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

Optics and Precision Engineering

Theoretical study of the intensity dependence of two-beam coupling gain coefficient in photorefractive crystals

Jinsong Liu

Published Jan 1, 2001• 0 citations
OpenAlex

Abstract

Intensity dependence of the two-beam coupling gain coefficient Γ, the effective trap density N eff and the intensity dependent factor η(I) is studied theoretically for the two-centre photorefractive crystals. The results show that N eff, η(I) and Γ have more complicated behaviors in two-centre crystals. When S Dγ T/S Tγ D is small, N eff increases and tends to saturate with increasing intensity for both type-A and type-B two-centre crystals. When S Dγ T/S Tγ D is large, N eff increases to a maximum and then decreases a little for type-A crystals and decreases greatly for type-B crystals.The different intensity dependence of Γ in the two types of crystals comes from their different level structures.

Related papers

Theoretical study of the intensity dependence of total effective trap density in photorefractive crystals

Chi Ming-jun, Shuo‐Xing Dou, Peixian Ye

Intensity dependence of the total effective trap density N eff is studied theoretically for the two-centre and the three-charge-state photorefractive crystals. The results show that N eff always increases with increasing intensity in three-charge-state crystals, whereas it has more complicated behaviors in two-centre crystals. When S D γ T / S T γ D is small, N eff increases and tends to saturate with increasing intensity for both type-A and type-B two-centre crystals. When S D γ T / S T γ D is large, N eff increases to a maximum and then decreases a little for type-A crystals and decreases greatly for type-B crystals. The different intensity dependences of N eff in the two types of crystals come from their different level structures.

Acta Physica Sinica (Overseas Edition)•Sep 1, 1999•0 citations

Signal-to-pump ratio dependence of buildup and decay rates in photorefractive nonlinear two-beam coupling

Moshe Horowitz, Ron Daisy, Baruch Fischer

The buildup and the decay of photorefractive two-beam coupling are experimentally demonstrated to be strongly dependent on the intensity ratio of the two beams (signal-to-pump ratio). The experiment, done with a BaTiO3 crystal, shows good agreement with the theory of two-beam coupling in the depleted-pump regime. The deviation of the response behavior from the small-signal regime is seen for ratios as small as ∼10−5. These results are significant for applications of two-beam coupling as gain media, especially for the elimination of amplified noise (fanning).

Journal of the Optical Society of America B•Sep 1, 1992•18 citations

Intensity dependence of stationary energy transfer in codirectional photorefractive cross-polarization two-wave mixing

Jinsong Liu, Changhong Liang

The intensity dependence of stationary energy transfer in photorefractive codirectional cross-polarization two-wave mixing is examined. The intensity formulae remained effect both in the saturation and the intermediate regime (before saturation) are driven, and the analytical expressions with the ratio of saturation intensity to total incident intensity as their explicit variable are obtained for the case of pump depletion. It is necessary to use these formulae in some problems, such as the temperature or intensity dependence of cross-polarization two-wave mixing. A method of measuring the coupling coefficient and saturation intensity of a cubic photorefractive crystal is presented, which is suitable for cross-polarization two-wave mixing in the intermediate regime.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•Sep 30, 1996•0 citations

Intensity-Dependent asymmetric transmission through a photorefractive etalon

Stephen Ducharme, Bao Vu

We describe observations of asymmetric transmission through a Fabry-Perot etalon which contains a photorefractive crystal of barium titanate. The etalon transmission is asymmetric due to two-beam energy coupling in the photorefractive crystal as predicted by He et al. [Q. B. He, P. Yeh and C. Gu, Opt. Lett, 17, 664 (1992)]. We have observed up to 25% asymmetry in the contrast, the ratio between the maximum and minimum transmittance, when the barium titanate crystal is reversed within the etalon. The etalon transmission is also intensity-dependent due to the intensity dependence of photorefractive two-beam energy coupling.

