Science.gov

Sample records for infrared laser excitation

  1. Advanced Excitation Techniques for Tunable Infrared Lasers.

    DTIC Science & Technology

    1979-07-01

    EXCITAT I ON TECHNI QUES FOR TUNA BLE I NFRARED LASERS 1. F. Ewanizky ~ Nig ht Vision & Elect ro-Optics Laboratory ERAD COM US ARMY ELECTRONICS...of this project. In order to enhance compatibility of this investigation with practical application, the pump laser was chosen to be of the target

  2. 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.

  3. Mechanism of oxidative stress generation in cells by localized near-infrared femtosecond laser excitation

    NASA Astrophysics Data System (ADS)

    He, Hao; Chan, Kam Tai; Kong, Siu Kai; Lee, Rebecca Kit Ying

    2009-12-01

    We examined the effect of femtosecond (fs) and continuous wave (CW) lasers at near-infrared range on the creation of reactive oxygen species in a human liver cancer cell line. By controlling the mitochondria electron transport chain (ETC), it was found that a major part of the oxidative stress was generated by the laser induced thermal effect on the mitochondria while the remaining part was created by direct free electron liberation by the fs pulses, which could be observed after breaking the ETC. The study helps clarify the major effects produced on animal cells when excited by fs lasers.

  4. 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.

  5. Two-photon vibrational excitation of air by long-wave infrared laser pulses

    NASA Astrophysics Data System (ADS)

    Palastro, J. P.; Peñano, J.; Johnson, L. A.; Hafizi, B.; Wahlstrand, J. K.; Milchberg, H. M.

    2016-08-01

    Ultrashort long-wave infrared (LWIR) laser pulses can resonantly excite vibrations in N2 and O2 through a two-photon transition. The absorptive vibrational component of the ultrafast optical nonlinearity grows in time, starting smaller than but quickly surpassing the electronic, rotational, and vibrational refractive components. The growth of the vibrational component results in a novel mechanism of third-harmonic generation, providing an additional two-photon excitation channel, fundamental + third harmonic. The original and emergent two-photon excitations drive the resonance exactly out of phase, causing spatial decay of the absorptive vibrational nonlinearity. This nearly eliminates two-photon vibrational absorption. Here we present simulations and analytical calculations demonstrating how these processes modify the ultrafast optical nonlinearity in air. The results reveal nonlinear optical phenomena unique to the LWIR regime of ultrashort pulse propagation in the atmosphere.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. Resonance Raman spectroscopy of red blood cells using near-infrared laser excitation.

    PubMed

    Wood, Bayden R; Caspers, Peter; Puppels, Gerwin J; Pandiancherri, Shveta; McNaughton, Don

    2007-03-01

    Resonance Raman spectra of oxygenated and deoxygenated functional erythrocytes recorded using 785 nm laser excitation are presented. The high-quality spectra show a mixture of enhanced A(1g), A(2g), B(1g), B(2g), E(u) and vinyl modes. The high sensitivity of the Raman system enabled spectra from four oxygenation and deoxygenation cycles to be recorded with only 18 mW of power at the sample over a 60-minute period. This low power prevented photo-/thermal degradation and negated protein denaturation leading to heme aggregation. The large database consisting of 210 spectra from the four cycles was analyzed with principal components analysis (PCA). The PC1 loadings plot provided exquisite detail on bands associated with the oxygenated and deoxygenated states. The enhancement of a band at 567 cm(-1), observed in the spectra of oxygenated cells and the corresponding PC1 loadings plot, was assigned to the Fe-O(2) stretching mode, while a band appearing at 419 cm(-1) was assigned to the Fe-O-O bending mode based on previous studies. For deoxygenated cells, the enhancement of B(1g) modes at 785 nm excitation is consistent with vibronic coupling between band III and the Soret transition. In the case of oxygenated cells, the enhancement of iron-axial out-of-plane modes and non-totally symmetric modes is consistent with enhancement into the y,z-polarized transition a(iu)(pi)-->d(xz)+O(2)(pi(g)) centered at 785 nm. The enhancement of non-totally symmetric B(1g) modes in oxygenated cells suggests vibronic coupling between band IV and the Soret band. This study provides new insights into the vibrational dynamics, electronic structure and resonant enhancement of heme moieties within functional erythrocytes at near-IR excitation wavelengths.

  16. 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.

  17. CINE: Comet INfrared Excitation

    NASA Astrophysics Data System (ADS)

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

    2017-08-01

    CINE calculates infrared pumping efficiencies that can be applied to the most common molecules found in cometary comae such as water, hydrogen cyanide or methanol. One of the main mechanisms for molecular excitation in comets is the fluorescence by the solar radiation followed by radiative decay to the ground vibrational state. This command-line tool calculates the effective pumping rates for rotational levels in the ground vibrational state scaled by the heliocentric distance of the comet. Fluorescence 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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)

  3. 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)

  4. Optical Properties of Small Band Gap Semiconductors Subject to Laser Excitation. Nonlinear Infrared Properties of Semiconductors.

    DTIC Science & Technology

    1982-01-01

    the Ill-V semiconductors with large spin -orbit splitting . These included GaAs, G&Sb, InAs, AlSb as w ll as Ge. The theory was further extended to...includle Lhe effects of the spin orbit split -off valence band in publication 12. E. 7hory of Pump and Probe Experiments To develop an understanding of the...James and D. L. Smith, "Absorption of High-Intensity 002 Laser Light in p-Type Semiconductors with Small Spin -Orbit Splittings ", J. Appi. Phys. S2

  5. 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.

  6. 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-).

  7. 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.

  8. 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.

  9. Fluorescence Detection of H5N1 Virus Gene Sequences Based on Optical Tweezers with Two-Photon Excitation Using a Single Near Infrared Nanosecond Pulse Laser.

    PubMed

    Li, Cheng-Yu; Cao, Di; Kang, Ya-Feng; Lin, Yi; Cui, Ran; Pang, Dai-Wen; Tang, Hong-Wu

    2016-04-19

    We present an analytical platform by combining near-infrared optical tweezers with two-photon excitation for fluorescence detection of H5N1 virus gene sequences. A heterogeneous enrichment strategy, which involved polystyrene (PS) microsphere and quantum dots (QDs), was adopted. The final hybrid-conjugate microspheres were prepared by a facile one-step hybridization procedure by using PS microspheres capturing target DNA and QDs tagging, respectively. Quantitative detection was achieved by the optical tweezers setup with a low-cost 1064 nm nanosecond pulse laser for both optical trapping and two-photon excitation for the same hybrid-conjugate microsphere. The detection limits for both neuraminidase (NA) gene sequences and hemagglutinin (HA) gene sequences are 16-19 pM with good selectivity for one-base mismatch, which is approximately 1 order of magnitude lower than the most existing fluorescence-based analysis method. Besides, because of the fact that only signal from the trapped particle is detected upon two-photon excitation, this approach showed extremely low background in fluorescence detection and was successfully applied to directly detect target DNA in human whole serum without any separation steps and the corresponding results are very close to that in buffer solution, indicating the strong anti-interference ability of this method. Therefore, it can be expected to be an emerging alternative for straightforward detecting target species in complex samples with a simple procedure and high-throughput.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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

  15. Infrared light excites cells by changing their electrical capacitance

    PubMed Central

    Shapiro, Mikhail G.; Homma, Kazuaki; Villarreal, Sebastian; Richter, Claus-Peter; Bezanilla, Francisco

    2012-01-01

    Optical stimulation has enabled important advances in the study of brain function and other biological processes, and holds promise for medical applications ranging from hearing restoration to cardiac pace making. In particular, pulsed laser stimulation using infrared wavelengths >1.5 μm has therapeutic potential based on its ability to directly stimulate nerves and muscles without any genetic or chemical pre-treatment. However, the mechanism of infrared stimulation has been a mystery, hindering its path to the clinic. Here we show that infrared light excites cells through a novel, highly general electrostatic mechanism. Infrared pulses are absorbed by water, producing a rapid local increase in temperature. This heating reversibly alters the electrical capacitance of the plasma membrane, depolarizing the target cell. This mechanism is fully reversible and requires only the most basic properties of cell membranes. Our findings underscore the generality of pulsed infrared stimulation and its medical potential. PMID:22415827

  16. Excited triplet state spectroscopy in the infrared

    NASA Astrophysics Data System (ADS)

    Baiardo, Joseph; Mukherjee, Ranajit; Vala, Martin

    1982-03-01

    A new method for the investigation of the infrared spectra of metastable excitedelectronic states is presented. With a Fourier Transform infrared spectrometer as the probe and a CW Xe lamp source as the pump, the infrared spectrum of the lowest triplet state of triphenylene isolated in a N 2 matrix at 15K has been examined. CH out-of-plane wagging modes are prominent and shifted from their ground state frequencies. It is expected that when fully developed this method will provide important information on excited state force constants and potential energy surfaces.

  17. 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.

  18. 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

  19. Infrared laser writing of MOFs.

    PubMed

    Hirai, K; Sada, K

    2017-05-09

    An infrared (IR) laser machine is used for the synthesis of metal-organic frameworks (MOFs). Solutions containing metal ions and organic ligands are casted on glass substrates. MOF crystals are formed at the positions the IR laser irradiated, resulting in the patterning of MOFs.

  20. University of Florida nuclear pumped laser program. [excitation of laser gaseous

    NASA Technical Reports Server (NTRS)

    Schneider, R. T.

    1979-01-01

    The mechanism of excitation of laser gases by fast ions (triton, proton, or fission fragments) and especially any role UF6 might play in radiative deexcitation of these gases were investigated. Population densities of excited important for laser action were obtained. Nuclear pumped CW-laser systems, especially He-Ne and CO2, were studied using steady state reactors. It was demonstrated that He-Ne lases in a CW-mode with nuclear pumping at both the red and the infrared transition. The infrared transition was observed to be superradiant.

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. Infrared laser sclerostomies.

    PubMed

    Ozler, S A; Hill, R A; Andrews, J J; Baerveldt, G; Berns, M W

    1991-08-01

    Four solid-state lasers with three fiberoptic delivery systems were used to perform laser sclerostomies in an acute-injury rabbit model and in fresh human globes. The lasers used were continuous-wave neodymium:yttrium aluminum garnet (YAG, 1.06 microns) and pulsed holmium:yttrium scandium galliam garnet (YSGG) (2.10 microns), erbium:YSGG (2.79 microns), and erbium:YAG (2.94 microns). Thermal damage to tissue and total laser energy required to produce sclerostomies decreased with increasing wavelength. In human tissue using a 600-microns fused silica fiberoptic, maximum thermal damage (greater than or equal to 100 microns) was noted at 1.06 microns with a total energy of 21 J at a power density of 2.5 kW/cm2. In addition, focal damage to the iris and ciliary body was noted at this wavelength. The least amount of thermal damage (15-20 microns) and lowest total energies needed were found at 2.94 microns. A 250-microseconds pulse length and pulse radiant exposures of 3.6 J/cm2 and 14.3 J/cm2 were used for the low hydroxyl-fused silica (500 microns) and zirconium fluoride (250 microns) fiberoptics, respectively. Although zirconium fluoride fibers have high through-put efficiencies that facilitate study of laser tissue interactions at 2.94 microns, problems encountered with fragility and solubility of the bare tip in aqueous media limit its usefulness. A high attenuation rate with the low hydroxyl-fused silica fiber limited its usable length to 35 cm at 2.94 microns. Tissue damage during sclerostomy formation was minimized at 2.94 microns, reaching a maximum at 1.06 microns. Minimizing tissue damage theoretically could decrease subconjunctival scarring and filtration failure.(ABSTRACT TRUNCATED AT 250 WORDS)

  10. [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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. Investigating the 3.3 micron infrared fluorescence from naphthalene following ultraviolet excitation

    NASA Technical Reports Server (NTRS)

    Williams, Richard M.; Leone, Stephen R.

    1994-01-01

    Polycyclic aromatic hydrocarbon (PAH) type molecules are proposed as the carriers of the unidentified infrared (UIR) bands. Detailed studies of the 3.3 micrometer infrared emission features from naphthalene, the simplest PAH, following ultraviolet laser excitation are used in the interpretation of the 3.29 micrometer (3040 cm(sup -1)) UIR band. A time-resolved Fourier transform spectrometer is used to record the infrared emission spectrum of gas-phase naphthalene subsequent to ultraviolet excitation facilitated by an excimer laser operated at either 193 nm or 248 nm. The emission spectra differ significantly from the absorption spectrum in the same spectral region. Following 193 nm excitation the maximum in the emission profile is red-shifted 45 cm(sup -1) relative to the absorption maximum; a 25 cm(sup -1) red-shift is observed after 248 nm excitation. The red-shifting of the emission spectrum is reduced as collisional and radiative relaxation removes energy from the highly vibrationally excited molecules. Coupling between the various vibrational modes is thought to account for the differences between absorption and emission spectra. Strong visible emission is also observed following ultraviolet excitation. Visible emission may play an important role in the rate of radiative relaxation, which according to the interstellar PAH hypothesis occurs only by the slow emission of infrared photons. Studying the visible emission properties of PAH type molecules may be useful in the interpretation of the DIB's observed in absorption.

  18. 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

  19. Laser-Induced Incandescence: Excitation Intensity

    NASA Astrophysics Data System (ADS)

    Vander Wal, Randall L.; Jensen, Kirk A.

    1998-03-01

    Assumptions of theoretical laser-induced incandescence (LII) models along with possible effects of high-intensity laser light on soot aggregates and the constituent primary particles are discussed in relation to selection of excitation laser fluence. Ex situ visualization of laser-heated soot by use of transmission electron microscopy reveals significant morphological changes (graphitization) induced by pulsed laser heating. Pulsed laser transmission measurements within a premixed laminar sooting flame suggest that soot vaporization occurs for laser fluences greater than 0.5 J cm 2 at 1064 nm. Radial LII intensity profiles at different axial heights in a laminar ethylene gas jet diffusion flame reveal a wide range of signal levels depending on the laser fluence that is varied over an eight fold range. Results of double-pulse excitation experiments in which a second laser pulse heats in situ the same soot that was heated by a prior laser pulse are detailed. These two-pulse measurements suggest varying degrees of soot structural change for fluences below and above a vaporization threshold of 0.5 J cm 2 at 1064 nm. Normalization of the radial-resolved LII signals based on integrated intensities, however, yields self-similar profiles. The self-similarity suggests robustness of LII for accurate relative measurement of soot volume fraction despite the morphological changes induced in the soot, variations in soot aggregate and primary particle size, and local gas temperature. Comparison of LII intensity profiles with soot volume fractions ( f v ) derived by light extinction validates LII for quantitative determination of f v upon calibration for laser fluences ranging from 0.09 to 0.73 J cm 2 .

  20. Laser-induced incandescence: excitation intensity.

    PubMed

    Vander Wal, R L; Jensen, K A

    1998-03-20

    Assumptions of theoretical laser-induced incandescence (LII) models along with possible effects of high-intensity laser light on soot aggregates and the constituent primary particles are discussed in relation to selection of excitation laser fluence. Ex situ visualization of laser-heated soot by use of transmission electron microscopy reveals significant morphological changes (graphitization) induced by pulsed laser heating. Pulsed laser transmission measurements within a premixed laminar sooting flame suggest that soot vaporization occurs for laser fluences greater than 0.5 J/cm(2) at 1064 nm. Radial LII intensity profiles at different axial heights in a laminar ethylene gas jet diffusion flame reveal a wide range of signal levels depending on the laser fluence that is varied over an eight fold range. Results of double-pulse excitation experiments in which a second laser pulse heats in situ the same soot that was heated by a prior laser pulse are detailed. These two-pulse measurements suggest varying degrees of soot structural change for fluences below and above a vaporization threshold of 0.5 J/cm(2) at 1064 nm. Normalization of the radial-resolved LII signals based on integrated intensities, however, yields self-similar profiles. The self-similarity suggests robustness of LII for accurate relative measurement of soot volume fraction despite the morphological changes induced in the soot, variations in soot aggregate and primary particle size, and local gas temperature. Comparison of LII intensity profiles with soot volume fractions (f(v)) derived by light extinction validates LII for quantitative determination of f(v) upon calibration for laser fluences ranging from 0.09 to 0.73 J/cm(2).

  1. Short infrared laser pulses block action potentials in neurons

    NASA Astrophysics Data System (ADS)

    Walsh, Alex J.; Tolstykh, Gleb P.; Martens, Stacey L.; Ibey, Bennett L.; Beier, Hope T.

    2017-02-01

    Short infrared laser pulses have many physiological effects on cells including the ability to stimulate action potentials in neurons. Here we show that short infrared laser pulses can also reversibly block action potentials. Primary rat hippocampal neurons were transfected with the Optopatch2 plasmid, which contains both a blue-light activated channel rhodopsin (CheRiff) and a red-light fluorescent membrane voltage reporter (QuasAr2). This optogenetic platform allows robust stimulation and recording of action potential activity in neurons in a non-contact, low noise manner. For all experiments, QuasAr2 was imaged continuously on a wide-field fluorescent microscope using a Krypton laser (647 nm) as the excitation source and an EMCCD camera operating at 1000 Hz to collect emitted fluorescence. A co-aligned Argon laser (488 nm, 5 ms at 10Hz) provided activation light for CheRiff. A 200 mm fiber delivered infrared light locally to the target neuron. Reversible action potential block in neurons was observed following a short infrared laser pulse (0.26-0.96 J/cm2; 1.37-5.01 ms; 1869 nm), with the block persisting for more than 1 s with exposures greater than 0.69 J/cm2. Action potential block was sustained for 30 s with the short infrared laser pulsed at 1-7 Hz. Full recovery of neuronal activity was observed 5-30s post-infrared exposure. These results indicate that optogenetics provides a robust platform for the study of action potential block and that short infrared laser pulses can be used for non-contact, reversible action potential block.

  2. Vacuum ultraviolet argon excimer laser at 126 nm excited by a high intensity laser

    NASA Astrophysics Data System (ADS)

    Kaku, Masanori; Harano, Shinya; Katto, Masahito; Kubodera, Shoichi

    2010-09-01

    We have observed the optical amplification of the Ar2* excimer at 126 nm pumped by optical-field-induced ionization (OFI) caused by an infrared high-intensity laser. We have evaluated similar small signal gain coefficients of approximately 1.0 cm-1 in two different experiments, where OFI Ar plasmas as gain media were produced in free space filled with Ar and inside an Ar-filled hollow fiber. This indicates that the function of a hollow fiber was to guide the infrared excitation laser and VUV Ar2* emissions, and not to regulate the OFI plasma. Despite the gain coefficient value at 126 nm, the laser oscillation has not been observed. This was limited by the optical quality of available state-of-the-art vacuum ultraviolet optics.

  3. 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.

  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. 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.

  6. [Infrared spectroscopy based on quantum cascade lasers].

    PubMed

    Wen, Zhong-Quan; Chen, Gang; Peng, Chen; Yuan, Wei-Qing

    2013-04-01

    Quantum cascade lasers (QCLs) are promising infrared coherent sources. Thanks to the quantum theory and band-gap engineering, QCL can access the wavelength in the range from 3 to 100 microm. Since the fingerprint spectrum of most gases are located in the mid-infrared range, mid-infrared quantum cascade laser based gas sensing technique has become the research focus world wide because of its high power, narrow linewidth and fast scanning. Recent progress in the QCL technology leads to a great improvement in laser output power and efficiency, which stimulates a fast development in the infrared laser spectroscopy. The present paper gives a broad review on the QCL based spectroscopy techniques according to their working principles. A discussion on their applications in gas sensing and explosive detecting is also given at the end of the paper.

  7. Optical modulation of quantum cascade laser with optimized excitation wavelength.

    PubMed

    Yang, Tao; Chen, Gang; Tian, Chao; Martini, Rainer

    2013-04-15

    The excitation wavelength for all-optical modulation of a 10.6 μm mid-infrared (MIR) quantum cascade laser (QCL) was varied in order to obtain maximum modulation depth. Both amplitude and wavelength modulation experiments were conducted at 820 nm and 1550 nm excitation respectively, whereby the latter matches the interband transition in the QCL active region. Experimental results show that for continuous-wave mode-operated QCL, the efficiency of free carrier generation is doubled under 1550 nm excitation compared with 820 nm excitation, resulting in an increase of the amplitude modulation index from 19% to 36%. At the same time, the maximum wavelength shift is more than doubled from 1.05 nm to 2.80 nm. Furthermore, for the first time to our knowledge, we demonstrated the optical switching of a QCL operated in pulse mode by simple variation of the excitation wavelength.

