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Quantum Electronics and Laser Science Conference

Influence of self-focusing on stimulated Rayleigh-wing scattering and stimulated librational scattering

Edward J. Miller, Robert W. Boyd

Published May 12, 1991• 0 citations

Abstract

Stimulated scattering is a nonlinear process that often results in the generation of a backwardgoing signal. This signal is known to display several unique and interesting properties; perhaps the most notable is phase conjugation. Stimulated Rayleigh-wing scattering (SRWS)1'2 is the stimulated scattering process arising from the optical Kerr effect, and it possesses an extremely fast response time (2 ps in CS2). Under certain experimental conditions, SRWS is known to conjugate both the phase and polarization of an incident field.3 The optical Kerr effect also leads to an intensity-dependent refractive index and is often the dominant contribution to this effect. With a large nonlinear index change, several undesirable effects, such as self-focusing and filamentation,Stimulated scattering is a nonlinear process that often results in the generation of a backwardgoing signal. This signal is known to display several unique and interesting properties; perhaps the most notable is phase conjugation. Stimulated Rayleigh-wing scattering (SRWS)1'2 is the stimulated scattering process arising from the optical Kerr effect, and it possesses an extremely fast response time (2 ps in CS2). Under certain experimental conditions, SRWS is known to conjugate both the phase and polarization of an incident field.3 The optical Kerr effect also leads to an intensity-dependent refractive index and is often the dominant contribution to this effect. With a large nonlinear index change, several undesirable effects, such as self-focusing and filamentation, occur as an intense optical wave propagates through a nonlinear medium.4

Related papers

Polarization Dependence of Stimulated Rayleigh-Wing Scattering and the Optical-Frequency Kerr Effect

Rikon Chao, John Godine

A theoretical study of the polarization dependence of stimulated Rayleigh-wing scattering and the optical-frequency Kerr effect has been undertaken. When the incident light is circularly polarized, a striking difference in gain is found for the co- and counter-rotating senses of polarization of the scattered light---the former being suppressed and the latter being exceptionally favored. The analysis begins with a model for the Kerr effect, which involves the alignment of anisotropic molecules in an electric field, but the results can be immediately generalized to any light scattering process of tensor symmetry. The nonlinear problem of the propagation of an intense elliptically polarized light wave in a Kerr-active medium is shown to have a solution in which the vibrational ellipse undergoes self-precession and self-retardation. The stimulated scatterings or instabilities of such a self-precessing and self-retarding light wave are obtained for the backward and forward directions. Birefringence, optical activity, and linear and circular dichroisms are some of the phenomena which result, but the forward direction yields substantially different results from the backward direction because of Stokes-anti-Stokes coupling.

Physical Review•Sep 10, 1969•56 citations

Saturation Effects in Stimulated Rayleigh-Wing Scattering

R. M. Herman

The phenomenon of stimulated Rayleigh-wing scattering in anisotropic molecular liquids is analyzed. Representative combinations of polarization for the incident and scattered light are considered. It is shown that in regions where the focused laser beam is intense, saturation occurs in the molecular response to external optical fields, in that perfect alignment of the individual liquid molecules in the optical fields is approached. Accordingly, the nonlinear amplification associated with the stimulated radiation is reduced. The results of the analysis qualitatively explain several important recent observations which are in conflict with previous theroretical predictions. For example, it is shown that the nonlinear gain is considerably greater when the incident light is circularly polarized (the stimulated radiation being circularly polarized in the reverse sense) than it is when the incident light is linearly polarized. Despite saturation, sufficient amplification exists in the former case to allow the efficient conversion of incident to stimulated Rayleigh light at moderate power levels.

Physical Review•Dec 5, 1967•16 citations

Stimulated Rayleigh wing scattering with Bessel beam pumping

R. Barillé, Suren Sogomonian, Genevieve Rivoire

We have observed SRWS without phase modulation and self focusing of the pump beam with use of a Bessel beam excitation. The experiments show at the scattering threshold two types of line spectra, and above the threshold a large band spectrum. These results are interpreted by the presence of four photon processes coupling two exciting photons, one Stokes and one anti-Stokes scattered photon, developing in cascade. This interpretation can be extended to the recent studies of soliton propagation in a planar waveguide.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•Dec 29, 1999•0 citations

Stimulated Rayleigh-Bragg scattering in a three-photon absorbing medium and its phase-conjugation property

