P. Venkateswarlu, M. George, Y. Rao, H. Jagannath, G. Chakrapani
Transient excited singlet state absorption spectrum of the laser dye, α-NPO (8 × 10-5 M/liter in toluene) was recorded in the 4500-6200 Å region with an optical delay of ~ 3 ns between the pump and the probe beams. Nine maxima and three shoulders are observed for the first time in the spectrum. A shoulder at 21090 cm-1 and three maxima at 20,530, 18,685, and 17,980 cm-1 are tentatively attributed to transitions from the vibrational levels at 26,740, 27,350, 29,170, and 29,885 cm-1 belonging to the first excited singlet electronic state S1, respectively, to a common upper level at 47,855 ± 25 cm-1 while three other maxima at 20,035, 19,525, and 17,570 cm-1 and another shoulder at 16,945 cm-1 are attributed, respectively, to transitions from the same four vibrational levels of S1 to another common upper level at 46,805 ± 70 cm-1. Transitions from the different vibrational levels of S1 to three different upper vibrational levels at 47,645 ± 30, 43,130, and 48,760 cm-1 could similarly be assigned to the remaining three maxima at 20,320, 18,445, and 16,390 cm-1 and the shoulder at 22,020 cm-1. Absorption from the higher vibrational levels of the excited state S1 may be understood on the basis of the fact that the pump and probe beams, each of ~ 8-ns pulse width, interact simultaneously with the molecules for ~ 5 ns.
{"title":"Transient excited singlet state absorption in the laser dye α-NPO","authors":"P. Venkateswarlu, M. George, Y. Rao, H. Jagannath, G. Chakrapani","doi":"10.1063/1.36769","DOIUrl":"https://doi.org/10.1063/1.36769","url":null,"abstract":"Transient excited singlet state absorption spectrum of the laser dye, α-NPO (8 × 10-5 M/liter in toluene) was recorded in the 4500-6200 Å region with an optical delay of ~ 3 ns between the pump and the probe beams. Nine maxima and three shoulders are observed for the first time in the spectrum. A shoulder at 21090 cm-1 and three maxima at 20,530, 18,685, and 17,980 cm-1 are tentatively attributed to transitions from the vibrational levels at 26,740, 27,350, 29,170, and 29,885 cm-1 belonging to the first excited singlet electronic state S1, respectively, to a common upper level at 47,855 ± 25 cm-1 while three other maxima at 20,035, 19,525, and 17,570 cm-1 and another shoulder at 16,945 cm-1 are attributed, respectively, to transitions from the same four vibrational levels of S1 to another common upper level at 46,805 ± 70 cm-1. Transitions from the different vibrational levels of S1 to three different upper vibrational levels at 47,645 ± 30, 43,130, and 48,760 cm-1 could similarly be assigned to the remaining three maxima at 20,320, 18,445, and 16,390 cm-1 and the shoulder at 22,020 cm-1. Absorption from the higher vibrational levels of the excited state S1 may be understood on the basis of the fact that the pump and probe beams, each of ~ 8-ns pulse width, interact simultaneously with the molecules for ~ 5 ns.","PeriodicalId":422579,"journal":{"name":"International Laser Science Conference","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115375140","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Zhe Chen, P. Sheng, D. Weitz, H. M. Lindsay, M. Y. Lin, P. Meakin
Optical scattering and absorption characteristics of fractal clusters are calculated with a self-consistent scheme in which the multiple scattering and local field effects are treated exactly in the dipole approximation. Our results indicate that for optical scattering the gold colloidal aggregates with fractal dimension D = 1.75 behave essentially as low dimensional objects and therefore can be accurately described by the (single-scattering) Born approximation. However, the absorption spectrum of the clusters is shown to be significantly affected by the proximity of the gold particles to their nearest neighbors in the aggregate structure. Comparison with experimental data is shown.
