We report the results of experiments demonstrating stimulated Brillouin scattering (SBS) and phase conjugation of a single-line HF laser. The 2.91 μm was selected by an intracavity grating yielding up to 3J in a 1.5-μS pulse. The flat-flat optical cavity was carefully aligned to maximize far-field intensity and the resulting spot diameter was found to be near the diffraction limit. The magnified far-field intensity profiles were imaged with film burns and with a linear pyroelectric array. This high spatial quality beam was intentionally distorted by passing it through a roughened NaCl window and the distortion was verified by examining the far-field intensity profile. This distorted beam was then focused into a cell containing xenon at 45 atm. The resulting SBS reflection passed back through the NaCl aberrator and the diffraction-limited far-field intensity profile of this reflected beam was found to be restored. This demonstration of random phase aberration and reconstruction of the laser beam provides evidence that the SBS reflection is the phase conjugate of the input beam. (12min)
{"title":"Phase conjugation of 2.91-μm HF laser radiation via stimulated Brillouin scattering","authors":"M. Duignan, B. Feldman, W. Whitney","doi":"10.1063/1.36864","DOIUrl":"https://doi.org/10.1063/1.36864","url":null,"abstract":"We report the results of experiments demonstrating stimulated Brillouin scattering (SBS) and phase conjugation of a single-line HF laser. The 2.91 μm was selected by an intracavity grating yielding up to 3J in a 1.5-μS pulse. The flat-flat optical cavity was carefully aligned to maximize far-field intensity and the resulting spot diameter was found to be near the diffraction limit. The magnified far-field intensity profiles were imaged with film burns and with a linear pyroelectric array. This high spatial quality beam was intentionally distorted by passing it through a roughened NaCl window and the distortion was verified by examining the far-field intensity profile. This distorted beam was then focused into a cell containing xenon at 45 atm. The resulting SBS reflection passed back through the NaCl aberrator and the diffraction-limited far-field intensity profile of this reflected beam was found to be restored. This demonstration of random phase aberration and reconstruction of the laser beam provides evidence that the SBS reflection is the phase conjugate of the input beam. (12min)","PeriodicalId":422579,"journal":{"name":"International Laser Science Conference","volume":"11 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":"127053184","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}
W. Luh, J. Bahns, K. Sando, A. Lyyra, P. Kleiber, W. Stwalley
Direct dye laser excitation of the K2 yellow (566-580-nm), Rb2 orange (590-610-nm) and Cs2 near-infrared (702-722-nm) diffuse bands has been investigated. Experimental results are consistent with 2 3 Π g (bound) ← 1 3 Σ u + (free) excitation followed by bound → free fluorescence. For Rb2 and Cs2, spin-orbit interactions become so significant that the 23Π g state is strongly split into three independent component states and this is observed in the spectra. We have investigated the free-bound-free fluorescence of the K2 yellow diffuse band in particular detail. Theoretical treatment and quantum-mechanical simulation of free-bound-free resonance fluorescence are described for comparison with our single longitudinal mode dye laser direct excitation experiments and measurements of the weak absorption in the same spectral region.
{"title":"Studies of the diffuse bands of K2, Rb2, and Cs2","authors":"W. Luh, J. Bahns, K. Sando, A. Lyyra, P. Kleiber, W. Stwalley","doi":"10.1063/1.36773","DOIUrl":"https://doi.org/10.1063/1.36773","url":null,"abstract":"Direct dye laser excitation of the K2 yellow (566-580-nm), Rb2 orange (590-610-nm) and Cs2 near-infrared (702-722-nm) diffuse bands has been investigated. Experimental results are consistent with \u0000 \u0000 \u0000 \u0000 2\u0000 3\u0000 \u0000 \u0000 Π\u0000 g\u0000 \u0000 (bound)\u0000 ←\u0000 \u0000 1\u0000 3\u0000 \u0000 \u0000 Σ\u0000 u\u0000 +\u0000 \u0000 (free)\u0000 \u0000 \u0000 excitation followed by bound → free fluorescence. For Rb2 and Cs2, spin-orbit interactions become so significant that the 23Π\u0000 g\u0000 state is strongly split into three independent component states and this is observed in the spectra. We have investigated the free-bound-free fluorescence of the K2 yellow diffuse band in particular detail. Theoretical treatment and quantum-mechanical simulation of free-bound-free resonance fluorescence are described for comparison with our single longitudinal mode dye laser direct excitation experiments and measurements of the weak absorption in the same spectral region.","PeriodicalId":422579,"journal":{"name":"International Laser Science Conference","volume":"262 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":"116236434","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 review recent progress in inelastic collisions between two laser-excited alkali atoms, with special emphasis on heteronuclear systems.
