomics-driven research project are presented, showing how the principle of selective vibrational excitation can be used to make possible novel and useful ion generation protocols. We conclude with an analysis of possible mechanisms for the phenomena of infrared desorption, ablation and ionization using very short laser pulses. Prospects for achieving similar results with more conventional laser sources are discussed.

  2. Fission fragment excited laser system

    DOEpatents

    McArthur, David A.; Tollefsrud, Philip B.

    1976-01-01

    A laser system and method for exciting lasing action in a molecular gas lasing medium which includes cooling the lasing medium to a temperature below about 150 K and injecting fission fragments through the lasing medium so as to preferentially excite low lying vibrational levels of the medium and to cause population inversions therein. The cooled gas lasing medium should have a mass areal density of about 5 .times. 10.sup.-.sup.3 grams/square centimeter, relaxation times of greater than 50 microseconds, and a broad range of excitable vibrational levels which are excitable by molecular collisions.

  3. Ultraviolet laser excitation source

    NASA Technical Reports Server (NTRS)

    Lee, J. H.; Mcfarland, D. R.; Hohl, F.

    1980-01-01

    A new intense ultraviolet light source has been developed from an array of hypocycloidal pinch (HCP) devices. The basic unit of the array is constructed with three disk electrodes and is capable of producing dense plasmas at temperatures up to 10,000,000 K. Very high input power levels to the array are possible without significantly shortening its useful life, in strong contrast with conventional xenon flashlamps. The new light source, when operated with Ar and Xe gas mixtures at high pressures (approximately 5 x 10 to the 4th Pa), produced a light output of over 100 MW in the near-UV spectral range and successfully pumped an iodine photodissociation laser at 1.315 microns. A xenon recombination laser at 2.027 microns was also pumped in the HCP array.

  4. Infrared-Laser Excitation of the Internal Vibrational Mode of a Diatomic Molecule Adsorbed on a Metal Surface.

    DTIC Science & Technology

    1986-11-01

    Excitation of the Internal Vibrational Mode of a Diatomic Molecule Adsorbed on a Metal Surface m by ’ Andre Peremans, Jacques Darville , Jean-Marie...Andre Peremans, Jacques Darville , Jean-Marie Gilles and Thomas F. George 13. TYPE OF REPORT 13b. TIME COVERED 14. DATE OF REPORT (Yr. Mo.. Dayl As...ON A METAL SURFACE h Andr& Peremans , Jacques Darville and Jean-Marie Gilles _ _ _ _ Laboratoire de Spectroscopie Mol6culaire de Surface Accesnion

  5. Influence of excitation and deexcitation processes on the dynamics of laser-excited argon clusters

    NASA Astrophysics Data System (ADS)

    Moll, M.; Schlanges, M.; Bornath, Th.; Krainov, V. P.

    2015-03-01

    The excitation of atomic clusters by intense infrared laser pulses leads to the creation of highly charged ions and to the emission of energetic photons. These phenomena, which follow from ionization processes occurring in the cluster, depend significantly on the population of ground states and excited states in the laser-produced nanoplasma. This makes it necessary to account for collisional excitation and deexcitation processes. We investigate the interaction of femtosecond laser pulses with argon clusters by means of a nanoplasma model. Considering laser excitation with single and double pulses, we analyze the role of excitation and deexcitation processes in detail and calculate the yield of highly charged ions and of energetic photons in different wavelength regimes.

  6. REVIEWS OF TOPICAL PROBLEMS: Gas lasers with solar excitation

    NASA Astrophysics Data System (ADS)

    Gordiets, B. F.; Panchenko, Vladislav Ya

    1986-07-01

    CONTENTS 1. Introduction 703 2. General requirements for laser media using solar excitation 704 3. Lasers with direct excitation by solar light 705 3.1. Basic characteristics of laser media. 3.2. Photodissociation Br2-CO2 lasers. 3.3. Interhalogen molecule lasers. 3.4. Iodine lasers. 3.5. Alkali metal vapor lasers. 4. Lasers with thermal conversion of solar pumping 709 4.1. General considerations. 4.2. CO2 laser with excitation in a black body cavity and with gas flow. 4.3. cw CO2 laser without gas flow. 5. Space laser media with solar excitation 713 5.1. Population inversion of molecular levels in the outer atmosphere of the Earth. 5.2. Laser effect in the atmospheres of Venus and Mars. 5.3. Terrestrial experimental technique for observing infrared emission in the atmospheres of planets. 5.4. Designs for laser systems in the atmospheres of Venus and Mars. 6. Conclusions 717 References 717

  7. Near infrared laser ocular bioeffects

    SciTech Connect

    Lund, D.J.; Beatrice, E.S.

    1989-05-01

    Thresholds for laser chorioretinal injury in the red end of the visible spectrum and the near-infrared (IR-A) spectral regions are presented. An unpredicted wavelength dependence of the injury threshold for single Q-switched pulses is demonstrated. Four lasers were used to determine thresholds at 40 wavelengths between 532 nm and 1064 nm: a ruby laser, a neodymium:YAG-pumped dye laser, an erbium:YLF laser and an alexandrite laser. Despite many careful and repeated efforts to determine a cause for the variation due to possible variations in the lasers or other aspects of the experimental technique and due to biological absorption properties of the eye, there is no complete or obvious explanation for the significant variations of threshold with small changes in wavelength. The implications of these findings for laser safety standards are presented.

  8. Direct excitation of microwave-spin dressed states using a laser-excited resonance Raman interaction

    NASA Astrophysics Data System (ADS)

    Shahriar, M. S.; Hemmer, P. R.

    1990-10-01

    We have used a laser-induced resonance Raman transition between the ground-state hyperfine sublevels in a sodium atomic beam to excite individual dressed states of the microwave-spin hyperfine transition. In addition, we have used the microwave interaction to excite the Raman trapped state. Extension of this technique to mm waves or to the far infrared may lead to applications such as mm-wave-beam steering and holographic image conversion.

  9. Laser Excited Fluorescence Studies Of Black Liquor

    NASA Astrophysics Data System (ADS)

    Horvath, J. J.; Semerjian, H. G.

    1986-10-01

    Laser excited fluorescence of black liquor was investigated as a possible monitoring technique for pulping processes. A nitrogen pumped dye laser was used to examine the fluorescence spectrum of black liquor solutions. Various excitation wavelengths were used between 290 and 403 nm. Black liquor fluorescence spectra were found to vary with both excitation wavelength and black liquor concentration. Laser excited fluorescence was found to be a sensitive technique for measurement of black liquor with good detection limits and linear response over a large dynamic range.

  10. Tunable Infrared Semiconductor Lasers

    DTIC Science & Technology

    2013-12-20

    is a thulium fiber laser that has output of 20Watts at 1.908 µm with a collimated output beam diameter of about 5 mm. With a cylindrical lens, a...the device onto a copper heat sink and then to the cold finger of liquid nitrogen Dewar. In characterization, a thulium fiber laser at 1.908 nm

  11. Optically pumped far-infrared lasers

    NASA Astrophysics Data System (ADS)

    Button, K. J.; Inguscio, M.; Strumia, F.

    A handbook of far-infrared (submillimeter) laser technology is presented. Among the specific laser systems described are: 12CH3F and 13CH3F lasers; submillimeter lasers in dueuterated methyl fluoride CD3F; and far-infrared laser lines obtained by optical pumping. Consideration is given to other far-infrared laser media, including: methyl iodide; CH3OH; D2O; and fluorocarbon 12, CF2C12. Additional topics discussed include: an optically pumped PH3 laser operating in the region 83-223 microns; an optically pumped formic acid laser; and optically pumped infrared lasing in propyne.

  12. Subcycle dynamics of high-order-harmonic generation of He atoms excited by attosecond pulses and driven by near-infrared laser fields: A self-interaction-free time-dependent density-functional-theory approach

    NASA Astrophysics Data System (ADS)

    Heslar, John; Telnov, Dmitry A.; Chu, Shih-I.

    2014-05-01

    In the framework of the self-interaction-free time-dependent density-functional theory, we have performed three-dimensional (3D) ab initio calculations of He atoms in near-infrared (NIR) laser fields subject to excitation by a single extreme ultraviolet (XUV) attosecond pulse (SAP). We have explored the dynamical behavior of the subcycle high harmonic generation (HHG) for transitions from the excited states to the ground state and found oscillation structures with respect to the time delay between the SAP and NIR fields. The oscillatory pattern in the photon emission spectra has a period of ˜1.3 fs which is half of the NIR laser optical cycle, similar to that recently measured in the experiments on transient absorption of He [M. Chini et al., Sci. Rep. 3, 1105 (2013), 10.1038/srep01105]. We present the photon emission spectra from 1s2p, 1s3p, 1s4p, 1s5p, and 1s6p excited states as functions of the time delay. We explore the subcycle Stark shift phenomenon in NIR fields and its influence on the photon emission process. Our analysis reveals several interesting features of the subcycle HHG dynamics and we identify the mechanisms responsible for the observed peak splitting in the photon emission spectra.

  13. Sub-Cycle Dynamics of High Harmonic Generation of He Atoms Excited by Attosecond Pulses and Driven by Near-Infrared Laser Fields: A Self-Interaction-Free TDDFT Theoretical Approach

    NASA Astrophysics Data System (ADS)

    Heslar, John; Telnov, Dmitry A.; Chu, Shih-I.

    2014-05-01

    In the framework of the self-interaction-free time-dependent density functional theory, we have performed 3D ab initio calculations of He atoms in near-infrared (NIR) laser fields subject to excitation by a single extreme ultraviolet (XUV) attosecond pulse (SAP). We have explored the novel dynamical behavior of the sub-cycle high harmonic generation (HHG) for transitions from the excited states to the ground state and found oscillation structures with respect to the time delay between the SAP and NIR fields. The oscillatory pattern in the photon emission spectra has a period of 1.3 fs which is half of the NIR laser optical cycle, similar to that recently measured in the experiments on transient absorption of He. We present the photon emission spectra from 1s2p, 1s3p, 1s4p, 1s5p, and 1s6p excited states as functions of the time delay. We explore the sub-cycle Stark shift phenomenon in NIR fields and its influence on the photon emission process. Our analysis reveals several new features of the sub-cycle HHG dynamics and we identify the mechanisms responsible for the observed peak splitting in the photon emission spectra. This work was partially supported by DOE.

  14. Optical and infrared lasers

    NASA Technical Reports Server (NTRS)

    Javan, A.

    1978-01-01

    Quantum mechanical predictions for the gain of an optically pumped CW FIR laser are presented for cases in which one or both of the pump and FIR transitions are pressure or Doppler broadened. The results are compared to those based on the rate equation model. Some of the quantum mechanical predictions are verified in CH3OH.

  15. Mixing gasdynamic laser with nonequilibrium arc excitation

    NASA Astrophysics Data System (ADS)

    Antonov, G. G.; Kovshechnikov, V. B.; Rutberg, F. G.

    2016-05-01

    A mixing gasdynamic laser with nonuniform arc excitation is investigated using a model setup. Tentative analysis of the results indicates the appropriateness of using plasmatrons to improve the efficiency of mixing gasdynamic lasers by making carbon dioxide molecules vibrationally more nonuniform. In addition, a plasmatron serves as a preionization source both for a fast-flow gas-discharge laser and for a gasdynamic laser with combined pumping.

  16. [Two-step exposure of biological objects to infrared laser and microwave radiation].

    PubMed

    Kol'tsov, Iu V; Korolev, V N; Kusakin, S A

    1999-01-01

    The effect of two-step exposure of bacterial objects to infrared laser and microwave pulse radiations was studied. The effect is determined by the time interval between two excitation steps and pulse duration. It was shown that the biologically active dose of microwave radiation is much lower than that of infrared laser radiation; however, laser radiation induces a stronger cellular response. It was found that microwaves enhance the efficiency of infrared laser radiation.

  17. Advanced infrared laser modulator development

    NASA Technical Reports Server (NTRS)

    Cheo, P. K.; Wagner, R.; Gilden, M.

    1984-01-01

    A parametric study was conducted to develop an electrooptic waveguide modulator for generating continuous tunable sideband power from an infrared CO2 laser. Parameters included were the waveguide configurations, microstrip dimensions device impedance, and effective dielectric constants. An optimum infrared laser modulator was established and was fabricated. This modulator represents the state-of-the-art integrated optical device, which has a three-dimensional topology to accommodate three lambda/4 step transformers for microwave impedance matching at both the input and output terminals. A flat frequency response of the device over 20 HGz or = 3 dB) was achieved. Maximum single sideband to carrier power greater than 1.2% for 20 W microwave input power at optical carrier wavelength of 10.6 microns was obtained.

  18. Laser Excited Fluorescence For Forensic Diagnostics

    NASA Astrophysics Data System (ADS)

    McKinney, Robert E.

    1986-07-01

    The application of laser excited fluorescence to the detection and identification of latent fingerprints was first accomplished ten years ago. The development of the technology has progressed rapidly with the introduction of commercial equipment by several manufacturers. Systems based on Argon-ion, Copper-vapor, and frequency-doubled Nd:YAG lasers are compared. The theoretical basis of detection by fluorescence is discussed along with the more useful techniques of dye staining. Other applications of the laser excited fluorescence in forensic investigation include gunshot residue analysis, serology, collection of trace evidence, and document examination.

  19. Using Guide Wavelengths to Assess Far-Infrared Laser Emissions

    NASA Astrophysics Data System (ADS)

    DeShano, B.; Olivier, K.; Cain, B.; Zink, L. R.; Jackson, M.

    2014-09-01

    An optically pumped molecular laser system with a transverse excitation scheme has been used to observe 77 guide wavelengths associated with the modes of an oversized waveguide laser resonator. These guide wavelengths, spanning from 102.6 to 990.6 μm, were generated by a variety of lasing media, including methanol along with several symmetric- and asymmetric-top molecules. The guide wavelengths displayed several consistent characteristics when compared with their respective fundamental laser emissions: their wavelengths were about 0.47 % larger and their relative powers were at least a factor of ten weaker. The properties of these guide wavelengths were used to assess frequency and wavelength measurements associated with known far-infrared laser emissions. For several of these laser emissions, this prompted a reinvestigation and subsequent revision of their measured values. Five far-infrared laser frequencies were also measured for the first time.

  20. Using Guide Wavelengths to Assess Far-Infrared Laser Emissions

    NASA Astrophysics Data System (ADS)

    DeShano, B.; Olivier, K.; Cain, B.; Zink, L. R.; Jackson, M.

    2015-01-01

    An optically pumped molecular laser system with a transverse excitation scheme has been used to observe 77 guide wavelengths associated with the modes of an oversized waveguide laser resonator. These guide wavelengths, spanning from 102.6 to 990.6 μm, were generated by a variety of lasing media, including methanol along with several symmetric- and asymmetric-top molecules. The guide wavelengths displayed several consistent characteristics when compared with their respective fundamental laser emissions: their wavelengths were about 0.47 % larger and their relative powers were at least a factor of ten weaker. The properties of these guide wavelengths were used to assess frequency and wavelength measurements associated with known far-infrared laser emissions. For several of these laser emissions, this prompted a reinvestigation and subsequent revision of their measured values. Five far-infrared laser frequencies were also measured for the first time.

  1. Parametric infrared tunable laser system

    NASA Technical Reports Server (NTRS)

    Garbuny, M.; Henningsen, T.; Sutter, J. R.

    1980-01-01

    A parametric tunable infrared laser system was built to serve as transmitter for the remote detection and density measurement of pollutant, poisonous, or trace gases in the atmosphere. The system operates with a YAG:Nd laser oscillator amplifier chain which pumps a parametric tunable frequency converter. The completed system produced pulse energies of up to 30 mJ. The output is tunable from 1.5 to 3.6 micrometers at linewidths of 0.2-0.5 /cm (FWHM), although the limits of the tuning range and the narrower line crystals presently in the parametric converter by samples of the higher quality already demonstrated is expected to improve the system performance further.

  2. Subcycle dynamics of high harmonic generation in valence-shell and virtual states of Ar atoms excited by attosecond pulses and driven by near-infrared laser fields: A self-interaction-free TDDFT theoretical approach

    NASA Astrophysics Data System (ADS)

    Heslar, John; Telnov, Dmitry A.; Chu, Shih-I.

    2015-05-01

    In the framework of the self-interaction-free time-dependent density functional theory (TDDFT), we have performed an ab initio all-electron study of subcycle structure, dynamics, and spectra of high harmonic generation (HHG) processes of Ar atoms in the presence of extreme ultraviolet (XUV) attosecond pulses and near-infrared (NIR) laser fields. The TDDFT equations are solved accurately and efficiently via the time-dependent generalized pseudospectral (TDGPS) method. We focus on the subcycle (with respect to NIR field) temporal behavior of the level shift of the excited energy levels and related dynamics of harmonic photon emission. We observe and identify the subcycle shifts in the harmonic emission spectrum as a function of the time delay between the XUV and NIR pulses. We present and analyze the harmonic emission spectra from 3snp0, 3p0ns, 3p1nd1,3p1np1, 3p0nd0, 3p0np0, and 3p0ns excited states and the 3p04p0-virtual state as functions of the time delay. In addition, we explore the subcycle a.c. Stark shift phenomenon in NIR fields and its influence on the harmonic emission process. Our analysis reveals several novel features of the subcycle HHG dynamics and spectra as well as temporal energy level shift. This work was partially supported by DOE.

  3. Laser-based excitation and diagnostics of planar fractures

    NASA Astrophysics Data System (ADS)

    Blum, T. E.; Van Wijk, K.; Snieder, R.; Willis, M. E.

    2011-12-01

    Faults are of interest not only to earth science, but also at different scales in the non-destructive testing (NDT) community. Remote sensing of faults is of interest to both communities, with the idea of inverting for the fracture properties in a non-invasive way. Alternatively, the wave field directly excited at the fracture is of interest to both communities because the waves thus radiated are equivalent to those emitted by acoustic emissions or micro-earthquakes. Much can be learned from recording of elastic waves excited at the the fracture. Based on technology developed for NDT, we use laser ultrasonics in the laboratory to excite and detect elastic waves, in order to determine the properties of fractures or faults in laboratory rock and synthetic samples. We show examples of wave propagation in a clear Poly(methyl methacrylate) cylinder. By focusing a high power infrared (IR) laser inside the cylinder we create a visible single disk-shaped fracture near the center of the sample. The laser generates a short pulse (~20 ns) of infrared light that is absorbed by the sample material at the focal point and is converted into heat. The sudden thermal expansion generates stress and forms a fracture parallel to the cylindrical axis. We excite elastic waves at the surface of the sample using the same high-power pulsed laser, but at a much lower energy setting, and with an unfocused beam. We measure the direct and scattered wave field from the fracture with a laser interferometer, and also excite the fracture directly with a fraction of the source laser energy impinging directly on the fracture. A comparison of the direct excitation and the elastic scattered wavefields, including studies of the tip diffractions from the fracture, shows strong agreement. The measured tip diffractions carry information about the stress concentration near the crack tips, which is crucial for understanding rupture processes. This novel laboratory technique allows us to measure the source

  4. The Berkeley tunable far infrared laser spectrometers

    NASA Technical Reports Server (NTRS)

    Blake, G. A.; Laughlin, K. B.; Cohen, R. C.; Busarow, K. L.; Gwo, D.-H.

    1991-01-01

    A detailed description is presented for a tunable far infrared laser spectrometer based on frequency mixing of an optically pumped molecular gas laser with tunable microwave radiation in a Schottky point contact diode. The system has been operated on over 30 laser lines in the range 10-100/cm and exhibits a maximum absorption sensitivity near one part in a million. Each laser line can be tuned by + or - 110 GHz with first-order sidebands.

  5. Mid-Infrared Fiber Lasers (Les fibres laser infrarouge moyen)

    DTIC Science & Technology

    2010-09-01

    à fibres sont intrinsèquement mieux adaptés à ces applications que les lasers à l’état solide conventionnels, offrant un confinement optique , une...Sep 2010 Mid-Infrared Fiber Lasers (Les fibres laser infrarouge moyen) Research and Technology Organisation (NATO) BP 25, F-92201 Neuilly-sur-Seine...SET-171)TP/370 www.rto.nato.int RTO MEETING PROCEEDINGS MP-SET-171 Mid-Infrared Fiber Lasers (Les fibres laser infrarouge moyen) Papers presented

  6. VIBRATIONALLY EXCITED HCN IN THE LUMINOUS INFRARED GALAXY NGC 4418

    SciTech Connect

    Sakamoto, Kazushi; Aalto, Susanne; Evans, Aaron S.; Wiedner, Martina C.; Wilner, David J.

    2010-12-20

    Infrared pumping and its effect on the excitation of HCN molecules can be important when using rotational lines of HCN to probe dense molecular gas in galaxy nuclei. We report the first extragalactic detection of (sub)millimeter rotational lines of vibrationally excited HCN, in the dust-enshrouded nucleus of the luminous infrared galaxy NGC 4418. We estimate the excitation temperature of T{sub vib} {approx} 230 K between the vibrational ground and excited (v{sub 2} = 1) states. This excitation is most likely due to infrared radiation. At this high vibrational temperature the path through the v{sub 2} = 1 state must have a strong impact on the rotational excitation in the vibrational ground level, although it may not be dominant for all rotational levels. Our observations also revealed nearly confusion-limited lines of CO, HCN, HCO{sup +}, H{sup 13}CN, HC{sup 15}N, CS, N{sub 2}H{sup +}, and HC{sub 3}N at {lambda} {approx} 1 mm. Their relative intensities may also be affected by the infrared pumping.

  7. Silver nanoparticle based surface enhanced Raman scattering spectroscopy of diabetic and normal rat pancreatic tissue under near-infrared laser excitation

    NASA Astrophysics Data System (ADS)

    Huang, H.; Shi, H.; Feng, S.; Lin, J.; Chen, W.; Huang, Z.; Li, Y.; Yu, Y.; Lin, D.; Xu, Q.; Chen, R.

    2013-04-01

    This paper presents the use of high spatial resolution silver nanoparticle based near-infrared surface enhanced Raman scattering (SERS) from rat pancreatic tissue to obtain biochrmical information about the tissue. A high quality SERS signal from a mixture of pancreatic tissues and silver nanoparticles can be obtained within 10 s using a Renishaw micro-Raman system. Prominent SERS bands of pancreatic tissue were assigned to known molecular vibrations, such as the vibrations of DNA bases, RNA bases, proteins and lipids. Different tissue structures of diabetic and normal rat pancreatic tissues have characteristic features in SERS spectra. This exploratory study demonstrated great potential for using SERS imaging to distinguish diabetic and normal pancreatic tissues on frozen sections without using dye labeling of functionalized binding sites.

  8. Site-Specific Dynamics of β-Sheet Peptides with (D) Pro-Gly Turns Probed by Laser-Excited Temperature-Jump Infrared Spectroscopy.

    PubMed

    Popp, Alexander; Scheerer, David; Chi, Heng; Keiderling, Timothy A; Hauser, Karin

    2016-05-04

    Turn residues and side-chain interactions play an important role for the folding of β-sheets. We investigated the conformational dynamics of a three-stranded β-sheet peptide ((D) P(D) P) and a two-stranded β-hairpin (WVYY-(D) P) by time-resolved temperature-jump (T-jump) infrared spectroscopy. Both peptide sequences contain (D) Pro-Gly residues that favor a tight β-turn. The three-stranded β-sheet (Ac-VFITS(D) PGKTYTEV(D) PGOKILQ-NH2 ) is stabilized by the turn sequences, whereas the β-hairpin (SWTVE(D) PGKYTYK-NH2 ) folding is assisted by both the turn sequence and hydrophobic cross-strand interactions. Relaxation times after the T-jump were monitored as a function of temperature and occur on a sub-microsecond time scale, (D) P(D) P being faster than WVYY-(D) P. The Xxx-(D) Pro tertiary amide provides a detectable IR band, allowing us to probe the dynamics site-specifically. The relative importance of the turn versus the intrastrand stability in β-sheet formation is discussed.

  9. Infrared Laser Therapy using IR absorption of biomolecules

    NASA Astrophysics Data System (ADS)

    Awazu, K.; Ishii, K.; Hazama, H.

    2011-02-01

    Since numerous characteristic absorption lines caused by molecular vibration exist in the mid-infrared (MIR) wavelength region, selective excitation or selective dissociation of molecules is possible by tuning the laser wavelength to the characteristic absorption lines of target molecules. By applying this feature to the medical fields, less-invasive treatment and non-destructive diagnosis with absorption spectroscopy are possible using tunable MIR lasers. A high-energy nanosecond pulsed MIR tunable laser was obtained with difference-frequency generation (DFG) between a Nd:YAG and a tunable Cr:forsterite lasers. The MIR-DFG laser was tunable in a wavelength range of 5.5-10 μm and generated a laser pulses with an energy of up to 1.4 mJ, a pulse width of 5 ns, and a pulse repetition rate of 10 Hz. Selective removal of atherosclerotic lesion was successfully demonstrated with the MIR-DFG laser tuned at a wavelength of 5.75 μm, which corresponds to the characteristic absorption of the ester bond in cholesterol esters in the atherosclerotic lesions. We have developed a non-destructive diagnostic probe with an attenuated total reflection (ATR) prism and two hollow optical fibres. An absorption spectrum of cholesterol was measured with the ATR probe by scanning the wavelength of the MIR-DFG laser, and the spectrum was in good agreement with that measured with a commercial Fourier transform infrared spectrometer.

  10. Spike processing with a graphene excitable laser

    PubMed Central

    Shastri, Bhavin J.; Nahmias, Mitchell A.; Tait, Alexander N.; Rodriguez, Alejandro W.; Wu, Ben; Prucnal, Paul R.

    2016-01-01

    Novel materials and devices in photonics have the potential to revolutionize optical information processing, beyond conventional binary-logic approaches. Laser systems offer a rich repertoire of useful dynamical behaviors, including the excitable dynamics also found in the time-resolved “spiking” of neurons. Spiking reconciles the expressiveness and efficiency of analog processing with the robustness and scalability of digital processing. We demonstrate a unified platform for spike processing with a graphene-coupled laser system. We show that this platform can simultaneously exhibit logic-level restoration, cascadability and input-output isolation—fundamental challenges in optical information processing. We also implement low-level spike-processing tasks that are critical for higher level processing: temporal pattern detection and stable recurrent memory. We study these properties in the context of a fiber laser system and also propose and simulate an analogous integrated device. The addition of graphene leads to a number of advantages which stem from its unique properties, including high absorption and fast carrier relaxation. These could lead to significant speed and efficiency improvements in unconventional laser processing devices, and ongoing research on graphene microfabrication promises compatibility with integrated laser platforms. PMID:26753897

  11. Laser techniques for spectroscopy of core-excited atomic levels

    NASA Technical Reports Server (NTRS)

    Harris, S. E.; Young, J. F.; Falcone, R. W.; Rothenberg, J. E.; Willison, J. R.

    1982-01-01

    We discuss three techniques which allow the use of tunable lasers for high resolution and picosecond time scale spectroscopy of core-excited atomic levels. These are: anti-Stokes absorption spectroscopy, laser induced emission from metastable levels, and laser designation of selected core-excited levels.

  12. Pulsed infrared laser ablation and clinical applications

    NASA Astrophysics Data System (ADS)

    Chan, Kin Foong

    Sufficient light energy deposited in tissue can result in ablation and excessive thermal and mechanical damage to adjacent tissues. The goals of this research are to investigate the mechanisms of pulsed infrared laser ablation of tissue, to optimize laser parameters for minimizing unnecessary damage to healthy tissue, and to explore the potential of using pulsed infrared lasers for clinical applications, especially laser lithotripsy. A dual-channel optical low coherence reflectometer was implemented to measure the expansion and collapse velocities of a Q-switched Ho:YAG (λ = 2.12 μm) laser-induced cavitation in water. Cavitation wall velocities up to 11 m/s were measured with this technique, and the results were in fair agreement with those calculated from fast-flash photographic images. The dependence of ablation threshold fluence on calculus absorption was examined. Preliminary results indicated that the product of optical absorption and ablation threshold fluence, which is the heat of ablation, remained constant for a given urinary calculus type and laser pulse duration. An extended study examined the influence of optical absorption on pulsed infrared laser ablation. An analytical photothermal ablation model was applied and compared to experimental ablation results using an infrared free-electron laser at selected wavelengths between 2.12 μm and 6.45 μm Results were in good agreement with the model, and the ablation depths of urinary calculi were highly dependent upon the calculus optical absorption as well as light attenuation within the intrapulse ablation plume. An efficient wavelength for ablation corresponded to the wavelength of the Er:YAG laser (λ = 2.94 μm) suggested this laser should be examined for laser lithotripsy. Schlieren flash photography, acoustic transient measurements with a piezoelectric polyvinylidene-fluoride needle-hydrophone, mass loss measurements, and chemical analyses were employed to study the ablation mechanisms of the free

  13. Infrared imaging results of an excited planar jet

    SciTech Connect

    Farrington, R.B.

    1991-12-01

    Planar jets are used for many applications including heating, cooling, and ventilation. Generally such a jet is designed to provide good mixing within an enclosure. In building applications, the jet provides both thermal comfort and adequate indoor air quality. Increased mixing rates may lead to lower short-circuiting of conditioned air, elimination of dead zones within the occupied zone, reduced energy costs, increased occupant comfort, and higher indoor air quality. This paper discusses using an infrared imaging system to show the effect of excitation of a jet on the spread angle and on the jet mixing efficiency. Infrared imaging captures a large number of data points in real time (over 50,000 data points per image) providing significant advantages over single-point measurements. We used a screen mesh with a time constant of approximately 0.3 seconds as a target for the infrared camera to detect temperature variations in the jet. The infrared images show increased jet spread due to excitation of the jet. Digital data reduction and analysis show change in jet isotherms and quantify the increased mixing caused by excitation. 17 refs., 20 figs.

  14. Nonsequential double ionization with mid-infrared laser fields

    PubMed Central

    Li, Ying-Bin; Wang, Xu; Yu, Ben-Hai; Tang, Qing-Bin; Wang, Guang-Hou; Wan, Jian-Guo

    2016-01-01

    Using a full-dimensional Monte Carlo classical ensemble method, we present a theoretical study of atomic nonsequential double ionization (NSDI) with mid-infrared laser fields, and compare with results from near-infrared laser fields. Unlike single-electron strong-field processes, double ionization shows complex and unexpected interplays between the returning electron and its parent ion core. As a result of these interplays, NSDI for mid-IR fields is dominated by second-returning electron trajectories, instead of first-returning trajectories for near-IR fields. Some complex NSDI channels commonly happen with near-IR fields, such as the recollision-excitation-with-subsequent-ionization (RESI) channel, are virtually shut down by mid-IR fields. Besides, the final energies of the two electrons can be extremely unequal, leading to novel e-e momentum correlation spectra that can be measured experimentally. PMID:27857182

  15. Nonsequential double ionization with mid-infrared laser fields

    NASA Astrophysics Data System (ADS)

    Li, Ying-Bin; Wang, Xu; Yu, Ben-Hai; Tang, Qing-Bin; Wang, Guang-Hou; Wan, Jian-Guo

    2016-11-01

    Using a full-dimensional Monte Carlo classical ensemble method, we present a theoretical study of atomic nonsequential double ionization (NSDI) with mid-infrared laser fields, and compare with results from near-infrared laser fields. Unlike single-electron strong-field processes, double ionization shows complex and unexpected interplays between the returning electron and its parent ion core. As a result of these interplays, NSDI for mid-IR fields is dominated by second-returning electron trajectories, instead of first-returning trajectories for near-IR fields. Some complex NSDI channels commonly happen with near-IR fields, such as the recollision-excitation-with-subsequent-ionization (RESI) channel, are virtually shut down by mid-IR fields. Besides, the final energies of the two electrons can be extremely unequal, leading to novel e-e momentum correlation spectra that can be measured experimentally.

  16. Multiple-photon excitation imaging with an all-solid-state laser

    NASA Astrophysics Data System (ADS)

    Wokosin, David L.; Centonze, Victoria F.; White, John G.; Hird, Steven N.; Sepsenwol, S.; Malcolm, Graeme P. A.; Maker, Gareth T.; Ferguson, Allister I.

    1996-05-01

    Two-photon excitation imaging is a recently described optical sectioning technique where fluorophore excitation is confined to--and therefore defines--the optical section being observed. This characteristic offers a significant advantage over laser-scanning confocal microscopy; the volume of fluorophore excited in the minimum necessary for imaging, thereby minimizing the destructive effects of fluorophore excitation in living tissues. In addition, a confocal pinhole is not required for optical scattering--thus further reducing the excitation needed for efficient photon collection. We have set up a two-photon excitation imaging system which uses an all-solid-state, short-pulse, long-wavelength laser as an excitation source. The source is a diode-pumped, mode-locked Nd:YLF laser operating in the infrared (1047 nm). This laser is small, has modest power requirements, and has proven reliable and stable in operation. The short laser pulses from the laser are affected by the system optical path; this has been investigated with second harmonic generation derived from a nonlinear crystal. The system has been specifically designed for the study of live biological specimens. Two cell types especially sensitive to high-energy illumination, the developing Caenorhabditis elegans embryo and the crawling sperm of the nematode, Ascaris, were used to demonstrate the dramatic increase in viability when fluorescence is generated by two-photon excitation. The system has the capability of switching between two-photon and confocal imaging modes to facilitate direct comparison of theory of these two optical sectioning techniques on the same specimen. A heavily stained zebra fish embryo was used to demonstrate the increase in sectioning depth when fluorescence is generated by infrared two- photon excitation. Two-photon excitation with the 1047 nm laser produces bright images with a variety of red emitting fluorophores, and some green emitting fluorophores, commonly used in biological

  17. Remote Minefield Detection Using Infrared Laser Radar

    DTIC Science & Technology

    1988-11-01

    Technology of Coherent Infrared Radar, pp. 60, 1981. 22. R.M. Hardesty , T.R. Lawrence, R.A. Richter, et al., "Ground- Based Coherent Lidar Measurement...vegetation damage related to their deployment. High- resolution imaging RMD lidar systems can use this information as a further aid to minefield...example a CO2 laser- based system can be called a ladar, a lidar , an optical radar, or an infrared radar. The most commonly used expressions are lidar and

  18. Longitudinally excited CO2 laser with multiple laser tubes

    NASA Astrophysics Data System (ADS)

    Uno, Kazuyuki; Akitsu, Tetsuya; Jitsuno, Takahisa

    2016-11-01

    We developed a longitudinally excited CO2 laser system that was constituted of two or three laser tubes and a single driving circuit. The multiple laser tubes simultaneously produced almost the same short laser pulses with a spike pulse width of about 164 ns and a pulse tail length of about 74 μs with a single driving circuit. The double-tube system was constituted of two 30 cm-long laser tubes with inner diameters of 13 mm and 16 mm and a single driving circuit with an input energy of 2.18 J. The output energy of the 13 mm-tube was 23.3 mJ, and that of the 16 mm-tube was 21.9 mJ at a gas pressure of 4.2 kPa (CO2:N2:He = 1:1:2). The triple-tube system was constituted of three 30 cm-long laser tubes with inner diameters of 9 mm, 13 mm, and 16 mm and a single driving circuit with an input energy of 2.18 J. The output energy of the 9 mm tube was 15.9 mJ, that of the 13 mm tube was 24.1 mJ, and that of the 16 mm tube was 19.2 mJ at a gas pressure of 4.2 kPa. With the same driving circuit and the same input energy, the total output energies of the multitube laser systems were higher than the output energy of a single-tube system.

  19. Optically Pumped Far Infrared Molecular Lasers.

    DTIC Science & Technology

    1980-04-01

    third and fifth order nonlinear processes can exceed first order laser processes. An experimental study of the generation of a 22.653 GHz signal (the...prime, practical sources. There are no counterparts in the far infrared of devices like IMPATTs, magnetrons, laser diodes, gyrotrons , etc. While in...1,000 GHz , the only proven, high spectral quality, modest technology, coherent source available to all researchers in the area, is the opti- cally

  20. Versatile Chromium-Doped Zinc Selenide Infrared Laser Sources

    DTIC Science & Technology

    2010-05-01

    laser, infrared laser, tunable laser, solid - state laser 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT: SAR 18. NUMBER OF PAGES 72...sensing, IR countermeasures, laser surgery and non-invasive imaging are just a few of the drivers of high-power solid - state mid-IR laser development...2 2.2 Early Solid - state Lasers

  1. CANOES II; Dynamics of Atmospheric Infrared Thermochemical Excitation. Volume 2

    DTIC Science & Technology

    1989-03-01

    4 8 which carried at least 6.5 eV internal energy, in their studies on the excitation of mercuric halides by N2 (A). The energy of the companion...as auroral precursors of infrared radiation ., 20. DISTRIBUTION /AVAILABILITY OF ABSTRACT 21 ABSTRACT SECURITY CLASSIFICATION MUNCLASSIFIED/tINLIMITED...investigate chemiluminescent reactions of atmospherically important radiators which could significantly contribute to emissions in several important

  2. Lasers and infrared thermography: advantageous cooperation.

    PubMed

    Vainer, Boris G

    2016-12-01

    In a brief review, the beneficial outcomes that have arisen from simultaneous use of laser- and infrared thermography (IRT)-based techniques are demonstrated. The most recent literary and original experimental results collected from different research and practical areas are presented. It is shown that modern IRT acts as an indispensable laser partner in various biomedical and many other applications and technologies. And vice versa, the laser-based methods and techniques often serve as an appropriate research instrument enriching IRT measurement data with independently obtained information.

  3. Excitation of nuclear isomers by X rays from laser plasma

    SciTech Connect

    Andreev, Aleksandr A; Karpeshin, F; Trzhaskovskaya, M B; Platonov, Konstantin Yu; Rozhdestvenskii, Yu V

    2010-06-23

    The possibility of obtaining isomer nuclei is studied by the example of the molybdenum isomer {sup 93}Mo upon irradiation of a niobium {sup 93}Nb target by {approx}50-J, 100-fs laser pulses. It is shown that the modern laser technique allows production of isomer nuclei by accelerated protons and radiative de-excitation of isomer nuclear states by thermal or line X-rays from laser plasma. (interaction of laser radiation with matter. laser plasma)

  4. LASERS IN MEDICINE: Two-photon excitation of aluminium phthalocyanines

    NASA Astrophysics Data System (ADS)

    Meshalkin, Yu P.; Alfimov, E. E.; Vasil'ev, N. E.; Denisov, A. N.; Makukha, V. K.; Ogirenko, A. P.

    1999-12-01

    A demonstration is given of the feasibility of two-photon excitation of aluminium phthalocyanine and of the pharmaceutical preparation 'Fotosens', used in photodynamic therapy. The excitation source was an Nd:YAG laser emitting at the 1064 nm wavelength. The spectra of the two-photon-excited luminescence were obtained and the two-photon absorption cross sections were determined.

  5. Gain and Lasing in Nuclear Excited Excimer Laser Systems.

    DTIC Science & Technology

    1981-04-24

    sources. The most advantageous volumetric nuclear excitation source is UF If enriched UF could be used as a pump source, a self- critical NPL could be...3 lower laser state by nuclear excitation and gas heating or by quenching of the upper laser state by UF6 and other species. Most NPLs demonstrated...induced effects, the loss in power density may be more critical than any nuclear considerations.I * Direct nuclear pumping of XeF excimer lasers has been

  6. Infrared laser spectroscopic trace gas sensing

    NASA Astrophysics Data System (ADS)

    Sigrist, Markus

    2016-04-01

    Chemical sensing and analyses of gas samples by laser spectroscopic methods are attractive owing to several advantages such as high sensitivity and specificity, large dynamic range, multi-component capability, and lack of pretreatment or preconcentration procedures. The preferred wavelength range comprises the fundamental molecular absorption range in the mid-infared between 3 and 15 μm, whereas the near-infrared range covers the (10-100 times weaker) higher harmonics and combination bands. The availability of near-infrared and, particularly, of broadly tunable mid-infrared sources like external cavity quantum cascade lasers (EC-QCLs), interband cascade lasers (ICLs), difference frequency generation (DFG), optical parametric oscillators (OPOs), recent developments of diode-pumped lead salt semiconductor lasers, of supercontinuum sources or of frequency combs have eased the implementation of laser-based sensing devices. Sensitive techniques for molecular absorption measurements include multipass absorption, various configurations of cavity-enhanced techniques such as cavity ringdown (CRD), or of photoacoustic spectroscopy (PAS) including quartz-enhanced (QEPAS) or cantilever-enhanced (CEPAS) techniques. The application requirements finally determine the optimum selection of laser source and detection scheme. In this tutorial talk I shall discuss the basic principles, present various experimental setups and illustrate the performance of selected systems for chemical sensing of selected key atmospheric species. Applications include an early example of continuous vehicle emission measurements with a mobile CO2-laser PAS system [1]. The fast analysis of C1-C4 alkanes at sub-ppm concentrations in gas mixtures is of great interest for the petrochemical industry and was recently achieved with a new type of mid-infrared diode-pumped piezoelectrically tuned lead salt vertical external cavity surface emitting laser (VECSEL) [2]. Another example concerns measurements on short

  7. Analysis of infrared laser tissue ablation

    NASA Astrophysics Data System (ADS)

    McKenzie, Gordon P.; Timmerman, Brenda H.; Bryanston-Cross, Peter J.

    2005-04-01

    The mechanisms involved in infrared laser tissue ablation are studied using a free electron laser (FELIX) in order to clarify whether the increased ablation efficiency reported in literature for certain infrared wavelengths is due to a wavelength effect or to the specific pulse structure of the lasers that are generally used in these studies. Investigations are presented of ablation of vitreous from pigs" eyes using several techniques including protein gel electrophoresis and ablation plume visualization. The ablation effects of three different infrared wavelengths are compared: 3 mm, which is currently in clinical surgical use, and the wavelengths associated with the amide I and amide II bands, i.e. 6.2 mm and 6.45mm, respectively. The results suggest a different ablation mechanism to be in operation for each studied wavelength, thus indicating that the generally reported increased ablation efficiency in the 6-6.5 micron range is due to the wavelength rather than the typical free electron laser pulse structure.

  8. Relation Between Discharge Length and Laser Pulse Characteristics in Longitudinally Excited CO2 Laser

    NASA Astrophysics Data System (ADS)

    Uno, Kazuyuki; Dobashi, Kazuma; Akitsu, Tetsuya; Jitsuno, Takahisa

    2013-04-01

    A longitudinally excited CO2 laser pumped by a fast discharge emits a short laser pulse, similarly to TEA and Q-switched CO2 lasers. We investigated the relation between the discharge length and the laser pulse characteristics to develop a longitudinally excited CO2 laser producing a high spike laser pulse. We examined discharge lengths of 30, 45, and 60 cm, using the same mirrors and the same excitation circuit with the same input energy. A longer discharge length increased the discharge volume and improved the laser output energy. However, the longer discharge length caused a long discharge formation time (a slow fall time of the discharge voltage) due to the higher discharge impedance, which resulted in a long laser pulse tail. Therefore, the longitudinally excited CO2 laser had optimum conditions for obtaining a high spike laser pulse effectively.

  9. PLASMA WAKE EXCITATION BY LASERS OR PARTICLE BEAMS

    SciTech Connect

    Schroeder, Carl B.; Esarey, Eric; Benedetti, Carlo; Toth, Csaba; Geddes, Cameron; Leemans, Wim

    2011-04-01

    Plasma accelerators may be driven by the ponderomotive force of an intense laser or the space-charge force of a charged particle beam. Plasma wake excitation driven by lasers or particle beams is examined, and the implications of the different physical excitation mechanisms for accelerator design are discussed. Plasma-based accelerators have attracted considerable attention owing to the ultrahigh field gradients sustainable in a plasma wave, enabling compact accelerators. These relativistic plasma waves are excited by displacing electrons in a neutral plasma. Two basic mechanisms for excitation of plasma waves are actively being researched: (i) excitation by the nonlinear ponderomotive force (radiation pressure) of an intense laser or (ii) excitation by the space-charge force of a dense charged particle beam. There has been significant recent experimental success using lasers and particle beam drivers for plasma acceleration. In particular, for laser-plasma accelerators (LPAs), the demonstration at LBNL in 2006 of high-quality, 1 GeV electron beams produced in approximately 3 cm plasma using a 40 TW laser. In 2007, for beam-driven plasma accelerators, or plasma-wakefield accelerators (PWFAs), the energy doubling over a meter to 42 GeV of a fraction of beam electrons on the tail of an electron beam by the plasma wave excited by the head was demonstrated at SLAC. These experimental successes have resulted in further interest in the development of plasma-based acceleration as a basis for a linear collider, and preliminary collider designs using laser drivers and beam drivers are being developed. The different physical mechanisms of plasma wave excitation, as well as the typical characteristics of the drivers, have implications for accelerator design. In the following, we identify the similarities and differences between wave excitation by lasers and particle beams. The field structure of the plasma wave driven by lasers or particle beams is discussed, as well as the

  10. Near-ultraviolet laser diodes for brilliant ultraviolet fluorophore excitation.

    PubMed

    Telford, William G

    2015-12-01

    Although multiple lasers are now standard equipment on most modern flow cytometers, ultraviolet (UV) lasers (325-365 nm) remain an uncommon excitation source for cytometry. Nd:YVO4 frequency-tripled diode pumped solid-state lasers emitting at 355 nm are now the primary means of providing UV excitation on multilaser flow cytometers. Although a number of UV excited fluorochromes are available for flow cytometry, the cost of solid-state UV lasers remains prohibitively high, limiting their use to all but the most sophisticated multilaser instruments. The recent introduction of the brilliant ultraviolet (BUV) series of fluorochromes for cell surface marker detection and their importance in increasing the number of simultaneous parameters for high-dimensional analysis has increased the urgency of including UV sources in cytometer designs; however, these lasers remain expensive. Near-UV laser diodes (NUVLDs), a direct diode laser source emitting in the 370-380 nm range, have been previously validated for flow cytometric analysis of most UV-excited probes, including quantum nanocrystals, the Hoechst dyes, and 4',6-diamidino-2-phenylindole. However, they remain a little-used laser source for cytometry, despite their significantly lower cost. In this study, the ability of NUVLDs to excite the BUV dyes was assessed, along with their compatibility with simultaneous brilliant violet (BV) labeling. A NUVLD emitting at 375 nm was found to excite most of the available BUV dyes at least as well as a UV 355 nm source. This slightly longer wavelength did produce some unwanted excitation of BV dyes, but at sufficiently low levels to require minimal additional compensation. NUVLDs are compact, relatively inexpensive lasers that have higher power levels than the newest generation of small 355 nm lasers. They can, therefore, make a useful, cost-effective substitute for traditional UV lasers in multicolor analysis involving the BUV and BV dyes.

  11. Two-Photon-Excited Fluorescence-Encoded Infrared Spectroscopy.

    PubMed

    Mastron, Joseph N; Tokmakoff, Andrei

    2016-11-23

    We report on a method for performing ultrafast infrared (IR) vibrational spectroscopy using fluorescence detection. Vibrational dynamics on the ground electronic state driven by femtosecond mid-infrared pulses are detected by changes in fluorescence amplitude resulting from modulation of a two-photon visible transition by nuclear motion. We examine a series of coumarin dyes and study the signals as a function of solvent and excitation pulse parameters. The measured signal characterizes the relaxation of vibrational populations and coherences but yields different information than conventional IR transient absorption measurements. These differences result from the manner in which the ground-state dynamics are projected by the two-photon detection step. Extensions of this method can be adapted for a variety of increased-sensitivity IR measurements.

  12. Formation of infrared solitons in graphene ensemble under Raman excitation

    NASA Astrophysics Data System (ADS)

    Ding, Chunling; Yu, Rong; Yang, Xiaoxue; Zhang, Duo; Huang, Mingju

    2015-11-01

    The formation of infrared solitons in graphene under Raman excitation is investigated using density-matrix approach. We find that the unique band structure and selection rules for the optical transitions near the Dirac point can result in extremely strong optical nonlinearity. Theoretical investigations with the aid of slowly varying envelope approximation and perturbation theory clearly indicate the existence of bright and dark solitons in Landau-quantized graphene. Actually, the formation of spatial soliton in such a material is the consequence of the balance between nonlinear effects and the dispersion properties. Also, the corresponding carrier frequency is tunable in the infrared range. These results can make us know better the crossover between optical solitons and graphene metamaterials. The predicted nonlinear optical effect in graphene may provide a new possibility for designing high-fidelity graphene-based information processing device.

  13. Electrically excited, localized infrared emission from single carbon nanotubes.

    PubMed

    Freitag, Marcus; Tsang, James C; Kirtley, John; Carlsen, Autumn; Chen, Jia; Troeman, Aico; Hilgenkamp, Hans; Avouris, Phaedon

    2006-07-01

    Carbon nanotube field-effect transistors (CNTFETs) produce band gap derived infrared emission under both ambipolar and unipolar transport conditions. We demonstrate here that heterogeneities/defects in the local environment of a CNTFET perturb the local potentials and, as a result, the characteristic bias dependent motion of the ambipolar light emission. Such defects can also introduce localized infrared emission due to impact excitation by carriers accelerated by a voltage drop at the defect. The correlation of the change in the motion of the ambipolarlight emission and of the stationary electroluminescence with the electrical characteristics of the CNTFETs shows that stationaryelectroluminescence can identify "environmental defects" in carbon nanotubes and help evaluate their influence on electrical transport and device operation. A number of different defects are studied involving local dielectric environment changes (partially polymer-covered nanotubes), nanotube-nanotube contacts in looped nanotubes, and nanotube segments close to the electronic contacts. Random defects due to local charging are also observed.

  14. Cine: Line excitation by infrared fluorescence in cometary atmospheres

    NASA Astrophysics Data System (ADS)

    de Val-Borro, Miguel; Cordiner, Martin A.; Milam, Stefanie N.; Charnley, Steven B.

    2017-03-01

    CINE is a Python module for calculating infrared pumping efficiencies that can be applied to the most common molecules found in cometary comae such as water, hydrogen cyanide or methanol. Excitation by solar radiation of vibrational bands followed by radiative decay to the ground vibrational state is one of the main mechanisms for molecular excitation in comets. This code calculates the effective pumping rates for rotational levels in the ground vibrational state scaled by the heliocentric distance of the comet. Line transitions are queried from the latest version of the HITRAN spectroscopic repository using the astroquery affiliated package of astropy. Molecular data are obtained from the LAMDA database. These coefficients are useful for modeling rotational emission lines observed in cometary spectra at sub-millimeter wavelengths. Combined with computational methods to solve the radiative transfer equations based, e.g., on the Monte Carlo algorithm, this model can retrieve production rates and rotational temperatures from the observed emission spectrum.

  15. Ultraviolet 320 nm laser excitation for flow cytometry.

    PubMed

    Telford, William; Stickland, Lynn; Koschorreck, Marco

    2017-02-27

    Although multiple lasers and high-dimensional analysis capability are now standard on advanced flow cytometers, ultraviolet (UV) lasers (usually 325-365 nm) remain an uncommon excitation source for cytometry. This is primarily due to their cost, and the small number of applications that require this wavelength. The development of the Brilliant Ultraviolet (BUV fluorochromes, however, has increased the importance of this formerly niche excitation wavelength. Historically, UV excitation was usually provided by water-cooled argon- and krypton-ion lasers. Modern flow cytometers primary rely on diode pumped solid state lasers emitting at 355 nm. While useful for all UV-excited applications, DPSS UV lasers are still large by modern solid state laser standards, and remain very expensive. Smaller and cheaper near UV laser diodes (NUVLDs) emitting at 375 nm make adequate substitutes for 355 nm sources in many situations, but do not work as well with very short wavelength probes like the fluorescent calcium chelator indo-1. In this study, we evaluate a newly available UV 320 nm laser for flow cytometry. While shorter in wavelength that conventional UV lasers, 320 is close to the 325 nm helium-cadmium wavelength used in the past on early benchtop cytometers. A UV 320 nm laser was found to excite almost all Brilliant Ultraviolet dyes to nearly the same level as 355 nm sources. Both 320 nm and 355 nm sources worked equally well for Hoechst and DyeCycle Violet side population analysis of stem cells in mouse hematopoetic tissue. The shorter wavelength UV source also showed excellent excitation of indo-1, a probe that is not compatible with NUVLD 375 nm sources. In summary, a 320 nm laser module made a suitable substitute for conventional 355 nm sources. This laser technology is available in a smaller form factor than current 355 nm units, making it useful for small cytometers with space constraints. © 2017 International Society for Advancement of Cytometry.

  16. A New Technology for Applanation Free Corneal Trephination: The Picosecond Infrared Laser (PIRL)

    PubMed Central

    Linke, Stephan J.; Frings, Andreas; Ren, Ling; Gomolka, Amadeus; Schumacher, Udo; Reimer, Rudolph; Hansen, Nils-Owe; Jowett, Nathan; Richard, Gisbert; Miller, R. J. Dwayne

    2015-01-01

    The impact of using a Femtosecond laser on final functional results of penetrating keratoplasty is low. The corneal incisions presented here result from laser ablations with ultrafast desorption by impulsive vibrational excitation (DIVE). The results of the current study are based on the first proof-of-principle experiments using a mobile, newly introduced picosecond infrared laser system, and indicate that wavelengths in the mid-infrared range centered at 3 μm are efficient for obtaining applanation-free deep cuts on porcine corneas. PMID:25781907

  17. Oxide glasses for mid-infrared lasers

    NASA Astrophysics Data System (ADS)

    Richards, Billy D. O.; Jha, Animesh; Jose, Gin; Jiang, Xin

    2011-06-01

    We present an overview of rare-earth doped heavy metal oxide and oxy-fluoride glasses which show promise as host materials for lasers operating in the 2-5 μm spectral region for medical, military and sensing applications. By engineering glass composition and purity, tellurite and germanate glasses can support transmission up to and beyond 5 μm and can have favourable thermal, mechanical and environmental stability compared to fluoride glasses. We discuss techniques for glass purification and water removal for enhanced infrared transmission. By comparing the material properties of the glass, and spectroscopic performance of selected rare-earth dopant ions we can identify promising compositions for fibre and bulk lasers in the mid-infrared. Tellurite glass has recently been demonstrated to be a suitable host material for efficient and compact lasers in the {2 μm spectral region in fibre and bulk form and the next challenge is to extend the operating range further into the infrared region where silica fibre is not sufficiently transparent, and provide an alternative to fluoride glass and fibre.

  18. Laser-excited fluorescence for measuring atmospheric pollution

    NASA Technical Reports Server (NTRS)

    Menzies, R. T.

    1975-01-01

    System measures amount of given pollutant at specific location. Infrared laser aimed at location has wavelength that will cause molecules of pollutant to fluoresce. Detector separates fluorescence from other radiation and measures its intensity to indicate concentration of pollutant.

  19. Long-Wavelength Infrared Surface Plasmons on Ga-Doped ZnO Films Excited via 2D Hole Arrays for Extraordinary Optical Transmission (Preprint)

    DTIC Science & Technology

    2013-10-01

    wavelength infrared regime. EOT is facilitated by the excitation of surface plasmon polaritons (SPPs) and can be tuned utilizing the physical...facilitated by the excitation of surface plasmon polaritons (SPPs) and can be tuned utilizing the physical structure size such as period. Pulse laser deposited...plasmonics, infrared, EOT, doped zinc oxides. 1. INTRODUCTION Surface plasmon polaritons (SPPs) are a means of real-time, label-free biosensing

  20. Fast Discharge Circuit for Longitudinally Excited CO2 Laser

    NASA Astrophysics Data System (ADS)

    Uno, Kazuyuki; Hayashi, Hiroyuki; Akitsu, Tetsuya; Jitsuno, Takahisa

    2013-04-01

    In a longitudinally excited CO2 laser with a short laser pulse, similarly to TEA and Q-switched CO2 lasers, a fast discharge is very important. We investigated the use of a fast discharge circuit to obtain a high spike laser pulse in a longitudinally excited CO2 laser. We compared a traditional capacitor-transfer circuit having a buffer capacitance of 700 pF with our direct-drive circuit in which the buffer capacitance is removed. The direct-drive circuit produced a fast discharge and a high spike laser pulse. We also investigated the effect of a resistance connected in parallel with the discharge tube to eliminate low discharge current after the main discharge. A low resistance of 1 kΩ or less acted as a shunt resistance. The shunt resistance was effective in decreasing the energy of the laser pulse tail at high gas pressure.

  1. Effects of Near-Infrared Laser on Neural Cell Activity

    NASA Astrophysics Data System (ADS)

    Mochizuki-Oda, Noriko; Kataoka, Yosky; Yamada, Hisao; Awazu, Kunio

    2004-08-01

    Near-infrared laser has been used to relieve patients from various kinds of pain caused by postherpetic neuralgesia, myofascial dysfunction, surgical and traumatic wound, cancer, and rheumatoid arthritis. Clinically, He-Ne (λ=632.8 nm, 780 nm) and Ga-Al-As (805 ± 25 nm) lasers are used to irradiate trigger points or nerve ganglion. However the precise mechanisms of such biological actions of the laser have not yet been resolved. Since laser therapy is often effective to suppress the pain caused by hyperactive excitation of sensory neurons, interactions with laser light and neural cells are suggested. As neural excitation requires large amount of energy liberated from adenosine triphosphate (ATP), we examined the effect of 830-nm laser irradiation on the energy metabolism of the rat central nervous system and isolated mitochondria from brain. The diode laser was applied for 15 min with irradiance of 4.8 W/cm2 on a 2 mm-diameter spot at the brain surface. Tissue ATP content of the irradiated area in the cerebral cortex was 19 % higher than that of the non-treated area (opposite side of the cortex), whereas the ADP content showed no significant difference. Irradiation at another wavelength (652 nm) had no effect on either ATP or ADP contents. The temperature of the brain tissue was increased 4.5 - 5.0 °C during the irradiation of both 830-nm and 652-nm laser light. Direct irradiation of the mitochondrial suspension did not show any wavelength-dependent acceleration of respiration rate nor ATP synthesis. These results suggest that the increase in tissue ATP content did not result from the thermal effect, but from specific effect of the laser operated at 830 nm. Electrophysiological studies showed the hyperpolarization of membrane potential of isolated neurons and decrease in membrane resistance with irradiation of the laser, suggesting an activation of potassium channels. Intracellular ATP is reported to regulate some kinds of potassium channels. Possible mechanisms

  2. Applications of the Infrared Free Electron Laser in Nonlinear and Time-Resolved Spectroscopy

    NASA Astrophysics Data System (ADS)

    Fann, Wunshain

    1990-01-01

    Free Electron Lasers (FEL) have been envisioned as novel radiation sources tunable over a wide spectral range. In this dissertation I report two types of experiments that used the infrared FEL, Mark III, to study nonlinear optical properties of conjugated polymers and the possibility of long lived vibrational excitations in acetanilide, a hydrogen-bonded molecular crystal.

  3. An infrared search for extraterrestrial laser signals

    NASA Technical Reports Server (NTRS)

    Betz, A.

    1986-01-01

    The focus of project SETI is on microwave frequencies, where receivers fundamentally have the best sensitivity for the detection of narrow band signals. Such receivers, when coupled to existing radio telescopes, form an optimum system for broad area searches over the sky. Detection of narrow band infrared signals is best done with a laser heterodyne reciever similar in function to a microwave spectral line receiver. A receiver was built for astrophysical observations at 30 THz (10 microns) and the spectrometer is being adapted for SETI work. The receiver uses a small CO2 laser as the local oscillator, a HgCdTe diode as the photomixer, and a multichannel intermediate frequency (IF) filterbank. An advanced multichannel IF processor is now being built to detect infrared line radiation in 1000 spectral channels each 1 MHz wide. When completed this processor will be used with a ground based telescope next year for a survey of several hundred selected stars for narrow band CO2 laser signals at 30 THz.

  4. Mid - infrared solid state lasers for spectroscopic applications

    NASA Astrophysics Data System (ADS)

    Terekhov, Yuri

    This work is devoted to study of novel high power middle-infrared (Mid-IR) laser sources enabling development of portable platform for sensing of organic molecules with the use of recently discovered Quartz Enhanced Photo Acoustic Spectroscopy (QEPAS). The ability to detect small concentrations is beneficial to monitor atmosphere pollution as well for biomedical applications such as analysis of human breath to detect earlier stages of cancer or virus activities. A QEPAS technique using a quartz tuning fork (QTF) as a detector enables a strong enhancement of measured signal when pump laser is modulated with a frequency coinciding with a natural frequency of a QTF. It is known that the detectability of acousto-optics based sensors is proportional to the square root of the laser intensity used for detection of analyte. That is the reason why commercially available semiconductor Mid-IR lasers having small output power limit sensitivity of modern QEPAS based sensors. The lack of high power broadly tunable lasers operating with a modulation frequency of quartz forks (~ 32.768 kHz) is the major motivation of this study. Commercially available Mid-IR (2-3.3 microm), single frequency, continuous wave (CW) fiber pumped lasers based on transition metal doped chalcogenides (e.g. Cr:ZnSe) prove to be efficient laser sources for organic molecules detection. However, their direct modulation is limited to several kHz, and cannot be directly used in combination with QEPAS. Hence, one objective of this work is to study and develop fiber laser pumped Ho:YAG (Er:YAG)/Cr:ZnSe tandem laser system/s. Ho (Holmium) and/or Er (Erbium) ions having long radiation lifetime (~ 10 ms) can effectively accumulate population inversion under CW fiber laser excitation. Utilization of acousto-optic (AO) modulators in the cavity of Ho:YAG (Er:YAG) laser will enable effective Q-Switching with repetition rate easily reaching the resonance frequency of a QTF. It is expected that utilization of Ho:YAG (Er

  5. Flashlamp-excited dye laser therapy for treatment of cutaneous vascular lesions

    NASA Astrophysics Data System (ADS)

    Goldberg, David J.

    1990-06-01

    Flashlamp excited dye laser therapy represents an exciting new advance in the treatment of a variety of cutaneous vascular lesions. Portwine stains, angiomas and telangiectases can be treated in all age groups with this laser system. This paper will review the physics of flashlamp dye laser photothermolysis. The differences between argon laser photocoagulation and flashlamp excited dye laser therapy will be reviewed.

  6. Investigation of germanium Raman lasers for the mid-infrared.

    PubMed

    De Leonardis, Francesco; Troia, Benedetto; Soref, Richard A; Passaro, Vittorio M N

    2015-06-29

    In this paper we present a detailed theoretical investigation of integrated racetrack Raman lasers based on the germanium material system operating in the mid-infrared beyond the germanium two-photon absorption cut-off wavelength of 3.17 μm. The effective Raman gain has been estimated in waveguides based on germanium-on-silicon, germanium-on-SOI and germanium-on-Si3N4 technology platforms as a function of their crystallographic orientations. Furthermore, general design guidelines have been determined by means of a comparative analysis of Raman laser performance, i.e. the threshold power, polarization and directionality of the excited Stokes signals as a function of racetrack cavity length and directional-coupler dimensions. Finally, the emitted Raman laser power has been evaluated as a function of overall propagation losses and operative wavelengths up to 3.8 μm, while the time dynamics of Raman lasers has been simulated assuming continuous and pulse waves as input pump signals.