{"title":"Optical properties of fractal clusters","authors":"Zhe Chen, P. Sheng, D. Weitz, H. M. Lindsay, M. Y. Lin, P. Meakin","doi":"10.1063/1.36738","DOIUrl":"https://doi.org/10.1063/1.36738","url":null,"abstract":"Optical scattering and absorption characteristics of fractal clusters are calculated with a self-consistent scheme in which the multiple scattering and local field effects are treated exactly in the dipole approximation. Our results indicate that for optical scattering the gold colloidal aggregates with fractal dimension D = 1.75 behave essentially as low dimensional objects and therefore can be accurately described by the (single-scattering) Born approximation. However, the absorption spectrum of the clusters is shown to be significantly affected by the proximity of the gold particles to their nearest neighbors in the aggregate structure. Comparison with experimental data is shown.","PeriodicalId":422579,"journal":{"name":"International Laser Science Conference","volume":"88 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124999882","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We present results of laser-induced desorption experiments on layers of CO and NO physisorbed at low temperatures (5–40 K) on fire-polished alumina substrates. The radiation source is a linetunable CO laser capable of operating on over 400 lines in the 1500–1900-cm−1 region with a cw output power on the strong lines of 0.3–0.5 W. The experiments are carried out in a bakable UHV chamber with coverages of about a monolayer. The desorbed molecules are detected with a quadrupole mass analyzer operating in a time-of-flight mode. The desorption yields from both molecules show a broad, nonresonant (wavelength-independent) behavior. Additionally, NO shows a strongly resonant peak at 1843 cm−1 that we attribute to the direct excitation of the NO stretch mode. Effective temperatures for the desorbed molecules are obtained by fitting the time-of-flight data to a Boltzmann distribution. These vary from approximately the substrate temperature to 10–20 K higher, depending on the laser fluence and the substrate temperature.
{"title":"Infrared laser-induced desorption of NO and CO from alumina substrates","authors":"W. Weber, B. D. Poindexter","doi":"10.1063/1.36744","DOIUrl":"https://doi.org/10.1063/1.36744","url":null,"abstract":"We present results of laser-induced desorption experiments on layers of CO and NO physisorbed at low temperatures (5–40 K) on fire-polished alumina substrates. The radiation source is a linetunable CO laser capable of operating on over 400 lines in the 1500–1900-cm−1 region with a cw output power on the strong lines of 0.3–0.5 W. The experiments are carried out in a bakable UHV chamber with coverages of about a monolayer. The desorbed molecules are detected with a quadrupole mass analyzer operating in a time-of-flight mode. The desorption yields from both molecules show a broad, nonresonant (wavelength-independent) behavior. Additionally, NO shows a strongly resonant peak at 1843 cm−1 that we attribute to the direct excitation of the NO stretch mode. Effective temperatures for the desorbed molecules are obtained by fitting the time-of-flight data to a Boltzmann distribution. These vary from approximately the substrate temperature to 10–20 K higher, depending on the laser fluence and the substrate temperature.","PeriodicalId":422579,"journal":{"name":"International Laser Science Conference","volume":"57 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115538998","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In laser Doppler velocimetry, two laser beams are crossed within a sample. Interference between the two beams generates a set of light and dark fringes within the intersection region of the beams. A particle passing through the fringe region will generate a modulated light scatter signal. Conventionally, the modulation frequency of the light scatter signal is used to estimate the velocity of the particles. However, the modulated light scatter signal generated by laser Doppler velocimetry also provides excellent noise immunity for particle size determination. To utilize the light scatter signal for precise particle size determination, it is necessary to align particles to pass through the center of the fringe region. We utilize the sheath flow cuvette to produce a thin stream of particulate suspension at the center of the interference fringe region. For polystyrene particles in water, the relative standard deviation of the light scatter distributions typically falls in the 1-2% range and is dominated by the intrinsic size distribution of the particle standards. Particles as small as 40-nm radius may be studied using a low-power He-Cd laser.
{"title":"Laser Doppler velocimetry for submicrometer particle size determination","authors":"N. Dovichi, F. Zarrin","doi":"10.1063/1.36754","DOIUrl":"https://doi.org/10.1063/1.36754","url":null,"abstract":"In laser Doppler velocimetry, two laser beams are crossed within a sample. Interference between the two beams generates a set of light and dark fringes within the intersection region of the beams. A particle passing through the fringe region will generate a modulated light scatter signal. Conventionally, the modulation frequency of the light scatter signal is used to estimate the velocity of the particles. However, the modulated light scatter signal generated by laser Doppler velocimetry also provides excellent noise immunity for particle size determination. To utilize the light scatter signal for precise particle size determination, it is necessary to align particles to pass through the center of the fringe region. We utilize the sheath flow cuvette to produce a thin stream of particulate suspension at the center of the interference fringe region. For polystyrene particles in water, the relative standard deviation of the light scatter distributions typically falls in the 1-2% range and is dominated by the intrinsic size distribution of the particle standards. Particles as small as 40-nm radius may be studied using a low-power He-Cd laser.","PeriodicalId":422579,"journal":{"name":"International Laser Science Conference","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114397312","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A KrF excimer laser with a fluence of 50 mJ/cm2 was used to photolyze either uranium hexafluoride or molecular fluorine, yielding a transient number density of fluorine atoms. The rise and decay of the atomic fluorine density was observed by transient absorption of a 404-cm−1 Pb-salt diode laser, which corresponds to the 2P3/2 → 2P1/2 spin-orbital transition in atomic fluorine. To prevent the diode laser wavelength from drifting out of resonance with the atomic fluorine line, part of the beam was split off and sent through a microwave discharge fluorine atom cell. This allowed a wavelength modulation-feedback technique to be used to lock the diode laser wavelength onto the atomic line. The remaining diode laser beam was made collinear with the excimer laser beam using a LiF window with a 45° angle of incidence to reflect the infrared beam while transmitting most of the UV beam. Using this setup along with a transient digitizer to average between 100 and 200 transient absorption profiles, fluorine atom number densities of the order of 1014/cm−3 in a 3-m path length were detected. The signals observed were about a factor of 5 less than expected from known photolysis cross sections.