本文综述了激光激发碱原子间非弹性碰撞的最新研究进展，特别强调了异核系统。
{"title":"Inelastic collisions in laser excited alkali atoms","authors":"M. Allegrini, S. Gozzini, L. Moi","doi":"10.1063/1.36853","DOIUrl":"https://doi.org/10.1063/1.36853","url":null,"abstract":"We review recent progress in inelastic collisions between two laser-excited alkali atoms, with special emphasis on heteronuclear systems.","PeriodicalId":422579,"journal":{"name":"International Laser Science Conference","volume":"11 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":"121770634","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}
Resonance Raman spectroscopy performed in the 150-300-nm spectral region provides several unique opportunities in molecular spectroscopy and biophysics.1,2 The performance of such experiments in the far-UV region requires optimization of laser technology, nonlinear optical devices, collection efficiency, spectral dispersion, and detection. The construction of a UV resonance Raman spectrometer designed to operate to 150 nm is described. This spectrometer is based on a Q-switched Nd:YAG laser, harmonic generating crystals, and stimulated Raman scattering in hydrogen gas. Reflective optics with backscattering collection are used to focus the Raman scattered light onto the slits of a nitrogen or helium filled vacuum monochromator. The detector is a solar blind photomultiplier with a MgF2 window. The performance of this spectrometer is described.
{"title":"Techniques for far-ultraviolet resonance Raman spectroscopy","authors":"P. Kelly, Shijian Li, G. Strahan, B. Hudson","doi":"10.1063/1.36760","DOIUrl":"https://doi.org/10.1063/1.36760","url":null,"abstract":"Resonance Raman spectroscopy performed in the 150-300-nm spectral region provides several unique opportunities in molecular spectroscopy and biophysics.1,2 The performance of such experiments in the far-UV region requires optimization of laser technology, nonlinear optical devices, collection efficiency, spectral dispersion, and detection. The construction of a UV resonance Raman spectrometer designed to operate to 150 nm is described. This spectrometer is based on a Q-switched Nd:YAG laser, harmonic generating crystals, and stimulated Raman scattering in hydrogen gas. Reflective optics with backscattering collection are used to focus the Raman scattered light onto the slits of a nitrogen or helium filled vacuum monochromator. The detector is a solar blind photomultiplier with a MgF2 window. The performance of this spectrometer is described.","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":"130353947","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}
For long-wavelength (1.3- and 1.5-μm) high-bit-rate (>400-Mbit/s) lightwave systems the highest receiver sensitivities have been achieved with III–V compound avalanche photodiodes with separate absorption and multiplication regions (SAM-APDs). Initial APDs of this type exhibited poor frequency response owing to charge accumulation at the heterojunction interfaces. A significant improvement in the bandwidth was achieved by introducing a transition region between the multiplication and absorption layers (SAGM-APD). Early SAGM-APDs exhibited bandwidths in the 1–3-GHz range and gain-bandwidth products as high as 18 GHz. Recently, the progression of new lightwave systems to higher and higher bit rates has stimulated efforts to further increase the bandwidth of these SAGM-APDs.
{"title":"High gain-bandwidth-product avalanche photodiodes for multigigabit data rate","authors":"J. Campbell","doi":"10.1063/1.36815","DOIUrl":"https://doi.org/10.1063/1.36815","url":null,"abstract":"For long-wavelength (1.3- and 1.5-μm) high-bit-rate (>400-Mbit/s) lightwave systems the highest receiver sensitivities have been achieved with III–V compound avalanche photodiodes with separate absorption and multiplication regions (SAM-APDs). Initial APDs of this type exhibited poor frequency response owing to charge accumulation at the heterojunction interfaces. A significant improvement in the bandwidth was achieved by introducing a transition region between the multiplication and absorption layers (SAGM-APD). Early SAGM-APDs exhibited bandwidths in the 1–3-GHz range and gain-bandwidth products as high as 18 GHz. Recently, the progression of new lightwave systems to higher and higher bit rates has stimulated efforts to further increase the bandwidth of these SAGM-APDs.","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":"129394053","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}
Resonance Raman spectroscopy of heme proteins and the visual pigments has provided valuable insights into the mechanism of action of these proteins. The performance of Raman experiments with ultraviolet radiation permits resonance with nonchromophoric components of proteins including the peptide bond itself.1,2 Fluorescence from the aromatic residues of proteins does not obscure the Raman signal because the fluorescence occurs at longer wavelengths. The peptide bond gives rise to new Raman active bands with ultraviolet excitation.2 The imino linkage of X-proline sequences results in absorption in the 220–240-nm range where normal amino linkages are transparent. This permits the selective excitation of this group relative to the predominant amino peptide bonds. This is of particular interest with respect to the involvement of isomerization of the X-proline linkage in protein folding. Recent results using radiation in the 150–200-nm region are presented.