  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. Satellite and lunar laser ranging in infrared

    NASA Astrophysics Data System (ADS)

    Courde, Clement; Torre, Jean-Marie; Samain, Etienne; Martinot-Lagarde, Gregoire; Aimar, Mourad; Albanese, Dominique; Maurice, Nicolas; Mariey, Hervé; Viot, Hervé; Exertier, Pierre; Fienga, Agnes; Viswanathan, Vishnu

    2017-05-01

    We report on the implementation of a new infrared detection at the Grasse lunar laser ranging station and describe how infrared telemetry improves the situation. We present our first results on the lunar reflectors and show that infrared detection permits us to densify the observations and allows measurements during the new and the full moon periods. We also present the benefit obtained on the ranging of Global Navigation Satellite System (GNSS) satellites and on RadioAstron which have a very elliptic orbit.

  11. 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

  12. 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.

  13. 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.

  14. Photophysics of infrared multiphoton excitation in thiophosgene

    SciTech Connect

    Brenner, D.M.; Spencer, M.N.; Steinfeld, J.I.

    1983-01-01

    IR multiphoton absorption (IRMPA) in thiophosgene has been studied by IR-visible double resonance. In particular, the probability of absorption has been measured in both collision-free (molecular beam) and collision-perturbed environments by monitoring the depopulation of the ground state level (000000). Although no evidence for true multiphoton absorption is found, a number of important observations have been made. (1) No correlation exists between the IRMPA spectrum under collision-free conditions and the low energy IR absorption spectrum. (2) Homogeneous depletion of rotational populations occurs at all CO/sub 2/-laser frequencies. (3) Bottlenecks to absorption do not occur in the pumped-mode ladder. (4) The probability of absorption depends inversely on pressure and is affected dramatically by long-range collisions. These results are interpreted in the framework of an optical Bloch equation model.

  15. Efficient Pr3+ laser material excitation by three-for-one cross-relaxation

    NASA Astrophysics Data System (ADS)

    Merkle, Larry D.; Dubinskii, Mark

    2017-05-01

    Pr3+ has three excited manifolds with the right energy spacings for emission between 3.5 and 5.5 microns, and can be excited efficiently using laser diodes developed for telecommunications. In the potential laser crystal Pr:RbPb2Cl5, we have observed strikingly strong fluorescence in this wavelength range following 1.53-micron excitation. Careful analysis indicates this must be due to two cross-relaxation processes that, together, efficiently convert one Pr3+ initially excited to the 3F3 manifold into three ions excited to the 3H5 manifold. This newly discovered "three-for-one" crossrelaxation process in Pr3+ may greatly enhance its utility as a mid-infrared laser ion.

  16. Titanium: Sapphire laser as an excitation source in two-photon spectroscopy

    SciTech Connect

    Fisher, W.G.; Wachter, E.A.; Armas, M.; Seaton, C.

    1997-02-01

    The passively mode-locked titanium:sapphire laser provides new opportunities for acquiring two-photon spectral data in the near-infrared, a region not commonly accessible to synchronously pumped dye lasers. This source generates pulses with peak powers near 100 kW at average powers over 1 W and is capable of yielding two-photon signals roughly two orders of magnitude larger than is possible with synchronously pumped dye lasers. However, the multimode output of this laser exhibits significant temporal and spectral pulse profile variations as the laser wavelength is tuned. As a consequence, peak powers of the titanium:sapphire laser can vary independently from average power across the tuning range. This wavelength dependence, coupled with the quadratic dependence of the two-photon signal upon the instantaneous power of the laser, precludes simple average power correction of nonlinear spectral band shapes. Here, we investigate the key properties of the titanium:sapphire laser as an excitation source for two-photon spectroscopy. We also identify a chemical reference suitable for obtaining source-corrected excitation spectra in the near-infrared using a double-beam, ratiometric approach; this is based on a source-independent two-photon excitation spectrum for the laser dye coumarin-480 that has been obtained with a single-frequency titanium:sapphire laser. From these data, correction factors are generated for correction of multimode source data. {copyright} {ital 1997} {ital Society for Applied Spectroscopy}

  17. Pulsed cyclic laser based on dissociative excitation

    SciTech Connect

    Celto, J.E.; Schimitschek, E.J.

    1980-10-14

    A pulsed laser produces emitted laser energy by dissociative excitation of metal dihalide and cyclic recombination. A metal dihalide selected from subgroup ii-b of the periodic table of elements is contained within an elongate sealed enclosure. Two elongate electrodes having external terminals are supported in parallel relationship within the enclosure, forming a gap parallel to the principal axis of the enclosure. A source of pulsed electric power is connected to the terminals of the two electrodes, producing repetitive transverse electric discharges across the gap. An inert buffer gas is included within the enclosure for aiding electric discharge uniformity, and to provide vibrational relaxation of the lasing medium in its electronic states. The buffer gas is ionized by a third electrode within the enclosure connected to a source of pulses which immediately precede the pulses applied to the first and second electrode so that the lasing medium is preionized immediately prior to the principal electric discharge. Two reflective surfaces, one of which is only partially reflective, are aligned with the principal axis of the laser assembly for producing an optical resonator for the emitted laser energy.

  18. 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

  19. 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.

  20. Lunar laser ranging in infrared at the Grasse laser station

    NASA Astrophysics Data System (ADS)

    Courde, C.; Torre, J. M.; Samain, E.; Martinot-Lagarde, G.; Aimar, M.; Albanese, D.; Exertier, P.; Fienga, A.; Mariey, H.; Metris, G.; Viot, H.; Viswanathan, V.

    2017-06-01

    For many years, lunar laser ranging (LLR) observations using a green wavelength have suffered an inhomogeneity problem both temporally and spatially. This paper reports on the implementation of a new infrared detection at the Grasse LLR station and describes how infrared telemetry improves this situation. Our first results show that infrared detection permits us to densify the observations and allows measurements during the new and the full Moon periods. The link budget improvement leads to homogeneous telemetric measurements on each lunar retro-reflector. Finally, a surprising result is obtained on the Lunokhod 2 array which attains the same efficiency as Lunokhod 1 with an infrared laser link, although those two targets exhibit a differential efficiency of six with a green laser link.

  1. 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

  2. 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.

  3. 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

  4. Nonsequential double ionization with mid-infrared laser fields

    SciTech Connect

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

    2016-11-18

    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. Here, 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.

  5. Nonsequential double ionization with mid-infrared laser fields

    DOE PAGES

    Li, Ying -Bin; Wang, Xu; Yu, Ben -Hai; ...

    2016-11-18

    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. Here, 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 finalmore » energies of the two electrons can be extremely unequal, leading to novel e-e momentum correlation spectra that can be measured experimentally.« less

  6. 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

  7. Quantum-cascade lasers enable infrared sensors

    SciTech Connect

    Schultz, John F. )

    2003-05-01

    Quantum-cascade lasers (QCLs) are semiconductor-injection lasers based on intersubband transitions in a multiple-quantum-well heterostructure. They are designed using band-structure engineering and grown by molecular beam epitaxy. The emission wavelength of a QCL is primarily a function of quantum-well thickness--thinner quantum wells lead to shorter wavelengths--and is essentially independent of the material bandgap. Quantum-cascade lasers can be designed to operate at any wavelength from 3.5 m (infrared) to 67 m (terahertz region) and are continuously tunable through ranges of a few inverse centimeters.1, 2, 3 This capability makes them well suited for spectroscopy in the infrared (see Laser Focus World, August 1999, p. 40).

  8. Infrared laser hemotherapy in cerebral ischemia modeling

    NASA Astrophysics Data System (ADS)

    Musienko, Julia I.; Nechipurenko, Natalia I.

    2003-10-01

    Use of intravenous laser irradiation of blood (ILIB) is considered to be the most effective method of laser therapy and its application is expedient pathogenetically in the ischemic disturbances. The aim of this study is to investigate ILIB influence with infrared laser (IL) with 860 nm wavelength on hemostasis, acid-base status (ABS) of blood in normal rabbits and after modeling of local ischemia of brain (LIB). Experimental cerebral ischemia is characterized by development of hypercoagulation syndrom and metabolic acidosis. ILIB with infrared radiation of 2.0 mW power provokes hypocoagulation in intact animals. Application of ILIB in rabbits after LIB contributes for hemostasis and acid-base status normalizing compared to operated animals. IL radiation with 8,5 mW power results in marked hemostatic activation in all animals. Therefore, beneficial effect of low power laser radiation (LPLR) manifests in narrow power diapason in experimental brain ischemia.

  9. 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.

  10. 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

  11. 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

  12. 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.

  13. 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.

  14. 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)

  15. 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

  16. 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

  17. 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.

  18. White light emission from Er2O3 nano-powder excited by infrared radiation

    NASA Astrophysics Data System (ADS)

    Tabanli, Sevcan; Eryurek, Gonul; Di Bartolo, Baldassare

    2017-07-01

    Phosphors of Er2O3 nano-crystalline powders were synthesized by the thermal decomposition method. The structural properties of the nano-powders were investigated with XRD and HRTEM measurements. The cubic phase with a = 10.540 Å was the only phase observed. The average crystalline sizes and the widths of the grain size distribution curves were determined to be 27.2, 18.7 and 9.7 nm, respectively. The spectroscopic properties of the Er2O3 nano-powder were studied by measuring the luminescence, decay and rise patterns under 808 and 975 nm diode laser excitations. A peculiar effect of the pressure was observed since an optically active ion (Er) is part of the complex and not a dopant. A broad band of the white light emission combined with blue, green and red up-conversion emission bands of Er3+ ions were observed at 0.03 mbar pressure under both excitation wavelengths. Only, an intense broad band white light emission was observed from these nanocrystals at atmospheric pressure. Rising patterns show that the white light intensity reaches its maximum value more rapidly under 975 nm excitation although it decays slower than that of 808 nm excitation. The color quality parameters such as the color coordinate (CRI), correlated color temperature and the color rendering index were found to vary with both the excitation wavelength and the ambient pressure indicating that these nanocrystals could be considered good white light emitting source under the infrared excitations.

  19. 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

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. Spontaneously excited pulses in an optically driven semiconductor laser.

    PubMed

    Wieczorek, Sebastian; Lenstra, Daan

    2004-01-01

    In optically injected semiconductor lasers, intrinsic quantum noise alone, namely, the spontaneous emission and the shot noise, are capable of exciting intensity multipulses from a steady state operation. Noisy lasers exhibit self-pulsations in the locking region of the corresponding deterministic system. The interpulse time statistics are studied in parameter regions near k-homoclinic (Shilnikov) bifurcations where the corresponding deterministic model exhibits single-, double-, and triple-pulse excitability. These statistics differ significantly among each other, and they could be used to characterize regions of different multipulse excitability in a real laser device.

  6. 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. Published 2015 Wiley Periodicals Inc. on

  7. Recombination-pumped triatomic hydrogen infrared lasers

    NASA Astrophysics Data System (ADS)

    Saykally, R. J.; Michael, E. A.; Wang, J.; Greene, Chris H.

    2010-12-01

    Mid-infrared laser lines observed in hydrogen/rare gas discharges are assigned to three-body recombination processes involving an electron, a rare gas (He or Ne) atom, and the triatomic hydrogen ion (H3+). Calculations of radiative transitions between neutral H3 Rydberg states support this interpretation, and link it to recent results for hydrogenic/rare gas afterglow plasmas. A mechanism for the population inversion is proposed, and the potential generality and astrophysical implications of such molecular recombination laser systems are briefly discussed.

  8. 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.

  9. Alternative infrared lasers for endoscopic surgery

    NASA Astrophysics Data System (ADS)

    Bass, Lawrence S.; Font, David E.; Oz, Mehmet C.; Trokel, Stephen L.; Treat, Michael R.

    1990-06-01

    There are substantial technical problems attendant to the removal of sessile polyps from the lumen of thin walled gastrointestinal organs such as the colon. A laser system which is capable of precise and circumscribed mucosal tissue vaporization would be useful for this task. Because of technical shortcomings of existing medical laser systems, we investigated the possibilities of mid-infrared lasers which could take advantage of large water absorption peaks in the 2 micron region to produce precise vaporization while retaining fiberoptic transmissibility. In addition to a high absorption wavelength, pulsed energy delivery contributes to precise vaporizing capabilities. The laser system that best fits our criteria is the 2.15 micron thulium-holmium- chromium:YAG which produces 200 microsecond pulses of energies up to 1 joule at firing rates up to 6 Hz. The laser output is transmitted efficiently via low hydroxyl quartz fibers. Ablative efficiency, defined here as the slope of the vaporization depth versus energy, reveals that the THC:YAG produces approximately 3 times greater depth of vaporization per joule than the cw Nd:YAG. On average, the Nd:YAG produced 1.5 times the amount of thermal damage as the THC:YAG for a given depth of vaporization. The THC:YAG laser should have an important clinical role since its use could reduce the risk of perforation in endoscopic laser procedures such as the removal of sessile polyps.

  10. Excitation and Control of Plasma Wakefields by Multiple Laser Pulses

    NASA Astrophysics Data System (ADS)

    Cowley, J.; Thornton, C.; Arran, C.; Shalloo, R. J.; Corner, L.; Cheung, G.; Gregory, C. D.; Mangles, S. P. D.; Matlis, N. H.; Symes, D. R.; Walczak, R.; Hooker, S. M.

    2017-07-01

    We demonstrate experimentally the resonant excitation of plasma waves by trains of laser pulses. We also take an important first step to achieving an energy recovery plasma accelerator by showing that a plasma wave can be damped by an out-of-resonance trailing laser pulse. The measured laser wakefields are found to be in excellent agreement with analytical and numerical models of wakefield excitation in the linear regime. Our results indicate a promising direction for achieving highly controlled, GeV-scale laser-plasma accelerators operating at multikilohertz repetition rates.

  11. 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

  12. 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

  13. A new technology for applanation free corneal trephination: the picosecond infrared laser (PIRL).

    PubMed

    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.

  14. 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.

  15. 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.

  16. 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.

  17. 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

  18. Mid-Infrared Laser Orbital Septal Tightening

    PubMed Central

    Chu, Eugene A.; Li, Michael; Lazarow, Frances B.; Wong, Brian J. F.

    2014-01-01

    IMPORTANCE Blepharoplasty is one of the most commonly performed facial aesthetic surgeries. While myriad techniques exist to improve the appearance of the lower eyelids, there is no clear consensus on the optimal management of the orbital septum. OBJECTIVES To evaluate the safety and feasibility of the use of the holmium:yttrium aluminum garnet (Ho:YAG) laser for orbital septal tightening, and to determine whether modest use of this laser would provide some degree of clinical efficacy. DESIGN, SETTING, AND PARTICIPANTS Direct laser irradiation of ex vivo bovine tissue was used to determine appropriate laser dosimetry using infrared thermal imaging and optical coherence tomography before conducting a pilot clinical study in 5 patients. Laser irradiation of the lower eyelid orbital septum was performed through a transconjunctival approach. Standardized preoperative and postoperative photographs were taken for each patient and evaluated by 6 unbiased aesthetic surgeons. EXPOSURE Use of the Ho:YAG laser for orbital septal tightening. MAIN OUTCOME AND MEASURE To determine appropriate laser dosimetry, infrared thermal imaging and optical coherence tomography were used to monitor temperature and tissue shape changes of ex vivo bovine tissue that was subjected to direct laser irradiation. For the clinical study, preoperative and postoperative photographs were evaluated by 6 surgeons on a 10-point Likert scale. RESULTS Optical coherence tomography demonstrated that laser irradiation of bovine tissue to a temperature range of 60°C to 80°C resulted in an increase in thickness of up to 2-fold. There were no complications or adverse cosmetic outcomes in the patient study. Patient satisfaction with the results of surgery averaged 7 on a 10-point Likert scale. For 3 patients, 3 (50%) of the evaluators believed there was a mild improvement in appearance of the lower eyelids after surgery. The remaining patients were thought to have no significant changes. CONCLUSIONS AND

  19. A tunable mid-infrared laser source for remote sensing

    NASA Technical Reports Server (NTRS)

    Barnes, Norman P.

    1991-01-01

    Many remote sensing needs can be effectively addressed with a tunable laser source in the mid infrared. One potential laser source is an optical parametric oscillator and amplifier system pumped by a near infrared solid state laser. Advantages of such a system and progress made at NASA Langley Research Center to date on such a system are described.

  20. 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.

  1. Infrared laser and Fourier transform spectroscopy of CCH: A highly excited bending vibration of the X ˜ 2Σ+ state and unique Renner-Teller levels of the A ˜ 2 Π state

    NASA Astrophysics Data System (ADS)

    Tokaryk, D. W.; Vervloet, M.; Phi, Tân-Trào

    2015-04-01

    New infrared bands of the linear carbon chain radical CCH are reported: X ˜ (0140 0)2Σ+ - X ˜ (000 0)2Σ+, recorded with a near-infrared diode laser spectrometer, and A ˜ (0 1 0) 22 Δ - X ˜ (011 0)2 Π, A ˜ (0 2 0) 32 Φ - X ˜ (022 0)2 Δ and A ˜ (0 3 0) 42 Γ - X ˜ (033 0)2 Φ, recorded in emission with a Fourier transform spectrometer. All of the upper levels in the transitions appear to be strongly affected by interactions with other levels. The data demonstrate the excellence of calculations by Tarroni and Carter (2003), which determine the upper state level positions, spin-orbit splitting A, and rotational parameter B to a remarkable level of accuracy, considering the very complex nature of the interactions between the X ˜ 2Σ+ and A ˜ 2 Π electronic states in the regions spanned by the observed levels.

  2. 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.

  3. 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

  4. 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.

  5. 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.

  6. New solid state lasers from the ultraviolet to the mid-infrared

    SciTech Connect

    Payne, S.A.; Krupke, W.F.; Beach, R.J.

    1995-08-15

    The authors discuss three new laser materials that offer improved access to the ultraviolet, near infrared and mid-infrared spectral regions. In order for each of these materials to have been identified, a particular hurdle needed to be overcome with respect to the fundamental laser physics impacting the material. In the case of the 280-320nm Ce:LiSAF laser, the main issue is the need to reduce the loss associated with excited state absorption, while for 1047nm Yb:S-FAP it is the ground state absorption at the laser wavelength that must be minimized. Cr:ZnSe has been down-selected from a number of potential candidates which could lase in the 2200-3000nm region, in order to mitigate the detrimental impact of nonradiative decay. In all three cases the authors discuss how appropriate consideration of fundamental concerns has led to the identification and understanding of the new laser system.

  7. 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.

  8. Excitability in semiconductor microring lasers: Experimental and theoretical pulse characterization

    SciTech Connect

    Gelens, L.; Coomans, W.; Van der Sande, G.; Verschaffelt, G.; Mashal, L.; Beri, S.; Danckaert, J.

    2010-12-15

    We characterize the operation of semiconductor microring lasers in an excitable regime. Our experiments reveal a statistical distribution of the characteristics of noise-triggered optical pulses that is not observed in other excitable systems. In particular, an inverse correlation exists between the pulse amplitude and duration. Numerical simulations and an interpretation in an asymptotic phase space confirm and explain these experimentally observed pulse characteristics.

  9. Upconversion luminescence of Ca1-x Ho x F2+x and Sr0.98-x Er0.02Ho x F2.02+x powders upon excitation by an infrared laser

    NASA Astrophysics Data System (ADS)

    Lyapin, A. A.; Kuznetsov, S. V.; Ryabochkina, P. A.; Merculov, A. P.; Chernov, M. V.; Ermakova, Yu A.; Luginina, A. A.; Fedorov, P. P.