{"title":"Detection of transient fluorine atoms","authors":"G. Loge, N. Nereson, H. Fry","doi":"10.1063/1.36799","DOIUrl":"https://doi.org/10.1063/1.36799","url":null,"abstract":"A KrF excimer laser with a fluence of 50 mJ/cm2 was used to photolyze either uranium hexafluoride or molecular fluorine, yielding a transient number density of fluorine atoms. The rise and decay of the atomic fluorine density was observed by transient absorption of a 404-cm−1 Pb-salt diode laser, which corresponds to the 2P3/2 → 2P1/2 spin-orbital transition in atomic fluorine. To prevent the diode laser wavelength from drifting out of resonance with the atomic fluorine line, part of the beam was split off and sent through a microwave discharge fluorine atom cell. This allowed a wavelength modulation-feedback technique to be used to lock the diode laser wavelength onto the atomic line. The remaining diode laser beam was made collinear with the excimer laser beam using a LiF window with a 45° angle of incidence to reflect the infrared beam while transmitting most of the UV beam. Using this setup along with a transient digitizer to average between 100 and 200 transient absorption profiles, fluorine atom number densities of the order of 1014/cm−3 in a 3-m path length were detected. The signals observed were about a factor of 5 less than expected from known photolysis cross sections.","PeriodicalId":422579,"journal":{"name":"International Laser Science Conference","volume":"132 ","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114006079","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The possibility of a practically total reduction of quantum photon fluctuations in cw laser radiation is discussed. This effect appears as a result of two-photon radiation absorption using a resonance transition in atoms excited from the ground state to the upper level, relaxing to the other states. For this case the possibility of induced two-photon emission is excluded, that is, the source of additional photon number fluctuations in a field mode.1 In this process the Fock states with the photon number n ≥ 2 are continuously reduced from the coherent state of the excited field. For the large time values of interaction the Fock states |n = 0 > and |n = 1> remain in the field. The effect of spin orientations of photons of the excited field on the quantum noise reduction process for the two-photon absorption by atoms on the transitions between the S → S and S → D terms is analyzed. The possibility of transformation of coherent and thermal fields (λ ≃ 6022 Å and λ = 5787 Å) into quasi-Fock states, as a result of its two-photon resonance absorption by Na homogeneous vapor, is considered.
{"title":"Transformation of coherent states of the electromagnetic field to quasi-Fock states","authors":"V. Zakharov","doi":"10.1063/1.36846","DOIUrl":"https://doi.org/10.1063/1.36846","url":null,"abstract":"The possibility of a practically total reduction of quantum photon fluctuations in cw laser radiation is discussed. This effect appears as a result of two-photon radiation absorption using a resonance transition in atoms excited from the ground state to the upper level, relaxing to the other states. For this case the possibility of induced two-photon emission is excluded, that is, the source of additional photon number fluctuations in a field mode.1 In this process the Fock states with the photon number n ≥ 2 are continuously reduced from the coherent state of the excited field. For the large time values of interaction the Fock states |n = 0 > and |n = 1> remain in the field. The effect of spin orientations of photons of the excited field on the quantum noise reduction process for the two-photon absorption by atoms on the transitions between the S → S and S → D terms is analyzed. The possibility of transformation of coherent and thermal fields (λ ≃ 6022 Å and λ = 5787 Å) into quasi-Fock states, as a result of its two-photon resonance absorption by Na homogeneous vapor, is considered.","PeriodicalId":422579,"journal":{"name":"International Laser Science Conference","volume":"200 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114751467","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The sideband instability of free-electron laser (FEL) oscillators has recently been observed1 in the Los Alamos experiments. This result underscores the expected need for sideband suppression in tapered-undulator oscillators. While the instability is predicted to actually enhance the power output of untapered systems, it is a possible threat to the potential high extraction of tapered systems. Simulations2 predict that the instability will lead to detrapping in FELs with relatively long, highly tapered undulators in which trapped electrons undergo multiple synchrotron oscillations while traversing the undulator. Sideband growth is associated with loss of extraction by one-half or more. Means for sideband suppression using multilayer dielectric mirror coatings are investigated. The objective is to identify filter functions which give adequate sideband suppression. It is found that the introduction of wavelength selectivity can suppress the instability, with recovery of full extraction.