  7. Photoluminescence excitation measurements using pressure-tuned laser diodes

    SciTech Connect

    Bercha, Artem; Ivonyak, Yurii; Mędryk, Radosław; Trzeciakowski, Witold A. Dybała, Filip; Piechal, Bernard

    2015-06-15

    Pressure-tuned laser diodes in external cavity were used as tunable sources for photoluminescence excitation (PLE) spectroscopy. The method was demonstrated in the 720 nm-1070 nm spectral range using a few commercial laser diodes. The samples for PLE measurements were quantum-well structures grown on GaAs and on InP. The method is superior to standard PLE measurements using titanium sapphire laser because it can be extended to any spectral range where anti-reflection coated laser diodes are available.

  8. Refractory period of an excitable semiconductor laser with optical injection

    NASA Astrophysics Data System (ADS)

    Garbin, B.; Dolcemascolo, A.; Prati, F.; Javaloyes, J.; Tissoni, G.; Barland, S.

    2017-01-01

    Injection-locked semiconductor lasers can be brought to a neuronlike excitable regime when parameters are set close to the unlocking transition. Here we study experimentally the response of this system to repeated optical perturbations and observe the existence of a refractory period during which perturbations are not able to elicit an excitable response. The results are analyzed via simulations of a set of dynamical equations which reproduced adequately the experimental results.

  9. Picosecond infrared laser (PIRL): an ideal phonomicrosurgical laser?

    PubMed

    Hess, Markus; Hildebrandt, Michael Dominik; Müller, Frank; Kruber, Sebastian; Kroetz, Peter; Schumacher, Udo; Reimer, Rudolph; Kammal, Michael; Püschel, Klaus; Wöllmer, Wolfgang; Miller, Dwayne

    2013-11-01

    A comparison of tissue cutting effects in excised cadaver human vocal folds after incisions with three different instruments [scalpel, CO2 laser and the picosecond infrared laser-(PIRL)] was performed. In total, 15 larynges were taken from human cadavers shortly after death. After deep freezing and thawing for the experiment, the vocal folds suspended in the hemilarynx were incised. Histology and environmental scanning electron microscopy (ESEM) analyses were performed. Damage zones after cold instrument cuts ranged from 51 to 135 μm, as compared to 9-28 μm after cutting with the PIRL. It was shown that PIRL incision had smaller zones of tissue coagulation and tissue destruction, when compared with scalpel and CO2 laser cuts. The PIRL technology provides an (almost) atraumatic laser, which offers a quantum jump towards realistic 'micro'-phonosurgery on a factual cellular dimension, almost entirely avoiding coagulation, carbonization, or other ways of major tissue destruction in the vicinity of the intervention area. Although not available for clinical use yet, the new technique appears promising for future clinical applications, so that technical and methodological characteristics as well as tissue experiments seem worthwhile to be communicated at this stage of development.

  10. Vibrationally Excited Molecules for Chemical Laser

    DTIC Science & Technology

    Briefly reported are studies on elementary, exothermic, atom-molecule reactions in the hopes of discovering basic features of chemical reaction into specific internal energy vibrational modes of the reaction products. The long- range goal of such studies would hopefully be the prediction of specific chemical reactions which might be promising candidates for chemical laser systems.

  11. Thermally excited proton spin-flip laser emission in tokamaks

    SciTech Connect

    Arunasalam, V.; Greene, G.J.

    1993-07-01

    Based on statistical thermodynamic fluctuation arguments, it is shown here for the first time that thermally excited spin-flip laser emission from the fusion product protons can occur in large tokamak devices that are entering the reactor regime of operation. Existing experimental data from TFTR supports this conjecture, in the sense that these measurements are in complete agreement with the predictions of the quasilinear theory of the spin-flip laser.

  12. Phasing of independent laser channels under impact SBS excitation

    SciTech Connect

    Gordeev, A A; Efimkov, V F; Zubarev, I G; Mikhailov, S I

    2015-10-31

    It is shown experimentally that phasing of independent laser channels under impact SBS excitation calls for a stable difference in arm lengths, as in a classical Michelson interferometer. A scheme with automatic compensation for fluctuations of interferometer arm lengths has been proposed and experimentally implemented. This scheme makes it possible to perform stable phasing of two laser channels under standard laboratory conditions. (control of radiation parameters)

  13. The examination of berberine excited state by laser flash photolysis

    NASA Astrophysics Data System (ADS)

    Cheng, Lingli; Wang, Mei; Zhao, Ping; Zhu, Hui; Zhu, Rongrong; Sun, Xiaoyu; Yao, Side; Wang, Shilong

    2009-07-01

    The property of the excited triplet state of berberine (BBR) was investigated by using time-resolved laser flash photolysis of 355 nm in acetonitrile. The transient absorption spectra of the excited triplet BBR were obtained in acetonitrile, which have an absorption maximum at 420 nm. And the ratio of excitation to ionization of BBR in acetonitrile solvent was calculated. The self-decay and self-quenching rate constants, and the absorption coefficient of 3BBR* were investigated and the excited state quantum yield was determined. Furthermore utilizing the benzophenone (BEN) as a triplet sensitizer, and the β-carotene (Car) as an excited energy transfer acceptor, the assignment of 3BBR* was further confirmed and the related energy transfer rate constants were also determined.

  14. Optical measurement of temperature in biological cells under infrared laser light exposure (λ=800 nm)

    NASA Astrophysics Data System (ADS)

    Moreau, David; Lefort, Claire; Leveque, Philippe; O'Connor, Rod P.

    2015-07-01

    Interest in the interaction between laser light and biological samples has gained momentum in recent years, particularly in neurobiology, where there is significant potential to stimulate neurons with infrared laser light. Despite recent reports showing the application of infrared light for neurostimulation, the underlying mechanism is still unknown. The two main hypotheses are based on thermal or electrostatic mechanisms. Here, a novel optical method is presented to make temperature measurements in human neural cells under infrared laser excitation (λ=800nm) using the dye Rhodamine B (RhB). The measurement of temperature is based on the property of RhB, a fluorescent dye whose fluorescence intensity decreases linearly with increases in temperature. We present and detail the setup and measurement procedure that has temporal resolution of few milliseconds, based around a fluorescent live-cell imaging microscope used for cellular microfluorimetry experiments.

  15. Pulse-shaping circuit for laser excitation

    NASA Technical Reports Server (NTRS)

    Laudenslager, J. B.; Pacala, T. J.

    1981-01-01

    Narrower, impedence-matched pulses initiate stabler electric discharges for gas lasers. Discharges are more efficient, more compact, capable of high repetition rate, and less expensive than conventional electron-beam apparatus, but gas tends to break down and form localized arcs. Pulse-shaping circuit compresses width of high-voltage pulses from relatively-slow rise-time voltage generator and gradually grades circuit impedance from inherent high impedance of generator to low impedence of gas.

  16. Multiple intermolecular bend vibrational excitation of a hydrogen bond: An extended infrared study of OCOHF

    NASA Astrophysics Data System (ADS)

    Nesbitt, David J.; Lovejoy, Christopher M.

    1990-12-01

    We report the use of near infrared tunable difference frequency laser absorption methods to investigate low-frequency bending of the intermolecular hydrogen bond in OCOHF complexes. By deliberate thermal warming of the slit jet expansion to 16 K, we observe bending ``hot band'' transitions built on the fundamental vHF=1←0 HF stretch from the lowest five internally excited bending states (i.e., vlbend=00←00, 11←11, 20←20, 22←22, and 31←31) which correspond to low-frequency, skeletal bending of the intermolecular hydrogen bond. In addition, much weaker parallel (Δl=0) combination band transitions (vlbend=20←00 and 31←11 ) are observed at ≲5% of the 00←00 intensity. Furthermore, measurements of the extremely weak 11←00 perpendicular (Δl=1) band are obtained at ≲1% of the 00←00 intensity. The fundamental, hot band, and combination band data permit quantitative measurement of the absolute vibrational energies of all vibrational levels for the l=0 and 1 manifolds in both HF excited (vHF=1) and ground-state (vHF=0) complexes. The bending frequencies are surprisingly low (˜10 cm-1 ) and exhibit positive anharmonicity (i.e., the energy level spacings increase with vlbend ). The results suggest nearly unrestricted bending of the hydrogen bond in a very flat, highly anharmonic angular potential. In contrast with many other weakly bound complexes, the lowest bending frequency decreases dramatically upon HF excitation, which signals a vHF vibrationally induced shift from a linear to a nonlinear equilibrium geometry for the vHF=1 excited OCOHF potential surface. Excess Lorentzian line widths are observed in all OCOHF transitions, attributable to vibrational predissociation lifetimes that vary smoothly from 1.2 ns (vlbend=00) to 650 ps (vlbend=31) as a function of intermolecular bending excitation.

  17. Radio frequency excited CO/sub 2/ waveguide lasers

    SciTech Connect

    Sinclair, R.L.; Tulip, J.L.

    1984-10-01

    This paper reports on the operation of radio frequency (rf) excited carbon dioxide waveguide lasers. An efficiency of greater than 10% has been achieved with a maximum power of 21 W. The effects of bore size, waveguide fabrication techniques, and gas mixture are discussed.

  18. Comparative hazard evaluation of near-infrared diode lasers.

    PubMed

    Marshall, W J

    1994-05-01

    Hazard evaluation methods from various laser protection standards differ when applied to extended-source, near-infrared lasers. By way of example, various hazard analyses are applied to laser training systems, which incorporate diode lasers, specifically those that assist in training military or law enforcement personnel in the proper use of weapons by simulating actual firing by the substitution of a beam of near-infrared energy for bullets. A correct hazard evaluation of these lasers is necessary since simulators are designed to be directed toward personnel during normal use. The differences among laser standards are most apparent when determining the hazard class of a laser. Hazard classification is based on a comparison of the potential exposures with the maximum permissible exposures in the 1986 and 1993 versions of the American National Standard for the Safe Use of Lasers, Z136.1, and the accessible emission limits of the federal laser product performance standard. Necessary safety design features of a particular system depend on the hazard class. The ANSI Z136.1-1993 standard provides a simpler and more accurate hazard assessment of low-power, near-infrared, diode laser systems than the 1986 ANSI standard. Although a specific system is evaluated, the techniques described can be readily applied to other near-infrared lasers or laser training systems.

  19. Relative refractory period in an excitable semiconductor laser.

    PubMed

    Selmi, F; Braive, R; Beaudoin, G; Sagnes, I; Kuszelewicz, R; Barbay, S

    2014-05-09

    We report on experimental evidence of neuronlike excitable behavior in a micropillar laser with saturable absorber. We show that under a single pulsed perturbation the system exhibits subnanosecond response pulses and analyze the role of the laser bias pumping. Under a double pulsed excitation we study the absolute and relative refractory periods, similarly to what can be found in neural excitability, and interpret the results in terms of a dynamical inhibition mediated by the carrier dynamics. These measurements shed light on the analogy between optical and biological neurons and pave the way to fast spike-time coding based optical systems with a speed several orders of magnitude faster than their biological or electronic counterparts.

  20. Atomic excitation and acceleration in strong laser fields

    NASA Astrophysics Data System (ADS)

    Zimmermann, H.; Eichmann, U.

    2016-10-01

    Atomic excitation in the tunneling regime of a strong-field laser-matter interaction has been recently observed. It is conveniently explained by the concept of frustrated tunneling ionization (FTI), which naturally evolves from the well-established tunneling picture followed by classical dynamics of the electron in the combined laser field and Coulomb field of the ionic core. Important predictions of the FTI model such as the n distribution of Rydberg states after strong-field excitation and the dependence on the laser polarization have been confirmed in experiments. The model also establishes a sound basis to understand strong-field acceleration of neutral atoms in strong laser fields. The experimental observation has become possible recently and initiated a variety of experiments such as atomic acceleration in an intense standing wave and the survival of Rydberg states in strong laser fields. Furthermore, the experimental investigations on strong-field dissociation of molecules, where neutral excited fragments after the Coulomb explosion of simple molecules have been observed, can be explained. In this review, we introduce the subject and give an overview over relevant experiments supplemented by new results.

  1. Polarization methods for diode laser excitation of solid state lasers

    DOEpatents

    Holtom, Gary R.

    2008-11-25

    A mode-locked laser employs a coupled-polarization scheme for efficient longitudinal pumping by reshaped laser diode bars. One or more dielectric polarizers are configured to reflect a pumping wavelength having a first polarization and to reflect a lasing wavelength having a second polarization. A Yb-doped gain medium can be used that absorbs light having a first polarization and emits light having a second polarization. Using such pumping with laser cavity dispersion control, pulse durations of less than 100 fs can be achieved.

  2. Electrodes for transversely excited gas lasers

    SciTech Connect

    Eldridge, R.E

    1989-05-23

    An electrode for a transverse gas flow laser is described comprising: an elongated member having a substantially flat top surface and a substantially flat bottom surface, the top and the bottom surfaces being disposed substantially parallel one to another, the member further having opposing ends of substantially semicircular shape. The member further has a substantially vertical side wall extending perpendicularly upwards from the bottom surface and surrounding the member, the side wall and the top surface being joined by a convex transition region having a given, substantially constant radius of curvature, the substantially constant radius of curvature enabling the electrode to be used use over a range of at least approximately 5,000 volts of discharge potential.

  3. Visible-near-infrared luminescent lanthanide ternary complexes based on beta-diketonate using visible-light excitation.

    PubMed

    Sun, Lining; Qiu, Yannan; Liu, Tao; Feng, Jing; Deng, Wei; Shi, Liyi

    2015-11-01

    We used the synthesized dinaphthylmethane (Hdnm) ligand whose absorption extends to the visible-light wavelength, to prepare a family of ternary lanthanide complexes, named as [Ln(dnm)3 phen] (Ln = Sm, Nd, Yb, Er, Tm, Pr). The properties of these complexes were investigated by Fourier transform infrared (FT-IR) spectroscopy, diffuse reflectance (DR) spectroscopy, thermogravimetric analyses, and excitation and emission spectroscopy. Generally, excitation with visible light is much more advantageous than UV excitation. Importantly, upon excitation with visible light (401-460 nm), the complexes show characteristic visible (Sm(3+)) as well as near-infrared (Sm(3+), Nd(3+), Yb(3+), Er(3+), Tm(3+), Pr(3+)) luminescence of the corresponding lanthanide ions, attributed to the energy transfer from the ligands to the lanthanide ions, an antenna effect. Now, using these near-infrared luminescent lanthanide complexes, the luminescent spectral region from 800 to 1650 nm, can be covered completely, which is of particular interest for biomedical imaging applications, laser systems, and optical amplification applications.

  4. Dynamics Of Electronic Excitation Of Solids With Ultrashort Laser Pulse

    SciTech Connect

    Medvedev, Nikita; Rethfeld, Baerbel

    2010-10-08

    When ultrashort laser pulses irradiate a solid, photoabsorption by electrons in conduction band produces nonequilibrium highly energetic free electrons gas. We study the ionization and excitation of the electronic subsystem in a semiconductor and a metal (solid silicon and aluminum, respectively). The irradiating femtosecond laser pulse has a duration of 10 fs and a photon energy of h-bar {omega} = 38 eV. The classical Monte Carlo method is extended to take into account the electronic band structure and Pauli's principle for electrons excited to the conduction band. In the case of semiconductors this applies to the holes as well. Conduction band electrons and valence band holes induce secondary excitation and ionization processes which we simulate event by event. We discuss the transient electron dynamics with respect to the differences between semiconductors and metals. For metals the electronic distribution is split up into two branches: a low energy distribution as a slightly distorted Fermi-distribution and a long high energy tail. For the case of semiconductors it is split into two parts by the band gap. To thermalize, these excited electronic subsystems need longer times than the characteristic pulse duration. Therefore, the analysis of experimental data with femtosecond lasers must be based on non-equilibrium concepts.

  5. Comprehensive Studies of Ultrafast Laser Excited Warm Dense Gold

    NASA Astrophysics Data System (ADS)

    Chen, Zhijiang; Mo, Mianzhen; Russell, Brandon; Tsui, Ying; Wang, Xijie; Ng, Andrew; Glenzer, Siegfried

    2016-10-01

    Isochoric excitation of solids by ultrafast laser pulses is an important approach to generate warm dense matter in laboratory. Electrical conductivity, structural dynamics and lattice stabilities are the most important properties in ultrafast laser excited warm dense matter. To investigate these properties, we have developed multiple advanced capabilities at SLAC recently, including the measurement of semi-DC electrical conductivity with ultrafast THz radiation, the study of solid and liquid structural dynamics by ultrafast electron diffraction (UED), and the investigation of lattice stability using frequency domain interferometry (FDI) on both front and rear surfaces. Due to the non-reversible nature in exciting solid to warm dense matter, all these diagnostics are implemented with single-shot approaches, reducing the uncertainties due to shot-to-shot fluctuations. In this talk, we will introduce these novel capabilities and present some highlighted studies in warm dense gold, which was uniformly excited by ultrafast laser pulses at 400nm. We appreciate the supports from DOE FES under FWP #100182.

  6. Laser Doppler velocimetry based on the optoacoustic effect in a RF-excited CO2 laser.

    PubMed

    Lee, Teaghee; Choi, Jong Woon; Kim, Yong Pyung

    2012-09-01

    We present a compact optoacoustic laser Doppler velocimetry method that utilizes the self-mixing effect in a RF-excited CO(2) laser. A portion of a Doppler-shifted laser beam, produced by irradiating a single wavelength laser beam on a moving object, is mixed with an originally existing laser beam inside a laser cavity. The fine change of pressure in the laser cavity modulated by the Doppler-shifted frequency is detected by a condenser microphone in the laser tube. In our studies, the frequency of the Doppler signal due to the optoacoustic effect was detected as high as 50 kHz. Our measurements also confirmed that the signal varied linearly with the velocity of the external scatterer (the moving object) and the cosine of the angle between the laser beam and the velocity vector of the object.

  7. Mode-locked solid state lasers using diode laser excitation

    DOEpatents

    Holtom, Gary R [Boston, MA

    2012-03-06

    A mode-locked laser employs a coupled-polarization scheme for efficient longitudinal pumping by reshaped laser diode bars. One or more dielectric polarizers are configured to reflect a pumping wavelength having a first polarization and to reflect a lasing wavelength having a second polarization. An asymmetric cavity provides relatively large beam spot sizes in gain medium to permit efficient coupling to a volume pumped by a laser diode bar. The cavity can include a collimation region with a controlled beam spot size for insertion of a saturable absorber and dispersion components. Beam spot size is selected to provide stable mode locking based on Kerr lensing. Pulse durations of less than 100 fs can be achieved in Yb:KGW.

  8. Control of multiphoton molecular excitation with shaped femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Xu, Bingwei

    The work presented in this dissertation describes the use of shaped femtosecond laser pulses to control the outcome of nonlinear optical process and thus to achieve the selectivity for multiphoton molecular transitions. This research could lead to applications in various fields including nonlinear optical spectroscopy, chemical identification, biological imaging, communications, photodynamic therapy, etc. In order to realize accurate pulse shaping of the femtosecond laser pulses, it is essential to measure and correct the spectral phase distortion of such pulses. A method called multiphoton intrapulse interference phase scan is used to do so throughout this dissertation. This method is highly accurate and reproducible, and has been proved in this work to be compatible with any femtosecond pulses regardless of bandwidth, intensity and repetition rate of the laser. The phase control of several quasi-octave laser sources is demonstrated in this dissertation, with the generation of 4.3 fs and 5.9 fs pulses that reach the theoretically predicted transform-limited pulse duration. The excellent phase control achieved also guarantees the reproducibility for selective multiphoton excitations by accurate phase and/or amplitude shaping. Selective two-photon excitation, stimulated Raman scattering and coherent anti-Stokes Raman scattering with a single broadband laser source are demonstrated in this dissertation. Pulse shaping is used to achieve a fast and robust approach to measure the two-photon excitation spectrum from fluorescent molecules, which provide important information for two-photon biological imaging. The selective excitation concept is also applied in the field of remote chemical identification. Detection of characteristic Raman lines for several chemicals using a single beam coherent anti-Stokes Raman scattering spectroscopy from a 12 meter standoff distance is shown, providing a promising approach to standoff detection of chemicals, hazardous contaminations

  9. Transient Infrared Measurement of Laser Absorption Properties of Porous Materials

    NASA Astrophysics Data System (ADS)

    Marynowicz, Andrzej

    2016-06-01

    The infrared thermography measurements of porous building materials have become more frequent in recent years. Many accompanying techniques for the thermal field generation have been developed, including one based on laser radiation. This work presents a simple optimization technique for estimation of the laser beam absorption for selected porous building materials, namely clinker brick and cement mortar. The transient temperature measurements were performed with the use of infrared camera during laser-induced heating-up of the samples' surfaces. As the results, the absorbed fractions of the incident laser beam together with its shape parameter are reported.

  10. Intense excitation source of blue-green laser

    NASA Astrophysics Data System (ADS)

    Han, K. S.

    1985-10-01

    An intense and efficient excitation source for blue-green lasers useful for the space-based satellite laser applications, underwater strategic communication, and measurement of ocean bottom profile is being developed. The source in use, hypocycloidal pinch plasma (HCP), and a newly designed dense-plasma focus (DPF) can produce intense UV photons (200 to 300 nm) which match the absorption spectra of both near UV and blue green dye lasers (300 to 400 nm). During the current project period, the successful enhancement of blue-green laser output of both Coumarin 503 and LD490 dye through the spectral conversion of the HCP pumping light has been achieved with a converter dye BBQ. The factor of enhancement in the blue-green laser output energy of both Coumarin 503 and LD490 is almost 73%. This enhancement will definitely be helpful in achieving the direct high power blue-green laser (> 1 MW) with the existing blue green dye laser. On the other hand the dense-plasma focus (DPF) with new optical coupling has been designed and constructed. For the optimization of the DPF device as the UV pumping light source, the velocity of current sheath and the formation of plasma focus have been measured as function of argon or argon-deuterium fill gas pressure. Finally, the blue-green dye laser (LD490) has been pumped with the DPF device for preliminary tests. Experimental results with the DPF device show that the velocity of the current sheath follows the inverse relation of sq st. of pressure as expected. The blue-green dye (LD490) laser output exceeded 3.1 m at the best cavity tuning of laser system. This corresponds to 3J/1 cu cm laser energy extraction.

  11. Electron scattering by laser-excited barium atoms

    NASA Technical Reports Server (NTRS)

    Register, D. F.; Trajmar, S.; Jensen, S. W.; Poe, R. T.

    1978-01-01

    Inelastic and superelastic scattering of 30- and 100-eV electrons by laser-excited 6s 6p 1P and subsequent cascade-populated 6s 6p 3P, 6s 5d 1D, and 6s 5d 3D Ba atoms have been observed. Absolute differential cross sections for the singlet and relative scattering intensities for the triplet species have been determined in the 5 to 20 deg angular region. Under the present conditions excitations dominate over deexcitations.

  12. Theoretical model for a background noise limited laser-excited optical filter for doubled Nd lasers

    NASA Astrophysics Data System (ADS)

    Shay, Thomas M.; Garcia, Daniel F.

    1990-06-01

    A simple theoretical model for the calculation of the dependence of filter quantum efficiency versus laser pump power in an atomic Rb vapor laser-excited optical filter is reported. Calculations for Rb filter transitions that can be used to detect the practical and important frequency-doubled Nd lasers are presented. The results of these calculations show the filter's quantum efficiency versus the laser pump power. The required laser pump powers required range from 2.4 to 60 mW/sq cm of filter aperture.

  13. Theoretical model for a background noise limited laser-excited optical filter for doubled Nd lasers

    NASA Technical Reports Server (NTRS)

    Shay, Thomas M.; Garcia, Daniel F.

    1990-01-01

    A simple theoretical model for the calculation of the dependence of filter quantum efficiency versus laser pump power in an atomic Rb vapor laser-excited optical filter is reported. Calculations for Rb filter transitions that can be used to detect the practical and important frequency-doubled Nd lasers are presented. The results of these calculations show the filter's quantum efficiency versus the laser pump power. The required laser pump powers required range from 2.4 to 60 mW/sq cm of filter aperture.

  14. Feasibility study: Monodisperse polymer particles containing laser-excitable dyes

    NASA Technical Reports Server (NTRS)

    Vanderhoff, John W.; Chen, Jing-Hong

    1993-01-01

    The objective was to determine the feasibility of the preparation of monodisperse spherical poly(methyl methacrylate) and polystyrene particles that contain laser-excitable dyes in the size range 0.1 microns to 1 cm. Poly(methyl methacrylate) and polystyrene were chosen because of their excellent optical properties. The sphericity was required for uniformity of spectral output of re-irradiated light from the dye-containing particles. The monodispersity was required to give each particle the same optical properties when exposed to laser light.

  15. Nuclear Excitation by a Strong Short Laser Pulse

    SciTech Connect

    Weidenmueller, Hans A.

    2011-05-06

    We derive the conditions on laser energy and photon number under which a short strong laser pulse excites a collective nuclear mode. We use the Giant Dipole Resonance as a representative example, and a random-matrix description of the fine-structure states and perturbation theory as tools. We identify the relevant observable as the nuclear time-decay function. That function is the Fourier transform of the autocorrelation function of the associated scattering matrix and contains information not otherwise available. We evaluate that function in specific cases and show that it may deviate significantly from an exponential.

  16. Entropy driven atomic motion in laser-excited bismuth.

    PubMed

    Giret, Y; Gellé, A; Arnaud, B

    2011-04-15

    We introduce a thermodynamical model based on the two-temperature approach in order to fully understand the dynamics of the coherent A(1g) phonon in laser-excited bismuth. Using this model, we simulate the time evolution of (111) Bragg peak intensities measured by Fritz et al. [Science 315, 633 (2007)] in femtosecond x-ray diffraction experiments performed on a bismuth film for different laser fluences. The agreement between theoretical and experimental results is striking not only because we use fluences very close to the experimental ones but also because most of the model parameters are obtained from ab initio calculations performed for different electron temperatures.

  17. Tabletop Transient Collisional Excitation X-Ray Lasers

    SciTech Connect

    Dunn, J; Li, Y; Osterheld, A L; Nilsen, J; Moon, S J; Fournier, K B; Hunter, J R; Faenov, A; Pikuz, T A; Shlyaptsev, V N

    1999-09-03

    Recent transient collisional excitation x-ray laser experiments are reported using the COMET tabletop laser driver at the Lawrence Livermore National Laboratory (LLNL). Ne-like and Ni-like ion x-ray laser schemes have been investigated with a combination of long 600 ps and short {approximately}1 ps high power laser pulses with 5-10 J total energy. We show small signal gain saturation for x-ray lasers when a reflection echelon traveling wave geometry is utilized. A gain length product of 18 has been achieved for the Ni-like Pd 4d{r_arrow}4p J=0-1 line at 147 {angstrom}, with an estimated output of {approximately}10{micro}J. Strong lasing on the 119 {angstrom} Ni-like Sn line has also been observed. To our knowledge this is the first time gain saturation has been achieved on a tabletop laser driven scheme and is the shortest wavelength tabletop x-ray laser demonstrated to date. In addition, we present preliminary results of the characterization of the line focus uniformity for a Ne-like ion scheme using L-shell spectroscopy.

  18. Effects of clinical infrared laser on superficial radial nerve conduction

    SciTech Connect

    Greathouse, D.G.; Currier, D.P.; Gilmore, R.L.

    1985-08-01

    The purposes of this study were to demonstrate the effects of infrared laser radiation on the sensory nerve conduction of a specified peripheral nerve in man and determine temperature changes in the tissue surrounding the treated nerve. Twenty healthy adults were divided into three groups: control (n = 5); experimental (n = 10), infrared laser radiation at 20 sec/cm2; and experimental (n = 5), infrared laser radiation treatment at 120 sec/cm2. Antidromic sensory nerve conduction studies were performed on the superficial radial nerve of each subject's right forearm. The infrared laser radiation was applied at a fixed intensity for five 1-cm2 segments. Latency, amplitude, and temperature measurements were recorded pretest; posttest; and posttest intervals of 1, 3, 5, 10, and 15 minutes. An analysis of variance with repeated measures was used to examine the data. No significant change was noted in the distal sensory latency or amplitude of the evoked sensory potential in either experimental or control groups as a result of the applications of the infrared laser radiation treatment. This study demonstrates that infrared laser used at clinically applied intensities does not alter conduction of sensory nerves nor does it elevate the subcutaneous temperature.

  19. Excitability in a quantum dot semiconductor laser with optical injection.

    PubMed

    Goulding, D; Hegarty, S P; Rasskazov, O; Melnik, S; Hartnett, M; Greene, G; McInerney, J G; Rachinskii, D; Huyet, G

    2007-04-13

    We experimentally analyze the dynamics of a quantum dot semiconductor laser operating under optical injection. We observe the appearance of single- and double-pulse excitability at one boundary of the locking region. Theoretical considerations show that these pulses are related to a saddle-node bifurcation on a limit cycle as in the Adler equation. The double pulses are related to a period-doubling bifurcation and occur on the same homoclinic curve as the single pulses.

  20. Excited states in the active media of oxygen - iodine lasers

    SciTech Connect

    Azyazov, V N

    2009-11-30

    A review of investigations of kinetic processes in active media oxygen - iodine lasers (OILs) performed in the last decade is presented. The mechanisms of pumping and quenching of electronically and vibrationally excited O{sub 2} and I{sub 2} molecules are considered, and dissociation mechanisms of I{sub 2} in the active medium of the OIL are analysed. The values of kinetic constants of processes proceeding in the active media of OILs are recommended. (review)

  1. Progress in rare-earth-doped mid-infrared fiber lasers.

    PubMed

    Seddon, Angela B; Tang, Zhuoqi; Furniss, David; Sujecki, Slawomir; Benson, Trevor M

    2010-12-06

    The progress, and current challenges, in fabricating rare-earth-doped chalcogenide-glass fibers for developing mid-infrared (IR) fiber lasers are reviewed. For the first time a coherent explanation is forwarded for the failure to date to develop a gallium-lanthanum-sulfide glass mid-IR fiber laser. For the more covalent chalcogenide glasses, the importance of optimizing the glass host and glass processing routes in order to minimize non-radiative decay and to avoid rare earth ion clustering and glass devitrification is discussed. For the first time a new idea is explored to explain an additional method of non-radiative depopulation of the excited state in the mid-IR that has not been properly recognized before: that of impurity multiphonon relaxation. Practical characterization of candidate selenide glasses is presented. Potential applications of mid-infrared fiber lasers are suggested.

  2. Coherent and incoherent structural dynamics in laser-excited antimony

    NASA Astrophysics Data System (ADS)

    Waldecker, Lutz; Vasileiadis, Thomas; Bertoni, Roman; Ernstorfer, Ralph; Zier, Tobias; Valencia, Felipe H.; Garcia, Martin E.; Zijlstra, Eeuwe S.

    2017-02-01

    We investigate the excitation of phonons in photoexcited antimony and demonstrate that the entire electron-lattice interactions, in particular coherent and incoherent electron-phonon coupling, can be probed simultaneously. Using femtosecond electron diffraction (FED) with high temporal resolution, we observe the coherent excitation of the fully symmetric A1 g optical phonon mode via the shift of the minimum of the atomic potential energy surface. Ab initio molecular dynamics simulations on laser excited potential energy surfaces are performed to quantify the change in lattice potential and the associated real-space amplitude of the coherent atomic oscillations. Good agreement is obtained between the parameter-free calculations and the experiment. In addition, our experimental configuration allows observing the energy transfer from electrons to phonons via incoherent electron-lattice scattering events. The electron-phonon coupling is determined as a function of electronic temperature from our DFT calculations and the data by applying different models for the energy transfer.

  3. Antecedents of two-photon excitation laser scanning microscopy.

    PubMed

    Masters, Barry R; So, Peter T C

    2004-01-01

    In 1931, Maria Göppert-Mayer published her doctoral dissertation on the theory of two-photon quantum transitions (two-photon absorption and emission) in atoms. This report describes and analyzes the theoretical and experimental work on nonlinear optics, in particular two-photon excitation processes, that occurred between 1931 and the experimental implementation of two-photon excitation microscopy by the group of Webb in 1990. In addition to Maria Göppert-Mayer's theoretical work, the invention of the laser has a key role in the development of two-photon microscopy. Nonlinear effects were previously observed in different frequency domains (low-frequency electric and magnetic fields and magnetization), but the high electric field strength afforded by lasers was necessary to demonstrate many nonlinear effects in the optical frequency range. In 1978, the first high-resolution nonlinear microscope with depth resolution was described by the Oxford group. Sheppard and Kompfner published a study in Applied Optics describing microscopic imaging based on second-harmonic generation. In their report, they further proposed that other nonlinear optical effects, such as two-photon fluorescence, could also be applied. However, the developments in the field of nonlinear optical stalled due to a lack of a suitable laser source. This obstacle was removed with the advent of femtosecond lasers in the 1980s. In 1990, the seminal study of Denk, Strickler, and Webb on two-photon laser scanning fluorescence microscopy was published in Science. Their paper clearly demonstrated the capability of two-photon excitation microscopy for biology, and it served to convince a wide audience of scientists of the potential capability of the technique.

  4. Ultra-broadband hybrid infrared laser system

    NASA Astrophysics Data System (ADS)

    Budilova, O. V.; Ionin, A. A.; Kinyaevskiy, I. O.; Klimachev, Yu. M.; Kotkov, A. A.; Kozlov, A. Yu.

    2016-03-01

    A hybrid IR laser system consisting of molecular gas lasers with frequency conversion of laser radiation in a solid-state converter (nonlinear crystal) was developed. One of these gas lasers is a carbon monoxide laser operating in multi-line or single-line mode. Another one is a carbon dioxide laser operating in multi-line mode. The two lasers operate under Q-switching with a joint rotating mirror. Due to sum- and difference-frequency generation in nonlinear crystals, the laser system emits within wavelength range from 2.5 to 16.6 μm. The laser system emitting radiation over such an extremely wide wavelength range (2.7 octaves) is of interest for remote sensing and other applications connected with laser beam propagation in the atmosphere.

  5. Mid-infrared laser-spectroscopic sensing of chemical species

    PubMed Central

    Sigrist, Markus W.

    2014-01-01

    This letter reports on mid-infrared laser-based detection and analysis of chemical species. Emphasis is put on broadly tunable laser sources and sensitive detection schemes. Selected examples from our lab illustrate the performance and potential of such systems in various areas including environmental and medical sensing. PMID:26257952

  6. Strong-field physics with mid-infrared lasers

    NASA Astrophysics Data System (ADS)

    Pogorelsky, I. V.

    2002-04-01

    Mid-infrared gas laser technology promises to become a unique tool for research in strong-field relativistic physics. The degree to which physics is relativistic is determined by a ponderomotive potential. At a given intensity, a 10 μm wavelength CO2 laser reaches a 100 times higher ponderomotive potential than the 1 μm wavelength solid state lasers. Thus, we can expect a proportional increase in the throughput of such processes as laser acceleration, x-ray production, etc. These arguments have been confirmed in proof-of-principle Thomson scattering and laser acceleration experiments conducted at BNL and UCLA where the first terawatt-class CO2 lasers are in operation. Further more, proposals for the 100 TW, 100 fs CO2 lasers based on frequency-chirped pulse amplification have been conceived. Such lasers can produce physical effects equivalent to a hypothetical multi-petawatt solid state laser. Ultra-fast mid-infrared lasers will open new routes to the next generation electron and ion accelerators, ultra-bright monochromatic femtosecond x-ray and gamma sources, allow to attempt the study of Hawking-Unruh radiation, and explore relativistic aspects of laser-matter interactions. We review the present status and experiments with terawatt-class CO2 lasers, sub-petawatt projects, and prospective applications in strong-field science. .

  7. UV Resonant Raman Spectrometer with Multi-Line Laser Excitation

    NASA Technical Reports Server (NTRS)

    Lambert, James L.; Kohel, James M.; Kirby, James P.; Morookian, John Michael; Pelletier, Michael J.

    2013-01-01

    A Raman spectrometer employs two or more UV (ultraviolet) laser wavel engths to generate UV resonant Raman (UVRR) spectra in organic sampl es. Resonant Raman scattering results when the laser excitation is n ear an electronic transition of a molecule, and the enhancement of R aman signals can be several orders of magnitude. In addition, the Ra man cross-section is inversely proportional to the fourth power of t he wavelength, so the UV Raman emission is increased by another fact or of 16, or greater, over visible Raman emissions. The Raman-scatter ed light is collected using a high-resolution broadband spectrograph . Further suppression of the Rayleigh-scattered laser light is provi ded by custom UV notch filters.

  8. Scaling of an Optically Pumped Mid-Infrared Rubidium Laser

    DTIC Science & Technology

    2015-03-26

    Figure 3.6. Daylight Solutions Laser Calibration Curve ...................................................20 Figure 3.7. Pulsed Absorption Spectroscopy ...to their high quantum efficiency, good beam quality, small thermal effect compared to other laser systems, and ability to be scaled to high power...the bleached limit of the infrared Rb laser , even at the highest Rb concentration the heat pipe could attain. Additionally, the beam quality of the 12

  9. Tunable Infrared Lasers: Preparing for Expanded use in Environmental Monitoring

    NASA Technical Reports Server (NTRS)

    Menzies, R. T.; Killinger, D. K.

    1994-01-01

    The literature on the use of tunable infrared lasers, for atmospheric trace gas detection and monitoring is about 25 years of age. However, this field, whith its myriad of potential application areas, has always been driven by the available laser technology. As new or improved laser devices become available, with characteristics which lend themselves to operation in compact, nearly autonomous instruments, their application to atmospheric science and environmental measurements expands.

  10. DNA fragmentation and nuclear phenotype in tendons exposed to low-intensity infrared laser

    NASA Astrophysics Data System (ADS)

    de Paoli, Flavia; Ramos Cerqueira, Larissa; Martins Ramos, Mayara; Campos, Vera M.; Ferreira-Machado, Samara C.; Geller, Mauro; de Souza da Fonseca, Adenilson

    2015-03-01

    Clinical protocols are recommended in device guidelines outlined for treating many diseases on empirical basis. However, effects of low-intensity infrared lasers at fluences used in clinical protocols on DNA are controversial. Excitation of endogenous chromophores in tissues and free radicals generation could be described as a consequence of laser used. DNA lesions induced by free radicals cause changes in DNA structure, chromatin organization, ploidy degrees and cell death. In this work, we investigated whether low-intensity infrared laser therapy could alter the fibroblasts nuclei characteristics and induce DNA fragmentation. Tendons of Wistar rats were exposed to low-intensity infrared laser (830 nm), at different fluences (1, 5 and 10 J/cm2), in continuous wave (power output of 10mW, power density of 79.6 mW/cm2). Different frequencies were analyzed for the higher fluence (10 J/cm2), at pulsed emission mode (2.5, 250 and 2500 Hz), with the laser source at surface of skin. Geometric, densitometric and textural parameters obtained for Feulgen-stained nuclei by image analysis were used to define nuclear phenotypes. Significant differences were observed on the nuclear phenotype of tendons after exposure to laser, as well as, high cell death percentages was observed for all fluences and frequencies analyzed here, exception 1 J/cm2 fluence. Our results indicate that low-intensity infrared laser can alter geometric, densitometric and textural parameters in tendon fibroblasts nuclei. Laser can also induce DNA fragmentation, chromatin lost and consequently cell death, using fluences, frequencies and emission modes took out from clinical protocols.

  11. Mid-infrared laser filaments in the atmosphere.

    PubMed

    Mitrofanov, A V; Voronin, A A; Sidorov-Biryukov, D A; Pugžlys, A; Stepanov, E A; Andriukaitis, G; Flöry, T; Ališauskas, S; Fedotov, A B; Baltuška, A; Zheltikov, A M

    2015-02-17

    Filamentation of ultrashort laser pulses in the atmosphere offers unique opportunities for long-range transmission of high-power laser radiation and standoff detection. With the critical power of self-focusing scaling as the laser wavelength squared, the quest for longer-wavelength drivers, which would radically increase the peak power and, hence, the laser energy in a single filament, has been ongoing over two decades, during which time the available laser sources limited filamentation experiments in the atmosphere to the near-infrared and visible ranges. Here, we demonstrate filamentation of ultrashort mid-infrared pulses in the atmosphere for the first time. We show that, with the spectrum of a femtosecond laser driver centered at 3.9 μm, right at the edge of the atmospheric transmission window, radiation energies above 20 mJ and peak powers in excess of 200 GW can be transmitted through the atmosphere in a single filament. Our studies reveal unique properties of mid-infrared filaments, where the generation of powerful mid-infrared supercontinuum is accompanied by unusual scenarios of optical harmonic generation, giving rise to remarkably broad radiation spectra, stretching from the visible to the mid-infrared.

  12. Mid-infrared laser filaments in the atmosphere

    PubMed Central

    Mitrofanov, A. V.; Voronin, A. A.; Sidorov-Biryukov, D. A.; Pugžlys, A.; Stepanov, E. A.; Andriukaitis, G.; Flöry, T.; Ališauskas, S.; Fedotov, A. B.; Baltuška, A.; Zheltikov, A. M.

    2015-01-01

    Filamentation of ultrashort laser pulses in the atmosphere offers unique opportunities for long-range transmission of high-power laser radiation and standoff detection. With the critical power of self-focusing scaling as the laser wavelength squared, the quest for longer-wavelength drivers, which would radically increase the peak power and, hence, the laser energy in a single filament, has been ongoing over two decades, during which time the available laser sources limited filamentation experiments in the atmosphere to the near-infrared and visible ranges. Here, we demonstrate filamentation of ultrashort mid-infrared pulses in the atmosphere for the first time. We show that, with the spectrum of a femtosecond laser driver centered at 3.9 μm, right at the edge of the atmospheric transmission window, radiation energies above 20 mJ and peak powers in excess of 200 GW can be transmitted through the atmosphere in a single filament. Our studies reveal unique properties of mid-infrared filaments, where the generation of powerful mid-infrared supercontinuum is accompanied by unusual scenarios of optical harmonic generation, giving rise to remarkably broad radiation spectra, stretching from the visible to the mid-infrared. PMID:25687621

  13. INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: Excitation of nuclear isomers by X rays from laser plasma

    NASA Astrophysics Data System (ADS)

    Andreev, Aleksandr A.; Platonov, Konstantin Yu; Rozhdestvenskii, Yu V.; Karpeshin, F.; Trzhaskovskaya, M. B.

    2010-06-01

    The possibility of obtaining isomer nuclei is studied by the example of the molybdenum isomer 93Mo upon irradiation of a niobium 93Nb target by ~50-J, 100-fs laser pulses. It is shown that the modern laser technique allows production of isomer nuclei by accelerated protons and radiative de-excitation of isomer nuclear states by thermal or line X-rays from laser plasma.

  14. The kinetics and mechanism of dissociation of metal carbonyls in high infrared laser fields

    NASA Astrophysics Data System (ADS)

    Langsam, Y.; Ronn, A. M.

    1981-01-01

    The method of laser induced dielectric breakdown has been used to study the dissociation of three metal carbonyls. Following non-resonant excitation by a TEA CO 2 laser, amorphous micro-metallic particles are deposited. The identity of the various species within a laser induced plasma for a series of related reactant molecules, has been determined using infrared and visible real time fluorescence techniques. Based upon the energetics of dissociation and the relative magnitudes of the rates of activation and deactivation for various collision partners of the plasma fluorescence, an energy transfer map as well as probable mechanisms are proposed. The kinetics of a variety of chemical reactions under plasma conditions are discussed in terms of elementary collision theory. It is shown that the internal vibration manifold of the metal carbonyls is equilibrated prior to the dissociation in agreement with the majority of laser induced multiphoton dissociation experiments.

  15. Low intensity infrared laser affects expression of oxidative DNA repair genes in mitochondria and nucleus

    NASA Astrophysics Data System (ADS)

    Fonseca, A. S.; Magalhães, L. A. G.; Mencalha, A. L.; Geller, M.; Paoli, F.

    2014-11-01

    Practical properties and physical characteristics of low intensity lasers have made possible their application to treat soft tissue diseases. Excitation of intracellular chromophores by red and infrared radiation at low energy fluences with increase of mitochondrial metabolism is the basis of the biostimulation effect but free radicals can be produced. DNA lesions induced by free radicals are repaired by the base excision repair pathway. In this work, we evaluate the expression of POLγ and APEX2 genes related to repair of mitochondrial and nuclear DNA, respectively. Skin and muscle tissue of Wistar rats were exposed to low intensity infrared laser at different fluences. One hour and 24 hours after laser exposure, tissue samples were withdrawn for total RNA extraction, cDNA synthesis, and evaluation of POLγ and APEX2 mRNA expression by real time quantitative polymerase chain reaction. Skin and muscle tissue of Wistar rats exposed to laser radiation show different expression of POLγ and APEX2 mRNA depending of the fluence and time after exposure. Our study suggests that a low intensity infrared laser affects expression of genes involved in repair of oxidative lesions in mitochondrial and nuclear DNA.

  16. Longitudinally excited CO2 laser with short laser pulse for hard tissue drilling

    NASA Astrophysics Data System (ADS)

    Uno, Kazuyuki; Hayashi, Hiroyuki; Akitsu, Tetsuya; Jitsuno, Takahisa

    2014-02-01

    We developed a longitudinally excited CO2 laser that produces a short laser pulse with a circular beam and a low divergence angle. The laser was very simple and consisted of a 45-cm-long alumina ceramic pipe with an inner diameter of 9 mm, a pulse power supply, a step-up transformer, a storage capacitance, and a spark-gap switch. The laser pulse had a spike pulse width of 103 ns and a pulse tail length of 32.6 μs. The beam cross-section was circular and the full-angle beam divergence was 1.7 mrad. The laser was used to drill ivory samples without carbonization at fluences of 2.3-7.1 J/cm2. The drilling depth of the dry ivory increased with the fluence. The drilling mechanism of the dry ivory was attributed to absorption of the laser light by the ivory.

  17. Airborne laser systems for atmospheric sounding in the near infrared

    NASA Astrophysics Data System (ADS)

    Sabatini, Roberto; Richardson, Mark A.; Jia, Huamin; Zammit-Mangion, David

    2012-06-01

    This paper presents new techniques for atmospheric sounding using Near Infrared (NIR) laser sources, direct detection electro-optics and passive infrared imaging systems. These techniques allow a direct determination of atmospheric extinction and, through the adoption of suitable inversion algorithms, the indirect measurement of some important natural and man-made atmospheric constituents, including Carbon Dioxide (CO2). The proposed techniques are suitable for remote sensing missions performed by using aircraft, satellites, Unmanned Aerial Vehicles (UAV), parachute/gliding vehicles, Roving Surface Vehicles (RSV), or Permanent Surface Installations (PSI). The various techniques proposed offer relative advantages in different scenarios. All are based on measurements of the laser energy/power incident on target surfaces of known geometric and reflective characteristics, by means of infrared detectors and/or infrared cameras calibrated for radiance. Experimental results are presented relative to ground and flight trials performed with laser systems operating in the near infrared (NIR) at λ = 1064 nm and λ = 1550 nm. This includes ground tests performed with 10 Hz and 20 KHz PRF NIR laser systems in a variety of atmospheric conditions, and flight trials performed with a 10 Hz airborne NIR laser system installed on a TORNADO aircraft, flying up to altitudes of 22,000 ft above ground level. Future activities are planned to validate the atmospheric retrieval algorithms developed for CO2 column density measurements, with emphasis on aircraft related emissions at airports and other high air-traffic density environments.

  18. Laser cooling and control of excitations in superfluid helium

    NASA Astrophysics Data System (ADS)

    Harris, G. I.; McAuslan, D. L.; Sheridan, E.; Sachkou, Y.; Baker, C.; Bowen, W. P.

    2016-08-01

    Superfluidity is a quantum state of matter that exists macroscopically in helium at low temperatures. The elementary excitations in superfluid helium have been probed with great success using techniques such as neutron and light scattering. However, measurements of phonon excitations have so far been limited to average thermodynamic properties or the driven response far out of thermal equilibrium. Here, we use cavity optomechanics to probe the thermodynamics of phonon excitations in real time. Furthermore, strong light-matter interactions allow both laser cooling and amplification. This represents a new tool to observe and control superfluid excitations that may provide insight into phonon-phonon interactions, quantized vortices and two-dimensional phenomena such as the Berezinskii-Kosterlitz-Thouless transition. The third sound modes studied here also offer a pathway towards quantum optomechanics with thin superfluid films, including the prospect of femtogram masses, high mechanical quality factors, strong phonon-phonon and phonon-vortex interactions, and self-assembly into complex geometries with sub-nanometre feature size.

  19. Coherent laser excitation of Ba-137 and Ba-138

    NASA Technical Reports Server (NTRS)

    Lam, Kai-Shue

    1992-01-01

    Computations are carried out for the 1S(6s2)-1P(6s,6p) coherent laser excitation of Ba-137 and Ba-138 in a magnetic field. Results are presented for both the steady-state and time-dependent excited-state populations of the Zeeman-split magnetic sublevels. The quantum-statistical Liouville-equation approach (for the reduced density matrix) is compared to the rate-equations approach. Significant differences are found between these, due to the interference between strongly overlapping lines (especially for Ba-137). The time-evolution profiles indicate that the Ba-137 transient time is much longer than that of Ba-138.

  20. Hard-core flashlamp for blue-green laser excitation

    SciTech Connect

    Han, K.S.; Lee, J.K.; Lee, J.H. )

    1988-10-01

    A hard-core flashlamp (HCF) which has a coaxial geometry and an array of inverse pinches was evaluated for blue-green laser excitation. The short pulses ({lt}0.5{mu}s) surface discharges were produced across the core insulator of teflon and alumina. The spectral irradiance of the HCF depends on argon fill gas pressure and the core insulating material. The maximum radiative output of the HCF lies in the region of 340--400 nm (the absorption band of LD 490). An LD490 dye laser pumped by a HCF prototype device had an output of 0.9mJ with a pulse width of 0.5{mu}{ital s} (FWHM).

  1. Transcranial infrared laser stimulation improves rule-based, but not information-integration, category learning in humans.

    PubMed

    Blanco, Nathaniel J; Saucedo, Celeste L; Gonzalez-Lima, F

    2017-03-01

    This is the first randomized, controlled study comparing the cognitive effects of transcranial laser stimulation on category learning tasks. Transcranial infrared laser stimulation is a new non-invasive form of brain stimulation that shows promise for wide-ranging experimental and neuropsychological applications. It involves using infrared laser to enhance cerebral oxygenation and energy metabolism through upregulation of the respiratory enzyme cytochrome oxidase, the primary infrared photon acceptor in cells. Previous research found that transcranial infrared laser stimulation aimed at the prefrontal cortex can improve sustained attention, short-term memory, and executive function. In this study, we directly investigated the influence of transcranial infrared laser stimulation on two neurobiologically dissociable systems of category learning: a prefrontal cortex mediated reflective system that learns categories using explicit rules, and a striatally mediated reflexive learning system that forms gradual stimulus-response associations. Participants (n=118) received either active infrared laser to the lateral prefrontal cortex or sham (placebo) stimulation, and then learned one of two category structures-a rule-based structure optimally learned by the reflective system, or an information-integration structure optimally learned by the reflexive system. We found that prefrontal rule-based learning was substantially improved following transcranial infrared laser stimulation as compared to placebo (treatment X block interaction: F(1, 298)=5.117, p=0.024), while information-integration learning did not show significant group differences (treatment X block interaction: F(1, 288)=1.633, p=0.202). These results highlight the exciting potential of transcranial infrared laser stimulation for cognitive enhancement and provide insight into the neurobiological underpinnings of category learning.

  2. Laser dyes excited by high PRR Nd:YAG laser second-harmonic radiation

    NASA Astrophysics Data System (ADS)

    Soldatov, A. N.; Donin, V. I.; Jakovin, D. V.; Reimer, I. V.

    2008-01-01

    The lasing characteristics of red-emitting dyes in ethanol excited by Nd:YAG laser second-harmonic radiation are examined. The Nd:YAG laser was pumped by a diode matrix. The pump pulse repetition rates (PRRs) were 2.5 - 10 kHz and the pulse duration was 60 - 300 ns. The following dyes were evaluated: oxazine 17, DCM, DCM sp, and pyridine 1. The conversion efficiency for oxazine was 25 % without wavelength selection and 15 % with wavelength selection over the tuning range from 630 to 700 nm. The Nd:YAG and dye laser designs used are described elsewhere [1,2].

  3. Multiphoton dissociation and thermal unimolecular reactions induced by infrared lasers. [REAMPA code

    SciTech Connect

    Dai, H.L.

    1981-04-01

    Multiphoton dissociation (MPD) of ethyl chloride was studied using a tunable 3.3 ..mu..m laser to excite CH stretches. The absorbed energy increases almost linearly with fluence, while for 10 ..mu..m excitation there is substantial saturation. Much higher dissociation yields were observed for 3.3 ..mu..m excitation than for 10 ..mu..m excitation, reflecting bottlenecking in the discrete region of 10 ..mu..m excitation. The resonant nature of the excitation allows the rate equations description for transitions in the quasicontinuum and continuum to be extended to the discrete levels. Absorption cross sections are estimated from ordinary ir spectra. A set of cross sections which is constant or slowly decreasing with increasing vibrational excitation gives good fits to both absorption and dissociation yield data. The rate equations model was also used to quantitatively calculate the pressure dependence of the MPD yield of SF/sub 6/ caused by vibrational self-quenching. Between 1000-3000 cm/sup -1/ of energy is removed from SF/sub 6/ excited to approx. > 60 kcal/mole by collision with a cold SF/sub 6/ molecule at gas kinetic rate. Calculation showed the fluence dependence of dissociation varies strongly with the gas pressure. Infrared multiphoton excitation was applied to study thermal unimolecular reactions. With SiF/sub 4/ as absorbing gas for the CO/sub 2/ laser pulse, transient high temperature pulses were generated in a gas mixture. IR fluorescence from the medium reflected the decay of the temperature. The activation energy and the preexponential factor of the reactant dissociation were obtained from a phenomenological model calculation. Results are presented in detail. (WHK)

  4. Gastric cancer detection based on blood plasma surface-enhanced Raman spectroscopy excited by polarized laser light.

    PubMed

    Feng, Shangyuan; Chen, Rong; Lin, Juqiang; Pan, Jianji; Wu, Yanan; Li, Yongzeng; Chen, Jiesi; Zeng, Haishan

    2011-03-15

    We have recently applied surface-enhanced Raman spectroscopy (SERS) for blood plasma analysis for non-invasive nasopharyngeal cancer detection and obtained good preliminary results. The aim of this study was to develop a more robust SERS spectroscopy based blood plasma analysis method for non-invasive gastric cancer detection. The effect of different laser polarizations (non-polarized, linear-polarized, right-handed circularly polarized, and left-handed circularly polarized) on blood plasma SERS spectroscopy was explored for the first time. Silver nanoparticles as the SERS-substrate were directly mixed with blood plasma to enhance the Raman scattering of various biomolecular constituents. High quality SERS spectra were obtained using a fiber optic probe and a dispersive type near infrared Raman system. Blood plasma samples from gastric cancer patients (n=32) and healthy subjects (n=33) were analyzed. The diagnostic performance for differentiating gastric cancer plasma from normal plasma was evaluated. Principal component analysis combined with linear discriminant analysis (LDA) of the obtained spectral data was used to develop diagnostic algorithms. Classification results obtained from cross-validation of the LDA model based on the four spectral data sets of different laser polarizations demonstrated different diagnostic sensitivities and specificities: 71.9% and 72.7% for non-polarized laser excitation, 75% and 87.9% for linear-polarized laser excitation, 81.3% and 78.8% for right-handed circularly polarized laser excitation, 100% and 97% for left-handed circularly polarized laser excitation. The results from this exploratory study demonstrated that plasma SERS spectroscopy with left-handed circularly polarized laser excitation has great promise of becoming a clinically useful diagnostic tool for non-invasive gastric cancer detection.

  5. Three-photon-excited upconversion luminescence of niobium ions doped silicate glass by a femtosecond laser irradiation.

    PubMed

    Zeng, Huidan; Song, Juan; Chen, Danping; Yuan, Shuanglong; Jiang, Xiongwei; Cheng, Ya; Yang, Yunxia; Chen, Guorong

    2008-04-28

    We report on the bluish green upconversion luminescence of niobium ions doped silicate glass by a femtosecond laser irradiation. The dependence of the fluorescence intensity on the pump power density of laser indicates that the conversion of infrared irradiation to visible emission is dominated by three-photon excitation process. We suggest that the charge transfer from O(2-) to Nb(5+) can efficiently contribute to the bluish green emission. The results indicate that transition metal ions without d electrons play an important role in fields of optics when embedded into silicate glass matrix.

  6. Thermo-optic nonlinearity of the laser dye LDS 867 under low power CW laser excitation

    NASA Astrophysics Data System (ADS)

    Mary, K. A. Ann; Mary, E. J. Sonia; Vidyadharan, Viji; Philip, Reji; Unnikrishnan, N. V.

    2015-02-01

    Thermally induced optical nonlinearity of the laser dye LDS 867 is studied in ethanol solution using the self phase modulation and closed aperture z-scan techniques, employing a continuous wave low power He-Ne laser beam for excitation. The nonlinear optical (NLO) coefficients are obtained by analyzing the z-scan curve on the basis of the thermal lens model. The dye exhibits a negative thermal nonlinearity which can be inferred from the occurrence of a pre-focal peak followed by a post-focal valley in the z-scan. The large nonlinear refractive index (n2) measured at the excitation wavelength of 633nm reveals that the material is NLO active even at low excitation powers of less than 1 mW. Results indicate that LDS 867 is a promising material for optical power limiting applications.

  7. Non Destructive Testing by active infrared thermography coupled with shearography under same optical heat excitation

    NASA Astrophysics Data System (ADS)

    Theroux, Louis-Daniel; Dumoulin, Jean; Maldague, Xavier

    2014-05-01

    As infrastructures are aging, the evaluation of their health is becoming crucial. To do so, numerous Non Destructive Testing (NDT) methods are available. Among them, thermal shearography and active infrared thermography represent two full field and contactless methods for surface inspection. The synchronized use of both methods presents multiples advantages. Most importantly, both NDT are based on different material properties. Thermography depend on the thermal properties and shearography on the mechanical properties. The cross-correlation of both methods result in a more accurate and exact detection of the defects. For real site application, the simultaneous use of both methods is simplified due to the fact that the excitation method (thermal) is the same. Active infrared thermography is the measure of the temperature by an infrared camera of a surface subjected to heat flux. Observation of the variation of temperature in function of time reveal the presence of defects. On the other hand, shearography is a measure of out-of-plane surface displacement. This displacement is caused by the application of a strain on the surface which (in our case) take the form of a temperature gradient inducing a thermal stress To measure the resulting out-of-plane displacement, shearography exploit the relation between the phase difference and the optical path length. The phase difference is measured by the observation of the interference between two coherent light beam projected on the surface. This interference is due to change in optical path length as the surface is deformed [1]. A series of experimentation have been conducted in laboratory with various sample of concrete reinforced with CFRP materials. Results obtained reveal that with both methods it was possible to detect defects in the gluing. An infrared lamp radiating was used as the active heat source. This is necessary if measurements with shearography are to be made during the heating process. A heating lamp in the

  8. Near-infrared laser-induced generation of three rare conformers of glycolic acid.

    PubMed

    Halasa, Anna; Lapinski, Leszek; Reva, Igor; Rostkowska, Hanna; Fausto, Rui; Nowak, Maciej J

    2014-07-31

    Structural transformations were induced in conformers of glycolic acid by selective excitation with monochromatic tunable near-infrared laser light. For the compound isolated in Ar matrixes, near-IR excitation led to generation of two higher-energy conformers (GAC; AAT) differing from the most stable SSC form by 180° rotation around the C-C bond. A detailed investigation of this transformation revealed that one conformer (GAC) is produced directly from the near-IR-excited most stable conformer. The other higher-energy conformer (AAT) was effectively generated only upon excitation of the primary photoproduct (GAC) with another near-IR photon. Once these higher-energy conformers of glycolic acid were generated in an Ar matrix, they could be subsequently transformed into one another upon selective near-IR excitations. Interestingly, no repopulation of the initial most stable SSC conformer occurred upon near-IR excitation of the higher-energy forms of the compound isolated in solid Ar. A dramatically different picture of near-IR-induced conformational transformations was observed for glycolic acid isolated in N2 matrixes. In this case, upon near-IR excitation, the most stable SSC form converted solely into a new conformer (SST), where the acid OH group is rotated by 180°. This conformational transformation was found to be photoreversible. Moreover, SST conformer, photoproduced in the N2 matrix, spontaneously converted to the most stable SSC form of glycolic acid, when the matrix was kept at cryogenic temperature and in the dark.

  9. Pulsed CO2 laser pumped by an all solid-state magnetic exciter

    NASA Astrophysics Data System (ADS)

    Shimada, T.; Noda, K.; Obara, M.; Midorikawa, K.

    1985-11-01

    An all solid-state exciter, which consists of a Silicon Controlled Rectifier (SCR) switched pulse transformer and a three stage magnetic pulse compressor, has been successfully used for pulsed CO2 laser excitation. Using the exciter, output laser energy of 240 mJ has been obtained at 1 pps under sealed-off conditions. Since this laser has no discharge switch, long lifetime operation with high repetition rate (HRR) is anticipated.

  10. Coded excitation for infrared non-destructive testing of carbon fiber reinforced plastics.

    PubMed

    Mulaveesala, Ravibabu; Venkata Ghali, Subbarao

    2011-05-01

    This paper proposes a Barker coded excitation for defect detection using infrared non-destructive testing. Capability of the proposed excitation scheme is highlighted with recently introduced correlation based post processing approach and compared with the existing phase based analysis by taking the signal to noise ratio into consideration. Applicability of the proposed scheme has been experimentally validated on a carbon fiber reinforced plastic specimen containing flat bottom holes located at different depths.

