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Ultrashort Pulse Excitation of Dense Upconversion Media

Stephen Colby Rand

Published Nov 10, 1997• 0 citations
OpenAlex

Abstract

Abstract : This project was initiated to identify conditions in dense upconversion media under which ultrashort pulses could lead to new applications. Four main results were obtained. First, a new channel for the generation of ultraviolet upconversion emission in Erbium-doped compounds was discovered. Second, an extremely promising imaging technique which relies on time-gated, ultrafast upconversion was demonstrated. Third, induced nonlinear response in dense upconversion materials was shown to be primarily dispersive in nature, even for resonant interactions, and we were able to explain how this apparently contradictory behavior arises. This revealed for the first time that cooperative nonlinearities could be useful in lossless, ultrafast applications. Fourth, a local mode of Yb in CsCdBr3 crystals was identified with properties which should permit coherent control of upconversion by ultrashort pulses.

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Ultrashort Pulses in Multicomponent Media and Photonic Bandgap Structures

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Abstract : The mathematical algorithms and programs for the study of the resonant light-matter interactions in the multi-component and multilevel media and photonic bandgap structures have been developed. The optimal component distribution in the two-component media have been found to get a pulse of a superradiative emission of the highest intensity. The mathematical algorithms and programs for the study of the femtosecond pulse propagation in an extended medium of the two-level atoms have developed. The regime of the inversionless superradiance in the two-component superradiative medium has been investigated. The theory of the superradiance by an ensemble of the two-level atoms embedded in the dielectric host was developed. It was shown that the near dipole-dipole interaction of dense collection of two-level atoms is enhanced by the presence of the host material, decreasing the pulse temporal width and increasing the peak pulse intensity of superradiative emission. The theory of nonlinear light-matter interaction in multidimensional resonant photonic crystals under Bragg diffraction condition has been developed. It was obtained the analytical and numerical solutions describing the novel kinds of nonlinear solitary waves: the Laue soliton, O-field, propagating and standing gap solitary waves. It has been described the spatio-temporal nonlinear dynamics of coherent field in periodic resonant structures with arbitrary modulation of atomic density and gain gratings.

•Feb 17, 1998•0 citations

Ultrashort Optical Pulses and Their Generation in Resonant Media (Scientific Summary)

Rostislav M. Arkhipov, Mikhail V. Arkhipov, A. A. Shimko +2 more

Our recent studies of methods for obtaining ultrashort light pulses and analysis of the impact of ultrashort optical pulses on classical and quantum micro-objects with the identification of the determining role of the degree of unipolarity of pulses (maximum for strictly unipolar pulses) in the efficiency of direct laser acceleration of charged particles and excitation of atoms and molecules have been reviewed. Special attention has been paid to the coherent mode locking regime in lasers, which is implemented when the laser pulse duration is less than the relaxation time of the working transition in media with resonance amplification and absorption (laser analog of the phenomenon of self-induced transparency). Experimental data on coherent mode locking in a titanium-sapphire laser with a cell with rubidium vapor at self-induced transparency in rubidium have been presented. The interaction of ultrashort pulses in resonant media has also been analyzed.

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Frontiers in Nonlinear Optics