    2017-07-01

    Fluorite-type Ca1-x Ho x F2+x and Sr0.98-x Er0.02Ho x F2.02+x powders were synthesized using the co-precipitation from water solution technique. The upconversion luminescence of Ca1-x Ho x F2+x and Sr0.98-x Er0.02Ho x F2.02+x powders in the visible spectral region upon excitation of 5I7 level Ho3+ ions and 4I13/2 level Er3+ ions were studied for the first time. The possibility of visualizing near IR laser radiation using Ca1-x Ho x F2+x and Sr0.98-x Er0.02Ho x F2.02+x powders is proposed. Optimal compositions of Ca1-x Ho x F2+x and Sr0.98-x Er0.02Ho x F2.02+x powders for application as visualizers are discussed.

  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. 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.

  13. 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)

  14. 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.

  15. Unidirectionality of an optically pumped far infrared ring laser

    NASA Astrophysics Data System (ADS)

    Matsushima, Kyoji; Higashida, Noriyoshi; Sokabe, Noburu; Ariyasu, Tomio

    1995-02-01

    An experimental and theoretical investigation has been made on the unidirectional operation of an optically pumped far infrared ring laser. A ring laser operating on the 119 μm line of CH 3OH experiences reversal of output direction in either case of (a) the pump frequency being tuned across the line center of the infrared pump transition or (b) the fir cavity being tuned across the far infrared line center. A model based on two-mode laser theory predicts the output directionality of the optically pumped fir ring laser.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. Collisional effects after selective laser excitation of polyatomic molecules

    NASA Astrophysics Data System (ADS)

    Zalesskaya, G. A.; Yakovlev, D. L.; Sambor, E. G.

    2003-09-01

    Application of multistep schemes for excitation of polyatomic molecules makes it possible to improve bond-selected excitation with light. Fast collisional energy transfer is one of the most important processes that hinder bond-selected reactions. Collisional effects after multistep laser excitation of molecules is an active area of research at present time because of both the little studied characteristics of relaxation processes for polyatomic molecules in vibrational quasi-continuum and possible practical applications. In this report, the intensities and decay rates of the time-resolved delayed fluorescence (DF) activated by several ways of multistep laser excitation of complex organic molecules (acetophenone, benzophenone, anthraquinone, fluorenone) were used to study collisional processes after nonequilbirium vibrational excitation of triplet molecules mixed with bath gases N2, CO2, NH3, H2O, C2H2, CCl4, C6H6, C5H12, many of which participate in important chemical and photochemical organic molecules transformations that occur in nature. The quantitative characteristics of collisional processes in vibrational quasicontinuum were obtained. Analysis was made of rate constant dependences for near-resonant vibration-vibration (V-V) and vibration-translation (V-T) energy transfer processes on such factors as: properties of excited molecules and bath gases; vibrational energy of excited molecules; temperature, etc. Conclusions were made that collisional efficiencies of V-V process in mixture with polyatomic bath gases were governed by long-range attractive interactions. Upper levels, initially populated following laser excitation relaxed to vibrational distribution after several collisions. Majority of the collision took place only in V-T transfer of relatively small energies. The regularities of this process reflected the dominant role of short-range repulsive forces.

  1. 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.

  2. Tunable diode lasers for 3-30 micron infrared operation

    NASA Technical Reports Server (NTRS)

    Linden, K. J.

    1983-01-01

    The tunable diode laser is now widely used in high resolution infrared spectroscopy studies, taking into account laboratory and industrial applications. The present investigation is concerned with advances related to laser performance and reliability. The advances are the result of improvements in materials and device technologies. Reliability data for broad-area Pb(1-x)Sn(x)Se lasers are considered along with performance improvements in stripe-geometry lasers, laser performance at wavelengths above 25 microns, and laser performance at wavelengths below 4 microns. Attention is given to tunable Pb-salt infrared diode lasers, mesa-stripe geometry lasers of Pb(1-x)Sn(x)Se and PbS(1-x)Se(x), and long wavelength diode laser emission observed in both Pb(1-x)Sn(x)Te and Pb(1-x)Sn(x)Se.

  3. 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.

  4. 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.

  5. 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.

  6. Suppression of excited-state absorption in laser crystals

    NASA Astrophysics Data System (ADS)

    Kuznetsova, Elena; Kolesov, Roman; Kocharovskaya, Olga

    2004-10-01

    Currently, a lot of experimental effort in solid-state optics is devoted to searching for laser materials suitable for tunable lasing, primarily in UV and VUV spectral regions. Researchers mainly focus on optical crystals doped with either transition metal or rare-earth ions. The latter ones doped into wide bandgap dielectric crystals have spectrally broad vibronic emission bands associated with 4fn-15d â" 4fn interconfigurational transitions, whose energies lie mostly in UV and VUV regions of the spectrum. The transitions are electric-dipole-allowed, therefore have large absorption and emission cross-sections, and are promising for efficient tunable laser action. However, in almost all promising crystals laser action in UV and VUV is hindered or completely prohibited due to excited-state absorption (ESA), i.e. absorption from metastable laser levels to higher-energy states, which occurs at emission or/and pump wavelengths. A method of suppression of losses due to excited-state absorption (ESA) in laser crystals is proposed, based on a well-known phenomenon of electromagnetically induced transparency (EIT). Absorption from a populated excited electronic state can be reduced under the action of an additional driving coherent field, resonantly coupling the terminal state of ESA to some intermediate discrete state.

  7. 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.

  8. 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.

  9. 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.

  10. Theoretical Modeling of - and Infrared - High-Pressure Gas Lasers with Application to the Xenon Chloride Laser

    NASA Astrophysics Data System (ADS)

    Ishihara, Toshihiko

    Theoretical modeling of microwave- and infrared -pumped high-pressure gas lasers is presented. The theoretical model consists of the time-averaged Boltzmann equation to calculate the electron velocity distribution function under the influence of an alternating electric field, a set of first-order ordinary differential equations to calculate the temporal evolution of the laser plasma, the laser photon balance equation to calculate the instantaneous laser output power, and the time history of the strength of the pumping power. The first law of thermodynamics is employed to determine the root-mean-square strength of the electric field acting on the laser plasma tube by matching the input power and the absorbed power. The theoretical model assumes that the chemical species are homogeneously distributed in an excited plasma and that the laser photons are uniformly distributed inside an optical cavity. Any adverse effects of the plasma tube wall are ignored to simplify the analysis. The theoretical modeling is numerically applied to a microwave-pumped XeCl laser pumped by a 915 MHz microwave of 450 nsec pulse duration. The calculated laser pulse is in fair agreement with the experimentally observed laser pulse. The plasma tube wall is considered to have a significant effect on the performance of the laser when the surface to volume ratio of the plasma tube is large. A parametric study of the microwave-pumped He -base XeCl laser is numerically done using the theoretical model. Among all the calculations done, the gas mixture of He/Xe/HCI = 1000/10/1.3 gives the best performance at the total pressure of 3.5 atm. The result is in good agreement with experimental observation. The theoretical modeling is extended to the infrared -pumped high-pressure XeCl laser. The laser plasma can be heated to a higher electron number density by the infrared beam than by the microwave. This fact may help the production of the laser upper-state molecules which are formed via the electron

  11. 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.

  12. Electronically Excited C2 from Laser Photodissociated C60

    NASA Technical Reports Server (NTRS)

    Arepalli, Sivaram; Scott, Carl D.; Nikolaev, Pavel; Smalley, Richard E.

    1999-01-01

    Spectral and transient emission measurements are made of radiation from products of laser excitation of buckminsterfullerene (C60) vapor diluted in argon at 973 K. The principal radiation is from the Swan band system of C2 and, at early times, also from a black body continuum. The C2 radiation is observed only when C60 is excited by green (532 nm) and not with IR (1064 nm) laser radiation at energy densities of about 1.5 J/square cm. Transient measurements indicate that there are two characteristic periods of decay of radiation. The first period, lasting about 2 micro seconds, has a characteristic decay time of about 0.3 micro seconds. The second period, lasting at least 50 micro seconds, has a characteristic decay time of about 5 micro seconds. These characteristic times are thought to be associated with cooling of C60 molecules or nanosized carbon particles during the early period; and with electronically excited C2 that is a decomposition product of laser excited C60, C58, ... molecules during the later period.

  13. 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.

  14. 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.

  15. 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

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. Synthesis Of Materials With Infrared And Ultraviolet Lasers

    NASA Astrophysics Data System (ADS)

    Lyman, John L.

    1989-05-01

    This paper discusses three divergent examples of synthesis of materials with lasers. The three techniques are: (1) Infrared (CO2) laser synthesis of silane (SiH4) from disilane (Si2H6); (2) Excimer (ArF) laser production of fine silicon powders from methyl-and chlorosubstituted silanes; and, (3) Excimer (KrF) laser production of fine metallic powders by laser ablation. The mechanism for each process is discussed along with some conclusions about the features of the laser radiation that enable each application.

  1. Synthesis of materials with infrared and ultraviolet lasers

    NASA Astrophysics Data System (ADS)

    Lyman, John L.

    This paper discusses three divergent examples of synthesis of materials with lasers. The three techniques are: (1) infrared (CO2) laser synthesis of silane (SiH4) from disilane (Si2H6); (2) excimer (ArF) laser production of fine silicon powders from methly- and chloro-substituted silanes; and (3) exciver (KrF) laser production of fine metallic powders by laser ablation. The mechanism for each process is discussed along with some conclusins about the features of the laser radiation that enable each application.

  2. 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.

  3. 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.

  4. Cutaneous melanin exhibiting fluorescence emission under near-infrared light excitation.

    PubMed

    Huang, Zhiwei; Zeng, Haishan; Hamzavi, Iltefat; Alajlan, Abdulmajeed; Tan, Eileen; McLean, David I; Lui, Harvey

    2006-01-01

    Under ultraviolet and visible light excitation, melanin is essentially a nonfluorescent substance. This work reports our study on near-infrared (NIR) fluorescence properties of melanins, and explores potential applications of NIR fluorescence techniques for evaluating skin disorders involving melanin. The NIR fluorescence spectrum is obtained using a fiber optic NIR spectrometer under 785-nm laser excitation. In vitro measurements are performed on synthetic dihydroxyphenylalanine (DOPA) melanin, melanin extracted from Sepia ink sacs, human hair, animal fur, and bird feathers. Paired spectral comparisons of white and black skin appendages show that melanization of hair, fur, or feathers more than doubles the NIR fluorescence. In vivo NIR autofluorescence of normal dorsal and volar forearm skin of 52 volunteers is measured. Dorsal forearm skin, which is darker than volar skin, exhibits significantly greater NIR fluorescence. Patients with vitiligo (n=4), compound nevus (n=3), nevus of Ota (n=1), superficial spreading melanoma (n=3), and postinflammatory hyperpigmentation (n=1) are also evaluated. NIR fluorescence is greater within the lesion than the surrounding normal skin for all these conditions except vitiligo, where the converse was true. The observed melanin NIR fluorescence provides a new approach to in vitro and in vivo melanin detection and quantification that may be particularly useful for evaluating pigmented skin lesions.

  5. Infrared presensitization photography at deuterium fluoride laser wavelengths

    SciTech Connect

    Geary, J.M.; Ross, K.; Suter, K. )

    1989-09-01

    Near-field irradiance distributions of a deuterium flouride laser system are obtained using infrared presensitization photography. This represents the shortest wavelength region to employ this technique thus far.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. Infrared laser in the treatment of craniomandibular disorders, arthrogenous pain

    SciTech Connect

    Hansson, T.L.

    1989-05-01

    The fast removal of intra-articular inflammation of the temporomandibular joint in five different patients after infrared laser application is described. Parameters of clinical evaluation was maximum mouth opening and subjective pain. The application of infrared laser of 700 Hz frequency for 3 minutes during five consecutive days at the skin over the painful area of the temporomandibular joint was used. However, the importance of concomitant mandibular stabilization is stressed to achieve optimal result.

  12. 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)

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. Indirect absorption spectroscopy using quantum cascade lasers: mid-infrared refractometry and photothermal spectroscopy.

    PubMed

    Pfeifer, Marcel; Ruf, Alexander; Fischer, Peer

    2013-11-04

    We record vibrational spectra with two indirect schemes that depend on the real part of the index of refraction: mid-infrared refractometry and photothermal spectroscopy. In the former, a quantum cascade laser (QCL) spot is imaged to determine the angles of total internal reflection, which yields the absorption line via a beam profile analysis. In the photothermal measurements, a tunable QCL excites vibrational resonances of a molecular monolayer, which heats the surrounding medium and changes its refractive index. This is observed with a probe laser in the visible. Sub-monolayer sensitivities are demonstrated.

  19. 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

  20. Reduced Auger Recombination in Mid-Infrared Semiconductor Lasers (POSTPRINT)

    DTIC Science & Technology

    2013-02-01

    overcome for successful system adoption. Within the last 15 years, quantum cascade lasers ( QCLs ) have proven to be a very capable semiconductor laser...restricted at the longer wavelengths, compared to QCLs due to band filling.9 In the short-wave and mid-wave infrared wavelengths, their low T0

  1. 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.

  2. 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. .

  3. Femtosecond laser excitation of coherent optical phonons in ferroelectric LuMnO3

    NASA Astrophysics Data System (ADS)

    Lou, Shi-Tao; Zimmermann, Frank M.; Bartynski, Robert A.; Hur, Namjung; Cheong, Sang-Wook

    2009-06-01

    We have used femtosecond pump-probe spectroscopy to excite and probe coherent optical phonon vibrations in single crystals of hexagonal ferroelectric LuMnO3 . An optical phonon mode of A1 symmetry was coherently excited with 25 fs pump-laser pulses (λ≈800nm) . The phonon mode, involving Lu ion motion along the c axis, was identified as the soft mode driving the ferroelectric transition. The excitation mechanism was determined to be purely displacive in nature due to resonant excitation of a narrow intra-atomic dxy,x2-y2→d3z2-r2 transition in Mn. The lifetime of the Mndxy,x2-y2→d3z2-r2 excitation was measured to be 0.8 ps. A remarkable reversal of the sign of the oscillation amplitude ( π phase shift) of the reflectivity curve was observed upon comparing longitudinal-optical (LO) with transverse-optical (TO) mode geometries. The phase reversal is attributed to the macroscopic electric depolarization field accompanying infrared-active longitudinal phonon modes but absent in TO modes. In addition to the direct effect of the ion motion on the optical properties, which is the same in LO and TO modes, the longitudinal depolarization field of the LO mode gives rise to an additional modulation of the refractive index via the linear electro-optic effect which dominates the optical response.

  4. 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.

  5. 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.

  6. Laser-induced filaments in the mid-infrared

    NASA Astrophysics Data System (ADS)

    Zheltikov, A. M.

    2017-05-01

    Laser-induced filamentation in the mid-infrared gives rise to unique regimes of nonlinear wave dynamics and reveals in many ways unusual nonlinear-optical properties of materials in this frequency range. The λ 2 scaling of the self-focusing threshold P cr, with radiation wavelength λ, allows the laser powers transmitted by single mid-IR filaments to be drastically increased without the loss of beam continuity and spatial coherence. When extended to the mid-infrared, laser filamentation enables new methods of pulse compression. Often working around the universal physical limitations, it helps generate few-cycle and subcycle field waveforms within an extraordinarily broad range of peak powers, from just a few up to hundreds of P cr. As a part of a bigger picture, laser-induced filamentation in the mid-infrared offers important physical insights into the general properties of the nonlinear-optical response of matter as a function of the wavelength. Unlike their near-infrared counterparts, which can be accurately described within the framework of perturbative nonlinear optics, mid-infrared filaments often entangle perturbative and nonperturbative nonlinear-optical effects, showing clear signatures of strong-field optical physics. With the role of nonperturbative nonlinear-optical phenomena growing, as a general tendency, with the field intensity and the driver wavelength, extension of laser filamentation to even longer driver wavelengths, toward the long-wavelength infrared, promises a hic sunt dracones land.

  7. 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

  8. 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.

  9. Laser Guiding and Wakefield Excitation in Plasma Channels.

    NASA Astrophysics Data System (ADS)

    Volfbeyn, Paul

    1998-11-01

    Laser driven plasma waves have been experimentally shown to sustain electric field gradients in excess of 10 GV/m. (For a review see E. Esarey et al., IEEE Trans. Plasma Sci. PS-24), 252 (1996). Laser diffraction limits the distance over which the high gradients are excited, thus placing a severe limit on the energy gain achievable in a laser plasma accelerating stage. To overcome the limitation on the acceleration distance due to laser beam diffraction, plasma channel guiding has been proposed in which, plasma channels with density minimum on axis can serve as optical guides. An overview is given of various techniques for plasma channel creation, relying on hydrodynamic shock expansion in laser heated plasmas (C.G. Durfee III and H. M. Milchberg, Phys. Rev. Lett., vol. 71, pp. 2409, (1993).) and capillary discharges. ( Y. Ehrlich, et al. Phys. Rev. Lett., vol.77, (no.20), p.4186-9 (1996).) Details of the dual laser pulse Ignitor - Heater scheme (P. Volfbeyn and W. P. Leemans, Phys. Rev. Lett., to be submitted.) will be presented, which allows creation of plasma channels in low atomic number gases, such as hydrogen. The current status of experiments on characterization of the plasma channel density profile and guiding of high intensity laser pulses will then be reviewed. These measurements are important since the density profile of plasma channels defines the modes of plasma oscillations and, therefore both the transverse (focusing) and longitudinal (accelerating) properties of the wake modes. Results of theoretical calculations of the wake modes for various plasma channel density profiles are presented, and their significance for the laser-plasma accelerator design is discussed.

  10. Development of a higher power fission-fragment-excited CO laser

    NASA Technical Reports Server (NTRS)

    Mcarthur, D. A.

    1976-01-01

    Moderate dilution of the CO with Ar lowers the reactor excitation threshold for lasing. Fission coatings on ceramic substrates have been developed which minimize fouling of laser mirrors. A new laser apparatus was constructed which more closely resembles large electrically excited CO lasers. Measurements of the energy emerging from the foils indicate that excitation of the gas is still below optimum values. Laser action at room temperature has also been observed.

  11. Optimal repetition rates of excitation pulses in a Tm-vapour laser

    SciTech Connect

    Gerasimov, V A; Gerasimov, V V; Pavlinskii, A V

    2011-01-31

    The optimal excitation pulse repetition rates (PRRs) for a gas-discharge Tm-vapour laser with indirect population of upper laser levels are determined. It is shown that, under the same excitation conditions, the optimal PRRs increase with a decrease in the energy defect between the upper laser acceptor level and the nearest resonant donor level. The reasons for the limitation of the optimal PRRs in Tm-vapour laser are discussed. It is shown that the maximum average power of Tm-vapour laser radiation may exceed several times the Cu-vapour laser power under the same excitation conditions and in identical gas-discharge tubes. (lasers)

  12. Advanced quantum cascade laser transmitter architectures and infrared photonics development

    SciTech Connect

    Anheier, Norman C.; Allen, Paul J.; Myers, Tanya L.

    2004-08-01

    Quantum cascade lasers (QCLs) provide a viable infrared laser source for a new class of laser transmitters capable of meeting the performance requirements for a variety of national security and civilian applications. The high output power, small size, and superb stability and modulation characteristics of QCLs make them amenable for integration as transmitters into ultra-sensitive, ultra-selective point sampling and remote short-range chemical sensors. This paper reports on the current development in infrared photonics that provides a pathway for QCL transmitter miniaturization. This research has produced infrared waveguide-based optical components in chalcogenide glass using both direct-laser writing and holographic exposure techniques. We discuss here the design and fabrication concepts and capabilities required to produce integrated waveguides, waveguide couplers, and other photonic devices.

  13. Stark effect applicable to optically pumped far-infrared laser

    NASA Technical Reports Server (NTRS)

    Claspy, P. C.; Koo, K. P.