  11. Spectrochemical analysis of powdered biological samples using transversely excited atmospheric carbon dioxide laser plasma excitation

    NASA Astrophysics Data System (ADS)

    Zivkovic, Sanja; Momcilovic, Milos; Staicu, Angela; Mutic, Jelena; Trtica, Milan; Savovic, Jelena

    2017-02-01

    The aim of this study was to develop a simple laser induced breakdown spectroscopy (LIBS) method for quantitative elemental analysis of powdered biological materials based on laboratory prepared calibration samples. The analysis was done using ungated single pulse LIBS in ambient air at atmospheric pressure. Transversely-Excited Atmospheric pressure (TEA) CO2 laser was used as an energy source for plasma generation on samples. The material used for the analysis was a blue-green alga Spirulina, widely used in food and pharmaceutical industries and also in a few biotechnological applications. To demonstrate the analytical potential of this particular LIBS system the obtained spectra were compared to the spectra obtained using a commercial LIBS system based on pulsed Nd:YAG laser. A single sample of known concentration was used to estimate detection limits for Ba, Ca, Fe, Mg, Mn, Si and Sr and compare detection power of these two LIBS systems. TEA CO2 laser based LIBS was also applied for quantitative analysis of the elements in powder Spirulina samples. Analytical curves for Ba, Fe, Mg, Mn and Sr were constructed using laboratory produced matrix-matched calibration samples. Inductively coupled plasma optical emission spectroscopy (ICP-OES) was used as the reference technique for elemental quantification, and reasonably well agreement between ICP and LIBS data was obtained. Results confirm that, in respect to its sensitivity and precision, TEA CO2 laser based LIBS can be successfully applied for quantitative analysis of macro and micro-elements in algal samples. The fact that nearly all classes of materials can be prepared as powders implies that the proposed method could be easily extended to a quantitative analysis of different kinds of materials, organic, biological or inorganic.

  12. Excitation Mechanisms of Near-Infrared Emission Lines in LINER Galaxies

    NASA Astrophysics Data System (ADS)

    Boehle, Anna

    2017-01-01

    I will present high spatial resolution, integral field spectroscopic observations of the nearby LINER (low ionization nuclear emission line region) galaxy NGC 404. LINERs are found at the centers of ~1/3 of galaxies within 40 Mpc, but their physical nature is not well understood. Although NGC 404 is thought to host a intermediate mass black hole at its center, it is unclear whether accretion onto the black hole or another mechanism such as shock excitation drives its LINER emission. We use the OSIRIS near-infrared integral field spectrograph at Keck Observatory behind laser guide star adaptive optics to map the strength and kinematics of [FeII], H2, and hydrogen recombination lines in the nucleus of NGC 404. These observations have a spatial pixel sampling of 0.5 pc and span the central 30 pc of the galaxy. We find that the ionized and molecular gas show differences in their morphology and kinematics on parsec scales. In particular, there are regions with line ratios of [FeII]/Pa-β that are much higher than previously seen in spatially integrated spectra, significantly restricting the possible excitation mechanisms of the near-infrared emission lines in this source. We are also applying these analysis techniques to 10 additional nearby LINERs, a part of a larger sample of 14 sources, to understand what drives the emission lines in these active galaxies. As a part of this program, I worked on the upgrade of the detector in the OSIRIS spectrograph, which has allowed observations for this survey obtained since January 2016 to be taken with increased instrument sensitivity of a factor of ~2 at J-band wavelengths (1.2 - 1.4 microns) and ~1.6 at H- and K-band wavelengths (1.5 - 2.4 microns). I will present results from the LINER survey, the OSIRIS detector upgrade, and also touch on related work using stellar orbits around the Milky Way supermassive black hole Sgr A* to constrain the mass and distance to our own Galactic Center.

  13. Infrared laser stimulation of retinal and vestibular neurons

    NASA Astrophysics Data System (ADS)

    Bardin, Fabrice; Bec, Jean-Michel; Albert, Emmanuelle S.; Hamel, Christian; Dupeyron, Gérard; Chabbert, Christian; Marc, Isabelle; Dumas, Michel

    2011-03-01

    The study of laser-neuron interaction has gained interest over the last few years not only for understanding of fundamental mechanisms but also for medical applications such as prosthesis because of the non-invasive characteristic of the laser stimulation. Several authors have shown that near infrared lasers are able to stimulate neurons. It is suggested that a thermal gradient induced by the absorption of the laser radiation on cells is the primary effect but the exact mechanism remains unclear. We show in this work that infrared laser radiations provide a possible way for stimulating retinal and vestibular ganglion cells. We describe relevant physical characteristics allowing safe and reproducible neuron stimulations by single infrared pulses. Calcium fluorescence imaging and electrophysiological recordings have been used to measure ionic exchanges at the neuron membrane. The stimulation system is based on a pulsed laser diode beam of a few mW. Effects of three different wavelengths (from 1470 to 1875 nm) and stimulation durations have been investigated. Variations of the stimulation energy thresholds suggest that the main physical parameter is the water optical absorption. Measurements of the temperature at the cell membrane show that a constant temperature rise is required to stimulate neurons, suggesting a photothermal process.

  14. Visible and Near-Infrared Dissociation Lasers.

    DTIC Science & Technology

    1984-07-01

    NUMBERS(s J. G. Eden N00014-82-K-0209 S. PERFORMING ORGANIZATION NAME AND ADDRESS 10 PROGRAM ELEMENT. PROJECT. TASK 9., Dent. of Electrical and Computer...of the viability of this system as a tunable green amplifier. B. Cdl Discharge-Pumped Laser Tunable, efficient sources of coherent radiation in the...in the gain spectrum. As a demonstration of the tunability of new laser media in the visible, an injection locking experiment has been performed on a

  15. Non-destructive Testing by Infrared Thermography Under Random Excitation and ARMA Analysis

    NASA Astrophysics Data System (ADS)

    Bodnar, J. L.; Nicolas, J. L.; Candoré, J. C.; Detalle, V.

    2012-11-01

    Photothermal thermography is a non-destructive testing (NDT) method, which has many applications in the field of control and characterization of thin materials. This technique is usually implemented under CW or flash excitation. Such excitations are not adapted for control of fragile materials or for multi-frequency analysis. To allow these analyses, in this article, the use of a new control mode is proposed: infrared thermography under random excitation and auto regressive moving average analysis. First, the principle of this NDT method is presented. Then, the method is shown to permit detection, with low energy constraints, of detachments situated in mural paintings.

  16. Activation of molecular oxygen by infrared laser radiation in pigment-free aerobic systems.

    PubMed

    Krasnovsky, A A; Drozdova, N N; Ivanov, A V; Ambartsumian, R V

    2003-09-01

    With the goal of mimicking the mechanisms of the biological effects of low energy laser irradiation, we have shown that infrared low intensity laser radiation causes oxygenation of the chemical traps of singlet oxygen dissolved in organic media and water saturated by air at normal atmospheric pressure. The photooxygenation rate was directly proportional to the oxygen concentration and strongly inhibited by the singlet oxygen quenchers. The maximum of the photooxygenation action spectrum coincided with the maximum of the oxygen absorption band at 1270 nm. The data provide unambiguous evidence that photooxygenation is determined by the reactive singlet (1)Delta(g )state formed as a result of direct laser excitation of molecular oxygen. Hence, activation of oxygen caused by its direct photoexcitation may occur in natural systems.

  17. Intratissue surgery with 80 MHz nanojoule femtosecond laser pulses in the near infrared

    NASA Astrophysics Data System (ADS)

    Koenig, Karsten; Krauss, Oliver; Riemann, Iris

    2002-02-01

    The use of 1 nanojoule near infrared 80 MHz femtosecond laser pulses for highly precise intratissue processing, in particular for intraocular refractive surgery, was evaluated. Destructive optical breakdown at TW/cm2 light intensities in a subfemtoliter intrastromal volume was obtained by diffraction-limited focussing with an 40x objective (N.A. 1.3) and beam scanning 50 to 140 µm below the epithelial surface. Using the same system at GW/cm2 intensities two-photon excited autofluorescence imaging was used to determine the target of interest and to visualize intraocular laser effects. Histological examination of laser-exposed porcine eyes reveal a minimum cut size below 1 µm without destructive effects to surrounding tissues.

  18. Infrared laser diode with visible illuminator for biomedical stimulation

    NASA Astrophysics Data System (ADS)

    Strek, Wieslaw; Podbielska, Halina; Szafranski, C.; Kuzmin, Andrei N.; Ges, J. A.; Ryabtsev, Gennadii I.

    1995-02-01

    The special laser diode device (LDD) leasing in the near infrared region (IR) with two wavelengths: (lambda) 1 equals 850 nm and (lambda) 2 equals 1000 nm, designed for laser therapy, is presented. This device is characterized by a unique feature, namely a separate built-in illuminator, operating in 670 nm. The special construction of LDD and the illuminator enables the user to visualize exactly the surface irradiated by IR radiation. The exposure time and the output of laser power are also controlled and can be displayed on the LED monitor at the front panel. This new device, described here, is compact, low cost, and user friendly.

  19. Biophysical mechanisms responsible for pulsed low-level laser excitation of neural tissue

    NASA Astrophysics Data System (ADS)

    Wells, Jonathon; Kao, Chris; Konrad, Peter; Mahadevan-Jansen, Anita; Jansen, E. Duco

    2006-02-01

    Background/Objective: The traditional method of stimulating neural activity has been based on electrical methods and remains the gold standard to date despite inherent limitations. We have previously shown a new paradigm to in vivo neural activation based on pulsed infrared light, which provides a contact-free, spatially selective, artifact-free method without incurring tissue damage that may have significant advantages over electrical stimulation in a variety of diagnostic and therapeutic applications. The goal of this study was to investigate the physical mechanism of this phenomenon, which we propose is a photo-thermal effect from transient tissue temperature changes resulting in direct or indirect activation of transmembrane ion channels causing propagation of the action potential. Methods: Rat sciatic nerve preparation was stimulated in vivo with the Holmium:YAG laser (2.12μm), Free Electron Laser (2.1μm), Alexandrite laser (690nm), and the prototype for a solid state commercial laser nerve stimulator built by Aculight (1.87μm) to determine contributions of photobiological responses from laser tissue interactions, including temperature, pressure, electric field, and photochemistry, underlying the biophysical mechanism of stimulation. Single point temperature measurements were made with a microthermocouple adjacent to the excitation site, while an infrared camera was used for 2-D radiometry of the irradiated surface. Displacement from laser-induced pressure waves or thermoelastic expansion was measured using a PS-OCT system. Results: Results exclude a direct photochemical, electric field, or pressure wave effect as the mechanism of optical stimulation. Measurements show relative small contributions from thermoelastic expansion (300 nm) with the laser parameters used for nerve stimulation. The maximum change in tissue temperature is about 9°C (average increase of 3.66 °C) at stimulation threshold radiant exposures. Conclusion: Neural activation with pulsed

  20. Anomalous dispersion and the pumping of far infrared (FIR) lasers

    NASA Technical Reports Server (NTRS)

    Lawandy, N. M.

    1978-01-01

    It is shown that the anomalous dispersion at the pump transition in molecular far-infrared lasers (FIR) can lead to sizable focusing and defocusing effects. Criteria for beam spreading and trapping are considered with CH2F as an example.

  1. Laser-induced fluorescence of formaldehyde in combustion using third harmonic Nd:YAG laser excitation.

    PubMed

    Brackmann, Christian; Nygren, Jenny; Bai, Xiao; Li, Zhongshan; Bladh, Henrik; Axelsson, Boman; Denbratt, Ingemar; Koopmans, Lucien; Bengtsson, Per-Erik; Aldén, Marcus

    2003-12-01

    Formaldehyde (CH2O) is an important intermediate species in combustion processes and it can through laser-induced fluorescence measurements be used for instantaneous flame front detection. The present study has focussed on the use of the third harmonic of a Nd:YAG laser at 355 nm as excitation wavelength for formaldehyde, and different dimethyl ether (C2H6O) flames were used as sources of formaldehyde in the experiments. The investigations included studies of the overlap between the laser profile and the absorption lines of formaldehyde, saturation effects and the potential occurrence of laser-induced photochemistry. The technique was applied for detection of formaldehyde in an internal combustion engine operated both as a spark ignition engine and as a homogenous charge compression ignition engine.

  2. In vivo studies of ultrafast near-infrared laser tissue bonding and wound healing

    NASA Astrophysics Data System (ADS)

    Sriramoju, Vidyasagar; Alfano, Robert R.

    2015-10-01

    Femtosecond (fs) pulse lasers in the near-infrared (NIR) range exhibit very distinct properties upon their interaction with biomolecules compared to the corresponding continuous wave (CW) lasers. Ultrafast NIR laser tissue bonding (LTB) was used to fuse edges of two opposing animal tissue segments in vivo using fs laser photoexcitation of the native vibrations of chomophores. The fusion of the incised tissues was achieved in vivo at the molecular level as the result of the energy-matter interactions of NIR laser radiation with water and the structural proteins like collagen in the target tissues. Nonthermal vibrational excitation from the fs laser absorption by water and collagen induced the formation of cross-links between tissue proteins on either sides of the weld line resulting in tissue bonding. No extrinsic agents were used to facilitate tissue bonding in the fs LTB. These studies were pursued for the understanding and evaluation of the role of ultrafast NIR fs laser radiation in the LTB and consequent wound healing. The fs LTB can be used for difficult to suture structures such as blood vessels, nerves, gallbladder, liver, intestines, and other viscera. Ultrafast NIR LTB yields promising outcomes and benefits in terms of wound closure and wound healing under optimal conditions.

  3. Integrated all-optical infrared switchable plasmonic quantum cascade laser.

    PubMed

    Kohoutek, John; Bonakdar, Alireza; Gelfand, Ryan; Dey, Dibyendu; Nia, Iman Hassani; Fathipour, Vala; Memis, Omer Gokalp; Mohseni, Hooman

    2012-05-09

    We report a type of infrared switchable plasmonic quantum cascade laser, in which far field light in the midwave infrared (MWIR, 6.1 μm) is modulated by a near field interaction of light in the telecommunications wavelength (1.55 μm). To achieve this all-optical switch, we used cross-polarized bowtie antennas and a centrally located germanium nanoslab. The bowtie antenna squeezes the short wavelength light into the gap region, where the germanium is placed. The perturbation of refractive index of the germanium due to the free carrier absorption produced by short wavelength light changes the optical response of the antenna and the entire laser intensity at 6.1 μm significantly. This device shows a viable method to modulate the far field of a laser through a near field interaction.

  4. Near Infrared Laser Spectroscopy of Scandium Monobromide

    NASA Astrophysics Data System (ADS)

    Xia, Ye; Cheung, A. S.-C.; Liao, Zhenwu; Yang, Mei; Chan, Man-Chor

    2012-06-01

    High resolution laser spectrum of scandium monobromide (ScBr) between 787 and 845 nm has been investigated using the technique of laser vaporization/reaction with free jet expansion and laser induced fluorescence spectroscopy. ScBr was produced by reacting laser vaporized Sc atoms with ethyl bromide (C2H5Br). Spectra of six vibrational bands of both Sc79Br and Sc81Br isotopomers of the C1 Σ+ - X1 Σ+ transition and seven vibrational bands of the e3 Δ - a3 Δ transition were obtained and analyzed. Least-squares fit of the measured line positions for the singlet transitions yielded accurate molecular constants for the v = 0 - 3 levels of the C1 Σ+ state and the v = 0 - 2 levels of the X1 Σ+ state. Similar least-squares fit for the triplet transitions yielded molecular constants for the v = 0 - 2 levels of both e3 Δ and a3 Δ states. The equilibrium bond length, r_0, of the a3 Δ state has been determined to be 2.4789 Å. Financial support from the Research Grants Council of the Hong Kong Special Administrative Region, China (Project No. HKU 701008P) is gratefully acknowledged

  5. Mid-Infrared Quantum Dot Cascade Lasers

    DTIC Science & Technology

    2005-11-18

    temperature, high efficiency infared laser sources can open up new applications such as medical imaging, sensing, inspection, and security surveillance...devices could be useful for new surgery and medical spectroscopy techniques, as well as monitoring of chemical species and free space communication

  6. Laser control of molecular excitations in stochastic dissipative media.

    PubMed

    Tremblay, Jean Christophe

    2011-05-07

    In the present work, ideas for controlling photochemical reactions in dissipative environments using shaped laser pulses are presented. New time-local control algorithms for the stochastic Schrödinger equation are introduced and compared to their reduced density matrix analog. The numerical schemes rely on time-dependent targets for guiding the reaction along a preferred path. The methods are tested on the vibrational control of adsorbates at metallic surfaces and on the ultrafast electron dynamics in a strong dissipative medium. The selective excitation of the specific states is achieved with improved yield when using the new algorithms. Both methods exhibit similar convergence behavior and results compare well with those obtained using local optimal control for the reduced density matrix. The favorable scaling of the methods allows to tackle larger systems and to control photochemical reactions in dissipative media of molecules with many more degrees of freedom.

  7. Mid-infrared coronary laser angioplasty with multifiber catheters

    NASA Astrophysics Data System (ADS)

    White, Christopher J.; Ramee, Stephen R.; Collins, Tyrone J.

    1993-06-01

    Mid-infrared laser wavelengths offer advantages as a source for coronary angioplasty based upon the excellent fiberoptic transmission and the enhanced tissue absorption of these photons. We report the results of a pilot clinical trial of a Holmium:YAG (2.1 micrometers ) coronary laser angioplasty using a prototype (1.6 mm and 2.0 mm) multifiber catheters. Coronary laser angioplasty with or without adjunctive balloon angioplasty or directional atherectomy was performed in 14 patients with 17 coronary stenoses. Laser success was obtained in 13/14 (93%) patients and 16/17 (94%) lesions. Uncomplicated procedural success was achieved in 9/14 (64%) patients and 12/17 (71%) lesions. Our initial laser success rate was very encouraging using this prototype multifiber catheter with a holmium:YAG laser. However, our overall procedural success rate was disappointing, and not superior to that expected with conventional angioplasty alone. The holmium laser remains an attractive energy source for laser angioplasty, but its utility is limited by catheters which create inadequate channels for stand-alone laser angioplasty.

  8. Glass drilling by longitudinally excited CO2 laser with short laser pulse

    NASA Astrophysics Data System (ADS)

    Uno, Kazuyuki; Yamamoto, Takuya; Akitsu, Tetsuya; Jitsuno, Takahisa

    2015-03-01

    We developed a longitudinally excited CO2 laser that produces a short laser pulse. The laser was very simple and consisted of a 45-cm-long alumina ceramic pipe with an inner diameter of 9 mm, a pulse power supply, a step-up transformer, a storage capacitance, and a spark-gap switch. The laser pulse had a spike pulse and a pulse tail. The energy of the pulse tail was controlled by adjusting medium gas. Using three types of CO2 laser pulse with the same spike-pulse energy and the different pulse-tail energy, the characteristics of the hole drilling of synthetic silica glass was investigated. Higher pulse-tail energy gave deeper ablation depth. In the short laser pulse with the spike-pulse energy of 1.2 mJ, the spike pulse width of 162 ns, the pulse-tail energy of 24.6 mJ, and the pulse-tail length of 29.6 μs, 1000 shots irradiation produced the ablation depth of 988 μm. In the hole drilling of synthetic silica glass by the CO2 laser, a crack-free process was realized.

  9. The design of infrared laser radar for vehicle initiative safety

    NASA Astrophysics Data System (ADS)

    Gong, Ping; Xu, Xi-ping; Li, Xiao-yu; Li, Tian-zhi; Liu, Yu-long; Wu, Jia-hui

    2013-09-01

    Laser radar for vehicle is mainly used in advanced vehicle on-board active safety systems, such as forward anti-collision systems, active collision warning systems and adaptive cruise control systems, etc. Laser radar for vehicle plays an important role in the improvement of vehicle active safety and the reduction of traffic accidents. The stability of vehicle active anti-collision system in dynamic environment is still one of the most difficult problems to break through nowadays. According to people's driving habit and the existed detecting technique of sensor, combining the infrared laser range and galvanometer scanning technique , design a 3-D infrared laser radar which can be used to assist navigation, obstacle avoidance and the vehicle's speed control for the vehicle initiative safety. The device is fixed to the head of vehicle. Then if an accident happened, the device could give an alarm to remind the driver timely to decelerate or brake down, by which way can people get the purpose of preventing the collision accidents effectively. To accomplish the design, first of all, select the core components. Then apply Zemax to design the transmitting and receiving optical system. Adopt 1550 nm infrared laser transmitter as emission unit in the device, a galvanometer scanning as laser scanning unit and an InGaAs-APD detector as laser echo signal receiving unit. Perform the construction of experimental system using FPGA and ARM as the core controller. The system designed in this paper can not only detect obstacle in front of the vehicle and make the control subsystem to execute command, but also transfer laser data to PC in real time. Lots of experiments using the infrared laser radar prototype are made, and main performance of it is under tested. The results of these experiments show that the imaging speed of the laser radar can reach up to 25 frames per second, the frame resolution of each image can reach 30×30 pixels, the horizontal angle resolution is about 6. 98

  10. How Plasmonic excitation influences the LIPSS formation on diamond during multipulse femtosecond laser irradiation ?

    NASA Astrophysics Data System (ADS)

    Abdelmalek, Ahmed; Bedrane, Zeyneb; Amara, El-Hachemi; Eaton, Shane M.; Ramponi, Roberta

    2017-03-01

    A generalized plasmonic model is proposed to calculate the nanostructure period induced by multipulse laser femtosecond on diamond at 800 nm wavelengths. We follow the evolution of LIPSS formation by changing diamond optical parameters in function of electron plasma excitation during laser irradiation. Our calculations shows that the ordered nanostructures can be observed only in the range of surface plasmon polariton excitation.

  11. Excited singlet-state absorption in laser dyes at the XeCl wavelength

    NASA Astrophysics Data System (ADS)

    Taylor, R. S.; Mihailov, S.

    1985-10-01

    The transmission properties of the laser dyes BBQ, PBD, BPBD, α-NPO, p-Quarterphenyl and PPO have been measured using a XeCl (308 nm) excimer laser. A model for the dye saturation which incorporates excited-state absorption was used to estimate the lifetime and the absorption cross section of the first excited singlet-state for each dye.

  12. Femtosecond laser electronic excitation tagging for aerodynamic and thermodynamic measurements

    NASA Astrophysics Data System (ADS)

    Calvert, Nathan David

    This thesis presents applications of Femtosecond Laser Electronic Excitation Tagging (FLEET) to a variety of aerodynamic and thermodynamic measurements. FLEET tagged line characteristics such as intensity, width and spectral features are investigated in various flow conditions (pressure, temperature, velocity, steadiness, etc.) and environments (gas composition) for both temporally and spatially instantaneous and averaged data. Special attention is drawn to the nature of first and second positive systems of molecular nitrogen and the ramifications on FLEET measurements. Existing laser-based diagnostic techniques are summarized and FLEET is directly compared with Particle Image Velocimetry (PIV) in various low speed flows. Multidimensional velocity, acceleration, vorticity and other flow parameters are extracted in supersonic free jets and within an enclosed in-draft tunnel test section. Probability distribution functions of the mean and standard deviation of critical flow parameters are unveiled by utilizing a Bayesian statistical framework wherein likelihood functions are established from prior and posterior distributions. Advanced image processing techniques based on fuzzy logic are applied to single-shot FLEET images with low signal-to-noise ratio to improve image quality and reduce uncertainty in data processing algorithms. Lastly, FLEET second positive and first negative emission are considered at a wide range of pressures to correct for changes in select rovibrational peak magnitude and shape due to density from which bulk gas temperature may be extracted.

  13. Decay Processes of Highly Excited Laser Ions in Solids.

    NASA Astrophysics Data System (ADS)

    Collins, John Michael

    Using the techniques of luminescence spectroscopy, we have investigated the luminescent properties of a number of systems following excitation with high-energy UV radiation. After revisiting the two-photon emission from Pr^{3+} in yttrium fluoride, an investigation into the possibility of energy transfer between Pr and other rare-earth ions was carried out in the systems YF_3:Pr,Tb; YF _3:Pr,Eu; LaF_3:Pr,Tb; and LaF_3:Pr,Eu. In all systems, spectroscopic and kinetic data shows no presence of energy transfer among the dopant ions. Investigation of the Pr -Eu doped systems were hindered by the presence of divalent Eu. The cross-relaxation process among Tb ions has been studied in Y_{rm 1-x} F_3:Tb_{ rm x}, with x =.001,.004 and.05, and is shown to increase with both concentration and temperature. Kinetic studies show that at high Tb concentration, the excitation migrates through the Tb sublattice at the ^5 D_3<=vel before the cross -relaxation can occur. The migration is quenched at low temperatures. Al_2O_3 :Ti, when excited with UV radiation shows the existence of as many as three previously unreported emissions. One of these bands, centered at 560 nm and extending throughout the visible region, was studied in more detail. The decay of this emission varies from 30 musec at 300^circK to 710 musec at 20^circK, while intensity actually decreases with temperature. A model is proposed which could explain this behavior. Laser action is also reported from this band and its application as a solid-state tunable laser is discussed. A previously unreported energy transfer from Gd ^{3+} to Er^ {3+} is shown to exist in the system Y _{.34}Gd_ {.65}Er_{.01} F_3. The energy transfer process is of the non-radiative type, and is quite efficient (~80%) in this system. Kinetic studies indicate that the transfer is more efficient at lower temperatures. This behavior is explained by a redistribution with temperature of the population of Gd and Er ions and its affect on the energy

  14. Ultrafast Nonlinear Excitation Dynamics of Black Phosphorus Nanosheets from Visible to Mid-Infrared.

    PubMed

    Wang, Kangpeng; Szydłowska, Beata M; Wang, Gaozhong; Zhang, Xiaoyan; Wang, Jing Jing; Magan, John J; Zhang, Long; Coleman, Jonathan N; Wang, Jun; Blau, Werner J

    2016-07-26

    The recent progress on black phosphorus makes it a promising candidate material for broadband nanophotonic devices, especially operating in the mid-infrared spectral region. Here, the excited carrier dynamics and nonlinear optical response of unoxidized black phosphorus nanosheets and their wavelength dependence were systematically studied from 800 nm to 2.1 μm. The wavelength-dependent relaxation times of black phosphorus nanosheets are determined to be 360 fs to 1.36 ps with photon energies from 1.55 to 0.61 eV. In a comparative study with graphene, we found that black phosphorus has a faster carrier relaxation in near- and mid-infrared region. With regard to nonlinear optical absorption, the response of black phosphorus significantly increases from near- to mid-infrared, and black phosphorus is also confirmed to be better as saturable absorber to MoS2 in infrared region.

  15. Thermal imaging method to visualize a hidden painting thermally excited by far infrared radiations

    NASA Astrophysics Data System (ADS)

    Davin, T.; Wang, X.; Chabane, A.; Pawelko, R.; Guida, G.; Serio, B.; Hervé, P.

    2015-06-01

    The diagnosis of hidden painting is a major issue for cultural heritage. In this paper, a non-destructive active infrared thermographic technique was considered to reveal paintings covered by a lime layer. An extended infrared spectral range radiation was used as the excitation source. The external long wave infrared energy source delivered to the surface is then propagated through the material until it encounters a painting zone. Due to several thermal effects, the sample surface then presents non-uniformity patterns. Using a high sensitive infrared camera, the presence of covered pigments can thus be highlighted by the analysis of the non-stationary phenomena. Reconstituted thermal contrast images of mural samples covered by a lime layer are shown.

  16. Ablation mechanisms of calcium carbonate under visible and infrared laser irradiation

    NASA Astrophysics Data System (ADS)

    Park, Hee K.; Haglund, Richard F., Jr.

    1997-05-01

    Calcium carbonate (CaCO3) and its structural relatives, the phosphates and hydroxyapatites, are natural crystals which are similar to the minerals found in such hard tissues as teeth and bone. We have recently demonstrated that laser- induced material removal in calcium carbonate occurs with high efficiency when irradiating with a free-electron laser at the fundamental asymmetric stretch mode of the carbonate group near 7 micrometers ; related studies show that the same thing is true in the isoelectronic sodium nitrate, and we expect it to operate in the phosphates as well when irradiated near the resonant 9 micrometers band. The mechanism of material removal appears to be the ejection of CO followed by a calcination reaction which produces CaO. Among the features which make CaCO3 such an interesting model material is that it also has a characteristic, temperature-dependent thermoluminescence - thus making it possible, by the study of the light emitted by the crystal prior to and after ablation, to estimate the temperature reached by the crystal in the early stages of laser ablation. Wavelength-dependent photoluminescence, photoacoustic and plume-spectroscopic studies show that efficient evaporative 'hole drilling' occurs at the infrared wavelengths corresponding to carbonate or nitrate vibration modes. However, where electronic or vibrational defects are excited by visible or infrared lasers, respectively, the mechanisms of material removal are photomechanical fracture in the former case and exfoliation or subsurface explosive vaporization in the latter.

  17. Atmospheric Laser and Infrared Transmission Model

    DTIC Science & Technology

    2009-01-01

    simplicity, we maintain separate ALIRT models for 1.3152 μ wavelength iodine and 1.060 μ wavelength neodym - ium/glass lasers. In Chapter 2, we describe...U t is either of E t or H t . With those assumptions, Equations A-1 imply that both electric and magnetic fields are solenoidal and that HiE rr...field that we are considering, the Poynting vector will point along the x3-axis, and the magnetic field, like the electric field, will be perpendicular

  18. Lasing studies of new coumarin derivatives under laser and lamp excitation

    SciTech Connect

    Aristov, A. V.; Veselova, T. V.; Kozlovskii, D. A.; Komlev, I. V.; Levin, M. B.; Reznichenko, A. V.; Tavrizova, M. A.; Cherkasov, A. S.

    1988-09-01

    The luminescence characteristics and results of a study of the comparative laser efficiency of ethanol solutions of a series of coumarin derivatives and rhodamine 6G are presented. It is shown that under laser excitation (neodymium laser third harmonic) and lamp excitation, the solutions of certain coumarins match rhodamine 6G in lasing efficiency values. A comparatively low photostability of the investigated coumarin solutions and its weak dependence on the spectral composition of the pumping radiation have been observed.

  19. Research on fission fragment excitation of gases and nuclear pumping of lasers

    NASA Technical Reports Server (NTRS)

    Schneider, R. T.; Davie, R. N.; Davis, J. F.; Fuller, J. L.; Paternoster, R. R.; Shipman, G. R.; Sterritt, D. E.; Helmick, H. H.

    1974-01-01

    Experimental investigations of fission fragment excited gases are reported along with a theoretical analysis of population inversions in fission fragment excited helium. Other studies reported include: nuclear augmentation of gas lasers, direct nuclear pumping of a helium-xenon laser, measurements of a repetitively pulsed high-power CO2 laser, thermodynamic properties of UF6 and UF6/He mixtures, and nuclear waste disposal utilizing a gaseous core reactor.

  20. Non-infrared femtosecond lasers: status and prospects

    NASA Astrophysics Data System (ADS)

    Kahmann, Max; Gebs, Raphael; Fleischhaker, Robert; Zawischa, Ivo; Kleinbauer, Jochen; Russ, Simone; Bauer, Lara; Keller, Uwe; Faisst, Birgit; Budnicki, Aleksander; Sutter, Dirk

    2016-03-01

    The unique properties of ultrafast laser pulses pave the way to numerous novel applications. Particularly lasers in the sub-pico second regime, i.e. femtosecond lasers, in the last decade arrived at a level of reliability suitable for the industrial environment and now gain an increasing recognition since these pulse durations combine the advantages of precise ablation with higher efficiency especially in the case of processing metallic materials. However, for some micro processing applications the infrared wavelength of these lasers is still a limiting factor. Thus, to further broaden the range of possible applications, industrial femtosecond lasers should combine the advantages of femtosecond pulses and shorter wavelengths. To that extend, we present results obtained with a frequency doubled TruMicro 5000 FemtoEdition. We show that depending on the processed material, the higher photon energy as well as tighter focusing options of the shorter wavelength can open up a new regime of processing parameters. This regime is not accessible by infrared light, leading to a wider range of possible applications.

  1. Infrared laser ablation sample transfer for MALDI imaging.

    PubMed

    Park, Sung-Gun; Murray, Kermit K

    2012-04-03

    An infrared laser was used to ablate material from tissue sections under ambient conditions for direct collection on a matrix assisted laser desorption ionization (MALDI) target. A 10 μm thick tissue sample was placed on a microscope slide and was mounted tissue-side down between 70 and 450 μm from a second microscope slide. The two slides were mounted on a translation stage, and the tissue was scanned in two dimensions under a focused mid-infrared (IR) laser beam to transfer material to the target slide via ablation. After the material was transferred to the target slide, it was analyzed using MALDI imaging using a tandem time-of-flight mass spectrometer. Images were obtained from peptide standards for initial optimization of the system and from mouse brain tissue sections using deposition either onto a matrix precoated target or with matrix addition after sample transfer and compared with those from standard MALDI mass spectrometry imaging. The spatial resolution of the transferred material is approximately 400 μm. Laser ablation sample transfer provides several new capabilities not possible with conventional MALDI imaging including (1) ambient sampling for MALDI imaging, (2) area to spot concentration of ablated material, (3) collection of material for multiple imaging analyses, and (4) direct collection onto nanostructure assisted laser desorption ionization (NALDI) targets without blotting or ultrathin sections.

  2. Infrared Laser System for Extended Area Monitoring of Air Pollution

    NASA Technical Reports Server (NTRS)

    Snowman, L. R.; Gillmeister, R. J.

    1971-01-01

    An atmospheric pollution monitoring system using a spectrally scanning laser has been developed by the General Electric Company. This paper will report on an evaluation of a breadboard model, and will discuss applications of the concept to various ambient air monitoring situations. The system is adaptable to other tunable lasers. Operating in the middle infrared region, the system uses retroreflectors to measure average concentrations over long paths at low, safe power levels. The concept shows promise of meeting operational needs in ambient air monitoring and providing new data for atmospheric research.

  3. On the nature of excited states of photosynthetic reaction centers: An ultrafast infrared study

    SciTech Connect

    Haran, G.; Wynne, K.; Reid, G.D.

    1995-12-31

    Bacterial photosynthetic reaction centers (RC) contain eight chromophores forming a well-defined supramolecular structure within a protein framework. Theoretical studies suggest that the excited states of these chromophores are delocalized and contain important contributions from charge-transfer and resonance states. There is no clear-cut experimental evidence pertaining to the degree of localization of excited states. We have used ultrafast near and mid-infrared spectroscopic methods to investigate the character of some of the excited states. Exciting the 800 nm, absorption band, we followed the fate of the excitation energy using either the stimulated emission of the special pair at 920 nm or a transient absorption at 1.2 {mu}m. For a completely localized system, Forster theory-based calculations are expected to accurately predict the kinetics of energy transfer. It was found, however, that calculated rates arc much faster than measured rates. This corroborates a delocalized picture, with internal conversion rather than energy transfer between states. We have also measured the transient absorption spectrum of the RC in the infrared spectral region, detecting several new low-lying electronic states. Assignments for these states, and implications for the localization problem will be discussed.

  4. Longitudinally excited CO2 laser with short laser pulse operating at high repetition rate

    NASA Astrophysics Data System (ADS)

    Li, Jianhui; Uno, Kazuyuki; Akitsu, Tetsuya; Jitsuno, Takahisa

    2016-11-01

    A short-pulse longitudinally excited CO2 laser operating at a high repetition rate was developed. The discharge tube was made of a 45 cm-long or 60 cm-long dielectric tube with an inner diameter of 16 mm and two metallic electrodes at the ends of the tube. The optical cavity was formed by a ZnSe output coupler with a reflectivity of 85% and a high-reflection mirror. Mixed gas (CO2:N2:He = 1:1:2) was flowed into the discharge tube. A high voltage of about 33 kV with a rise time of about 200 ns was applied to the discharge tube. At a repetition rate of 300 Hz and a gas pressure of 3.4 kPa, the 45 cm-long discharge tube produced a short laser pulse with a laser pulse energy of 17.5 mJ, a spike pulse energy of 0.2 mJ, a spike width of 153 ns, and a pulse tail length of 90 μs. The output power was 5.3 W. The laser pulse waveform did not depend on the repetition rate, but the laser beam profile did. At a low repetition rate of less than 50 Hz, the laser beam had a doughnut-like shape. However, at a high repetition rate of more than 150 Hz, the discharge concentrated at the center of the discharge tube, and the intensity at the center of the laser beam was higher. The laser beam profile depended on the distribution of the discharge. An output power of 7.0 W was achieved by using the 60 cm-long tube.

  5. Infrared Laser Optoacoustic Detection Of Gases And Vapours

    NASA Astrophysics Data System (ADS)

    Johnson, S. A.; Cummins, P. G.; Bone, S. A.; Davies, P. B.

    1988-10-01

    Mid-infrared laser optoacoustic spectroscopy has been used to detect a variety of gases and vapours. Performance was calibrated using the signal from a known concentration of ethene, and then the method applied to the perfume alcohol geraniol. Detection limits were found to be 1 ppb for ethene and 70 ppb for geraniol on their strongest absorption lines for a few seconds measurement time.

  6. Origin of near to middle infrared luminescence and energy transfer process of Er(3+)/Yb(3+)co-doped fluorotellurite glasses under different excitations.

    PubMed

    Huang, Feifei; Liu, Xueqiang; Ma, Yaoyao; Kang, Shuai; Hu, Lili; Chen, Danping

    2015-02-04

    We report the near to middle infrared luminescence and energy transfer process of Er(3+)/Yb(3+) co-doped fluorotellurite glasses under 980, 1550 and 800 nm excitations, respectively. Using a 980 nm laser diode pump, enhanced 1.5 and 2.7 μm emissions from Er(3+):I13/2→(4)I15/2 and I11/2→(4)I13/2 transitions are observed, in which Yb(3+) ions can increase pumping efficiency and be used as energy transfer donors. Meanwhile, Yb(3+) can also be used as an acceptor and intensive upconversion luminescence of around 1000 nm is achieved from Er(3+):I11/2→(4)I15/2 and Yb(3+): F5/2→(4)F7/2 transitions using 1550 nm excitation. In addition, the luminescence properties and variation trendency by 800 nm excitation is similar to that using 1550 nm excitation. The optimum Er(3+) and Yb(3+) ion ratio is 1:1.5 and excess Yb(3+) ions decrease energy transfer efficiency under the two pumpings. These results indicate that Er(3+)/Yb(3+) co-doped fluorotellurite glasses are potential middle- infrared laser materials and may be used to increase the efficiency of the silicon solar cells.

  7. FAST TRACK COMMUNICATION: Selective inactivation of micro-organisms with near-infrared femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Tsen, K. T.; Tsen, Shaw-Wei D.; Sankey, Otto F.; Kiang, Juliann G.

    2007-11-01

    We demonstrate an unconventional and revolutionary method for selective inactivation of micro-organisms by using near-infrared femtosecond laser pulses. We show that if the wavelength and pulse width of the excitation femtosecond laser are appropriately selected, there exists a window in power density that enables us to achieve selective inactivation of target viruses and bacteria without causing cytotoxicity in mammalian cells. This strategy targets the mechanical (vibrational) properties of micro-organisms, and thus its antimicrobial efficacy is likely unaffected by genetic mutation in the micro-organisms. Such a method may be effective against a wide variety of drug resistant micro-organisms and has broad implications in disinfection as well as in the development of novel treatments for viral and bacterial pathogens.

  8. Accurate frequency of the 119 micron methanol laser from tunable far-infrared absorption spectroscopy

    NASA Technical Reports Server (NTRS)

    Inguscio, M.; Zink, L. R.; Evenson, K. M.; Jennings, D. A.

    1990-01-01

    High-accuracy absorption spectroscopy of CH3OH in the far infrared is discussed. In addition to 22 transitions in the ground state, the frequency of the (n, tau, J, K), (0, 1, 16, 8) to (0, 2, 15, 7) transition in the nu5 excited vibrational level, which is responsible for the laser emission at 119 microns, was measured. The measured frequency is 2,522,782.57(10) MHz at zero pressure, with a pressure shift of 6.1(32) kHz/Pa (0.805/420/ MHz/torr). An accurate remeasurement of the laser emission frequency has also been performed, and the results are in good agreement.

  9. Livermore experience: contributions of J. H. Eberly to laser excitation theory

    SciTech Connect

    Shore, B W; Kulander, K; Davis, J I

    2000-10-12

    This article summarizes the developing understanding of coherent atomic excitation, as gained through a collaboration of J. H. Eberly with the Laser Isotope Separation Program of the Lawrence Livermore National Laboratory, particularly aspects of coherence, population trapping, multilevel multiphoton excitation sequences, analytic solutions to multistate excitation chains, the quasicontinuum, pulse propagation, and noise. In addition to the discovery of several curious and unexpected properties of coherent excitation, mentioned here, the collaboration provided an excellent example of unexpected benefits from investment into basic research.

  10. Nanowires-assisted excitation and propagation of mid-infrared surface plasmon polaritons in graphene

    NASA Astrophysics Data System (ADS)

    Lu, Hua; Zhao, Jianlin; Gu, Min

    2016-10-01

    We investigate the excitation and propagation of surface plasmon polaritons in a novel graphene hybrid photonic nanostructure, which consists of a graphene sheet and a dielectric layer with partly etched nanowires coated on the silicon substrate. The simulation and analytical results show that the mid-infrared plasmonic wave can be generated in the graphene sheet by normally incident light due to the satisfaction of the wavevector matching condition. Especially, we find that the plasmonic wavelength and spectral width are determined by the width, pitch, and refractive index of the dielectric nanowires, as well as the layer number and the Fermi level of graphene sheet. The analytical calculations agree well with the finite-difference time-domain simulations. These results would provide an new avenue toward the excitation of graphene plasmonics for the manipulation of mid-infrared light at nanoscale.

  11. Resonant infrared pulsed laser deposition of cyclic olefin copolymer films

    NASA Astrophysics Data System (ADS)

    Singaravelu, S.; Klopf, J. M.; Schriver, K. E.; Park, H. K.; Kelley, M. J.; Haglund, R. F.

    2014-03-01

    Barrier materials on thin-film organic optoelectronic devices inhibit the uptake of water, oxygen, or environmental contaminants, and fabricating them is a major challenge. By definition, these barrier layers must be insoluble, so the usual routes to polymer- or organic-film deposition by spin coating are not problematic. In this paper, we report comparative studies of pulsed laser deposition of cyclic olefin copolymer (COC), an excellent moisture barrier and a model system for a larger class of protective materials that are potentially useful in organic electronic devices, such as organic light-emitting diodes (OLEDs). Thin films of COC were deposited by resonant and nonresonant infrared pulsed laser ablation of solid COC targets, using a free-electron laser tuned to the 3.43 μm C-H stretch of the COC, and a high-intensity nanosecond Q-switched laser operated at 1064 nm. The ablation craters and deposited films were characterized by scanning-electron microscopy, Fourier-transform infrared spectrometry, atomic-force microscopy, high-resolution optical microscopy, and surface profilometry. Thermal-diffusion calculations were performed to determine the temperature rise induced in the film at the C-H resonant wavelength. The results show that resonant infrared pulsed laser deposition (RIR-PLD) is an effective, low-temperature thin-film deposition technique that leads to evaporation and deposition of intact molecules in homogeneous, smooth films. Nonresonant PLD, on the other hand, leads to photothermal damage, degradation of the COC polymers, and to the deposition only of particulates.

  12. Monolithically Integrated Mid-Infrared Quantum Cascade Laser and Detector

    PubMed Central

    Schwarz, Benedikt; Reininger, Peter; Detz, Hermann; Zederbauer, Tobias; Andrews, Aaron Maxwell; Schrenk, Werner; Strasser, Gottfried

    2013-01-01

    We demonstrate the monolithic integration of a mid-infrared laser and detector utilizing a bi-functional quantum cascade active region. When biased, this active region provides optical gain, while it can be used as a detector at zero bias. With our novel approach we can measure the light intensity of the laser on the same chip without the need of external lenses or detectors. Based on a bound-to-continuum design, the bi-functional active region has an inherent broad electro-luminescence spectrum of 200 cm−1, which indicate sits use for single mode laser arrays. We have measured a peak signal of 191.5 mV at theon-chip detector, without any amplification. The room-temperature pulsed emission with an averaged power consumption of 4 mW and the high-speed detection makes these devices ideal for low-power sensors. The combination of the on-chip detection functionality, the broad emission spectrum and the low average power consumption indicates the potential of our bi-functional quantum cascade structures to build a mid-infrared lab-on-a-chip based on quantum cascade laser technology. PMID:23389348

  13. Infrared laser-assisted desorption electrospray ionization mass spectrometry.

    PubMed

    Rezenom, Yohannes H; Dong, Jianan; Murray, Kermit K

    2008-02-01

    We have used an infrared laser for desorption of material and ionization by interaction with electrosprayed solvent. Infrared laser-assisted desorption electrospray ionization (IR LADESI) mass spectrometry was used for the direct analysis of water-containing samples under ambient conditions. An ion trap mass spectrometer was modified to include a pulsed Er:YAG laser at 2.94 microm wavelength coupled into a germanium oxide optical fiber for desorption at atmospheric pressure and a nanoelectrospray source for ionization. Analytes in aqueous solution were placed on a stainless steel target and irradiated with the pulsed IR laser. Material desorbed and ablated from the target was ionized by a continuous stream of charged droplets from the electrosprayed solvent. Peptide and protein samples analyzed using this method yield mass spectra similar to those obtained by conventional electrospray. Blood and urine were analyzed without sample pretreatment to demonstrate the capability of IR LADESI for direct analysis of biological fluids. Pharmaceutical products were also directly analyzed. Finally, the role of water as a matrix in the IR LADESI process is discussed.

  14. Laser Welding of Copper Using Multi Mode Fiber Lasers at Near Infrared Wavelength

    NASA Astrophysics Data System (ADS)

    Liebl, S.; Wiedenmann, R.; Ganser, A.; Schmitz, P.; Zaeh, M. F.

    Due to the increasing electrification of automotive drives and the expansion of decentralized renewable energygeneration, the consumption of copper for the fabrication of electrical components such as electric motors or conducting paths increases. To jointhese components, laser welding is more frequently used since it represents a flexible and fully automatable joining process. Because of the high thermal conductivity, the low absorption coefficient forinfrared wavelength of common laser beam sources and the resulting limited process efficiency, welding of copper alloys represents a major challenge for laser assisted processes. In this paper, experimental investigationsare presented to identify arising process limits during laser welding of pure copper materials with multi-mode fiber lasers at near infrared wavelength depending on the applied laser power and welding velocity. In addition, a potential stabilization of the welding process by shielding gas support was examined. Further investigations were focused on the influence of shielding gas on the molten pool geometry.

  15. Design and fabrication of visible and infrared laser HR coating

    NASA Astrophysics Data System (ADS)

    Li, Meixuan; Dong, Lianhe; Zhang, Lei; Wu, Boqi; Ma, Jun

    2014-08-01

    In view of the special requirements of the high power laser spectral bands and the incident angle, plate dual wavelength laser high reflecting membrane on the K9 optical glass by using electron beam evaporation deposition. Under the condition of vertical incidence, the reflectivity of 532 nm wavelength is higher than 90%; Under the condition of plus or minus 45 ° incident angle, the reflectivity of 1064 nm wavelength at near infrared band is higher than 99.9%. Through material selection, optimization of process parameters and the method of the ion source assisted deposition to improve the membrane layer density and membrane base binding strength, laser-damaged threshold and meet the requirements of the use of optical instruments under certain environmental conditions.

  16. Dentin mid-infrared laser ablation at various lasing parameters

    NASA Astrophysics Data System (ADS)

    Papadopoulos, Dimitris N.; Papagiakoumou, Eirini I.; Makropoulou, Mersini I.; Khabbaz, Marouan G.; Serafetinides, Alexander A.

    2005-01-01

    In this study a frustrated total internal reflection (FTIR) Q-switched and free-running Er:YAG laser, as well as a novel design transversally excited atmospheric pressure (TEA) oscillator-double amplifier corona preionised high beam quality Hydrogen-Fluoride (HF) laser system, all developed in our lab, were used in dentin ablation experiments. In the case of the Er:YAG laser, pulses of 190 ns in Q-switched operation and of 80 μs pulse width in free-running operation at 2.94 μm were used, while HF laser pulses of 39 ns in the wavelength range of 2.6-3.1 μm in a predominantly TEM00 beam were also used to interact in vitro with dentin tissue. Several samples of freshly extracted human teeth were used, cut longitudinally in facets of 0.4-1.5 mm thick. Ablation experiments were conducted with the laser beam directly focused on the tissue or after being waveguided through suitable mid-IR fiber/waveguide alternatively ended with quartz end-sealing caps. The correlation between the various laser beam parameters, as wavelength, pulse duration, repetition rate, energy and spatial distribution of the beam profile and the ablative characteristics (ablation rates, tissue surface morphology) of dentin surface were investigated.

  17. Eye-safe infrared laser-induced breakdown spectroscopy (LIBS) emissions from energetic materials

    NASA Astrophysics Data System (ADS)

    Brown, Ei E.; Hömmerich, Uwe; Yang, Clayton C.; Jin, Feng; Trivedi, Sudhir B.; Samuels, Alan C.

    2016-05-01

    Laser-induced breakdown spectroscopy is a powerful diagnostic tool for detection of trace elements by monitoring the atomic and ionic emission from laser-induced plasmas. Besides elemental emissions from conventional UV-Vis LIBS, molecular LIBS emission signatures of the target compounds were observed in the long-wave infrared (LWIR) region in recent studies. Most current LIBS studies employ the fundamental Nd:YAG laser output at 1.064 μm, which has extremely low eye-damage threshold. In this work, comparative LWIR-LIBS emissions studies using traditional 1.064 μm pumping and eye-safe laser wavelength at 1.574 μm were performed on several energetic materials for applications in chemical, biological, and explosive (CBE) sensing. A Q-switched Nd: YAG laser operating at 1.064 μm and the 1.574 μm output of a pulsed Nd:YAG pumped Optical Parametric Oscillator were employed as the excitation sources. The investigated energetic materials were studied for the appearance of LWIR-LIBS emissions (4-12 μm) that are directly indicative of oxygenated breakdown products as well as partially dissociated and recombination molecular species. The observed molecular IR LIBS emission bands showed strong correlation with FTIR absorption spectra of the studied materials for 1.064 μm and 1.574 μm pump wavelengths.

  18. Laser Infrared Desorption Spectroscopy to Detect Complex Organic Molecules on Icy Planetary Surfaces

    NASA Technical Reports Server (NTRS)

    Sollit, Luke S.; Beegle, Luther W.

    2008-01-01

    Laser Desorption-Infrared Spectroscopy (LD-IR) uses an IR laser pulse to desorb surface materials while a spectrometer measures the emission spectrum of the desorbed materials (Figure 1). In this example, laser desorption operates by having the incident laser energy absorbed by near surface material (10 microns in depth). This desorption produces a plume that exists in an excited state at elevated temperatures. A natural analog for this phenomenon can be observed when comets approach the sun and become active and individual molecular emission spectra can be observed in the IR [1,2,3,4,5]. When this occurs in comets, the same species that initially emit radiation down to the ground state are free to absorb it, reducing the amount of detectable emission features. The nature of our technique results in absorption not occurring, because the laser pulse could easily be moved away form the initial desorption plume, and still have better spatial resolution then reflectance spectroscopy. In reflectance spectroscopy, trace components have a relatively weak signal when compared to the entire active nature of the surface. With LDIR, the emission spectrum is used to identify and analyze surface materials.

  19. Rapidly tuning miniature transversely excited atmospheric-pressure CO2 laser.

    PubMed

    Qu, Yanchen; Ren, Deming; Hu, Xiaoyong; Liu, Fengmei; Zhao, Jingshan

    2002-08-20

    An experimental study of a rapidly tuning miniature transversely excited atmospheric-pressure CO2 laser is reported. To rapidly shift laser wavelengths over selected transitions in the 9-11 microm wavelength region, we have utilized a high-frequency stepping motor and a diffraction grating. The laser is highly automated with a monolithic microprocessor controlled laser line selection. For the achievement of stable laser output, a system of laser excitation with a voltage of 10 kV, providing effective surface corona preionization and allowing one to work at various gas pressures, is utilized. Laser operation at 59 emission lines of the CO2 molecule rotational transition is obtained and at 51 lines, the pulse energy of laser radiation exceeds 30 mJ. The system can be tuned between two different rotational lines spanning the wavelength range from 9.2 to 10.8 microm within 10 ms.

  20. Near-infrared excited surface-enhanced Raman spectroscopy of rhodamine 6G on colloidal silver

    NASA Astrophysics Data System (ADS)

    Kneipp, K.; Roth, E.; Engert, C.; Kiefer, W.

    1993-05-01

    1064 nm excited surface-enhanced Raman spectroscopy (SERS) of rhodamine 6G (Rh 6G) on NaCl-activated silver sol is reported performed with a scanning Raman spectrometer. The present study gives the opportunity to compare directly the enhancement factors for excitation in the near-infrared (NIR) and in the visible region and shows that for the case of Rh 6G these factors are of the same order of magnitude. This result can be explained by a growing electromagnetic contribution to the enhancement at 1064 nm which compensates the loss of resonance Raman enhancement by the change of excitation wavelength from about 500 to 1064 nm. An additional enhancement factor ascribed to the local mechanism of a Rh 6G-adatom—anion surface complex gives an essential contribution to SERS. This specific enhancement due to Cl-activated sites results in similar contributions in the visible and in the NIR.

  1. A novel laser angioplasty guided hollow fiber using mid-infrared laser

    NASA Astrophysics Data System (ADS)

    Yoshihashi-Suzuki, Sachiko; Yamada, Shinya; Sato, Izuru; Awazu, Kunio

    2006-02-01

    We have proposed selective removal of cholesterol ester by infrared laser of wavelength with 5.75 μm irradiation; the wavelength of 5.75 μm correspond with the ester bond C=O stretching vibration. The flexible laser guiding line and a compact light source are required for our proposal. We used a compact mid-infrared tunable laser by difference frequency generation; DFG laser was developed for substitute light source of free electron laser. In the present work, first, we have developed hollow optical fiber with a diamond lens-tip to deliver DFG laser in the blood vessel and evaluated the transmission of DFG laser from 5.5 μm to 7.5 μm. The transmission of 5.75 μm is about 65%, the DFG beam was focused on the tip of fiber by diamond lens-tip. Secondly, we performed the selective removal experiment of cholesterol ester using the hollow optical fiber with diamond lens-tip and DFG laser. The sample used a two layer model, cholesterol oleate and gelatin. The cholesterol oleate was decomposed by 5.75 μm DFG irradiation with 3.8 W/cm2.

  2. Radiative processes in air excited by an ArF laser

    NASA Technical Reports Server (NTRS)

    Laufer, Gabriel; Mckenzie, Robert L.; Huo, Winifred M.

    1988-01-01

    The emission spectrum of air that is excited by an ArF laser has been investigated experimentally and theoretically to determine the conditions under which fluorescence from O2 can be used for the measurement of temperature in aerodynamic flows. In addition to the expected fluorescence from O2, the spectrum from excitation with an intense laser beam is shown to contain significant contributions from the near-resonant Raman fundamental and overtone bands, the four-photon fluorescence excitation of C produced from ambient CO2, and possibly the three-photon excitation of O(2+). The nature of the radiative interactions contributing to these additional features is described.

  3. Highlighting the DNA damage response with ultrashort laser pulses in the near infrared and kinetic modeling

    PubMed Central

    Ferrando-May, Elisa; Tomas, Martin; Blumhardt, Philipp; Stöckl, Martin; Fuchs, Matthias; Leitenstorfer, Alfred

    2013-01-01

    Our understanding of the mechanisms governing the response to DNA damage in higher eucaryotes crucially depends on our ability to dissect the temporal and spatial organization of the cellular machinery responsible for maintaining genomic integrity. To achieve this goal, we need experimental tools to inflict DNA lesions with high spatial precision at pre-defined locations, and to visualize the ensuing reactions with adequate temporal resolution. Near-infrared femtosecond laser pulses focused through high-aperture objective lenses of advanced scanning microscopes offer the advantage of inducing DNA damage in a 3D-confined volume of subnuclear dimensions. This high spatial resolution results from the highly non-linear nature of the excitation process. Here we review recent progress based on the increasing availability of widely tunable and user-friendly technology of ultrafast lasers in the near infrared. We present a critical evaluation of this approach for DNA microdamage as compared to the currently prevalent use of UV or VIS laser irradiation, the latter in combination with photosensitizers. Current and future applications in the field of DNA repair and DNA-damage dependent chromatin dynamics are outlined. Finally, we discuss the requirement for proper simulation and quantitative modeling. We focus in particular on approaches to measure the effect of DNA damage on the mobility of nuclear proteins and consider the pros and cons of frequently used analysis models for FRAP and photoactivation and their applicability to non-linear photoperturbation experiments. PMID:23882280

  4. [Infrared laser radiation in the treatment of low back pain syndrome].

    PubMed

    Mika, T; Orłow, H; Kuszelewski, Z

    1990-06-01

    The effectiveness was estimated of infrared laser radiation in the treatment of low back pain syndrome. The patients received irradiation from a semiconductor laser. The results were evaluated in 82 patients using a questionnaire of pain, taking into account its intensity, frequency, taking of analgesics, and the motor activity of the patient. The results suggest a favourable effect of infrared laser radiation on pain.

  5. Laser Doppler velocimetry based on the optoacoustic effect in a RF-excited CO{sub 2} laser

    SciTech Connect

    Lee, Teaghee; Choi, Jong Woon; Kim, Yong Pyung

    2012-09-15

    We present a compact optoacoustic laser Doppler velocimetry method that utilizes the self-mixing effect in a RF-excited CO{sub 2} laser. A portion of a Doppler-shifted laser beam, produced by irradiating a single wavelength laser beam on a moving object, is mixed with an originally existing laser beam inside a laser cavity. The fine change of pressure in the laser cavity modulated by the Doppler-shifted frequency is detected by a condenser microphone in the laser tube. In our studies, the frequency of the Doppler signal due to the optoacoustic effect was detected as high as 50 kHz. Our measurements also confirmed that the signal varied linearly with the velocity of the external scatterer (the moving object) and the cosine of the angle between the laser beam and the velocity vector of the object.

  6. Picosecond passively mode-locked mid-infrared fiber laser

    NASA Astrophysics Data System (ADS)

    Wei, C.; Zhu, X.; Norwood, R. A.; Kieu, K.; Peyghambarian, N.

    2013-02-01

    Mode-locked mid-infrared (mid-IR) fiber lasers are of increasing interest due to their many potential applications in spectroscopic sensors, infrared countermeasures, laser surgery, and high-efficiency pump sources for nonlinear wavelength convertors. Er3+-doped ZBLAN (ZrF4-BaF2-LaF3-AlF3-NaF) fiber lasers, which can emit mid-IR light at 2.65-2.9 μm through the transition from the upper energy level 4I11/2 to the lower laser level 4I13/2, have attracted much attention because of their broad emission range, high optical efficiency, and the ready availability of diode pump lasers at the two absorption peaks of Er3+ ions (975 nm and 976 nm). In recent years, significant progress on high power Er3+- doped ZBLAN fiber lasers has been achieved and over 20 watt cw output at 2.8 μm has been demonstrated; however, there has been little progress on ultrafast mid-IR ZBLAN fiber lasers to date. We report a passively mode-locked Er3+- doped ZBLAN fiber laser in which a Fe2+:ZnSe crystal was used as the intracavity saturable absorber. Fe2+:ZnSe is an ideal material for mid-IR laser pulse generation because of its large saturable absorption cross-section and small saturation energy along with the excellent opto-mechanical (damage threshold ~2 J/cm2) and physical characteristics of the crystalline ZnSe host. A 1.6 m double-clad 8 mol% Er3+-doped ZBLAN fiber was used in our experiment. The fiber core has a diameter of 15 μm and a numerical aperture (NA) of 0.1. The inner circular cladding has a diameter of 125 μm and an NA of 0.5. Both continuous-wave and Q-switched mode-locking pulses at 2.8 μm were obtained. Continuous-wave mode locking operation with a pulse duration of 19 ps and an average power of 51 mW were achieved when a collimated beam traversed the Fe2+:ZnSe crystal. When the cavity was modified to provide a focused beam at the Fe2+:ZnSe crystal, Q-switched mode-locked operation with a pulse duration of 60 ps and an average power of 4.6 mW was achieved. More powerful

  7. Excited state two photon absorption of a charge transfer radical dimer in the near infrared.

    PubMed

    Schiccheri, Nicola; Meneghetti, Moreno

    2005-06-02

    Nonlinear transmission measurements of a solution of radical dimers of tetramethyl-tetrathiafulvalene, (TMTTF+)2, recorded with 9 ns laser pulses at 1064 nm are reported and interpreted on the basis of a multiphoton absorption process. One finds that the process can be interpreted with a sequence of three photon absorption, the first being a one photon absorption related to the intermolecular charge transfer process characteristic of the dimers and the second a two photon absorption from the excited state created with the first process. A model calculation allows one to obtain the value of the two photon absorption cross section which is found to be several orders of magnitude larger than those usually found for two photon absorbing systems excited from the ground state. These results show the importance of an excited-state population for obtaining large nonlinear optical responses.

  8. Study on laser and infrared attenuation performance of carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Liu, Xiang-cui; Liu, Qing-hai; Dai, Meng-yan; Cheng, Xiang; Fang, Guo-feng; Zhang, Tong; Liu, Haifeng

    2014-11-01

    In recent years, the weapon systems of laser and infrared (IR) imaging guidance have been widely used in modern warfare because of their high precision and strong anti-interference. However, military smoke, a rapid and effective passive jamming method, can effectively counteract the attack of precision-guided weapons by their scattering and absorbing effects. The traditional smoke has good visible light (0.4-0.76μm) obscurant performance, but hardly any effects to other electromagnetic wave bands while the weapon systems of laser and IR imaging guidance usually work in broad band, including the near-infrared (1-3μm), middle-infrared (3-5μm), far-infrared (8-14μm), and so on. Accordingly, exploiting new effective obscurant materials has attracted tremendous interest worldwide nowadays. As is known, the nano-structured materials have lots of unique properties comparing with the traditional materials suggesting that they might be the perfect alternatives to solve the problems above. Carbon nanotubes (CNTs) are well-ordered, all-carbon hollow graphitic nano-structured materials with a high aspect ratio, lengths from several hundred nanometers to several millimeters. CNTs possess many unique intrinsic physical-chemical properties and are investigated in many areas reported by the previous studies. However, no application research about CNTs in smoke technology field is reported yet. In this paper, the attenuation performances of CNTs smoke to laser and IR were assessed in 20m3 smoke chamber. The testing wavebands employed in experiments are 1.06μm and 10.6μm laser, 3-5μm and 8-14μm IR radiation. The main parameters were obtained included the attenuation rate, transmission rate, mass extinction coefficient, etc. The experimental results suggest that CNTs smoke exhibits excellent attenuation ability to the broadband IR radiation. Their mass extinction coefficients are all above 1m2·g-1. Nevertheless, the mass extinction coefficients vary with the sampling time

  9. Retinal safety of near-infrared lasers in cataract surgery

    NASA Astrophysics Data System (ADS)

    Wang, Jenny; Sramek, Christopher; Paulus, Yannis M.; Lavinsky, Daniel; Schuele, Georg; Anderson, Dan; Dewey, David; Palanker, Daniel

    2012-09-01

    Femtosecond lasers have added unprecedented precision and reproducibility to cataract surgery. However, retinal safety limits for the near-infrared lasers employed in surgery are not well quantified. We determined retinal injury thresholds for scanning patterns while considering the effects of reduced blood perfusion from rising intraocular pressure and retinal protection from light scattering on bubbles and tissue fragments produced by laser cutting. We measured retinal damage thresholds of a stationary, 1030-nm, continuous-wave laser with 2.6-mm retinal spot size for 10- and 100-s exposures in rabbits to be 1.35 W (1.26 to 1.42) and 0.78 W (0.73 to 0.83), respectively, and 1.08 W (0.96 to 1.11) and 0.36 W (0.33 to 0.41) when retinal perfusion is blocked. These thresholds were input into a computational model of ocular heating to calculate damage threshold temperatures. By requiring the tissue temperature to remain below the damage threshold temperatures determined in stationary beam experiments, one can calculate conservative damage thresholds for cataract surgery patterns. Light scattering on microbubbles and tissue fragments decreased the transmitted power by 88% within a 12 deg angle, adding a significant margin for retinal safety. These results can be used for assessment of the maximum permissible exposure during laser cataract surgery under various assumptions of blood perfusion, treatment duration, and scanning patterns.