Guang S. He, Qingdong Zheng, Paras N. Prasad

We show that the backward-stimulated Rayleigh-Bragg scattering (SRBS) can be efficiently generated in a three-photon absorbing medium. Compared with all other known stimulated (such as Brillouin and Raman) scattering effects, the observed effect exhibits the following three features: (i) no frequency shift, (ii) a lower pump threshold, and (iii) no critical requirement for pump spectral linewidths within a range of Δv¯≤1cm−1. The specific nonlinear scattering medium is a three-photon absorbing chromophore solution (PRL-OT04 in chloroform), pumped by 1064nm laser pulses of nanoseconds duration but with three different spectral linewidths. The mechanism for generating backward SRBS in a three-photon active medium is the formation of a stationary Bragg grating enhanced by three-photon-absorption-associated refractive index changes. A superior optical phase-conjugation property of the backward SRBS beam has been experimentally demonstrated by employing two different optical setups. In both cases, a specially introduced aberration influence of 4-5 mrad can be basically removed by the backward SRBS beam that retains a much smaller beam divergence of ≤0.4 mrad.

Journal of the Optical Society of America B•Apr 17, 2007•9 citations

Spatial and spectral properties of stimulated Rayleigh-wing scattering pumped with a Bessel beam:role of four-photon parametric processes

R. Barillé, Suren Sogomonian, Genevieve Rivoire

Stimulated Rayleigh-wing scattering is studied here in various liquids excited with a Bessel beam that allows a complete spatial separation between the transmitted exciting light and the scattered light. The results show that a large Stokes spectral band displaying substructures is obtained in the absence of self-focusing, cross-focusing, self-phase modulation, and cross-phase modulation. An interpretation is proposed based on the role of cascade Stokes–anti-Stokes coupled scattering processes.

Journal of the Optical Society of America B•Jul 1, 1999•4 citations

Two-photon absorption induced stimulated Rayleigh-Bragg scattering

Guang S. He, Paras N. Prasad

A frequency-unshifted and backward stimulated scattering can be efficiently generated in one-photon-absorption free but two-photon absorbing materials. Using a number of novel two-photon absorbing dye solutions as the scattering media and nanosecond pulsed laser as the pump beams, a highly directional backward stimulated scattering at the exact pump wavelength can be readily observed once the pump intensity is higher than a certain threshold level. The spectral and spatial structures as well as the temporal behavior and optical phase-conjugation property of this new type of backward stimulated scattering have been experimentally studied. This stimulated scattering phenomenon can be explained by using a model of two-photon-excitation enhanced standing-wave Bragg grating initially formed by the strong forward pump beam and much weaker backward Rayleigh scattering beam; the partial reflection of the pump beam from this grating provides an positive feedback to the initial backward Rayleigh scattering beam without suffering linear attenuation influence. Comparing to other known stimulated (Raman, Brillouin, Rayleigh-wing, and Kerr) scattering effects, the stimulated Rayleigh-Bragg scattering exhibits the advantages of no frequency-shift, low pump threshold, and low spectral linewidth requirement.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•Jan 28, 2005•1 citation

Stimulated scattering is a nonlinear process that often results in the generation of a backwardgoing signal. This signal is known to display several unique and interesting properties; perhaps the most notable is phase conjugation. Stimulated Rayleigh-wing scattering (SRWS)1'2 is the stimulated scattering process arising from the optical Kerr effect, and it possesses an extremely fast response time (2 ps in CS2). Under certain experimental conditions, SRWS is known to conjugate both the phase and polarization of an incident field.3 The optical Kerr effect also leads to an intensity-dependent refractive index and is often the dominant contribution to this effect. With a large nonlinear index change, several undesirable effects, such as self-focusing and filamentation,Stimulated scattering is a nonlinear process that often results in the generation of a backwardgoing signal. This signal is known to display several unique and interesting properties; perhaps the most notable is phase conjugation. Stimulated Rayleigh-wing scattering (SRWS)1'2 is the stimulated scattering process arising from the optical Kerr effect, and it possesses an extremely fast response time (2 ps in CS2). Under certain experimental conditions, SRWS is known to conjugate both the phase and polarization of an incident field.3 The optical Kerr effect also leads to an intensity-dependent refractive index and is often the dominant contribution to this effect. With a large nonlinear index change, several undesirable effects, such as self-focusing and filamentation, occur as an intense optical wave propagates through a nonlinear medium.4