    1976-01-01

    Absorption measurements at CO2 laser frequencies were carried out as a function of Stark fields and CH3OH gas pressures to assess the effect of low electric field Stark tuning on methanol absorption at the P(12) 9.4 micron CO2 laser line, in a continuing search for coherent emitters at submillimeter wavelengths (far infrared). The line center absorption coefficient is found to increase five-fold with a 2.3 kV/cm Stark field at the 220 mtorr methanol pressure optimal for methanol far infrared lasing. The low electric field Stark tuning encourages efforts to enhance the pumping efficiency of a methanol far infrared laser at its normal optimum operating pressure, and suggests that significant Stark field induced frequency modulation of the far IR laser output is feasible.

  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. Microwave excitation of a XeCl laser without preionization

    NASA Astrophysics Data System (ADS)

    Klingenberg, Hans H.; Gekat, Frank; Spindler, Gerhard

    1990-08-01

    Microwave discharges have been used to excite rare gas halide mixtures like XeC1. For the realization of microwave excited excimer lasers a minimum specific pump power density of 100 kW/cxn3 is needed. The resulting power requirements are of the order of one to ten mega- watts. This power has to be deposited in a discharge tube which is housed in a hollow waveguide. For these purposes, a WR-650 waveguide circuit was assembled. The pulsed microwave source was a magnetron transmitter with a frequency of 1.35 GHz, a pulsed power of 2.5 MW and a pulse length of 4 jis. The puise repetition frequency was 10 Hz. A double ridge waveguide coupling structure was designed using the cornputer code URMEL-T. This program is based on a finite difference discretization method for the Maxwell field equations to compute electromagnetic fields in waveguides and cavities. The laser gas mixture consisted of He/Xe/HC1 = 1000/1/0.2 at a total pressure of 1000 mbar. A laser pulse energy of 20 pJ with a pulse width of 65 ns (FWHM) was measured yielding a peak power of 300 W.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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).

  4. Atmospheric Laser and Infrared Transmission Model

    DTIC Science & Technology

    2009-01-01

    mature high energy solid state laser technol- ogy is flashlamp- pumped 1.06 μ neodymium/glass (Nd:glass), however, diode pumping , and alternative lasing...field will have relatively simple characteristics, such as those of the TEM00 mode. But some features of high-power lasers militate against this. In...a transverse -flow gas laser , upstream depletion of the inversion may destroy axial symmetry of the output. Support structures for optics may block

  5. 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.

  6. Mid-infrared solid-state lasers and laser materials

    NASA Technical Reports Server (NTRS)

    Barnes, Norman P.; Byvik, Charles E.

    1988-01-01

    An account is given of NASA-Langley's objectives for the development of advanced lasers and laser materials systems applicable to remote sensing in the mid-IR range. Prominent among current concerns are fiber-optic spectroscopy, eye-safe solid-state lasers for both Doppler sensing and mid-IR wavelength-generation laser pumping, and nonlinear optics generating tunable mid-IR radiation. Ho:YAG lasers are noted to exhibit intrinsic advantages for the desired applications, and are pumpable by GaAlAs laser diodes with a quantum efficiency approaching 2.

  7. Optimal repetition rates of excitation pulses in a Tm-vapour laser

    NASA Astrophysics Data System (ADS)

    Gerasimov, V. A.; Gerasimov, V. V.; Pavlinskii, A. V.

    2011-01-01

    The optimal excitation pulse repetition rates (PRRs) for a gas-discharge Tm-vapour laser with indirect population of upper laser levels are determined. It is shown that, under the same excitation conditions, the optimal PRRs increase with a decrease in the energy defect between the upper laser acceptor level and the nearest resonant donor level. The reasons for the limitation of the optimal PRRs in Tm-vapour laser are discussed. It is shown that the maximum average power of Tm-vapour laser radiation may exceed several times the Cu-vapour laser power under the same excitation conditions and in identical gas-discharge tubes.

  8. 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)

  9. 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].

  10. Low-cost laser scanning photoacoustic microscopy system with a pulsed laser diode excitation source

    NASA Astrophysics Data System (ADS)

    Erfanzadeh, Mohsen; Zhu, Quing

    2017-03-01

    We present a low-cost laser scanning photoacoustic microscopy system with a pulsed laser diode as the excitation source. The system utilizes a 905 nm pulsed laser diode with 120 ns pulse width and 1 KHz repetition rate. No averaging is performed in data acquisition, resulting in a short image acquisition time. The maximum field of view is 4.6 mm × 3.7 mm and the lateral resolution is 71 μm. Images of human hairs and mouse ear are presented to demonstrate the feasibility of the system in imaging biological tissue.

  11. 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.

  12. 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.

  13. 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

  14. 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.

  15. 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.

  16. 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.

  17. Mid- infrared semiconductor laser based trace gas sensor technologies for environmental monitoring and industrial process control

    NASA Astrophysics Data System (ADS)

    Lewicki, Rafał; Jahjah, Mohammad; Ma, Yufei; Tittel, Frank K.; Stefanski, Przemyslaw; Tarka, Jan

    2013-01-01

    Recent advances in the development of compact sensors based on mid-infrared continuous wave (CW), thermoelectrically cooled (TEC) and room temperature operated quantum cascade lasers (QCLs) for the detection, quantification and monitoring of trace gas species and their applications in environmental and industrial process analysis will be reported. These sensors employ a 2f wavelength modulation (WM) technique based on quartz enhanced photoacoustic spectroscopy (QEPAS) that achieves detection sensitivity at the ppb and sub ppb concentration levels. The merits of QEPAS include an ultra-compact, rugged sensing module, with wide dynamic range and immunity to environmental acoustic noise. QCLs are convenient QEPAS excitation sources that permit the targeting of strong fundamental rotational-vibrational transitions which are one to two orders of magnitude more intense in the mid-infrared than overtone transitions in the near infrared spectral region.

  18. 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.

  19. Infrared spectroscopy of excited states and transients in photochemistry

    NASA Astrophysics Data System (ADS)

    Schaffner, Kurt; Grevels, Friedrich-Wilhelm

    Flash photolysis with time-resolved IR detection is used in investigations of the primary photoreactions of chromium, molybdenum, tungsten, manganese, iron, and osmium carbonyl complexes, and of the ensuing transformations of transient products in room temperature solution. The method bridges the gap to spectral data obtained at low temperatures. It provides information which has previously been inaccessible, such as detailed structural information, and kinetic data in cases where the UV-visible absorptions of the species of interest overlap. Finally, excited-state IR spectroscopy has now become feasible for many organic compounds with the most recent instrumental set-up which reaches a time resolution of ≥ 50 ns.

  20. Mid-infrared high-power diode lasers and modules

    NASA Astrophysics Data System (ADS)

    Kelemen, Márc T.; Gilly, Juergen; Rattunde, Marcel; Wagner, Joachim; Ahlert, Sandra; Biesenbach, Jens

    2010-02-01

    High-power diode lasers in the mid-infrared wavelength range between 1.8μm and 2.3μm have emerged new possibilities for applications like processing and accelerated drying of materials, medical surgery, infrared countermeasures or for pumping of solid-state and semiconductor disc lasers. We will present results on MBE grown (AlGaIn)(AsSb) quantum-well diode laser single emitters with emitter widths between 90μm and 200μm. In addition laser bars with 20% or 30% fill factor have been processed. More than 30% maximum wall-plug efficiency in cw operation for single emitters and laser bars has been reached. Even at 2200nm more than 15W have been demonstrated with a 30% fill factor bar. Due to an increasing interest in pulsed operation modes for these mid-infrared lasers, we have investigated single emitters and laser bars at 1940nm for different pulse times and duty cycles. More than 9W have been measured at 30A with 500ns pulse time and 1% duty cycle without COMD for a single emitter. Most applications mentioned before need fiber coupled output power, therefore fiber coupled modules based on single emitters or laser bars have been developed. Single-emitter based modules show 600mW out of a 200μm core fiber with NA=0.22 at different wavelengths between 1870nm and 1940nm. At 2200nm an output power of 450mW ex fiber impressively demonstrates the potential of GaSb based diode lasers well beyond wavelengths of 2μm. Combining several laser bars, 20W out of a 600μm core fiber have been established at 1870nm. Finally for a 7 bar stack at 1870nm we have demonstrated more than 85W at 50A in qcw mode.

  1. 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.

  2. 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.

  3. Polycarbonate resin drilling by longitudinally excited CO2 laser

    NASA Astrophysics Data System (ADS)

    Uno, Kazuyuki; Kato, Masaya; Akitsu, Tetsuya; Jitsuno, Takahisa

    2017-02-01

    We developed a longitudinally excited CO2 laser with a long external cavity and investigated the drilling characteristics of polycarbonate resin. The CO2 laser was very simple and consisted of a 45-cm-long alumina ceramic pipe with an inner diameter of 13 mm, a pulse power supply, a step-up transformer, a storage capacitance, and a long external optical cavity with a cavity length of 175 cm and an aperture of 9 mm. The CO2 laser produced a short pulse that had a spike pulse with the width of 282 ns and the energy of 0.45 mJ, a pulse tail with the length of 66.9 μs and the energy of 15.65 mJ, and a good circular beam. In a processing system, a ZnSe focusing lens with the focal length of 50 mm was used and the location of the focal plane was that of the sample surface. In the drilling of polycarbonate resin by the CO2 laser, the drilling characteristics depended on the number of pulses and the fluence was investigated. Clear drilling without carbonization was produced by the irradiation of 50 pulses or less with the fluence of 19 J/cm2 and the irradiation of 100 pulses or less with the fluence of 8 J/cm2. The clear drilling with the deepest depth in this work was 403 μm at the 50 pulses irradiation with the fluence of 19 J/cm2. The number of pulses and the fluence can control thermal influence in the CO2 laser processing of polycarbonate resin.

  4. Low intensity infrared laser induces filamentation in Escherichia coli cells

    NASA Astrophysics Data System (ADS)

    Fonseca, A. S.; Presta, G. A.; Geller, M.; Paoli, F.

    2011-10-01

    Low intensity continuous wave and pulsed emission modes laser is used in treating many diseases and the resulting biostimulative effect on tissues has been described, yet the photobiological basis is not well understood. The aim of this wok was to evaluate, using bacterial filamentation assay, effects of laser on Escherichia coli cultures in exponential and stationary growth phase. E. coli cultures, proficient and deficient on DNA repair, in exponential and stationary growth phase, were exposed to low intensity infrared laser, aliquots were spread onto microscopic slides, stained by Gram method, visualized by optical microscopy, photographed and percentage of bacterial filamentation were determined. Low intensity infrared laser with therapeutic fluencies and different emission modes can induce bacterial filamentation in cultures of E. coli wild type, fpg/ mutM, endonuclease III and exonuclease III mutants in exponential and stationary growth phase. This study showed induction of bacterial, filamentation in E. coli cultures expose to low intensity infrared laser and attention to laser therapy protocols, which should take into account fluencies, wavelengths, tissue conditions, and genetic characteristics of cells before beginning treatment.

  5. 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.

  6. 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

  7. 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.

  8. Advanced nanoparticle generation and excitation by lasers in liquids.

    PubMed

    Barcikowski, Stephan; Compagnini, Giuseppe

    2013-03-07

    Today, nanoparticles are widely implemented as functional elements onto surfaces, into volumes and as nano-hybrids, resulting for example in bioactive composites and biomolecule conjugates. However, only limited varieties of materials compatible for integration into advanced functional materials are available: nanoparticles synthesized using conventional gas phase processes are often agglomerated into micro powders that are hard to re-disperse into functional matrices. Chemical synthesis methods often lead to impurities of the nanoparticle colloids caused by additives and precursor reaction products. In the last decade, laser ablation and nanoparticle generation in liquids has proven to be a unique and efficient technique to generate, excite, fragment, and conjugate a large variety of nanostructures in a scalable and clean manner. This editorial briefly highlights selected recent advancements and critical aspects in the field of pulsed laser-based nanoparticle generation and manipulation, including exemplary strategies to harvest the unique properties of the laser-generated nanomaterials in the field of biomedicine and catalysis. The presented critical aspects address future assignments such as size control and scale-up.

  9. The mid-infrared swept laser: life beyond OCT?

    NASA Astrophysics Data System (ADS)

    Childs, D. T. D.; Hogg, R. A.; Revin, D. G.; Rehman, I. U.; Cockburn, J. W.; Matcher, S. J.

    2015-03-01

    Near-infrared external cavity lasers with high tuning rates ("swept lasers") have come to dominate the field of nearinfrared low-coherence imaging of biological tissues. Compared with time-domain OCT, swept-source OCT a) replaces slow mechanical scanning of a bulky reference mirror with much faster tuning of a laser cavity filter element and b) provides a ×N (N being the number of axial pixels per A-scan) speed advantage with no loss of SNR. We will argue that this striking speed advantage has not yet been fully exploited within biophotonics but will next make its effects felt in the mid-infrared. This transformation is likely to be driven by recent advances in external cavity quantum cascade lasers, which are the mid-IR counterpart to the OCT swept-source. These mid-IR sources are rapidly emerging in the area of infrared spectroscopy. By noting a direct analogy between time-domain OCT and Fourier Transform Infrared (FTIR) spectroscopy we show analytically and via simulations that the mid-IR swept laser can acquire an infrared spectrum ×N (N being the number of spectral data points) faster than an FTIR instrument, using identical detected flux levels and identical receiver noise. A prototype external cavity mid-IR swept laser is demonstrated, offering a comparatively low sweep rate of 400 Hz over 60 cm-1 with 2 cm-1 linewidth, but which provides evidence that sweep rates of over a 100 kHz should be readily achievable simply by speeding up the cavity tuning element. Translating the knowledge and experience gained in near-IR OCT into mid-IR source development may result in sources offering significant benefits in certain spectroscopic applications.

  10. Far infrared optical excitation in metallic uranium sulfide

    NASA Astrophysics Data System (ADS)

    Schoenes, J.; Brüesch, P.

    1981-04-01

    Previous near normal incidence reflectivity measurements on US single crystals from 12 to 0.03 eV have been extended down to 0.0018 eV (15 cm -1). A broad plateau with a reflectivity of 90±2% is observed between 40 and 400 cm -1 with a further increase of the reflectivity below 40 cm -1. A Kramers-Kronig transformation of the data shows the existence of a resonance at 315 cm -1. From a comparison with recent neutron data and other arguments we deduce that this resonance is due to the excitation of a transverse optical phonon coupled to an f→ d or d→f interband transition.

  11. 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.

  12. 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

  13. Laser-induced temperature-rise measurement by infrared imaging

    NASA Astrophysics Data System (ADS)

    Gu, Jianhui; Tam, Siu Chung; Lam, Yee Loy; Zheng, Qiguang; Wei, Xueqin

    2000-06-01

    The characteristics of laser-induced temperature-rise are important information in laser material processing. In our experiment, several kinds of metals such as mild carbon steel, stainless steel, aluminum alloy and copper, and non-metals namely epoxy and polymethyl methacrylate were irradiated by using a high-power CW CO2 laser beam, while the temperature distribution and variation on their surfaces were measured by using a fast scanning infrared camera to image the laser irradiated area. The CO2 laser beam power was varied from several tens of Watts to several hundreds of Watts for the irradiating of different materials. 2-D and 3-D temperature distributions and the temperature variations against the time of laser irradiation on certain points within the laser-irradiated area were recorded and measured. It is found that the temperature distribution on the surfaces of the irradiated materials was tightly related to the laser beam mode, and the temperature fluctuations corresponded to the laser beam power fluctuations. The results of this research could be applied to laser material processing.

  14. 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.

  15. 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.

  16. 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.

  17. High Power Mid Wave Infrared Semiconductor Lasers

    DTIC Science & Technology

    2006-06-15

    injected MWIR laser arrays using III-V antimonide based materials. In this approach, InGaSb quantum wells are grown on metamorphic layers on a GaSb or GaAs...also demonstrated room temperature photoluminescence up to 3 gm from InGaSb quantum wells grown on GaAs substrate. Using this approach we have...InAsSb/InAlAs quantum well lasers was reported with a To of 26K. Thus typically, the devices require thermoelectric or even cryogenic cooling to operate

  18. 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.

  19. Short infrared laser pulses increase cell membrane fluidity

    NASA Astrophysics Data System (ADS)

    Walsh, Alex J.; Cantu, Jody C.; Ibey, Bennett L.; Beier, Hope T.

    2017-02-01

    Short infrared laser pulses induce a variety of effects in cells and tissues, including neural stimulation and inhibition. However, the mechanism behind these physiological effects is poorly understood. It is known that the fast thermal gradient induced by the infrared light is necessary for these biological effects. Therefore, this study tests the hypothesis that the fast thermal gradient induced in a cell by infrared light exposure causes a change in the membrane fluidity. To test this hypothesis, we used the membrane fluidity dye, di-4-ANEPPDHQ, to investigate membrane fluidity changes following infrared light exposure. Di-4-ANEPPDHQ fluorescence was imaged on a wide-field fluorescence imaging system with dual channel emission detection. The dual channel imaging allowed imaging of emitted fluorescence at wavelengths longer and shorter than 647 nm for ratiometric assessment and computation of a membrane generalized polarization (GP) value. Results in CHO cells show increased membrane fluidity with infrared light pulse exposure and this increased fluidity scales with infrared irradiance. Full recovery of pre-infrared exposure membrane fluidity was observed. Altogether, these results demonstrate that infrared light induces a thermal gradient in cells that changes membrane fluidity.

  20. 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.

  1. 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.

  2. Laser control of molecular excitations in stochastic dissipative media

    NASA Astrophysics Data System (ADS)

    Tremblay, Jean Christophe

    2011-05-01

    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.

  3. 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

  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 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.

  6. 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.

  7. 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

  8. 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.

  9. 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.

  10. Lasing due to the excited state in quantum dot lasers

    NASA Astrophysics Data System (ADS)

    Abusaa, M.; Danckaert, J.; Viktorov, E. A.

    2017-07-01

    Quantum Dot Lasers (QDLs) are promising sources of light because of their favorable properties compared to other light sources. Emission in QDLs can access transitions in ground state (GS) and excited state (ES). Lasing due to the ES extends the spectral range and enables the laser to generate high output powers. Thus, lasing action due to the ES or to the dual lasing regime (GS and ES simultaneously) is expected to increase the applicability of QDLs in many future applications. We present a partially microscopic rate equation model that takes into account lasing action due to both the GS and the ES and distinguishes between both types of carriers (electrons and holes). Also, we present all possible steady-state solutions and we apply a stability analysis to the solutions to determine all stable lasing regimes (lasing due to the GS, lasing due to the ES and the dual lasing regime) to highlight the role of ES transitions. Specifically, we address the appearance of lasing due to the ES to the larger population of the ES and hence to the larger gain in higher injected current regimes.

  11. 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.

  12. Critical evaluation of a handheld Raman spectrometer with near infrared (785nm) excitation for field identification of minerals.

    PubMed

    Jehlička, Jan; Culka, Adam; Vandenabeele, Peter; Edwards, Howell G M

    2011-10-01

    Handheld Raman spectrometers (Ahura First Defender XL, Inspector Raman DeltaNu) permit the recording of acceptable and good quality spectra of a large majority of minerals outdoors and on outcrops. Raman spectra of minerals in the current study were obtained using instruments equipped with 785 nm diode lasers. Repetitive measurements carried out under an identical instrumental setup confirmed the reliability of the tested Raman spectrometers. Raman bands are found at correct wavenumber positions within ±3 cm(-1) compared to reference values in the literature. Taking into account several limitations such as the spatial resolution and problems with metallic and black and green minerals handheld Raman spectrometers equipped with 785 nm diode lasers can be applied successfully for the detection of minerals from the majority of classes of the mineralogical system. For the detection of biomarkers and biomolecules using Raman spectroscopy, e.g. for exobiological applications, the near infrared excitation can be considered as a preferred excitation. Areas of potential applications of the actual instruments include all kind of common geoscience work outdoors. Modified Raman systems can be proposed for studies of superficial or subsurface targets for Mars or Lunar investigations. Copyright © 2011 Elsevier B.V. All rights reserved.

  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. Pulsed Infrared Laser Induced Visible Luminescence.