  10. High-speed high-sensitivity infrared spectroscopy using mid-infrared swept lasers (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Childs, David T. D.; Groom, Kristian M.; Hogg, Richard A.; Revin, Dmitry G.; Cockburn, John W.; Rehman, Ihtesham U.; Matcher, Stephen J.

    2016-03-01

    Infrared spectroscopy is a highly attractive read-out technology for compositional analysis of biomedical specimens because of its unique combination of high molecular sensitivity without the need for exogenous labels. Traditional techniques such as FTIR and Raman have suffered from comparatively low speed and sensitivity however recent innovations are challenging this situation. Direct mid-IR spectroscopy is being speeded up by innovations such as MEMS-based FTIR instruments with very high mirror speeds and supercontinuum sources producing very high sample irradiation levels. Here we explore another possible method - external cavity quantum cascade lasers (EC-QCL's) with high cavity tuning speeds (mid-IR swept lasers). Swept lasers have been heavily developed in the near-infrared where they are used for non-destructive low-coherence imaging (OCT). We adapt these concepts in two ways. Firstly by combining mid-IR quantum cascade gain chips with external cavity designs adapted from OCT we achieve spectral acquisition rates approaching 1 kHz and demonstrate potential to reach 100 kHz. Secondly we show that mid-IR swept lasers share a fundamental sensitivity advantage with near-IR OCT swept lasers. This makes them potentially able to achieve the same spectral SNR as an FTIR instrument in a time x N shorter (N being the number of spectral points) under otherwise matched conditions. This effect is demonstrated using measurements of a PDMS sample. The combination of potentially very high spectral acquisition rates, fundamental SNR advantage and the use of low-cost detector systems could make mid-IR swept lasers a powerful technology for high-throughput biomedical spectroscopy.

  11. Unified Time and Frequency Picture of Ultrafast Atomic Excitation in Strong Laser Fields.

    PubMed

    Zimmermann, H; Patchkovskii, S; Ivanov, M; Eichmann, U

    2017-01-06

    Excitation and ionization in strong laser fields lies at the heart of such diverse research directions as high-harmonic generation and spectroscopy, laser-induced diffraction imaging, emission of femtosecond electron bunches from nanotips, self-guiding, filamentation and mirrorless lasing during propagation of light in atmospheres. While extensive quantum mechanical and semiclassical calculations on strong-field ionization are well backed by sophisticated experiments, the existing scattered theoretical work aiming at a full quantitative understanding of strong-field excitation lacks experimental confirmation. Here we present experiments on strong-field excitation in both the tunneling and multiphoton regimes and their rigorous interpretation by time dependent Schrödinger equation calculations, which finally consolidates the seemingly opposing strong-field regimes with their complementary pictures. Most strikingly, we observe an unprecedented enhancement of excitation yields, which opens new possibilities in ultrafast strong-field control of Rydberg wave packet excitation and laser intensity characterization.

  12. Unified Time and Frequency Picture of Ultrafast Atomic Excitation in Strong Laser Fields

    NASA Astrophysics Data System (ADS)

    Zimmermann, H.; Patchkovskii, S.; Ivanov, M.; Eichmann, U.

    2017-01-01

    Excitation and ionization in strong laser fields lies at the heart of such diverse research directions as high-harmonic generation and spectroscopy, laser-induced diffraction imaging, emission of femtosecond electron bunches from nanotips, self-guiding, filamentation and mirrorless lasing during propagation of light in atmospheres. While extensive quantum mechanical and semiclassical calculations on strong-field ionization are well backed by sophisticated experiments, the existing scattered theoretical work aiming at a full quantitative understanding of strong-field excitation lacks experimental confirmation. Here we present experiments on strong-field excitation in both the tunneling and multiphoton regimes and their rigorous interpretation by time dependent Schrödinger equation calculations, which finally consolidates the seemingly opposing strong-field regimes with their complementary pictures. Most strikingly, we observe an unprecedented enhancement of excitation yields, which opens new possibilities in ultrafast strong-field control of Rydberg wave packet excitation and laser intensity characterization.

  13. Intracellular protein mass spectroscopy using mid-infrared laser ionization

    NASA Astrophysics Data System (ADS)

    Awazu, K.; Suzuki, S.

    2007-07-01

    Large-scale analysis of proteins, which can be regarded as functional biomolecule, assumes an important role in the life science. A MALDI using an ultraviolet laser (UV-MALDI) is one of ionization methods without fragmentation and has achieved conformation analysis of proteins. Recently, protein analysis has shifted from conformation analysis to functional and direct one that reserves posttranslational modifications such as the sugar chain addition and phosphorylation. We have proposed a MALDI using a mid-infrared tunable laser (IR-MALDI) as a new ionization method. IR-MALDI is promising because most biomolecules have a specific absorption in mid-infrared range, and IR-MALDI is expected to offer; (1) use of various matrices, (2) use of biomolecules such as water and lipid as the matrix, and (3) super-soft ionization. First, we evaluated the wavelength dependence of ionization of different matrices using a difference frequency generation (DFG) laser, which can tune the wavelength within a range from 5.5 to 10.0 μm. As results, ionization was specifically occurred at 5.8 μm which the C=O vibration stretching bond in matrix material and mass spectrum was observed. Next, protein mass spectrum was observed in the culture cells, MIN6, which secrete insulin, without the conventional cell-preparation processes. We demonstrate that the IR-MALDI has an advantage over the conventional method (UV-MALDI) in direct analysis of intracellular proteins.

  14. Infrared laser sealing of porcine tissues: preliminary in vivo studies

    NASA Astrophysics Data System (ADS)

    Cilip, Christopher M.; Hutchens, Thomas C.; Kerr, Duane; Latimer, Cassandra; Rosenbury, Sarah B.; Giglio, Nicholas C.; Schweinsberger, Gino R.; Perkins, William C.; Wilson, Christopher R.; Ward, Arlen; Nau, William H.; Fried, Nathaniel M.

    2015-02-01

    We are exploring infrared (IR) lasers as an alternative energy modality to radiofrequency (RF) and ultrasonic (US) devices intended to provide rapid surgical hemostasis with minimal collateral zones of thermal damage and tissue necrosis. Previously, a 1470-nm IR laser sealed and cut ex vivo porcine renal arteries of 1-8 mm in 2 s, yielding burst pressures < 1200 mmHg (compared to normal systolic blood pressure of 120 mmHg) and thermal coagulation zones < 3 mm (including the seal). This preliminary study describes in vivo testing of a laser probe in a porcine model. A prototype, fiber optic based handheld probe with vessel/tissue clasping mechanism was tested on blood vessels < 6 mm diameter using incident 1470-nm laser power of 35 W for 1-5 s. The probe was evaluated for hemostasis after sealing isolated and bundled vasculature of abdomen and hind leg, as well as liver and lung parenchyma. Sealed vessel samples were collected for histological analysis of lateral thermal damage. Hemostasis was achieved in 57 of 73 seals (78%). The probe consistently sealed vasculature in small bowel mesentery, mesometrium, and gastro splenic and epiploic regions. Seal performance was less consistent on hind leg vasculature including saphenous arteries and bundles and femoral and iliac arteries. Collagen denaturation averaged 1.6 mm in 8 samples excised for histologic examination. A handheld laser probe sealed porcine vessels in vivo. With further improvements in probe design and laser parameter optimization, IR lasers may provide an alternative to RF and US vessel sealing devices.

  15. Multi-excitation near infrared (NIR) spectral fluorescence imaging using organic fluorophores

    NASA Astrophysics Data System (ADS)

    Kobayashi, Hisataka; Koyama, Yoshinori; Barrett, Tristan; Hama, Yukihiro; Choyke, Peter L.

    2008-02-01

    The ability to obtain multi-color fluorescent imaging in vivo simultaneously using multi-targeted imaging probes could be of potential benefit from both a research and a clinical perspective. However, the simultaneous acquisition of more than 2 separate organic fluorophores usually requires more than one excitation source, since a single excitation source may not optimally excite all the fluorophores. In this study, we employed a multi-excitation approach in order to acquire optimized images with multiple near infrared (NIR) organic fluorophores at the same time. Using 3 sets of excitation filters (595+/-20nm, 640+/-25nm, 688+/-17nm) to acquire 3 distinct spectra and spectral unmixing software (CRi, Woburn, MA), it was possible to resolve the emission spectra of each of the NIR fluorophores using commercial software (Nuance, CRi, Woburn, MA) To demonstrate the utility of this approach 2 mouse models were investigated; In one model, mice bearing four implanted malignancies were injected with a cocktail of 3 fluorescently labeled monoclonal antibodies, each with its own distinct NIR fluorophore. In the second model five different lymph node drainage basins were imaged with 5-color dendrimer-based lymphatic imaging agents tagged with 5 different NIR fluorophores. We successfully detected each of the targeted tumors in the first model and all of the lymph nodes by their distinct color in the second model; neither of which would have been possible using the single excitation method. In conclusion, multi-excitation NIR spectral fluorescence imaging is feasible in a reasonable time frame and opens the possibility for in vivo immunohistochemical imaging (IHCi).

  16. Vibrational eigenvalues and eigenfunctions for planar acetylene by wave-packet propagation, and its mode-selective infrared excitation

    NASA Astrophysics Data System (ADS)

    Liu, Li; Muckerman, James T.

    1997-09-01

    Vibrational eigenvalues with estimated errors <5×10-2 cm-1 and their corresponding eigenfunctions for J=0 5D (planar) acetylene modeled by the Halonen-Child-Carter potential-energy surface are obtained using an energy-shifted, imaginary-time Lanczos propagation of symmetry-adapted wave packets. A lower resolution (˜4 cm-1) vibrational eigenspectrum of the system is also calculated by the Fourier transform of the autocorrelation of an appropriate wave packet. The eigenvalues from both approaches are in excellent agreement. The wave function of the molecule is represented in a direct-product discrete variable representation (DVR) with nearly 300 000 grid points. Our results are compared with the previously reported theoretical and experimental values. We use our 69 computed eigenstates as a basis to perform an optimal control simulation of selective two-photon excitation of the symmetric CH-stretch mode with an infrared, linearly polarized, transform-limited, and subpicosecond-picosecond laser pulse. The resulting optimal laser pulses, which are then tested on the full DVR grid, fall within the capabilities of current powerful, subpicosecond, and tunable light sources.

  17. Density gradient free electron collisionally excited x-ray laser

    DOEpatents

    Campbell, E.M.; Rosen, M.D.

    1984-11-29

    An operational x-ray laser is provided that amplifies 3p-3s transition x-ray radiation along an approximately linear path. The x-ray laser is driven by a high power optical laser. The driving line focused optical laser beam illuminates a free-standing thin foil that may be associated with a substrate for improved structural integrity. This illumination produces a generally cylindrically shaped plasma having an essentially uniform electron density and temperature, that exists over a long period of time, and provides the x-ray laser gain medium. The x-ray laser may be driven by more than one optical laser beam. The x-ray laser has been successfully demonstrated to function in a series of experimental tests.

  18. Density gradient free electron collisionally excited X-ray laser

    DOEpatents

    Campbell, Edward M.; Rosen, Mordecai D.

    1989-01-01

    An operational X-ray laser (30) is provided that amplifies 3p-3s transition X-ray radiation along an approximately linear path. The X-ray laser (30) is driven by a high power optical laser. The driving line focused optical laser beam (32) illuminates a free-standing thin foil (34) that may be associated with a substrate (36) for improved structural integrity. This illumination produces a generally cylindrically shaped plasma having an essentially uniform electron density and temperature, that exists over a long period of time, and provides the X-ray laser gain medium. The X-ray laser (30) may be driven by more than one optical laser beam (32, 44). The X-ray laser (30) has been successfully demonstrated to function in a series of experimental tests.

  19. Influence of the excitation circuits on the CuBr laser performance

    SciTech Connect

    Vuchkov, N.K.; Astadjov, D.N.; Sabotinov, N.V. . Inst. of Solid State Physics)

    1994-03-01

    A comparative study has been carried out of the output characteristics, electric parameters, and main kinetic plasma processes concerning CuBr laser performance during the excitation pulse. Four electric circuits were used for CuBr vapor laser excitation: WPC (without peaking capacitor); OC (ordinary circuit, i.e., with a peaking capacitor); IPC (interacting peaking circuits), and IC (interacting circuits). The calculated and experimental values are in very good agreement. The improvement of the CuBr laser performance from WPC- to IC-excitation (the laser power and efficiency increase three times) is mainly attributed to the increased physical laser efficiency, which concerns the electrooptic energy conversion with regard to plasma kinetic processes.

  20. Pulsed laser excitation power dependence of photoluminescence peak energies in bulk ZnO

    NASA Astrophysics Data System (ADS)

    Dang, Giang T.; Kanbe, Hiroshi; Kawaharamura, Toshiyuki; Taniwaki, Masafumi

    2011-10-01

    Photoluminescence (PL) spectra of hydrothermal bulk ZnO were measured in the temperature range from 5 to 298 K. The sample was excited by means of the 266-nm line of an Nd3+: YAG Q-switched pulsed laser with numerous average excitation powers in the range from 0.33 to 7.50 mW. At constant temperatures, the most intense PL peak red-shifts with average excitation power, whereas positions of other near-band-edge peaks remain unchanged. It was experimentally proven that the red-shift is not due to local heating at the excited spot. Rather, it is due to relaxation of photoexcited carriers to lower energy transitions as the most intense transition is saturated by high excitation photon density. Furthermore, the temperature dependence of energy of the most intense PL peak was fitted with the Varshni equation. The Varshni coefficients α and β decrease with increasing pulsed laser excitation power.

  1. Infrared laser spectroscopy of the linear C13 carbon cluster

    NASA Technical Reports Server (NTRS)

    Giesen, T. F.; Van Orden, A.; Hwang, H. J.; Fellers, R. S.; Provencal, R. A.; Saykally, R. J.

    1994-01-01

    The infrared absorption spectrum of a linear, 13-atom carbon cluster (C13) has been observed by using a supersonic cluster beam-diode laser spectrometer. Seventy-six rovibrational transitions were measured near 1809 wave numbers and assigned to an antisymmetric stretching fundamental in the 1 sigma g+ ground state of C13. This definitive structural characterization of a carbon cluster in the intermediate size range between C10 and C20 is in apparent conflict with theoretical calculations, which predict that clusters of this size should exist as planar monocyclic rings.

  2. Tunable Infrared Laser Instruments for Airborne Atmospheric Studies

    NASA Technical Reports Server (NTRS)

    Fried, A.; Diskin, G.; Weibring, P.; Richter, D.; Walega, J. G.; Sachse, G.; Slate, T.; Rana, M.; Podolske, J.

    2008-01-01

    Tunable infrared laser-based instruments on airborne platforms have provided invaluable contributions to atmospheric studies over the past several decades. This paper presents an overview of some recent studies and developments using this approach that were presented at the 2007 Field Laser Applications in Industry and Research (FLAIR, http://www.inoa.it/flair/) conference in Florence, Italy. The present overview only covers select in situ absorption-based instruments that were presented in the airborne session at this conference. In no case are comprehensive details presented. These details can be found in the numerous references given. Additional approaches based upon cavity-enhanced and photoacoustic measurements, which are also making invaluable contributions in airborne atmospheric studies, are not discussed in this brief overview.

  3. Target tracking using infrared measurements and laser illumination

    NASA Astrophysics Data System (ADS)

    Maybeck, Peter S.; Herrera, Theodore D.; Evans, Roger J.

    1994-07-01

    A missile target tracker is designed using a filter/correlator (with adaptive target shape identification) based on forward-looking infrared (FLIR) sensor measurements to track the center-of-intensity of the hardbody/plume combination, and another filter using Doppler and/or speckle information in the return from a low-power laser illuminator to estimate the offset between the intensity centroid and the hardbody center-of-mass. The Doppler information is shown to yield smaller bias and error variance from the tracker than the speckle information. Performance of trackers based on just Doppler or both Doppler and speckle information from the laser return is portrayed as a function of important parameters in the tracking environment.

  4. Chemical analysis of surgical smoke by infrared laser spectroscopy

    NASA Astrophysics Data System (ADS)

    Gianella, Michele; Sigrist, Markus W.

    2012-11-01

    The chemical composition of surgical smoke, a gaseous by-product of some surgical devices—lasers, drills, vessel sealing devices—is of great interest due to the many toxic components that have been found to date. For the first time, surgical smoke samples collected during routine keyhole surgery were analyzed with infrared laser spectroscopy. Traces (ppm range) of methane, ethane, ethylene, carbon monoxide and sevoflurane were detected in the samples which consisted mostly of carbon dioxide and water vapor. Except for the anaesthetic sevoflurane, none of the compounds were present at dangerous concentrations. Negative effects on the health of operation room personnel can be excluded for many toxic compounds found in earlier studies, since their concentrations are below recommended exposure limits.

  5. Infrared Laser Ablation Sample Transfer for MALDI and Electrospray

    NASA Astrophysics Data System (ADS)

    Park, Sung-Gun; Murray, Kermit King

    2011-08-01

    We have used an infrared laser to ablate materials under ambient conditions that were captured in solvent droplets. The droplets were either deposited on a MALDI target for off-line analysis by MALDI time-of-flight mass spectrometry or flow-injected into a nanoelectrospray source of an ion trap mass spectrometer. An infrared optical parametric oscillator (OPO) laser system at 2.94 μm wavelength and approximately 1 mJ pulse energy was focused onto samples for ablation at atmospheric pressure. The ablated material was captured in a solvent droplet 1-2 mm in diameter that was suspended from a silica capillary a few millimeters above the sample target. Once the sample was transferred to the droplet by ablation, the droplet was deposited on a MALDI target. A saturated matrix solution was added to the deposited sample, or in some cases, the suspended capture droplet contained the matrix. Peptide and protein standards were used to assess the effects of the number of IR laser ablation shots, sample to droplet distance, capture droplet size, droplet solvent, and laser pulse energy. Droplet collected samples were also injected into a nanoelectrospray source of an ion trap mass spectrometer with a 500 nL injection loop. It is estimated that pmol quantities of material were transferred to the droplet with an efficiency of approximately 1%. The direct analysis of biological fluids for off-line MALDI and electrospray was demonstrated with blood, milk, and egg. The implications of this IR ablation sample transfer approach for ambient imaging are discussed.

  6. Characterizing Far-infrared Laser Emissions and the Measurement of Their Frequencies.

    PubMed

    Jackson, Michael; Zink, Lyndon R

    2015-12-18

    The generation and subsequent measurement of far-infrared radiation has found numerous applications in high-resolution spectroscopy, radio astronomy, and Terahertz imaging. For about 45 years, the generation of coherent, far-infrared radiation has been accomplished using the optically pumped molecular laser. Once far-infrared laser radiation is detected, the frequencies of these laser emissions are measured using a three-laser heterodyne technique. With this technique, the unknown frequency from the optically pumped molecular laser is mixed with the difference frequency between two stabilized, infrared reference frequencies. These reference frequencies are generated by independent carbon dioxide lasers, each stabilized using the fluorescence signal from an external, low pressure reference cell. The resulting beat between the known and unknown laser frequencies is monitored by a metal-insulator-metal point contact diode detector whose output is observed on a spectrum analyzer. The beat frequency between these laser emissions is subsequently measured and combined with the known reference frequencies to extrapolate the unknown far-infrared laser frequency. The resulting one-sigma fractional uncertainty for laser frequencies measured with this technique is ± 5 parts in 10(7). Accurately determining the frequency of far-infrared laser emissions is critical as they are often used as a reference for other measurements, as in the high-resolution spectroscopic investigations of free radicals using laser magnetic resonance. As part of this investigation, difluoromethane, CH2F2, was used as the far-infrared laser medium. In all, eight far-infrared laser frequencies were measured for the first time with frequencies ranging from 0.359 to 1.273 THz. Three of these laser emissions were discovered during this investigation and are reported with their optimal operating pressure, polarization with respect to the CO2 pump laser, and strength.

  7. Molecular Gas-Filled Hollow Optical Fiber Lasers in the Near Infrared

    DTIC Science & Technology

    2012-01-12

    HOLLOW OPTICAL FIBER LASERS IN THE NEAR F A9550-08-l-0344 INFRARED Sb. GRANT NUMBER Sc. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Sd. PROJECT NUMBER...SUPPLEMENTARY NOTES 14. ABSTRACT We have demonstrated of a new class of optically pumped gas lasers inside a hollow-core photonic crystal fibers . Here, a...crystal fiber . These lasers are the first in a new class of infrared lasers based on the combination of hollow- fiber and optically pumped-gas

  8. Infrared laser deposition of Teflon coatings on microstructures

    NASA Astrophysics Data System (ADS)

    Papantonakis, M. R.; HaglundJr., R. F.

    2006-01-01

    Polytetrafluoroethylene (PTFE, trade name Teflon) has a wide range of unique and desirable physical, electrical and chemical properties. Its tribological properties are well-suited to anti-stiction applications, and its chemical inertness commends it as a barrier and passivation layer. However, conventional thin-film techniques are not suited for depositing Teflon films on microstructures. Spin coating is impossible because of the well-known insolubility of PTFE. Plasma polymerization of fluorocarbon monomers, ion beam and rf sputtering produce PTFE films that are deficient in fluorine. Pulsed laser deposition (PLD) using excimer and Ti:sapphire lasers is unsatisfactory because UV or near-IR laser ablation "unzips" the PTFE, and requires high-temperature annealing to re-polymerize the deposited monomeric film. We have demonstrated that a completely dry, vapor-phase coating technique - resonant infrared pulsed laser deposition (RIR-PLD) at a wavelength of 8.26 μm -produces crystalline, smooth Teflon films at low process temperatures. Indeed, the films as deposited by RIR-PLD exhibit a surprising degree of crystallinity even at room temperature. The stoichiometry and local electronic structure are preserved during the laser vaporization process, as demonstrated by IR absorption and X-ray photoelectron spectroscopy. Films deposited on microscale structures show good adhesion, excellent smoothness, and a high degree of conformability to the structures. We also discuss experiments planned for the near future to compare the tribological properties of the PTFE films deposited by RIR-PLD with those of other tribological coatings. We will also discuss the implementation of RIR-PLD in practical processing schemes for MEMS applications, including the challenge in adapting existing solid-state mid-IR laser technology for this purpose.

  9. Laser hyperdoping silicon for enhanced infrared optoelectronic properties

    NASA Astrophysics Data System (ADS)

    Warrender, Jeffrey M.

    2016-09-01

    Pulsed laser melting and rapid solidification have attracted interest for decades as a method to achieve impurity concentrations in silicon orders of magnitude above the equilibrium solubility limit. The incorporation of sulfur into silicon using this technique led to the observation of strong broadband infrared absorption in the resulting material. This observation, combined with interest in impurity band optoelectronic device concepts, has resulted in renewed interest in laser techniques for achieving high impurity concentrations. In this paper, I review the literature that led to the present understanding of laser hyperdoping and provide a summary of the optical and optoelectronic measurements made on sulfur hyperdoped silicon to date. I mention recent work exploring transition metal impurities and discuss how considerations discovered in early solidification and later rapid solidification work inform our approaches to kinetically trapping such impurities. I also provide a simplified picture of how a laser hyperdoping process is typically carried out, as an entry point for an experimentalist seeking to fabricate such layers.

  10. Emission spectra of YAG:Er3+ under pulse laser-thermal excitation

    NASA Astrophysics Data System (ADS)

    Marchenko, V. M.; Shakir, Yu. A.

    2016-12-01

    Spectra and kinetics of emission of YAG:0.5% Er3+ monocrystal in visible and NIR ranges were investigated under laser-thermal excitation by the pulses of CO2 laser of 100 ns duration at wavelength λ = 10,6 μμm. Kinetics of integral emission was interpreted.

  11. Plastic lab-on-a-chip for fluorescence excitation with integrated organic semiconductor lasers.

    PubMed

    Vannahme, Christoph; Klinkhammer, Sönke; Lemmer, Uli; Mappes, Timo

    2011-04-25

    Laser light excitation of fluorescent markers offers highly sensitive and specific analysis for bio-medical or chemical analysis. To profit from these advantages for applications in the field or at the point-of-care, a plastic lab-on-a-chip with integrated organic semiconductor lasers is presented here. First order distributed feedback lasers based on the organic semiconductor tris(8-hydroxyquinoline) aluminum (Alq3) doped with the laser dye 4-dicyanomethylene-2-methyl-6-(p-dimethylaminostyril)-4H-pyrane (DCM), deep ultraviolet induced waveguides, and a nanostructured microfluidic channel are integrated into a poly(methyl methacrylate) (PMMA) substrate. A simple and parallel fabrication process is used comprising thermal imprint, DUV exposure, evaporation of the laser material, and sealing by thermal bonding. The excitation of two fluorescent marker model systems including labeled antibodies with light emitted by integrated lasers is demonstrated.

  12. Direct measurement of excited-state intervalence transfer in [(tpy)Ru(III)(tppz(*-))Ru(II)(tpy)](4+) by time-resolved near-infrared spectroscopy.

    PubMed

    Dattelbaum, Dana M; Hartshorn, Chris M; Meyer, Thomas J

    2002-05-08

    Extension of time-resolved infrared (TRIR) measurements into the near-infrared region has allowed the first direct measurement of a mixed-valence band in the metal-to-ligand charge transfer (MLCT) excited state of a symmetrical ligand-bridged complex. Visible laser flash excitation of [(tpy)Ru(tppz)Ru(tpy)]4+ (tppz is 2,3,5,6-tetrakis(2-pyridyl)pyrazine; tpy is 2,2':6',6' '-terpyridine) produces the mixed-valence, MLCT excited state [(tpy)RuIII(tppz*-)RuII(tpy)]4+* with the excited electron localized on the bridging tppz ligand. A mixed-valence band appears at numax = 6300 cm-1 with a bandwidth-at-half- maximum, Deltanu1/2 = 1070 cm-1. In the analogous ground-state complex, [(tpy)Ru(tppz)Ru(tpy)]5+, a mixed-valence band appears at numax = 6550 cm-1 with Deltanu1/2 = 970 cm-1 which allows a comparison to be made of electronic coupling across tppz0 and tppz*- as bridging ligands.

  13. Repetitive operation of switchless transverse flow transversely excited atmosphere CO2 lasers.

    PubMed

    Patil, Gautam C; Nilaya, J Padma; Biswas, D J

    2011-09-01

    The enhanced preionisation efficiency of a mutually coupled parallel spark preioniser has been exploited to achieve switchless operation of a transversely excited atmosphere (TEA) CO(2) laser in the conventional transverse gas flow configuration. This made the laser more compatible to repetitive operation and the satisfactory performance of a switchless TEA CO(2) laser of ~8 cc active volume is reported here up to a maximum repetition rate of 100 Hz at a gas replenishment factor of ~2.

  14. In situ microparticle analysis of marine phytoplankton cells with infrared laser-based optical tweezers

    NASA Astrophysics Data System (ADS)

    Sonek, G. J.; Liu, Y.; Iturriaga, R. H.

    1995-11-01

    We describe the application of infrared optical tweezers to the in situ microparticle analysis of marine phytoplankton cells. A Nd:YAG laser (lambda=3D 1064 nm) trap is used to confine and manipulate single Nannochloris and Synechococcus cells in an enriched seawater medium while spectral fluorescence and Lorenz-Mie backscatter signals are simultaneously acquired under a variety of excitation and trapping conditions. Variations in the measured fluorescence intensities of chlorophyll a (Chl a) and phycoerythrin pigments in phytoplankton cells are observed. These variations are related, in part, to basic intrasample variability, but they also indicate that increasing ultraviolet-exposure time and infrared trapping power may have short-term effects on cellular physiology that are related to Chl a photobleaching and laser-induced heating, respectively. The use of optical tweezers to study the factors that affect marine cell physiology and the processes of absorption, scattering, and attenuation by individual cells, organisms, and particulate matter that contribute to optical closure on a microscopic scale are also described. (c)1995 Optical Society of America

  15. Excitation of Accelerating Plasma Waves by Counter-propagating Laser Beams

    SciTech Connect

    Gennady Shvets; Nathaniel J. Fisch; and Alexander Pukhov

    2001-08-30

    Generation of accelerating plasma waves using two counter-propagating laser beams is considered. Colliding-beam accelerator requires two laser pulses: the long pump and the short timing beam. We emphasize the similarities and differences between the conventional laser wakefield accelerator and the colliding-beam accelerator (CBA). The highly nonlinear nature of the wake excitation is explained using both nonlinear optics and plasma physics concepts. Two regimes of CBA are considered: (i) the short-pulse regime, where the timing beam is shorter than the plasma period, and (ii) the parametric excitation regime, where the timing beam is longer than the plasma period. Possible future experiments are also outlined.

  16. Transverse-type laser assembly using induced electrical discharge excitation and method

    DOEpatents

    Ault, Earl R.

    1994-01-01

    A transverse-type laser assembly is disclosed herein. This assembly defines a laser cavity containing a vapor or gaseous substance which lases when subjected to specific electrical discharge excitation between a pair of spaced-apart electrodes located within the cavity in order to produce a source of light. An arrangement located entirely outside the laser cavity is provided for inducing a voltage across the electrodes within the cavity sufficient to provide the necessary electrical discharge excitation to cause a vapor substance between the electrodes to lase.

  17. Transverse-type laser assembly using induced electrical discharge excitation and method

    DOEpatents

    Ault, E.R.

    1994-04-19

    A transverse-type laser assembly is disclosed herein. This assembly defines a laser cavity containing a vapor or gaseous substance which lases when subjected to specific electrical discharge excitation between a pair of spaced-apart electrodes located within the cavity in order to produce a source of light. An arrangement located entirely outside the laser cavity is provided for inducing a voltage across the electrodes within the cavity sufficient to provide the necessary electrical discharge excitation to cause a vapor substance between the electrodes to lase. 3 figures.

  18. Surface modification of UHMWPE with infrared femtosecond laser

    NASA Astrophysics Data System (ADS)

    Fernández-Pradas, J. M.; Naranjo-León, S.; Morenza, J. L.; Serra, P.

    2012-09-01

    Ultra-high-molecular-weight polyethylene (UHMWPE) is a polymer with mechanical and corrosion properties, which make it appropriate for using in biomedical devices such as hip and knee prostheses. The surface morphology and chemistry of UHMWPE influence its biocompatibility. A laser with wavelength at 1027 nm delivering 450 fs pulses at a repetition rate of 1 kHz is used to modify the surface of UHMWPE samples with 0.45 μm root mean square surface roughness. Micrometric resolution is achieved with the use of a focusing lens of 0.25 NA and pulse energies of few microjoules. The study focuses in the influence of different pulse energies and pulse overlaps on the laser-induced surface roughness and ablation yield. Confocal microscopy is used to characterize changes in the morphology of the irradiated surfaces, and their chemical structure is analyzed by attenuated total reflectance infrared and Raman spectroscopies. The roughness increases as the pulse energy increases until it reaches a maximum. The ablation yield increases with the pulse energy and pulse overlap. However, the ablation yield per pulse is lower for higher pulse overlap. Pulses of 6 μJ have the highest ablation efficiency. Infrared and Raman spectra of samples irradiated with low energy pulses are similar to those of the pristine sample. However, some Cdbnd C and Cdbnd O bonds can be detected after irradiation with the highest pulse energies.

  19. Mid-infrared absorption spectroscopy using quantum cascade lasers

    NASA Astrophysics Data System (ADS)

    Haibach, Fred; Erlich, Adam; Deutsch, Erik

    2011-06-01

    Block Engineering has developed an absorption spectroscopy system based on widely tunable Quantum Cascade Lasers (QCL). The QCL spectrometer rapidly cycles through a user-selected range in the mid-infrared spectrum, between 6 to 12 μm (1667 to 833 cm-1), to detect and identify substances on surfaces based on their absorption characteristics from a standoff distance of up to 2 feet with an eye-safe laser. It can also analyze vapors and liquids in a single device. For military applications, the QCL spectrometer has demonstrated trace explosive, chemical warfare agent (CWA), and toxic industrial chemical (TIC) detection and analysis. The QCL's higher power density enables measurements from diffuse and highly absorbing materials and substrates. Other advantages over Fourier Transform Infrared (FTIR) spectroscopy include portability, ruggedness, rapid analysis, and the ability to function from a distance through free space or a fiber optic probe. This paper will discuss the basic technology behind the system and the empirical data on various safety and security applications.

  20. Infrared upconversion for astronomical applications. [laser applications to astronomical spectroscopy of infrared spectra

    NASA Technical Reports Server (NTRS)

    Abbas, M. M.; Kostiuk, T.; Ogilvie, K. W.

    1975-01-01

    The performance of an upconversion system is examined for observation of astronomical sources in the low to middle infrared spectral range. Theoretical values for the performance parameters of an upconversion system for astronomical observations are evaluated in view of the conversion efficiencies, spectral resolution, field of view, minimum detectable source brightness and source flux. Experimental results of blackbody measurements and molecular absorption spectrum measurements using a lithium niobate upconverter with an argon-ion laser as the pump are presented. Estimates of the expected optimum sensitivity of an upconversion device which may be built with the presently available components are given.

  1. Simple Short-Pulse CO2 Laser Excited by Longitudinal Discharge without High-Voltage Switch

    NASA Astrophysics Data System (ADS)

    Uno, Kazuyuki; Jitsuno, Takahisa; Akitsu, Tetsuya

    2012-05-01

    We have developed a longitudinally excited CO2 laser without a high-voltage switch. The laser produces a short laser pulse similar to those from TEA and Q-switched CO2 lasers. This system, which is the simplest short-pulse CO2 laser yet constructed, includes a pulsed power supply, a high-speed step-up transformer, a storage capacitor, and a laser tube. At high pressure (4.2 kPa and above), a rapid discharge produces a short laser pulse with a sharp spike pulse. In mixed gas (CO2: N2: He = 1: 1: 2) at a pressure of 9.0 kPa, the laser pulse contains a spike pulse of 218 ns and has a pulse tail length of 16.7 μs.

  2. Resonant and nonresonant vibrational excitation of ammonia molecules in the growth of gallium nitride using laser-assisted metal organic chemical vapour deposition

    NASA Astrophysics Data System (ADS)

    Golgir, Hossein Rabiee; Zhou, Yun Shen; Li, Dawei; Keramatnejad, Kamran; Xiong, Wei; Wang, Mengmeng; Jiang, Li Jia; Huang, Xi; Jiang, Lan; Silvain, Jean Francois; Lu, Yong Feng

    2016-09-01

    The influence of exciting ammonia (NH3) molecular vibration in the growth of gallium nitride (GaN) was investigated by using an infrared laser-assisted metal organic chemical vapor deposition method. A wavelength tunable CO2 laser was used to selectively excite the individual vibrational modes. Resonantly exciting the NH-wagging mode (v2) of NH3 molecules at 9.219 μm led to a GaN growth rate of 84 μm/h, which is much higher than the reported results. The difference between the resonantly excited and conventional thermally populated vibrational states was studied via resonant and nonresonant vibrational excitations of NH3 molecules. Resonant excitation of various vibrational modes was achieved at 9.219, 10.35, and 10.719 μm, respectively. Nonresonant excitation was conducted at 9.201 and 10.591 μm, similar to conventional thermal heating. Compared to nonresonant excitation, resonant excitation noticeably promotes the GaN growth rate and crystalline quality. The full width at half maximum value of the XRD rocking curves of the GaN (0002) and GaN (10-12) diffraction peaks decreased at resonant depositions and reached its minimum value of 45 and 53 arcmin, respectively, at the laser wavelength of 9.219 μm. According to the optical emission spectroscopic studies, resonantly exciting the NH3 v2 mode leads to NH3 decomposition at room temperature, reduces the formation of the TMGa:NH3 adduct, promotes the supply of active species in GaN formation, and, therefore, results in the increased GaN growth rate.

  3. Implementation of Time-Resolved Step-Scan Fourier Transform Infrared (FT-IR) Spectroscopy Using a kHz Repetition Rate Pump Laser

    PubMed Central

    MAGANA, DONNY; PARUL, DZMITRY; DYER, R. BRIAN; SHREVE, ANDREW P.

    2011-01-01

    Time-resolved step-scan Fourier transform infrared (FT-IR) spectroscopy has been shown to be invaluable for studying excited-state structures and dynamics in both biological and inorganic systems. Despite the established utility of this method, technical challenges continue to limit the data quality and more wide ranging applications. A critical problem has been the low laser repetition rate and interferometer stepping rate (both are typically 10 Hz) used for data acquisition. Here we demonstrate significant improvement in the quality of time-resolved spectra through the use of a kHz repetition rate laser to achieve kHz excitation and data collection rates while stepping the spectrometer at 200 Hz. We have studied the metal-to-ligand charge transfer excited state of Ru(bipyridine)3Cl2 in deuterated acetonitrile to test and optimize high repetition rate data collection. Comparison of different interferometer stepping rates reveals an optimum rate of 200 Hz due to minimization of long-term baseline drift. With the improved collection efficiency and signal-to-noise ratio, better assignments of the MLCT excited-state bands can be made. Using optimized parameters, carbonmonoxy myoglobin in deuterated buffer is also studied by observing the infrared signatures of carbon monoxide photolysis upon excitation of the heme. We conclude from these studies that a substantial increase in performance of ss-FT-IR instrumentation is achieved by coupling commercial infrared benches with kHz repetition rate lasers. PMID:21513597

  4. High power repetitive excimer lasers pumped by an all solid state magnetic exciter

    NASA Astrophysics Data System (ADS)

    Kobayashi, Osamu; Noda, Koji; Shimada, Tsutomu; Obara, Minoru

    1986-01-01

    In a high repetition rate excimer laser operation, the lifetime of the exciter is one of the most important problems. To attain a nearly endless lifetime of the excimer laser exciter, an all-solid-state exciter has been developed which consists of a high-voltage transformer switched by a silicon-controlled rectifier, producing a pulse whose energy and duration are 11.2 J and 8 microns, respectively, and a three-stage magnetic compressor. With a 1.4-ohm dummy load, output peak power, energy/pulse, and pulse duration were 100 MW, 5.2 J, and 100 ns, respectively. The electrical efficiency of the exciter was 47 percent. The energy loss of 6 J in the exciter was due both to the core loss and the transfer loss. It should be noted that the time jitter between the SCR gate input pulse and the output voltage pulse was less than 12 ns.

  5. Absorption-ablation-excitation mechanism of laser-cluster interactions in a nanoaerosol system.

    PubMed

    Ren, Yihua; Li, Shuiqing; Zhang, Yiyang; Tse, Stephen D; Long, Marshall B

    2015-03-06

    The absorption-ablation-excitation mechanism in laser-cluster interactions is investigated by measuring Rayleigh scattering of aerosol clusters along with atomic emission from phase-selective laser-induced breakdown spectroscopy. For 532 nm excitation, as the laser intensity increases beyond 0.16  GW/cm^{2}, the scattering cross section of TiO_{2} clusters begins to decrease, concurrent with the onset of atomic emission of Ti, indicating a scattering-to-ablation transition and the formation of nanoplasmas. With 1064 nm laser excitation, the atomic emissions are more than one order of magnitude weaker than that at 532 nm, indicating that the thermal effect is not the main mechanism. To better clarify the process, time-resolved measurements of scattering signals are examined for different excitation laser intensities. For increasing laser intensity, the cross section of clusters decreases during a single pulse, evincing the shorter ablation delay time and larger ratios of ablation clusters. Assessment of the electron energy distribution during the ablation process is conducted by nondimensionalizing the Fokker-Planck equation, with analogous Strouhal Sl_{E}, Peclet Pe_{E}, and Damköhler Da_{E} numbers defined to characterize the laser-induced aerothermochemical environment. For conditions where Sl_{E}≫1, Pe_{E}≫1, and Da_{E}≪1, the electrons are excited to the conduction band by two-photon absorption, then relax to the bottom of the conduction band by electron energy loss to the lattice, and finally serve as the energy transfer media between laser field and lattice. The relationship between delay time and excitation intensity is well correlated by this simplified model with quasisteady assumption.

  6. Activators of photoluminescence in calcite: evidence from high-resolution, laser-excited luminescence spectroscopy

    USGS Publications Warehouse

    Pedone, V.A.; Cercone, K.R.; Burruss, R.C.

    1990-01-01

    Laser-excited luminescence spectroscopy of a red-algal, biogenic calcite and a synthetic Mn-calcite can make the distinction between organic and trace-element activators of photoluminescence. Organic-activated photoluminescence in biogenic calcite is characterized by significant peak shifts and increasing intensity with shorter-wavelength excitation and by significant decreases in intensity after heating to ??? 400??C. In contrast, Mn-activated photoluminescence shows no peak shift, greatest intensity under green excitation and limited changes after heating. Examination of samples with a high-sensitivity spectrometer using several wavelengths of exciting light is necessary for identification of photoluminescence activators. ?? 1990.

  7. Experiments concerning the laser-enhanced reaction between vibrationally excited O3 and NO

    NASA Technical Reports Server (NTRS)

    Hui, K.-K.; Cool, T. A.

    1978-01-01

    The enhancement in reaction rate between O3 and NO is studied for the case of O3 vibrationally excited by a CO2 laser. Chemiluminescence observations of a vibrationally excited and an electronically excited nitrogen dioxide reaction product provide information on the separate contributions to the overall reaction rate of these two reactive channels. The contribution of the stretching and bending modes of O3 to the reaction rate enhancement is also discussed. In addition, consideration is given to the nonreactive vibrational deactivation of vibrationally excited O3.

  8. Sensitivity of laser-induced upconversion fluorescence dynamics to exciting wavelength in Er3+-doped YAG

    NASA Astrophysics Data System (ADS)

    Du, S.; Jiang, L.; Zhang, W.; Gong, W.; Fu, Z.; Dai, Z.

    2011-06-01

    A novel sensitivity of laser-induced upconversion (UC) fluorescence dynamics to the exciting wavelength in Er3+:YAG crystal has been observed. The sensitivities to exciting wavelength variations are only 0.02 and 0.06 nm for 2 G 9/2 and 2 P 3/2 UC luminescence, respectively. The observation of this sensitivity reveals that when a certain level is populated by more than one UC mechanisms, a precise determination of suitable exciting wavelength is crucial because the competition between different UC mechanisms has a sensitive variation with exciting wavelength in near-resonant range.

  9. Understanding the emission pattern produced by focused laser beam excitation of perylene square single crystals

    NASA Astrophysics Data System (ADS)

    Takazawa, Ken

    2017-01-01

    Square single crystals of perylene (α-crystals) exhibit a peculiar emission pattern when excited by a focused laser beam. Fluorescence spots are observed at the point of excitation and at four edges, with the lines connecting the excitation point and edge emissions being perpendicular to the edges irrespective of the excitation position. Two different mechanisms explaining this emission pattern have been proposed so far. Our newly designed experiment and analysis revealed that the involved mechanism features a combination of the waveguide effect and total internal reflection by crystal edges.

  10. Nuclear fission fragment excitation of electronic transition laser media

    NASA Technical Reports Server (NTRS)

    Lorents, D. C.; Mccusker, M. V.; Rhodes, C. K.

    1976-01-01

    Specific characteristics of the media including density, excitation rates, wavelength, kinetics, fissile material, scale size, and medium uniformity are assessed. The use of epithermal neutrons, homogeneously mixed fissile material, and special high cross section nuclear isotopes to optimize coupling of the energy to the medium are shown to be important considerations maximizing the scale size, energy deposition, and medium uniformity. It is demonstrated that e-beam excitation can be used to simulate nuclear pumping conditions to facilitate the search for candidate media.

  11. DEVELOPMENT OF NEW MID-INFRARED ULTRAFAST LASER SOURCES FOR COMPACT COHERENT X-RAY SOURCES

    SciTech Connect

    Sterling Backus

    2012-05-14

    In this project, we proposed to develop laser based mid-infrared lasers as a potentially robust and reliable source of ultrafast pulses in the mid-infrared region of the spectrum, and to apply this light source to generating bright, coherent, femtosecond-to-attosecond x-ray beams.

  12. Electron injector for Iranian Infrared Free Electron Laser

    NASA Astrophysics Data System (ADS)

    Rajabi, A.; Jazini, J.; Fathi, M.; Khosravi, N.; Shokri, B.

    2016-12-01

    The quality of the electron beam for applications like free electron lasers (FELs) has a direct impact on the quality of the laser radiation. The electron injector considered for Iranian Infrared Free Electron Laser (IRIFEL) includes a thermionic RF electron gun plus a bunch compressor as the electron preinjector and a 50 MeV constant gradient traveling wave linac as the main accelerator of the electron injector. In the present work, a thermionic RF gun is designed and matched with an optimized linac to produce a high quality mono-energetic electron beam. The results show that the preinjector is capable of delivering an electron bunch with 1 ps bunch length and 3 mm-mrad emittance to the linac entrance which is desirable for IRIFEL operation. The results also show that by geometrical manipulation and optimization of the linac structure, the pattern of the RF fields in the linac will be more symmetric, which is important in order to produce high stable mono-energetic bunches.

  13. Generation of tunable and broadband far-infrared laser pulses during two-color filamentation

    SciTech Connect

    Theberge, Francis; Chateauneuf, Marc; Roy, Gilles; Mathieu, Pierre; Dubois, Jacques

    2010-03-15

    Tunable far-infrared laser pulses were generated efficiently during two-color filamentation in air. Understanding the creation of few-cycle far-infrared laser pulses is important since it is at the frontier between two possible generation mechanisms. The first one is the four-wave mixing generation, associated to the generation of wavelengths from ultraviolet up to mid-infrared laser pulses. The second process is the formation of transient photocurrent, which was recently used to describe the generation of submillimetric (terahertz) waves. Comparison between experiments and simulations revealed that the four-wave mixing mechanism is dominant for the far-infrared generation during two-color filamentation.

  14. Near-infrared induced optical quenching effects on mid-infrared quantum cascade lasers

    SciTech Connect

    Guo, Dingkai Talukder, Muhammad Anisuzzaman; Chen, Xing; Cai, Hong; Johnson, Anthony M.; Choa, Fow-Sen; Khurgin, Jacob B.

    2014-06-23

    In space communications, atmospheric absorption and Rayleigh scattering are the dominant channel impairments. Transmission using mid-infrared (MIR) wavelengths offers the benefits of lower loss and less scintillation effects. In this work, we report the telecom wavelengths (1.55 μm and 1.3 μm) induced optical quenching effects on MIR quantum cascade lasers (QCLs), when QCLs are operated well above their thresholds. The QCL output power can be near 100% quenched using 20 mW of near-infrared (NIR) power, and the quenching effect depends on the input NIR intensity as well as wavelength. Time resolved measurement was conducted to explore the quenching mechanism. The measured recovery time is around 14 ns, which indicates that NIR generated electron-hole pairs may play a key role in the quenching process. The photocarrier created local field and band bending can effectively deteriorate the dipole transition matrix element and quench the QCL. As a result, MIR QCLs can be used as an optical modulator and switch controlled by NIR lasers. They can also be used as “converters” to convert telecom optical signals into MIR optical signals.

  15. Laser pulse trains for controlling excited state dynamics of adenine in water.

    PubMed

    Petersen, Jens; Wohlgemuth, Matthias; Sellner, Bernhard; Bonačić-Koutecký, Vlasta; Lischka, Hans; Mitrić, Roland

    2012-04-14

    We investigate theoretically the control of the ultrafast excited state dynamics of adenine in water by laser pulse trains, with the aim to extend the excited state lifetime and to suppress nonradiative relaxation processes. For this purpose, we introduce the combination of our field-induced surface hopping method (FISH) with the quantum mechanical-molecular mechanical (QM/MM) technique for simulating the laser-driven dynamics in the condensed phase under explicit inclusion of the solvent environment. Moreover, we employ parametric pulse shaping in the frequency domain in order to design simplified laser pulse trains allowing to establish a direct link between the pulse parameters and the controlled dynamics. We construct pulse trains which achieve a high excitation efficiency and at the same time keep a high excited state population for a significantly extended time period compared to the uncontrolled dynamics. The control mechanism involves a sequential cycling of the population between the lowest and higher excited states, thereby utilizing the properties of the corresponding potential energy surfaces to avoid conical intersections and thus to suppress the nonradiative decay to the ground state. Our findings provide a means to increase the fluorescence yield of molecules with an intrinsically very short excited state lifetime, which can lead to novel applications of shaped laser fields in the context of biosensing.

  16. Excitation and deexcitation of the Si-H stretching mode in a Si:H with picosecond free electron laser pulses

    SciTech Connect

    Xu, Z.; Fauchet, M.; Rella, C.W.

    1995-12-31

    Hydrogen in amorphous and crystalline silicon has been the topic of intense theoretical and experimental investigations for more than one decade. To better understand how the Si-H bonds interact with the Si matrix and how they can be broken, it would be useful to excite selectively these bonds and monitor the energy flow from the Si-H bonds into the bulk Si modes. One attractive way of exciting the Si-H modes selectively is with an infrared laser tuned to a Si-H vibrational mode. Unfortunately, up to now, this type of experiment had not been possible because of the lack of a laser producing intense, ultrashort pulses that are tunable in the mid infrared. In this presentation, we report the first measurement where a 1 picosecond long laser pulse was used to excite the Si-H stretching modes near 2000 cm{sup -1} and another identical laser pulse was used to measure the deexcitation from that specific vibrational mode. The laser was the Stanford free electron laser generating {approximately}1 ps-long pulses, tunable in the 5 {mu}m region and focussed to an intensity of {approximately}1 GW/cm{sup 2}. The pump-probe measurements were performed in transmission at room temperature on several 2 {mu}m thick a-Si:H films deposited on c-Si. Samples with predominant Si-H{sub 1} modes, predominant Si-H{sub n>1} modes and with a mixture of modes were prepared. The laser was tuned on resonance with either of these modes. Immediately after excitation, we observe a bleaching of the infrared absorption, which can be attributed to excitation of the Si-H mode. Beaching is expected since, as a result of anharmonicity, the detuning between the (E{sub 3} - E{sub 2}) resonance and the (E{sub 2} - E{sub 1}) resonance is larger than the laser bandwidth. Note that despite the anharmonicity, it should be possible to climb the vibrational ladder due to power broadening.

  17. Infrared

    NASA Astrophysics Data System (ADS)

    Vollmer, M.

    2013-11-01

    underlying physics. There are now at least six different disciplines that deal with infrared radiation in one form or another, and in one or several different spectral portions of the whole IR range. These are spectroscopy, astronomy, thermal imaging, detector and source development and metrology, as well the field of optical data transmission. Scientists working in these fields range from chemists and astronomers through to physicists and even photographers. This issue presents examples from some of these fields. All the papers—though some of them deal with fundamental or applied research—include interesting elements that make them directly applicable to university-level teaching at the graduate or postgraduate level. Source (e.g. quantum cascade lasers) and detector development (e.g. multispectral sensors), as well as metrology issues and optical data transmission, are omitted since they belong to fundamental research journals. Using a more-or-less arbitrary order according to wavelength range, the issue starts with a paper on the physics of near-infrared photography using consumer product cameras in the spectral range from 800 nm to 1.1 µm [1]. It is followed by a series of three papers dealing with IR imaging in spectral ranges from 3 to 14 µm [2-4]. One of them deals with laboratory courses that may help to characterize the IR camera response [2], the second discusses potential applications for nondestructive testing techniques [3] and the third gives an example of how IR thermal imaging may be used to understand cloud cover of the Earth [4], which is the prerequisite for successful climate modelling. The next two papers cover the vast field of IR spectroscopy [5, 6]. The first of these deals with Fourier transform infrared spectroscopy in the spectral range from 2.5 to 25 µm, studying e.g. ro-vibrational excitations in gases or optical phonon interactions within solids [5]. The second deals mostly with the spectroscopy of liquids such as biofuels and special

  18. Investigation of RF excited CW CO2 waveguide lasers local oscillator - RF excitation

    NASA Technical Reports Server (NTRS)

    Hochuli, U.

    1988-01-01

    A new local oscillator housing was built which seems to have improved laser life. Laser cooling was changed from internal water cooling to the more convenient thermal contact cooling. At the present time, a conclusion can not be made if the 20 percent reduction in power output is the result of poorer cooling or poorer grating alignment. The coupling-starting network was improved from 55 to about 90 percent. It can be adjusted by varying trimmers C sub 1 and C sub 2 to match RF power levels between 10 and 30 W. If the laser admittance changes greatly with laser life rematching will have to be achieved by remote control for space applications. The same holds true if the RF power level has to be changed with a maximum efficiency constraint.

  19. Output power of a quantum dot laser: Effects of excited states

    SciTech Connect

    Wu, Yuchang; Jiang, Li Asryan, Levon V.

    2015-11-14

    A theory of operating characteristics of quantum dot (QD) lasers is discussed in the presence of excited states in QDs. We consider three possible situations for lasing: (i) ground-state lasing only; (ii) ground-state lasing at first and then the onset of also excited-state lasing with increasing injection current; (iii) excited-state lasing only. The following characteristics are studied: occupancies of the ground-state and excited-state in QDs, free carrier density in the optical confinement layer, threshold currents for ground- and excited-state lasing, densities of photons emitted via ground- and excited-state stimulated transitions, output power, internal and external differential quantum efficiencies. Under the conditions of ground-state lasing only, the output power saturates with injection current. Under the conditions of both ground- and excited-state lasing, the output power of ground-state lasing remains pinned above the excited-state lasing threshold while the power of excited-state lasing increases. There is a kink in the light-current curve at the excited-state lasing threshold. The case of excited-state lasing only is qualitatively similar to that for single-state QDs—the role of ground-state transitions is simply reduced to increasing the threshold current.

  20. Excitability in optically injected semiconductor lasers: Contrasting quantum- well- and quantum-dot-based devices

    NASA Astrophysics Data System (ADS)

    Kelleher, B.; Bonatto, C.; Huyet, G.; Hegarty, S. P.

    2011-02-01

    Excitability is a generic prediction for an optically injected semiconductor laser. However, the details of the phenomenon differ depending on the type of device in question. For quantum-well lasers very complicated multipulse trajectories can be found, while for quantum-dot lasers the situation is much simpler. Experimental observations show the marked differences in the pulse shapes while theoretical considerations reveal the underlying mechanism responsible for the contrast, identifying the increased stability of quantum-dot lasers to perturbations as the root.

  1. Excitability in optically injected semiconductor lasers: contrasting quantum-well- and quantum-dot-based devices.

    PubMed

    Kelleher, B; Bonatto, C; Huyet, G; Hegarty, S P

    2011-02-01

    Excitability is a generic prediction for an optically injected semiconductor laser. However, the details of the phenomenon differ depending on the type of device in question. For quantum-well lasers very complicated multipulse trajectories can be found, while for quantum-dot lasers the situation is much simpler. Experimental observations show the marked differences in the pulse shapes while theoretical considerations reveal the underlying mechanism responsible for the contrast, identifying the increased stability of quantum-dot lasers to perturbations as the root.

  2. Investigation of quantum dot passively mode-locked lasers with excited-state transition.

    PubMed

    Cheng, Hsu-Chieh; Lee, Chien-Ping

    2013-11-04

    Monolithic passively mode-locked quantum dot lasers with excited-state transition were investigated in a broad operating range without ground-state lasing. Optical and electrical characteristics of these mode locked lasers were studied in detail at different levels of injection current and absorber bias. Very different behaviors in the evolution of the hysteresis, the optical spectra and the evolution of repetition frequency were observed between our lasers and conventional quantum dot lasers with ground-state transition. Possible mechanisms behind these observed phenomena were proposed and discussed. A minimum pulse width of 3.3 ps and an externally compressed pulse width of 0.78 ps were obtained.

  3. INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: Phase-sensitive electric modulation of photoluminescence upon bichromatic excitation of atoms

    NASA Astrophysics Data System (ADS)

    Astapenko, Valerii A.

    2005-12-01

    A new type of modulation of the photoluminescence intensity of atoms excited by a bichromatic laser radiation with the frequency ratio 1:2 is proposed and analysed. The modulation is produced by alternating electric field acting on atoms and occurs due to the quantum interference of the amplitudes of two excitation channels of an atom, which proves to be possible because the applied electric field removes the parity selection rule for one of the excitation channels. An important feature of this process is the dependence of photoluminescence on the phase difference of monochromatic components of exciting radiation. The calculation was performed for an alkali metal atom excited at the s—s transition taking the saturation effect into account.

  4. Resonant infrared pulsed laser deposition of a polyimide precursor

    NASA Astrophysics Data System (ADS)

    Dygert, N. L.; Schriver, K. E.; Haglund, R. F., Jr.

    2007-04-01

    Poly(amic acid) (PAA), a precursor to polyimide, was successfully deposited on substrates without reaching curing temperature, by resonant infrared pulsed laser ablation. The PAA was prepared by dissolving pyromellitic dianhydride and 4, 4' oxidianiline in the polar solvent Nmethyl pyrrolidinone (NMP). The PAA was deposited in droplet-like morphologies when ablation occurred in air, and in string-like moieties in the case of ablation in vacuum. In the as-deposited condition, the PAA was easily removed by washing with NMP; however, once cured thermally for thirty minutes, the PAA hardened, indicating the expected thermosetting property. Plume shadowgraphy showed very clear contrasts in the ablation mechanism between ablation of the solvent alone and the ablation of the PAA, even at low concentrations. A Wavelength dependence in plume velocity was also observed.

  5. Two-photon fluorescence excitation spectroscopy by pulse shaping ultrabroad-bandwidth femtosecond laser pulses

    SciTech Connect

    Xu Bingwei; Coello, Yves; Lozovoy, Vadim V.; Dantus, Marcos

    2010-11-10

    A fast and automated approach to measuring two-photon fluorescence excitation (TPE) spectra of fluorophores with high resolution ({approx}2 nm ) by pulse shaping ultrabroad-bandwidth femtosecond laser pulses is demonstrated. Selective excitation in the range of 675-990 nm was achieved by imposing a series of specially designed phase and amplitude masks on the excitation pulses using a pulse shaper. The method eliminates the need for laser tuning and is, thus, suitable for non-laser-expert use. The TPE spectrum of Fluorescein was compared with independent measurements and the spectra of the pH-sensitive dye 8-hydroxypyrene-1,3,6-trisulfonic acid (HPTS) in acidic and basic environments were measured for the first time using this approach.

  6. Ignition of a combustible gas mixture by a laser spark excited in the reactor volume

    SciTech Connect

    Kazantsev, S. Yu.; Kononov, I. G.; Kossyi, I. A.; Tarasova, N. M.; Firsov, K. N.

    2009-03-15

    Ignition of a stoichiometric CH{sub 4}: O{sub 2} mixture by a laser spark excited in the reactor volume is studied experimentally. It is found that the spark initiates a feebly radiating incomplete-combustion wave, which is much faster than the combustion wave, but is substantially slower than the detonation wave. With a time delay of 500-700 {mu}s, a bright optical flash occupying the entire chamber volume is observed, which indicates fast (involving branching chain reactions) ignition of the gas mixture. A conclusion is drawn regarding the common nature of the process of ignition of a combustible gas mixture by a laser spark excited in the reactor volume and the previously investigated initiation of combustion by laser sparks excited at solid targets, high-power microwave discharges, and high-current gliding discharges.

  7. Ultrafast Electron Dynamics in Gold in the Presence of Laser Excited Surface Plasma Waves

    SciTech Connect

    Raynaud, M.

    2010-02-02

    Surface plasmon excitation with ultrashort intense laser pulses enhances efficiently laser absorption in metals and creates local high fields and non-equilibrium hot electrons population that have attractivity for numerous applications such as the development of intense sources of high-energy particles or photons and in the fast ignitor scheme in the framework of inertial fusion. In this context, the knowledge of the dynamics of relaxation of the collective electrons behavior is of importance. Using gold grating, we have investigated electrons relaxation in the presence of laser excited surface plasmon waves using a multiple-wavelengh femtosecond pump-probe technique. The results yield evidence of longer relaxation time in the presence of the collective excitation than that of individual electronic states.

  8. Selective excitation of the OClO molecule with femtosecond laser pulse

    NASA Astrophysics Data System (ADS)

    Yuan, Kai-Jun; Sun, Zhigang; Cong, Shu-Lin; Lou, Nanquan

    2005-11-01

    The three-dimensional time-dependent quantum wave packet dynamics (J=0) using a Hamiltonian for a triatomic molecule in Radau coordinates is employed to study laser pulse excitation of the OClO molecule. The fast Fourier transform (FFT) and the split operator methods are applied to propagate the wave packet. The vibronic excitations AA22(ν1,ν2,ν3)←XB12(0,0,0) of the triatomic molecule OClO using femtosecond laser pulses of varying intensities are investigated. With an ultrashort laser pulse of certain FWHM (full width at half maximum), the vibrational level can be selectively excited. The changes in the vibrational population distributions caused by simple variation of the pulse are remarkable.

  9. Coherent blue emission generated by Rb two-photon excitation using diode and femtosecond lasers

    NASA Astrophysics Data System (ADS)

    Lopez, Jesus P.; Moreno, Marco P.; de Miranda, Marcio H. G.; Vianna, Sandra S.

    2017-04-01

    The coherent blue light generated in rubidium vapor due to the combined action of an ultrashort pulse train and a continuous wave diode laser is investigated. Each step of the two-photon transition 5S–5P{}3/2–5D is excited by one of the lasers, and the induced coherence between the 5S and 6P{}3/2 states is responsible for generating the blue beam. Measurements of the excitation spectrum reveal the frequency comb structure and allow us to identify the resonant modes responsible for inducing the nonlinear process. Further, each resonant mode excites a different group of atoms, making the process selective in atomic velocity. The signal dependency on the atomic density is characterized by a sharp growth and a rapid saturation. We also show that for high intensity of the diode laser, the Stark shift at resonance causes the signal suppression observed at low atomic density.

  10. Fluorescence anisotropy excitation by polarization-shaped laser pulses after transmission through a kagome fiber

    NASA Astrophysics Data System (ADS)

    Otto, J.; Patas, A.; Althoff, J.; Lindinger, A.