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FOREWORD by N. Bloembergen NONLINEAR OPTICS Channeling of atoms in a standing laser light wave by V.I. Balykin et al. Optical nonlinearities and the Kerr effect in phaseonium by U. Rathe et al. Spectroscopic studies in the far ultraviolet (80-200nm) using nonlinear tunable sources by B.P. Stoicheff CARS in plasma physics by M. Lefebvre et al. Velocity distribution of electrons for tunnel ionization by a light field with polar asymmetry by N.B. Baranova and B. Ya Zel'dovich NONLINEAR OPTICS IN CONDENSED MEDIA Hot carriers in semiconductors studied via picosecond optical nonlinearities in the infrared by T. Elsasser and W. Kaiser Non-local time-resolved spectroscopy-tracking of polariton pulses in crystals by Ch Flytzanis et al. Self trapping of optical beams in photorefractive media by M. Segev et al. Solitons in quantum nonlinear optics by R.Y. Chiao et al. Femtosecond dynamics of third-order nonlinearities in polythiophenes by A Cybo-Ottone et al. NEW DEVICES AND TECHNOLOGY Nonlinear generation of sub-psec pulses of THz electromagnetic radiation by optoelectronics-applications to time-domain spectroscopy by D. Grischkowsky Novel nonlinear optical techniques for studying chiral molecules of biological importance by N.I. Koroteev Coupled nonlinear cavities: new avenues to ultrashort pulses by F. Mitschke et al. Transverse rotating waves in nonlinear optical systems with spatial and temporal delay by N.G. Iroshnikov and M.A. Vorontsov The effect of intraspectral harmonics correlation of broad-band fields on the excitation of quantum resonance systems by A.M. Bonch-Bruevich and S.B. Przhibelskii Injection-locked femtosecond parametric oscillators in LBO crystals by V.M. Gordienko et al. INDEX

CRC Press eBooks•Jul 16, 2021•7 citations

Ultrafast Cooperative Phenomena in Coherently Prepared Media: From Superfluorescence to Coherent Raman Scattering and Applications

Ariunbold Gombojav

Technological progress in commercializing ultrafast lasers and detectors has allowed realization of cooperative processes on an ultrashort time scale, which demand a re-evaluation of the conventional cooperative phenomena with a new insight. Ultrafast cooperative phenomena in coherently prepared media and various applications of superfluorescence and coherent Raman scattering are studied in this dissertation. In particular, a simple theoretical testimony on analogy between a cooperative emission and coherent Raman scattering is presented by offering an opportunity to perform parallel research on these two processes from a unified point of view.\n\nOn one hand, the superfluorescent pulse with a time duration of a few tens of picoseconds (ps) from alkali metal vapor is observed for the first time, even though cooperative phenomena in atomic vapor have been extensively studied for more than five decades. A dense rubidium vapor pumped by ultrashort (100 femtosecond, fs) pulses allows a realization of the ultrafast superfluorescence while a time-resolved study of superfluorescence is accomplished by using a streak camera with 2 ps time resolution. Experimental research on quantum nature of cooperative emissions has been “frozen” over the years (three decades) possibly because of the technical difficulties. Quantum fluctuations of superfluorescence development are explored experimentally by taking advantage of the ultra fast streak camera. Presumable applications of the superfluorescent pulse in e.g., a remote sensing, and an ultraviolet upconversion of the input infrared laser pulse are presented. The quantum interference due to different excitation pathways is revealed by the temporal coherent control technique while observing interferometric signals from alkali metal vapors. \n\nOn the other hand, a new spectroscopic technique based on ultrafast coherent Raman scattering is developed. The key advantage of the presented technique is to suppress the non-resonant background noise which usually obscures possible applications of the other conventional coherent Raman techniques in practice. A reduction of the background noise is achieved by shaping and delaying the third pulse which probes the coherence of the medium (i.e., an enhancement of specific vibrations of the target molecules in unison) firstly prepared by two broadband pulses. We demonstrate a robustness and superiority of signal-to-noise ratio of the developed technique by identifying as few as 10000 bacterial spores at a single laser shot level.\n\nFinally, several comparative studies between cooperative and uncooperative processes are presented. A picosecond cooperative phenomenon in a three-photon resonant medium induced by a single as well as two-color ultrashort pulses is investigated. A time-resolved study shows that a picosecond cooperative effect is crucial in the well-established fields of resonant-enhanced multiphoton ionizations and harmonic generations. We also present a quantitative analysis for spontaneous versus broadband coherent Raman scattering on pyridine molecules. The spontaneous Raman signal is enhanced by 5 orders as a result of cooperative phenomena.

•Jan 1, 2011•4 citations

Continuous-wave, cooperative upconversion lasers.