A theoretical study of the polarization dependence of stimulated Rayleigh-wing scattering and the optical-frequency Kerr effect has been undertaken. When the incident light is circularly polarized, a striking difference in gain is found for the co- and counter-rotating senses of polarization of the scattered light---the former being suppressed and the latter being exceptionally favored. The analysis begins with a model for the Kerr effect, which involves the alignment of anisotropic molecules in an electric field, but the results can be immediately generalized to any light scattering process of tensor symmetry. The nonlinear problem of the propagation of an intense elliptically polarized light wave in a Kerr-active medium is shown to have a solution in which the vibrational ellipse undergoes self-precession and self-retardation. The stimulated scatterings or instabilities of such a self-precessing and self-retarding light wave are obtained for the backward and forward directions. Birefringence, optical activity, and linear and circular dichroisms are some of the phenomena which result, but the forward direction yields substantially different results from the backward direction because of Stokes-anti-Stokes coupling.

The phenomenon of stimulated Rayleigh-wing scattering in anisotropic molecular liquids is analyzed. Representative combinations of polarization for the incident and scattered light are considered. It is shown that in regions where the focused laser beam is intense, saturation occurs in the molecular response to external optical fields, in that perfect alignment of the individual liquid molecules in the optical fields is approached. Accordingly, the nonlinear amplification associated with the stimulated radiation is reduced. The results of the analysis qualitatively explain several important recent observations which are in conflict with previous theroretical predictions. For example, it is shown that the nonlinear gain is considerably greater when the incident light is circularly polarized (the stimulated radiation being circularly polarized in the reverse sense) than it is when the incident light is linearly polarized. Despite saturation, sufficient amplification exists in the former case to allow the efficient conversion of incident to stimulated Rayleigh light at moderate power levels.

We have observed SRWS without phase modulation and self focusing of the pump beam with use of a Bessel beam excitation. The experiments show at the scattering threshold two types of line spectra, and above the threshold a large band spectrum. These results are interpreted by the presence of four photon processes coupling two exciting photons, one Stokes and one anti-Stokes scattered photon, developing in cascade. This interpretation can be extended to the recent studies of soliton propagation in a planar waveguide.

We show that the backward-stimulated Rayleigh-Bragg scattering (SRBS) can be efficiently generated in a three-photon absorbing medium. Compared with all other known stimulated (such as Brillouin and Raman) scattering effects, the observed effect exhibits the following three features: (i) no frequency shift, (ii) a lower pump threshold, and (iii) no critical requirement for pump spectral linewidths within a range of Δv¯≤1cm−1. The specific nonlinear scattering medium is a three-photon absorbing chromophore solution (PRL-OT04 in chloroform), pumped by 1064nm laser pulses of nanoseconds duration but with three different spectral linewidths. The mechanism for generating backward SRBS in a three-photon active medium is the formation of a stationary Bragg grating enhanced by three-photon-absorption-associated refractive index changes. A superior optical phase-conjugation property of the backward SRBS beam has been experimentally demonstrated by employing two different optical setups. In both cases, a specially introduced aberration influence of 4-5 mrad can be basically removed by the backward SRBS beam that retains a much smaller beam divergence of ≤0.4 mrad.

Stimulated Rayleigh-wing scattering is studied here in various liquids excited with a Bessel beam that allows a complete spatial separation between the transmitted exciting light and the scattered light. The results show that a large Stokes spectral band displaying substructures is obtained in the absence of self-focusing, cross-focusing, self-phase modulation, and cross-phase modulation. An interpretation is proposed based on the role of cascade Stokes–anti-Stokes coupled scattering processes.

A frequency-unshifted and backward stimulated scattering can be efficiently generated in one-photon-absorption free but two-photon absorbing materials. Using a number of novel two-photon absorbing dye solutions as the scattering media and nanosecond pulsed laser as the pump beams, a highly directional backward stimulated scattering at the exact pump wavelength can be readily observed once the pump intensity is higher than a certain threshold level. The spectral and spatial structures as well as the temporal behavior and optical phase-conjugation property of this new type of backward stimulated scattering have been experimentally studied. This stimulated scattering phenomenon can be explained by using a model of two-photon-excitation enhanced standing-wave Bragg grating initially formed by the strong forward pump beam and much weaker backward Rayleigh scattering beam; the partial reflection of the pump beam from this grating provides an positive feedback to the initial backward Rayleigh scattering beam without suffering linear attenuation influence. Comparing to other known stimulated (Raman, Brillouin, Rayleigh-wing, and Kerr) scattering effects, the stimulated Rayleigh-Bragg scattering exhibits the advantages of no frequency-shift, low pump threshold, and low spectral linewidth requirement.