    2016-08-01

    We report improved fluorescence contrast between dyes by two-photon excitation with polarization-shaped laser pulses after transmission through a kagome fiber utilizing the anisotropy of the dye molecules. Particularly phase- and polarization-tailored pulse shapes are employed for two-photon excited fluorescence of dyes in a liquid environment at the distal end of the kagome fiber. The distortions due to the optical fiber properties are precompensated in order to receive predefined polarization-shaped laser pulses after the kagome fiber. This enables to optimally excite one dye in one polarization direction and simultaneously the other dye in the other polarization direction. The presented method has a high potential for endoscopic applications due to the unique properties of kagome fibers for guiding ultrashort laser pulses.

  11. Quantum electrodynamical theory of high-efficiency excitation energy transfer in laser-driven nanostructure systems

    NASA Astrophysics Data System (ADS)

    Weeraddana, Dilusha; Premaratne, Malin; Gunapala, Sarath D.; Andrews, David L.

    2016-08-01

    A fundamental theory is developed for describing laser-driven resonance energy transfer (RET) in dimensionally constrained nanostructures within the framework of quantum electrodynamics. The process of RET communicates electronic excitation between suitably disposed emitter and detector particles in close proximity, activated by the initial excitation of the emitter. Here, we demonstrate that the transfer rate can be significantly increased by propagation of an auxiliary laser beam through a pair of nanostructure particles. This is due to the higher order perturbative contribution to the Förster-type RET, in which laser field is applied to stimulate the energy transfer process. We construct a detailed picture of how excitation energy transfer is affected by an off-resonant radiation field, which includes the derivation of second and fourth order quantum amplitudes. The analysis delivers detailed results for the dependence of the transfer rates on orientational, distance, and laser intensity factor, providing a comprehensive fundamental understanding of laser-driven RET in nanostructures. The results of the derivations demonstrate that the geometry of the system exercises considerable control over the laser-assisted RET mechanism. Thus, under favorable conformational conditions and relative spacing of donor-acceptor nanostructures, the effect of the auxiliary laser beam is shown to produce up to 70% enhancement in the energy migration rate. This degree of control allows optical switching applications to be identified.

  12. Infrared planar laser-induced fluorescence imaging and applications to imaging of carbon monoxide and carbon dioxide

    NASA Astrophysics Data System (ADS)

    Kirby, Brian James

    This dissertation introduces infrared planar laser- induced fluorescence (IR PLIF) techniques for visualization of species that lack convenient electronic transitions and are therefore unsuitable for more traditional electronic PLIF measurements. IR PLIF measurements can generate high signal levels that scale linearly with both laser energy and species concentration, thereby demonstrating advantages over Raman and multiphoton PLIF techniques. IR PLIF is shown to be a straightforward and effective tool for visualization of CO and CO2 in reactive flows. The slow characteristic times of vibrational relaxation and the large mole fractions of CO and CO2 in typical flows lead to high IR PLIF signal levels, despite the low emission rates typical of vibrational transitions. Analyses of rotational energy transfer (RET) and vibrational energy transfer (VET) show that excitation schemes in either linear (weak) or saturated (strong) limits may be developed, with the fluorescence collected directly from the laser-excited species or indirectly from bath gases in vibrational resonance with the laser-excited species. Use of short (~1 μs) exposures (for CO) or short exposures combined with long-pulse, high-pulse-energy excitation (for CO2) minimizes unwanted signal variation due to spatially-dependent VET rates. Results are presented for flows ranging from room- temperature mixing to a benchmark CH4 laminar diffusion flame. Linear excitation is appropriate for CO due to its slow vibrational relaxation. However, linear excitation is not well-suited for CO2 imaging due to fast H 2O-enhanced VET processes and the attendant difficulty in interpreting the resulting signal. Saturated excitation using a CO2 laser (or combined CO2 laser-OPO) technique is most appropriate for CO 2, as it generates high signal and minimizes spatial variations in fluorescence quantum yield. Since IR PLIF is applicable to most IR-active species, it has a high potential for expanding the diagnostic

  13. Doping of germanium and silicon crystals with non-hydrogenic acceptors for far infrared lasers

    DOEpatents

    Haller, Eugene E.; Brundermann, Erik

    2000-01-01

    A method for doping semiconductors used for far infrared lasers with non-hydrogenic acceptors having binding energies larger than the energy of the laser photons. Doping of germanium or silicon crystals with beryllium, zinc or copper. A far infrared laser comprising germanium crystals doped with double or triple acceptor dopants permitting the doped laser to be tuned continuously from 1 to 4 terahertz and to operate in continuous mode. A method for operating semiconductor hole population inversion lasers with a closed cycle refrigerator.

  14. A fuzzy automated object classification by infrared laser camera

    NASA Astrophysics Data System (ADS)

    Kanazawa, Seigo; Taniguchi, Kazuhiko; Asari, Kazunari; Kuramoto, Kei; Kobashi, Syoji; Hata, Yutaka

    2011-06-01

    Home security in night is very important, and the system that watches a person's movements is useful in the security. This paper describes a classification system of adult, child and the other object from distance distribution measured by an infrared laser camera. This camera radiates near infrared waves and receives reflected ones. Then, it converts the time of flight into distance distribution. Our method consists of 4 steps. First, we do background subtraction and noise rejection in the distance distribution. Second, we do fuzzy clustering in the distance distribution, and form several clusters. Third, we extract features such as the height, thickness, aspect ratio, area ratio of the cluster. Then, we make fuzzy if-then rules from knowledge of adult, child and the other object so as to classify the cluster to one of adult, child and the other object. Here, we made the fuzzy membership function with respect to each features. Finally, we classify the clusters to one with the highest fuzzy degree among adult, child and the other object. In our experiment, we set up the camera in room and tested three cases. The method successfully classified them in real time processing.

  15. Photoacoustic overtone spectroscopy of liquids with continuous wave laser excitation

    NASA Astrophysics Data System (ADS)

    Manzares, Carlos; I

    1991-06-01

    To study overtone absorptions in condensed phases, a technique is presented which uses a piezoelectric detector, lock-in amplification and a cw dye laser modulated at frequencies from 10 to 120 kHz with an acousto-optic modulator. Acoustic resonance frequencies calculated for a cylindrical cell are observed experimentally using liquid Si(CH 3) 4 as the sample. The acoustic signal is found to be proportional to the laser power. The fifth overtone of the CH streching mode of Si(CH 3) 4 has been recorded pure and in solutions with CCl 4. With a 1% solution of Si(CH 3) 4 in CCl 4, an absorbance of approximately 1 × 10 -5 cm -1 is detected with a dye laser power of 55 mW.

  16. Ab initio non-Born-Oppenheimer simulations of rescattering dissociation of H2 in strong infrared laser fields

    NASA Astrophysics Data System (ADS)

    Li, Zhi-Chao; He, Feng

    2014-11-01

    We simulate the time-dependent Schrödinger equation and observe the rescattering dissociation of H2 in strong infrared laser fields. Two dissociation pathways are identified, i.e., the dissociation of H2+ in the 2 p σu state and the dissociation of H2 in doubly excited states. The former accounts for larger proportions as the rescattering energy is larger. The kinetic energy release of dissociative fragments reflects the temporal internuclear distance at the moment the rescattering happens.

  17. Generation of THz Radiation by Excitation of InAs with a Free Electron Laser

    SciTech Connect

    Mashiko Tani; Shunsuke Kono; Ping Gu; Kiyomi Sakai; Mamoru Usami; Michelle D. Shinn; Joseph F. Gubeli; George Neil; Jingzhou Xu; Roland Kersting; X.-C. Zhang

    2001-01-01

    Terahertz (THz) radiation is generated by exciting an un-doped InAs wafer with a femtosecond free-electron laser (FEL) at the Thomas Jefferson National Accelerator Facility. A microwatt level of THz radiation is detected from the unbiased InAs emitter when it is excited with the femtosecond FEL pulses operated at a wavelength of 1.06 {mu}-m and 10 W average power.

  18. Method and apparatus for secondary laser pumping by electron beam excitation

    DOEpatents

    George, E. Victor; Krupke, William F.; Murray, John R.; Powell, Howard T.; Swingle, James C.; Turner, Jr., Charles E.; Rhodes, Charles K.

    1978-01-01

    An electron beam of energy typically 100 keV excites a fluorescer gas which emits ultraviolet radiation. This radiation excites and drives an adjacent laser gas by optical pumping or photolytic dissociation to produce high efficiency pulses. The invention described herein was made in the course of, or under, United States Energy Research and Development Administration Contract No. W-7405-Eng-48 with the University of California.

  19. Study of excitation transfer in laser dye mixtures by direct measurement of fluorescence lifetime

    NASA Technical Reports Server (NTRS)

    Lin, C.; Dienes, A.

    1973-01-01

    By directly measuring the donor fluorescence lifetime as a function of acceptor concentration in the laser dye mixture Rhodamine 6G-Cresyl violet, we found that the Stern-Volmer relation is obeyed, from which the rate of excitation transfer is determined. The experimental results indicate that the dominant mechanism responsible for the efficient excitation transfer is that of resonance transfer due to long range dipole-dipole interaction.

  20. Near infrared excited micro-Raman spectra of 4:1 methanol-ethanol mixture and ruby fluorescence at high pressure

    NASA Astrophysics Data System (ADS)

    Wang, X. B.; Shen, Z. X.; Tang, S. H.; Kuok, M. H.

    1999-06-01

    Near infrared (NIR) lasers, as a new excitation source for Raman spectroscopy, has shown its unique advantages and is being increasingly used for some special samples, such as those emitting strong fluorescence in the visible region. This article focuses on some issues related to high-pressure micro-Raman spectroscopy using NIR excitation source. The Raman spectra of 4:1 methanol-ethanol mixture (4:1 M-E) show a linear variation in both Raman shifts and linewidths under pressure up to 18 GPa. This result is useful in distinguishing Raman scattering of samples from that of the alcohol mixture, an extensively used pressure-transmitting medium. The R1 fluorescence in the red region induced by two-photon absorption of the NIR laser is strong enough to be used as pressure scale. The frequency and line width of the R1 lines are very sensitive to pressure change and the glass transition of the pressure medium. Our results manifest that it is reliable and convenient to use NIR induced two-photon excited fluorescence of ruby for both pressure calibration and distribution of pressure in the 4:1 M-E pressure transmitting medium.

  1. Quantum cascade semiconductor infrared and far-infrared lasers: from trace gas sensing to non-linear optics.

    PubMed

    Duxbury, Geoffrey; Langford, Nigel; McCulloch, Michael T; Wright, Stephen

    2005-11-01

    The Quantum cascade (QC) laser is an entirely new type of semiconductor device in which the laser wavelength depends on the band-gap engineering. It can be made to operate over a much larger range than lead salt lasers, covering significant parts of both the infrared and submillimetre regions, and with higher output power. In this tutorial review we survey some of the applications of these new lasers, which range from trace gas detection for atmospheric or medical purposes to sub-Doppler and time dependent non-linear spectroscopy.

  2. Turbid Media Extinction Coefficient for Near-Infrared Laser Radiation

    NASA Astrophysics Data System (ADS)

    Dreischuh, T.; Gurdev, L.; Vankov, O.; Stoyanov, D.; Avramov, L.

    2015-03-01

    In this work, extended investigations are performed of the extinction coefficient of Intralipid-20% dilutions in distilled water depending on the Intralipid concentration, for laser radiation wavelengths in the red and near-infrared regions covering the so-called tissue optical window. The extinction is measured by using an approach we have developed recently based on the features of the spatial intensity distribution of laser-radiation beams propagating through semi-infinite turbid media. The measurements are conducted using separately two dilution- containing plexiglass boxes of different sizes and volumes, in order to prove the appropriateness of the assumption of semi-infinite turbid medium. The experimental results for the extinction are in agreement with our previous results and with empiric formulae found by other authors concerning the wavelength dependence of the scattering coefficient of Intralipid - 10% and Intralipid - 20%. They are also in agreement with known data of the water absorptance. It is estimated as well that the wavelengths around 1320 nm would be advantageous for deep harmless sensing and diagnostics of tissues.

  3. Impact of Infrared Lunar Laser Ranging on Lunar Dynamics

    NASA Astrophysics Data System (ADS)

    Viswanathan, Vishnu; Fienga, Agnès; Manche, Hervé; Gastineau, Mickael; Courde, Clément; Torre, Jean-Marie; Exertier, Pierre; Laskar, Jacques; LLR Observers : Astrogeo-OCA, Apache Point, McDonald Laser Ranging Station, Haleakala Observatory, Matera Laser Ranging Observatory

    2016-10-01

    Since 2015, in addition to the traditional green (532nm), infrared (1064nm) has been the preferred wavelength for lunar laser ranging at the Calern lunar laser ranging (LLR) site in France. Due to the better atmospheric transmission of IR with respect to Green, nearly 3 times the number of normal points have been obtained in IR than in Green [ C.Courde et al 2016 ]. In our study, in addition to the historical data obtained from various other LLR sites, we include the recent IR normal points obtained from Calern over the 1 year time span (2015-2016), constituting about 4.2% of data spread over 46 years of LLR. Near even distribution of data provided by IR on both the spatial and temporal domain, helps us to improve constraints on the internal structure of the Moon modeled within the planetary ephemeris : INPOP [ Fienga et al 2015 ]. IERS recommended models have been used in the data reduction software GINS (GRGS,CNES) [ V.Viswanathan et al 2015 ]. Constraints provided by GRAIL, on the Lunar gravitational potential and Love numbers have been taken into account in the least-square fit procedure. New estimates on the dynamical parameters of the lunar core will be presented.

  4. Design study of a laser-cooled infrared sensor

    DOE PAGES

    Hehlen, Markus Peter; Boncher, William Lawrence; Love, Steven Paul

    2015-03-10

    The performance of a solid-state optical refrigerator is the result of a complex interplay of numerous optical and thermal parameters. We present a first preliminary study of an optical cryocooler using ray-tracing techniques. A numerical optimization identified a non-resonant cavity with astigmatism. This geometry offered more efficient pump absorption by the YLF:10%Yb laser-cooling crystal compared to non-resonant cavities without astigmatism that have been pursued experimentally so far. Ray tracing simulations indicate that ~80% of the incident pump light can absorbed for temperatures down to ~100 K. Calculations of heat loads, cooling power, and net payload heat lift are presented. Theymore » show that it is possible to cool a payload to a range of 90–100 K while producing a net payload heat lift of 80 mW and 300 mW when pumping a YLF:10%Yb crystal with 20 W and 50 W at 1020 nm, respectively. This performance is suited to cool HgCdTe infrared detectors that are used for sensing in the 8–12 μm atmospheric window. While the detector noise would be ~6× greater at 100 K than at 77 K, the laser refrigerator would introduce no vibrations and thus eliminate sources of microphonic noise that are limiting the performance of current systems.« less

  5. Design study of a laser-cooled infrared sensor

    SciTech Connect

    Hehlen, Markus Peter; Boncher, William Lawrence; Love, Steven Paul

    2015-03-10

    The performance of a solid-state optical refrigerator is the result of a complex interplay of numerous optical and thermal parameters. We present a first preliminary study of an optical cryocooler using ray-tracing techniques. A numerical optimization identified a non-resonant cavity with astigmatism. This geometry offered more efficient pump absorption by the YLF:10%Yb laser-cooling crystal compared to non-resonant cavities without astigmatism that have been pursued experimentally so far. Ray tracing simulations indicate that ~80% of the incident pump light can absorbed for temperatures down to ~100 K. Calculations of heat loads, cooling power, and net payload heat lift are presented. They show that it is possible to cool a payload to a range of 90–100 K while producing a net payload heat lift of 80 mW and 300 mW when pumping a YLF:10%Yb crystal with 20 W and 50 W at 1020 nm, respectively. This performance is suited to cool HgCdTe infrared detectors that are used for sensing in the 8–12 μm atmospheric window. While the detector noise would be ~6× greater at 100 K than at 77 K, the laser refrigerator would introduce no vibrations and thus eliminate sources of microphonic noise that are limiting the performance of current systems.

  6. Coherent sources for mid-infrared laser spectroscopy

    NASA Astrophysics Data System (ADS)

    Honzátko, Pavel; Baravets, Yauhen; Mondal, Shyamal; Peterka, Pavel; Todorov, Filip

    2016-12-01

    Mid-infrared laser absorption spectroscopy (LAS) is useful for molecular trace gas concentration measurements in gas mixtures. While the gas chromatography-mass spectrometry is still the gold standard in gas analysis, LAS offers several advantages. It takes tens of minutes for a gas mixture to be separated in the capillary column precluding gas chromatography from real-time control of industrial processes, while LAS can measure the concentration of gas species in seconds. LAS can be used in a wide range of applications such as gas quality screening for regulation, metering and custody transfer,1 purging gas pipes to avoid explosions,1 monitoring combustion processes,2 detection and quantification of gas leaks,3 by-products monitoring to provide feedback for the real-time control of processes in petrochemical industry,4 real-time control of inductively coupled plasma etch reactors,5, 6 and medical diagnostics by means of time-resolved volatile organic compound (VOC) analysis in exhaled breath.7 Apart from the concentration, it also permits us to determine the temperature, pressure, velocity and mass flux of the gas under observation. The selectivity and sensitivity of LAS is linked to a very high spectral resolution given by the linewidth of single-frequency lasers. Measurements are performed at reduced pressure where the collisional and Doppler broadenings are balanced. The sensitivity can be increased to ppb and sometimes to ppt ranges by increasing the interaction length in multi-pass gas cells or resonators and also by adopting modulation techniques.8

  7. Switching between ground and excited states by optical feedback in a quantum dot laser diode

    SciTech Connect

    Virte, Martin; Breuer, Stefan; Sciamanna, Marc; Panajotov, Krassimir

    2014-09-22

    We demonstrate switching between ground state and excited state emission in a quantum-dot laser subject to optical feedback. Even though the solitary laser emits only from the excited state, we can trigger the emission of the ground state by optical feedback. We observe recurrent but incomplete switching between the two emission states by variation of the external cavity length in the sub-micrometer scale. We obtain a good qualitative agreement of experimental results with simulation results obtained by a rate equation that accounts for the variations of the feedback phase.

  8. Generation of an ultra-short electrical pulse with width shorter than the excitation laser

    PubMed Central

    Shi, Wei; Wang, Shaoqiang; Ma, Cheng; Xu, Ming

    2016-01-01

    We demonstrate experimentally a rare phenomenon that the width of an electrical response is shorter than that of the excitation laser. In this work, generation of an ultrashort electrical pulse is by a semi-insulating GaAs photoconductive semiconductor switch (PCSS) and the generated electrical pulse width is shorter than that of the excitation laser from diode laser. When the pulse width and energy of the excitation laser are fixed at 25.7 ns and 1.6 μJ respectively, the width of the generated electrical pulse width by 3-mm-gap GaAs PCSS at the bias voltage of 9 kV is only 7.3 ns. The model of photon-activated charge domain (PACD) is used to explain the peculiar phenomenon in our experiment. The ultrashort electrical pulse width is mainly relevant to the time interval of PACD from occurrence to disappearance in the mode. The shorter the time interval is, the narrower the electrical pulse width will become. In more general terms, our result suggests that in nonlinear regime a response signal can have a much short width than the excitation pulses. The result clearly indicates that generating ultrashort electrical pulses can be achieved without the need of ultrashort lasers. PMID:27273512

  9. Excited state absorption of pump radiation as a loss mechanism in solid-state lasers

    SciTech Connect

    Kliewer, M.L.; Powell, R.C.

    1989-08-01

    The characteristics of optical pumping dynamics occurring in laser-pumped rare earth-doped, solid-state laser materials were investigated by using a tunable alexandrite laser to pump Y/sub 3/Al/sub 5/O/sub 12/:Nd/sup 3+/ in an optical cavity. It was found that the slope efficiency of the Nd laser operation depends strongly on the wavelength of the pump laser. For pump wavelengths resulting in low slope efficiencies, intense fluorescence emission is observed from the sample in the blue-green spectral region. This is attributed to the excited state absorption of pump photons which occurs during radiationless relaxation from the pump band to the metastable state. This type of process will be an important loss mechanism for monochromatic pumping of laser systems at specific pump wavelengths.

  10. Excited-state absorption of pump radiation as a loss mechanism in solid-state lasers

    SciTech Connect

    Kliewer, M.L.; Powell, R.C.

    1989-08-01

    The characteristics of optical pumping dynamics occuring in laser-pumped rare earth-doped, solid-state laser materials were investigated by using a tunable alexandrite laser to pump Y3Al5O12:Nd(3+) in an optical cavity. It was found that the slope efficiency of the Nd laser operation depends strongly on the wavelength of the pump laser. For pump wavelength resulting in low slope efficiencies, intense fluorescence emission is observed form the sample in the blue-green spectral region. This is attributed to the excited state absorption of pump photons which occurs during radiationless relaxation from the pump band to the metastable state. This type of process will be an important loss mechanism for monochromatic pumping of laser systems at specific pump wavelengths.

  11. Excited state absorption of pump radiation as a loss mechanism in solid-state lasers

    NASA Technical Reports Server (NTRS)

    Kliewer, Michael L.; Powell, Richard C.

    1989-01-01

    The characteristics of optical pumping dynamics in laser-pumped, rare-earth-doped, solid-state laser materials are investigated by using a tunable alexandrite laser to pump Y3Al5O12:Nd(3+) in an optical cavity. It is found that the slope efficiency of the Nd laser operation depends strongly on the wavelength of the pump laser. For pump wavelengths resulting in low slope efficiencies, intense fluorescence emission is observed from the sample in the blue-green spectral region. This is attributed to the excited-state absorption of pump photons which occurs during radiationless relaxation from the pump band to the metastable state. This type of process is an important loss mechanism for monochromatic pumping of laser systems at specific pump wavelengths.

  12. Investigation of laser radar systems based on mid-infrared semiconductor lasers

    NASA Astrophysics Data System (ADS)

    Rybaltowski, Adam

    This dissertation deals with the possibility of utilizing mid-infrared semiconductor lasers in systems of optical remote sensing with range resolution, called laser radar or lidar. The main subject investigated in this dissertation is two-fold: firstly, an analysis of the signal-to-noise ratio (SNR) and related maximum sensing range calculations in this type of lidar based on available system components, and---secondly---improvements in the Random-Modulation Continuous-Wave (RM-CW) lidar technique to better utilize available mid-infrared semiconductor lasers. As far as the SNR analysis is concerned, an appropriate framework has been constructed to analyze post-demodulation noise in mid-infrared direct-detection RM-CW lidar. It is based on a generalization of the Wiener-Khintchine theorem; noise is assumed to be additive, stationary, and have an arbitrary power spectrum. This is in contrast to the SNR analysis in the literature on this subject, which is inadequate for mid-infrared RM-CW lidar as it only considers Poissonian fluctuations of the number of detected photons. In addition to regular SNR analysis, the framework derived in this dissertation allows treatment of singularities such as demodulation with an unbalanced sequence in 1/f noise. To calculate maximum lidar sensing range, the following detection limits have been considered: signal shot noise, background blackbody radiation shot noise based on the Background-Limited Photodetection (BLIP) detectivity limit, and minimum-size detector noise given by diffraction-limited focusing. The latter is found to be of greatest practical interest. Furthermore, a lidar figure of merit has been introduced, and all quantities related to lidar performance and its detection limits have been presented graphically. Since pseudo-random sequences discussed in the literature have been found highly non-optimal for most applications of RM-CW lidar, a framework for the construction of new pseudo-random sequences of desired

  13. Plasma undulator excited by high-order mode lasers

    NASA Astrophysics Data System (ADS)

    Wang, Jingwei; Rykovanov, Sergey

    2016-10-01

    A laser-created plasma undulator together with a laser-plasma accelerator makes it possible to construct an economical and extremely compact XFEL. However, the spectrum spread of the radiation from the current plasma undulators is too large for XFELs, because of the different values of strength parameters. The phase slippage between the electrons and the wakefield also limits the number of the electron oscillation cycles, thus reduces the performance of XFEL. Here we proposed a phase-locked plasma undulator created by high-order mode lasers. The modulating field is uniform along the transverse direction by choosing appropriate laser intensities of the modes, which enables all the electrons oscillate with the same strength parameter. The plasma density is tapered to lock the phase between the electrons and the wakefield, which signally increases the oscillation cycles. As a result, X-ray radiation with high brightness and narrow bandwidth is generated by injecting a high-energy electron beam into the novel plasma undulator. The beam loading limit indicates that the current of the electron beam could be hundreds of Ampere. These properties imply that such a plasma undulator may have great potential in compact XFELs. This work was supported by the Helmholtz Association (Young Investigator's Group No. VH-NG-1037).

  14. Development of UV-excitable red and near-infrared fluorescent labels and their application for simultaneous multicolor bioimaging by single-wavelength excitation.

    PubMed

    Mizuno, Tetsuya; Umezawa, Keitaro; Shindo, Yutaka; Citterio, Daniel; Oka, Kotaro; Suzuki, Koji

    2013-09-01

    We report a new type of UV-excitable red/NIR-emissive fluorescent dyads (PKF series). Conjugation of a pyrene and a novel bright red/near-infrared (NIR) fluorophore resulted in large quasi-Stokes shift while retaining intense fluorescence emission and sharp spectral bands. Labeling of PKF dyads to biomolecules was performed by means of introduction of a succinimidyl ester. Simultaneous Ca(2+)/albumin dual-color intracellular imaging by PKF in combination with fura-2 (UV-excitable/VIS-emissive Ca(2+) indicator) reveals its usefulness as a new bioimaging tool.

  15. The role of excitation parameters in high repetition-rate N2-TE lasers

    NASA Astrophysics Data System (ADS)

    Kukhlevsky, S. V.; Kozma, L.

    1993-09-01

    We have studied the effects of decreasing the excitation duration on the pulse-repetition-rate (PRR) capabilities of a low-pressure ( P<200 Torr) N2-TE laser. It was found that maximum PRR increases with decreasing duration of the discharge current. PRR as high as 1000 Hz has been obtained in the sealed-off non-flowing regime of laser operation. These findings are adequately explained by the time dependence of the arc-discharge formation.

  16. Frontiers in propulsion research: Laser, matter-antimatter, excited helium, energy exchange thermonuclear fusion

    NASA Technical Reports Server (NTRS)

    Papailiou, D. D. (Editor)

    1975-01-01

    Concepts are described that presently appear to have the potential for propulsion applications in the post-1990 era of space technology. The studies are still in progress, and only the current status of investigation is presented. The topics for possible propulsion application are lasers, nuclear fusion, matter-antimatter annihilation, electronically excited helium, energy exchange through the interaction of various fields, laser propagation, and thermonuclear fusion technology.

  17. Visible and near-infrared excitation spectra from the neptunyl ion doped into a uranyl tetrachloride lattice

    NASA Astrophysics Data System (ADS)

    Barker, Beau J.; Berg, John M.; Kozimor, Stosh A.; Wozniak, Nicholas R.; Wilkerson, Marianne P.

    2016-03-01

    Visible and near-infrared illumination induces 5f-5f and ligand-to-metal charge-transfer (LMCT) transitions of the neptunyl tetrachloride anion in polycrystalline Cs2U(Np)O2Cl4, and results in near-infrared luminescence from the second electronically excited state to the ground state. This photoluminescence is used as a detection method to collect excitation spectra throughout the near-infrared and visible regions. The excitation spectra of LMCT transitions in excitation spectra were identified in previous work. Here the measurement and analysis is extended to include both LMCT and intra-5f transitions. The results manifest variation in structural properties of the neptunium-oxo bond among the low-lying electronic states. Vibronic intensity patterns and energy spacings are used to compare bond lengths and vibrational frequencies in the excited states, confirming significant characteristic differences between those excited by 5f-5f transitions from those due to LMCT transitions. Results are compared with recently published RASPT2/SO calculations of [NpO2Cl4]2-.

  18. Terahertz emission from biased conjugated polymers excited by femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Unuma, Takeya; Yamada, Naruki; Kishida, Hideo

    2016-12-01

    We perform terahertz emission spectroscopy to investigate the ultrafast motion of electrons and holes in conjugated polymer films excited by femtosecond laser pulses under in-plane bias electric field. The terahertz waveforms are found to exhibit not the features of free carrier acceleration along bias electric field but a characteristic shape reproduced well by the second time derivative of a delta-function-like polarization. Linear-to-quadratic relations between the terahertz emission amplitude and the excitation intensity are observed for three different conjugated polymers, indicating that the polarization is created by either exciton formation or optical rectification involving two-step excitation via localized states.

  19. Laser excited fluorescence in the cesium-xenon excimer and the cesium dimer

    NASA Technical Reports Server (NTRS)

    Exton, R. J.; Snow, W. L.; Hillard, M. E.

    1978-01-01

    Argon ion laser lines are used to excite fluorescence in a mixture of cesium and xenon. Excimer band fluorescence is observed at higher pressures (about 1 atm) while at lower pressures (several torr) a diffuse fluorescence due to the cesium dimer is observed whose character changes with exciting wavelength. The excimer fluorescence is shown to be directly related to the location of the exciting wavelength within previously measured Cs/Xe line shapes. This fact suggests that the excimer systems may be efficiently pumped through these line shapes. Qualitative energy-level schemes are proposed to explain the observations in both the excimer and dimer systems.

  20. High-Quality-Factor Mid-Infrared Toroidal Excitation in Folded 3D Metamaterials.

    PubMed

    Liu, Zhe; Du, Shuo; Cui, Ajuan; Li, Zhancheng; Fan, Yuancheng; Chen, Shuqi; Li, Wuxia; Li, Junjie; Gu, Changzhi

    2017-02-22

    With unusual electromagnetic radiation properties and great application potentials, optical toroidal moments have received increasing interest in recent years. 3D metamaterials composed of split ring resonators with specific orientations in micro-/nanoscale are a perfect choice for toroidal moment realization in optical frequency considering the excellent magnetic confinement and quality factor, which, unfortunately, are currently beyond the reach of existing micro-/nanofabrication techniques. Here, a 3D toroidal metamaterial operating in mid-infrared region constructed by metal patterns and dielectric frameworks is designed, by which high-quality-factor toroidal resonance is observed experimentally. The toroidal dipole excitation is confirmed numerically and further demonstrated by phase analysis. Furthermore, the far-field radiation intensity of the excited toroidal dipoles can be adjusted to be predominant among other multipoles by just tuning the incident angle. The related processing method expands the capability of focused ion beam folding technologies greatly, especially in 3D metamaterial fabrication, showing great flexibility and nanoscale controllability on structure size, position, and orientation.

  1. Dielectric function for a model of laser-excited GaAs

    SciTech Connect

    Benedict, Lorin X.

    2001-02-15

    We consider a model for the ultrashort pulsed-laser excitation of GaAs in which electrons are excited from the top of the valence band to the bottom of the conduction band. The linear optical response of this excited system in the visible and near-UV is calculated by solving a statically screened Bethe-Salpeter equation. Single-particle electron energies and wave functions are taken from ab initio electronic structure calculations. The screened electron-hole interaction W is calculated with a model dielectric function which includes the excited carriers. Though band-gap renormalization is neglected, dramatic changes are observed in the shape of {epsilon}{sub 2}({omega}) due to Pauli blocking and the enhanced screening of W. We estimate the error incurred in the static screening approximation by performing static screening calculations with the assumption that the excited carriers respond too slowly to screen W.

  2. Three-photon resonant atomic excitation in spatially incoherent laser beams

    SciTech Connect

    Peet, Victor; Shchemeljov, Sergei

    2003-10-01

    Two-color excitation by spatially coherent and incoherent laser beams has been used to study three-photon-resonant excitation and subsequent ionization of xenon in conditions, when internally generated sum-frequency field plays an important role in excitation of atomic resonances through interfering one-photon excitation pathway. We show that the incoherence in one of the pumping fields reduces the efficiency of generated sum-frequency field, and thus suppresses the interference between the three- and the one-photon excitation channels. The degree of suppression is controlled by varying the crossing angle between coherent and incoherent laser beams. We show that ionization profiles can be analyzed on the basis of the well-studied interference of one- and three-photon transition amplitudes, but with pumping field decomposed into multiple small-scale uncorrelated domains where coherent process of four-wave mixing occurs. The gain length for a coherent process in these domains depends on the coherence degree and excitation geometry. It gives a possibility of controlling the contribution of coherent processes to the excitation of multiphoton resonances.

  3. A comparative study of experimental and finite element analysis on submillimeter flaws by laser and ultrasonic excited thermography

    NASA Astrophysics Data System (ADS)

    Zhang, Hai; Fernandes, Henrique; Yu, Lingyao; Hassler, Ulf; Genest, Marc; Robitaille, François; Joncas, Simon; Sheng, Yunlong; Maldague, Xavier

    2016-05-01

    Stitching is used to reduce dry-core and reinforce T-joint structure. However, it might cause new types of flaws, especially submillimeter flaws. In this paper, new approaches including micro-VT, lock-in micro-LLT and micro-LST based on both lock-in and pulse methods are used to detect submillimeter flaws in stitched CFRP. A comparison of laser excitation thermography and micro-VT on micro-porosities is conducted. Micro-CT is used to validate the infrared results. Then, a finite element analysis (FEA) is performed. The geometrical model needed for finite element discretization was developed from micro-CT measurements. The model is validated for the experimental results. Finally a comprehensive experimental and simulation comparison of micro-LLT and micro-LST based on both lock-in and pulse methods is conducted.

  4. Near-infrared (808 and 980 nm) excited photoluminescence study in Nd-doped Y2O3 phosphor for bio-imaging

    NASA Astrophysics Data System (ADS)

    Prasad Sukul, Prasenjit; Kumar, Kaushal

    2016-12-01

    The upconversion (UC) process in lanthanide-doped nanophosphors has attracted great research interest for its extensive application potential in biological in vitro and in vivo imaging due to the high tissue penetration depth of near-infrared excitation and low autofluorescence background. In this article, the authors report the synthesis of oxide nanophosphor of size  ⩽50 nm, which forms stable aqueous dispersion. The photoluminescence study is made on the nanophosphor upon 808 and 980 nm diode laser excitations. The 808 nm excitation resulted in strong emission at 795 nm due to the 4K13/2  →  4I13/2 transition along with other emissions from the Nd3+ ion. The 980 nm excitation has resulted in it turning green in the 525-560 nm range and is assigned to the 4S3/2  →  4I15/2 transition of the Er3+ ion, which is supposed to be present in a trace amount in the sample. The observation of strong UC emission indicates that the sample can be used for UC-based bio-imaging applications.

  5. Mid-infrared photothermal heterodyne spectroscopy in a liquid crystal using a quantum cascade laser

    PubMed Central

    Mërtiri, Alket; Jeys, Thomas; Liberman, Vladimir; Hong, M. K.; Mertz, Jerome; Altug, Hatice; Erramilli, Shyamsunder

    2012-01-01

    We report a technique to measure the mid-infrared photothermal response induced by a tunable quantum cascade laser in the neat liquid crystal 4-octyl-4′-cyanobiphenyl (8CB), without any intercalated dye. Heterodyne detection using a Ti:sapphire laser of the response in the solid, smectic, nematic and isotropic liquid crystal phases allows direct detection of a weak mid-infrared normal mode absorption using an inexpensive photodetector. At high pump power in the nematic phase, we observe an interesting peak splitting in the photothermal response. Tunable lasers that can access still stronger modes will facilitate photothermal heterodyne mid-infrared vibrational spectroscopy. PMID:22912508

  6. Pumping laser excited spins through MgO barriers

    NASA Astrophysics Data System (ADS)

    Martens, Ulrike; Walowski, Jakob; Schumann, Thomas; Mansurova, Maria; Boehnke, Alexander; Huebner, Torsten; Reiss, Günter; Thomas, Andy; Münzenberg, Markus

    2017-04-01

    We present a study of the tunnel magneto-Seebeck (TMS)4 effect in MgO based magnetic tunnel junctions (MTJs). The electrodes consist of CoFeB with in-plane magnetic anisotropy. The temperature gradients which generate a voltage across the MTJs layer stack are created using laser heating. Using this method, the temperature can be controlled on the micrometer length scale: here, we investigate, how both, the TMS voltage and the TMS effect, depend on the size, position and intensity of the applied laser spot. For this study, a large variety of different temperature distributions was created across the junction. We recorded 2D maps of voltages generated by heating in dependence of the laser spot position and the corresponding calculated TMS values. The voltages change in value and sign, from large positive values when heating the MTJ directly in the centre to small values when heating the junction on the edges and even small negative values when heating the sample away from the junction. Those zero crossings lead to very high calculated TMS ratios. Our systematic analysis shows, that the distribution of the temperature gradient is essential, to achieve high voltage signals and reasonable resulting TMS ratios. Furthermore, artefacts on the edges produce misleading results, but also open up further possibilities of more complex heating scenarios for spincaloritronics in spintronic devices.

  7. Tandem ion mobility spectrometry coupled to laser excitation

    SciTech Connect

    Simon, Anne-Laure; Choi, Chang Min; Clavier, Christian; Barbaire, Marc; Maurelli, Jacques; Dagany, Xavier; MacAleese, Luke; Dugourd, Philippe; Chirot, Fabien

    2015-09-15

    This manuscript describes a new experimental setup that allows to perform tandem ion mobility spectrometry (IMS) measurements and which is coupled to a high resolution time-of-flight mass spectrometer. It consists of two 79 cm long drift tubes connected by a dual ion funnel assembly. The setup was built to permit laser irradiation of the ions in the transfer region between the two drift tubes. This geometry allows selecting ions according to their ion mobility in the first drift tube, to irradiate selected ions, and examine the ion mobility of the product ions in the second drift tube. Activation by collision is possible in the same region (between the two tubes) and between the second tube and the time-of-flight. IMS-IMS experiments on Ubiquitin are reported. We selected a given isomer of charge state +7 and explored its structural rearrangement following collisional activation between the two drift tubes. An example of IMS-laser-IMS experiment is reported on eosin Y, where laser irradiation was used to produce radical ions by electron photodetachment starting from doubly deprotonated species. This allowed measuring the collision cross section of the radical photo-product, which cannot be directly produced with an electrospray source.

  8. The Development of Diode Laser Infrared Absorption Spectroscopy as a Plasma Diagnostic.

    NASA Astrophysics Data System (ADS)

    McClain, Robert Leslie

    A high resolution infrared spectrometer based on a tunable lead salt diode laser has been interfaced to both a DC glow discharge and to the downstream region of an ECR plasma etcher. In each case high sensitivity is achieved by multi-passing the infrared beam, using a Herriott type optical arrangement consisting of two facing spherical mirrors. In the DC discharge a 1 m long by 15 cm diameter section of the positive column is sampled using typically 42 passes between 10 cm mirrors roughly 2 m apart. In the ECR device a region approximately 50 cm downstream from the ECR layer of a 0-1 kW ASTeX source is sampled. Effective path lengths of about 9 m are achieved with 30 passes. The abundance of CF_2 in discharges of CF_4 and mixtures of CF _4 and either 0_2 or CHF_3 has been obtained by measuring the fractional absorption in several rotational lines of the upsilon_3 band (asymmetric stretch) near 1095 cm^{-1} (9.1 mu). Rotational temperatures are determined only approximately, but are close to room temperature as expected. The derived concentration of CF_2 is 1.75 times 10^{11} cm ^{-3} in a CF_4 plasma in the ECR etcher at 800 W excitation and 2 mTorr pressure, while in the DC discharge positive column at 20 mTorr and 40 mA it is 1.11 times 10^{12} cm^ {-3}. Dependence on pressure and excitation has been determined over a limited range. In the ECR etcher, the concentration of CF_3 has been determined from the measured fractional absorption of a selected R-branch transition of the upsilon _3 band at 1266.714 cm^{ -1}. The density is 9.5 times 10^{11} cm ^{-3} in a CF_4 plasma at 2 mTorr and 800 W. The CF_3 density has also been monitored over a limited range of excitation power, pressure, and gas composition. Absorption lines of the parent species CF_4 are also easily observed and followed, and those of the polymerization product C_2F _6 were detected in the DC discharge. In the ECR plasma, which uses a quartz liner in the source to mitigate sputtering, strong

  9. Pyroelectricity Assisted Infrared-Laser Desorption Ionization (PAI-LDI) for Atmospheric Pressure Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Li, Yanyan; Ma, Xiaoxiao; Wei, Zhenwei; Gong, Xiaoyun; Yang, Chengdui; Zhang, Sichun; Zhang, Xinrong

    2015-08-01

    A new atmospheric pressure ionization method termed pyroelectricity-assisted infrared laser desorption ionization (PAI-LDI) was developed in this study. The pyroelectric material served as both sample target plate and enhancing ionization substrate, and an IR laser with wavelength of 1064 nm was employed to realize direct desorption and ionization of the analytes. The mass spectra of various compounds obtained on pyroelectric material were compared with those of other substrates. For the five standard substances tested in this work, LiNbO3 substrate produced the highest ion yield and the signal intensity was about 10 times higher than that when copper was used as substrate. For 1-adamantylamine, as low as 20 pg (132.2 fmol) was successfully detected. The active ingredient in (Compound Paracetamol and 1-Adamantylamine Hydrochloride Capsules), 1-adamantylamine, can be sensitively detected at an amount as low as 150 pg, when the medicine stock solution was diluted with urine. Monosaccharide and oligosaccharides in Allium Cepa L. juice was also successfully identified with PAI-LDI. The method did not require matrix-assisted external high voltage or other extra facility-assisted set-ups for desorption/ionization. This study suggested exciting application prospect of pyroelectric materials in matrix- and electricity-free atmospheric pressure mass spectrometry research.

  10. Chemical and explosive detection with long-wave infrared laser induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Jin, Feng; Trivedi, Sudhir B.; Yang, Clayton S.; Brown, Ei E.; Kumi-Barimah, Eric; Hommerich, Uwe H.; Samuels, Alan C.

    2016-05-01

    Conventional laser induced breakdown spectroscopy (LIBS) mostly uses silicon-based detectors and measures the atomic emission in the UV-Vis-NIR (UVN) region of the spectrum. It can be used to detect the elements in the sample under test, such as the presence of lead in the solder for electronics during RoHS compliance verification. This wavelength region, however, does not provide sufficient information on the bonding between the elements, because the molecular vibration modes emit at longer wavelength region. Measuring long-wave infrared spectrum (LWIR) in a LIBS setup can instead reveal molecular composition of the sample, which is the information sought in applications including chemical and explosive detection and identification. This paper will present the work and results from the collaboration of several institutions to develop the methods of LWIR LIBS for chemical/explosive/pharmaceutical material detection/identification, such as DMMP and RDX, as fast as using a single excitation laser pulse. In our latest LIBS setup, both UVN and LWIR spectra can be collected at the same time, allowing more accurate detection and identification of materials.

  11. Femtosecond transient infrared and stimulated Raman spectroscopy shed light on the relaxation mechanisms of photo-excited peridinin

    NASA Astrophysics Data System (ADS)

    Di Donato, Mariangela; Ragnoni, Elena; Lapini, Andrea; Foggi, Paolo; Hiller, Roger G.; Righini, Roberto

    2015-06-01

    By means of one- and two-dimensional transient infrared spectroscopy and femtosecond stimulated Raman spectroscopy, we investigated the excited state dynamics of peridinin, a carbonyl carotenoid occurring in natural light harvesting complexes. The presence of singly and doubly excited states, as well as of an intramolecular charge transfer (ICT) state, makes the behavior of carbonyl carotenoids in the excited state very complex. In this work, we investigated by time resolved spectroscopy the relaxation of photo-excited peridinin in solvents of different polarities and as a function of the excitation wavelength. Our experimental results show that a characteristic pattern of one- and two-dimensional infrared bands in the C=C stretching region allows monitoring the relaxation pathway. In polar solvents, moderate distortions of the molecular geometry cause a variation of the single/double carbon bond character, so that the partially ionic ICT state is largely stabilized by the solvent reorganization. After vertical photoexcitation at 400 nm of the S2 state, the off-equilibrium population moves to the S1 state with ca. 175 fs time constant; from there, in less than 5 ps, the non-Franck Condon ICT state is reached, and finally, the ground state is recovered in 70 ps. That the relevant excited state dynamics takes place far from the Franck Condon region is demonstrated by its noticeable dependence on the excitation wavelength.

  12. Femtosecond transient infrared and stimulated Raman spectroscopy shed light on the relaxation mechanisms of photo-excited peridinin.

    PubMed

    Di Donato, Mariangela; Ragnoni, Elena; Lapini, Andrea; Foggi, Paolo; Hiller, Roger G; Righini, Roberto

    2015-06-07

    By means of one- and two-dimensional transient infrared spectroscopy and femtosecond stimulated Raman spectroscopy, we investigated the excited state dynamics of peridinin, a carbonyl carotenoid occurring in natural light harvesting complexes. The presence of singly and doubly excited states, as well as of an intramolecular charge transfer (ICT) state, makes the behavior of carbonyl carotenoids in the excited state very complex. In this work, we investigated by time resolved spectroscopy the relaxation of photo-excited peridinin in solvents of different polarities and as a function of the excitation wavelength. Our experimental results show that a characteristic pattern of one- and two-dimensional infrared bands in the C=C stretching region allows monitoring the relaxation pathway. In polar solvents, moderate distortions of the molecular geometry cause a variation of the single/double carbon bond character, so that the partially ionic ICT state is largely stabilized by the solvent reorganization. After vertical photoexcitation at 400 nm of the S2 state, the off-equilibrium population moves to the S1 state with ca. 175 fs time constant; from there, in less than 5 ps, the non-Franck Condon ICT state is reached, and finally, the ground state is recovered in 70 ps. That the relevant excited state dynamics takes place far from the Franck Condon region is demonstrated by its noticeable dependence on the excitation wavelength.

  13. Ultrahigh-gradient acceleration of injected eletrons by laser-excited relativistic electron plasma waves

    NASA Astrophysics Data System (ADS)

    Clayton, C. E.; Marsh, K. A.; Dyson, A.; Everett, M.; Lal, A.; Leemans, W. P.; Williams, R.; Joshi, C.

    1993-01-01

    High-gradient acceleration of externally injected 2.1-MeV electrons by a laser beat wave driven relativistic plasma wave has been demonstrated for the first time. Electrons with energies up to the detection limit of 9.1 MeV were detected when such a plasma wave was resonantly excited using a two-frequency laser. This implies a gradient of 0.7 GeV/m, corresponding to a plasma-wave amplitude of more than 8%. The electron signal was below detection threshold without injection or when the laser was operated on a single frequency.

  14. Excitation of silicon microspheres resonances with femtosecond laser fabricated glass waveguides

    NASA Astrophysics Data System (ADS)

    Ćirkinoǧlu, Hüseyin Ozan; Gökay, Ulaş Sabahattin; Serpengüzel, Ali; Sotillo, Belén.; Bharadwaj, Vibhav; Eaton, Shane M.; Ramponi, Roberta

    2016-09-01

    Optical waveguides were fabricated with femtosecond pulsed lasers on glass and characterized by transmission measurements. Glass waveguides were later used for excitation of the whispering gallery modes in a silicon microsphere. The coupling between the silicon microsphere and the femtosecond laser inscribed optical waveguide was simulated in both 90° elastic scattering and 0° transmission spectra. The silicon microsphere whispering gallery modes are available for both in the transverse electric and transverse magnetic polarizations with a spectral mode spacing of 0.25 nm. Optical resonances on silicon microsphere integrated with femtosecond laser written optical waveguides may lead to future quantum optical communication devices.

  15. Laser-Induced Fluorescence in Gaseous [I[subscript]2] Excited with a Green Laser Pointer

    ERIC Educational Resources Information Center

    Tellinghuisen, Joel

    2007-01-01

    A green laser pointer could be used in a flashy demonstration of laser-induced fluorescence in the gas phase by directing the beam of the laser through a cell containing [I[subscript]2] at its room temperature vapor pressure. The experiment could be used to provide valuable insight into the requirements for laser-induced fluorescence (LIF) and the…

  16. Raman Laser Spectrometer internal Optical Head current status: opto-mechanical redesign to minimize the excitation laser trace

    NASA Astrophysics Data System (ADS)

    Sanz, Miguel; Ramos, Gonzalo; Moral, Andoni; Pérez, Carlos; Belenguer, Tomás; del Rosario Canchal, María; Zuluaga, Pablo; Rodriguez, Jose Antonio; Santiago, Amaia; Rull, Fernando; Instituto Nacional de Técnica Aeroespacial (INTA), Universidad de Valladolid (UVa), Ingeniería de Sistemas para la Defesa de España S.A. (ISDEFE)

    2016-10-01

    Raman Laser Spectrometer (RLS) is the Pasteur Payload instruments of the ExoMars mission, within the ESA's Aurora Exploration Programme, that will perform for the first time in an out planetary mission Raman spectroscopy. RLS is composed by SPU (Spectrometer Unit), iOH (Internal Optical Head), and ICEU (Instrument Control and Excitation Unit). iOH focuses the excitation laser on the samples (excitation path), and collects the Raman emission from the sample (collection path, composed on collimation system and filtering system). The original design presented a high laser trace reaching to the detector, and although a certain level of laser trace was required for calibration purposes, the high level degrades the Signal to Noise Ratio confounding some Raman peaks.The investigation revealing that the laser trace was not properly filtered as well as the iOH opto-mechanical redesign are reported on. After the study of the Long Pass Filters Optical Density (OD) as a function of the filtering stage to the detector distance, a new set of filters (Notch filters) was decided to be evaluated. Finally, and in order to minimize the laser trace, a new collection path design (mainly consisting on that the collimation and filtering stages are now separated in two barrels, and on the kind of filters to be used) was required. Distance between filters and collimation stage first lens was increased, increasing the OD. With this new design and using two Notch filters, the laser trace was reduced to assumable values, as can be observed in the functional test comparison also reported on this paper.

  17. Infrared Pulse-laser Long-path Absorption Measurement of Carbon Dioxide Using a Raman-shifted Dye Laser

    NASA Technical Reports Server (NTRS)

    Minato, Atsushi; Sugimoto, Nobuo; Sasano, Yasuhiro

    1992-01-01

    A pulsed laser source is effective in infrared laser long-path absorption measurements when the optical path length is very long or the reflection from a hard target is utilized, because higher signal-to-noise ratio is obtained in the detection of weak return signals. We have investigated the performance of a pulse-laser long-path absorption system using a hydrogen Raman shifter and a tunable dye laser pumped by a Nd:YAG laser, which generates second Stokes radiation in the 2-micron region.

  18. Selective mode excitation in finite size plasma crystals by diffusely reflected laser light

    SciTech Connect

    Schablinski, Jan; Block, Dietmar

    2015-02-15

    The possibility to use diffuse reflections of a laser beam to exert a force on levitating dust particles is studied experimentally. Measurements and theoretical predictions are found to be in good agreement. Further, the method is applied to test the selective excitation of breathing-like modes in finite dust clusters.

  19. Computer simulation of effect of conditions on discharge-excited high power gas flow CO laser

    NASA Astrophysics Data System (ADS)

    Ochiai, Ryo; Iyoda, Mitsuhiro; Taniwaki, Manabu; Sato, Shunichi

    2017-01-01

    The authors have developed the computer simulation codes to analyze the effect of conditions on the performances of discharge excited high power gas flow CO laser. The six be analyzed. The simulation code described and executed by Macintosh computers consists of some modules to calculate the kinetic processes. The detailed conditions, kinetic processes, results and discussions are described in this paper below.

  20. Single photon excimer laser photodissociation of highly vibrationally excited polyatomic molecules

    SciTech Connect

    Tiee, J.J.; Wampler, F.B.; Rice, W.W.

    1980-01-01

    The ir + uv photodissociation of SF/sub 6/ has been performed using CO/sub 2/ and ArF lasers. The two-color photolysis significantly enhances the photodissociation process over ArF irradiation alone and is found to preserve the initial isotopic specificity of the ir excitation process.

  1. Fast infrared chemical imaging with a quantum cascade laser.

    PubMed

    Yeh, Kevin; Kenkel, Seth; Liu, Jui-Nung; Bhargava, Rohit

    2015-01-06

    Infrared (IR) spectroscopic imaging systems are a powerful tool for visualizing molecular microstructure of a sample without the need for dyes or stains. Table-top Fourier transform infrared (FT-IR) imaging spectrometers, the current established technology, can record broadband spectral data efficiently but requires scanning the entire spectrum with a low throughput source. The advent of high-intensity, broadly tunable quantum cascade lasers (QCL) has now accelerated IR imaging but results in a fundamentally different type of instrument and approach, namely, discrete frequency IR (DF-IR) spectral imaging. While the higher intensity of the source provides a higher signal per channel, the absence of spectral multiplexing also provides new opportunities and challenges. Here, we couple a rapidly tunable QCL with a high performance microscope equipped with a cooled focal plane array (FPA) detector. Our optical system is conceptualized to provide optimal performance based on recent theory and design rules for high-definition (HD) IR imaging. Multiple QCL units are multiplexed together to provide spectral coverage across the fingerprint region (776.9 to 1904.4 cm(-1)) in our DF-IR microscope capable of broad spectral coverage, wide-field detection, and diffraction-limited spectral imaging. We demonstrate that the spectral and spatial fidelity of this system is at least as good as the best FT-IR imaging systems. Our configuration provides a speedup for equivalent spectral signal-to-noise ratio (SNR) compared to the best spectral quality from a high-performance linear array system that has 10-fold larger pixels. Compared to the fastest available HD FT-IR imaging system, we demonstrate scanning of large tissue microarrays (TMA) in 3-orders of magnitude smaller time per essential spectral frequency. These advances offer new opportunities for high throughput IR chemical imaging, especially for the measurement of cells and tissues.

  2. Assessment of Excitation Mechanisms and Temporal Dependencies of Infrared Radiation from Vibrationally Excited Carbon Monoxide and Ozone in EXCEDE Experiments.

    DTIC Science & Technology

    1987-03-31

    2.2.2 Dissociative Excitation of Carbon Dioxide .. ..... .. 15 2.2.3 Vibrational Exchange with N2(v). .... ....... .. 18 2.2.4 Quenching of Metastable...Excitation of Carbon Dioxide As shown in Figures 1-2 and 2-2 the ambient CO2 concentration exceeds that of CO by about a factor of 3 at 100 kin, equals the...ASSESSEMENT OF EXCITATION MECHANSIMS AND TEMPORAL DEPENDENCIES OF INFRAREO RADIATION FROM VIBbRATIONALLY EXCITEO CARBON MONOXIDE AND OZONE IN EXCEDE

  3. Feasibility study: Monodisperse polymer particles containing laser-excitable dyes

    NASA Technical Reports Server (NTRS)

    Venkateswarlu, Putcha; He, K. X.; Sharma, A.

    1993-01-01

    The optical properties associated with small particles, which include aerosols, hydrosols and solid microspheres have an impact on several areas of science and engineering. Since the advent of high-speed computers and lasers, the interaction of light with matter in the form of small particles with a discontinuous optical boundary relative to the surroundings has been much better understood. Various nonlinear optical effects have been observed involving interaction of a laser beam with both solid microspheres and liquid microdroplets. These include observation of second and third harmonic generation, four wave mixing, optical visibility, two photon absorption, observation of stimulated emission and lasing, and Stimulated Raman Scattering. Many of these effects are observed with laser intensities which are orders of magnitude less than that required by threshold condition for interactions in macroscopic bulk medium. The primary reason for this is twofold. The front surface of the microsphere acts as a thick lens to enhance the internal intensity of the input laser radiation, and the spherical shape of the droplet acts as an optical cavity to provide feedback at specific wavelengths corresponding to the whispering gallery modes or the morphology dependent resonances (MDR's). The most interesting and significant recent finding in this field is undoubtedly the existence of resonance peaks in linear and nonlinear optical spectra. Such resonance peaks are only dependent on the particle morphology, which means the size, shape and refractive index of the particle. Because of the simultaneous presence of these resonances, they have been referred to by many names, including structural resonances, whispering modes or whispering gallery modes, creeping waves, circumferential waves, surfaces modes, and virtual modes. All of these names refer to the same phenomena, i.e. morphology dependent resonances (MDR's) which has already been described and predicted precisely by

  4. Fiber laser pumped high power mid-infrared laser with picosecond pulse bunch output.

    PubMed

    Wei, Kaihua; Chen, Tao; Jiang, Peipei; Yang, Dingzhong; Wu, Bo; Shen, Yonghang

    2013-10-21

    We report a novel quasi-synchronously pumped PPMgLN-based high power mid-infrared (MIR) laser with picosecond pulse bunch output. The pump laser is a linearly polarized MOPA structured all fiberized Yb fiber laser with picosecond pulse bunch output. The output from a mode-locked seed fiber laser was directed to pass through a FBG reflector via a circulator to narrow the pulse duration from 800 ps to less than 50 ps and the spectral FWHM from 9 nm to 0.15 nm. The narrowed pulses were further directed to pass through a novel pulse multiplier through which each pulse was made to become a pulse bunch composing of 13 sub-pulses with pulse to pulse time interval of 1.26 ns. The pulses were then amplified via two stage Yb fiber amplifiers to obtain a linearly polarized high average power output up to 85 W, which were then directed to pass through an isolator and to pump a PPMgLN-based optical parametric oscillator via quasi-synchronization pump scheme for ps pulse bunch MIR output. High MIR output with average power up to 4 W was obtained at 3.45 micron showing the feasibility of such pump scheme for ps pulse bunch MIR output.

  5. Nonlinear femtosecond near infrared laser structuring in oxide glasses

    NASA Astrophysics Data System (ADS)

    Royon, Arnaud

    Three-dimensional femtosecond laser structuring has a growing interest because of its ease of implementation and the numerous possible applications in the domain of photonic components. Structures such as waveguides, diffraction gratings, optical memories or photonic crystals can be fabricated thanks to this technique. Its use with oxide glasses is promising because of several advantages; they are resistant to flux and ageing, their chemical composition can easily be changed to fit the well-defined requirements of an application. They can already be found in Raman amplifiers, optical fibers, fiber lasers, and other devices. This thesis is based on two axes. The first axis consists in characterizing the linear and nonlinear optical properties of bulk vitreous materials in order to optimize their composition with a particular application in view. Within this context, the nonlinear optical properties, their physical origins (electronic and nuclear) as well as their characteristic response times (from a few femtoseconds to a few hundreds of picoseconds) are described within the Born-Oppenheimer approximation. Fused silica and several sodium-borophosphate glasses containing different concentrations in niobium oxide have been studied. Results show that the nonlinear optical properties of fused silica are mainly from electronic origin, whereas in the sodium-borophosphate glasses, the contribution from nuclear origin becomes predominant when the concentration of niobium oxide exceeds 30%. The second axis is based on the structuring of materials. Three commercially available fused silica samples presenting different fabrication conditions (therefore distinct impurity levels) and irradiated with a near infrared femtosecond laser have been studied. The laser induced defects have been identified by means of several spectroscopic techniques. They show the formation of color centers as well as a densification inside the irradiated area. Their linear refractive index and

  6. Photo-ionization and photo-excitation of curcumin investigated by laser flash photolysis.

    PubMed

    Qian, Tingting; Kun, Li; Gao, Bo; Zhu, Rongrong; Wu, Xianzheng; Wang, Shilong

    2013-12-01

    Curcumin (Cur) has putative antitumor properties. In the current study, we examined photophysical and photochemical properties of Cur using laser flash photolysis. The results demonstrated that Cur could be photo-ionized at 355 nm laser pulse to produce radical cation (Cur(+)) and solvated electron e(sol)(-) in 7:3 ethanol-water mixtures. The quantum yield of Cur photo-ionization and the ratio of photo-ionization to photo-excitation were also determined. Cur(+) could be transferred into neutral radical of Cur (Cur) via deprotonation with the pKa 4.13. The excited singlet of Cur ((1)Cur* could be transferred into excited triplet ((3)Cur*, which could be quenched by oxygen to produce singlet oxygen (1)O2*. Reaction of (3)Cur* with tryptophan was confirmed. The results encourage developing curcumin as a photosensitive antitumor agent.

  7. CO/sub 2/ dissociation in sealed rf-excited CO/sub 2/ waveguide lasers

    SciTech Connect

    McArthur, B.A.; Tulip, J.

    1988-05-01

    A mass spectrometer has been used to study the gas composition in a sealed rf-excited CO/sub 2/ waveguide laser during operation. CO/sub 2/ dissociation levels, at 53% to 71%, are similar to those reported for dc-excited waveguide lasers and substantiate prior measurements on rf-excited discharges. The degree of dissociation decreases with increasing pressure and xenon content, but increases as the proportion of helium in the gas mixture is increased. Dissociation has been found to be insensitive to the rf input power per unit discharge length over the range of 2.7 to 4.7 W/cm. This is believed to be the result of increased rates of water vapor outgassing at higher input power levels.

  8. Estimation of ground and excited state dipole moments of some laser dyes

    NASA Astrophysics Data System (ADS)

    Biradar, D. S.; Siddlingeshwar, B.; Hanagodimath, S. M.

    2008-03-01

    The ground state ( μg) and the excited state ( μe) dipole moments of three laser dyes namely 2, 5-diphenyl-1, 3, 4- oxadiazole (PPD), 2, 2″-dimethyl-p-terphenyl (DMT) and 1, 3-diphenyl benzene (MT) were studied at room temperature in various solvents. The ground state dipole moments ( μg) of all the three laser dyes were determined experimentally by Guggenheim method. The excited state dipole moments ( μe) were estimated from Lippert's, Bakshiev's and Chamma Viallet's equations by using the variation of the Stokes shift with the solvent dielectric constant and refractive index. Ground and excited state dipole moments were evaluated by means of solvatochromic shift method and also the excited state dipole moments are determined in combination with ground state dipole moments. It was observed that dipole moment values of excited states ( μe) were higher than corresponding ground state values ( μg), indicating a substantial redistribution of the π-electron densities in a more polar excited state for all the dyes investigated.

  9. Time of flight emission spectroscopy of laser produced nickel plasma: Short-pulse and ultrafast excitations

    SciTech Connect

    Smijesh, N.; Chandrasekharan, K.; Joshi, Jagdish C.; Philip, Reji

    2014-07-07

    We report the experimental investigation and comparison of the temporal features of short-pulse (7 ns) and ultrafast (100 fs) laser produced plasmas generated from a solid nickel target, expanding into a nitrogen background. When the ambient pressure is varied in a large range of 10⁻⁶Torr to 10²Torr, the plume intensity is found to increase rapidly as the pressure crosses 1 Torr. Time of flight (TOF) spectroscopy of emission from neutral nickel (Ni I) at 361.9 nm (3d⁹(²D) 4p → 3d⁹(²D) 4s transition) reveals two peaks (fast and slow species) in short-pulse excitation and a single peak in ultrafast excitation. The fast and slow peaks represent recombined neutrals and un-ionized neutrals, respectively. TOF emission from singly ionized nickel (Ni II) studied using the 428.5 nm (3p⁶3d⁸(³P) 4s→ 3p⁶3d⁹ 4s) transition shows only a single peak for either excitation. Velocities of the neutral and ionic species are determined from TOF measurements carried out at different positions (i.e., at distances of 2 mm and 4 mm, respectively, from the target surface) on the plume axis. Measured velocities indicate acceleration of neutrals and ions, which is caused by the Coulomb pull of the electrons enveloping the plume front in the case of ultrafast excitation. Both Coulomb pull and laser-plasma interaction contribute to the acceleration in the case of short-pulse excitation. These investigations provide new information on the pressure dependent temporal behavior of nickel plasmas produced by short-pulse and ultrafast laser pulses, which have potential uses in applications such as pulsed laser deposition and laser-induced nanoparticle generation.