    DTIC Science & Technology

    1979-01-01

    Tne- Technic~1 ~~~~~~~~ scence ”r~ ——— 6. PERFORMING ORG. REPORT NUMBER _____________ ______UN BE R(a)I~~~~I1 ~~~~I1a~~~~ B...here can produce pressure waves reaching kilobar 1evels)~~ 13 A possibility , then , is one of laser shock induced tribolumine — scence . This could be

  15. Innovative Solid State Infrared Laser Devices

    DTIC Science & Technology

    2010-12-01

    Signature// KENNETH L. SCHEPLER JOHN F. CARR, Chief EO CM Tech Branch EO CM Tech Branch Multispectral Sensing & Detection Division...a flat sapphire70% transmissive output coupler (OC) and a semiconductor saturable absorber mirror ( SESAM ) fabricated by NRL for this experiment...Cr2+:ZnSe laser,” Optics Letters 25: 168-170. (2000). [5] I. T Sorokina, E. Sorokin, and T. J Carrig, “Femtosecond pulse generation from a SESAM

  16. 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.

  17. 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.

  18. Two-laser mid-infrared and ultraviolet matrix-assisted laser desorption/ionization

    NASA Astrophysics Data System (ADS)

    Little, Mark W.; Murray, Kermit K.

    2007-03-01

    Matrix-assisted laser desorption/ionization (MALDI) was performed using two-pulsed lasers with wavelengths in the infrared and ultraviolet regions. A 2.94 [mu]m pulsed optical parametric oscillator laser system and a 337 nm pulsed nitrogen laser irradiated the same spot on the sample target. Sinapinic acid (SA), 2,5-dihydroxybenzoic acid (DHB), [alpha]-cyano-4-hydroxycinnamic acid (CCA), and 4-nitroaniline (NA) were used as matrices, and bovine insulin and cytochrome C were used as analytes. The laser energy was adjusted so that one-laser MALDI and LDI was at a minimum and the matrix and analyte ion signal was enhanced when the two lasers were fired together. Two-laser LDI was observed with SA, DHB, and NA matrices and two-laser MALDI was observed with SA and DHB. Plots of ion signal as a function of delay between the IR and UV lasers show two-laser signal from 0 ns up to a delay of 500 ns when the IR laser is fired before the UV laser. The results are interpreted in terms of IR laser heating of the target that leads to an enhancement in UV LDI and MALDI.

  19. Subsurface thermal coagulation of tissues using near infrared lasers

    NASA Astrophysics Data System (ADS)

    Chang, Chun-Hung Jack

    Noninvasive laser therapy is currently limited primarily to cosmetic dermatological applications such as skin resurfacing, hair removal, tattoo removal and treatment of vascular birthmarks. In order to expand applications of noninvasive laser therapy, deeper optical penetration of laser radiation in tissue as well as more aggressive cooling of the tissue surface is necessary. The near-infrared laser wavelength of 1075 nm was found to be the optimal laser wavelength for creation of deep subsurface thermal lesions in liver tissue, ex vivo, with contact cooling, preserving a surface tissue layer of 2 mm. Monte Carlo light transport, heat transfer, and Arrhenius integral thermal damage simulations were conducted at this wavelength, showing good agreement between experiment and simulations. Building on the initial results, our goal is to develop new noninvasive laser therapies for application in urology, specifically for treatment of female stress urinary incontinence (SUI). Various laser balloon probes including side-firing and diffusing fibers were designed and tested for both transvaginal and transurethral approaches to treatment. The transvaginal approach showed the highest feasibility. To further increase optical penetration depth, various types and concentrations of optical clearing agents were also explored. Three cadavers studies were performed to investigate and demonstrate the feasibility of laser treatment for SUI.

  20. 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.

  1. Near-Infrared Laser Adjuvant for Influenza Vaccine

    PubMed Central

    Kashiwagi, Satoshi; Yuan, Jianping; Forbes, Benjamin; Hibert, Mathew L.; Lee, Eugene L. Q.; Whicher, Laura; Goudie, Calum; Yang, Yuan; Chen, Tao; Edelblute, Beth; Collette, Brian; Edington, Laurel; Trussler, James; Nezivar, Jean; Leblanc, Pierre; Bronson, Roderick; Tsukada, Kosuke; Suematsu, Makoto; Dover, Jeffrey; Brauns, Timothy; Gelfand, Jeffrey; Poznansky, Mark C.

    2013-01-01

    Safe and effective immunologic adjuvants are often essential for vaccines. However, the choice of adjuvant for licensed vaccines is limited, especially for those that are administered intradermally. We show that non-tissue damaging, near-infrared (NIR) laser light given in short exposures to small areas of skin, without the use of additional chemical or biological agents, significantly increases immune responses to intradermal influenza vaccination without augmenting IgE. The NIR laser-adjuvanted vaccine confers increased protection in a murine influenza lethal challenge model as compared to unadjuvanted vaccine. We show that NIR laser treatment induces the expression of specific chemokines in the skin resulting in recruitment and activation of dendritic cells and is safe to use in both mice and humans. The NIR laser adjuvant technology provides a novel, safe, low-cost, simple-to-use, potentially broadly applicable and clinically feasible approach to enhancing vaccine efficacy as an alternative to chemical and biological adjuvants. PMID:24349390

  2. Scanning Laser Infrared Molecular Spectrometer (SLIMS)

    NASA Technical Reports Server (NTRS)

    Scott, David C.; Rickey, Kelly; Ksendzov, Alexander; George, Warren P.; Aljabri, Abdullah S.; Steinkraus, Joel M.

    2012-01-01

    This prototype innovation is a novel design that achieves very long, effective laser path lengths that are able to yield ppb (parts per billion) and sub-ppb measurements of trace gases. SLIMS can also accommodate multiple laser channels covering a wide range of wavelengths, resulting in detection of more chemicals of interest. The mechanical design of the mirror cell allows for the large effective path length within a small footprint. The same design provides a robust structure that lends itself to being immune to some of the alignment challenges that similar cells face. By taking a hollow cylinder and by cutting an elliptically or spherically curved surface into its inner wall, the basic geometry of a reflecting ring is created. If the curved, inner surface is diamond-turned and highly polished, a surface that is very highly reflective can be formed. The surface finish can be further improved by adding a thin chrome or gold film over the surface. This creates a high-quality, curved, mirrored surface. A laser beam, which can be injected from a small bore hole in the wall of the cylinder, will be able to make many low-loss bounces around the ring, creating a large optical path length. The reflecting ring operates on the same principle as the Herriott cell. The difference exists in the mirror that doesn't have to be optically aligned, and which has a relatively large, internal surface area that lends itself to either open air or evacuated spectroscopic measurements. This solid, spherical ring mirror removes the possibility of mirror misalignment caused by thermal expansion or vibrations, because there is only a single, solid reflecting surface. Benefits of the reflecting ring come into play when size constraints reduce the size of the system, especially for space missions in which mass is at a premium.

  3. Infrared Laser and Reaction Rate Study

    DTIC Science & Technology

    1976-02-01

    other isotopes in which plants can be grown. (3) Separation of rare earths Ot and Hf, which may be competitive with other techniques. (4...34«.. Thls ls ha- « .i-PL p^ ■*•"«•> lasers TH ""»bllshed fact fo ^actions nanism of the HF 2 «r + F 2 ^^ + H and produces HP...22, p. 983 (1974). 65. H. R. Fetterman and H. R. Schlossberg, Microwave J., Vol. 17, p. 35 (1974). 66. T. Plant , L. Newman, E. J. Danielewicz, T

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. Thermal lensing from near-infrared laser radiation in an artificial eye

    NASA Astrophysics Data System (ADS)

    Vincelette, Rebecca; Oliver, Jeff; Rockwell, Benjamin; Thomas, Robert; Welch, Ashley J.

    2009-02-01

    A confocal imaging system mounted to a micrometer stage was used to image the thermal lens induced into a water filled Cain-cell artificial eye. A dual-beam pump-probe geometry was used to quantify the 633-nm visible wavelength probe beam's transient response when exposed to the near-infrared pump-beam source. The infrared laser radiation wavelengths tested were 1110, 1130, 1150 and 1318 nm for 1-s exposures to 450-mW of power. Analysis of video data revealed the amount of refractive shift, induced by the thermal lens, as a function of time. Data demonstrate how the formation and dissipation of the thermal lens follow a logarithmic excitation and exponential decay in time respectively. Confocal imaging showed that thermal lensing was strongest for the 1150-nm wavelength followed by 1130, 1318 and 1110-nm.

  10. Note: Infrared laser diagnostics for deuterium gas puff Z pinches

    NASA Astrophysics Data System (ADS)

    Ivanov, V. V.; McKee, E. S.; Hammel, B. D.; Darling, T. W.; Swanson, K. J.; Covington, A. M.

    2017-07-01

    Deuterium gas puff Z pinches have been used for generation of strong neutron fluxes on the MA class pulse power machines. Due to the low electron density of deuterium Z-pinch plasma, regular laser diagnostics in the visible range cannot be used for observation and study of the pinch. Laser probing at the wavelength of 1064 nm was used for visualization of deuterium plasma. Infrared schlieren and interferometry diagnostics showed the deuterium gas puff plasma dynamics, instabilities, and allowed for the reconstruction of the profile of the plasma density.

  11. 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.

  12. Gas laser in which the gas is excited by capacitor discharge

    SciTech Connect

    Lacour, B.; de Witte, O.; Maillet, M.; Vannier, C.

    1985-01-22

    A gas laser in which the gas is excited by laser discharge, said laser including two capacitors formed by two parallel metal plates between which two dielectric parts are spaced apart to form a passage which contains the laser gas. It further includes a transformer whose secondary winding is connected to the plates and whose primary winding is connected in series with a capacitor, means for charging and capacitor and a thyristor for discharging the capacitor in the primary winding. Application to exciting gas lasers in which the gas contains a dye stuff.

  13. Speckle-free near-infrared imaging using a Nd3+ random laser

    NASA Astrophysics Data System (ADS)

    Barredo-Zuriarrain, M.; Iparraguirre, I.; Fernández, J.; Azkargorta, J.; Balda, R.

    2017-10-01

    Single shot infrared images of different patterns obtained, both by reflection and transmission, with a near infrared random laser source and a narrowband laser are analyzed under similar experimental conditions. The Nd-based crystal powder random laser provides speckle-free transmission and reflection infrared images with higher values of contrast to noise ratio than those obtained with the narrowband laser. These results open up new possibilities to enhance the field of high resolution imaging for optoelectronic and biomedical applications.

  14. Origin of near to middle infrared luminescence and energy transfer process of Er3+/Yb3+co-doped fluorotellurite glasses under different excitations

    PubMed Central

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

    2015-01-01

    We report the near to middle infrared luminescence and energy transfer process of Er3+/Yb3+ 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 Er3+:I13/2→4I15/2 and I11/2→4I13/2 transitions are observed, in which Yb3+ ions can increase pumping efficiency and be used as energy transfer donors. Meanwhile, Yb3+ can also be used as an acceptor and intensive upconversion luminescence of around 1000 nm is achieved from Er3+:I11/2→4I15/2 and Yb3+: F5/2→4F7/2 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 Er3+ and Yb3+ ion ratio is 1:1.5 and excess Yb3+ ions decrease energy transfer efficiency under the two pumpings. These results indicate that Er3+/Yb3+ co-doped fluorotellurite glasses are potential middle- infrared laser materials and may be used to increase the efficiency of the silicon solar cells. PMID:25648651

  15. 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.

  16. 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.

  17. Infrared microcalorimetric spectroscopy using quantum cascade lasers.

    PubMed

    Morales-Rodríguez, M E; Senesac, L R; Rajic, S; Lavrik, N V; Smith, D B; Datskos, P G

    2013-02-15

    We have investigated an IR microcalorimetric spectroscopy technique that can be used to detect the presence of trace amounts of target molecules. The chemical detection is accomplished by obtaining the IR photothermal spectra of molecules adsorbed on the surface of uncooled thermal micromechanical detectors. Although we use a chemical layer to absorb target molecules, IR microcalorimetric spectroscopy requires no chemical specific coatings. The chemical specificity of the presented method is a consequence of the wavelength-specific absorption of IR photons from tunable quantum cascade lasers due to vibrational spectral bands of the analyte. We have obtained IR photothermal spectra for trace concentrations of 1,3,5-Trinitroperhydro-1,3,5-triazine and a monolayer of 2-Sulfanylethan-1-ol (2-mercaptoethanol) over the wavelength region from 6 to 10 μm. We found that both chemicals exhibit a number of photothermal absorption features that are in good agreement with their respective IR spectra.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. Molecular recognition using receptor-free nanomechanical infrared spectroscopy based on a quantum cascade laser

    PubMed Central

    Kim, Seonghwan; Lee, Dongkyu; Liu, Xunchen; Van Neste, Charles; Jeon, Sangmin; Thundat, Thomas

    2013-01-01

    Speciation of complex mixtures of trace explosives presents a formidable challenge for sensors that rely on chemoselective interfaces due to the unspecific nature of weak intermolecular interactions. Nanomechanical infrared (IR) spectroscopy provides higher selectivity in molecular detection without using chemoselective interfaces by measuring the photothermal effect of adsorbed molecules on a thermally sensitive microcantilever. In addition, unlike conventional IR spectroscopy, the detection sensitivity is drastically enhanced by increasing the IR laser power, since the photothermal signal comes from the absorption of IR photons and nonradiative decay processes. By using a broadly tunable quantum cascade laser for the resonant excitation of molecules, we increased the detection sensitivity by one order of magnitude compared to the use of a conventional IR monochromator. Here, we demonstrate the successful speciation and quantification of picogram levels of ternary mixtures of similar explosives (trinitrotoluene (TNT), cyclotrimethylene trinitramine (RDX), and pentaerythritol tetranitrate (PETN)) using nanomechanical IR spectroscopy. PMID:23346368

  3. 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.

  4. 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.

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

    SciTech Connect

    Singaravelu, Senthil R.; Klopf, John M.; Schriver, Kenneth E.; Park, HyeKyoung; Kelley, Michael J.; Haglund, Jr., Richard F.

    2013-08-01

    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.

  6. The spread of excitation in neocortical columns visualized with infrared-darkfield videomicroscopy.

    PubMed

    Dodt, H U; D'Arcangelo, G; Pestel, E; Zieglgänsberger, W

    1996-07-08

    A combination of darkfield techniques and infrared videomicroscopy was used to measure the intrinsic optical signal (IOS) in slices of adult rat neocortex. The IOS, which reflects changes in light transmittance and scattering, provides a means of studying the spread of neuronal excitation and its modulation with high sensitivity and spatial resolution. The column-like IOS elicited by orthodromic stimulation is in accordance with models of neocortical circuitry. Blockade of synaptic transmission by the glutamate receptor antagonists 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and D-2-amino-5-phosphovaleric acid (D-APV) reduced the IOS. The GABAA agonist muscimol and the neuroactive steroid 5 alpha-tetrahydrodeoxy-corticosterone (5 alpha-THDOC) decreased the spread of excitation, whereas the GABAA antagonist bicuculline increased it. The present data suggest that the spatial spread of excitation in different neocortical layers is delimited by GABAergic inhibition mediated by the activation of GABAA receptors.

  7. 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.

  8. 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.

  9. 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

  10. Monolithically integrated mid-infrared quantum cascade laser and detector.

    PubMed

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

    2013-02-06

    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 indicates its use for single mode laser arrays. We have measured a peak signal of 191.5 mV at the on-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.

  11. 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.

  12. 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.

  13. 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.

  14. Infrared laser pulse triggers increased singlet oxygen production in tumour cells

    PubMed Central

    Sokolovski, S. G.; Zolotovskaya, S. A.; Goltsov, A.; Pourreyron, C.; South, A. P.; Rafailov, E. U.

    2013-01-01

    Photodynamic therapy (PDT) is a technique developed to treat the ever-increasing global incidence of cancer. This technique utilises singlet oxygen (1O2) generation via a laser excited photosensitiser (PS) to kill cancer cells. However, prolonged sensitivity to intensive light (6–8 weeks for lung cancer), relatively low tissue penetration by activating light (630 nm up to 4 mm), and the cost of PS administration can limit progressive PDT applications. The development of quantum-dot laser diodes emitting in the highest absorption region (1268 nm) of triplet oxygen (3O2) presents the possibility of inducing apoptosis in tumour cells through direct 3O2 → 1O2 transition. Here we demonstrate that a single laser pulse triggers dose-dependent 1O2 generation in both normal keratinocytes and tumour cells and show that tumour cells yield the highest 1O2 far beyond the initial laser pulse exposure. Our modelling and experimental results support the development of direct infrared (IR) laser-induced tumour treatment as a promising approach in tumour PDT. PMID:24336590

  15. 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.

  16. 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.

  17. Near-infrared laser speckle imaging of human breast tissue

    NASA Astrophysics Data System (ADS)

    Bean, Robert Speer

    Current methods of breast cancer diagnostics (self-exam, clinical exam, x-ray mammography) fail to diagnose a significant number of cases while still in readily operable stages. This is especially true in younger women, where fibrotic tissue reduces the efficacy of x-ray mammography. Near infrared (NIR) laser photons pass diffusively through human tissue, creating a speckle pattern in a detector after transmission. The high and low intensity variations of the speckle have the appearance of random noise, but are not. The speckle pattern will have an intensity distribution that is informative about the scattering and absorption properties of the tissue that is imaged. Adaptations to the Los Alamos National Laboratory MCNP code are described that allow simulation of NIR laser transport through human tissue. A HeNe laser was used to create laser intensity patterns via transmission through homogeneous and non-homogeneous tissue phantoms. The Kolmogorov-Smirnov test was used to compare the cumulative distribution functions of the laser intensity patterns, and identify the presence of a non-homogeneity. Laser speckle techniques offer the ability to image tumors with few (<3) millimeter resolution without ionizing radiation dose.

  18. Infrared Laser Ablation with Vacuum Capture for Fingermark Sampling

    NASA Astrophysics Data System (ADS)

    Donnarumma, Fabrizio; Camp, Eden E.; Cao, Fan; Murray, Kermit K.

    2017-09-01

    Infrared laser ablation coupled to vacuum capture was employed to collect material from fingermarks deposited on surfaces of different porosity and roughness. Laser ablation at 3 μm was performed in reflection mode with subsequent capture of the ejecta with a filter connected to vacuum. Ablation and capture of standards from fingermarks was demonstrated on glass, plastic, aluminum, and cardboard surfaces. Using matrix assisted laser desorption ionization (MALDI), it was possible to detect caffeine after spiking with amounts as low as 1 ng. MALDI detection of condom lubricants and detection of antibacterial peptides from an antiseptic cream was demonstrated. Detection of explosives from fingermarks left on plastic surfaces as well as from direct deposition on the same surface using gas chromatography mass spectrometry (GC-MS) was shown. [Figure not available: see fulltext.

  19. 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.

  20. 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.

  1. Laser selective cutting of biological tissues by impulsive heat deposition through ultrafast vibrational excitations.

    PubMed

    Franjic, Kresimir; Cowan, Michael L; Kraemer, Darren; Miller, R J Dwayne

    2009-12-07

    Mechanical and thermodynamic responses of biomaterials after impulsive heat deposition through vibrational excitations (IHDVE) are investigated and discussed. Specifically, we demonstrate highly efficient ablation of healthy tooth enamel using 55 ps infrared laser pulses tuned to the vibrational transition of interstitial water and hydroxyapatite around 2.95 microm. The peak intensity at 13 GW/cm(2) was well below the plasma generation threshold and the applied fluence 0.75 J/cm(2) was significantly smaller than the typical ablation thresholds observed with nanosecond and microsecond pulses from Er:YAG lasers operating at the same wavelength. The ablation was performed without adding any superficial water layer at the enamel surface. The total energy deposited per ablated volume was several times smaller than previously reported for non-resonant ultrafast plasma driven ablation with similar pulse durations. No micro-cracking of the ablated surface was observed with a scanning electron microscope. The highly efficient ablation is attributed to an enhanced photomechanical effect due to ultrafast vibrational relaxation into heat and the scattering of powerful ultrafast acoustic transients with random phases off the mesoscopic heterogeneous tissue structures.

  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. 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.

  4. 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

  5. [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.

  6. 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.