Ping Xie

Continuous-wave lasers in which the emitted photon energy may be up to three times greater than that of the incident pump light by virtue of cooperative (coupled atom) upconversion processes are reported for the first time in this thesis. Cw upconversion laser action was obtained at wavelengths of 0.55$\mu$m, 0.70$\mu$m, 0.85$\mu$m and 2.8$\mu$m using infrared excitation in the range $\lambda$ = 1.48-1.70$\mu$m in concentrated crystals of Er:CaF$\sb2$ and Er:LiYF$\sb4$. Detailed aspects of the behavior and internal dynamics of these systems have been considered both experimentally and theoretically in this work. Two limiting approaches were applied to gain theoretical insight into possible unique features of cooperative upconversion lasers. These corresponded to strong and weak coupling theories. A density matrix approach describing the strong coupling limit predicted several new results of cooperative interactions, including enhanced quantum efficiency, enhanced energy transfer, and cooperative instabilities. A rate equation analysis appropriate to weaker coupling was used to confirm that cooperative upconversion lasers can operate continuously on self-terminating transitions and established threshold conditions for pair- and trio-pumped lasers. Time dependent upconversion fluorescence measurements were performed to investigate the pumping mechanism of the new lasers experimentally. These observations and measurement of the intensity dependence of upconversion emission established that the inversion mechanism was exclusively cooperative in nature. Upconversion laser instabilities were also studied and related to nonlinear, cooperative dynamics. Unique features of cooperative upconversion lasers were identified, compared with other upconversion pumping schemes, and exploited to demonstrate the first cw mode-locked solid state laser operating in the visible spectral range. On the basis of this work, it may be concluded that cooperative upconversion provides a practical means of generating coherent radiation in new spectral regions, even on self-terminating transitions.

•Jan 1, 1992•1 citation

Coherent Cooperative Radiation in Solids

Stephen Colby Rand

Avalanche upconversion dynamics and associated nonlinear optical response was also reported for the first time in Tm:YALO crystals at room temperature. The avalanche mechanism involves a cooperative down conversion (cross relaxation) step and is a promising method of pumping rare earth lasers at entirely new (diode compatible) wavelengths, corresponding to excited state absorptions rather than ground state absorptions. Quantum theory describing the threshold for photo-darkening and the role of energy migration in avalanches was developed, and semi quantitative agreement obtained with preliminary measurements of nonlinear susceptibilities. Cooperative dynamics in general, and avalanche dynamics in particular, were shown to furnish a promising new mechanism not only for solid state lasers but for nonlinear optical interactions as well, opening the door to practical signal processing and switching applications exploiting the low intensity thresholds of avalanche processes.