{"title":"Applications of ultraviolet resonance Raman spectroscopy to protein structure","authors":"L. Mayne, B. Hudson","doi":"10.1063/1.36824","DOIUrl":"https://doi.org/10.1063/1.36824","url":null,"abstract":"Resonance Raman spectroscopy of heme proteins and the visual pigments has provided valuable insights into the mechanism of action of these proteins. The performance of Raman experiments with ultraviolet radiation permits resonance with nonchromophoric components of proteins including the peptide bond itself.1,2 Fluorescence from the aromatic residues of proteins does not obscure the Raman signal because the fluorescence occurs at longer wavelengths. The peptide bond gives rise to new Raman active bands with ultraviolet excitation.2 The imino linkage of X-proline sequences results in absorption in the 220–240-nm range where normal amino linkages are transparent. This permits the selective excitation of this group relative to the predominant amino peptide bonds. This is of particular interest with respect to the involvement of isomerization of the X-proline linkage in protein folding. Recent results using radiation in the 150–200-nm region are presented.","PeriodicalId":422579,"journal":{"name":"International Laser Science Conference","volume":"56 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":"126243465","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 have identified the long debated origin of the short-range component of surface-enhanced Raman scattering (SERS) as Ag 4 + clusters which are stabilized by co-adsorbed molecules or by low substrate temperature on rough Ag surfaces. The assignment has been supported by vibrational mode calculations which include the effects of adsorption of the cluster, image interaction with the metal, and co-adsorbed anions in the electrochemical environment. The observed modes at 73, 110, and 161 cm−1 correspond to those calculated at 75, 100 and 118, and 170 cm−1. The adsorbed clusters act as Lewis acid sites onto which other molecules such as pyridine are bonded thus leading to SERS beyond the usual electromagnetic factor which is due to macroscopic roughness. The mechanism of the added enhancement is through charge transfer excitation between the adsorbed molecules and the clusters and through HOMO—LUMO transitions within the cluster.
{"title":"Silver clusters as the active sites for surface-enhanced Raman scattering","authors":"T. Furtak, D. Roy","doi":"10.1063/1.36737","DOIUrl":"https://doi.org/10.1063/1.36737","url":null,"abstract":"We have identified the long debated origin of the short-range component of surface-enhanced Raman scattering (SERS) as \u0000 \u0000 \u0000 \u0000 \u0000 Ag\u0000 \u0000 4\u0000 +\u0000 \u0000 \u0000 \u0000 clusters which are stabilized by co-adsorbed molecules or by low substrate temperature on rough Ag surfaces. The assignment has been supported by vibrational mode calculations which include the effects of adsorption of the cluster, image interaction with the metal, and co-adsorbed anions in the electrochemical environment. The observed modes at 73, 110, and 161 cm−1 correspond to those calculated at 75, 100 and 118, and 170 cm−1. The adsorbed clusters act as Lewis acid sites onto which other molecules such as pyridine are bonded thus leading to SERS beyond the usual electromagnetic factor which is due to macroscopic roughness. The mechanism of the added enhancement is through charge transfer excitation between the adsorbed molecules and the clusters and through HOMO—LUMO transitions within the cluster.","PeriodicalId":422579,"journal":{"name":"International Laser Science Conference","volume":"21 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":"127504776","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 nonlinear Schrodinger equation arises naturally in a variety of physical processes; in particular, it is fundamentally important to nonlinear optics. Both the analytic and numerical solutions of this equation have been extensively investigated; a recent review by Taha and Ablowitz1 suggests that for soliton propagation problems the method of Hardin and Tapped2 is the superior numerical method. In this paper, the split operator Fourier transform (SOFT) method, originally due to Fleck et al.,3 is demonstrated to be applicable to the nonlinear Schrodinger equation. For the particular soliton problem studied,4 the results obtained with the SOFT method are found to be an order of magnitude more accurate than those obtained with the Hardin-Tappert method.