Ferroelectrics•Dec 1, 1995•1 citation

Comparison of three wave mixing in photorefractive and nematic liquid crystals

David John Webb, LASZLO SOLYMAR

Consideration of the coupled wave equations governing three wave mixing in photorefractives and nematic liquid crystals, when both are exhibiting a local response, shows that the main difference between the two is the self phase modulation that occurs in the liquid crystals. It is this difference that explains the dissimilar variation of the exponential gain factor, as a function of inter-beam angle. The other difference between the two media is the dependence of gain on the total incident intensity for the case of nematic liquid crystals and on the detuning frequency for the case of photorefractive media. >

•Sep 16, 1991•0 citations

Optical Amplification and Slow Light Based on Two-Wave Mixing at Large Modulation Depth

Zhang Yun-Dong, Jianbo Ye, Qiu Wei

Based on Kukhtarev's equations, we derive the formulae of intensity-coupling coefficient, the phase-coupling coefficient and the group velocity at large modulation depth. It is theoretically shown that the signal beam can be amplified after passing through the photorefractive crystal and the group velocity reduced to m/s, even cm/s. Meanwhile, we also analyse the influence of the thermal excitation rate and the large signal effects on optical amplification and reduction of light propagation in photorefractive two-wave mixing.

Chinese Physics Letters•May 1, 2007•0 citations
Intensity dependence of the two-beam coupling gain coefficient Γ, the effective trap density N eff and the intensity dependent factor η(I) is studied theoretically for the two-centre photorefractive crystals. The results show that N eff, η(I) and Γ have more complicated behaviors in two-centre crystals. When S Dγ T/S Tγ D is small, N eff increases and tends to saturate with increasing intensity for both type-A and type-B two-centre crystals. When S Dγ T/S Tγ D is large, N eff increases to a maximum and then decreases a little for type-A crystals and decreases greatly for type-B crystals.The different intensity dependence of Γ in the two types of crystals comes from their different level structures.
Intensity dependence of the total effective trap density N eff is studied theoretically for the two-centre and the three-charge-state photorefractive crystals. The results show that N eff always increases with increasing intensity in three-charge-state crystals, whereas it has more complicated behaviors in two-centre crystals. When S D γ T / S T γ D is small, N eff increases and tends to saturate with increasing intensity for both type-A and type-B two-centre crystals. When S D γ T / S T γ D is large, N eff increases to a maximum and then decreases a little for type-A crystals and decreases greatly for type-B crystals. The different intensity dependences of N eff in the two types of crystals come from their different level structures.
The buildup and the decay of photorefractive two-beam coupling are experimentally demonstrated to be strongly dependent on the intensity ratio of the two beams (signal-to-pump ratio). The experiment, done with a BaTiO3 crystal, shows good agreement with the theory of two-beam coupling in the depleted-pump regime. The deviation of the response behavior from the small-signal regime is seen for ratios as small as ∼10−5. These results are significant for applications of two-beam coupling as gain media, especially for the elimination of amplified noise (fanning).
The intensity dependence of stationary energy transfer in photorefractive codirectional cross-polarization two-wave mixing is examined. The intensity formulae remained effect both in the saturation and the intermediate regime (before saturation) are driven, and the analytical expressions with the ratio of saturation intensity to total incident intensity as their explicit variable are obtained for the case of pump depletion. It is necessary to use these formulae in some problems, such as the temperature or intensity dependence of cross-polarization two-wave mixing. A method of measuring the coupling coefficient and saturation intensity of a cubic photorefractive crystal is presented, which is suitable for cross-polarization two-wave mixing in the intermediate regime.
We describe observations of asymmetric transmission through a Fabry-Perot etalon which contains a photorefractive crystal of barium titanate. The etalon transmission is asymmetric due to two-beam energy coupling in the photorefractive crystal as predicted by He et al. [Q. B. He, P. Yeh and C. Gu, Opt. Lett, 17, 664 (1992)]. We have observed up to 25% asymmetry in the contrast, the ratio between the maximum and minimum transmittance, when the barium titanate crystal is reversed within the etalon. The etalon transmission is also intensity-dependent due to the intensity dependence of photorefractive two-beam energy coupling.
Consideration of the coupled wave equations governing three wave mixing in photorefractives and nematic liquid crystals, when both are exhibiting a local response, shows that the main difference between the two is the self phase modulation that occurs in the liquid crystals. It is this difference that explains the dissimilar variation of the exponential gain factor, as a function of inter-beam angle. The other difference between the two media is the dependence of gain on the total incident intensity for the case of nematic liquid crystals and on the detuning frequency for the case of photorefractive media. >
Based on Kukhtarev's equations, we derive the formulae of intensity-coupling coefficient, the phase-coupling coefficient and the group velocity at large modulation depth. It is theoretically shown that the signal beam can be amplified after passing through the photorefractive crystal and the group velocity reduced to m/s, even cm/s. Meanwhile, we also analyse the influence of the thermal excitation rate and the large signal effects on optical amplification and reduction of light propagation in photorefractive two-wave mixing.