  10. Note: Longitudinally excited N{sub 2} laser with low beam divergence

    SciTech Connect

    Uno, K. Akitsu, T.; Jitsuno, T.

    2014-09-15

    We developed a longitudinally excited N{sub 2} laser (337 nm) with low beam divergence without collimator lenses. The N{sub 2} laser consisted of a 30 cm long Pyrex glass tube with an inner diameter of 2.5 mm, a normal stable resonator formed by flat mirrors, and a simple, novel driver circuit. At a N{sub 2} gas pressure of 0.4 kPa and a repetition rate of 40 Hz, the N{sub 2} laser produced a circular beam with an output energy of 2.6 μJ and a low full-angle beam divergence of 0.29 mrad due to the uniform discharge formed by the longitudinal excitation scheme, the long cavity with the small aperture, and the low-input energy oscillation.

  11. Dynamic near-field nanofocusing by V-shaped metal groove via a femtosecond laser excitation

    NASA Astrophysics Data System (ADS)

    Du, Guangqing; Yang, Qing; Chen, Feng; Lu, Yu; Ou, Yan; Yong, Jiale; Hou, Xun

    2016-03-01

    The ultrafast dynamics of plasmonic near-field nanofocusing by a V-shaped groove milled on Au film via a femtosecond laser excitation is theoretically studied based on finite element method. The spatiotemporal evolution of the focused e-fields around the V-groove geometry is obtained. It is revealed that the strong nanofocusing at the V-shaped groove occurs at the moderate electron temperature of 3000 K in the electron-phonon uncoupled state via a femtosecond laser pulse excitation. The phenomenon is explained as the electron thermal dynamics manipulation of plasmon resonances due to femtosecond laser fluence modifications. This study provides basic understanding of ultrafast dynamics of near-field nanofocusing in V-shaped geometry for wide applications in the fields such as super-resolution imaging, SERS, and photothermal therapy.

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

    SciTech Connect

    Kaptan, Y. Herzog, B.; Schöps, O.; Kolarczik, M.; Woggon, U.; Owschimikow, N.; Röhm, A.; Lingnau, B.; Lüdge, K.; Schmeckebier, H.; Arsenijević, D.; Bimberg, D.; Mikhelashvili, V.; Eisenstein, G.

    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 observed 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.

  13. Design of an infrared camera based aircraft detection system for laser guide star installations

    SciTech Connect

    Friedman, H.; Macintosh, B.

    1996-03-05

    There have been incidents in which the irradiance resulting from laser guide stars have temporarily blinded pilots or passengers of aircraft. An aircraft detection system based on passive near infrared cameras (instead of active radar) is described in this report.

  14. Large excited state two photon absorptions in the near infrared region of surprisingly stable radical cations of (ferrocenyl)indenes.

    PubMed

    Orian, Laura; Scuppa, Stefano; Santi, Saverio; Meneghetti, Moreno

    2013-08-21

    Multiphoton absorptions are important non-linear optical processes which allow us to explore excited states with low energy photons giving rise to new possibilities for photoinduced processes. Among these processes, multiphoton absorptions from excited states are particularly interesting because of the large susceptibilities characteristic of excited states. Here we explore the nonlinear transmission measurements recorded with 9 ns laser pulses at 1064 nm of the radical cations of (2-ferrocenyl)indene and of (2-ferrocenyl)-hexamethylindene, two interesting very stable molecules. The non-linear transmission data can be interpreted with a multiphoton sequence of three photon absorptions, the first being a one photon absorption related to the intramolecular charge transfer and the second a two photon absorption from the excited state created with the first process. The two photon absorption cross section is found to be several orders of magnitude larger than those usually found for two photon absorbing systems excited from the ground state.

  15. Detection of an infrared near-field optical signal by attaching an infrared-excitable phosphor to the end of a photocantilever.

    PubMed

    Tanaka, Y; Fukuzawa, K; Ohwaki, J

    1999-01-01

    To improve the signal-to-noise ratio of near-field scanning optical microscopy, we propose attaching an infrared-excitable phosphor (IEP) to a photocantilever. One source of noise is the light scattered from locations on the sample surface other than that of the probe tip. By detecting only the light scattered from the tip, we can obtain a near-field optical signal without noise. We attached an IEP particle to a photocantilever to convert infrared light to visible light and we used 1550-nm infrared illumination, so the light scattered from the sample was only infrared. The silicon photodiode of the photocantilever is 10(6) times less sensitive to infrared light than to visible light. As a result, only the converted visible light from the IEP particle, i.e. the signal containing the near-field optical information from the tip, was detected. We verified that the photocantilever detected the signal in the evanescent light produced by infrared illumination and that the detected signal was the light converted by the IEP. The experimental results show the feasibility of detecting infrared light and not the background light through the use of the IEP.

  16. Ultrafast gating of a mid-infrared laser pulse by a sub-pC relativistic electron beam

    SciTech Connect

    Cesar, D. B.; Musumeci, P.; Alesini, D.

    2015-12-21

    In this paper we discuss a relative time-of-arrival measurement scheme between an electron beam and a mid-infrared laser pulse based on the electron-beam controlled transmission in semiconductor materials. This technique can be used as a time-stamping diagnostic in ultrafast electron diffraction or microscopy. In particular, our characterization of Germanium demonstrates that sub-ps time-of-arrival sensitivity could be achieved in a single shot and with very low charge beams (<1 pC). Detailed measurements as a function of the beam charge and the laser wavelength offer insights on the free carrier dynamics in the semiconductor upon excitation by the electron beam.

  17. Portable Infrared Laser Spectroscopy for On-site Mycotoxin Analysis

    NASA Astrophysics Data System (ADS)

    Sieger, Markus; Kos, Gregor; Sulyok, Michael; Godejohann, Matthias; Krska, Rudolf; Mizaikoff, Boris

    2017-03-01

    Mycotoxins are toxic secondary metabolites of fungi that spoil food, and severely impact human health (e.g., causing cancer). Therefore, the rapid determination of mycotoxin contamination including deoxynivalenol and aflatoxin B1 in food and feed samples is of prime interest for commodity importers and processors. While chromatography-based techniques are well established in laboratory environments, only very few (i.e., mostly immunochemical) techniques exist enabling direct on-site analysis for traders and manufacturers. In this study, we present MYCOSPEC - an innovative approach for spectroscopic mycotoxin contamination analysis at EU regulatory limits for the first time utilizing mid-infrared tunable quantum cascade laser (QCL) spectroscopy. This analysis technique facilitates on-site mycotoxin analysis by combining QCL technology with GaAs/AlGaAs thin-film waveguides. Multivariate data mining strategies (i.e., principal component analysis) enabled the classification of deoxynivalenol-contaminated maize and wheat samples, and of aflatoxin B1 affected peanuts at EU regulatory limits of 1250 μg kg‑1 and 8 μg kg‑1, respectively.

  18. Portable Infrared Laser Spectroscopy for On-site Mycotoxin Analysis

    PubMed Central

    Sieger, Markus; Kos, Gregor; Sulyok, Michael; Godejohann, Matthias; Krska, Rudolf; Mizaikoff, Boris

    2017-01-01

    Mycotoxins are toxic secondary metabolites of fungi that spoil food, and severely impact human health (e.g., causing cancer). Therefore, the rapid determination of mycotoxin contamination including deoxynivalenol and aflatoxin B1 in food and feed samples is of prime interest for commodity importers and processors. While chromatography-based techniques are well established in laboratory environments, only very few (i.e., mostly immunochemical) techniques exist enabling direct on-site analysis for traders and manufacturers. In this study, we present MYCOSPEC - an innovative approach for spectroscopic mycotoxin contamination analysis at EU regulatory limits for the first time utilizing mid-infrared tunable quantum cascade laser (QCL) spectroscopy. This analysis technique facilitates on-site mycotoxin analysis by combining QCL technology with GaAs/AlGaAs thin-film waveguides. Multivariate data mining strategies (i.e., principal component analysis) enabled the classification of deoxynivalenol-contaminated maize and wheat samples, and of aflatoxin B1 affected peanuts at EU regulatory limits of 1250 μg kg−1 and 8 μg kg−1, respectively. PMID:28276454

  19. Short infrared (IR) laser pulses can induce nanoporation

    NASA Astrophysics Data System (ADS)

    Roth, Caleb C.; Barnes, Ronald A.; Ibey, Bennett L.; Glickman, Randolph D.; Beier, Hope T.

    2016-03-01

    Short infrared (IR) laser pulses on the order of hundreds of microseconds to single milliseconds with typical wavelengths of 1800-2100 nm, have shown the capability to reversibly stimulate action potentials (AP) in neuronal cells. While the IR stimulation technique has proven successful for several applications, the exact mechanism(s) underlying the AP generation has remained elusive. To better understand how IR pulses cause AP stimulation, we determined the threshold for the formation of nanopores in the plasma membrane. Using a surrogate calcium ion, thallium, which is roughly the same shape and charge, but lacks the biological functionality of calcium, we recorded the flow of thallium ions into an exposed cell in the presence of a battery of channel antagonists. The entry of thallium into the cell indicated that the ions entered via nanopores. The data presented here demonstrate a basic understanding of the fundamental effects of IR stimulation and speculates that nanopores, formed in response to the IR exposure, play an upstream role in the generation of AP.

  20. Subtarget Effect on Laser Plasma Generated by Transversely Excited Atmospheric CO2 Laser at Atmospheric Gas Pressure

    NASA Astrophysics Data System (ADS)

    Kagawa, Kiichiro; Lie, Tjung Jie; Hedwig, Rinda; Abdulmajid, Syahrun Nur; Suliyanti, Maria Margaretha; Kurniawan, Hendrik

    2000-05-01

    An experimental study has been carried out on the dynamical process taking place in the laser plasma generated by Transversely Excited Atmospheric CO2 laser (100 mJ, 50 ns) irradiation of a soft sample at surrounding helium pressure of 1 atm. It is shown that the presence of a copper subtarget behind the soft sample is crucial in raising the gushing speed of the atoms to the level adequate for the generation of shock wave laser plasma even at atmospheric pressure. It is also found that the time profiles of spatially integrated emission intensity of the target’s atoms and gas atoms exhibit a characteristic dynamical process that consists of successive excitation and cooling stages even at such a high pressure, which is typical of shock wave laser plasma. It is therefore suggested that the generation of the laser plasma at atmospheric pressure is more likely due to the shock wave mechanism than to the widely known breakdown mechanism. Initial spectrochemical analysis of water from the blow off of a boiler system was also carried out, showing a detection limit of as low as 5 ppm for calcium.

  1. Origins of intracellular calcium mobilization evoked by infrared laser stimulation

    NASA Astrophysics Data System (ADS)

    Olsovsky, Cory A.; Tolstykh, Gleb P.; Ibey, Bennett L.; Beier, Hope T.

    2015-03-01

    Cellular delivery of pulsed IR laser energy has been shown to stimulate action potentials in neurons. The mechanism for this stimulation is not completely understood. Certain hypotheses suggest the rise in temperature from IR exposure could activate temperature- or pressure-sensitive channels, or create pores in the cellular outer membrane. Studies using intensity-based Ca2+-responsive dyes show changes in Ca2+ levels after various IR stimulation parameters; however, determination of the origin of this signal proved difficult. An influx of larger, typically plasma-membrane-impermeant ions has been demonstrated, which suggests that Ca2+ may originate from the external solution. However, activation of intracellular signaling pathways, possibly indicating a more complex role of increasing Ca2+ concentration, has also been shown. By usingCa2+ sensitive dye Fura-2 and a high-speed ratiometric imaging system that rapidly alternates the excitation wavelengths, we have quantified the Ca2+ mobilization in terms of influx from the external solution and efflux from intracellular organelles. CHO-K1 cells, which lack voltage-gated Ca2+ channels, and NG-108 neuroblastoma cells, which do not produce action potentials in an early undifferentiated state, are used to determine the origin of the Ca2+ signals and investigate the role these mechanisms may play in IR neural stimulation.

  2. Development of mid-infrared solid state lasers for spaceborne lidar

    NASA Technical Reports Server (NTRS)

    Whitney, Donald A.; Kim, Kyong H.

    1988-01-01

    This semiannual progress report covers work performed during the period from April 13, 1988 to October 13, 1988 under NASA grant number NAG-1-877 entitled, Development of mid-infrared solid state lasers for spaceborne lidar. We have designed a flashlamp-pumped Cr3(+);GSAG laser of pulsed laser energy greater than 200 mJ and of pulse width of 1 ms FWHM to simulate a high-power laser diode in pumping mid-infrared laser crystals such as Tm3(+), Er3(+), and/or Ho3(+)-ion doped YAG, YLF or other host materials. This Cr3(+);GSAG laser will be used to determine optimum conditions for laser diode pumped mid-infrared lasers, maximum energy extraction limit with longitudinal pumping, thermal damage limit, and other problems related to high power laser diode pumping. We have completed a modification of an existing flashlamp-pumped and liquid nitrogen cooled rare earth laser system for 60 J electrical input energy and a 500 micron pulse width, and have carried out preliminary experiments with a Ho(+):Er3(+):Tm3(+):YAG crystal to test the system performance. This flashlamp-pumped rare earth laser system will be used to determine optimum Tm3(+)-ion concentration in Ho3(+):Cr3(+):Tm3(+):YAG crystal in the remaining research period.

  3. Development of mid-infrared solid state lasers for spaceborne lidar

    NASA Astrophysics Data System (ADS)

    Whitney, Donald A.; Kim, Kyong H.

    1988-07-01

    This semiannual progress report covers work performed during the period from April 13, 1988 to October 13, 1988 under NASA grant number NAG-1-877 entitled, Development of mid-infrared solid state lasers for spaceborne lidar. We have designed a flashlamp-pumped Cr3(+);GSAG laser of pulsed laser energy greater than 200 mJ and of pulse width of 1 ms FWHM to simulate a high-power laser diode in pumping mid-infrared laser crystals such as Tm3(+), Er3(+), and/or Ho3(+)-ion doped YAG, YLF or other host materials. This Cr3(+);GSAG laser will be used to determine optimum conditions for laser diode pumped mid-infrared lasers, maximum energy extraction limit with longitudinal pumping, thermal damage limit, and other problems related to high power laser diode pumping. We have completed a modification of an existing flashlamp-pumped and liquid nitrogen cooled rare earth laser system for 60 J electrical input energy and a 500 micron pulse width, and have carried out preliminary experiments with a Ho(+):Er3(+):Tm3(+):YAG crystal to test the system performance. This flashlamp-pumped rare earth laser system will be used to determine optimum Tm3(+)-ion concentration in Ho3(+):Cr3(+):Tm3(+):YAG crystal in the remaining research period.

  4. Ground and excited state dipole moments of coumarin 337 laser dye

    NASA Astrophysics Data System (ADS)

    Raikar, U. S.; Tangod, V. B.; Mannopantar, S. R.; Mastiholi, B. M.

    2010-11-01

    This paper reports that the effects of spectral properties of coumarin 337 laser dye have been investigated in different solvents considering solvent parameters like dielectric constant ( є) and refractive index ( n) of different solvent polarities. The ground state ( μg) and excited state ( μe) dipole moments are calculated using Lippert's, Bakhshiev's, and Kawski-Chamma-Viallet's equations. In all these three equations the variation of Stokes shift was used to calculate the excited state ( μe) dipole moment. It is observed that the Bakhshiev method is comparatively better than the other two methods for ground state and excited state dipole moment calculations. The angle between the excited state and ground state dipole moments is also calculated.

  5. Laser-excited fluorescence of rare earth elements in fluorite: Initial observations with a laser Raman microprobe

    USGS Publications Warehouse

    Burruss, R.C.; Ging, T.G.; Eppinger, R.G.; Samson, a.M.

    1992-01-01

    Fluorescence emission spectra of three samples of fluorite containing 226-867 ppm total rare earth elements (REE) were excited by visible and ultraviolet wavelength lines of an argon ion laser and recorded with a Raman microprobe spectrometer system. Narrow emission lines ( 0.9 for Eu2+ and 0.99 for Er3+. Detection limits for three micrometer spots are about 0.01 ppm Eu2+ and 0.07 ppm Er3+. These limits are less than chondrite abundance for Eu and Er, demonstrating the potential microprobe analytical applications of laser-excited fluorescence of REE in fluorite. However, application of this technique to common rock-forming minerals may be hampered by competition between fluorescence emission and radiationless energy transfer processes involving lattice phonons. ?? 1992.

  6. Vacuum ultraviolet and near-infrared excited luminescence properties of Ca 3(PO 4) 2: RE3+, Na + ( RE=Tb, Yb, Er, Tm, and Ho)

    NASA Astrophysics Data System (ADS)

    Zhang, Jia; Wang, Yuhua; Guo, Linna; Zhang, Feng; Wen, Yan; Liu, Bitao; Huang, Yan

    2011-08-01

    Tb 3+, Yb 3+, Tm 3+, Er 3+, and Ho 3+ doped Ca 3(PO 4) 2 were synthesized by solid-state reaction, and their luminescence properties were studied by spectra techniques. Tb 3+-doped samples can exhibit intense green emission under VUV excitation, and the brightness for the optimal Tb 3+ content is comparable with that of the commercial Zn 2SiO 4:Mn 2+ green phosphor. Under near-infrared laser excitation, the upconversion luminescence spectra of Yb 3+, Tm 3+, Er 3+, and Ho 3+ doped samples demonstrate that the red, green, and blue tricolored fluorescence could be obtained by codoping Yb 3+-Ho 3+, Yb 3+-Er 3+, and Yb 3+-Tm 3+ in Ca 3(PO 4) 2, respectively. Good white upconversion emission with CIE chromaticity coordinates (0.358, 0.362) is achieved by quadri-doping Yb 3+-Tm 3+-Er 3+-Ho 3+ in Ca 3(PO 4) 2, in which the cross-relaxation process between Er 3+ and Tm 3+, producing the 1D2- 3F4 transition of Tm 3+, is found. The upconversion mechanisms are elucidated through the laser power dependence of the upconverted emissions and the energy level diagrams.

  7. Assessment of different excitation wavelengths for photodetecting neoplastic urothelial lesions by laser-induced autofluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Anidjar, Maurice; Cussenot, Oliver; Avrillier, Sigrid; Ettori, Dominique; Teillac, Pierre; Le Duc, Alain

    1996-04-01

    We have designed a program using laser induced autofluorescence spectroscopy as a possible way to characterize urothelial tumors of the bladder. The autofluorescence spectra were compared between normal, suspicious and tumor areas of human bladder. Three different pulsed laser wavelengths were used for excitation: 308 nm (excimer), 337 nm (nitrogen) and 480 nm (dye laser). Excitation light was delivered by a specially devised multifiber catheter introduced through the working channel of a regular cystoscope under saline irrigation. The fluorescence light was focused into an optical multichannel analyzer detection system. The data was evaluated in 25 patients immediately before resection of a bladder tumor. Spectroscopic results were compared with histopathology. Upon 337 nm and 480 nm excitations, the overall intensity of the fluorescence spectra from bladder tumors was clearly reduced in comparison with normal urothelium, regardless of the stage and the grade of the tumor. upon 308 nm excitation, the shape of tumor fluorescence spectra, including carcinoma in situ, differed drastically from that of normal tissue. In this case, no absolute intensity measurements are needed and clear diagnosis can be achieved from fluorescence intensity ratio (360/440 nm). This spectroscopic study could be particularly useful for the design of a simplified autofluorescence imaging device for real-time routine detection of occult urothelial neoplastic lesions.

  8. Direct and secondary nuclear excitation with x-ray free-electron lasers

    SciTech Connect

    Gunst, Jonas; Wu, Yuanbin Kumar, Naveen; Keitel, Christoph H.; Pálffy, Adriana

    2015-11-15

    The direct and secondary nuclear excitation produced by an x-ray free electron laser when interacting with a solid-state nuclear target is investigated theoretically. When driven at the resonance energy, the x-ray free electron laser can produce direct photoexcitation. However, the dominant process in that interaction is the photoelectric effect producing a cold and very dense plasma in which also secondary processes such as nuclear excitation by electron capture may occur. We develop a realistic theoretical model to quantify the temporal dynamics of the plasma and the magnitude of the secondary excitation therein. Numerical results show that depending on the nuclear transition energy and the temperature and charge states reached in the plasma, secondary nuclear excitation by electron capture may dominate the direct photoexcitation by several orders of magnitude, as it is the case for the 4.8 keV transition from the isomeric state of {sup 93}Mo, or it can be negligible, as it is the case for the 14.4 keV Mössbauer transition in {sup 57}Fe. These findings are most relevant for future nuclear quantum optics experiments at x-ray free electron laser facilities.

  9. Low-intensity red and infrared laser effects at high fluences on Escherichia coli cultures.

    PubMed

    Barboza, L L; Campos, V M A; Magalhães, L A G; Paoli, F; Fonseca, A S

    2015-10-01

    Semiconductor laser devices are readily available and practical radiation sources providing wavelength tenability and high monochromaticity. Low-intensity red and near-infrared lasers are considered safe for use in clinical applications. However, adverse effects can occur via free radical generation, and the biological effects of these lasers from unusually high fluences or high doses have not yet been evaluated. Here, we evaluated the survival, filamentation induction and morphology of Escherichia coli cells deficient in repair of oxidative DNA lesions when exposed to low-intensity red and infrared lasers at unusually high fluences. Cultures of wild-type (AB1157), endonuclease III-deficient (JW1625-1), and endonuclease IV-deficient (JW2146-1) E. coli, in exponential and stationary growth phases, were exposed to red and infrared lasers (0, 250, 500, and 1000 J/cm2) to evaluate their survival rates, filamentation phenotype induction and cell morphologies. The results showed that low-intensity red and infrared lasers at high fluences are lethal, induce a filamentation phenotype, and alter the morphology of the E. coli cells. Low-intensity red and infrared lasers have potential to induce adverse effects on cells, whether used at unusually high fluences, or at high doses. Hence, there is a need to reinforce the importance of accurate dosimetry in therapeutic protocols.

  10. Low-level infrared laser modulates muscle repair and chromosome stabilization genes in myoblasts.

    PubMed

    da Silva Neto Trajano, Larissa Alexsandra; Stumbo, Ana Carolina; da Silva, Camila Luna; Mencalha, Andre Luiz; Fonseca, Adenilson S

    2016-08-01

    Infrared laser therapy is used for skeletal muscle repair based on its biostimulative effect on satellite cells. However, shortening of telomere length limits regenerative potential in satellite cells, which occurs after each cell division cycle. Also, laser therapy could be more effective on non-physiologic tissues. This study evaluated low-level infrared laser exposure effects on mRNA expression from muscle injury repair and telomere stabilization genes in myoblasts in normal and stressful conditions. Laser fluences were those used in clinical protocols. C2C12 myoblast cultures were exposed to low-level infrared laser (10, 35, and 70 J/cm(2)) in standard or normal (10 %) and reduced (2 %) fetal bovine serum concentrations; total RNA was extracted for mRNA expression evaluation from muscle injury repair (MyoD and Pax7) and chromosome stabilization (TRF1 and TRF2) genes by real time quantitative polymerization chain reaction. Data show that low-level infrared laser increases the expression of MyoD and Pax7 in 10 J/cm(2) fluence, TRF1 expression in all fluences, and TRF2 expression in 70 J/cm(2) fluence in both 10 and 2 % fetal bovine serum. Low-level infrared laser increases mRNA expression from genes related to muscle repair and telomere stabilization in myoblasts in standard or normal and stressful conditions.

  11. Low-intensity red and infrared laser effects at high fluences on Escherichia coli cultures

    PubMed Central

    Barboza, L.L.; Campos, V.M.A.; Magalhães, L.A.G.; Paoli, F.; Fonseca, A.S.

    2015-01-01

    Semiconductor laser devices are readily available and practical radiation sources providing wavelength tenability and high monochromaticity. Low-intensity red and near-infrared lasers are considered safe for use in clinical applications. However, adverse effects can occur via free radical generation, and the biological effects of these lasers from unusually high fluences or high doses have not yet been evaluated. Here, we evaluated the survival, filamentation induction and morphology of Escherichia coli cells deficient in repair of oxidative DNA lesions when exposed to low-intensity red and infrared lasers at unusually high fluences. Cultures of wild-type (AB1157), endonuclease III-deficient (JW1625-1), and endonuclease IV-deficient (JW2146-1) E. coli, in exponential and stationary growth phases, were exposed to red and infrared lasers (0, 250, 500, and 1000 J/cm2) to evaluate their survival rates, filamentation phenotype induction and cell morphologies. The results showed that low-intensity red and infrared lasers at high fluences are lethal, induce a filamentation phenotype, and alter the morphology of the E. coli cells. Low-intensity red and infrared lasers have potential to induce adverse effects on cells, whether used at unusually high fluences, or at high doses. Hence, there is a need to reinforce the importance of accurate dosimetry in therapeutic protocols. PMID:26445339

  12. Highly emitting near-infrared lanthanide "encapsulated sandwich" metallacrown complexes with excitation shifted toward lower energy.

    PubMed

    Trivedi, Evan R; Eliseeva, Svetlana V; Jankolovits, Joseph; Olmstead, Marilyn M; Petoud, Stéphane; Pecoraro, Vincent L

    2014-01-29

    Near-infrared (NIR) luminescent lanthanide complexes hold great promise for practical applications, as their optical properties have several complementary advantages over organic fluorophores and semiconductor nanoparticles. The fundamental challenge for lanthanide luminescence is their sensitization through suitable chromophores. The use of the metallacrown (MC) motif is an innovative strategy to arrange several organic sensitizers at a well-controlled distance from a lanthanide cation. Herein we report a series of lanthanide “encapsulated sandwich” MC complexes of the form Ln3+ [12-MC(Zn(II),quinHA)-4]2[24-MC(Zn(II),quinHA)-8] (Ln3+ [Zn(II)MC(quinHA)]) in which the MC framework is formed by the self-assembly of Zn2+ ions and tetradentate chromophoric ligands based on quinaldichydroxamic acid (quinHA). A first-generation of luminescent MCs was presented previously but was limited due to excitation wavelengths in the UV. We report here that through the design of the chromophore of the MC assembly, we have significantly shifted the absorption wavelength toward lower energy (450 nm). In addition to this near-visible inter- and/or intraligand charge transfer absorption, Ln3+ [Zn(II)MC(quinHA)] exhibits remarkably high quantum yields, long luminescence lifetimes (CD3OD; Yb3+, QLn(L) = 2.88(2)%, τobs = 150.7(2) μs; Nd3+, QLn(L) = 1.35(1)%, τobs = 4.11(3) μs; Er3+, QLn(L) = 3.60(6)·10–2%, τobs = 11.40(3) μs), and excellent photostability. Quantum yields of Nd3+ and Er3+ MCs in the solid state and in deuterated solvents, upon excitation at low energy, are the highest values among NIR-emitting lanthanide complexes containing C–H bonds. The versatility of the MC strategy allows modifications in the excitation wavelength and absorptivity through the appropriate design of the ligand sensitizer, providing a highly efficient platform with tunable properties.

  13. INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: Coherent phase control of excitation of atoms by bichromatic laser radiation in an electric field

    NASA Astrophysics Data System (ADS)

    Astapenko, Valerii A.

    2005-06-01

    A new method for coherent phase control of excitation of atoms in a discrete spectrum under the action of bichromatic laser radiation with the frequency ratio 1:2 is analysed. An important feature of this control method is the presence of a electrostatic field, which removes the parity selection rule for one of the control channels. It is shown that for the phase difference between the monochromatic radiation components, corresponding to the destructive interference between channels, there exists the electrostatic field strength at which the excited atomic transition is 'bleached'. It is proposed to use luminescence at the adjacent atomic transition for detecting the phase dependence of optical excitation.

  14. Inertial cavitation in theranostic nanoemulsions with simultaneous pulsed laser and low frequency ultrasound excitation

    NASA Astrophysics Data System (ADS)

    Arnal, Bastien; Wei, Chen-Wei; Xia, Jinjun; Pelivanov, Ivan M.; Lombardo, Michael; Perez, Camilo; Matula, Thomas J.; Pozzo, Danilo; O'Donnell, Matthew

    2014-03-01

    Ultrasound-induced inertial cavitation is a mechanical process used for site-localized therapies such as non-invasive surgery. Initiating cavitation in tissue requires very high intensity focused ultrasound (HIFU) and low-frequencies. Hence, some applications like thrombolysis require targeted contrast agents to reduce peak intensities and the potential for secondary effects. A new type of theranostic nanoemulsion has been developed as a combined ultrasound (US)/photoacoustic(PA) agent for molecular imaging and therapy. It includes a nanoscale emulsion core encapsulated with a layer of gold nanospheres at the water/ oil interface. Its optical absorption exhibits a spectrum broadened up to 1100 nm, opening the possibility that 1064 nm light can excite cavitation nuclei. If optically-excited nuclei are produced at the same time that a low-frequency US wave is at peak negative pressure, then highly localized therapies based on acoustic cavitation may be enabled at very low US pressures. We have demonstrated this concept using a low-cost, low energy, portable 1064 nm fiber laser in conjunction with a 1.24 MHz US transducer for simultaneous laser/US excitation of nanoemulsions. Active cavitation detection from backscattered signals indicated that cavitation can be initiated at very low acoustic pressures (less than 1 MPa) when laser excitation coincides with the rarefaction phase of the acoustic wave, and that no cavitation is produced when light is delivered during the compressive phase. US can sustain cavitation activity during long acoustic bursts and stimulate diffusion of the emulsion, thus increasing treatment speed. An in vitro clot model has been used to demonstrate combined US and laser excitation of the nanoemulsion for efficient thrombolysis.

  15. Sequential nonadiabatic excitation of large molecules and ions driven by strong laser fields

    SciTech Connect

    Markevitch, Alexei N.; Levis, Robert J.; Romanov, Dmitri A.; Smith, Stanley M.; Schlegel, H. Bernhard; Ivanov, Misha Yu.

    2004-01-01

    Electronic processes leading to dissociative ionization of polyatomic molecules in strong laser fields are investigated experimentally, theoretically, and numerically. Using time-of-flight ion mass spectroscopy, we study the dependence of fragmentation on laser intensity for a series of related molecules and report regular trends in this dependence on the size, symmetry, and electronic structure of a molecule. Based on these data, we develop a model of dissociative ionization of polyatomic molecules in intense laser fields. The model is built on three elements: (i) nonadiabatic population transfer from the ground electronic state to the excited-state manifold via a doorway (charge-transfer) transition; (ii) exponential enhancement of this transition by collective dynamic polarization of all electrons, and (iii) sequential energy deposition in both neutral molecules and resulting molecular ions. The sequential nonadiabatic excitation is accelerated by a counterintuitive increase of a large molecule's polarizability following its ionization. The generic theory of sequential nonadiabatic excitation forms a basis for quantitative description of various nonlinear processes in polyatomic molecules and ions in strong laser fields.

  16. Excitation and dissociation mechanisms in molecules with application to mercuric halide laser system

    SciTech Connect

    Spence, D.; Wang, R.G.; Dillon, M.A.

    1982-01-01

    Although the mercuric halide laser systems have received intensive study in recent years, being one of only two efficient electronic-transition lasers known, the precise collisional mechanisms leding to HgBr(B), formation and subsequent fluorescence are still imperfectly understood. The initial suggestion that direct collisional excitation of, say, HgBr/sub 2/, by electrons (analogous to photoionization), i.e., HgBr/sub 2/ + e ..-->.. HgBr(b) + Br + e, was the dominant mechanism, was temporarily abandoned when a measurement by Allison and Zare yielded a cross section of only < 1 x 10/sup -20/ cm/sup 2/ for low incident electron energy HgBr(B-x) fluorescence, much too small to explain the observed laser efficiency. Subsequent explanations for HgBr(B) formation included energy transfer from excited N/sub 2/ or rare gases, electronic recombination of HgBr/sub 2//sup +/, or dissociative electron attachment. Though it has recently been demonstrated that electronic energy transfer does play a role in HgBr(B) formation in the presence of N/sub 2/ or X/sub e/ buffers, modeling studies of e-beam sustained discharges have now conclusively shown that direct electron-impact excitation of mercuric halides, is indeed the dominant laser mechanism. The technique of electron-energy-loss spectroscopy was used to obtain pseudo-optical absorption spectra in HgBr/sub 2/ and HgCl/sub 2/. Results are presented and discussed. (WHK)

  17. High quality electron beam acceleration by ionization injection in laser wakefields with mid-infrared dual-color lasers

    NASA Astrophysics Data System (ADS)

    Zeng, Ming; Luo, Ji; Chen, Min; Mori, Warren B.; Sheng, Zheng-Ming; Hidding, Bernhard

    2016-06-01

    For the laser wakefield acceleration, suppression of beam energy spread while keeping sufficient charge is one of the key challenges. In order to achieve this, we propose bichromatic laser ionization injection with combined laser wavelengths of 2.4 μ m and 0.8 μ m for wakefield excitation and triggering electron injection via field ionization, respectively. A laser pulse at 2.4 μ m wavelength enables one to drive an intense acceleration structure with a relatively low laser power. To further reduce the requirement of laser power, we also propose to use carbon dioxide as the working gas medium, where carbon acts as the injection element. Our three dimensional particle-in-cell simulations show that electron beams at the GeV energy level with both low energy spreads (around 1%) and high charges (several tens of picocoulomb) can be obtained by the use of this scheme with laser peak power totaling sub-100 TW.

  18. Mid-infrared laser emission from Cr:ZnS channel waveguide fabricated by femtosecond laser helical writing

    PubMed Central

    Peng, Ya-Pei; Zou, Xiao; Bai, Zhengyuan; Leng, Yuxin; Jiang, Benxue; Jiang, Xiongwei; Zhang, Long

    2015-01-01

    The operation of a mid-infrared laser at 2244 nm in a Cr:ZnS polycrystalline channel waveguide fabricated using direct femtosecond laser writing with a helical movement technique is demonstrated. A maximum power output of 78 mW and an optical-to-optical slope efficiency of 8.6% are achieved. The compact waveguide structure with 2 mm length was obtained through direct femtosecond laser writing, which was moved on a helical trajectory along the laser medium axis and parallel to the writing direction. PMID:26692268

  19. Ab Initio Simulation of Electrical Currents Induced by Ultrafast Laser Excitation of Dielectric Materials

    NASA Astrophysics Data System (ADS)

    Wachter, Georg; Lemell, Christoph; Burgdörfer, Joachim; Sato, Shunsuke A.; Tong, Xiao-Min; Yabana, Kazuhiro

    2014-08-01

    We theoretically investigate the generation of ultrafast currents in insulators induced by strong few-cycle laser pulses. Ab initio simulations based on time-dependent density functional theory give insight into the atomic-scale properties of the induced current signifying a femtosecond-scale insulator-metal transition. We observe the transition from nonlinear polarization currents during the laser pulse at low intensities to tunnelinglike excitation into the conduction band at higher laser intensities. At high intensities, the current persists after the conclusion of the laser pulse considered to be the precursor of the dielectric breakdown on the femtosecond scale. We show that the transferred charge sensitively depends on the orientation of the polarization axis relative to the crystal axis, suggesting that the induced charge separation reflects the anisotropic electronic structure. We find good agreement with very recent experimental data on the intensity and carrier-envelope phase dependence [A. Schiffrin et al., Nature (London) 493, 70 (2013)].

  20. Transcranial low-level infrared laser irradiation ameliorates depression induced by reserpine in rats.

    PubMed

    Mohammed, Haitham S

    2016-11-01

    Transcranial low-level infrared laser is a modality of therapy based on the principle of photons delivered in a non-invasive manner through the skull for the treatment of some neurological conditions such as psychological disorders, traumatic brain injuries, and neurodegenerative diseases among others. In the present study, effects of low-level infrared laser irradiation with different radiation powers (80, 200, and 400 mW, continuous wave) were investigated on normal animals subjected to forced swimming test (FST). Results indicated that there are changes in FST parameters in animals irradiated with laser; the lowest dose provoked a significant increase in animal activity (swimming and climbing) and a significant decrease in animal's immobility, while the highest laser dose resulted in a complete inverse action by significantly increasing animal immobility and significantly decreasing animal activity with respect to control animals. The lowest dose (80 mW) of transcranial laser irradiation has then utilized on animals injected with a chronic dose of reserpine (0.2 mg/kg i.p. for 14 days) served as an animal model of depression. Laser irradiation has successfully ameliorated depression induced by reserpine as indicated by FST parameters and electrocorticography (ECoG) spectral analysis in irradiated animals. The findings of the present study emphasized the beneficial effects of low-level infrared laser irradiation on normal and healthy animals. Additionally, it indicated the potential antidepressant activity of the low dose of infrared laser irradiation.

  1. Comparison of laser-based mitigation of fused silica surface damage using mid- versus far-infrared lasers

    SciTech Connect

    Yang, S T; Matthews, M J; Elhadj, S; Cooke, D; Guss, G M; Draggoo, V G; Wegner, P J

    2009-12-16

    Laser induced growth of optical damage can limit component lifetime and therefore operating costs of large-aperture fusion-class laser systems. While far-infrared (IR) lasers have been used previously to treat laser damage on fused silica optics and render it benign, little is known about the effectiveness of less-absorbing mid-IR lasers for this purpose. In this study, they quantitatively compare the effectiveness and efficiency of mid-IR (4.6 {micro}m) versus far-IR (10.6 {micro}m) lasers in mitigating damage growth on fused silica surfaces. The non-linear volumetric heating due to mid-IR laser absorption is analyzed by solving the heat equation numerically, taking into account the temperature-dependent absorption coefficient {alpha}(T) at {lambda} = 4.6 {micro}m, while far-IR laser heating is well-described by a linear analytic approximation to the laser-driven temperature rise. In both cases, the predicted results agree well with surface temperature measurements based on infrared radiometry, as well as sub-surface fictive temperature measurements based on confocal Raman microscopy. Damage mitigation efficiency is assessed using a figure of merit (FOM) relating the crack healing depth to laser power required, under minimally-ablative conditions. Based on their FOM, they show that for cracks up to at least 500 {micro}m in depth, mitigation with a 4.6 {micro}m mid-IR laser is more efficient than mitigation with a 10.6 {micro}m far-IR laser. This conclusion is corroborated by direct application of each laser system to the mitigation of pulsed laser-induced damage possessing fractures up to 225 {micro}m in depth.

  2. Statistical analysis of excitation-emission matrices for laser-induced fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Maslov, N. A.; Papaeva, E. O.

    2016-07-01

    An algorithm for statistical processing of the set of multicomponent excitation-emission matrices for laser-induced fluorescence spectroscopy is proposed that is based on principal component analysis. It is shown for the first time that the fluorescence emission and excitation spectra of unknown fluorophores in optically thin samples can be calculated. Using the proposed algorithm, it is possible to pass from principal components with alternating signs to positive quantities corresponding to the spectra of real substances. The method is applied to a mixture of three fluorescent dyes, and it is demonstrated that the obtained spectra of principal components well reproduce the spectra of initial dyes.

  3. Photoblepharokeratoconjunctivitis caused by invisible infrared radiation emitted from a green laser pointer.

    PubMed

    Khedr, Yahya A H; Khedr, Abdulla H

    2014-03-11

    There are a wide variety of laser pointers sold to the general public. Among those are the high-powered diode-pumped solid-state lasers (>5 mW), which do not follow the laser safety regulations for packing, and are sold as regular lasers without the infrared (IR) filters. In this case report, we encountered a patient with photoblepharokeratoconjunctivitis caused by the invisible IR radiations emitted from a green laser pointer. Owing to the thermal effect of the invisible IR rays led to the disease.

  4. Bioaerosol detection and classification using dual excitation wavelength laser-induced fluorescence

    NASA Astrophysics Data System (ADS)

    Jonsson, Per; Wästerby, Pär.; Gradmark, Per-Åke; Hedborg, Julia; Larsson, Anders; Landström, Lars

    2015-05-01

    We present results obtained by a detection system designed to measure laser-induced fluorescence from individual aerosol particles using dual excitation wavelengths. The aerosol is sampled from ambient air and via a 1 mm diameter nozzle, surrounded by a sheath air flow, confined into a particle beam. A continuous wave blue laser at 404 nm is focused on the aerosol beam and two photomultiplier tubes monitor the presence of individual particles by simultaneous measuring the scattered light and any induced fluorescence. When a particle is present in the detection volume, a laser pulse is triggered from an ultraviolet laser at 263 nm and the corresponding fluorescence spectrum is acquired with a spectrometer based on a diffraction grating and a 32 channel photomultiplier tube array with single-photon sensitivity. The spectrometer measures the fluorescence spectra in the wavelength region from 250 to 800 nm. In the present report, data were measured on different monodisperse reference aerosols, simulants of biological warfare agents, and different interference aerosol particles, e.g. pollen. In the analysis of the experimental data, i.e., the time-resolved scattered and fluorescence signals from 404 nm c.w. light excitation and the fluorescence spectra obtained by a pulsed 263 nm laser source, we use multivariate data analysis methods to classify each individual aerosol particle.

  5. Preablation electron and lattice dynamics on the silicon surface excited by a femtosecond laser pulse

    SciTech Connect

    Ionin, A. A.; Kudryashov, S. I. Seleznev, L. V.; Sinitsyn, D. V.; Lednev, V. N.; Pershin, S. M.

    2015-11-15

    The study of the time-resolved optical reflection from the silicon surface excited by single femtosecond laser pulses below and near the melting threshold reveals fast (less than 10 ps) Auger recombination of a photogenerated electron–hole plasma with simultaneous energy transfer to the lattice. The acoustic relaxation of the excited surface layer indicates (according to reported data) a characteristic depth of 150 nm of the introduction of the laser radiation energy, which is related to direct linear laser radiation absorption in the photoexcited material due to a decrease in the energy bandgap. The surface temperature, which is probed at a time delay of about 100 ps from the reflection thermomodulation of probe radiation and the integrated continuous thermal emission from the surface, increases with the laser fluence and, thus, favors a nonlinear increase in the fluorescence of sublimated silicon atoms. The surface temperature estimated near the picosecond melting threshold demonstrates a substantial (20%) overheating of the material with respect to the equilibrium melting temperature. Above the melting threshold, the delay of formation of the material melt decreases rapidly (from several tens of picoseconds to several fractions of a picosecond) when the laser fluence and, correspondingly, the surface temperature increase. In the times of acoustic relaxation of the absorbing layer and even later, the time modulation of the optical reflectivity of the material demonstrates acoustic reverberations with an increasing period, which are related to the formation of melt nuclei in the material.

  6. Methanogenic activity tests by Infrared Tunable Diode Laser Absorption Spectroscopy.

    PubMed

    Martinez-Cruz, Karla; Sepulveda-Jauregui, Armando; Escobar-Orozco, Nayeli; Thalasso, Frederic

    2012-10-01

    Methanogenic activity (MA) tests are commonly carried out to estimate the capability of anaerobic biomass to treat effluents, to evaluate anaerobic activity in bioreactors or natural ecosystems, or to quantify inhibitory effects on methanogenic activity. These activity tests are usually based on the measurement of the volume of biogas produced by volumetric, pressure increase or gas chromatography (GC) methods. In this study, we present an alternative method for non-invasive measurement of methane produced during activity tests in closed vials, based on Infrared Tunable Diode Laser Absorption Spectroscopy (MA-TDLAS). This new method was tested during model acetoclastic and hydrogenotrophic methanogenic activity tests and was compared to a more traditional method based on gas chromatography. From the results obtained, the CH(4) detection limit of the method was estimated to 60 ppm and the minimum measurable methane production rate was estimated to 1.09(.)10(-3) mg l(-1) h(-1), which is below CH(4) production rate usually reported in both anaerobic reactors and natural ecosystems. Additionally to sensitivity, the method has several potential interests compared to more traditional methods among which short measurements time allowing the measurement of a large number of MA test vials, non-invasive measurements avoiding leakage or external interferences and similar cost to GC based methods. It is concluded that MA-TDLAS is a promising method that could be of interest not only in the field of anaerobic digestion but also, in the field of environmental ecology where CH(4) production rates are usually very low.

  7. Interaction between pulsed infrared laser and carbon fiber reinforced polymer composite laminates

    NASA Astrophysics Data System (ADS)

    Liu, Yan-Chi; Wu, Chen-Wu; Song, Hong-Wei; Huang, Chen-Guang

    2016-10-01

    The Laser drilling processes, in particular the interaction between the pulsed infrared Laser and the target materials were investigated on the CFRP composite laminate. The incremental freezing method was designed to reveal experimentally the temporal patterns of the ablation profiles in the CFRP composite laminates subjected to pulsed Laser irradiation. The temperature characteristics of the specimens were analyzed with Finite Element Method (FEM) and the phase change history studied. The theoretical results match well with the experimental outcome.

  8. Alternatives to excimer laser refractive surgery: UV and mid-infrared laser ablation of intraocular lenses and porcine cornea

    NASA Astrophysics Data System (ADS)

    Serafetinides, A. A.; Makropoulou, M.; Spyratou, E.; Bacharis, C.

    2007-03-01

    Despite the fact that the laser applications in human ophthalmology are well established, further research is still required, for better and predictable ablation dosimetry on both cornea tissue and intraocular lenses. Further studies for alternative laser sources to the well established excimer lasers, such as UV or mid-infrared solid state lasers, have been proposed for refractive surgery. The precise lens ablation requires the use of laser wavelengths possessing a small optical penetration depth in the cornea and in the synthetic lenses, in order to confine the laser energy deposition to a small volume. In order to eliminate some very well known problems concerning the reshaping of cornea and the modification of the optical properties of the intraocular lenses, ablation experiments of ex vivo porcine cornea, acrylic PMMA and hydrophilic lenses were conducted with an Er:YAG laser (2.94 μm) and the fifth harmonic of a Nd:YAG laser (213 nm). The morphology of cornea was recorded using a cornea topography system before and immediately after the ablation. Histology analysis of the specimens was obtained, in order to examine the microscopic appearance of the ablated craters and the existence of any thermal damage caused by the mid-infrared and UV laser irradiation. The macroscopic morphology of the intraocular lens craters was inspected with an optical transmission microscope. Measurements of the ablation rates of the lenses were performed and simulated by a mathematical model.

  9. Electron density measurements in a photoinitiated, impulse-enhanced, electrically excited laser gas discharge

    NASA Astrophysics Data System (ADS)

    Seguin, V. A.; Seguin, H. J. J.; Capjack, C. E.; Nikumb, S. K.

    1986-11-01

    Measurements of the electron density within a photo-initiated, impulse-enhanced, electrically excited (PIE) laser gas discharge are presented. Ion current measurements were made using a single Langmuir electrostatic probe positioned within the laser discharge volume. Calculations of the electron density were made utilizing a thick-sheath analysis. The results indicate that the electron density increases by two orders of magnitude as the pulser power level is increased. In addition, the electron density was observed to decrease markedly as the dc discharge current was increased.

  10. Plasma membrane nanoporation as a possible mechanism behind infrared excitation of cells

    NASA Astrophysics Data System (ADS)

    Beier, Hope T.; Tolstykh, Gleb P.; Musick, Joshua D.; Thomas, Robert J.; Ibey, Bennett L.

    2014-12-01

    Objective. Short infrared (IR) laser pulses have been used to stimulate action potentials in neurons both in vivo and in vitro. However, the mechanism(s) underlying this phenomenon has remained elusive. In vitro studies have found that pulsed IR exposure generates a nearly instant change in capacitance in the plasma membrane, characterized by inward rectification, a common feature in pore-forming exposures, such as electrical pulses and acoustic shock waves. Based on this similarity, we hypothesize that the mechanism of IR stimulation is the formation of short-lived nanopores in the plasma membrane. These transient, small-diameter pores allow the influx of extracellular ions that lead to action potential generation, possibly through activation of secondary messenger pathways or depolarization of the cell membrane resulting in activation of voltage-gated ion channels. Approach. A variety of fluorescent markers are used to observe the cell response to IR stimulation to monitor for effects indicative of nanoporation in other modalities. Main results. We observe rapid, transient rises in intracellular Ca2+, influx of YO-PRO-1 and propidium iodide into the cell signifying membrane permeabilization, cellular blebbing and swelling, and activation of the intracellular phosphoinositides lipid signaling pathway. Significance. This conclusion better explains the experimental observations and limitations of IR-induced neurological stimulation and represents a distinct theoretical shift in the understanding of the mechanism of IR-induced stimulation.

  11. Rotationally resolved IR-diode laser studies of ground-state CO2 excited by collisions with vibrationally excited pyridine.

    PubMed

    Johnson, Jeremy A; Kim, Kilyoung; Mayhew, Maurine; Mitchell, Deborah G; Sevy, Eric T

    2008-03-27

    Relaxation of highly vibrationally excited pyridine (C5NH5) by collisions with carbon dioxide has been investigated using diode laser transient absorption spectroscopy. Vibrationally hot pyridine (E' = 40,660 cm(-1)) was prepared by 248 nm excimer laser excitation followed by rapid radiationless relaxation to the ground electronic state. Pyridine then collides with CO2, populating the high rotational CO2 states with large amounts of translational energy. The CO2 nascent rotational population distribution of the high-J (J = 58-80) tail of the 00(0)0 state was probed at short times following the excimer laser pulse to measure rate constants and probabilities for collisions populating these CO2 rotational states. Doppler spectroscopy was used to measure the CO2 recoil velocity distribution for J = 58-80 of the 00(0)0 state. The energy-transfer distribution function, P(E,E'), from E' - E approximately 1300-7000 cm(-1) was obtained by re-sorting the state-indexed energy-transfer probabilities as a function of DeltaE. P(E,E') is fit to an exponential or biexponential function to determine the average energy transferred in a single collision between pyridine and CO2. Also obtained are fit parameters that can be compared to previously studied systems (pyrazine, C6F6, methylpyrazine, and pyrimidine/CO2). Although the rotational and translational temperatures that describe pyridine/CO2 energy transfer are similar to previous systems, the energy-transfer probabilities are much smaller. P(E,E') fit parameters for pyridine/CO2 and the four previously studied systems are compared to various donor molecular properties. Finally, P(E,E') is analyzed in the context of two models, one indicating that P(E,E') shape is primarily determined by the low-frequency out-of-plane donor vibrational modes, and the other that indicates that P(E,E') shape can be determined from how the donor molecule final density of states changes with DeltaE.

  12. Efficiency of GaInAs/GaAs quantum-well lasers upon inhomogeneous excitation of quantum wells

    SciTech Connect

    Ushakov, D V; Afonenko, A A; Aleshkin, V Ya

    2013-11-30

    A model for calculating the power characteristics of laser structures taking into account inhomogeneous excitation of quantum wells (QWs), recombination in the barrier regions, and nonlinear gain effects is developed. It is shown that, with increasing number of QWs, the output power of the Ga{sub 0.8}In{sub 0.2}As/GaAs/InGaP structures at first considerably increases and then slightly decreases. In a wide range of injection currents, the optimal number of QWs is 5 ± 1. The inhomogeneity of QW excitation increases with increasing injection current and decreases the laser power compared to homogeneous excitation. (lasers)

  13. Relativistic ponderomotive effect on the propagation of rippled laser beam and the excitation of electron plasma wave in collisionless plasma

    NASA Astrophysics Data System (ADS)

    Priyanka; Chauhan, Prashant; Purohit, Gunjan

    2013-01-01

    This paper presents an investigation of the propagation of rippled laser beam in a collisionless plasma and its effect on and the excitation of electron plasma wave and particle acceleration, when relativistic and ponderomotive nonlinearities are simultaneously operative. Electron plasma wave (EPW) coupling with rippled laser beam arises on account of the relativistic change in the electron mass and the modification of the background electron density due to ponderomotive nonlinearity. When the electron plasma wave gets coupled to the rippled laser beam, a large fraction of the pump energy gets transferred to EPW and this excited EPW can accelerate the electrons. Analytical expressions for the growth rate of the laser spike in plasma, beam width of the rippled laser beam and excited electron plasma wave have been obtained using paraxial ray approximation. These coupled equations are solved analytically and numerically to study the growth of laser spike in plasma and its effect on the self focusing of rippled laser beam in plasma, amplitude of the excited electron plasma wave and particle acceleration. The result shows that the effect of including ponderomotive nonlinearity significantly affects the growth of laser spike in plasma, excitation of electron plasma wave as well as the number of energetic electrons in particle acceleration process. The results are presented for typical laser plasma parameters.

  14. Laser capture microdissection: Arcturus(XT) infrared capture and UV cutting methods.

    PubMed

    Gallagher, Rosa I; Blakely, Steven R; Liotta, Lance A; Espina, Virginia

    2012-01-01

    Laser capture microdissection (LCM) is a technique that allows the precise procurement of enriched cell populations from a heterogeneous tissue under direct microscopic visualization. LCM can be used to harvest the cells of interest directly or can be used to isolate specific cells by ablating the unwanted cells, resulting in histologically enriched cell populations. The fundamental components of laser microdissection technology are (a) visualization of the cells of interest via microscopy, (b) transfer of laser energy to a thermolabile polymer with either the formation of a polymer-cell composite (capture method) or transfer of laser energy via an ultraviolet laser to photovolatize a region of tissue (cutting method), and (c) removal of cells of interest from the heterogeneous tissue section. Laser energy supplied by LCM instruments can be infrared (810 nm) or ultraviolet (355 nm). Infrared lasers melt thermolabile polymers for cell capture, whereas ultraviolet lasers ablate cells for either removal of unwanted cells or excision of a defined area of cells. LCM technology is applicable to an array of applications including mass spectrometry, DNA genotyping and loss-of-heterozygosity analysis, RNA transcript profiling, cDNA library generation, proteomics discovery, and signal kinase pathway profiling. This chapter describes the unique features of the Arcturus(XT) laser capture microdissection instrument, which incorporates both infrared capture and ultraviolet cutting technology in one instrument, using a proteomic downstream assay as a model.

  15. Ultrafast spin-transfer torque driven by femtosecond pulsed-laser excitation.

    PubMed

    Schellekens, A J; Kuiper, K C; de Wit, R R J C; Koopmans, B

    2014-07-10

    Spin currents have an important role in many proposed spintronic devices, as they govern the switching process of magnetic bits in random access memories or drive domain wall motion in magnetic shift registers. The generation of these spin currents has to be fast and energy efficient for realization of these envisioned devices. Recently it has been shown that femtosecond pulsed-laser excitation of thin magnetic films creates intense and ultrafast spin currents. Here we utilize this method to change the orientation of the magnetization in a magnetic bilayer by spin-transfer torque on sub-picosecond timescales. By analysing the dynamics of the magnetic bilayer after laser excitation, the rich physics governing ultrafast spin-transfer torque are elucidated opening up new pathways to ultrafast magnetization reversal, but also providing a new method to quantify optically induced spin currents generated on femtosecond timescales.

  16. Probing electron transfer processes in YPO(4):Ce, Sm by combined synchrotron-laser excitation spectroscopy.

    PubMed

    Poolton, N R J; Bos, A J J; Jones, G O; Dorenbos, P

    2010-05-12

    Yttrium phosphate co-doped with cerium and samarium acts as a charge storage phosphor, but in highly doped material (0.5% co-doping levels), the proximity of defects leads to the uncontrolled non-radiative loss of stored charge through tunnelling. In order to characterize these defects, their mutual interactions and intra-pair charge transfer routes, experiments have been undertaken in which a laser probe is deployed during luminescence excitation using a synchrotron. Two modes of operation are described; in each case, the laser (2.8 eV) probes only Sm(2+) ions, and the detection is set to monitor exclusively Ce(3+) 5d-4f emission. Mode 1: the sample is pumped with monochromatic synchrotron photons in the range 4.5-12 eV, and the resultant charge populations probed with the laser 30 s later; this has the effect of sampling electrons trapped at Sm(2+) that are in quasi-equilibrium. Here, a clear transition between a sub-bandgap Urbach tail region and excitations above the mobility edge is especially apparent, enabling an accurate value of the conduction band energy of YPO(4) to be determined, 9.20 eV. Furthermore, the Sm(2+) and Ce(3+) ground state energies can be positioned within the bandgap (6.8 eV and 3.85 eV above the top of the valence band, respectively). Mode 2: the sample is pumped with monochromatic synchrotron photons in the range 4.5-12 eV and, during this pumping process, the laser probe is activated. This more dynamic process probes direct electron transfer excitation processes between spatially correlated Sm-Ce defect pairs, via their excited states; the laser probe enhances the Ce(3+) emission if direct electron transfer from the Ce(3+) ground state to the excited states of Sm(2+) is being pumped, or quenches the luminescence if the Ce(3+) excited states are pumped. The experiments allow for a precise measure of the difference in energy between the Sm(2+) and Ce(3+) ground states (2.98 eV).

  17. Quenching of nitrogen dioxide fluorescence excited by a He-Cd laser

    SciTech Connect

    Kireev, S.V.; Shnyrev, S.L.

    1994-06-01

    The effect of some buffer gases on nitrogen dioxide fluorescence excited by a 0.44-{mu}m He-Cd laser is investigated. The rate constants of fluorescence self-quenching by buffer gases are measured. The cross sections of collision quenching of fluorescence are determined. The obtained results can be used for nitrogen dioxide monitoring in the atmosphere. 12 refs., 3 figs., 1 tab.

  18. Strongly Enhanced Laser Absorption and Electron Acceleration via Resonant Excitation of Surface Plasma Waves

    NASA Astrophysics Data System (ADS)

    Raynaud, M.; Riconda, C.; Adam, J. C.; Heron, A.

    2010-02-01

    The possibility of creating enhanced fast electron bunches via the excitation of surface plasma waves (SPW) in laser overdense plasma interaction has been investigated by mean of relativistic one dimension motion of a test electron in the field of the surface plasma wave study and with two-dimensional (2D) Particle-In-Cell (PIC) numerical simulations. Strong electron acceleration together with a dramatic increase, up to 70%, of light absorption by the plasma is observed.

  19. Generation of terahertz radiation by a surface ballistic photocurrent in semiconductors under subpicosecond laser excitation

    SciTech Connect

    Ziaziulia, P. A.; Malevich, V. L.; Manak, I. S.; Krotkus, A.

    2012-02-15

    An analytical model describing the onset of a surface ballistic photocurrent in cubic semiconductors under femtosecond laser excitation is proposed. It is shown that the contribution of the photocurrent component parallel to the surface to the generation of terahertz pulses may be comparable to the contribution of the perpendicular component. Consideration of the cubic symmetry of a semiconductor leads to the azimuthal anisotropy of terahertz generation.

  20. Study of cylindrical optical micro-structure technology used in infrared laser protection

    NASA Astrophysics Data System (ADS)

    Sun, Yanjun; Liu, Shunrui; Wang, Zhining; Zhao, Yixuan; Wu, Boqi; Leng, Yanbing; Wang, Li

    2016-10-01

    The paper aimed at the problem that strong absorption in visible wavelengths and equipment or operator injury caused by specular reflection exist in infrared laser protection technology to propose an infrared laser non-specular reflection optical micro-structure formed from optical window surface. It has the function of little effect on visible light transmission and large-angle scattering to 1064nm infrared laser in order to enable laser protection. The paper uses light track method to design double-side micro-cylindrical lens arrays with dislocation construction. Array period T and curvature radius of lens units R should meet the condition:0infrared laser reflection is about 75%, divergence angle is greater than 30%,which greatly reduces the single-directivity reflection echo energy of laser to achieve the purpose of laser protection.

  1. Excitation Mechanism of H, He, C, and F Atoms in Metal-Assisted Atmospheric Helium Gas Plasma Induced by Transversely Excited Atmospheric-Pressure CO2 Laser Bombardment

    NASA Astrophysics Data System (ADS)

    Lie, Zener Sukra; Khumaeni, Ali; Kurihara, Kazuyoshi; Kurniawan, Koo Hendrik; Lee, Yong Inn; Fukumoto, Ken-ichi; Kagawa, Kiichiro; Niki, Hideaki

    2011-12-01

    To clarify the excitation mechanism of hydrogen in transversely excited atmospheric-pressure (TEA) CO2 laser-induced helium gas plasma, atomic emission characteristics of H, C, F, and He were studied using a Teflon sheet (thickness of 2 mm) attached to a metal subtarget. The TEA CO2 laser (750 mJ, 200 ns) was focused on the Teflon sheet in the surrounding He gas at 1 atm. Atomic emissions of H, C, F, and He occurred with a long lifetime, a narrow spectrum width, and a low-background spectrum. The correlation emission intensity curves of H--He and F--He indicated a parabolic functions. To explain the emission characteristics, we offered a model in which helium metastable atoms (He*) play an important role in the excitation processes; namely, atoms collide with helium metastable atoms (He*) to be ionized by the Penning effect, and then recombine with electrons to produce excited states, from which atomic emissions occur.

  2. Excitation Mechanism of H, He, C, and F Atoms in Metal-Assisted Atmospheric Helium Gas Plasma Induced by Transversely Excited Atmospheric-Pressure CO2 Laser Bombardment

    NASA Astrophysics Data System (ADS)

    Sukra Lie, Zener; Khumaeni, Ali; Kurihara, Kazuyoshi; Hendrik Kurniawan, Koo; Inn Lee, Yong; Fukumoto, Ken-ichi; Kagawa, Kiichiro; Niki, Hideaki

    2011-12-01

    To clarify the excitation mechanism of hydrogen in transversely excited atmospheric-pressure (TEA) CO2 laser-induced helium gas plasma, atomic emission characteristics of H, C, F, and He were studied using a Teflon sheet (thickness of 2 mm) attached to a metal subtarget. The TEA CO2 laser (750 mJ, 200 ns) was focused on the Teflon sheet in the surrounding He gas at 1 atm. Atomic emissions of H, C, F, and He occurred with a long lifetime, a narrow spectrum width, and a low-background spectrum. The correlation emission intensity curves of H-He and F-He indicated a parabolic functions. To explain the emission characteristics, we offered a model in which helium metastable atoms (He*) play an important role in the excitation processes; namely, atoms collide with helium metastable atoms (He*) to be ionized by the Penning effect, and then recombine with electrons to produce excited states, from which atomic emissions occur.