  7. Selective excitation of high-order laser modes and its application to vortex array laser beam generation

    NASA Astrophysics Data System (ADS)

    Chu, Shu-Chun; Otsuka, Kenju

    2010-02-01

    This study reports a method of creating vortex array laser beams by superposing high-order laser modes on their rotated replicas. An interferometer configuration was used to convert these high-order laser modes to vortex array laser beams containing multi vortexes aligned in an almost square manner. To generate this kind vortex array laser beams, this study reports systematic approaches to the selective excitation of high-order laser modes in end-pumped solid-state lasers with laser resonators and asymmetric pumping. The resulting vortex array laser beams can be used as optical tweezers and atom traps in the form of two-dimensional arrays, or to study the transfer of angular momentum to micro particles or atoms (Bose-Einstein condensate).

  8. [Research Progress on Laser-Induced Breakdown Spectroscopy Based on Resonance Excitation].

    PubMed

    Wang, Xu-zhao; Hao, Zhong-qi; Guo, Lian-bo; Li, Xiang-you; Lu, Yong-feng; Zeng, Xiao-yan

    2015-05-01

    Laser-induced breakdown spectroscopy (LIBS), a new kind of atomic spectrum analysis technology, has attracted much atterition of the researchers due to its characteristics of real-time, simultaneous multi-element analysis, and no sample preparation. However, the poor analytical sensitivity has been an important factor that restricts the development of this technology. LIBS based on resonance excitation combines atomic fluorescence spectroscopy and laser-induced breakdown spectroscopy and selectively excites the target elements. In this way, the analytical sensitivity of LIBS can be improved substantially and its application for trace elements detection is greatly expanded. In this paper, the research development of LIBS based on resonance excitation is summarized. The generation of atomic, fluorescence spectrum in laser-induced plasma, the typical classification and the basic principle of LIBS based on resonance. excitation are introduced. The influence of ablation laser energy, resonant laser energy and wavelength, delay between the ablation laser and the resonant laser, and the gate width on spectral enhancement are analyzed in detail. The application status and deficiencies of LIBS based on resonance excitation in the fields of metallurgy, environmental monitoring and isotope detection are elaborated. Future prospects of LIBS based on resonance excitation are also described.

  9. 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.

  10. 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

  11. Acoustic and flexural excitation of a floating structure by a single laser pulse.

    PubMed

    Philp, W R; Podlesak, M; Pierce, S G

    1996-12-20

    The acoustic and flexural vibrations of a small-scale floating structure following irradiation by a pulsed Nd:glass laser are compared with a radiated underwater sound field. A single subablative laser pulse of 600-μs duration was used both to bend and shock the floating structure at the irradiation site. The laser pulse caused the structure to flex at a frequency of approximately 1 kHz whereas relaxation oscillations in the laser output simultaneously excited ultrasonic Lamb waves within the material bulk. We present results to illustrate the broad bandwidth provided by this unusual form of excitation.

  12. 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

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. Investigation intensity response of distributed-feedback fiber laser to external acoustic excitation Investigation intensity response of DFB fiber laser

    NASA Astrophysics Data System (ADS)

    Wang, P. P.; Chang, J.; Zhu, C. G.; Wang, W. J.; Zhao, Y. J.; Zhang, X. L.; Peng, G. D.; Lv, G. P.; Liu, X. Z.; Wang, H.

    2012-08-01

    The intensity response of distributed-feedback (DFB) fiber laser to external acoustic excitation has been investigated. On that basis, an intensity modulated sensing system based on DFB fiber laser has been constructed. Acoustic pressure sensitivity of the intensity-type sensor at frequencies ranging from 800 Hz to 9 kHz has been obtained by experiments for the first time to the authors' knowledge. In addition, intensity response property of DFB fiber laser to external acoustic excitation with different pump power has been analyzed. We conclude that the signal power increases with the pump drive current of 980 nm laser diode (LD), and yet the ratios of signal power to DFB fiber laser power decrease. It confirms that the anti-interference performance of DFB fiber laser to fixed external acoustic interference becomes stronger with the increasing current of pump source, and this conclusion is beneficial to the investigation of wavelength demodulated sensors.

  18. Impedance matching in RF excited fast axial flow CO2 laser: The role of the capacitance due to laser head

    NASA Astrophysics Data System (ADS)

    Bhagat, M. S.; Biswas, A. K.; Rana, L. B.; Kukreja, L. M.

    2012-10-01

    Impedance matching in an indigenously developed 2 kW RF-excited fast axial flow (RF-FAF) CO2 laser was seen to be significantly influenced by the capacitance formed between the laser head and the electrodes. We find in the published literature that this capacitance is generally assumed to be negligible while designing the matching network in the RF-FAF CO2 lasers. It is shown that this capacitance could have a significant value and consequently would modify the design of the matching network remarkably for a specific laser design studied in the present case. The widely used discharge load model for capacitively coupled RF (CCRF) discharge excited CO2 laser plasma is extended to include this capacitance. The method of measurement of this capacitance using a bridge and the ANSYS software based simulation of its formation due to the laser head structure are discussed.

  19. 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).

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. New infrared solid state laser materials for CALIOPE

    SciTech Connect

    DeLoach, L.D.; Page, R.H.; Wilke, G.D.

    1994-08-01

    Tunable infrared laser light may serve as a useful means by which to detect the presence of the targeted effluents. Since optical parametric oscillators (OPOs) have proven to be a versatile method of generating coherent light from the ultraviolet to the mid-infrared, this technology is a promising choice by which to service the CALIOPE applications. In addition, since some uncertainty remains regarding the precise wavelengths and molecules that will be targeted, the deployment of OPOs retains the greatest amount of wavelength flexibility. Another approach that the authors are considering is that of generating tunable infrared radiation directly with a diode-pumped solid state laser (DPSSL). One important advantage of a DPSSL is that it offers flexible pulse format modes that can be tailored to meet the needs of a particular application and target molecule. On the other hand, direct generation by a tunable DPSSL will generally be able to cover a more limited wavelength range than is possible with OPO technology. In support of the CALIOPE objectives the authors are exploring the potential for laser action among a class of materials comprised of transition metal-doped zinc chalcogenide crystals (i.e., ZnS, ZnSe and ZnTe). The Cr{sup 2+}, Co{sup 2+} and Ni{sup 2+} dopants were selected as the most favorable candidates, on the basis of their documented spectral properties in the scientific literature. Thus far, the authors have characterized the absorption and emission properties of these ions in the ZnS and ZnSe crystals. The absorption spectra are used to determine the preferred wavelength at which the crystal should be pumped, while the emission spectra reveal the extent of the tuning range potentially offered by the material. In addition, measurements of the emission lifetime as a function of temperature turn out to be quite useful, since this data is suggestive of the room temperature emission yield.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. Infrared free electron laser enhanced transdermal drug delivery

    NASA Astrophysics Data System (ADS)

    Awazu, Kunio; Uchizono, Takeyuki; Suzuki, Sachiko; Yoshikawa, Kazushi

    2005-08-01

    It is necessary to control enhancement of transdermal drug delivery with non-invasive. The present study was investigated to assess the effectivity of enhancing the drug delivery by irradiating 6-μm region mid infrared free electron laser (MIR-FEL). The enhancement of transdermal drug (lidocaine) delivery of the samples (hairless mouse skin) irradiated with lasers was examined for flux (μg/cm2/h) and total penetration amount (μg/cm2) of lidocaine by High performance Liquid Chromatography (HPLC). The flux and total amount penatration date was enhanced 200-300 fold faster than the control date by the laser irradiation. FEL irradiating had the stratum corneum, and had the less thermal damage in epidermis. The effect of 6-μm region MIR-FEL has the enhancement of transdermal drug delivery without removing the stratum corneum because it has the less thermal damage. It leads to enhancement drug delivery system with non-invasive laser treatment.

  20. 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.

  1. Vacuum electrospray of volatile liquids assisted by infrared laser irradiation.

    PubMed

    Ninomiya, Satoshi; Chen, Lee Chuin; Suzuki, Hiroaki; Sakai, Yuji; Hiraoka, Kenzo

    2012-04-15

    Current large cluster sources such as C(60) or argon utilize gas-phase sources which are of low-brightness and cannot be focused efficiently to better than 1 micron diameter spot size. The development of a high-brightness large cluster ion source is of critical importance to achieve high resolution in secondary ion mass spectrometry (SIMS) imaging of organics. We propose a new high-brightness large cluster ion source, and a technique for producing a stable electrospray of volatile liquids under vacuum. It is known that vacuum electrospray of volatile liquids such as water is extremely difficult because of freezing of the liquids introduced in vacuum by evaporative cooling. To avoid freezing, the tip of the electrospray emitter was irradiated by a continuous wave infrared laser. Without continuous laser irradiation the vacuum electrospray of a water/methanol solution was unstable with respect to the shapes of the Taylor cone and current, whereas continuous laser irradiation produced a stable electrospray of water. The typical modes of electrospray were clearly observed with an optical microscope even under vacuum conditions. A stable vacuum electrospray could be achieved by improving the vacuum pressure to suppress electric discharge and by using the laser to maintain the liquid state. This is the first description of the production of a stable vacuum electrospray of volatile liquids such as water. This vacuum electrospray technique can be expected to produce a novel high-brightness large cluster ion beam source. Copyright © 2012 John Wiley & Sons, Ltd.

  2. Satellite laser ranging in the near-infrared regime

    NASA Astrophysics Data System (ADS)

    Eckl, Johann J.; Schreiber, K. Ulrich; Schüler, Torben

    2017-05-01

    Satellite Laser Ranging Systems typically operate on the second harmonic wavelength of a pulsed Nd:YAG laser at a wavelength of 532 nm. The absence of sufficiently sensitive photo-detectors with a reasonably large active area made it beneficial to trade the conversion loss of frequency doubling against the higher quantum efficiency of the detectors. Solid state silicon detectors in the near infra-red regime at λ = 1.064 µm also suffered from high thermal noise and slow signal rise times, which increased the scatter of the measurements by more than a factor of 3 over the operation at λ = 532 nm. With the availability of InGaAs/InP compound - Single Photon Avalanche Diodes the situation has changed considerably. Their quantum efficiency has reached 70% and the compound material of these diodes provides a response bandwidth, which is commensurate with high high speed detectors in the regime of 532 nm. We have investigated the properties of such a diode type Princeton Lightwave PGA-200-1064 for its suitability for SLR at the Nd:YAG fundamental wavelength with respect to the quantum efficiency and their timing properties. The results are presented in this paper. Furthermore, we provide remarks to on the performance of the diode compared to state of the art detectors, that operate at the Nd:YAG second harmonic wavelength. Finally, we give an estimate of the photoelectron statistics in satellite laser ranging for different operational parameters of the Wettzell Laser Ranging System.

  3. 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.

  4. Luminescence of crystals excited by a KrCl laser and a subnanosecond electron beam

    SciTech Connect

    Lipatov, E I; Tarasenko, Viktor F; Orlovskii, Viktor M; Alekseev, S B

    2005-08-31

    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. (interaction of laser radiation with matter)

  5. 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.

  6. 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

  7. 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.

  8. 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.

  9. 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.

  10. High power continuous wave atomic Xe laser with radio frequency excitation

    NASA Astrophysics Data System (ADS)

    Vitruk, P. P.; Morley, R. J.; Baker, H. J.; Hall, D. R.

    1995-09-01

    Radio frequency discharges in Ar/He/Xe gas mixtures have been studied in the range 5-150 MHz, and the importance of the ion sheaths in Xe laser excitation has been recognized. The discharge data have been used to improve the cw Xe laser performance, and efficiencies up to 0.8% observed. Area scaling in the slab geometry has been studied for α discharge excitation at 49 MHz, and multimode cw laser power up to 5.5 W has been observed. High quality beams have been produced at 4.9 W using a hybrid waveguide/unstable resonator.

  11. 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.

  12. CW Ultraviolet Laser Excited with an Electron Beam

    DTIC Science & Technology

    1989-10-01

    than the He-Ag ’ nfrared laser 2 Thne cotimum. average neon pressure was found to b7 ’Ce1 3 orr. W e note that with the octical cav4_ty ano- electr...Silfvast, "Neutral-Atcm Recombination Lasers in CO2 Laser-Vaporized Target Material," IEEE J. Quantum Electron., vol. QE-21, p. 1714, Oct. 1985. 4) W. T

  13. 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.

  14. Mid-infrared microspectroscopic imaging with a quantum cascade laser

    NASA Astrophysics Data System (ADS)

    Yeh, Kevin; Schulmerich, Matthew; Bhargava, Rohit

    2013-05-01

    Conventional mid-infrared (mid-IR) Fourier transform infrared (FT-IR) spectroscopic imaging systems employ an incoherent globar source and achieve spectral contrast through interferometry. While this approach is suitable for many general applications, recent advancements in broadly tunable external cavity Quantum Cascade Lasers (QCL) offer new approaches to and new possibilities for mid-IR micro-spectroscopic imaging. While QCL-based devices have yet to achieve the wide spectral range generally employed by spectroscopists for molecular analyses, they are starting to be used for microscopy at discrete frequencies. Here, we present a discrete frequency IR (DFIR) microscope based on a QCL source and explore its utility for mid-IR imaging. In our prototype instrument, spectral contrast is achieved by tuning the QCL to bands in a narrow spectral region of interest. We demonstrate wide-field imaging employing a 128x128 pixel liquid nitrogen cooled mercury cadmium telluride (MCT) focal plane array (FPA) detector. The resulting images demonstrate successful imaging as well as several unique features due to coherence effects from the laser source. Here we discuss the effects of this coherence and compare our instrument to conventional mid-IR imaging instrumentation.

  15. Patient identification using a near-infrared laser scanner

    NASA Astrophysics Data System (ADS)

    Manit, Jirapong; Bremer, Christina; Schweikard, Achim; Ernst, Floris

    2017-03-01

    We propose a new biometric approach where the tissue thickness of a person's forehead is used as a biometric feature. Given that the spatial registration of two 3D laser scans of the same human face usually produces a low error value, the principle of point cloud registration and its error metric can be applied to human classification techniques. However, by only considering the spatial error, it is not possible to reliably verify a person's identity. We propose to use a novel near-infrared laser-based head tracking system to determine an additional feature, the tissue thickness, and include this in the error metric. Using MRI as a ground truth, data from the foreheads of 30 subjects was collected from which a 4D reference point cloud was created for each subject. The measurements from the near-infrared system were registered with all reference point clouds using the ICP algorithm. Afterwards, the spatial and tissue thickness errors were extracted, forming a 2D feature space. For all subjects, the lowest feature distance resulted from the registration of a measurement and the reference point cloud of the same person. The combined registration error features yielded two clusters in the feature space, one from the same subject and another from the other subjects. When only the tissue thickness error was considered, these clusters were less distinct but still present. These findings could help to raise safety standards for head and neck cancer patients and lays the foundation for a future human identification technique.

  16. 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.

  17. 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.

  18. 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

  19. Implementation of time-resolved step-scan fourier transform infrared (FT-IR) spectroscopy using a kHz repetition rate pump laser.

    PubMed

    Magana, Donny; Parul, Dzmitry; Dyer, R Brian; Shreve, Andrew P

    2011-05-01

    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)(3)Cl(2) 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.

  20. Two-photon fluorescence excitation in continuous-wave infrared optical tweezers

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Sonek, G. J.; Berns, M. W.; Konig, K.; Tromberg, B. J.

    1995-11-01

    We report the observation of two-photon fluorescence excitation in a continuous-wave (cw) single-beam gradient force optical trap and demonstrate its use as an in situ probe to study the physiological state of an optically confined sample. In particular, a cw Nd:YAG (1064-nm) laser is used simultaneously to confine, and excite visible fluorescence from submicrometer regions of, cell specimens. Two-photon fluorescence emission spectra are presented for motile human sperm cells and immotile Chinese hamster ovary cells that have been labeled with nucleic acid (Propidium Iodide) and pH-sensitive (Snarf) fluorescent probes. The resulting spectra are correlated to light-induced changes in the physiological state experienced by the trapped cells. This spectral technique should prove extremely useful for monitoring cellular activity and the effects of confinement by optical tweezers.

  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. Effects of argon laser irradiation on polar excitations in frog sciatic nerve.

    PubMed

    Matsuda, Yoshiki; Niwa, Mayuka; Iwai, Hiromasa; Kogure, Shinichi; Honjoe, Nobuyuki; Komatsu, Mitsuaki; Ishii, Yoshio; Watanabe, Kazuhiro

    2006-07-01

    Since the mechanisms underlying the effects of low-power laser irradiation on the nervous system remain unclear, we examined whether such irradiation can influence ionic channels of the nerve membrane using the law of polar excitation in isolated frog sciatic nerve. Using 43 frogs (Xenopus laevis), nerve preparations were stimulated at 0.5/second using a 10-millisecond pulse at supramaximal intensity. Ar+ laser irradiation (457, 488, 514 nm; 50, 75, 100 mW) was applied for 30 minutes to the portion between the anode and cathode stimulating electrodes. Ar+ laser irradiations (457, 488 nm; 50 mW) blocked the generation of anode-break-excitation, rather than cathode-make-excitation. Such a selective effect occurred when applying a blocker of hyperpolarization-activated cation current (Ih) channel, ZD7288. Ar+ laser irradiation may influence Na+ channels in addition to Ih channels. (c) 2006 Wiley-Liss, Inc.

  3. Resonant vibrational excitation of ethylene molecules in laser-assisted diamond deposition

    NASA Astrophysics Data System (ADS)

    Fan, L. S.; Zhou, Y. S.; Wang, M. X.; Gao, Y.; Liu, L.; Silvain, J. F.; Lu, Y. F.

    2014-07-01

    The influence of resonant vibrational excitation of ethylene molecules in combustion chemical vapor deposition of diamond was investigated. Resonant vibrational excitation of the CH2-wagging mode (a type c fundamental band, υ7, at 949.3 cm-1) in ethylene molecules was achieved by using a wavelength-tunable CO2 laser with a matching wavelength at 10.532 µm. By comparing to laser irradiation at off-resonance wavelengths, an on-resonance vibrational excitation is more efficient in energy coupling, increasing flame temperatures, accelerating the combustion reactions, and promoting diamond deposition. An enhanced rate of 5.7 was achieved in terms of the diamond growth rate with an improved diamond quality index at a high flame temperature under a resonant excitation of the CH2-wagging mode. This study demonstrates that a resonant vibrational excitation is an effective route for coupling energy into the gas phase reactions and promoting the diamond synthesis process.

  4. Intense excitation source of blue-green laser

    NASA Astrophysics Data System (ADS)

    Han, Kwang S.

    1986-10-01

    An intense and efficient source for blue green laser useful for the space-based satellite laser applications, underwater strategic communication, and measurement of ocean bottom profile is being developed. The source in use, the hypocycloidal pinch plasma (HCP), and the dense plasma focus (DPF) can produce intense uv photons (200 to 400nm) which match the absorption spectra of both near UV and blue green dye lasers (300 to 400nm). As a result of optimization of the DPF light at 355nm, the blue green dye (LD490) laser output exceeding 4mJ was obtained at the best cavity tunning of the laser system. With the HCP pumped system a significant enhancement of the blue green laser outputs with dye LD490 and coumarin 503 has been achieved through the spectrum conversion of the pumping light by mixing a converter dye BBQ. The maximum increase of laser output with the dye mixture of LD490+BBQ and coumarin 503+BBQ was greater than 80%. In addition, the untunned near UV lasers were also obtained. The near UV laser output energy of P-terphenyl dye was 0.5mJ at lambda sub C=337nm with the bandwidth of 3n m for the pulse duration of 0.2us. Another near UV laser output energy obtained with BBQ dye was 25 mJ at lambda sub C=383nm with the bandwidth of 3nm for the pulse duration of 0.2us. Another near UV laser output energy obtained with BBQ dye was 25 mJ at lambda sub C=383nm with the bandwidth of 3nm for the pulse duration of 0.2microsec.

