Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC)

High efficiency Raman amplification of waves with conformed profiles

Ildar A. Begishev, I. A. Kulagin, T. Usmanov

Published Jan 1, 1994• 0 citations
Publisher

Abstract

In the case of the scattering Raman amplification of light beams in a field of powerful ultrashort pulses, the back influence of the amplified radiation on the fundamental wave may be significant. Moreover, properties of the media, such as a population of atomic states, may significantly change. That leads to amplitude-phase modulation of the fundamental pulse owing to change of direction of intensity exchange in the pulse.1 As a result, the bond between the fundamental and Stokes waves becomes weaker, that results in a decrease in the frequency conversion efficiency. For spatial inhomogeneous beams this effect is different in various beam sections.

DOI
10.1364/cleo_europe.1994.cwf85

Related papers

Change in the shape of frequency-modulated light pulses during amplification

E G Lariontsev, V. N. Serkin

An analysis is made of the propagation of a frequency-modulated light pulse in a linearly amplifying medium with an inhomogeneously broadened gain profile. It is shown that a pulse can be compressed considerably during amplification. Conditions are established under which strong distortions of the pulse shape may result in its splitting. An analysis is made of the influence of the phase self-modulation of radiation on the shape of ultrashort light pulses in oscillators and amplifiers.

Soviet Journal of Quantum Electronics•Jun 30, 1976•1 citation

Transient stimulated Raman amplification with picosecond pulse trains

Jui‐Teng Lin, John F. Reintjes

We consider transient stimulated Raman amplification of trains of picosecond pulses. In this regime the gain of a single pulse is reduced from its steady-state value because of the inability of the nonlinear polarization to follow the time variations of the pump pulse. In addition oscillatory behavior of the pump and Stokes pulse amplitudes have been predicted in the transient regime in conditions of high pump depletion. When the pump radiation is in the form of a train of pulses whose separation is comparable to or shorter than the dephasing time of the nonlinear medium, increased gain can be experienced by later pulses in the train because they can grow from the material polarization created by earlier pulses. We have analyzed this type of amplification as a function of pulse spacing, pump energy, and pump intensity in the regime of high pump depletion. In addition we have considered the effects of Stark shifts of the two-photon resonant Raman level on the Stokes conversion efficiency. We find that at constant pulse intensity the conversion efficiency increases with time through the pulse train, gradually approaching steady state at low conversion efficiencies at times long compared to T2. The maximum conversion efficiency increases as the pulse spacing is decreased. If the pump depletion is too high the peak conversion of the Stokes oscillates through the train in a manner similar to the oscillations of the intensity of a single pulse. A Stark shift of the resonant level can cause reduced gain as well as introduce phase shifts on the Stokes and pump beams. The effects of these processes on the conversion efficiency are discussed.

Annual Meeting Optical Society of America•Jan 1, 1985•0 citations

Switching of Raman scattering

Rob Heeman, Herman P. Godfried

In transient stimulated Raman scattering (SRS), efficient conversion of short pump pulses to Stokes radiation is difficult to obtain. A short seed pulse at the Stokes frequency increases the efficiency and may induce full depletion of the pump pulse, even when the pump power is too low to scatter efficiency without seed. However, for low pump powers the Ra­man polarizability induced by the pump and seed pulse decays, which results in a terminating Stokes pulse, even when the pump pulse itself is long. Nevertheless, the Stokes pulse can be wider than the dephasing time of the Raman polarizability or the width of the seed pulse by an order of magnitude. Applying a second seed may once again induce a sufficiently large Raman polarizability but only if the phase of the Stokes seed matches the phase difference between the pump and remaining Raman polarizability. If not, the polarizability induced by the first pulse and consequently the conversion efficiency for the Stokes radiation decreases. Therefore, it is possible to switch off the Stokes pulse by applying a second seed with appropriate phase and intensity.

Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC)•Jan 1, 1994•0 citations

Raman solitons and self-phase modulation

R. Wolfson, Kai J. Drühl

Homogeneous broadening leads to the decay of Raman solitons,1,2 if pump and Stokes are not exactly on Raman resonance. This is due to a dispersive frequency shift at the soliton center. Media with strong self-phase modulation (SPM) can balance this dispersive effect and even show an amplification of peak pump intensity. In this case, the net decrease in pump power is compensated by narrowing from SPM. We present analytical and numerical results, which demonstrate this effect for media with strong Stark shift.

Annual Meeting Optical Society of America•Jan 1, 1988•0 citations

Wave-mixing and Phase Conjugation in Laser Active Media

Kazuo Kuroda

Nonlinear optics normally involves the change in the susceptibility of a material due to the presence of optical radiation. In many cases, the light-matter interaction produces a change in the refractive index of the medium, as occurs in photorefractive media, as well as in Kerr-like media, Brillouin-active media and absorbing media with thermallyinduced refractive index changes. Such nonlinear refractive index variation corresponds to a change in the real part of the optical susceptibility %. In resonant materials, the optical radiation induces stimulated emission (or absorption) causing transfer of population between different energy states of the medium. This can lead to saturation of the amplification (or absorption) corresponding to changes in the imaginary part of the susceptibility x= i2odk where the amplitude gain coefficient a(I) is a saturable function of the intensity /, and k is the magnitude of the wavevector of the optical radiation. The interference of two (or more) coherent beams I(x) in the laser amplifier can cause a modulation of the population inversion N(x). This modulation of the inversion is commonly known as spatial hole burning in lasers and leads to formation of a gain-grating a(x) = 1/2GN(X) where G is the stimulated emission cross-section. The gain grating can act as a very efficient diffractive optical element exhibiting high diffraction efficiency that may be even greater than unity [16] and also very high phase conjugate reflectivity using four-wave mixing (FWM) geometries [5-7].

CRC Press eBooks•Mar 14, 2002•0 citations

A novel technique for suppression of parasitic superfluorescence in backward Raman amplifiers

John A. Caird

The major parasitic modes of backward Raman amplifiers are different forms of superfluorescent forward Raman scattering. It is shown that spatial, and/or temporal variation of the Raman frequency in the scattering medium can inhibit amplification of spontaneously scattered light by creating off-resonant conditions in the forward direction. If the frequencies of the optical pulses are properly varied in time (the pulses are chirped), the required resonance condition for amplification of a counterpropagating Stokes wave can be maintained throughout the medium. Raman transition frequencies can be varied in an atomic vapor by application of a magnetic field via the Zeeman effect. The use of thallium (T1) metal vapors for scattering XeCl or KrF excimer laser radiation is considered as a particular example.