{"title":"Prevention of sideband-induced detrapping in tapered-undulator free-electron lasers","authors":"D. Quimby","doi":"10.1063/1.36715","DOIUrl":"https://doi.org/10.1063/1.36715","url":null,"abstract":"The sideband instability of free-electron laser (FEL) oscillators has recently been observed1 in the Los Alamos experiments. This result underscores the expected need for sideband suppression in tapered-undulator oscillators. While the instability is predicted to actually enhance the power output of untapered systems, it is a possible threat to the potential high extraction of tapered systems. Simulations2 predict that the instability will lead to detrapping in FELs with relatively long, highly tapered undulators in which trapped electrons undergo multiple synchrotron oscillations while traversing the undulator. Sideband growth is associated with loss of extraction by one-half or more. Means for sideband suppression using multilayer dielectric mirror coatings are investigated. The objective is to identify filter functions which give adequate sideband suppression. It is found that the introduction of wavelength selectivity can suppress the instability, with recovery of full extraction.","PeriodicalId":422579,"journal":{"name":"International Laser Science Conference","volume":"45 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127931451","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A two-step methodology is presented for extracting ground state population distributions and alignment factors from 1 + 1 resonance-enhanced multiphoton ionization (REMPI) spectra. In the first step the ion signal is corrected for variation with laser intensity on a shot-to-shot basis, generating an isopower spectrum. In the second step populations and alignments are derived from the isopower spectrum by correcting for the interdependent effects of saturation and intermediate state alignment. Both classical and quantum-mechanical models are presented and their attributes are noted. This analysis procedure is applied to a room temperature thermal distribution of nitric oxide using the 1 + 1 REMPI process in which lines of the NO A2Σ+—X2Π (0,0) band constitute the resonant transition. The present treatment is able to recover the known rovibrational population distribution, independent of branch choice, over a wide range of practical operating conditions.
{"title":"Reduction of 1 + 1 REMPI spectra to population distributions: saturation and intermediate state alignment effects","authors":"D. C. Jacobs, R. Madix, R. Zare","doi":"10.1063/1.36768","DOIUrl":"https://doi.org/10.1063/1.36768","url":null,"abstract":"A two-step methodology is presented for extracting ground state population distributions and alignment factors from 1 + 1 resonance-enhanced multiphoton ionization (REMPI) spectra. In the first step the ion signal is corrected for variation with laser intensity on a shot-to-shot basis, generating an isopower spectrum. In the second step populations and alignments are derived from the isopower spectrum by correcting for the interdependent effects of saturation and intermediate state alignment. Both classical and quantum-mechanical models are presented and their attributes are noted. This analysis procedure is applied to a room temperature thermal distribution of nitric oxide using the 1 + 1 REMPI process in which lines of the NO A2Σ+—X2Π (0,0) band constitute the resonant transition. The present treatment is able to recover the known rovibrational population distribution, independent of branch choice, over a wide range of practical operating conditions.","PeriodicalId":422579,"journal":{"name":"International Laser Science Conference","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115784503","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The time-averaged width of individual longitudinal modes of a multimode XeCl discharge laser oscillator was measured using time-delayed interferometry, a technique related to Fourier-transform spectroscopy. The beam from the laser was divided by the beam splitter of a Michelson interferometer. The arms of the interferometer were adjusted so that their lengths differed by an integral multiple of the laser cavity length. Interferograms were recorded using a CID camera and a videocassette recorder. Measurements of the interference fringe visibility, made at path length differences of up to three times the cavity length, were used to calculate the width of the longitudinal modes, averaged over the laser pulse. The width inferred in this way exceeds the transform-limited width by a factor of 7. This discrepancy is attributed to the time-varying refractive index of the gain medium, which causes the resonant frequencies of the optical cavity to change during the laser pulse. This phenomenon limits the temporal coherence of such lasers, unless a compensating change is made in the cavity length. The time-dependent populations of the atomic and molecular levels predicted by a computer model of the discharge plasma were used to calculate the refractive index. The principal cause of the refractive- index change was found to be the dissociation of HCl. A simple model of the effect of the time-varying refractive index on the laser frequency predicts fringe visibilities in good agreement with measured values.