Michigan Univ. Final Report•Oct 30, 1991•0 citations
Abstract : This project was initiated to identify conditions in dense upconversion media under which ultrashort pulses could lead to new applications. Four main results were obtained. First, a new channel for the generation of ultraviolet upconversion emission in Erbium-doped compounds was discovered. Second, an extremely promising imaging technique which relies on time-gated, ultrafast upconversion was demonstrated. Third, induced nonlinear response in dense upconversion materials was shown to be primarily dispersive in nature, even for resonant interactions, and we were able to explain how this apparently contradictory behavior arises. This revealed for the first time that cooperative nonlinearities could be useful in lossless, ultrafast applications. Fourth, a local mode of Yb in CsCdBr3 crystals was identified with properties which should permit coherent control of upconversion by ultrashort pulses.
Abstract : The mathematical algorithms and programs for the study of the resonant light-matter interactions in the multi-component and multilevel media and photonic bandgap structures have been developed. The optimal component distribution in the two-component media have been found to get a pulse of a superradiative emission of the highest intensity. The mathematical algorithms and programs for the study of the femtosecond pulse propagation in an extended medium of the two-level atoms have developed. The regime of the inversionless superradiance in the two-component superradiative medium has been investigated. The theory of the superradiance by an ensemble of the two-level atoms embedded in the dielectric host was developed. It was shown that the near dipole-dipole interaction of dense collection of two-level atoms is enhanced by the presence of the host material, decreasing the pulse temporal width and increasing the peak pulse intensity of superradiative emission. The theory of nonlinear light-matter interaction in multidimensional resonant photonic crystals under Bragg diffraction condition has been developed. It was obtained the analytical and numerical solutions describing the novel kinds of nonlinear solitary waves: the Laue soliton, O-field, propagating and standing gap solitary waves. It has been described the spatio-temporal nonlinear dynamics of coherent field in periodic resonant structures with arbitrary modulation of atomic density and gain gratings.
Our recent studies of methods for obtaining ultrashort light pulses and analysis of the impact of ultrashort optical pulses on classical and quantum micro-objects with the identification of the determining role of the degree of unipolarity of pulses (maximum for strictly unipolar pulses) in the efficiency of direct laser acceleration of charged particles and excitation of atoms and molecules have been reviewed. Special attention has been paid to the coherent mode locking regime in lasers, which is implemented when the laser pulse duration is less than the relaxation time of the working transition in media with resonance amplification and absorption (laser analog of the phenomenon of self-induced transparency). Experimental data on coherent mode locking in a titanium-sapphire laser with a cell with rubidium vapor at self-induced transparency in rubidium have been presented. The interaction of ultrashort pulses in resonant media has also been analyzed.
FOREWORD by N. Bloembergen NONLINEAR OPTICS Channeling of atoms in a standing laser light wave by V.I. Balykin et al. Optical nonlinearities and the Kerr effect in phaseonium by U. Rathe et al. Spectroscopic studies in the far ultraviolet (80-200nm) using nonlinear tunable sources by B.P. Stoicheff CARS in plasma physics by M. Lefebvre et al. Velocity distribution of electrons for tunnel ionization by a light field with polar asymmetry by N.B. Baranova and B. Ya Zel'dovich NONLINEAR OPTICS IN CONDENSED MEDIA Hot carriers in semiconductors studied via picosecond optical nonlinearities in the infrared by T. Elsasser and W. Kaiser Non-local time-resolved spectroscopy-tracking of polariton pulses in crystals by Ch Flytzanis et al. Self trapping of optical beams in photorefractive media by M. Segev et al. Solitons in quantum nonlinear optics by R.Y. Chiao et al. Femtosecond dynamics of third-order nonlinearities in polythiophenes by A Cybo-Ottone et al. NEW DEVICES AND TECHNOLOGY Nonlinear generation of sub-psec pulses of THz electromagnetic radiation by optoelectronics-applications to time-domain spectroscopy by D. Grischkowsky Novel nonlinear optical techniques for studying chiral molecules of biological importance by N.I. Koroteev Coupled nonlinear cavities: new avenues to ultrashort pulses by F. Mitschke et al. Transverse rotating waves in nonlinear optical systems with spatial and temporal delay by N.G. Iroshnikov and M.A. Vorontsov The effect of intraspectral harmonics correlation of broad-band fields on the excitation of quantum resonance systems by A.M. Bonch-Bruevich and S.B. Przhibelskii Injection-locked femtosecond parametric oscillators in LBO crystals by V.M. Gordienko et al. INDEX