  3. Beat wave excitation of electron plasma wave by relativistic cross focusing of cosh-Gaussian laser beams in plasma

    NASA Astrophysics Data System (ADS)

    Singh, Arvinder; Gupta, Naveen

    2015-06-01

    A scheme for beat wave excitation of electron plasma wave (EPW) is proposed by relativistic cross-focusing of two coaxial Cosh-Gaussian (ChG) laser beams in an under dense plasma. The plasma wave is generated on account of beating of two coaxial laser beams of frequencies ω1 and ω2 . The mechanism for laser produced nonlinearity is assumed to be relativistic nonlinearity in electron mass. Following moment theory approach in Wentzel Kramers Brillouin (W.K.B) approximation, the coupled differential equations governing the evolution of spot size of laser beams with distance of propagation have been derived. The relativistic nonlinearity depends not only on the intensity of first laser beam but also on the intensity of second laser beam. Therefore, propagation dynamics of one laser beam affect that of second beam and hence cross-focusing of the two laser beams takes place. Due to non uniform intensity distribution of pump laser beams, the background electron concentration gets modified. The amplitude of EPW, which depends on the background electron concentration, thus gets nonlinearly coupled with the laser beams. The effects of relativistic electron mass nonlinearity and the cross-focusing of pump beams on excitation of EPW have been incorporated. Numerical simulations have been carried out to investigate the effect of laser as well as plasma parameters on cross-focusing of laser beams and further its effect on power of excited EPW.

  4. Real-time quantum cascade laser-based infrared microspectroscopy in-vivo

    NASA Astrophysics Data System (ADS)

    Kröger-Lui, N.; Haase, K.; Pucci, A.; Schönhals, A.; Petrich, W.

    2016-03-01

    Infrared microscopy can be performed to observe dynamic processes on a microscopic scale. Fourier-transform infrared spectroscopy-based microscopes are bound to limitations regarding time resolution, which hampers their potential for imaging fast moving systems. In this manuscript we present a quantum cascade laser-based infrared microscope which overcomes these limitations and readily achieves standard video frame rates. The capabilities of our setup are demonstrated by observing dynamical processes at their specific time scales: fermentation, slow moving Amoeba Proteus and fast moving Caenorhabditis elegans. Mid-infrared sampling rates between 30 min and 20 ms are demonstrated.

  5. [Infrared tunable difference frequency laser source]. Final technical report, September 15, 1990--September 14, 1992

    SciTech Connect

    Curl, R.F.

    1992-12-31

    Purpose of grant was to purchase equipment necessary to construct an infrared laser source based on difference frequency generation in AgGaS{sub 2}. This continuous wave, single frequency, tunable infrared source has been assembled and is being used for infrared kinetic spectroscopy of small free radicals important in combustion. Infrared spectra are given for the Q-branch of a combination band (11{sup 1}1) of N{sub 2}O, and for the transient in CO produced by flash photolysis of acetone in various vibrational states.

  6. [Infrared tunable difference frequency laser source]. Final technical report, September 15, 1990--September 14, 1992

    SciTech Connect

    Curl, R.F.

    1992-01-01

    Purpose of grant was to purchase equipment necessary to construct an infrared laser source based on difference frequency generation in AgGaS[sub 2]. This continuous wave, single frequency, tunable infrared source has been assembled and is being used for infrared kinetic spectroscopy of small free radicals important in combustion. Infrared spectra are given for the Q-branch of a combination band (11[sup 1]1) of N[sub 2]O, and for the transient in CO produced by flash photolysis of acetone in various vibrational states.

  7. Monitoring coherent electron wave packet excitation dynamics by two-color attosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Yuan, Kai-Jun; Bandrauk, André D.

    2016-11-01

    We propose a method to monitor coherent electron wave packet (CEWP) excitation dynamics with two-color attosecond laser pulses. Simulations are performed on aligned H2+ by numerically solving the three-dimensional time-dependent Schrödinger equation with combinations of a resonant linearly polarized λl= 100/70 nm pump pulse and a circularly polarized λc=5 nm attosecond probe pulse. It is found that time dependent diffraction patterns in molecular frame photoelectron angular distributions (MFPADs) produced by the circular probe pulse exhibit sensitivity to the molecular alignments and time-dependent geometry of the CEWPs during and after the coherent excitation between the ground and excited states induced by the linear pump pulse. The time dependent MFPADs are described by an ultrafast diffraction model for the ionization of the bound CEWPs.

  8. Full elastic characterization of absorptive rubber using laser excited guided ultrasonic waves

    NASA Astrophysics Data System (ADS)

    Verstraeten, Bert; Xu, Xiadong; Martinez, Loïc; Glorieux, Christ

    2012-05-01

    Because of the highly damping nature of rubber, it is difficult to characterize its dynamic elastic properties using classical methods. In this paper, an experimental approach employing laser excited guided acoustic waves is proposed to accurately determine the real and imaginary part of the longitudinal and shear elastic modulus of a rubber layer. From the spatiotemporal evolution of a propagating laser excited Lamb wave measured by a laser Doppler vibrometer, which is scanning along a line perpendicular to a line of excitation, the phase velocity dispersion curves in the wave number - frequency domain are obtained. The results are interpreted in the framework of a detailed semianalytical study, analyzing the influence of elastic damping on the Lamb dispersion curves. This analysis is exploited to adequately fit the experimental dispersion curves and thus extract information about the elastic moduli and absorption coefficients of the rubber plate. The results are validated by a pulse-echo measurement, and by guided wave propagation results with the rubber layer connected in a bi-layer plate configuration to non-damping plates.

  9. Portable Raman spectroscopy using retina-safe (1550 nm) laser excitation

    NASA Astrophysics Data System (ADS)

    Brouillette, Carl; Smith, Wayne; Donahue, Michael; Huang, Hermes; Shende, Chetan; Sengupta, Atanu; Inscore, Frank; Patient, Michael; Farquharson, Stuart

    2012-06-01

    The use of portable Raman analyzers to identify unknown substances in the field has grown dramatically during the past decade. Measurements often require the laser beam to exit the confines of the sample compartment, which increases the potential of eye or skin damage. This is especially true for most commercial analyzers, which use 785 nm laser excitation. To overcome this safety concern, we have built a portable FT-Raman analyzer using a 1550 nm retina-safe excitation laser. Excitation at 1550 nm falls within the 1400 to 2000 nm retina-safe range, so called because the least amount of damage to the eye occurs in this spectral region. In contrast to wavelengths below 1400 nm, the retina-safe wavelengths are not focused by the eye, but are absorbed by the cornea, aqueous and vitreous humor. Here we compare the performance of this system to measurements of explosives at shorter wavelengths, as well as its ability to measure surface-enhanced Raman spectra of several chemicals, including the food contaminant melamine.

  10. Production of excited hydrogen molecule in a two-frequency chirped laser field

    NASA Astrophysics Data System (ADS)

    Datta, Avijit

    2017-02-01

    We have studied the population transfer in a 1+1 ladder system from v = 0, j = 0 of X 1 Σ g + state to J 1 Δ g +( v = 2, j = 2) state using two frequency-chirped laser pulses and thus to create excited hydrogen molecule. The first chirped frequency connects the ground level with two nonadiabatically coupled (i.e. dressed) intermediate levels, B 1 Σ u +( v = 14, j = 1) and C 1 Π u ( v = 3, j = 1), while the second chirped pulse excites the intermediate levels to the final target level. Here both the chirped fields produce adiabatic crossings due to the chirping actions and facilitate the population transfer to the higher levels. We reported complete population transfer to the highly excited bound electronic level J 1 Δ g +( v = 2, j = 2) using appropriate laser parameters of the two chirped laser pulses for all combinations of negatively and positively chirped fields. We explained the population transfer by drawing adiabatic dressed states including nonadiabatic interaction.

  11. Enhanced thermal radiation in terahertz and far-infrared regime by hot phonon excitation in a field effect transistor

    SciTech Connect

    Chung, Pei-Kang; Yen, Shun-Tung

    2014-11-14

    We demonstrate the hot phonon effect on thermal radiation in the terahertz and far-infrared regime. A pseudomorphic high electron mobility transistor is used for efficiently exciting hot phonons. Boosting the hot phonon population can enhance the efficiency of thermal radiation. The transistor can yield at least a radiation power of 13 μW and a power conversion efficiency higher than a resistor by more than 20%.

  12. Multi-photon excited coherent random laser emission in ZnO powders.

    PubMed

    Tolentino Dominguez, Christian; Gomes, Maria de A; Macedo, Zélia S; de Araújo, Cid B; Gomes, Anderson S L

    2015-01-07

    We report the observation and analysis of anti-Stokes coherent random laser (RL) emission from zinc oxide (ZnO) powders excited by one-, two- or three-photon femtosecond laser radiation. The ZnO powders were produced via a novel proteic sol-gel, low-cost and environmentally friendly route using coconut water in the polymerization step of the metal precursor. One- and two-photon excitation at 354 nm and 710 nm, respectively, generated single-band emissions centred at about 387 nm. For three-photon excitation, the emission spectra showed a strong ultraviolet (UV) band (380-396 nm) attributed to direct three-photon absorption from the valence band to the conduction band. The presence of an intensity threshold and a bandwidth narrowing of the UV band from about 20 to 4 nm are clear evidence of RL action. The observation of multiple sub-nanometre narrow peaks in the emission spectra for excitation above the RL threshold is consistent with random lasing by coherent feedback.

  13. Multi-photon excited coherent random laser emission in ZnO powders

    NASA Astrophysics Data System (ADS)

    Tolentino Dominguez, Christian; Gomes, Maria De A.; Macedo, Zélia S.; de Araújo, Cid B.; Gomes, Anderson S. L.

    2014-11-01

    We report the observation and analysis of anti-Stokes coherent random laser (RL) emission from zinc oxide (ZnO) powders excited by one-, two- or three-photon femtosecond laser radiation. The ZnO powders were produced via a novel proteic sol-gel, low-cost and environmentally friendly route using coconut water in the polymerization step of the metal precursor. One- and two-photon excitation at 354 nm and 710 nm, respectively, generated single-band emissions centred at about 387 nm. For three-photon excitation, the emission spectra showed a strong ultraviolet (UV) band (380-396 nm) attributed to direct three-photon absorption from the valence band to the conduction band. The presence of an intensity threshold and a bandwidth narrowing of the UV band from about 20 to 4 nm are clear evidence of RL action. The observation of multiple sub-nanometre narrow peaks in the emission spectra for excitation above the RL threshold is consistent with random lasing by coherent feedback.

  14. Pulsed infrared radiation excites cultured neonatal spiral and vestibular ganglion neurons by modulating mitochondrial calcium cycling.

    PubMed

    Lumbreras, Vicente; Bas, Esperanza; Gupta, Chhavi; Rajguru, Suhrud M

    2014-09-15

    Cochlear implants are currently the most effective solution for profound sensorineural hearing loss, and vestibular prostheses are under development to treat bilateral vestibulopathies. Electrical current spread in these neuroprostheses limits channel independence and, in some cases, may impair their performance. In comparison, optical stimuli that are spatially confined may result in a significant functional improvement. Pulsed infrared radiation (IR) has previously been shown to elicit responses in neurons. This study analyzes the response of neonatal rat spiral and vestibular ganglion neurons in vitro to IR (wavelength = 1,863 nm) using Ca(2+) imaging. Both types of neurons responded consistently with robust intracellular Ca(2+) ([Ca(2+)]i) transients that matched the low-frequency IR pulses applied (4 ms, 0.25-1 pps). Radiant exposures of ∼637 mJ/cm(2) resulted in continual neuronal activation. Temperature or [Ca(2+)] variations in the media did not alter the IR-evoked transients, ruling out extracellular Ca(2+) involvement or primary mediation by thermal effects on the plasma membrane. While blockage of Na(+), K(+), and Ca(2+) plasma membrane channels did not alter the IR-evoked response, blocking of mitochondrial Ca(2+) cycling with CGP-37157 or ruthenium red reversibly inhibited the IR-evoked [Ca(2+)]i transients. Additionally, the magnitude of the IR-evoked transients was dependent on ryanodine and cyclopiazonic acid-dependent Ca(2+) release. These results suggest that IR modulation of intracellular calcium cycling contributes to stimulation of spiral and vestibular ganglion neurons. As a whole, the results suggest selective excitation of neurons in the IR beam path and the potential of IR stimulation in future auditory and vestibular prostheses.

  15. Mid-infrared lasers for energy frontier plasma accelerators

    NASA Astrophysics Data System (ADS)

    Pogorelsky, I. V.; Polyanskiy, M. N.; Kimura, W. D.

    2016-09-01

    Plasma wake field accelerators driven with solid-state near-IR lasers have been considered as an alternative to conventional rf accelerators for next-generation TeV-class lepton colliders. Here, we extend this study to the mid-IR spectral domain covered by CO2 lasers. We conclude that the increase in the laser driver wavelength favors the regime of laser wake field acceleration with a low plasma density and high electric charge. This regime is the most beneficial for gamma colliders to be converted from lepton colliders via inverse Compton scattering. Selecting a laser wavelength to drive a Compton gamma source is essential for the design of such a machine. The revealed benefits from spectral diversification of laser drivers for future colliders and off-spring applications validate ongoing efforts in advancing the ultrafast CO2 laser technology.

  16. Viability of fibroblasts cultured under nutritional stress irradiated with red laser, infrared laser, and red light-emitting diode

    NASA Astrophysics Data System (ADS)

    Volpato, Luiz Evaristo Ricci; de Oliveira, Rodrigo Cardoso; Espinosa, Mariano Martinez; Bagnato, Vanderley Salvador; Machado, Maria A. A. M.

    2011-07-01

    Phototherapy is noninvasive, painless and has no known side effect. However, for its incorporation into clinical practice, more well-designed studies are necessary to define optimal parameters for its application. The viability of fibroblasts cultured under nutritional stress irradiated with either a red laser, an infrared laser, or a red light-emitting diode (LED) was analyzed. Irradiation parameters were: red laser (660 nm, 40 mW, 1 W/cm2), infrared laser (780 nm, 40 mW, 1 W/cm2), and red LED (637 +/- 15 nm, 40 mW, 1 W/cm2). All applications were punctual and performed with a spot with 0.4 mm2 of diameter for 4 or 8 s. The Kruskal-Wallis test and analysis of variance of the general linear model (p <= 0.05) were used for statistical analysis. After 72 h, phototherapy with low-intensity laser and LED showed no toxicity at the cellular level. It even stimulated methylthiazol tetrazolium assay (MTT) conversion and neutral red uptake of fibroblasts cultured under nutritional stress, especially in the group irradiated with infrared laser (p = 0.004 for MTT conversion and p < 0.001 for neutral red uptake). Considering the parameters and protocol of phototherapy used, it can be concluded that phototherapy stimulated the viability of fibroblasts cultured under nutritional deficit resembling those found in traumatized tissue in which cell viability is reduced.

  17. Nonlinear high voltage transmission line for transversely excited CO{sub 2} lasers

    SciTech Connect

    Ishi, Akira; Yasuoka, Koichi; Tamagawa, Tohru

    1995-12-31

    A high voltage Pulse with the risetime less than a few hundreds nanoseconds and the amplitude of several tens kilovolts is required to establish stable glow discharge excitation in high power pulsed gas lasers. To make the high voltage pulse fast, we have developed a nonlinear high voltage transmission line for transversely excited CO{sub 2} lasers. Fig.1 shows the electrical circuit of switching unit, pulse sharpening unit with nonlinear high voltage transmission line and discharge electrodes for TE-CO{sub 2} laser. The nonlinear high voltage transmission line is a 15-step LC ladder circuit that consists of linear inductors (L=6 {mu}H) and nonlinear BaTiO{sub 3} capacitors. Fig.2 shows a capacitance dependence on applied voltages. If an LC ladder circuit is constructed using a capacitor with the characteristics, the transmission velocity is fast at the high-voltage section and is slow at the low-voltage section. High voltage pulse with slow risetime is expected to be sharpen. The voltage and the current waveforms of the discharge measured at the point {open_quotes}c{close_quotes}. The risetime of 1{mu}s of the input voltage pulse was compressed to less than 200 ns at the output terminal of the LC ladder circuit and the outout pulse was applied to the discharge gap of the laser.

  18. Ultrafast spin-transfer torque driven by femtosecond pulsed-laser excitation

    NASA Astrophysics Data System (ADS)

    Koopmans, Bert

    A hot topic in the field of ultrafast laser-induced manipulation of the magnetic state is that of the role and exploitation of laser-induced spin currents. Intense debate has been triggered by claims that such a spin-transfer, e.g. in the form of super-diffusive spin currents over tens of nanometers, might be a main contributor to the demagnetization process in ferromagnetic thin films after femtosecond laser excitation. In this presentation the underlying concepts will be introduced and recent developments reviewed. Particularly we demonstrate the possibility to apply a laser-induced spin transfer torque on a free magnetic layer, using a non-collinear multilayer configuration consisting of a free in-plane layer on top of a perpendicularly magnetized injection layer, as separated by a nonmagnetic spacer. Interestingly, this approach allows for a quantitative measurement of the amount of spin transfer. Moreover, it might provide access to novel device architectures in which the magnetic state is controlled by fs laser pulses. Careful analysis of the resulting precession of the free layer allows us to quantify the applied torque, and distinguish between driving mechanisms based on laser-induced transfer of hot electrons versus a spin Seebeck effect due to the large thermal gradients. Further engineering of the layered structures in order to gain fundamental understanding and optimize efficiencies will be reported. A simple model that treats local non-equilibrium magnetization dynamics to spin transport effects via a spin-dependent chemical potential will be introduced.

  19. Portable optical-resolution photoacoustic microscopy with a pulsed laser diode excitation

    NASA Astrophysics Data System (ADS)

    Zeng, Lvming; Liu, Guodong; Yang, Diwu; Ji, Xuanrong

    2013-02-01

    Optical-resolution photoacoustic microscopy (OR-PAM) has been significantly improved in terms of spatial resolution, detection sensitivity, imaging speed, and penetration depth. However, the popular producibility of OR-PAM system is still limited by the size and cost of solid-state laser excitation. Here, we developed a portable laser-diode-based OR-PAM (LD-OR-PAM) system using a pulsed semiconductor laser source, which was operated at 905 ± 15 nm with a pulse energy as low as 4.9 μJ. The measured lateral resolution has been improved to ˜1.5 μm from hundreds of microns. The compact and inexpensive natures of LD-OR-PAM would promote the potential clinical applications such as in dermatology.

  20. Investigation of superelastic electron scattering by laser-excited Ba - Experimental procedures and results

    NASA Technical Reports Server (NTRS)

    Register, D. F.; Trajmar, S.; Fineman, M. A.; Poe, R. T.; Csanak, G.; Jensen, S. W.

    1983-01-01

    Differential (in angle) electron scattering experiments on laser-excited Ba-138 1P were carried out at 30- and 100-eV impact energies. The laser light was linearly polarized and located in the scattering plane. The superelastic scattering signal was measured as a function of polarization direction of the laser light with respect to the scattering plane. It was found at low electron scattering angles that the superelastic scattering signal was asymmetric to reflection of the polarization vector with respect to the scattering plane. This is in contradiction with theoretical predictions. An attempt was made to pinpoint the reason for this observation, and a detailed investigation of the influence of experimental conditions on the superelastic scattering was undertaken. No explanation for the asymmetry has as yet been found.

  1. Method and apparatus for producing laser radiation following two-photon excitation of a gaseous medium

    DOEpatents

    Bischel, William K. [Menlo Park, CA; Jacobs, Ralph R. [Livermore, CA; Prosnitz, Donald [Hamden, CT; Rhodes, Charles K. [Palo Alto, CA; Kelly, Patrick J. [Fort Lewis, WA

    1979-02-20

    Method and apparatus for producing laser radiation by two-photon optical pumping of an atomic or molecular gaseous medium and subsequent lasing action. A population inversion is created as a result of two-photon absorption of the gaseous species. Stark tuning is utilized, if necessary, in order to tune the two-photon transition into exact resonance. In particular, gaseous ammonia (NH.sub.3) or methyl fluoride (CH.sub.3 F) is optically pumped by a pair of CO.sub.2 lasers to create a population inversion resulting from simultaneous two-photon excitation of a high-lying vibrational state, and laser radiation is produced by stimulated emission of coherent radiation from the inverted level.

  2. Method and apparatus for producing laser radiation following two-photon excitation of a gaseous medium

    DOEpatents

    Bischel, W.K.; Jacobs, R.R.; Prosnitz, D.P.; Rhodes, C.K.; Kelly, P.J.

    1979-02-20

    Method and apparatus are disclosed for producing laser radiation by two-photon optical pumping of an atomic or molecular gaseous medium and subsequent lasing action. A population inversion is created as a result of two-photon absorption of the gaseous species. Stark tuning is utilized, if necessary, in order to tune the two-photon transition into exact resonance. In particular, gaseous ammonia (NH[sub 3]) or methyl fluoride (CH[sub 3]F) is optically pumped by a pair of CO[sub 2] lasers to create a population inversion resulting from simultaneous two-photon excitation of a high-lying vibrational state, and laser radiation is produced by stimulated emission of coherent radiation from the inverted level. 3 figs.

  3. Polarization spectroscopy and laser-locking for excitation of ultracold potassium atoms

    NASA Astrophysics Data System (ADS)

    Conover, Charles; Eberhart, Max; Adamson, Philip

    2016-05-01

    We report on the use of polarization spectroscopy to lock the frequency of an external-cavity diode laser to a the 4s - 4 p1/2 (770 nm), 4s - 4 p3/2 (767 nm) and 4s - 5 p1/2 and 4s - 5 p3/2 (405 nm) transitions in potassium. A rate equation model is in good agreement with the observed lineshapes and the D2 transition lineshapes agree with prior experiments. We have used the dispersion shaped lines to lock the frequency of lasers for probing a magneto-optical trap's density on the D1 line and for stepwise excitation of potassium Rydberg states using the 4s - 5 p3/2 transition. The technique has proven particularly helpful by enabling modulation-free locking of blue diode lasers. This research was supported by the National Science Foundation under Grant PHY-1126599.

  4. THz and infrared excitation spectrum below the Jahn-Teller transition in Sr3Cr2O8

    NASA Astrophysics Data System (ADS)

    Wang, Zhe; Schmidt, Michael; Günther, Axel; Schaile, Sebastian; Pascher, Nikola; Mayr, Franz; Goncharov, Yurii; Krug von Nidda, Hans-Albrecht; Loidl, Alois; Quintero-Castro, Diana; Islam, A. T. M. N.; Lake, Bella; Deisenhofer, Joachim

    2012-02-01

    We report on optical excitations observed recently in Sr3Cr2O8 by THz and infrared spectroscopy. Low-energy excitations below 3 THz are detected by THz time domain spectroscopy. These excitations can be divided into two different classes according to the temperature-dependent properties. One is emergent right below the Jahn-Teller transition temperature, which is determined by specific heat measurement to occur at 285 K [1, 2]. The other appears only below 100 K, where the fluctuations are sufficiently suppressed, consistent with the temperature dependence of low-energy Raman modes [3]. Infrared transmission measurements reveal a broad crystal-field excitation, which can be associated with an electronic transition from E to T2 orbital states. [4pt] [1] Zhe Wang et al., Phys. Rev. B 83, 201102 (2011) [0pt] [2] D. L. Quintero-Castro et al., Phys. Rev. B 81, 014415 (2010) [0pt] [3] D. Wulferding et al., Phys. Rev. B 84, 064419 (2011)

  5. The edge detection method of the infrared imagery of the laser spot

    NASA Astrophysics Data System (ADS)

    Che, Jinxi; Zhang, Jinchun; Li, Zhongmin

    2016-01-01

    In the jamming effectiveness experiments, in which the thermal infrared imager was interfered by the CO2 Laser, in order to evaluate the jamming effect of the thermal infrared imager by the CO2 Laser, it was needed to analyses the obtained infrared imagery of laser spot. Because the laser spot pictures obtained from the thermal infrared imager are irregular, the edge detection is an important process. The image edge is one of the most basic characteristics of the image, and it contains most of the information of the image. Generally, because of the thermal balance effect, the partly temperature of objective is no quite difference; therefore the infrared imagery's ability of reflecting the local detail of object is obvious week. At the same time, when the information of heat distribution of the thermal imagery was combined with the basic information of target, such as the object size, the relative position of field of view, shape and outline, and so on, the information just has more value. Hence, it is an important step for making image processing to extract the objective edge of the infrared imagery. Meanwhile it is an important part of image processing procedure and it is the premise of many subsequent processing. So as to extract outline information of the target from the original thermal imagery, and overcome the disadvantage, such as the low image contrast of the image and serious noise interference, and so on, the edge of thermal imagery needs detecting and processing. The principles of the Roberts, Sobel, Prewitt and Canny operator were analyzed, and then they were used to making edge detection on the thermal imageries of laser spot, which were obtained from the jamming effect experiments of CO2 laser jamming the thermal infrared imager. On the basis of the detection result, their performances were compared. At the end, the characteristics of the operators were summarized, which provide reference for the choice of edge detection operators in thermal imagery

  6. Quantitative analysis of solids in motion by transient infrared emission spectroscopy using hot-gas jet excitation

    SciTech Connect

    Jones, R.W.; McClelland, J.F. )

    1990-10-01

    Quantitative compositional analysis of optically thick solids in motion is demonstrated by using transient infrared emission spectroscopy (TIRES). TIRES greatly reduces the self-absorption that normally degrades conventional emission spectra so that they closely resemble blackbody spectra. Quantitative compositional analyses of poly((methyl methacrylate)-co-(butyl methacrylate)) and poly(ethylene-co-(vinyl acetate)) with standard errors of prediction under 1% were achieved with only a few seconds of data acquisition using principal component regression. Use of a hot-gas jet in place of a laser in the TIRES technique allows study of materials that do not absorb strongly at common laser wavelengths while reducing cost and complexity.

  7. Development of long wavelength semiconductor diode lasers near 28 microns for use in infrared heterodyne spectrometers

    NASA Technical Reports Server (NTRS)

    Linden, K. J.

    1984-01-01

    The development of tunable diode lasers operating in the 28 micrometers spectral region for use in infrared heterodyne spectrometers is reported. A process capable of yielding lasers emitting 500 micron W of multimode power, 112 micron W in a true single mode and true single mode operation at laser currents of up to 35% above threshold was developed. Results were obtained from narrow mesastripe (20 micrometer wide) short cavity (120 micrometer length) laser configurations. Six stripe geometry lasers, with a variety of cavity widths and lengths were delivered. The techniques to fabricate such devices was obtained and the long term reliability of such lasers by reproducible electrical and optical output characteristics fabrication from lasers are demonstrated.

  8. Nanosurgery of cells and chromosomes using near-infrared twelve-femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Uchugonova, Aisada; Lessel, Matthias; Nietzsche, Sander; Zeitz, Christian; Jacobs, Karin; Lemke, Cornelius; König, Karsten

    2012-10-01

    Laser-assisted surgery based on multiphoton absorption of near-infrared laser light has great potential for high precision surgery at various depths within the cells and tissues. Clinical applications include refractive surgery (fs-LASIK). The non-contact laser method also supports contamination-free cell nanosurgery. In this paper we describe usage of an ultrashort femtosecond laser scanning microscope for sub-100 nm surgery of human cells and metaphase chromosomes. A mode-locked 85 MHz Ti:Sapphire laser with an M-shaped ultrabroad band spectrum (maxima: 770 nm/830 nm) and an in situ pulse duration at the target ranging from 12 fs up to 3 ps was employed. The effects of laser nanoprocessing in cells and chromosomes have been quantified by atomic force microscopy. These studies demonstrate the potential of extreme ultrashort femtosecond laser pulses at low mean milliwatt powers for sub-100 nm surgery of cells and cellular organelles.

  9. Electronic Relaxation after Resonant Laser Excitation of Cr in Superfluid Helium Nanodroplets

    PubMed Central

    2013-01-01

    Chromium (Cr) atoms embedded into helium nanodroplets (HeN) are ejected from the droplets upon photoexcitation. During ejection they undergo electronic relaxation resulting in bare Cr atoms in various excited states. In a study of the relaxation process we present absorption spectra observed via laser induced fluorescence and beam depletion as well as dispersed fluorescence spectra and time-resolved fluorescence measurements. Broad and shifted absorption structures were found for the strong z7P° ← a7S3 and y7P° ← a7S3 excitations from the ground state. Emission lines are, in contrast, very narrow, which indicates that fluorescence is obtained from bare excited Cr atoms after ejection. Upon excitation into the y7P2,3,4° states we observed fluorescence from y7P2°, z5P1,2,3°, and z7P2,3,4°, indicating that these states are populated by electronic relaxation during the ejection processes. Relative population ratios are obtained from the intensities of individual spectral lines. Excitation into the z7P2,3,4° states resulted in fluorescence only from z7P2°. Estimates of the time duration of the ejection process are obtained from time-resolved measurements. PMID:23410146

  10. Novel mid-infrared lasers with compressively strained InAsSb active regions

    SciTech Connect

    Kurtz, S.R.; Biefeld, R.M.; Allerman, A.A.

    1997-02-01

    Mid-infrared lasers grown by MOCVD with AlAsSb claddings and strained InAsSb active regions are reported. A 3.8--3.9 {micro}m injection laser with a pseudomorphic InAsSb multiple quantum well active region lased at 210 K under pulsed operation. A semi-metal layer acts as an internal electron source for the injection laser. An optically pumped laser with an InAsSb/InAsP strained-layer superlattice active region was demonstrated at 3.7 {micro}m, 240 K.

  11. A stable, high power optically pumped far infrared laser system

    NASA Technical Reports Server (NTRS)

    Farhoomand, Jam; Pickett, Herbert M.

    1988-01-01

    The generation of 1.25 watts of CW laser power at the 119-micron (2522.8 GHz) methanol line is reported. The maximum frequency fluctuation of the free running laser is less than + or - 100 kHz per hour. This laser has also been tested on numerous other lines ranging from 403.7 GHz (HCOOH) to 5260 GHz (CH3OD) with improved power and stability.

  12. Fluorescence properties and energy transfer study of Er3+/Nd3+ doped fluorophosphate glass pumped at 800 and 980 nm for mid-infrared laser applications

    NASA Astrophysics Data System (ADS)

    Tian, Ying; Xu, Rongrong; Hu, Lili; Zhang, Junjie

    2012-04-01

    The fluorescence properties of 2.7 μm emission as well as near infrared emissions in Er3+/Nd3+ doped fluorophosphate glasses are investigated under 800 and 980 nm excitation. The fluorescence dynamics and energy transfer processes between Er and Nd ions in different pumping schemes are reported. Three Judd-Ofelt intensity parameters, energy transfer microparameters, and efficiency have been determined using the Judd-Ofelt and Förster-Dexter theories. The calculated energy transfer efficiency of the Er3+:4I13/2 level to the Nd3+:4I15/2 level is as high as 83.91%. The results indicate that Nd3+ may be an efficient sensitizer for Er3+ to obtain mid-infrared emission and the more suitable pumping scheme of 2.7 μm laser applications for Er3+/Nd3+ doped fluorophosphate glass is 980 nm excitation.

  13. Mode Control and Tunability in Rf-Excited Carbon - Waveguide Lasers.

    NASA Astrophysics Data System (ADS)

    Hill, Christopher Alexander

    Available from UMI in association with The British Library. The first chapter describes some uses and advantages of the CO_2 waveguide laser, with a brief historical review. The rest of the thesis, apart from routine accounts of apparatus and summaries of parts of the literature, reports several pieces of original work. These have aimed mainly at a better understanding of waveguide laser models and at applying them in detail to real devices, with a general emphasis on the design of highly tunable cw CO_2 waveguide oscillators. Chapter 2 has a formal statement of passive waveguide transmission theory and suggests that some recent experimental work elsewhere can be explained by assuming that the wavefronts of EH_{1_{rm m} } guide modes are curved. Chapter 4 shows that the seminal paper on waveguide reflector EH_{11} coupling losses by Abrams (1972) contains an error which leads to predictions significantly different from those of Degnan and Hall (1973). It is resolved by introducing the correct phase shifts phi_{rm p }(z,R_{rm M} ) for the Laguerre-Gaussian beams reflected from a spherical mirror. The two methods of calculation (Gaussian -beam expansion and diffraction integral) are then seen to yield the same results. Also, chapter 4 contains a detailed review of published coupling loss theory for plane mirrors. Surprising errors and inconsistencies are revealed. Chapter 6 discusses the application of Rigrod -type modelling to waveguide gas lasers, especially those with significant distributed loss. It reports an attempt to characterize an rf-excited waveguide CO_2 laser whose waveguide losses are certainly significant. For another such laser (chapter 7) the dependence of gain on rf excitation frequency is confirmed. Chapter 8 develops a multimode model of a dual -Case I waveguide laser with one tilted mirror. This description fits many commercial lasers; if a diffraction grating is modelled as a lossy plane mirror with a wavelength-dependent tilt, it also fits many

  14. 3rd Tech DeltaSphere-3000 Laser 3D Scene Digitizer infrared laser scanner hazard analysis.

    SciTech Connect

    Augustoni, Arnold L.

    2005-02-01

    A laser hazard analysis and safety assessment was performed for the 3rd Tech model DeltaSphere-3000{reg_sign} Laser 3D Scene Digitizer, infrared laser scanner model based on the 2000 version of the American National Standard Institute's Standard Z136.1, for the Safe Use of Lasers. The portable scanner system is used in the Robotic Manufacturing Science and Engineering Laboratory (RMSEL). This scanning system had been proposed to be a demonstrator for a new application. The manufacture lists the Nominal Ocular Hazard Distance (NOHD) as less than 2 meters. It was necessary that SNL validate this NOHD prior to its use as a demonstrator involving the general public. A formal laser hazard analysis is presented for the typical mode of operation for the current configuration as well as a possible modified mode and alternative configuration.

  15. Spectroscopic properties in Er(3+)-doped germanotellurite glasses and glass ceramics for mid-infrared laser materials.

    PubMed

    Kang, Shiliang; Xiao, Xiudi; Pan, Qiwen; Chen, Dongdan; Qiu, Jianrong; Dong, Guoping

    2017-03-07

    Transparent Er(3+)-doped germanotellurite glass ceramics (GCs) with variable Te/Ge ratio were prepared by controllable heat-treated process. X-ray diffraction (XRD) and transmission electron microscope (TEM) confirmed the formation of nanocrystals in glass matrix. Raman spectra were used to investigate the evolution of glass structure and photon energy. Fourier transform infrared (FTIR) spectra were introduced to characterize the change of hydroxyl group (OH(-)) content. Enhanced 2.7 μm emission was achieved from Er(3+)-doped GCs upon excitation with a 980 nm laser diode (LD), and the influence of GeO2 concentration and heat-treated temperature on the spectroscopic properties were also discussed in detail. It is found that the present Er(3+)-doped GC possesses large stimulated emission cross section at around 2.7 μm (0.85 × 10(-20) cm(2)). The advantageous spectroscopic characteristics suggest that the obtained GC may be a promising material for mid-infrared fiber lasers.

  16. Spectroscopic properties in Er3+-doped germanotellurite glasses and glass ceramics for mid-infrared laser materials

    NASA Astrophysics Data System (ADS)

    Kang, Shiliang; Xiao, Xiudi; Pan, Qiwen; Chen, Dongdan; Qiu, Jianrong; Dong, Guoping

    2017-03-01

    Transparent Er3+-doped germanotellurite glass ceramics (GCs) with variable Te/Ge ratio were prepared by controllable heat-treated process. X-ray diffraction (XRD) and transmission electron microscope (TEM) confirmed the formation of nanocrystals in glass matrix. Raman spectra were used to investigate the evolution of glass structure and photon energy. Fourier transform infrared (FTIR) spectra were introduced to characterize the change of hydroxyl group (OH‑) content. Enhanced 2.7 μm emission was achieved from Er3+-doped GCs upon excitation with a 980 nm laser diode (LD), and the influence of GeO2 concentration and heat-treated temperature on the spectroscopic properties were also discussed in detail. It is found that the present Er3+-doped GC possesses large stimulated emission cross section at around 2.7 μm (0.85 × 10‑20 cm2). The advantageous spectroscopic characteristics suggest that the obtained GC may be a promising material for mid-infrared fiber lasers.

  17. Spectroscopic properties in Er3+-doped germanotellurite glasses and glass ceramics for mid-infrared laser materials

    PubMed Central

    Kang, Shiliang; Xiao, Xiudi; Pan, Qiwen; Chen, Dongdan; Qiu, Jianrong; Dong, Guoping

    2017-01-01

    Transparent Er3+-doped germanotellurite glass ceramics (GCs) with variable Te/Ge ratio were prepared by controllable heat-treated process. X-ray diffraction (XRD) and transmission electron microscope (TEM) confirmed the formation of nanocrystals in glass matrix. Raman spectra were used to investigate the evolution of glass structure and photon energy. Fourier transform infrared (FTIR) spectra were introduced to characterize the change of hydroxyl group (OH−) content. Enhanced 2.7 μm emission was achieved from Er3+-doped GCs upon excitation with a 980 nm laser diode (LD), and the influence of GeO2 concentration and heat-treated temperature on the spectroscopic properties were also discussed in detail. It is found that the present Er3+-doped GC possesses large stimulated emission cross section at around 2.7 μm (0.85 × 10−20 cm2). The advantageous spectroscopic characteristics suggest that the obtained GC may be a promising material for mid-infrared fiber lasers. PMID:28266570

  18. Integrated ultraviolet and tunable mid-infrared laser source for analyses of proteins

    NASA Astrophysics Data System (ADS)

    Hazama, Hisanao; Takatani, Yoshiaki; Awazu, Kunio

    2007-02-01

    Mass spectrometry using matrix-assisted laser desorption/ionization (MALDI) technique is one of the most widely used method to analyze proteins in biological research fields. However, it is difficult to analyze insoluble proteins which have important roles in researches on disease mechanisms or in developments of drugs by using ultraviolet (UV) lasers which have commonly been used for MALDI. Recently, a significant improvement in MALDI process of insoluble proteins using a combination of a UV nitrogen laser and a tunable mid-infrared (MIR) free electron laser (FEL) was reported. Since the FEL is a very large and expensive equipment, we have developed a tabletop laser source which can generate both UV and tunable MIR lasers. A tunable MIR laser (5.5-10 μm) was obtained by difference frequency generation (DFG) between a Nd:YAG and a tunable Cr:forsterite lasers using two AgGaS II crystals. The MIR laser can generate pulses with an energy of up to 1.4 mJ at a repetition rate of 10 Hz. A UV laser was obtained by third harmonic generation of a Nd:YAG laser splitted from that used for DFG. A time interval between the UV and the MIR laser pulses can be adjusted with a variable optical delay.

  19. INTERACTION OF LASER RADIATION WITH MATTER: Luminescence of crystals excited by a KrCl laser and a subnanosecond electron beam

    NASA Astrophysics Data System (ADS)

    Lipatov, E. I.; Tarasenko, Viktor F.; Orlovskii, Viktor M.; Alekseev, S. B.

    2005-08-01

    Luminescence of crystals of natural spodumene and natural diamond of the type IIa is studied upon excitation by a laser at a wavelength of 222 nm and by a subnanosecond avalanche electron beam (SAEB) formed in air at the atmospheric pressure. The photoluminescence spectra of spodumene and diamond are shown to exhibit additional bands, which are absent upon SAEB excitation. It is demonstrated that SAEB excitation allows one to analyse various crystals under normal conditions without using any vacuum equipment.

  20. Mid-infrared laser ablation of intraocular acrylic lenses

    NASA Astrophysics Data System (ADS)

    Spyratou, E.; Makropoulou, M.; Bacharis, C.; Serafetinides, A. A.

    2007-05-01

    Ablation rates measurements with free-running Er:YAG laser (λ=2.94 μm) were performed in hydrophilic acrylic intraocular lenses. We studied the role of water in the laser ablation mechanisms by using hydrophilic lenses with different concentrations of H II0 and D II0. A mathematical model simulated the experimental results.

  1. Ultrafast excited-state dynamics and fluorescence deactivation of near-infrared fluorescent proteins engineered from bacteriophytochromes

    NASA Astrophysics Data System (ADS)

    Zhu, Jingyi; Shcherbakova, Daria M.; Hontani, Yusaku; Verkhusha, Vladislav V.; Kennis, John T. M.

    2015-08-01

    Near-infrared fluorescent proteins, iRFPs, are recently developed genetically encoded fluorescent probes for deep-tissue in vivo imaging. Their functions depend on the corresponding fluorescence efficiencies and electronic excited state properties. Here we report the electronic excited state deactivation dynamics of the most red-shifted iRFPs: iRFP702, iRFP713 and iRFP720. Complementary measurements by ultrafast broadband fluorescence and absorption spectroscopy show that single exponential decays of the excited state with 600 ~ 700 ps dominate in all three iRFPs, while photoinduced isomerization was completely inhibited. Significant kinetic isotope effects (KIE) were observed with a factor of ~1.8 in D2O, and are interpreted in terms of an excited-state proton transfer (ESPT) process that deactivates the excited state in competition with fluorescence and chromophore mobility. On this basis, new approaches for rational molecular engineering may be applied to iRFPs to improve their fluorescence.

  2. Damage detection in membrane structures using non-contact laser excitation and wavelet transformation

    NASA Astrophysics Data System (ADS)

    Huda, Feblil; Kajiwara, Itsuro; Hosoya, Naoki

    2014-08-01

    In this paper, a vibration testing and health monitoring system based on an impulse response excited by laser is proposed to detect damage in membrane structures. A high power Nd: YAG pulse laser is used to supply an ideal impulse to a membrane structure by generating shock waves via laser-induced breakdown in air. A health monitoring apparatus is developed with this vibration testing system and a damage detecting algorithm which only requires the vibration mode shape of the damaged membrane. Artificial damage is induced in membrane structure by cutting and tearing the membrane. The vibration mode shapes of the membrane structure extracted from vibration testing by using the laser-induced breakdown and laser Doppler vibrometer are then analyzed by 2-D continuous wavelet transformation. The location of damage is determined by the dominant peak of the wavelet coefficient which can be seen clearly by applying a boundary treatment and the concept of an iso-surface to the 2-D wavelet coefficient. The applicability of the present approach is verified by finite element analysis and experimental results, demonstrating the ability of the method to detect and identify the positions of damage induced on the membrane structure.

  3. CO2 laser-forward looking infrared /FLIR/ integration concepts

    NASA Astrophysics Data System (ADS)

    Osche, G. R.; Luck, C. F.; Seavey, R. E.; Phelan, R. K.

    1980-01-01

    A survey of techniques for combining active laser functions with passive thermal imaging systems is presented along with some recent accomplishments. Emphasis is placed on the advantages of integrating CO2 lasers with the 8 - 12 micron thermal sensors arising from the commonality of operating wavelengths. Compatibility of performance, eye safety, and sharing of optical components are pointed out as the primary driving factors which favor CO2 lasers. Recent accomplishments include the development of the first U.S. CO2 laser rangefinder which has been integrated with the thermal sensor for a high survivability test vehicle. A fully modularized, sealed-off CO2 TEA laser rangefinder developed for the U.S. Army is also described.

  4. Complementary analysis of tissue homogenates composition obtained by Vis and NIR laser excitations and Raman spectroscopy.

    PubMed

    Staniszewska-Slezak, Emilia; Malek, Kamilla; Baranska, Malgorzata

    2015-08-05

    Raman spectroscopy and four excitation lines in the visible (Vis: 488, 532, 633 nm) and near infrared (NIR: 785 nm) were used for biochemical analysis of rat tissue homogenates, i.e. myocardium, brain, liver, lung, intestine, and kidney. The Vis Raman spectra are very similar for some organs (brain/intestines and kidney/liver) and dominated by heme signals when tissues of lung and myocardium were investigated (especially with 532 nm excitation). On the other hand, the NIR Raman spectra are specific for each tissue and more informative than the corresponding ones collected with the Vis excitations. The spectra analyzed without any special pre-processing clearly illustrate different chemical composition of each tissue and give information about main components e.g. lipids or proteins, but also about the content of some specific compounds such as amino acid residues, nucleotides and nucleobases. However, in order to obtain the whole spectral information about tissues complex composition the spectra of Vis and NIR excitations should be collected and analyzed together. A good agreement of data gathered from Raman spectra of the homogenates and those obtained previously from Raman imaging of the tissue cross-sections indicates that the presented here approach can be a method of choice for an investigation of biochemical variation in animal tissues. Moreover, the Raman spectral profile of tissue homogenates is specific enough to be used for an investigation of potential pathological changes the organism undergoes, in particular when supported by the complementary FTIR spectroscopy.

  5. Complementary analysis of tissue homogenates composition obtained by Vis and NIR laser excitations and Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Staniszewska-Slezak, Emilia; Malek, Kamilla; Baranska, Malgorzata

    2015-08-01

    Raman spectroscopy and four excitation lines in the visible (Vis: 488, 532, 633 nm) and near infrared (NIR: 785 nm) were used for biochemical analysis of rat tissue homogenates, i.e. myocardium, brain, liver, lung, intestine, and kidney. The Vis Raman spectra are very similar for some organs (brain/intestines and kidney/liver) and dominated by heme signals when tissues of lung and myocardium were investigated (especially with 532 nm excitation). On the other hand, the NIR Raman spectra are specific for each tissue and more informative than the corresponding ones collected with the Vis excitations. The spectra analyzed without any special pre-processing clearly illustrate different chemical composition of each tissue and give information about main components e.g. lipids or proteins, but also about the content of some specific compounds such as amino acid residues, nucleotides and nucleobases. However, in order to obtain the whole spectral information about tissues complex composition the spectra of Vis and NIR excitations should be collected and analyzed together. A good agreement of data gathered from Raman spectra of the homogenates and those obtained previously from Raman imaging of the tissue cross-sections indicates that the presented here approach can be a method of choice for an investigation of biochemical variation in animal tissues. Moreover, the Raman spectral profile of tissue homogenates is specific enough to be used for an investigation of potential pathological changes the organism undergoes, in particular when supported by the complementary FTIR spectroscopy.

  6. Excitation-induced germanium quantum dot growth on silicon(100)-2X1 by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Er, Ali Oguz

    2011-12-01

    Self-assembled Ge quantum dots (QD) are grown on Si(100)-(2x1) with laser excitation during growth processes by pulsed laser deposition (PLD). In situ reflection-high energy electron diffraction (RHEED) and post-deposition atomic force microscopy (AFM) are used to study the growth dynamics and morphology of the QDs. A Q-switched Nd:YAG laser (lambda = 1064 nm, 40 ns pulse width, 5 J/cm2 fluence, and 10 Hz repetition rate) were used to ablate germanium and irradiate the silicon substrate. Ge QD formation on Si(100)-(2x1) with different substrate temperatures and excitation laser energy densities was studied. The excitation laser reduces the epitaxial growth temperature to 250 °C for a 22 ML film. In addition, applying the excitation laser to the substrate during the growth changes the QD morphology and density and improves the uniformity of quantum dots fabricated at 390 °C. At room temperature, applying the excitation laser during growth decreases the surface roughness although epitaxial growth could not be achieved. We have also studied the surface diffusion coefficient of Ge during pulsed laser deposition of Ge on Si(100)-(2x1) with different excitation laser energy densities. Applying the excitation laser to the substrate during the growth increases the surface diffusion coefficient, changes the QD morphology and density, and improves the size uniformity of the grown quantum dots. To study the effect of high intensity ultralast laser pulses, Ge quantum dots on Si(I00) were grown in an ultrahigh vacuum (UHV) chamber (base pressure ˜7.0x10 -10 Torr) by femtosecond pulsed laser deposition. The results show that excitation laser reduces the epitaxial growth temperature to ˜70 °C. This result could lead to nonthermal method to achieve low temperature epitaxy which limits the redistribution of impurities, reduces intermixing in heteroepitaxy, and restricts the generation of defects by thermal stress. We have ruled out thermal effects and some of the desorption

  7. Pulsed laser imaging of rapid Ca2+ gradients in excitable cells.

    PubMed Central

    Monck, J R; Robinson, I M; Escobar, A L; Vergara, J L; Fernandez, J M

    1994-01-01

    Excitable cells are thought to respond to action potentials by forming short lived and highly localized Ca2+ gradients near sites of Ca2+ entry or near the site of Ca2+ release by intracellular stores. However, conventional imaging techniques lack the spatial and temporal resolution to capture these gradients. Here we demonstrate the use of pulsed-laser microscopy to measure Ca2+ gradients with submicron spatial resolution and millisecond time resolution in two preparations where the Ca2+ signal is thought to be fast and highly localized: adrenal chromaffin cells, where the entry of Ca2+ through voltage dependent Ca2+ channels triggers exocytotic fusion; and skeletal muscle fibers, where intracellular Ca2+ release from the sarcoplasmic reticulum initiates contraction. In chromaffin cells, Ca2+ gradients developed over 10-100 ms and were initially restricted to discrete submembrane domains, or hot spots, before developing into complete rings of elevated Ca2+ concentration. In frog skeletal muscle large, short-lived (approximately 6 ms) Ca2+ gradients were observed within individual sarcomeres following induction of action potentials. The pulsed laser imaging approach permits, for the first time, the capture and critical examination of rapid Ca2+ signaling events such as those underlying excitation-secretion and excitation-contraction coupling. Images FIGURE 1 FIGURE 2 FIGURE 3 FIGURE 4 FIGURE 5 FIGURE 6 PMID:7948669

  8. Control of crystallographic orientation in diamond synthesis through laser resonant vibrational excitation of precursor molecules

    PubMed Central

    Xie, Zhi Qiang; Bai, Jaeil; Zhou, Yun Shen; Gao, Yi; Park, Jongbok; Guillemet, Thomas; Jiang, Lan; Zeng, Xiao Cheng; Lu, Yong Feng

    2014-01-01

    Crystallographic orientations determine the optical, electrical, mechanical, and thermal properties of crystals. Control of crystallographic orientations has been studied by changing the growth parameters, including temperature, pressure, proportion of precursors, and surface conditions. However, molecular dynamic mechanisms underlying these controls remain largely unknown. Here we achieved control of crystallographic orientations in diamond growth through a joint experimental and theoretical study of laser resonant vibrational excitation of precursor molecules (ethylene). Resonant vibrational excitation of the ethylene molecules using a wavelength-tunable CO2 laser steers the chemical reactions and promotes proportion of intermediate oxide species, which results in preferential growth of {100}-oriented diamond films and diamond single crystals in open air. Quantum molecular dynamic simulations and calculations of chemisorption energies of radicals detected from our mass-spectroscopy experiment provide an in-depth understanding of molecular reaction mechanisms in the steering of chemical reactions and control of crystallographic orientations. This finding opens up a new avenue for controlled chemical vapor deposition of crystals through resonant vibrational excitations to steer surface chemistry. PMID:24694918

  9. Quantum signature for laser-driven correlated excitation of Rydberg atoms

    NASA Astrophysics Data System (ADS)

    Wu, Huaizhi; Li, Yong; Yang, Zhen-Biao; Zheng, Shi-Biao

    2017-01-01

    The excitation dynamics of a laser-driven Rydberg-atom system exhibits a cooperative effect due to the interatomic Rydberg-Rydberg interaction, but the large many-body system with inhomogeneous Rydberg coupling is hard to exactly solve or numerically study by density-matrix equations. In this paper, we find that the laser-driven Rydberg-atom system with most of the atoms being in the ground state can be described by a simplified interaction model resembling the optical Kerr effect if the distance-dependent Rydberg-Rydberg interaction is replaced by an infinite-range coupling. We can then quantitatively study the effect of the quantum fluctuations on the Rydberg excitation with the interatomic correlation involved and analytically calculate the statistical characteristics of the excitation dynamics in the steady state, revealing the quantum signature of the driven-dissipative Rydberg-atom system. The results obtained here will be of great interest for other spin-1/2 systems with spin-spin coupling.

  10. Laser safety in design of near-infrared scanning LIDARs

    NASA Astrophysics Data System (ADS)

    Zhu, X.; Elgin, D.

    2015-05-01

    3D LIDARs (Light Detection and Ranging) with 1.5μm nanosecond pulse lasers have been increasingly used in different applications. The main reason for their popularity is that these LIDARs have high performance while at the same time can be made eye-safe. Because the laser hazard effect on eyes or skin at this wavelength region (<1.4μm) is mainly from the thermal effect accumulated from many individual pulses over a period of seconds, scanning can effectively reduce the laser beam hazard effect from the LIDARs. Neptec LIDARs have been used in docking to the International Space Station, military helicopter landing and industrial mining applications. We have incorporated the laser safety requirements in the LIDAR design and conducted laser safety analysis for different operational scenarios. While 1.5μm is normally said to be the eye-safe wavelength, in reality a high performance 3D LIDAR needs high pulse energy, small beam size and high pulse repetition frequency (PRF) to achieve long range, high resolution and high density images. The resulting radiant exposure of its stationary beam could be many times higher than the limit for a Class 1 laser device. Without carefully choosing laser and scanning parameters, including field-of-view, scan speed and pattern, a scanning LIDAR can't be eye- or skin-safe based only on its wavelength. This paper discusses the laser safety considerations in the design of eye-safe scanning LIDARs, including laser pulse energy, PRF, beam size and scanning parameters in two basic designs of scanning mechanisms, i.e. galvanometer based scanner and Risley prism based scanner. The laser safety is discussed in terms of device classification, nominal ocular hazard distance (NOHD) and safety glasses optical density (OD).

  11. Ultrafast imaging of free carriers: controlled excitation with chirped ultrafast laser Bessel beams

    NASA Astrophysics Data System (ADS)

    Velpula, P. K.; Bhuyan, M. K.; Mauclair, C.; Colombier, J. P.; Stoian, R.

    2014-03-01

    Nonlinear propagation of intense ultrafast laser pulses inside transparent materials has a strong influence on the fabrication quality and accuracy for 3D laser-material processing. Due to their ability to maintain near-constant fluence profiles over an appreciable distance along the propagation direction in linear and nonlinear media, ultrafast Bessel beams are ideal sources for high aspect ratio sub-micron structuring applications. We report here on the interaction of transparent materials, especially fused silica, with ultrafast non-diffractive beams of moderate cone angle at various laser energies and pulse durations and define their impact on photoinscription regimes, i.e. formation of isotropic and non-isotropic (positive and negative) refractive index structures. The laser pulse duration was observed to be key in deciding the type of the structures via excitation efficiency. To understand the significant mechanisms for forming these different structures, the free carrier behavior as a function of laser pulse duration and energy was studied by capturing instantaneous excitation profiles using time-resolved microscopy. Time-resolved imaging and simulation studies reveal that low carrier densities are generated for ultrashort pulses leading to soft positive index alterations via presumably non-thermally induced structural transitions via defects. On the other hand, the high free carrier density generation in the case of longer pulse durations leads to a hydrodynamic expansion resulting in high aspect ratio sub-micron size wide voids. Delayed ionization, carrier defocusing and lower nonlinear effects are responsible for the confinement of energy, resulting in efficient energy deposition on-axis.

  12. High power mid-infrared continuous-wave optical parametric oscillator pumped by fiber lasers

    NASA Astrophysics Data System (ADS)

    Xu, Xiaojun; Li, Xiao; Liu, Lei; Shang, Yaping

    2015-02-01

    3~5μm mid-infrared laser has many important applications, such as gas detection, spectral analysis, remote sensing, medical treatment, and also in the military laser radar, infrared countermine, and so on. Optical parametric oscillator (OPO) is an efficient way to generate laser in this wavelength range, which has attracted the eyes of many people. In this paper, the recent development of mid-infrared OPO is overviewed. Meanwhile, detailed introduction on our recent work is given. Maximum idler output power of 34.2W at center wavelength of 3.35μm was obtained, to our knowledge, which is the new power record of the international public reporting for the continue-wave (CW) mid-infrared OPO. It is worth mentioning that the pump source, the quasi single-frequency (SF) narrow line width fiber laser, was also developed by our groups. According to the current status of research, some solutions is proposed in order to achieve higher power, narrower line width, and compact volume mid-infrared OPO in a wide tunable range.

  13. CONTROL OF LASER RADIATION PARAMETERS: Excitation of dynamic chaos in a monolithic ring chip laser upon periodic modulation of mechanical stresses in the active element

    NASA Astrophysics Data System (ADS)

    Kravtsov, Nikolai V.; Sidorov, S. S.; Pashinin, Pavel P.; Firsov, V. V.; Chekina, S. N.

    2004-04-01

    The peculiarities of nonlinear dynamics of solid-state bidirectional ring Nd:YAG chip lasers are studied theoretically and experimentally during periodic modulation of mechanical stresses in the active element. It is shown that modulation of mechanical stresses is an effective method for exciting dynamic chaos in a monolithic chip laser.

  14. Infrared Imaging of {ital In Vivo} Microvasculature Following Pulsed Laser Irradiation

    SciTech Connect

    Telenkov, S.A.; Milner, T.E.; Smithies, D.J.; Nelson, J.S.; Goodman, D.M.; Tanenbaum, B.S.

    1998-10-01

    Infrared emission images of the chick chorioallantoic membrane (CAM) microvasculature following pulsed laser irradiation were recorded using a high speed infrared focal plane array camera. A three-dimensional tomographic reconstruction algorithm was applied to compute the initial space-dependent temperature increase in discrete CAM blood vessels caused by light absorption. The proposed method may provide consistent estimates of the physical dimensions of subsurface blood vessels and may be useful in understanding a variety of biomedical engineering problems involving laser{endash}tissue interaction. {copyright} {ital 1998 Society of Photo-Optical Instrumentation Engineers.}

  15. A fast moving object detection method based on 2D laser scanner and infrared camera

    NASA Astrophysics Data System (ADS)

    Zeng, Lina; Ding, Meng; Zhang, Tianci; Sun, Zejun

    2015-10-01

    Moving object detection is a major research direction of video surveillance systems. This paper proposes a novel approach for moving object detection by fusing information from the laser scanner and infrared camera. First, in accordance with the feature of laser scanner data, we apply robust principal component analysis (RPCA) to studying moving object detection. Then the depth and angle information of moving objects is mapped to the infrared image pixels so as to obtain the regions of interest (ROI). Finally, moving objects can be recognized by making investigation of the ROI. Experimental results show that this method has good real-time performance and accuracy.

  16. Laser radiation action on the biomedium as nonadiabatic excitation of macromolecules

    NASA Astrophysics Data System (ADS)

    Kompanets, Igor N.; Krasnov, Andrey E.; Malov, A. N.

    1996-11-01

    The extended sphere of the laser successful use at large vagueness of the gear of radiation interaction with biological and biosimilar objects is a main modern paradox in the application of low-intensity coherent radiation in biology and medicine. There are rather regularly, for example, the reasons of immateriality of such parameters as laser radiation coherency degree for biostimulation, but the replacement of semi-conductor lasers by the light diodes isn't observed in medical practice until now. there are also no convincing results on comparative analysis of biostimulated effect under coherent and noncoherent radiation. Action of coherent electromagnetic radiation of the visible and infrared spectral range causes, as appear, the same type structure-optical changes in various objects biological liquids, cells suspensions, model biomolecular solutions, cells of plan, insects and animals. The medicobiologic consequences of laser effect are extremely variable because of the complexity of biological object and sophistication of research techniques and analyses. The energy doze of radiation acting onto a bio-object, as a rule, is extremely small, and hence like the case of extremely high frequency radiation one can to name this action by the 'informative' one, i.e., initiating only biosystem reactions is produced due to its own energy. In connection with the relatively slow biosystem response to the laser radiation action, the nonlocality of this reaction at the local action and large variety of biochemical reactions caused with laser radiation one can assume the existence of uniform physical mechanism realizing the biostimulation effect of laser radiation for various biosystems.

  17. Studies of fullerene absorption and production using an infrared free-electron laser

    SciTech Connect

    Affatigato, M.; Haglund, R.F.; Ying, Z.C.; Compton, R.N.

    1995-12-31

    Tunable photon sources such as free-electron lasers are potentially valuable tools in spectroscopic studies of fullerenes, a new class of carbon materials with unique cage structures. We have used the infrared free-electron-laser facility at Vanderbilt University to study the infrared absorption of gas-phase fullerene molecules and also to investigate the effects of an infrared laser in the synthesis and crystallization of fullerene materials. In one experiment, fullerene vapor was created in a heat pipe through which the FEL beam was passed; the transmission of the FEL beam relative to a reference detector was measured as a function of wavelength. A large (>10%) absorption of the IR laser was observed when it passed through C{sub 60} vapor at {approximately}800{degrees}C. Due to the broad spectral width of the FEL as well as spectral congestion, no spectral peaks were seen when the laser wavelength was tuned across a T{sub 1u}C{sub 60} IR mode near 7.0 {mu}. However, it is expected that the vibrational features can be resolved experimentally by passing the transmitted beam through a monochromator. In a separate experiment, the FEL beam was focused onto a surface of graphite or graphite/metal mixture target. Various fullerene molecules, including endohedral types, were produced when the soot was recovered from the ablation chamber. The yield of the products was measured to be {approximately}0.4 g/J of the incident laser energy. However, both the yield and the product distribution are virtually, the same as those in experiments using a nanosecond Nd:YAG laser. This suggests that the laser wavelength is not a crucial parameter in making fullerenes by laser ablation. Even when the laser is at resonance with one of the vibrational modes of C{sub 60}, the fullerene production is neither substantially enhanced nor suppressed.

  18. IV INTERNATIONAL CONFERENCE ON ATOM AND MOLECULAR PULSED LASERS (AMPL'99): Radiative and photochemical properties of organic compounds excited by high-power XeCl laser radiation

    NASA Astrophysics Data System (ADS)

    Kopylova, T. N.; Kuznetsova, Rimma T.; Svetlichnyi, Valerii A.; Sergeev, A. K.; Tel'minov, E. N.; Filinov, D. N.

    2000-06-01

    Radiative and photochemical properties of a number of laser dyes excited by focused radiation of a XeCl laser with intensity up to 200 MW cm-2 were studied. A method for measuring the gain of organic molecules under high-power excitation is proposed. The dependence of the dye transmittance for the pump radiation on its intensity was studied. It is shown that changes in energy, spectral, and time characteristics of radiation and the photostability of compounds under high-power excitation are associated with the formation of superluminescence.

  19. Response measurement by laser Doppler vibrometry in vibration qualification tests with non-Gaussian random excitation

    NASA Astrophysics Data System (ADS)

    Troncossi, M.; Di Sante, R.; Rivola, A.

    2016-10-01

    In the field of vibration qualification testing, random excitations are typically imposed on the tested system in terms of a power spectral density (PSD) profile. This is the one of the most popular ways to control the shaker or slip table for durability tests. However, these excitations (and the corresponding system responses) exhibit a Gaussian probability distribution, whereas not all real-life excitations are Gaussian, causing the response to be also non-Gaussian. In order to introduce non-Gaussian peaks, a further parameter, i.e., kurtosis, has to be controlled in addition to the PSD. However, depending on the specimen behaviour and input signal characteristics, the use of non-Gaussian excitations with high kurtosis and a given PSD does not automatically imply a non-Gaussian stress response. For an experimental investigation of these coupled features, suitable measurement methods need to be developed in order to estimate the stress amplitude response at critical failure locations and consequently evaluate the input signals most representative for real-life, non-Gaussian excitations. In this paper, a simple test rig with a notched cantilevered specimen was developed to measure the response and examine the kurtosis values in the case of stationary Gaussian, stationary non-Gaussian, and burst non-Gaussian excitation signals. The laser Doppler vibrometry technique was used in this type of test for the first time, in order to estimate the specimen stress amplitude response as proportional to the differential displacement measured at the notch section ends. A method based on the use of measurements using accelerometers to correct for the occasional signal dropouts occurring during the experiment is described. The results demonstrate the ability of the test procedure to evaluate the output signal features and therefore to select the most appropriate input signal for the fatigue test.