{"title":"Application of the split operator Fourier transform method to the solution of the nonlinear Schrodinger equation","authors":"P. DeVries","doi":"10.1063/1.36847","DOIUrl":"https://doi.org/10.1063/1.36847","url":null,"abstract":"The nonlinear Schrodinger equation arises naturally in a variety of physical processes; in particular, it is fundamentally important to nonlinear optics. Both the analytic and numerical solutions of this equation have been extensively investigated; a recent review by Taha and Ablowitz1 suggests that for soliton propagation problems the method of Hardin and Tapped2 is the superior numerical method. In this paper, the split operator Fourier transform (SOFT) method, originally due to Fleck et al.,3 is demonstrated to be applicable to the nonlinear Schrodinger equation. For the particular soliton problem studied,4 the results obtained with the SOFT method are found to be an order of magnitude more accurate than those obtained with the Hardin-Tappert method.","PeriodicalId":422579,"journal":{"name":"International Laser Science Conference","volume":"7 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":"123664230","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}
Y. Liu, Q. Zhang, S. C. O'brien, J. Heath, R. Curl, F. Tittel, R. Smalley
We have recently developed an ion source which is capable of producing both positive and negative semiconductor cluster ions cooled by supersonic expansion. Ions of a particular mass are selected and studied by laser photodetachment and photodissociation followed by time-of-flight mass analysis. The electron affinities (EA) of several semiconductor clusters have been measured by photodetachment threshold measurements on their negative ions. For GaAs clusters, an even/odd size alternation in EA is observed as in the ionization potentials of the neutrals, supporting the suggestion that the neutral even clusters have fully paired singlet ground states with no dangling bonds.1,2 Photodissociation studies reveal that negative silicon and germanium cluster ions fragment predominantly into 6–11 atom size clusters with 6–10 being the favorite fragmentation daughters.
{"title":"Photodetachment and photodissociation studies of semiconductor cluster ions","authors":"Y. Liu, Q. Zhang, S. C. O'brien, J. Heath, R. Curl, F. Tittel, R. Smalley","doi":"10.1063/1.36742","DOIUrl":"https://doi.org/10.1063/1.36742","url":null,"abstract":"We have recently developed an ion source which is capable of producing both positive and negative semiconductor cluster ions cooled by supersonic expansion. Ions of a particular mass are selected and studied by laser photodetachment and photodissociation followed by time-of-flight mass analysis. The electron affinities (EA) of several semiconductor clusters have been measured by photodetachment threshold measurements on their negative ions. For GaAs clusters, an even/odd size alternation in EA is observed as in the ionization potentials of the neutrals, supporting the suggestion that the neutral even clusters have fully paired singlet ground states with no dangling bonds.1,2 Photodissociation studies reveal that negative silicon and germanium cluster ions fragment predominantly into 6–11 atom size clusters with 6–10 being the favorite fragmentation daughters.","PeriodicalId":422579,"journal":{"name":"International Laser Science Conference","volume":"15 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":"123694184","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}
Liquid suspensions of microparticles are two-component media with novel electromagnetic properties. For these media, laser-generated electrostrictive forces and torques can modulate the microparticle density and orientation in such a way as to alter the dielectric constant of the composite. In turn, this change gives rise to the formation of microparticle gratings which can serve as a nonlinear medium. For example, suspensions have been utilized to generate phase conjugate radiation in the visible. In addition, self-focusing and optical bistability have also been demonstrated at visible wavelengths. Here we examine the possibility of another nonlinear process occurring in these media; namely, coherent beam combination. Specifically, we examine the nonlinear response of a liquid suspension of microspheres to two nearly degenerate laser beams. These two waves create a moving grating composed of microparticles vibrating at the difference frequency. In turn, this oscillating grating scatters radiation from the higher frequency wave into the lower frequency beam via a process similar to stimulated Raman scattering, with the grating assuming the role of the acoustic wave. For a suspension composed of 10−3 volume fraction of 0.34-µm latex spheres in water, the nonlinear coefficient ϰ = 2.91 cm−3,with/the laser intensity in kW/cm2 at DF wavelenghts.
{"title":"Two-wave mixing in liquid suspensions of microparticles","authors":"R. McGraw, D. Rogovin","doi":"10.1063/1.36753","DOIUrl":"https://doi.org/10.1063/1.36753","url":null,"abstract":"Liquid suspensions of microparticles are two-component media with novel electromagnetic properties. For these media, laser-generated electrostrictive forces and torques can modulate the microparticle density and orientation in such a way as to alter the dielectric constant of the composite. In turn, this change gives rise to the formation of microparticle gratings which can serve as a nonlinear medium. For example, suspensions have been utilized to generate phase conjugate radiation in the visible. In addition, self-focusing and optical bistability have also been demonstrated at visible wavelengths. Here we examine the possibility of another nonlinear process occurring in these media; namely, coherent beam combination. Specifically, we examine the nonlinear response of a liquid suspension of microspheres to two nearly degenerate laser beams. These two waves create a moving grating composed of microparticles vibrating at the difference frequency. In turn, this oscillating grating scatters radiation from the higher frequency wave into the lower frequency beam via a process similar to stimulated Raman scattering, with the grating assuming the role of the acoustic wave. For a suspension composed of 10−3 volume fraction of 0.34-µm latex spheres in water, the nonlinear coefficient ϰ = 2.91 cm−3,with/the laser intensity in kW/cm2 at DF wavelenghts.","PeriodicalId":422579,"journal":{"name":"International Laser Science Conference","volume":"28 6 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":"116715046","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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