Technological progress in commercializing ultrafast lasers and detectors has allowed realization of cooperative processes on an ultrashort time scale, which demand a re-evaluation of the conventional cooperative phenomena with a new insight. Ultrafast cooperative phenomena in coherently prepared media and various applications of superfluorescence and coherent Raman scattering are studied in this dissertation. In particular, a simple theoretical testimony on analogy between a cooperative emission and coherent Raman scattering is presented by offering an opportunity to perform parallel research on these two processes from a unified point of view.\n\nOn one hand, the superfluorescent pulse with a time duration of a few tens of picoseconds (ps) from alkali metal vapor is observed for the first time, even though cooperative phenomena in atomic vapor have been extensively studied for more than five decades. A dense rubidium vapor pumped by ultrashort (100 femtosecond, fs) pulses allows a realization of the ultrafast superfluorescence while a time-resolved study of superfluorescence is accomplished by using a streak camera with 2 ps time resolution. Experimental research on quantum nature of cooperative emissions has been “frozen” over the years (three decades) possibly because of the technical difficulties. Quantum fluctuations of superfluorescence development are explored experimentally by taking advantage of the ultra fast streak camera. Presumable applications of the superfluorescent pulse in e.g., a remote sensing, and an ultraviolet upconversion of the input infrared laser pulse are presented. The quantum interference due to different excitation pathways is revealed by the temporal coherent control technique while observing interferometric signals from alkali metal vapors. \n\nOn the other hand, a new spectroscopic technique based on ultrafast coherent Raman scattering is developed. The key advantage of the presented technique is to suppress the non-resonant background noise which usually obscures possible applications of the other conventional coherent Raman techniques in practice. A reduction of the background noise is achieved by shaping and delaying the third pulse which probes the coherence of the medium (i.e., an enhancement of specific vibrations of the target molecules in unison) firstly prepared by two broadband pulses. We demonstrate a robustness and superiority of signal-to-noise ratio of the developed technique by identifying as few as 10000 bacterial spores at a single laser shot level.\n\nFinally, several comparative studies between cooperative and uncooperative processes are presented. A picosecond cooperative phenomenon in a three-photon resonant medium induced by a single as well as two-color ultrashort pulses is investigated. A time-resolved study shows that a picosecond cooperative effect is crucial in the well-established fields of resonant-enhanced multiphoton ionizations and harmonic generations. We also present a quantitative analysis for spontaneous versus broadband coherent Raman scattering on pyridine molecules. The spontaneous Raman signal is enhanced by 5 orders as a result of cooperative phenomena.
Continuous-wave lasers in which the emitted photon energy may be up to three times greater than that of the incident pump light by virtue of cooperative (coupled atom) upconversion processes are reported for the first time in this thesis. Cw upconversion laser action was obtained at wavelengths of 0.55μ\muμm, 0.70μ\muμm, 0.85μ\muμm and 2.8μ\muμm using infrared excitation in the range λ\lambdaλ = 1.48-1.70μ\muμm in concentrated crystals of Er:CaF$\sb2$ and Er:LiYF$\sb4$. Detailed aspects of the behavior and internal dynamics of these systems have been considered both experimentally and theoretically in this work. Two limiting approaches were applied to gain theoretical insight into possible unique features of cooperative upconversion lasers. These corresponded to strong and weak coupling theories. A density matrix approach describing the strong coupling limit predicted several new results of cooperative interactions, including enhanced quantum efficiency, enhanced energy transfer, and cooperative instabilities. A rate equation analysis appropriate to weaker coupling was used to confirm that cooperative upconversion lasers can operate continuously on self-terminating transitions and established threshold conditions for pair- and trio-pumped lasers. Time dependent upconversion fluorescence measurements were performed to investigate the pumping mechanism of the new lasers experimentally. These observations and measurement of the intensity dependence of upconversion emission established that the inversion mechanism was exclusively cooperative in nature. Upconversion laser instabilities were also studied and related to nonlinear, cooperative dynamics. Unique features of cooperative upconversion lasers were identified, compared with other upconversion pumping schemes, and exploited to demonstrate the first cw mode-locked solid state laser operating in the visible spectral range. On the basis of this work, it may be concluded that cooperative upconversion provides a practical means of generating coherent radiation in new spectral regions, even on self-terminating transitions.
Avalanche upconversion dynamics and associated nonlinear optical response was also reported for the first time in Tm:YALO crystals at room temperature. The avalanche mechanism involves a cooperative down conversion (cross relaxation) step and is a promising method of pumping rare earth lasers at entirely new (diode compatible) wavelengths, corresponding to excited state absorptions rather than ground state absorptions. Quantum theory describing the threshold for photo-darkening and the role of energy migration in avalanches was developed, and semi quantitative agreement obtained with preliminary measurements of nonlinear susceptibilities. Cooperative dynamics in general, and avalanche dynamics in particular, were shown to furnish a promising new mechanism not only for solid state lasers but for nonlinear optical interactions as well, opening the door to practical signal processing and switching applications exploiting the low intensity thresholds of avalanche processes.