{"title":"Longitudinal mode width in excimer lasers","authors":"G. Lombardi, W. Long","doi":"10.1063/1.36861","DOIUrl":"https://doi.org/10.1063/1.36861","url":null,"abstract":"The time-averaged width of individual longitudinal modes of a multimode XeCl discharge laser oscillator was measured using time-delayed interferometry, a technique related to Fourier-transform spectroscopy. The beam from the laser was divided by the beam splitter of a Michelson interferometer. The arms of the interferometer were adjusted so that their lengths differed by an integral multiple of the laser cavity length. Interferograms were recorded using a CID camera and a videocassette recorder. Measurements of the interference fringe visibility, made at path length differences of up to three times the cavity length, were used to calculate the width of the longitudinal modes, averaged over the laser pulse. The width inferred in this way exceeds the transform-limited width by a factor of 7. This discrepancy is attributed to the time-varying refractive index of the gain medium, which causes the resonant frequencies of the optical cavity to change during the laser pulse. This phenomenon limits the temporal coherence of such lasers, unless a compensating change is made in the cavity length. The time-dependent populations of the atomic and molecular levels predicted by a computer model of the discharge plasma were used to calculate the refractive index. The principal cause of the refractive- index change was found to be the dissociation of HCl. A simple model of the effect of the time-varying refractive index on the laser frequency predicts fringe visibilities in good agreement with measured values.","PeriodicalId":422579,"journal":{"name":"International Laser Science Conference","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131015660","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The material TAS is a ternary chalcogenide salt with space group symmetry R3m, transparent between 1.3 and 17μm. Its large nonlinear optic coefficient and high damage threshold make TAS a promising candidate for nonlinear frequency conversion processes throughout the infrared.1 Recently, large, good quality crystals of TAS have been grown, cut, polished, and coated for CO2 laser second harmonic conversion by Westinghouse Research Laboratory. At NRL, a 2.5-cm diam 6-cm long crystal was pumped by a Lumonics 822 H P CO2 laser operating on the 9-μm P(20) transition with energy of 350 mJ in a 100 ns FWHM pulse. In type I doubling conditions, we have observed up to 25% total energy conversion to the second harmonic at 1 J/cm2 with no apparent crystal damage. Additionally, in a second similar TAS crystal we have observed both type I and type II sum frequency generation to the third harmonic with an overall total energy conversion of 1.5%. Progress toward a TAS-based OPO in the 8-12-μm range is also reported. (12min)
材料TAS为三元硫系盐，空间基对称R3m，透明度在1.3 ~ 17μm之间。大的非线性光学系数和高的损伤阈值使TAS成为整个红外非线性变频过程的一个有希望的候选者近年来，美国西屋研究实验室(Westinghouse Research Laboratory)在CO2激光二次谐波转换中制备出了大尺寸、高质量的TAS晶体。在NRL, Lumonics 822 hp CO2激光器以100 ns FWHM脉冲以350 mJ的能量在9 μm P(20)跃迁上泵浦一个直径为2.5 cm、长为6 cm的晶体。在I型倍增条件下，我们观察到高达25%的总能量转换为1 J/cm2的二次谐波，没有明显的晶体损伤。此外，在第二个类似的TAS晶体中，我们观察到I型和II型的频率产生总和为三次谐波，总能量转换为1.5%。还报道了8-12 μm范围内基于tas的OPO的进展。(12分钟)
{"title":"Efficient harmonic generation of CO2 laser radiation in thallium arsenic selenide","authors":"R. Auyeung, D. Zielke, B. Feldman","doi":"10.1063/1.36865","DOIUrl":"https://doi.org/10.1063/1.36865","url":null,"abstract":"The material TAS is a ternary chalcogenide salt with space group symmetry R3m, transparent between 1.3 and 17μm. Its large nonlinear optic coefficient and high damage threshold make TAS a promising candidate for nonlinear frequency conversion processes throughout the infrared.1 Recently, large, good quality crystals of TAS have been grown, cut, polished, and coated for CO2 laser second harmonic conversion by Westinghouse Research Laboratory. At NRL, a 2.5-cm diam 6-cm long crystal was pumped by a Lumonics 822 H P CO2 laser operating on the 9-μm P(20) transition with energy of 350 mJ in a 100 ns FWHM pulse. In type I doubling conditions, we have observed up to 25% total energy conversion to the second harmonic at 1 J/cm2 with no apparent crystal damage. Additionally, in a second similar TAS crystal we have observed both type I and type II sum frequency generation to the third harmonic with an overall total energy conversion of 1.5%. Progress toward a TAS-based OPO in the 8-12-μm range is also reported. (12min)","PeriodicalId":422579,"journal":{"name":"International Laser Science Conference","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130751935","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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