IEEE Journal of Quantum Electronics•Apr 1, 1980•9 citations
In the case of the scattering Raman amplification of light beams in a field of powerful ultrashort pulses, the back influence of the amplified radiation on the fundamental wave may be significant. Moreover, properties of the media, such as a population of atomic states, may significantly change. That leads to amplitude-phase modulation of the fundamental pulse owing to change of direction of intensity exchange in the pulse.1 As a result, the bond between the fundamental and Stokes waves becomes weaker, that results in a decrease in the frequency conversion efficiency. For spatial inhomogeneous beams this effect is different in various beam sections.
We consider transient stimulated Raman amplification of trains of picosecond pulses. In this regime the gain of a single pulse is reduced from its steady-state value because of the inability of the nonlinear polarization to follow the time variations of the pump pulse. In addition oscillatory behavior of the pump and Stokes pulse amplitudes have been predicted in the transient regime in conditions of high pump depletion. When the pump radiation is in the form of a train of pulses whose separation is comparable to or shorter than the dephasing time of the nonlinear medium, increased gain can be experienced by later pulses in the train because they can grow from the material polarization created by earlier pulses. We have analyzed this type of amplification as a function of pulse spacing, pump energy, and pump intensity in the regime of high pump depletion. In addition we have considered the effects of Stark shifts of the two-photon resonant Raman level on the Stokes conversion efficiency. We find that at constant pulse intensity the conversion efficiency increases with time through the pulse train, gradually approaching steady state at low conversion efficiencies at times long compared to T2. The maximum conversion efficiency increases as the pulse spacing is decreased. If the pump depletion is too high the peak conversion of the Stokes oscillates through the train in a manner similar to the oscillations of the intensity of a single pulse. A Stark shift of the resonant level can cause reduced gain as well as introduce phase shifts on the Stokes and pump beams. The effects of these processes on the conversion efficiency are discussed.
In transient stimulated Raman scattering (SRS), efficient conversion of short pump pulses to Stokes radiation is difficult to obtain. A short seed pulse at the Stokes frequency increases the efficiency and may induce full depletion of the pump pulse, even when the pump power is too low to scatter efficiency without seed. However, for low pump powers the Ra­man polarizability induced by the pump and seed pulse decays, which results in a terminating Stokes pulse, even when the pump pulse itself is long. Nevertheless, the Stokes pulse can be wider than the dephasing time of the Raman polarizability or the width of the seed pulse by an order of magnitude. Applying a second seed may once again induce a sufficiently large Raman polarizability but only if the phase of the Stokes seed matches the phase difference between the pump and remaining Raman polarizability. If not, the polarizability induced by the first pulse and consequently the conversion efficiency for the Stokes radiation decreases. Therefore, it is possible to switch off the Stokes pulse by applying a second seed with appropriate phase and intensity.
Homogeneous broadening leads to the decay of Raman solitons,1,2 if pump and Stokes are not exactly on Raman resonance. This is due to a dispersive frequency shift at the soliton center. Media with strong self-phase modulation (SPM) can balance this dispersive effect and even show an amplification of peak pump intensity. In this case, the net decrease in pump power is compensated by narrowing from SPM. We present analytical and numerical results, which demonstrate this effect for media with strong Stark shift.
Nonlinear optics normally involves the change in the susceptibility of a material due to the presence of optical radiation. In many cases, the light-matter interaction produces a change in the refractive index of the medium, as occurs in photorefractive media, as well as in Kerr-like media, Brillouin-active media and absorbing media with thermallyinduced refractive index changes. Such nonlinear refractive index variation corresponds to a change in the real part of the optical susceptibility %. In resonant materials, the optical radiation induces stimulated emission (or absorption) causing transfer of population between different energy states of the medium. This can lead to saturation of the amplification (or absorption) corresponding to changes in the imaginary part of the susceptibility x= i2odk where the amplitude gain coefficient a(I) is a saturable function of the intensity /, and k is the magnitude of the wavevector of the optical radiation. The interference of two (or more) coherent beams I(x) in the laser amplifier can cause a modulation of the population inversion N(x). This modulation of the inversion is commonly known as spatial hole burning in lasers and leads to formation of a gain-grating a(x) = 1/2GN(X) where G is the stimulated emission cross-section. The gain grating can act as a very efficient diffractive optical element exhibiting high diffraction efficiency that may be even greater than unity [16] and also very high phase conjugate reflectivity using four-wave mixing (FWM) geometries [5-7].
The major parasitic modes of backward Raman amplifiers are different forms of superfluorescent forward Raman scattering. It is shown that spatial, and/or temporal variation of the Raman frequency in the scattering medium can inhibit amplification of spontaneously scattered light by creating off-resonant conditions in the forward direction. If the frequencies of the optical pulses are properly varied in time (the pulses are chirped), the required resonance condition for amplification of a counterpropagating Stokes wave can be maintained throughout the medium. Raman transition frequencies can be varied in an atomic vapor by application of a magnetic field via the Zeeman effect. The use of thallium (T1) metal vapors for scattering XeCl or KrF excimer laser radiation is considered as a particular example.