  20. Response measurement by laser Doppler vibrometry in vibration qualification tests with non-Gaussian random excitation.

    PubMed

    Troncossi, M; Di Sante, R; Rivola, A

    2016-10-01

    In the field of vibration qualification testing, random excitations are typically imposed on the tested system in terms of a power spectral density (PSD) profile. This is the one of the most popular ways to control the shaker or slip table for durability tests. However, these excitations (and the corresponding system responses) exhibit a Gaussian probability distribution, whereas not all real-life excitations are Gaussian, causing the response to be also non-Gaussian. In order to introduce non-Gaussian peaks, a further parameter, i.e., kurtosis, has to be controlled in addition to the PSD. However, depending on the specimen behaviour and input signal characteristics, the use of non-Gaussian excitations with high kurtosis and a given PSD does not automatically imply a non-Gaussian stress response. For an experimental investigation of these coupled features, suitable measurement methods need to be developed in order to estimate the stress amplitude response at critical failure locations and consequently evaluate the input signals most representative for real-life, non-Gaussian excitations. In this paper, a simple test rig with a notched cantilevered specimen was developed to measure the response and examine the kurtosis values in the case of stationary Gaussian, stationary non-Gaussian, and burst non-Gaussian excitation signals. The laser Doppler vibrometry technique was used in this type of test for the first time, in order to estimate the specimen stress amplitude response as proportional to the differential displacement measured at the notch section ends. A method based on the use of measurements using accelerometers to correct for the occasional signal dropouts occurring during the experiment is described. The results demonstrate the ability of the test procedure to evaluate the output signal features and therefore to select the most appropriate input signal for the fatigue test.

  1. The possibilities of applying infrared lasers in otolaryngology

    NASA Astrophysics Data System (ADS)

    Kukwa, Andrzej; Tulibacki, Marek P.; Wojtowicz, Piotr; Oledzka, Iwona; Obarska, Agnieszka

    2003-10-01

    The authors present their many years of experience in the area of laryngological surgery with various types of solid lasers. In our clinical practice we use Nd-YAG, Ho-YAG and Er-YAG surgical lasers. There are many reasons for applying lasers, depending on medical conditions. One of the most frequent cases are the nasal polyps, where surgical treatment is aimed at curing the results. For this type the procedures there was applied Nd-YAG laser, which has shortened the period of treatment and extended the remission. We also use this laser for mucal tissue corrections of the nasal conchs through deep coagulation effect. The above mentioned laser is also useful for the preventative treatment of granulation stenosis by removal of granulation tissue from different sections of the upper way; from the nose to the trachea.Other laser procedures in the nasal area include coagulation of Kisselbach locus, bleeding in Rendu-Osler disease, separating adhesions of the nasal concha from the nasal septum, coagulation of septal bleeding polyps, angiomas of different location, small papillomae of throat and nose, and reduction of hypertrophy nasopharyngeal mucoosa in OSAS patients, and uvolo-palato-pharyngoplasty (UPPP). Neodymium laser is also used for the management of neoplastic diseases in palliative and radical (CA. basocellulare) treatment for the resection of the premalignant changes (papilloma, leukoplakia) and early neoplastic changes of throat and larynx. Keloplasty in the area of larynx and trachea is performed with the use of Ho-YAG laser, with shallow effect, regardless of the density of tissue, enabling coagulation of vascular vessels. It enables non-traumatic resections of bone structures, such as the wall of maxillary sinus, nasal spine, or conchoplasty; the mucal tissue and the frame. Recent clinical tests are examining the possibilities of Er-YAG laser application for crushing calculus in the salivary ducts. Using lasers in laryngology enables their extensive

  2. Matrix-assisted laser-desorption mass spectrometry of DNA using an infrared free-electron laser

    NASA Astrophysics Data System (ADS)

    Haglund, Richard F., Jr.; Tang, Kai; Hillenkamp, Franz; Chen, C. H. Winston

    1993-07-01

    Sequencing the human genome requires an interdisciplinary approach combining aspects of biology, chemistry, physics, and engineering applied at the molecular level. One potentially interesting approach involves the use of matrix-assisted laser desorption-ionization mass spectroscopy (MALDI-MS), because of its high sensitivity, high speed, great accuracy, and ease of automation. However, while MALDI-MS has been successful in mass analysis of proteins and many large biomolecules, attempts to apply the technique to DNA sequencing have proven notoriously difficult. Because the choice of matrix materials for MALDI-MS is severely constrained by the application of conventional UV and visible laser sources, we are investigating the application of a tunable infrared free-electron laser to test the potential of infrared MALDI-MS for DNA sequencing. We describe the advantages of using tunable IR laser sources to choose matrix materials with optimal desorption, ionization, and thermomechanical properties, while avoiding the photochemical effects induced by ultraviolet and visible lasers. We also show the results of preliminary MALDI-MS experiments on small organic molecules using the Vanderbilt free-electron laser.

  3. Development of far infrared attenuation to measure electron densities in cw pin discharge lasers

    NASA Technical Reports Server (NTRS)

    Babcock, R. V.

    1977-01-01

    A two beam attenuation technique was devised to measure electron densities 10 to the 9th power to 10 to the 11th power cm/3 resolved to 1 cm, in a near atmospheric COFFEE laser discharge, using 496 micrometer and 1,220 micrometer radiations from CH3F, optically pumped by a CO2 laser. A far infrared generator was developed which was suitable except for a periodic intensity variation in FIR output deriving from frequency variation of the pump radiation.

  4. Applications of infrared free electron lasers in picosecond and nonlinear spectroscopy

    NASA Astrophysics Data System (ADS)

    Fann, W. S.; Benson, S. V.; Madey, J. M. J.; Etemad, S.; Baker, G. L.; Rothberg, L.; Roberson, M.; Austin, R. H.

    1990-10-01

    In this paper we describe two different types of spectroscopic experiments that exploit the characteristics of the infrared FEL, Mark III, for studies of condensed matter: - the spectrum of χ(3)(-3ω; ω, ω, ω) in polyacetylene: an application of the free electron laser in nonlinear optical spectroscopy, and - a dynamical test of Davydov-like solitons in acetanilide using a picosecond free electron laser. These two studies highlight the unique contributions FELs can make to condensed-matter spectroscopy.

  5. The effect of near-infrared MLS laser radiation on cell membrane structure and radical generation.

    PubMed

    Kujawa, Jolanta; Pasternak, Kamila; Zavodnik, Ilya; Irzmański, Robert; Wróbel, Dominika; Bryszewska, Maria

    2014-09-01

    The therapeutic effects of low-power laser radiation of different wavelengths and light doses are well known, but the biochemical mechanism of the interaction of laser light with living cells is not fully understood. We have investigated the effect of MLS (Multiwave Locked System) laser near-infrared irradiation on cell membrane structure, functional properties, and free radical generation using human red blood cells and breast cancer MCF-4 cells. The cells were irradiated with low-intensity MLS near-infrared (simultaneously 808 nm, continuous emission and 905 nm, pulse emission, pulse-wave frequency, 1,000 or 2,000 Hz) laser light at light doses from 0 to 15 J (average power density 212.5 mW/cm(2), spot size was 3.18 cm(2)) at 22 °C, the activity membrane bound acetylcholinesterase, cell stability, anti-oxidative activity, and free radical generation were the parameters used in characterizing the structural and functional changes of the cell. Near-infrared low-intensity laser radiation changed the acetylcholinesterase activity of the red blood cell membrane in a dose-dependent manner: There was a considerable increase of maximal enzymatic rate and Michaelis constant due to changes in the membrane structure. Integral parameters such as erythrocyte stability, membrane lipid peroxidation, or methemoglobin levels remained unchanged. Anti-oxidative capacity of the red blood cells increased after MLS laser irradiation. This irradiation induced a time-dependent increase in free radical generation in MCF-4 cells. Low-intensity near-infrared MLS laser radiation induces free radical generation and changes enzymatic and anti-oxidative activities of cellular components. Free radical generation may be the mechanism of the biomodulative effect of laser radiation.

  6. Infrared absorption nano-spectroscopy using sample photoexpansion induced by tunable quantum cascade lasers.

    PubMed

    Lu, Feng; Belkin, Mikhail A

    2011-10-10

    We report a simple technique that allows obtaining mid-infrared absorption spectra with nanoscale spatial resolution under low-power illumination from tunable quantum cascade lasers. Light absorption is detected by measuring associated sample thermal expansion with an atomic force microscope. To detect minute thermal expansion we tune the repetition frequency of laser pulses in resonance with the mechanical frequency of the atomic force microscope cantilever. Spatial resolution of better than 50 nm is experimentally demonstrated.

  7. Low-intensity infrared laser effects on zymosan-induced articular inflammatory response

    NASA Astrophysics Data System (ADS)

    Januária dos Anjos, Lúcia Mara; da Fonseca, Adenilson d. S.; Gameiro, Jacy; de Paoli, Flávia

    2015-03-01

    Low-level therapy laser is a phototherapy treatment that involves the application of low power light in the red or infrared wavelengths in various diseases such as arthritis. In this work, we investigated whether low-intensity infrared laser therapy could cause death by caspase-6 apoptosis or DNA damage pathways in cartilage cells after zymosaninduced articular inflammatory process. Inflammatory process was induced in C57BL/6 mouse by intra-articular injection of zymosan into rear tibio-tarsal joints. Thirty animals were divided in five groups: (I) control, (II) laser, (III) zymosan-induced, (IV) zymosan-induced + laser and (V). Laser exposure was performed after zymosan administration with low-intensity infrared laser (830 nm), power 10 mW, fluence 3.0 J/cm2 at continuous mode emission, in five doses. Twenty-four hours after last irradiation, the animals were sacrificed and the right joints fixed and demineralized. Morphological analysis was observed by hematoxylin and eosin stain, pro-apoptotic (caspase-6) was analyzed by immunocytochemistry and DNA fragmentation was performed by TUNEL assay in articular cartilage cells. Inflammatory process was observed in connective tissue near to articular cartilage, in IV and V groups, indicating zymosan effect. This process was decreased in both groups after laser treatment and dexamethasone. Although groups III and IV presented higher caspase-6 and DNA fragmentation percentages, statistical differences were not observed when compared to groups I and II. Our results suggest that therapies based on low-intensity infrared lasers could reduce inflammatory process and could not cause death by caspase-6 apoptosis or DNA damage pathways in cartilage cells after zymosan-induced articular inflammatory process.

  8. Growth and characterization of materials for tunable lasers in the near infrared spectral region

    NASA Technical Reports Server (NTRS)

    Powell, Richard C.; Martin, Joel J.

    1989-01-01

    Laser spectroscopy, crystal growth, and radiation damage research was performed. The laser spectroscopy effort focused on understanding the effects of excited state absorption processes involving pump photons. This was performed on a variety of rare earth ions in different hosts. The crystal growth and radiation damage effort focused on LiFY4 (YLF) doped with rare earth ions. The results of this work is described.

  9. Spectroscopy of the three-photon laser excitation of cold Rubidium Rydberg atoms in a magneto-optical trap

    SciTech Connect

    Entin, V. M.; Yakshina, E. A.; Tretyakov, D. B.; Beterov, I. I.; Ryabtsev, I. I.

    2013-05-15

    The spectra of the three-photon laser excitation 5S{sub 1/2} {yields} 5P{sub 3/2} {yields} 6S{sub 1/2}nP of cold Rb Rydberg atoms in an operating magneto-optical trap based on continuous single-frequency lasers at each stage are studied. These spectra contain two partly overlapping peaks of different amplitudes, which correspond to coherent three-photon excitation and incoherent three-step excitation due to the presence of two different ways of excitation through the dressed states of intermediate levels. A four-level theoretical model based on optical Bloch equations is developed to analyze these spectra. Good agreement between the experimental and calculated data is achieved by introducing additional decay of optical coherence induced by a finite laser line width and other broadening sources (stray electromagnetic fields, residual Doppler broadening, interatomic interactions) into the model.

  10. One-photon excitation in the e -H collision in the presence of a laser field

    SciTech Connect

    Cionga, A. ); Florescu, V. )

    1992-04-01

    We consider the one-photon excitation of atomic hydrogen by electron impact in the presence of a homogeneous monochromatic linearly polarized electric field as a model for the radiation field of the laser. In the framework of the approximative approach of Faisal and Rahman (in {ital Fifth} {ital International} {ital Conference} {ital on} {ital Atomic} {ital Physics}, edited by R. Marrus, M. H. Prior, and H. A. Stutgart (University of California, Berkeley, 1976), p. 49), suited for high-energy electrons, we present an analytic expression for the transition amplitude to an arbitrary {ital nlm} state, in terms of hypergeometric Gauss and Appell {ital F}{sub 1} functions, together with the numerical results for excitation to the {ital n}=4 states.

  11. Picosecond x-ray strain rosette reveals direct laser excitation of coherent transverse acoustic phonons

    PubMed Central

    Lee, Sooheyong; Williams, G. Jackson; Campana, Maria I.; Walko, Donald A.; Landahl, Eric C.

    2016-01-01

    Using a strain-rosette, we demonstrate the existence of transverse strain using time-resolved x-ray diffraction from multiple Bragg reflections in laser-excited bulk gallium arsenide. We find that anisotropic strain is responsible for a considerable fraction of the total lattice motion at early times before thermal equilibrium is achieved. Our measurements are described by a new model where the Poisson ratio drives transverse motion, resulting in the creation of shear waves without the need for an indirect process such as mode conversion at an interface. Using the same excitation geometry with the narrow-gap semiconductor indium antimonide, we detected coherent transverse acoustic oscillations at frequencies of several GHz. PMID:26751616

  12. Time-resolved thermal mirror technique with top-hat cw laser excitation.

    PubMed

    Astrath, Francine B; Astrath, Nelson G; Shen, Jun; Zhou, Jianqin; Malacarne, Luis C; Pedreira, P R B; Baesso, Mauro L

    2008-08-04

    A theoretical model was developed for time-resolved thermal mirror spectroscopy under top-hat cw laser excitation that induced a nanoscale surface displacement of a low absorption sample. An additional phase shift to the electrical field of a TEM(00) probe beam reflected from the surface displacement was derived, and Fresnel diffraction theory was used to calculate the propagation of the probe beam. With the theory, optical and thermal properties of three glasses were measured, and found to be consistent with literature values. With a top-hat excitation, an experimental apparatus was developed for either a single thermal mirror or a single thermal lens measurement. Furthermore, the apparatus was used for concurrent measurements of thermal mirror and thermal lens. More physical properties could be measured using the concurrent measurements.

  13. Picosecond x-ray strain rosette reveals direct laser excitation of coherent transverse acoustic phonons

    SciTech Connect

    Lee, Sooheyong; Williams, G. Jackson; Campana, Maria I.; Walko, Donald A.; Landahl, Eric C.

    2016-01-11

    Using a strain-rosette, we demonstrate the existence of transverse strain using time-resolved x-ray diffraction from multiple Bragg reflections in laser-excited bulk gallium arsenide. We find that anisotropic strain is responsible for a considerable fraction of the total lattice motion at early times before thermal equilibrium is achieved. Our measurements are described by a new model where the Poisson ratio drives transverse motion, resulting in the creation of shear waves without the need for an indirect process such as mode conversion at an interface. Finally, using the same excitation geometry with the narrow-gap semiconductor indium antimonide, we detected coherent transverse acoustic oscillations at frequencies of several GHz.

  14. Picosecond x-ray strain rosette reveals direct laser excitation of coherent transverse acoustic phonons

    DOE PAGES

    Lee, Sooheyong; Williams, G. Jackson; Campana, Maria I.; ...

    2016-01-11

    Using a strain-rosette, we demonstrate the existence of transverse strain using time-resolved x-ray diffraction from multiple Bragg reflections in laser-excited bulk gallium arsenide. We find that anisotropic strain is responsible for a considerable fraction of the total lattice motion at early times before thermal equilibrium is achieved. Our measurements are described by a new model where the Poisson ratio drives transverse motion, resulting in the creation of shear waves without the need for an indirect process such as mode conversion at an interface. Finally, using the same excitation geometry with the narrow-gap semiconductor indium antimonide, we detected coherent transverse acousticmore » oscillations at frequencies of several GHz.« less

  15. Food powder analysis by using transversely excited atmospheric CO2 laser-induced plasma spectroscopy

    NASA Astrophysics Data System (ADS)

    Khumaeni, Ali; Sukra Lie, Zener; Setiabudi, Wahyu; Hendrik Kurniawan, Koo; Kagawa, Kiichiro

    2015-06-01

    A direct and sensitive analysis of food powder sample has successfully been carried out by utilizing the special characteristics of pulsed transversely excited atmospheric (TEA) CO2 laser. In this study, a food powder was placed in a container made of copper plate and covered by a metal mesh. The container was perpendicularly attached on a metal surface. A high-temperature luminous plasma was induced on a metal surface 5 mm above the mesh. Once the plasma was produced, a strong shock wave was induced, blowing-off of the powder from the container to enter into the plasma to be dissociated and excited. By using this method, a semi-quantitative analysis of food powder was made. The detection limits of Cr in the powdered agar and Cd in the powdered rice were 9 mg/kg and 50 mg/kg, respectively.

  16. Features of simultaneous ground- and excited-state lasing in quantum dot lasers

    SciTech Connect

    Zhukov, A. E. Maximov, M. V.; Shernyakov, Yu. M.; Livshits, D. A.; Savelyev, A. V.; Zubov, F. I.; Klimenko, V. V.

    2012-02-15

    The lasing spectra and light-current (L-I) characteristics of an InAs/InGaAs quantum dot laser emitting in the simultaneous lasing mode at the ground- and excited-state optical transitions are studied. Lasing and spontaneous emission spectra are compared. It is shown that ground-state quenching of lasing is observed even in the absence of active region self-heating or an increase in homogeneous broadening with growth in the current density. It is found that the intensities of both lasing and spontaneous emission at the ground-state transition begin to decrease at a pump intensity that significantly exceeds the two-level lasing threshold. It is also found that different groups of quantum dots are involved in ground- and excited-state lasing.

  17. Photo-magnonics: excitation of magnonic materials by femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Muenzenberg, Markus

    2010-03-01

    Analogue the photonic crystals, a periodic modification of a magnetic material is prepared by forming an anti-dot lattice for spin waves. The resulting bands are generally complex in the magnetic case because of different dispersions along different magnetization directions (backward volume and Damon-Eshbach mode). They depend on the variation strength of the periodic magnetostatic potential. All-optical femtosecond laser experiments allow the excitation of spin-waves with comparable amplitudes as field pulse and resonance techniques today. It is a promising valuable alternative method to study spin-waves and their relaxation paths in a magnonic material. Laser pulses with a duration of 60 fs from a Ti:Sapphire regenerative laser system are used for optical excitation (pump pulse) as well as for the observation of the subsequent magnetic relaxation (probe pulse). The initial local single spin-flip excitation is subsequently decaying into spin waves lower in energy within the pico- and nanosecond regime over a wide spectral range. In focus of our investigation is the propagation and localization of dipolar surface modes (Damon-Eshbach) in thin Nickel and (low damped) CoFeB film cubic and hexagonal lattice structures. Their mode dispersion is measured by applying different magnetic fields which shift the energy of the mode and allows identifying them. We find well defined modes in the condensed state with a specific pronounced k-value determining the properties of the propagating spin wave. One example for a distinct modification of the magnonic periodic structure is a line defect that can function as a wave guide inside the magnonic gap region. An increased intensity of the Damon Eshbach mode by a factor of two is found in the wave guide region. A study of these wave guides will allow to specifically design the material properties, making magnonic materials the material of choice for advanced spin computing devices.

  18. Photobiomodulation of wound healing via visible and infrared laser irradiation.

    PubMed

    Solmaz, Hakan; Ulgen, Yekta; Gulsoy, Murat

    2017-03-20

    Fibroblast cells are known to be one of the key elements in wound healing process, which has been under the scope of research for decades. However, the exact mechanism of photobiomodulation on wound healing is not fully understood yet. Photobiomodulation of 635 and 809 nm laser irradiation at two different energy densities were investigated with two independent experiments; first, in vitro cell proliferation and then in vivo wound healing. L929 mouse fibroblast cell suspensions were exposed with 635 and 809 nm laser irradiations of 1 and 3 J/cm(2) energy densities at 50 mW output power separately for the investigation of photobiomodulation in vitro. Viabilities of cells were examined by means of MTT assays performed at the 24th, 48th, and 72nd hours following the laser irradiations. Following the in vitro experiments, 1 cm long cutaneous incisional skin wounds on Wistar albino rats (n = 24) were exposed with the same laser sources and doses in vivo. Wound samples were examined on 3rd, 5th, and 7th days of healing by means of mechanical tensile strength tests and histological examinations. MTT assay results showed that 635 nm laser irradiation of both energy densities after 24 h were found to be proliferative. One joule per square centimeter laser irradiation results also had positive effect on cell proliferation after 72 h. However, 809 nm laser irradiation at both energy densities had neither positive nor negative affects on cell viability. In vivo experiment results showed that, 635 nm laser irradiation of both energy densities stimulated wound healing in terms of tensile strength, whereas 809 nm laser stimulation did not cause any stimulative effect. The results of mechanical tests were compatible with the histological evaluations. In this study, it is observed that 635 nm laser irradiations of low energy densities had stimulative effects in terms of cell proliferation in vitro and mechanical strength of incisions in vivo. However, 809 nm laser

  19. The excitation of near-infrared H2 emission in NGC 253

    NASA Astrophysics Data System (ADS)

    Rosenberg, M. J. F.; van der Werf, P. P.; Israel, F. P.

    2013-02-01

    Context. Because of its large angular size and proximity to the Milky Way, NGC 253, an archetypal starburst galaxy, provides an excellent laboratory to study the intricacies of this intense episode of star formation. Aims: We aim to characterize the excitation mechanisms driving the emission in NGC 253. Specifically we aim to distinguish between shock excitation and ultraviolet (UV) excitation as the dominant driving mechanism, using Brγ, H2 and [FeII] as diagnostic emission line tracers. Methods: Using SINFONI observations, we create linemaps of Brγ, [FeII]1.64, and all detected H2 transitions. By using symmetry arguments of the gas and stellar gas velocity field, we find a kinematic center in agreement with previous determinations. The ratio of the 2-1 S(1) to 1-0 S(1) H2 transitions can be used as a diagnostic to discriminate between shock and fluorescent excitation. Results: Using the 1-0 S(1)/2-1 S(1) line ratio as well as several other H2 line ratios and the morphological comparison between H2 and Brγ and [FeII], we find that excitation from UV photons is the dominant excitation mechanisms throughout NGC 253. We employ a diagnostic energy level diagram to quantitatively differentiate between mechanisms. We compare the observed energy level diagrams to photon-dominated region (PDR) and shock models and find that in most regions and over the galaxy as a whole, fluorescent excitation is the dominant mechanism exciting the H2 gas. We also place an upper limit of the percentage of shock excited H2 at 29%. Conclusions: We find that UV radiation is the dominant excitation mechanism for the H2 emission. The H2 emission does not correlate well with Brγ but closely traces the polycyclic aromatic hydrocarbon emission, showing that not only is H2 fluorescently excited, but it is predominately excited by slightly lower mass stars than O stars which excite Brγ, such as B stars. Reduced datacubes and extracted images for each line are only available at the CDS via

  20. Spin-wave population in nickel after femtosecond laser pulse excitation

    NASA Astrophysics Data System (ADS)

    Lenk, Benjamin; Eilers, Gerrit; Hamrle, Jaroslav; Münzenberg, Markus

    2010-10-01

    The spin-wave relaxation mechanisms after intense laser excitation in ferromagnetic nickel films are investigated with all-optical pump-probe experiments. Uniform precession (Kittel mode), Damon-Eshbach surface modes and perpendicular standing spin waves can be identified by their dispersion ω(Hext) . However, different to other ferromagnets ω(Hext) deviates from the expected behavior. Namely, a mode discontinuity is observed that can be attributed to a nonlinear process. Above a critical field the power spectrum reveals a redistribution of the energy within the spin-wave spectrum populated.

  1. Ultrafast lattice dynamics in lead selenide quantum dot induced by laser excitation

    SciTech Connect

    Wang, Xuan; Rahmani, Hamidreza; Zhou, Jun; Gorfien, Matthew; Mendez Plaskus, Joshua; Li, Dong; Voss, Ryan; Nelson, Cory A.; Wai Lei, Kin; Wolcott, Abraham; Zhu, Xiaoyang; Li, Junjie; Cao, Jianming

    2016-10-10

    We directly monitored the lattice dynamics in PbSe quantum dots induced by laser excitation using ultrafast electron di raction. The energy relaxation between the carriers and the lattice took place within 10 ps, showing no evidence of any signi cant phonon bottleneck e ect. Meanwhile, the lattice dilation exhibited some unusual features that could not be explained by the available mechanisms of photon- induced acoustic vibrations in semiconductors alone. The heat transport between the QDs and the substrate deviates signi cantly from Fourier's Law, which opens questions about the heat transfer under nonequilibrium conditions in nanoscale materials.

  2. Observation of negative terahertz photoconductivity in monolayer MoS2 under femtosecond laser excitation

    NASA Astrophysics Data System (ADS)

    Lui, Chun Hung; Frenzel, Alex J.; Pilon, Daniel V.; Lee, Yi-Hsien; Kong, Jing; Gedik, Nuh

    2014-03-01

    We observed a pronounced transient decrease of terahertz conductivity in doped monolayer molybdenum disulfide (MoS2) after pulsed laser excitation. This anomalous phenomenon arises from the strong many-body interactions in the system, where optically produced electron-hole pairs join the doped charges to form trions, bound states of two electrons and one hole, and substantially diminish the carrier conductivity by the resulting increase of effective mass. Our results reveal the ultrafast formation and decay of trions in monolayer MoS2 and their influence on the conductivity of the material.

  3. Ultrafast lattice dynamics in lead selenide quantum dot induced by laser excitation

    NASA Astrophysics Data System (ADS)

    Wang, Xuan; Rahmani, Hamidreza; Zhou, Jun; Gorfien, Matthew; Mendez Plaskus, Joshua; Li, Dong; Voss, Ryan; Nelson, Cory A.; Wai Lei, Kin; Wolcott, Abraham; Zhu, Xiaoyang; Li, Junjie; Cao, Jianming

    2016-10-01

    We directly monitored the lattice dynamics in PbSe quantum dots (QD) induced by laser excitation using ultrafast electron diffraction. The energy relaxation between the carriers and the lattice took place within 10 ps, showing no evidence of any significant phonon bottleneck effect. Meanwhile, the lattice dilation exhibited some unusual features that could not be explained by the available mechanisms of photon-induced acoustic vibrations in semiconductors alone. The heat transport between the QDs and the substrate deviates significantly from Fourier's Law, which opens questions about the heat transfer under nonequilibrium conditions in nanoscale materials.

  4. Bound state - excitation in ion-ion collisions related to X-ray lasers modelling

    SciTech Connect

    Stancalie, V.; Sureau, A.; Klisnick, A.

    1995-12-31

    As in the earlier work of Walling and Weisheit we used the Seaton`s semi-classical, impact parameter formulation of Coulomb excitation for a variety of inelastic ion-ion collisions, involved in laser-produced soft X-ray lasers with Li-like aluminum ions, 1s{sup 2} nl configuration. Energy levels has been calculated by direct SCF method including the spin-orbit interaction. Our definition of the electric 2{sup {lambda}} - pole line strength, S{sup {lambda}}, is consistent with that of Sobelman. The ion-ion collision processes have been considered for a wide range of temperature between 500 eV to 30 eV, with a particular interest in the last part of plasma evolution time, when complications such as non-Maxwellian particle distributions, radiation fields and transient plasma conditions can be neglected, and when the plasma electrons and ions have comparable temperatures.

  5. Spectroscopic analysis of the excitation transfer from background air to diffusing aluminum laser produced plasma

    NASA Astrophysics Data System (ADS)

    Ribière, M.; Karabourniotis, D.; Chéron, B. G.

    2009-04-01

    During the relaxation of the plasma plume generated by laser ablation of an aluminum target, a pronounced intensity enhancement is observed at the central wavelength of the 396.15 nm self-reversed resonant line. This spectral special feature is analyzed and related to the interaction of the plasma edge with the background air excited by the shockwave, prompt electrons, and extreme ultraviolet radiation produced at the earliest times of the ablation. In this article, the electron density, the aluminum ground state, and resonant level populations are determined from the fitting of the 396.15 nm calculated line profile to the experimental one at two background pressures (100 and 1000 Pa). The evolution of these densities is derived from experiments performed at delays, after the laser pulse arrival, ranging from 120 to 180 ns.

  6. Optimization of native fluorescence detection of proteins using a pulsed nano laser excitation source

    PubMed Central

    Heywood, Matthew S.; Farnsworth, Paul B.

    2010-01-01

    We present a mathematical description of the S/N ratio in a fluorescence-based protein detector for capillary electrophoresis that uses a pulsed UV laser at 266 nm as an excitation source. The model accounts for photobleaching, detector volume, laser repetition rate, and analyte flow rate. We have experimentally characterized such a system, and present a comparison of the experimental data with the predictions of the model. Using the model, the system was optimized for test analytes tryptophan, tyrosine, BSA, and conalbumin, producing detection limits (3σ) of 0.67 nM, 5.7 nM, 0.9 nM, and 1.5 nM, respectively. Based on the photobleaching data, a photobleaching cross section of 1.4×10−18 cm2 at 266 nm was calculated for tryptophan. PMID:21073798

  7. Runaway electron beams in the gas discharge for UV nitrogen laser excitation

    SciTech Connect

    Khomich, V. Yu.; Yamschikov, V. A.

    2011-12-15

    The review of the methods for obtaining the runaway electron beams in the gas discharge is performed. The new method is offered, using which the beam is first formed in a narrow gap ({approx}1 mm) between the cathode and the grid and then it is accelerated by the field of the plasma column of the anomalous self-sustained discharge in the main gap (10-20 mm long). The electron beams with an energy of about 10 keV and current density of 10{sup 3} A/cm{sup 2} at a molecular nitrogen pressure of up to 100 Torr have been obtained experimentally. The results of research of the UV nitrogen laser with an excitation via runaway electron beam and radiation of energy of {approx}1 mJ are given. The UV nitrogen laser generation with the energy of {approx}1 mJ has been obtained by the runaway electron beams.

  8. Temperature measurements using YAG : Dy and YAG : Sm under diode laser excitation (405 nm)

    NASA Astrophysics Data System (ADS)

    Hashemi, A.; Vetter, A.; Jovicic, G.; Batentschuk, M.; Brabec, C. J.

    2015-07-01

    Temperature-sensitive phosphors offer an option of accurate contactless temperature measurement. The method can be applied to a wide temperature range and up to more than 1500 K. In the current paper, phosphor thermometry based on four rare earths doped in YAG was studied. The standard excitation of thermographic phosphors is carried out with a Nd : YAG laser often at 355 or 266 nm. We examined the temperature dependent luminescence at an excitation wavelength of 405 nm. The excitation with visible blue light offers two main advantages: the excitation sources are rather cheap and they involve less safety issues. Accordingly, a variety of new application of such remote-thermometry would be possible. The results show that YAG : Dy and YAG : Sm may be well utilized for phosphor thermometry excited by a 405 nm diode laser.

  9. Two-color interference effect involving three-photon atomic excitation and four-wave mixing in crossed laser beams

    SciTech Connect

    Peet, V.

    2007-09-15

    Through multiphoton ionization measurements, the polarization effects in destructive quantum interference under three-photon resonant excitation have been studied. Recent observations [V. Peet, Phys. Rev. A 74, 033406 (2006)] have indicated that contrary to the well-known pattern of a total suppression of resonance excitation, the destructive interference becomes incomplete if three-photon transition is driven by crossed beams with orthogonal polarization planes. These observations have been tested for a more general case of two-color excitation and very similar polarization-dependent anomalies in the interference character have been registered. It has been shown that the destructive interference is modified and the resonance excitation does occur if two crossed laser beams have opposite circular polarizations. The pressure-induced evolution of the uncanceled ionization peaks has the ratio of blue shift to width close to 0.5 exactly as it is known for resonance ionization peaks registered under excitation by counterpropagating laser beams.

  10. Fluence-dependent dynamics of the 5d6s exchange splitting in Gd metal after femtosecond laser excitation

    NASA Astrophysics Data System (ADS)

    Frietsch, Björn; Carley, Robert; Gleich, Markus; Teichmann, Martin; Bowlan, John; Weinelt, Martin

    2016-07-01

    We investigate the fluence-dependent dynamics of the exchange-split 5d6s valence bands of Gd metal after femtosecond, near-infrared (IR) laser excitation. Time- and angle-resolved photoelectron spectroscopy (tr-ARPES) with extreme ultraviolet (XUV) probe pulses is used to simultaneously map the transient binding energies of the minority and majority spin valence bands. The decay constant of the exchange splitting increases with fluence. This reflects the slower response of the occupied majority-spin component, which we attribute to Elliot-Yafet spin-flip scattering in accordance with the microscopic three-temperature model (M3TM). In contrast, the time constant of the partly unoccupied minority-spin band stays unaffected by a change in pump fluence. Here, we introduce as an alternative to superdiffusive spin transport exchange scattering, which is an ultrafast electronic mechanism explaining the observed dynamics. Exchange scattering can reduce the spin polarization in the partially unoccupied minority-spin band and thus its energetic position without effective demagnetization.

  11. Two-photon excited spectroscopies of ex vivo human skin endogenous species irradiated by femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Chen, Jianxin; Zhuo, Shuangmu; Luo, Tianshu; Zhao, Jingjun

    2006-10-01

    Two-photon excited spectroscopies from ex vivo human skin are investigated by using a femtosecond laser and a confocal microscope (Zeiss LSM 510 META). In the dermis, collagen is responsible for second harmonic generation (SHG); elastin, nicotinamide adenine dinucleotide (NADH), melanin and porphyrin are the primary endogenous sources of two-photon excited autofluorescence. In the epidermis, keratin, NADH, melanin and porphyrins contribute to autofluorescence signals. The results also show that the SHG spectra have the ability to shift with the excitation wavelength and the autofluorescence spectra display a red shift of the spectral peaks when increasing the excitation wavelength. These results may have practical implications for diagnosis of skin diseases.

  12. Study on the activation of styrene-based shape memory polymer by medium-infrared laser light

    NASA Astrophysics Data System (ADS)

    Leng, Jinsong; Zhang, Dawei; Liu, Yanju; Yu, Kai; Lan, Xin

    2010-03-01

    This paper demonstrates the feasibility of shape memory polymer (SMP) activation by medium-infrared laser light. Medium-infrared light is transmitted by an optical fiber embedded in the SMP matrix, and the shape recovery process and temperature distribution are recorded by an infrared camera. Light-induced SMP exhibits potential applications in biomedicines and flexible displays.

  13. Photothermal analysis of polymeric dye laser materials excited at different pump rates

    NASA Astrophysics Data System (ADS)

    Duchowic, Ricardo; Scaffardi, Lucía B.; Costela, Angel; García-Moreno, Inmaculada; Sastre, Roberto; Acun~A, Alberto Ulises

    2003-02-01

    The photothermal properties and heat diffusion of polymeric lasers, made up from solutions of Rhodamine 6G in solid matrices of poly(2-hydroxyethyl methacrylate) with different amounts of the cross-linking monomer ethylene glycol dimethacrylate and copolymers of 2-hydroxyethyl methacrylate and methyl methacrylate have been studied through photothermal deflection spectroscopy. The heat load that is due to the pumping process was quantified as a function of the pump excitation repetition frequency (0.25-10 Hz), determining the time-dependent temperature changes at different locations within the laser matrix. A theoretical model, which reproduces these changes with high accuracy, was developed on the basis of the heat-diffusion equation of optically dense fluids. The observed thermal effects became important for impairing the laser stability at pump repetition frequencies higher than 1 Hz. In addition, the irreversible optical changes produced in the laser matrices at high pump fluence values (>1 J/cm2) were also analyzed. These effects originate, most likely, from a two-step photothermal mechanism.

  14. Comparison between accelerometer and laser vibrometer to measure traffic-excited vibrations on bridges

    NASA Astrophysics Data System (ADS)

    Gioffre, M.; Gusella, V.; Marsili, Roberto; Rossi, Gianluca L.

    2000-05-01

    The use of accelerometer based measurement techniques for evaluating bridge forced vibrations or to perform bridge modal analysis is well established. Some of the goals of this experimental approach and typical results are here reviewed. It is well known to all researchers who have experience in vibration measurements that values of acceleration amplitude can be very low at low frequencies and that a limitation to the use of accelerometer can be due to the threshold parameter of this kind of transducer. Under this condition the measurement of displacement seems more appropriate. On the other hand laser vibrometer systems detect relative displacements as opposed to the absolute measures of accelerometers. In this paper the results of some in field measurements on a highway little bridge, excited by traffic, under normal operating conditions, are analyzed. Vibrations have been measured simultaneously by a typical accelerometer for civil structures and by a laser vibrometer equipped with a fringe counter board in terms of velocity and displacements. The accelerations calculated from the laser vibrometer signals and the one directly measured by the accelerometer has been compared. The advantages of the use of a laser vibrometer at low frequency are relevant and it appears possible to open up new possibility to analyze bridge loads in operating conditions, monitoring bridge health state, predict fatigue life and improve the bridge design.

  15. Ultralow-power near-infrared excited neodymium-doped nanoparticles for long-term in vivo bioimaging.

    PubMed

    Qin, Qing-Song; Zhang, Pei-Zhi; Sun, Ling-Dong; Shi, Shuo; Chen, Nai-Xiu; Dong, Hao; Zheng, Xiao-Yu; Li, Le-Min; Yan, Chun-Hua

    2017-03-27

    Lanthanide-doped luminescent nanoparticles with both emission and excitation in the near-infrared (NIR-to-NIR) region hold great promise for bioimaging. Herein, core@shell structured LiLuF4:Nd@LiLuF4 (named as Nd@Lu) nanoparticles (NPs) with highly efficient NIR emission were developed for high-performance in vivo bioimaging. Strikingly, the absolute quantum yield of Nd@Lu NPs reached as high as 32%. After coating with polyethylene glycol (PEG), the water-dispersible Nd@Lu NPs showed good bio-compatibility and low toxicity. With efficient NIR emission, the Nd@Lu NPs were clearly detectable in tissues at depths of up to 20 mm. In addition, long-term in vivo biodistribution with a high signal-to-noise ratio of 25.1 was distinctly tracked upon an ultralow-power-density excitation (10 mW cm(-2)) of 732 nm for the first time.

  16. Multi-spectral imaging with mid-infrared semiconductor lasers

    NASA Astrophysics Data System (ADS)

    Wang, Yi; Wang, Yang; Le, Han Q.

    2006-01-01

    Multi-spectral laser imaging can be a useful technology for target discrimination, classification, and identification based on object spectral signatures. The mid-IR region (~3-14 μm) is particularly rich of molecular spectroscopic fingerprints, but the technology has been under utilized. Compact, potentially inexpensive semiconductor lasers may allow more cost-effective applications. This paper describes a development of semiconductor-laser-based multi-spectral imaging for both near-IR and mid-IR, and demonstrates the potential of this technology. The near-IR study employed 7 wavelengths from 0.635-1.55 μm, and used for system engineering evaluation as well as for studying the fundamental aspects of multi-spectral laser imaging. These include issues of wavelength-dependence scattering as a function of incident and receiving angle and the polarization effects. Stokes vector imaging and degree-of-linear-polarization were shown to reveal significant information to characterize the targets. The mid-IR study employed 4 wavelengths from 3.3-9.6 μm, and was applied to diverse targets that consist of natural and man-made materials and household objects. It was shown capable to resolve and distinguish small spectral differences among various targets, thanks to the laser radiometric and spectral accuracy. Colorless objects in the visible were shown with "colorful" signatures in the mid-IR. An essential feature of the study is an advanced system architecture that employs wavelength-division-multiplexed laser beams for high spectral fidelity and resolution. In addition, unlike conventional one-transmitter and one receiver design, the system is based on a scalable CDMA network concept with multiple transmitters and receivers to allow efficient information acquisition. The results suggest that multi-spectral laser imaging in general can be a unique and powerful technology for wide ranging applications.

  17. Three-dimensional direct cell patterning in collagen hydrogels with near-infrared femtosecond laser

    NASA Astrophysics Data System (ADS)

    Hribar, Kolin C.; Meggs, Kyle; Liu, Justin; Zhu, Wei; Qu, Xin; Chen, Shaochen

    2015-11-01

    We report a methodology for three-dimensional (3D) cell patterning in a hydrogel in situ. Gold nanorods within a cell-encapsulating collagen hydrogel absorb a focused near-infrared femtosecond laser beam, locally denaturing the collagen and forming channels, into which cells migrate, proliferate, and align in 3D. Importantly, pattern resolution is tunable based on writing speed and laser power, and high cell viability (>90%) is achieved using higher writing speeds and lower laser intensities. Overall, this patterning technique presents a flexible direct-write method that is applicable in tissue engineering systems where 3D alignment is critical (such as vascular, neural, cardiac, and muscle tissue).

  18. Three-dimensional direct cell patterning in collagen hydrogels with near-infrared femtosecond laser

    PubMed Central

    Hribar, Kolin C.; Meggs, Kyle; Liu, Justin; Zhu, Wei; Qu, Xin; Chen, Shaochen

    2015-01-01

    We report a methodology for three-dimensional (3D) cell patterning in a hydrogel in situ. Gold nanorods within a cell-encapsulating collagen hydrogel absorb a focused near-infrared femtosecond laser beam, locally denaturing the collagen and forming channels, into which cells migrate, proliferate, and align in 3D. Importantly, pattern resolution is tunable based on writing speed and laser power, and high cell viability (>90%) is achieved using higher writing speeds and lower laser intensities. Overall, this patterning technique presents a flexible direct-write method that is applicable in tissue engineering systems where 3D alignment is critical (such as vascular, neural, cardiac, and muscle tissue). PMID:26603915

  19. Cell perforation mediated by plasmonic bubbles generated by a single near infrared femtosecond laser pulse.

    PubMed

    Boutopoulos, Christos; Bergeron, Eric; Meunier, Michel

    2016-01-01

    We report on transient membrane perforation of living cancer cells using plasmonic gold nanoparticles (AuNPs) enhanced single near infrared (NIR) femtosecond (fs) laser pulse. Under optimized laser energy fluence, single pulse treatment (τ = 45 fs, λ = 800 nm) resulted in 77% cell perforation efficiency and 90% cell viability. Using dark field and ultrafast imaging, we demonstrated that the generation of submicron bubbles around the AuNPs is the necessary condition for the cell membrane perforation. AuNP clustering increased drastically the bubble generation efficiency, thus enabling an effective laser treatment using low energy dose in the NIR optical therapeutical window.

  20. Microprocessing of human hard tooth tissues surface by mid-infrared erbium lasers radiation

    NASA Astrophysics Data System (ADS)

    Belikov, Andrey V.; Shatilova, Ksenia V.; Skrypnik, Alexei V.

    2015-03-01

    A new method of hard tooth tissues laser treatment is described. The method consists in formation of regular microdefects on tissue surface by mid-infrared erbium laser radiation with propagation ratio M2<2 (Er-laser microprocessing). Proposed method was used for preparation of hard tooth tissues surface before filling for improvement of bond strength between tissues surface and restorative materials, microleakage reduction between tissues surface and restorative materials, and for caries prevention as a result of increasing microhardness and acid resistance of tooth enamel.

  1. Fiber based infrared lasers and their applications in medicine, spectroscopy and metrology

    NASA Astrophysics Data System (ADS)

    Alexander, Vinay Varkey

    In my thesis, I have demonstrated the development of fiber based infrared lasers and devices for applications in medicine, spectroscopy and metrology. One of the key accomplishments presented in this thesis for medical applications is the demonstration of a focused infrared laser to perform renal denervation both in vivo and in vitro. Hypertension is a significant health hazard in the US and throughout the world, and the laser based renal denervation procedure may be a potential treatment for resistant hypertension. Compared to current treatment modalities, lasers may be able to perform treatments with lesser collateral tissue damage and quicker treatment times helping to reduce patient discomfort and pain. An additional medical application demonstrated in this thesis is the use of infrared fiber lasers to damage sebaceous glands in human skin as a potential treatment for acne. Another significant work presented in this thesis is a field trial performed at the Wright Patterson Air Force Base using a Short Wave Infrared (SWIR) Supercontinuum (SC) laser as an active illumination source for long distance reflectance measurements. In this case, an SC laser developed as part of this thesis is kept on a 12 story tower and propagated through the atmosphere to a target kept 1.6 km away and used to perform spectroscopy measurements. In the future this technology may permit 24/7 surveillance based on looking for the spectral signatures of materials. Beyond applications in defense, this technology may have far reaching commercial applications as well, including areas such as oil and natural resources exploration. Beyond these major contributions to the state-of-the-art, this thesis also describes other significant studies such as power scalability of SWIR SC sources and non-invasive measurement of surface roughness.

  2. Monitoring corneal hydration with a mid-infrared (IR) laser.

    PubMed

    Joshi, Abhijeet; Bennett, David B; Stafsudd, Oscar M

    2015-01-01

    A mid-infrared (IR) source at ∼ 3 μm radiation is used as a probe to measure hydration in porcine cornea. Since the Er(3+):YAG emission targets vibrational modes (around 3300 cm(-1)) in the H2O molecule, it is highly sensitive to changes in water content in the first ∼ 10 μm of the corneal tissue.

  3. Near-infrared emitting ytterbium metal-organic frameworks with tunable excitation properties.

    PubMed

    White, Kiley A; Chengelis, Demetra A; Zeller, Matthias; Geib, Steven J; Szakos, Jessica; Petoud, Stéphane; Rosi, Nathaniel L

    2009-08-14

    The design of metal-organic frameworks (MOFs) incorporating near-infrared emitting ytterbium cations and organic sensitizers allows for the preparation of new materials with tunable and enhanced photophysical properties.

  4. 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.

  5. Near-infrared Single-photon-counting Detectors for Free-space Laser Receivers

    NASA Technical Reports Server (NTRS)

    Krainak, Michael A.; Sun, Xiaoli; Hasselbrack, William; Wu, Stewart; Waczynski, Augustyn; Miko, Laddawan

    2007-01-01

    We compare several photon-counting detector technologies for use as near-infrared timeresolved laser receivers in science instrument, communication and navigation systems. The key technologies are InGaAs(P) photocathode hybrid photomultiplier tubes and InGaAs(P) and HgCdTe avalanche photodiodes. We discuss recent experimental results and application.

  6. Low-intensity infrared laser radiation influence on the tumor growth

    NASA Astrophysics Data System (ADS)

    Cheida, A. A.; Efimova, E. G.

    2005-08-01

    Infrared laser radiation of low intensity in exposition dose of 25-35 mJicm2 does not cause progress the tumor process. Moreover, disturbing the blood flow in the tumor due to changing synthesis of norepinephrine and histamine this radiation contributes to the damage of the tumor tissue accompanied by the beginning of adaptation reaction in the organism.

  7. Prophylaxis and treatment of acute radiation ulcers in rats with low-power infrared laser radiation

    NASA Astrophysics Data System (ADS)

    Kursova, Larisa V.; Kaplan, Michael A.; Nikitina, Rosa G.; Maligina, Antonina I.

    1999-12-01

    Exposure of radiation ulcers in rats to low-power infrared laser radiation (LPLR) (wavelength--890 nm, pulse power--6 W, frequency--150 and 300 Hz, irradiation time--10 min) noticeably accelerates their healing, reduces exudative processes, increases number of specialized cells in wound. Application of LPLR prior to radiation damage decreases ulcer dimensions.

  8. Nucleotide excision repair pathway assessment in DNA exposed to low-intensity red and infrared lasers.

    PubMed

    Fonseca, A S; Campos, V M A; Magalhães, L A G; Paoli, F

    2015-10-01

    Low-intensity lasers are used for prevention and management of oral mucositis induced by anticancer therapy, but the effectiveness of treatment depends on the genetic characteristics of affected cells. This study evaluated the survival and induction of filamentation of Escherichia coli cells deficient in the nucleotide excision repair pathway, and the action of T4endonuclease V on plasmid DNA exposed to low-intensity red and near-infrared laser light. Cultures of wild-type (strain AB1157) E. coli and strain AB1886 (deficient in uvrA protein) were exposed to red (660 nm) and infrared (808 nm) lasers at various fluences, powers and emission modes to study bacterial survival and filamentation. Also, plasmid DNA was exposed to laser light to study DNA lesions produced in vitro by T4endonuclease V. Low-intensity lasers:i) had no effect on survival of wild-type E. coli but decreased the survival of uvrA protein-deficient cells,ii) induced bacterial filamentation, iii) did not alter the electrophoretic profile of plasmids in agarose gels, andiv) did not alter the electrophoretic profile of plasmids incubated with T4 endonuclease V. These results increase our understanding of the effects of laser light on cells with various genetic characteristics, such as xeroderma pigmentosum cells deficient in nucleotide excision pathway activity in patients with mucositis treated by low-intensity lasers.

  9. Low-intensity red and infrared lasers on XPA and XPC gene expression

    NASA Astrophysics Data System (ADS)

    Fonseca, A. S.; Magalhães, L. A. G.; Mencalha, A. L.; Ferreira-Machado, S. C.; Geller, M.; Paoli, F.

    2014-09-01

    Laser devices emit monochromatic, coherent, and highly collimated intense beams of light that are useful for a number of biomedical applications. However, for low-intensity lasers, possible adverse effects of laser light on DNA are still controversial. In this work, the expression of XPA and XPC genes in skin and muscle tissue exposed to low-intensity red and infrared lasers was evaluated. Skin and muscle tissue of Wistar rats were exposed to low-intensity red and infrared lasers at different fluences in continuous mode emission. Skin and muscle tissue samples were withdrawn for total RNA extraction, cDNA synthesis, and evaluation of actin gene expression by quantitative polymerase chain reaction. Data obtained show that laser radiation alters the expression of XPA and XPC mRNA differently in skin and muscle tissue of Wistar rats, depending on physical (fluence and wavelength) and biological (tissue) parameters. Laser light could modify expression of genes related to the nucleotide excision repair pathway at fluences and wavelengths used in clinical protocols.

  10. Nucleotide excision repair pathway assessment in DNA exposed to low-intensity red and infrared lasers

    PubMed Central

    Fonseca, A.S.; Campos, V.M.A.; Magalhães, L.A.G.; Paoli, F.

    2015-01-01

    Low-intensity lasers are used for prevention and management of oral mucositis induced by anticancer therapy, but the effectiveness of treatment depends on the genetic characteristics of affected cells. This study evaluated the survival and induction of filamentation of Escherichia coli cells deficient in the nucleotide excision repair pathway, and the action of T4endonuclease V on plasmid DNA exposed to low-intensity red and near-infrared laser light. Cultures of wild-type (strain AB1157) E. coli and strain AB1886 (deficient in uvrA protein) were exposed to red (660 nm) and infrared (808 nm) lasers at various fluences, powers and emission modes to study bacterial survival and filamentation. Also, plasmid DNA was exposed to laser light to study DNA lesions produced in vitro by T4endonuclease V. Low-intensity lasers:i) had no effect on survival of wild-type E. coli but decreased the survival of uvrA protein-deficient cells,ii) induced bacterial filamentation, iii) did not alter the electrophoretic profile of plasmids in agarose gels, andiv) did not alter the electrophoretic profile of plasmids incubated with T4 endonuclease V. These results increase our understanding of the effects of laser light on cells with various genetic characteristics, such as xeroderma pigmentosum cells deficient in nucleotide excision pathway activity in patients with mucositis treated by low-intensity lasers. PMID:26445337

  11. Femtosecond laser ablation with single and two-photon excitation for MEMS

    NASA Astrophysics Data System (ADS)

    Elbandrawy, Mohamed Abdelfattah Kottb Ahmad

    There is an increasing interest in femtosecond laser micromachining of materials because of the femtosecond laser's unique high peak power, ultrashort pulse width, negligible heat conductivity process during the laser pulse, and the minimal heat affected zone, which is in the same order of magnitude of the ablated submicron spot. There are some obstacles in reaching optimal and reliable micromachining parameters. One of these obstacles is the lack of understanding of the nature of the interaction and related physical processes. These processes include amorphization, melting, re-crystallization, nucleated-vaporization, and ablation. The focus of this Dissertation was to study the laser-matter interaction with single and two-photon excitation for optical micro-electro-mechanical system (OMEMS) applications. The laser pulse interaction mechanism was studied by performing a series of experiments including self-imaging experiments, two-photon absorption measurements, and micromachining processes characterizations. As a result of the self-imaging experiment, it was found for both Si and GaP that the material surface reflectivity increased twice as much during the action of the laser pulse. The generation of electron-hole plasma of 10 22cm-3 density was assigned to be responsible for the reflectivity jump. The Drude damping time of the generated plasma was determined to be 0.35 fs for silicon and 0.27 fs for gallium phosphate. Additionally, a precise measurement of the two-photon absorption (TPA) coefficient (beta) was done. The TPA coefficient was found to be 0.2 cm/GW. Experimental results were in good agreement with the theoretical expectations up to a point at which the ablation started kicking off and the plasma absorption took place. In case of a single pulse interaction with silicon, self-assembled nano-filaments of a few tens of microns' length and about 100 nm width were observed for the first time with the femtosecond single pulse interaction. The filaments were

  12. Infrared laser-based sensing in medical applications

    NASA Astrophysics Data System (ADS)

    Sigrist, Markus W.; Bartlome, Richard; Gianella, Michele

    2010-01-01

    Laser-spectroscopic applications in medicine increase in importance. We present two medical applications of laser-based analyses of trace gases. The analysis of exhaled breath concerns the determination of the D/H isotope ratio after intake of a small amount of heavy water. The D/H isotope ratio can be used to deduce the total body water weight and lays the foundation for many other laser-based clinical applications. An elevated D/H ratio could be monitored in breath samples up to 30 days after ingestion of only 5 ml of D2O. A second example concerns the analysis of surgical smoke produced in minimally invasive laparoscopic surgery with electroknives. The quantitative determination of harmless and hazardous compounds down to the ppm level is demonstrated. A specific example is the presence of sevoflurane at concentrations of 80 to 300 ppm, an anesthetic, which to our knowledge is measured for the first time in an abdominal cavity.

  13. Laser exposure analysis for a near-infrared ocular interferometer

    NASA Astrophysics Data System (ADS)

    Primeau, Brian C.; Goldstein, Goldie L.; Greivenkamp, John E.

    2012-06-01

    Ocular interferometry has potential value in a variety of ocular measurement applications, including measuring ocular thicknesses, topography of ocular surfaces or the wavefront of the eye. Of particular interest is using interferometry for characterizing corneal shape and irregular corneal features, making this technology attractive due to its inherent accuracy and spatial resolution. A particular challenge of designing an ocular interferometer is determining safe laser exposure levels to the eye, including both the retina and anterior segment. Described here are the laser exposure standards relevant in the interferometer design and the corresponding calculations and results. The results of this work can be used to aid in the design of similar laser-based systems for ocular evaluation.

  14. The Laser-assisted photoelectric effect of He, Ne, Ar and Xe in intense extreme ultraviolet and infrared laser fields

    NASA Astrophysics Data System (ADS)

    Hayden, P.; Dardis, J.; Hough, P.; Richardson, V.; Kennedy, E. T.; Costello, J. T.; Düsterer, S.; Redlin, H.; Feldhaus, J.; Li, W. B.; Cubaynes, D.; Meyer, M.

    2016-02-01

    In this paper, we report results on two-colour above-threshold ionisation, where extreme ultraviolet pulses of femtosecond duration were synchronised to intense infrared laser pulses of picosecond duration, in order to study the laser-assisted photoelectric effect of atomic helium, neon, krypton and xenon which leads to the appearance of characteristic sidebands in the photoelectron spectra. The observed trends are found to be well described by a simple model based on the soft-photon approximation, at least for the relatively low optical intensities of up to ? employed in these early experiments.

  15. Mid-Infrared Fiber Laser Based on Super-Continuum

    DTIC Science & Technology

    2007-01-31

    the pump wavelength. The gain fiber comprises a.lm of highly doped, large mode area ( LMA ) erbium-doped fiber amplifier (EDFA). Two 1480nm pump laser...amplified stimulation emission. In addition, the LMA EDFA can be incorporated and spliced into the pump laser set-up, and up to several Omni Sciences...Outputnput from 5m Nufern Er/Yb ~2SF ~0mL# gain fiber 71125 pm 6W 976nm pump Figure 4. Detailed lay-out for power amplifier stage using cladding

  16. Near infrared and visible luminescence from xerogels covalently grafted with lanthanide [Sm(3+), Yb(3+), Nd(3+), Er(3+), Pr(3+), Ho(3+)] β-diketonate derivatives using visible light excitation.

    PubMed

    Sun, Lining; Qiu, Yannan; Liu, Tao; Zhang, Jin Z; Dang, Song; Feng, Jing; Wang, Zhijuan; Zhang, Hongjie; Shi, Liyi

    2013-10-09

    A series of ternary lanthanide β-diketonate derivatives covalently bonded to xerogels (named as Ln-DP-xerogel, Ln = Sm, Yb, Nd, Er, Pr, Ho) by doubly functionalized alkoxysilane (dbm-Si) was synthesized in situ via a sol-gel process. The properties of these xerogel materials were investigated by Fourier-transform infrared (FT-IR) spectroscopy, field-emission scanning electron microscopy (FE-SEM), diffuse reflectance (DR) spectroscopy, thermogravimetric analyses, and fluorescence spectroscopy. The data and analyses suggest that the lanthanide derivatives have been covalently grafted to the corresponding xerogels successfully. Of importance here is that, after excitation with visible light (400-410 nm), the xerogels all show characteristic visible (Sm(3+)) as well as near-infrared (NIR; Sm(3+), Yb(3+), Nd(3+), Er(3+), Pr(3+), Ho(3+)) luminescence of the corresponding Ln(3+) ions, which is attributed to the energy transfer from the ligands to the Ln(3+) ions via an antenna effect. Exciting with visible light is advantageous over UV excitation. Furthermore, to the best of our knowledge, it is the first observation of NIR luminescence with visible light excitation from xerogels covalently bonded with the Sm(3+), Pr(3+), and Ho(3+) derivatives. Compared to lanthanide complexes (Ln = Er, Nd, Yb) functionalized periodic mesoporous organosilica (PMO) materials that exhibit similar optical properties reported in our previous work, the Ln-DP-xerogel (Ln = Sm, Yb, Nd, Er, Pr, Ho) in this case offer advantages in terms of ease of synthesis and handling and potentially low cost for emerging technological applications. Development of near-infrared luminescence of the lanthanide materials with visible light excitation is of strong interest to emerging applications such as chemosensors, laser systems, and optical amplifiers.

  17. Hundred-watt-level high power random distributed feedback Raman fiber laser at 1150 nm and its application in mid-infrared laser generation.

    PubMed

    Zhang, Hanwei; Zhou, Pu; Wang, Xiong; Du, Xueyuan; Xiao, Hu; Xu, Xiaojun

    2015-06-29

    Two kinds of hundred-watt-level random distributed feedback Raman fiber have been demonstrated. The optical efficiency can reach to as high as 84.8%. The reported power and efficiency of the random laser is the highest one as we know. We have also demonstrated that the developed random laser can be further used to pump a Ho-doped fiber laser for mid-infrared laser generation. Finally, 23 W 2050 nm laser is achieved. The presented laser can obtain high power output efficiently and conveniently and opens a new direction for high power laser sources at designed wavelength.

  18. Picosecond dissociation of amyloid fibrils with infrared laser: A nonequilibrium simulation study

    SciTech Connect

    Hoang Viet, Man; Roland, Christopher Sagui, Celeste; Derreumaux, Philippe; Nguyen, Phuong H.; Li, Mai Suan

    2015-10-21

    Recently, mid-infrared free-electron laser technology has been developed to dissociate amyloid fibrils. Here, we present a theoretical framework for this type of experiment based on laser-induced nonequilibrium all-atom molecular dynamics simulations. We show that the fibril is destroyed due to the strong resonance between its amide I vibrational modes and the laser field. The effects of laser irradiation are determined by a balance between fibril formation and dissociation. While the overall rearrangements of the fibril finish over short time scales, the interaction between the peptides and the solvent continues over much longer times indicating that the waters play an important role in the dissociation process. Our results thus provide new insights into amyloid fibril dissociation by laser techniques and open up new venues to investigate the complex phenomena associated with amyloidogenesis.

  19. Picosecond dissociation of amyloid fibrils with infrared laser: A nonequilibrium simulation study.

    PubMed

    Hoang Viet, Man; Derreumaux, Philippe; Li, Mai Suan; Roland, Christopher; Sagui, Celeste; Nguyen, Phuong H

    2015-10-21

    Recently, mid-infrared free-electron laser technology has been developed to dissociate amyloid fibrils. Here, we present a theoretical framework for this type of experiment based on laser-induced nonequilibrium all-atom molecular dynamics simulations. We show that the fibril is destroyed due to the strong resonance between its amide I vibrational modes and the laser field. The effects of laser irradiation are determined by a balance between fibril formation and dissociation. While the overall rearrangements of the fibril finish over short time scales, the interaction between the peptides and the solvent continues over much longer times indicating that the waters play an important role in the dissociation process. Our results thus provide new insights into amyloid fibril dissociation by laser techniques and open up new venues to investigate the complex phenomena associated with amyloidogenesis.

  20. Bismuth Oxide Thin Films Deposited on Silicon Through Pulsed Laser Ablation, for Infrared Detectors

    NASA Astrophysics Data System (ADS)

    Condurache-Bota, Simona; Constantinescu, Catalin; Tigau, Nicolae; Praisler, Mirela

    2016-12-01

    Infrared detectors are used in many human activities, from industry to military, telecommunications, environmental studies and even medicine. Bismuth oxide thin films have proved their potential for optoelectronic applications, but their uses as infrared sensors have not been thoroughly studied so far. In this paper, pulsed laser ablation of pure bismuth targets within a controlled oxygen atmosphere is proposed for the deposition of bismuth oxide films on Si (100) substrates. Crystalline films were obtained, whose uniformity depends on the deposition conditions (number of laser pulses and the use of a radio-frequency (RF) discharge of the oxygen inside the deposition chamber). The optical analysis proved that the refractive index of the films is higher than 3 and that their optical bandgap is around 1eV, recommending them for infrared applications.