  5. Application of liposome-encapsulated ceramic phoshpors for cancer cell imaging under near infrared excitation

    NASA Astrophysics Data System (ADS)

    Akiyama, Hirotada; Tokuzen, Kimikazu; Otsuka, Hiroko; Soga, Kohei; Tashiro, Fumio

    2010-06-01

    Bioimaging with fluorescent probes is used as an invaluable tool in a biomedical field both in vivo and in vitro. However, organic dyes have some problems such as photo-breaching and cytotoxicity due to short wavelength with high quantum energy. Recently, a new approach using rare-earth-doped ceramic nanophosphors (RED-CNP) shows that fluorescence from RED-CNP in both visible (upconversion) and near infrared (NIR) wavelength region under NIR excitation is available for bioimaging. In order to efficiently introduce the RED-CNP into cancer cells, in this study we have developed a lipid nano-particles of liposome-encapsulated erbium (Er) ion-doped Y2O3 (lipo-Y2O3). Cationic lipo-Y2O3 could clearly visualize the intracellular region of human hepatocellular carcinoma Huh-7 cells by a fluorescence microscope measurements equipped with near-infrared excitation source scanning. The results imply that the lipo-Y2O3 would potentially be useful material for imaging of cancer cells. The embedded Y2O3 in the liposome having cancer-specific ligands and/or antibodies on its surface should have a great potential for cancer cell imaging in general in living subjects.

  6. Absorption-Ablation-Excitation Mechanism of Laser-Cluster Interactions in a Nanoaerosol System

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

    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 /cm2 , the scattering cross section of TiO2 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 SlE , Peclet PeE , and Damköhler DaE numbers defined to characterize the laser-induced aerothermochemical environment. For conditions where SlE≫1 , PeE≫1 , and DaE≪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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. Electro-optic modulator for infrared laser using gallium arsenide crystal

    NASA Technical Reports Server (NTRS)

    Walsh, T. E.

    1968-01-01

    Gallium arsenide electro-optic modulator used for infrared lasers has a mica quarter-wave plate and two calcite polarizers to amplitude or phase modulate an infrared laser light source in the wavelength range from 1 to 3 microns. The large single crystal has uniformly high resistivities, is strain free, and comparable in quality to good optical glass.

  15. 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.

  16. Design of stabilization system for medium wave infrared laser power

    NASA Astrophysics Data System (ADS)

    Ding, Zhong-kui; Wang, Lin; Shi, Xue-shun; Xu, Jun

    2013-12-01

    The 3~5um Medium Wave Infrared(MWIR) laser has gained a lot of attention for its important application values in remote sensing, medical, military and many other fields. However, there are many technical difficulties to fabricate those kind lasers, and the performance of their output power stabilities remain to be improved. In a practical application, the MWIR's output power will be instability when the temperature changes and the current varies. So a system of reducing MWIR power fluctuation should be established. In this paper, a photoelectric system of stabilizing the output power of He-Ne laser is developed, which is designed based on the theory of feedback control. Some primary devices and technologies are presented and the functions of each module are described in detail. Among of those, an auxiliary visible light path is designed to aid to adjust WMIR optical system. A converging lens as spatial filter is employed to eliminate stray light well. Dewar temperature control equipment is also used to reduce circuit noise in IR detector. The power supply of AD conversion circuit is independently designed to avoid the crosstalk caused by the analog section and digital section. Then the system has the advantages of good controllability, stability and high precision after above designation. Finally, the measurement precision of the system is also analyzed and verified.

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

    NASA Astrophysics Data System (ADS)

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

    1995-02-01

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

  18. 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.

  19. In vivo comparison of near infrared lasers for skin welding.

    PubMed

    Tabakoğlu, Haşim Ozgür; Gülsoy, Murat

    2010-05-01

    The skin closure abilities of near infrared lasers and suturing were compared by histological examination and mechanical tensile tests during a 21-day healing period. One-centimeter incisions on the dorsal skin of Wistar rats were treated by one of the closing techniques: (a) soldering, using an 809 nm diode laser (0.5 W, 5 s) with 25% bovine serum albumin (BSA) and 2.5 mg/ml indocyanine green (ICG); (b) direct welding with a 980 nm diode laser (0.5 W, 5 s); (c) direct welding with a 1,070 nm fiber laser (0.5 W, 5 s); (d) suturing. Six spots (79.61 J/cm(2) for each spot) were applied through the incisions. Healing was inspected on the 1st, 4th, 7th, 14th, and 21st post-operative days. The closure index (CI), thermally altered area (TAA), granulation area (GA) and epidermal thickness (ET) were determined by histological examination. Tensile tests were performed at a 5 mm/min crosshead speed up to the first opening along the incision. Immediate superficial closure with high CI values was found for the laser-irradiated incisions at the early phase of recovery. Clear welds without thermal damage were observed for the group irradiated at 1,070 nm. For the sutured group, the incisions remained unclosed for the first day, and openings through the incision were observed. At the end of the 21-day recovery period, no differences between experimental groups were observed in terms of the CI, GA and ET values. However, the tensile strength of the groups irradiated at 980 nm and 1,070 nm was found to be higher than that of the sutured incisions. The laser welding techniques were found to be reliable in terms of immediate and mechanically strong closure compared with suturing. Of them, 1,070 nm laser welding yielded noticeably stronger bonds, with minimal scarring at the end of the 21-days of recovery.

  20. 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.

  1. 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

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. Plasma undulator based on laser excitation of wakefields in a plasma channel.

    PubMed

    Rykovanov, S G; Schroeder, C B; Esarey, E; Geddes, C G R; Leemans, W P

    2015-04-10

    An undulator is proposed based on the plasma wakefields excited by a laser pulse in a plasma channel. Generation of the undulator fields is achieved by inducing centroid oscillations of the laser pulse in the channel. The period of such an undulator is proportional to the Rayleigh length of the laser pulse and can be submillimeter, while preserving high undulator strength. The electron trajectories in the undulator are examined, expressions for the undulator strength are presented, and the spontaneous radiation is calculated. Multimode and multicolor laser pulses are considered for greater tunability of the undulator period and strength.

  8. 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.

  9. 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.

  10. 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.

  11. Vacuum ultraviolet argon excimer laser excited by optical-field-induced ionized electrons produced in an argon-filled hollow fiber

    NASA Astrophysics Data System (ADS)

    Kubodera, Shoichi; Kaku, Masanori; Katto, Masahito

    2011-10-01

    Short-wavelength lasers in the vacuum ultraviolet (VUV) spectral region between 100 and 200 nm have not yet been developed to the same degree as visible and infrared lasers. We have demonstrated the production of argon excimers via an optical-field-induced ionization (OFI) process by using a high-intensity infrared laser. We here report optical amplification of argon excimers at the wavelength of 126 nm by producing an extended OFI plasma inside an argon-filled hollow fiber with an inner diameter of 250 microns with a length of 5.0 cm. A gain-length product of 4.3 through the use of single-pass amplification with VUV optics was observed, indicating a small signal gain coefficient of 0.86 cm-1 with an uncertainty of 0.03. It was found that the hollow fiber served to extend the OFI plasma length and to guide the excitation of the infrared laser and the produced VUV emissions at 126 nm, but did not affect the OFI plasma conditions to produce argon excimer molecules. Short-wavelength lasers in the vacuum ultraviolet (VUV) spectral region between 100 and 200 nm have not yet been developed to the same degree as visible and infrared lasers. We have demonstrated the production of argon excimers via an optical-field-induced ionization (OFI) process by using a high-intensity infrared laser. We here report optical amplification of argon excimers at the wavelength of 126 nm by producing an extended OFI plasma inside an argon-filled hollow fiber with an inner diameter of 250 microns with a length of 5.0 cm. A gain-length product of 4.3 through the use of single-pass amplification with VUV optics was observed, indicating a small signal gain coefficient of 0.86 cm-1 with an uncertainty of 0.03. It was found that the hollow fiber served to extend the OFI plasma length and to guide the excitation of the infrared laser and the produced VUV emissions at 126 nm, but did not affect the OFI plasma conditions to produce argon excimer molecules. Part of this work has been supported by

  12. Chalcogenide molded freeform optics for mid-infrared lasers

    NASA Astrophysics Data System (ADS)

    Chenard, Francois; Alvarez, Oseas; Yi, Allen

    2017-05-01

    High-precision chalcogenide molded micro-lenses were produced to collimate mid-infrared Quantum Cascade Lasers (QCLs). Molded cylindrical micro-lens prototypes with aspheric contour (acylindrical), high numerical aperture (NA 0.8) and small focal length (f<2 mm) were fabricated to collimate the QCL fast-axis beam. Another innovative freeform micro-lens has an input acylindrical surface to collimate the fast axis and an orthogonal output acylindrical surface to collimate the slow axis. The thickness of the freeform lens is such that the output fast- and slow-axis beams are circular. This paper presents results on the chalcogenide molded freeform micro-lens designed to collimate and circularize QCL at 4.6 microns.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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

  2. 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.

  3. 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.

  4. Single frequency and wavelength stabilized near infrared laser source for water vapor DIAL remote sensing application

    NASA Astrophysics Data System (ADS)

    Chuang, Ti; Walters, Brooke; Shuman, Tim; Losee, Andrew; Schum, Tom; Puffenberger, Kent; Burnham, Ralph

    2015-02-01

    Fibertek has demonstrated a single frequency, wavelength stabilized near infrared laser transmitter for NASA airborne water vapor DIAL application. The application required a single-frequency laser transmitter operating at 935 nm near infrared (NIR) region of the water vapor absorption spectrum, capable of being wavelength seeded and locked to a reference laser source and being tuned at least 100 pm across the water absorption spectrum for DIAL on/off measurements. Fibertek is building a laser transmitter system based on the demonstrated results. The laser system will be deployed in a high altitude aircraft (ER-2 or UAV) to autonomously perform remote, long duration and high altitude water vapor measurements.

  5. 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.

  6. 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.

  7. Photoacoustic-based detector for infrared laser spectroscopy

    SciTech Connect

    Scholz, L.; Palzer, S.

    2016-07-25

    In this contribution, we present an alternative detector technology for use in direct absorption spectroscopy setups. Instead of a semiconductor based detector, we use the photoacoustic effect to gauge the light intensity. To this end, the target gas species is hermetically sealed under excess pressure inside a miniature cell along with a MEMS microphone. Optical access to the cell is provided by a quartz window. The approach is particularly suitable for tunable diode laser spectroscopy in the mid-infrared range, where numerous molecules exhibit large absorption cross sections. Moreover, a frequency standard is integrated into the method since the number density and pressure inside the cell are constant. We demonstrate that the information extracted by our method is at least equivalent to that achieved using a semiconductor-based photon detector. As exemplary and highly relevant target gas, we have performed direct spectroscopy of methane at the R3-line of the 2v{sub 3} band at 6046.95 cm{sup −1} using both detector technologies in parallel. The results may be transferred to other infrared-active transitions without loss of generality.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. Plasmon excitation and electron emission of a carbon nanotube under a linearly polarized laser: A real-time first-principles study

    NASA Astrophysics Data System (ADS)

    Uchida, Kazuki; Watanabe, Kazuyuki

    2017-09-01

    We study the properties of electron excitation and emission of a finite carbon nanotube (CNT) under a linearly polarized femtosecond laser using real-time time-dependent density-functional theory. We find a plasmon resonance in the near-infrared region of the optical absorption spectrum that is highly sensitive to the laser polarization direction. The laser polarization direction dependence of the plasmon excitation obtained in the present study is consistent with the properties of polarized optical absorption observed in experiments. In electron emission that occurs subsequent to electronic excitation, the yield of emitted electrons also shows a laser polarization direction dependence, and the kinetic energy spectrum of the emitted electrons is broadened in the high-energy regime due to the electron acceleration caused by plasmon-induced electric-field enhancement. The findings of the present study are of crucial importance for understanding the laser-CNT interaction, which is a prerequisite for applications of CNTs in electron emitters, nanodevices, and optoelectronic components and sensors.

  13. 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.

  14. 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.

  15. Selective excitation of lowest-order transverse ring modes in a quasi-stadium laser diode.

    PubMed

    Fukushima, Takehiro; Shinohara, Susumu; Sunada, Satoshi; Harayama, Takahisa; Arai, Kenichi; Sakaguchi, Koichiro; Tokuda, Yasunori

    2013-10-15

    For a two-dimensional quasi-stadium laser diode, we demonstrate stable excitation of the lowest-order transverse ring modes by optimally designing the confocal end mirrors of the laser cavity based on extended Fox-Li mode calculations. We observe kink-free light output versus injection current characteristics and highly directional single-peak emissions corresponding to the diamond-shaped trajectory in the cavity. These results provide convincing evidence for selective excitation of the lowest-order transverse modes.

  16. 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.

  17. Progress in table-top transient collisional excitation x-ray lasers at LLNL

    SciTech Connect

    Da Silva, L B; Dunn, J; Li, Y; Nilsen, J; Osterheld, A; Shepherd, R; Shlyaptsev, V N

    1999-02-07

    We present progress in experiments for high efficiency Ne-like and Ni-like ion x-ray lasers using the transient collisional excitation scheme. Experimental results have been obtained on the COMET 15 TW table-top laser system at the Lawrence Livermore National Laboratory (LLNL). The plasma formation, ionization and collisional excitation of the x-ray laser have been optimized using two sequential laser pulses of 600 ps and 1 ps duration with an optional pre-pulse. We have observed high gains up to 55 cm{sup {minus}1} in Ne-like and Ni-like ion schemes for various atomic numbers. We report strong output for the 4d - 4p line in lower Z Ni-like ion sequence for Mo to Y, lasing from {approximately}190 {angstrom} to 240 {angstrom}, by pumping with less than 5 J energy on target.

  18. Direct printing of microstructures by femtosecond laser excitation of nanocrystals in solution

    SciTech Connect

    Shou, Wan; Pan, Heng

    2016-05-23

    We report direct printing of micro/sub-micron structures by femtosecond laser excitation of semiconductor nanocrystals (NCs) in solution. Laser excitation with moderate intensity (10{sup 11}–10{sup 12} W/cm{sup 2}) induces 2D and 3D deposition of CdTe nanocrystals in aqueous solution, which can be applied for direct printing of microstructures. It is believed that laser irradiation induces charge formation on nanocrystals leading to deposition. Furthermore, it is demonstrated that the charged nanocrystals can respond to external electrical bias, enabling a printing approach based on selective laser induced electrophoretic deposition. Finally, energy dispersive X-ray analysis of deposited structures shows oxidation occurs and deposited structure mainly consists of Cd{sub x}O.

  19. 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

  20. Near-infrared hybrid plasmonic multiple quantum well nanowire lasers.

    PubMed

    Wang, Jiamin; Wei, Wei; Yan, Xin; Zhang, Jinnan; Zhang, Xia; Ren, Xiaomin

    2017-04-17

    The lasing characteristics of hybrid plasmonic AlGaAs/GaAs multiple quantum well (MQW) nanowire (NW) lasers beyond diffraction limit have been investigated by 3D finite-difference time-domain simulations. The results show that the hybrid plasmonic MQW NW has lower threshold gain over a broad diameter range in comparison with its photonic counterpart. Beyond the diffraction limit, the hybrid plasmonic MQW NW has a lowest threshold gain of 788 cm-1 at a diameter of 130 nm, and a cutoff diameter of 80 nm, half that of the photonic lasers. In comparison with the hybrid plasmonic core-shell NWs, the hybrid plasmonic MQW NWs exhibit significantly lower threshold gain, higher Purcell factor, and smaller cutoff diameter, which are attributed to the superior overlap between the hybrid plasmonic modes and gain medium, as well as a stronger optical confinement due to the grating-like effect of MQW structures. Moreover, the hybrid plasmonic MQW NW has a lower threshold gain than that of the core-shell NW over a broad wavelength range. The hybrid plasmonic MQW NW structure is promising for ultrasmall and low-consumption near-infrared nanolasers.

  1. 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.

  2. 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.

  3. 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.

  4. Laser tissue soldering with near-infrared absorbing nanoparticles

    NASA Astrophysics Data System (ADS)

    Gobin, Andre M.; O'Neal, D. P.; Halas, Naomi J.; Drezek, Rebekah A.; West, Jennifer L.

    2005-04-01

    Gold nanoshells are a new class of nanoparticles with tunable optical absorption that can be placed in the near infrared. Gold nanoshells consist of a spherical silica core surrounded by a thin gold shell. The ratio of the sizes of the core diameter to the shell thickness as well as the total size of the nanoshell determines the optical absorption properties. Previous experiments have shown that these nanoparticles are stable at >325°C for durations typical of laser tissue welding. We have investigated the use of gold nanoshells as exogenous NIR absorbers to facilitate ex vivo laser tissue soldering. For ex vivo testing, gold nanoshells with peak absorption at approximately 820 nm were suspended in an albumin solder formulation and applied to muscle strips, followed by irradiation of the tissue at 821 nm. Mechanical testing of nanoshell-solder welds in muscle revealed successful fusion of tissues with tensile strengths of the weld site equal to the native tissue. The use of thermally stable nanoshells as an exogenous absorber allows the usage of light sources that are minimally absorbed by tissue components, thereby minimizing damage to surrounding tissue and producing welds sufficient for wound closure.

  5. Design study of a laser-cooled infrared sensor

    NASA Astrophysics Data System (ADS)

    Hehlen, Markus P.; Boncher, William L.; Love, Steven P.

    2015-03-01

    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. 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

  7. 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

  8. 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-.

  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. 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).

  13. Investigations of the thermal response of laser-excited biomolecules.

    PubMed Central

    Li, P; Champion, P M

    1994-01-01

    A model is presented that connects the underlying classical thermal transport coefficients to the experimentally determined vibrational temperature of a photoexcited chromophore embedded in a protein matrix that is surrounded by water. Both photo-stationary state heating (e.g., within a 10-ns laser pulse) and transient cooling (e.g., after termination of the laser pulse) are treated. Because only a few thermal transport parameters can be experimentally determined, this simple model provides a practical and efficient method for describing the temperatures of the chromophore, protein, and solvent as functions of time and position. We expect that such a model will be useful in interfacing experimental observations with more elaborate molecular dynamics calculations, which depend upon many variables. In the transient cooling process, which is relevant for ultrafast pulsed laser measurements, the temperature of the chromophore follows a double exponential decay at short times, whereas at longer times the thermal decay "rolls over" to a diffusion limit (t-3/2). For typical 10-ns laser pulses (approximately 0.5 GW/cm2) and chromophore absorption cross-sections (approximately 10(-16) cm2), we find that the biomolecule reaches thermal steady-state on a ps time scale. The role of the various thermal transport coefficients and their independent experimental determination is also discussed. PMID:8161696

  14. 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.

  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. 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

  17. Germanium-on-silicon mid-infrared grating couplers with low-reflectivity inverse taper excitation.

    PubMed

    Alonso-Ramos, Carlos; Nedeljkovic, Milos; Benedikovic, Daniel; Penadés, Jordi Soler; Littlejohns, Callum G; Khokhar, Ali Z; Pérez-Galacho, Diego; Vivien, Laurent; Cheben, Pavel; Mashanovich, Goran Z

    2016-09-15

    A broad transparency range of its constituent materials and compatibility with standard fabrication processes make germanium-on-silicon (Ge-on-Si) an excellent platform for the realization of mid-infrared photonic circuits. However, the comparatively large Ge waveguide thickness and its moderate refractive index contrast with the Si substrate hinder the implementation of efficient fiber-chip grating couplers. We report for the first time, to the best of our knowledge, a single-etch Ge-on-Si grating coupler with an inversely tapered access stage, operating at a 3.8 μm wavelength. Optimized grating excitation yields a coupling efficiency of -11  dB (7.9%), the highest value reported for a mid-infrared Ge-on-Si grating coupler, with reflectivity below -15  dB (3.2%). The large periodicity of our higher-order grating design substantially relaxes the fabrication constraints. We also demonstrate that a focusing geometry allows a 10-fold reduction in inverse taper length, from 500 to 50 μm.

  18. 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.

  19. Origin of coherent phonons in Bi2Te3 excited by ultrafast laser pulses

    NASA Astrophysics Data System (ADS)

    Wang, Yaguo; Guo, Liang; Xu, Xianfan; Pierce, Jonathan; Venkatasubramanian, Rama

    2013-08-01

    Femtosecond laser pulses are used to excite coherent optical phonons in single crystal Bi2Te3 thin films. Oscillations from low- and high-frequency A1g phonon modes are observed. A perturbation model based on molecular dynamics reveals various possibilities of phonon generation due to complex interactions among different phonon modes. In order to elucidate the process of phonon generation, measurements on thin films with thicknesses below the optical absorption depth are carried out, showing that a gradient force is necessary to excite the observed A1g phonon modes, which provides a refined picture of displacive excitation of coherent phonon.

  20. 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.

  1. Excitability and optical pulse generation in semiconductor lasers driven by resonant tunneling diode photo-detectors.

    PubMed

    Romeira, Bruno; Javaloyes, Julien; Ironside, Charles N; Figueiredo, José M L; Balle, Salvador; Piro, Oreste

    2013-09-09

    We demonstrate, experimentally and theoretically, excitable nanosecond optical pulses in optoelectronic integrated circuits operating at telecommunication wavelengths (1550 nm) comprising a nanoscale double barrier quantum well resonant tunneling diode (RTD) photo-detector driving a laser diode (LD). When perturbed either electrically or optically by an input signal above a certain threshold, the optoelectronic circuit generates short electrical and optical excitable pulses mimicking the spiking behavior of biological neurons. Interestingly, the asymmetric nonlinear characteristic of the RTD-LD allows for two different regimes where one obtain either single pulses or a burst of multiple pulses. The high-speed excitable response capabilities are promising for neurally inspired information applications in photonics.

  2. 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.

  3. 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.

  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. Inactivation of viruses by coherent excitations with a low power visible femtosecond laser

    PubMed Central

    Tsen, KT; Tsen, Shaw-Wei D; Chang, Chih-Long; Hung, Chien-Fu; Wu, T-C; Kiang, Juliann G

    2007-01-01

    Background Resonant microwave absorption has been proposed in the literature to excite the vibrational states of microorganisms in an attempt to destroy them. But it is extremely difficult to transfer microwave excitation energy to the vibrational energy of microorganisms due to severe absorption of water in this spectral range. We demonstrate for the first time that, by using a visible femtosecond laser, it is effective to inactivate viruses such as bacteriophage M13 through impulsive stimulated Raman scattering. Results and discussion By using a very low power (as low as 0.5 nj/pulse) visible femtosecond laser having a wavelength of 425 nm and a pulse width of 100 fs, we show that M13 phages were inactivated when the laser power density was greater than or equal to 50 MW/cm2. The inactivation of M13 phages was determined by plaque counts and had been found to depend on the pulse width as well as power density of the excitation laser. Conclusion Our experimental findings lay down the foundation for an innovative new strategy of using a very low power visible femtosecond laser to selectively inactivate viruses and other microorganisms while leaving sensitive materials unharmed by manipulating and controlling with the femtosecond laser system. PMID:17550590

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. New infrared photon absorption processes

    SciTech Connect

    Bayfield, J.E.

    1993-05-01

    The fast ionization of atoms by very short laser pulses, and its possible suppression at extreme pulse intensities, is an active new field of investigation at present. Described is an investigation of whether past techniques for infrared laser multiphoton ionization of excited hydrogen atoms and of one-dimensional microwave ionization of highly excited hydrogen atoms can be combined and extended to address the new issues. Although technically difficult and requiring further improvement of apparatus, intense-field infrared laser experiments on excited hydrogen atoms are possible and can directly test theoretical and numerical results.

  12. 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

  13. 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.

  14. 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.

  15. 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

  16. 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.

  17. 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.

  18. Infrared coronal emission lines and the possibility of their laser emission in Seyfert nuclei

    NASA Technical Reports Server (NTRS)

    Greenhouse, Matthew A.; Feldman, Uri; Smith, Howard A.; Klapisch, Marcel; Bhatia, Anand K.; Bar-Shalom, Avi

    1993-01-01

    Results are presented from detailed balance calculations, and a compilation of atomic data and other model calculations designed to support upcoming ISO and current observing programs involving IR coronal emission lines, together with a table with a complete line list of infrared transitions within the ground configurations 2s2 2p(k), 3s2 3p(k), and the first excited configurations 2s 2p and 3s 3p of highly ionized astrophysically abundant elements. The temperature and density parameter space for dominant cooling via IR coronal lines is presented, and the relationship of IR and optical coronal lines is discussed. It is found that, under physical conditions found in Seyfert nuclei, 14 of 70 transitions examined have significant population inversions in levels that give rise to IR coronal lines. Several IR coronal line transitions were found to have laser gain lengths that correspond to column densities of 10 exp 24-25/sq cm which are modeled to exist in Seyfert nuclei. Observations that can reveal inverted level populations and laser gain in IR coronal lines are suggested.

  19. Controlling the coulomb explosion of silver clusters by femtosecond dual-pulse laser excitation.

    PubMed

    Döppner, T; Fennel, Th; Diederich, Th; Tiggesbäumker, J; Meiwes-Broer, K H

    2005-01-14

    Silver clusters grown in helium nanodroplets are excited by intense femtosecond laser pulses resulting in the formation of a hot electron plasma far from equilibrium. The ultrafast dynamics is studied by applying optically delayed dual pulses, which allows us to pursue and control the coupling of the laser field to the clusters on a femtosecond time scale. A distinct influence of the optical delay on the ionization efficiency gives strong evidence that a significant contribution of collective dipolar electron motion is present, which is verified by corresponding Vlasov dynamics simulations on a model system. The microscopic approach demonstrates the outstanding role of giant resonances in clusters also in intense laser fields.

  20. 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.

  1. 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.

  2. Red emitting monolithic dual wavelength DBR diode lasers for shifted excitation Raman difference spectroscopy

    NASA Astrophysics Data System (ADS)

    Sumpf, B.; Maiwald, M.; Müller, A.; Bugge, F.; Fricke, J.; Ressel, P.; Pohl, J.; Erbert, G.; Tränkle, G.

    2014-02-01

    Raman lines are often obscured by background light or fluorescence especially when investigating biological samples or samples containing impurities. Shifted excitation Raman difference spectroscopy (SERDS) is a technique to overcome this. By exciting the sample with two slightly shifted wavelengths, it is possible to separate the Raman lines and distortions. In this paper, monolithic dual wavelength DBR diode lasers meeting the demands of Raman spectroscopy and SERDS will be presented. The wavelengths are stabilized and selected by using deeply-etched 10th order surface gratings with different periods manufactured using i-line wafer stepper lithography. Two possible resonator concepts, i.e. a mini-array of two parallel DBR RW-lasers and a Y-branch DBR laser, will be compared. Established excitation wavelengths for Raman spectroscopy at 671 nm and 785 nm are chosen. The total laser length is 3 mm; the ridge width is 2.2 μm for the 785 nm devices and 5 μm for the 671 nm lasers. The length of the DBR gratings is 500 μm. The devices at 671 nm reach output powers up to 100 mW having an emission width smaller than 12 pm (FWHM). The 785 nm lasers show output powers up to 200 mW and a narrow emission below 22 pm. For the dual wavelength lasers the spectral distance between the two excitation lines is about 0.5 nm as targeted. The power consumption at both wavelengths is below 1 W. These data proof that the devices are well suited for their application in portable Raman measurement systems such as handheld devices using SERDS.

  3. Two-photon absorption cross section of excited phthalocyanines by a femtosecond Ti-sapphire laser.

    PubMed

    Mir, Youssef; van Lier, Johan E; Allard, Jean-François; Morris, Denis; Houde, Daniel

    2009-03-01

    In the past few years, photodynamic therapy (PDT) has become a major treatment for neovascular age-related macular degeneration (AMD) in which there is abnormal growth of choroidal neovasculature (CNV) that eventually obscures central vision, leading to blindness. However, one of the main limitations of current PDT is the relatively low specificity of the photosensitizer (PS) and light for pathological tissue which may induce damage to adjacent healthy tissue. An alternative approach to circumvent the specificity limitation is to improve the irradiation process. In particular two photon (2-gamma) excitation promises a more precise illumination of the target tissue. PS are activated by the simultaneous absorption of 2-gamma delivered by ultra-fast pulses of near infrared light. In order to evaluate the efficiency of phthalocyanine (Pc) dyes for 2-gamma absorption we measured 2-gamma absorption cross sections (sigma(2)) of a number of metalated Pc (MPc) dyes at lambda(ex) = 800 nm using a femtosecond laser. The studied Pc molecules vary by the type of the central metal ion (Al or Zn) and the number of peripheral sulfo substituents (MPcS). Each MPc dye of our series shows an improved 2-gamma absorption sigma(2) as compared to that obtained for Photofrin (3.1 +/- 0.1 GM, with 1 GM = 10(-50) cm(4) s photon(-1) mol(-1)), the PS currently approved for 1-gamma PDT. Our data show an 2.5-fold enhancement for AlPcCl, AlPcS(2adj) and ZnPcS(3)C(9), up to 10-fold (28.6 +/- 0.72 GM) for the ZnPcS(4) dye relative to Photofrin. These findings confirm the efficiency of Pc for 2-gamma absorption processes and represent the first detailed comparison study of 2-gamma absorption sigma(2) between Photofrin and Pc dyes.

  4. 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.

  5. 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

  6. 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…

  7. 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…

  8. 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.

  9. Laser-assisted synthesis of diamond crystals in open air through vibrational excitation of precursor molecules

    NASA Astrophysics Data System (ADS)

    Xie, Z. Q.; Zhou, Y. S.; He, X. N.; Gao, Y.; Park, J. B.; Guillemet, T.; Lu, Y. F.

    2011-03-01

    Fast growth of diamond crystals in open air was achieved by laser-assisted combustion synthesis through vibrational excitation of precursor molecules. A wavelength-tunable CO2 laser (spectrum range from 9.2 to 10.9 μm) was used for the vibrational excitation in synthesis of diamond crystals. A pre-mixed C2H4/C2H2/O2 gas mixture was used as precursors. Through resonant excitation of the CH2-wagging mode of ethylene (C2H4) molecules using the CO2 laser tuned at 10.532 Μm, high-quality diamond crystals were grown on silicon substrates with a high growth rate of ~139 μm/hr. Diamond crystals with a length up to 5 mm and a diameter of 1 mm were grown in 36 hours. Sharp Raman peaks at 1332 cm-1 with full width at half maximum (FWHM) values around 4.5 cm-1 and distinct X-ray diffraction spectra demonstrated the high quality of the diamond crystals. The effects of the resonant excitation of precursor molecules by the CO2 laser were investigated using optical emission spectroscopy.

  10. Excitation of monochromatic and stable electron acoustic wave by two counter-propagating laser beams

    NASA Astrophysics Data System (ADS)

    Xiao, C. Z.; Liu, Z. J.; Zheng, C. Y.; He, X. T.

    2017-07-01

    The undamped electron acoustic wave is a newly-observed nonlinear electrostatic plasma wave and has potential applications in ion acceleration, laser amplification and diagnostics due to its unique frequency range. We propose to make the first attempt to excite a monochromatic and stable electron acoustic wave (EAW) by two counter-propagating laser beams. The matching conditions relevant to laser frequencies, plasma density, and electron thermal velocity are derived and the harmonic effects of the EAW are excluded. Single-beam instabilities, including stimulated Raman scattering and stimulated Brillouin scattering, on the excitation process are quantified by an interaction quantity, η =γ {τ }B, where γ is the growth rate of each instability and {τ }B is the characteristic time of the undamped EAW. The smaller the interaction quantity, the more successfully the monochromatic and stable EAW can be excited. Using one-dimensional Vlasov-Maxwell simulations, we excite EAW wave trains which are amplitude tunable, have a duration of thousands of laser periods, and are monochromatic and stable, by carefully controlling the parameters under the above conditions.

  11. 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.

  12. 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.

  13. 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.

  14. Electron spectra from ionizing collisions in a dense laser-excited Na beam.

    NASA Astrophysics Data System (ADS)

    Babenko, E.; Ramos, G.; Smith, W. W.

    2000-06-01

    We report low-energy (<=4 eV) electron spectra from collision processes occurring in a high density (10^12 - 10^13/cm^3), laser-excited atomic beam. Very different spectra are seen, depending on which states are laser populated. When the 3p_3/2 and 3d_5/2 states are stepwise excited at low intensity, two main electron peaks are seen, attributed to photoionization and Penning ionization.(H.Dengel, M.W.Ruf and H.Hotop, Europhysics Letters 23), 567 (1993). At higher, saturating intensity in our dense beam, we see multiple peaks, with the extra peaks attributed to 3p+3d associative ionization(AI)(E.Babenko, C.Tapalian and W.W.Smith, Chem. Phys. Lett. 244), 121 (1995). and superelastic electron scattering from excited states. The main, broad AI peak at 1.1 eV reflects the vibrorotational distribution of the product Na_2^+ dimer ions, consistent with a simple long-range model of the collision process. A broad, low energy peak at 0.35 eV is tentatively attributed to excitation of the dissociative ^2Σ_u^+ state of the Na_2^+ dimer. Analogous spectra were taken when the 3p and 5s states were selectively laser excited.

  15. Thermal response of nanocomposite materials under pulsed laser excitation

    SciTech Connect

    Rashidi-Huyeh, Majid; Palpant, Bruno

    2004-10-15

    The optical properties of nanocomposite materials made of matrix-embedded noble metal nanoparticles strongly depend on thermal effects from different origins. We propose a classical model describing the energy exchanges within the nanoparticles and between the latter and the surrounding dielectric host subsequent to a light pulse absorption. This model, which accounts for the thermal interactions between neighboring particles, allows us to calculate numerically the temperature dynamics of the electrons, metal lattice and matrix as functions of particle size, and metal concentration of the medium, whatever be the pulsed excitation temporal regime. It is illustrated in the case of Au:SiO{sub 2} materials under femtosecond and nanosecond pulse excitation. It is shown that, in the femtosecond regime, the heat transfer to the matrix cannot be neglected beyond a few picosecond delay from which particle size and metal concentration play a significant role in the electron relaxation. In the nanosecond regime, these morphologic parameters influence crucially the material thermal behavior with the possibility of generating a thermal lens effect. The implications in the analysis of experimental results regarding both the electron relaxation dynamics and the nonlinear optical properties are also discussed. Finally, a method to adapt the model to the case of thin nanocomposite film is proposed.

  16. 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.

  17. Fast Infrared Chemical Imaging with a Quantum Cascade Laser

    PubMed Central

    2015-01-01

    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. PMID:25474546

  18. Theoretical operational life study of the closed-cycle transversely excited atmospheric CO2 laser

    NASA Astrophysics Data System (ADS)

    Hokazono, Hirokazu; Obara, Minoru; Midorikawa, Katsumi; Tashiro, Hideo

    1991-05-01

    The operational characteristics of a high-power closed-cycle transversely excited atmospheric CO2 laser are investigated kinetically. The fractional CO2/N2, molecules decomposition, and concentration of minor impurities accumulated in the laser gas mixture are calculated theoretically as a function of shots and number of repetitive discharge pulses. It is shown that the laser output peak power decreases in proportion to the fractional CO2 decomposition, while nitrogen oxides are found to show little effect on the operational E/N. The theoretical model employed specifies that a trace of water vapor in the laser chamber suppresses the CO2 decomposition due to fact that CO2 reforming is enhanced by OH radicals. As far as ultraviolet preionization is concerned, its absorption depth of the laser gas mixture decreases as the CO2 decomposition increases.

  19. 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.

  20. 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.

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

    NASA Astrophysics Data System (ADS)

    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 (Currad +) and solvated electron esol- 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. Currad + could be transferred into neutral radical of Cur (Currad ) via deprotonation with the pKa 4.13. The excited singlet of Cur (1Cur*) could be transferred into excited triplet (3Cur*), which could be quenched by oxygen to produce singlet oxygen 1O2∗. Reaction of 3Cur* with tryptophan was confirmed. The results encourage developing curcumin as a photosensitive antitumor agent.

  2. 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

  3. 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

  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. Compact, High Power, Multi-Spectral Mid-Infrared Semiconductor Laser Package

    DTIC Science & Technology

    2001-10-01

    Pumped (OP) type-II lasers The optically pumped laser devices were tested by pumping with 980 nm diode laser . Figure 29 shows the typical...Choi, and D. A. Coppeta "High-power diode - laser - pumped InAsSb/GaSb and GaInAsSb/GaSb lasers emitting from 3 to 4 µm" Appl. Phys. Lett. 64, 152 (1994...Arias, M. Zandian, R. R. Zucca, and Y.-Z. Liu "High-power diode - pumped mid-infrared semiconductor lasers ," Proc. SPIE 2382, 262

  6. 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.

  7. 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.

  8. 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.

  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. Laboratory analysis of techniques for remote sensing of estuarine parameters using laser excitation

    NASA Technical Reports Server (NTRS)

    Exton, R. J.; Houghton, W. M.; Esaias, W.; Harriss, R. C.; Farmer, F. H.; White, H. H.

    1983-01-01

    The theoretical concepts underlying remote sensing of estuarine parameters using laser excitation are examined. The concepts are extended to include Mie scattering as a measure of the total suspended solids and to develop the water Raman signal as an internal standard. Experimental validation of the theory was performed using backscattered laser light from a laboratory tank to simulate a remote-sensing geometry. Artificially prepared sediments and biological cultures were employed to check specific aspects of the theory under controlled conditions. Natural samples gathered from a variety of water types were also analyzed in the tank to further enhance the simulation. The results indicate that it should be possible to remotely quantify total suspended solids, dissolved organics, attenuation coefficient, chlorophyll a, and phycoerythrin in estuarine water using laser excitation.

  13. Laser-induced fluorescence detection of hydroxyl (OH) radical by femtosecond excitation.

    PubMed

    Stauffer, Hans U; Kulatilaka, Waruna D; Gord, James R; Roy, Sukesh

    2011-05-15

    The development of a laser-induced fluorescence detection scheme for probing combustion-relevant species using a high-repetition-rate ultrafast laser is described. A femtosecond laser system with a 1 kHz repetition rate is used to induce fluorescence, following two-photon excitation (TPE), from hydroxyl (OH) radicals that are present in premixed laminar flames. The experimental TPE and one-photon fluorescence spectra resulting from broadband excitation into the (0,0) band of the OH A(2)∑(+)-X(2)Π system are compared to simulated spectra. Additionally, the effects of non-transform-limited femtosecond pulses on TPE efficiency is investigated. © 2011 Optical Society of America

  14. 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.

  15. 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.

  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. Infrared Lunar Laser Ranging at Calern : Impact on Lunar Dynamics

    NASA Astrophysics Data System (ADS)

    Viswanathan, Vishnu; Fienga, Agnes; Manche, Herve; Gastineau, Mickael; Courde, Clement; Torre, Jean Marie; Exertier, Pierre; Laskar, Jacques

    2017-04-01

    Introduction: 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 [1]. Dataset: 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 [2]. Data reduction: IERS recommended models have been used in the data reduction software GINS (GRGS,CNES) [3]. Constraints provided by GRAIL [4], on the Lunar gravitational potential and Love numbers have been taken into account in the least-square fit procedure. Earth orientation parameters from KEOF series have been used as per a recent study [5]. Results: New estimates on the dynamical parameters of the lunar core will be presented. Acknowledgements: We thank the lunar laser ranging observers at Observatoire de la Côte d'Azur, France, McDonald Observatory, Texas, Haleakala Observatory, Hawaii, and Apache Point Observatory in New Mexico for providing LLR observations that made this study possible. The research described in this abstract was carried out at Geoazur-CNRS, France, as a part of a PhD thesis funded by Observatoire de Paris and French Ministry of Education and Research. References: [1] Clement C. et al. (2016) submitted to A&A [2] Fienga A. et al. (2015) Celest Mech Dyn Astr, 123: 325. doi:10.1007/s10569-015-9639-y [3] Viswanathan V. et al. (2015) EGU, Abstract 18, 13995 [4] Konopliv A. S. et al. (2013) J. Geophys. Res. Planets, 118, 1415

  18. 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.

  19. 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.

  20. 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.