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Conference on Lasers and Electro-Optics

Experimental and theoretical double-pumped phase conjugation in inverted Nd:YAG

Darren Udaiyan, R.P.M. Green, D.H. Kim, K.S. Syed, Michael J. Damzen

Published Jan 1, 1996• 1 citation
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Abstract

Summary form only given. Double-pumped phase conjugation (DPPC) has been studied in photorefractives and in media with local response. A laser amplifier is an example of a medium with local response, by the formation of gain gratings (via spatial hole burning) from two coherent beams. In this work we demonstrate experimentally DPPC in a gain medium (Nd:YAG) and show that it can produce high powers, high reflectivities, and fast response times compared to DPPC in photorefractives.

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Double-pumped phase conjugation in inverted Nd:YAG

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An experimental study of double-pumped phase conjugation (DPPC) in a gain medium (Nd:YAG) is presented. The input–output energy and phase conjugate reflectivity of the system was experimentally characterized, with a maximum reflectivity of R∼160 observed. A self-starting DPPC laser was also produced by use of a feedback mirror, and spatial and temporal outputs are presented. The DPPC laser produced a TEM00 spatial mode output of 113 mJ in a 20-ns single-longitudinal mode pulse at a repetition rate of 10 Hz.

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A. Brignon, Jean‐Pierre Huignard

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Two-wave mixing in Nd:YAG by gain saturation

A. Brignon, Jean‐Pierre Huignard

Two-wave mixing at λ = 1.06 μm in the saturable gain of a flash-lamp-pumped Nd:YAG amplifier was investigated, both experimentally and theoretically, by development of a transient analysis. Despite the local response of the inverted medium, it is shown that energy redistribution can occur, thus leading to the depletion of a low-intensity signal beam. Finally we measured a diffraction efficiency of 20% of the transmission-gain grating by diffracting a probe beam at λ = 1.06 μm under the Bragg condition.

Optics Letters•Oct 1, 1993•42 citations
Summary form only given. Double-pumped phase conjugation (DPPC) has been studied in photorefractives and in media with local response. A laser amplifier is an example of a medium with local response, by the formation of gain gratings (via spatial hole burning) from two coherent beams. In this work we demonstrate experimentally DPPC in a gain medium (Nd:YAG) and show that it can produce high powers, high reflectivities, and fast response times compared to DPPC in photorefractives.
An experimental study of double-pumped phase conjugation (DPPC) in a gain medium (Nd:YAG) is presented. The input–output energy and phase conjugate reflectivity of the system was experimentally characterized, with a maximum reflectivity of R∼160 observed. A self-starting DPPC laser was also produced by use of a feedback mirror, and spatial and temporal outputs are presented. The DPPC laser produced a TEM00 spatial mode output of 113 mJ in a 20-ns single-longitudinal mode pulse at a repetition rate of 10 Hz.
We demonstrate for the first time, to our knowledge, second harmonic optical phase conjugation, using the second spatial harmonics of a nonsinusoidal grating formed in a photorefractive material. The possibility of harmonic phase conjugation has been considered previously for artificial Kerr media.1 We have applied the same idea to barium titanate, since the existence of the higher-order gratings in this material has been known to us for some time. In our experiment, two 1.06-µm cw Nd:YAG laser beams wrote a grating in a poled photorefractive barium titanate crystal. Then a second harmonic of the YAG at 0.532 µm read out the grating in a counterpropagating direction to one of the writing beams. In this geometry, the usual Bragg condition is not satisfied. The reflectivity of the 0.532-µm signal was rather weak, ~0.01%, with ~0.1-mW reading beam power. The buildup time was around 3 s, with loosely focused writing beams with 50-mW power in each beam. The same experiment with a SBN crystal showed no significant harmonic phase conjugation. Finally, we stress that this effect is different from the previously published result.2
Vectorial phase conjugation (VPC) is an effective way of eliminating both phase and polarisation distortions in optical systems and is of special interest in solid-state amplifiers operating at high average powers in which the amplified radiation can become depolarised. There have been experimental demonstrations of VPC in two-photon resonant media and in media with local response [1,2]. This paper presents experimental results of the phase conjugate reflectivity and fidelity of VPC in saturable media (Cr4+:YAG and inverted Nd3+:YAG).
Phase distortion correction of an optical wave propagating in laser media is a crucial problem to be taken into account in most of laser systems. For this purpose, phase conjugation through stimulated Brillouin scattering using the master oscillator-power amplification configuration has shown a very good potential to obtain high beam quality in solid-state lasers that operate at variable repetition rates. Another attractive alternative to generate the phase-conjugate wavefronts is to use a four-wave mixing (DFWM) process in the laser amplifier. In this medium, the interference between the interacting beams leads to a spatial modulation of the complex susceptibility of the medium by gain saturation (amplitude gain grating). This all-solid-state solution presents the advantage of suppressing the external nonlinear medium and would realize the required functions in the laser medium itself. Moreover, due to the amplification experienced by all the interacting beams, associated to the resonant nonlinearity of the gain saturation, high reflectivities already have been achieved in Nd:YAG amplifiers using a multipass geometry.1,2
Two-wave mixing at λ = 1.06 μm in the saturable gain of a flash-lamp-pumped Nd:YAG amplifier was investigated, both experimentally and theoretically, by development of a transient analysis. Despite the local response of the inverted medium, it is shown that energy redistribution can occur, thus leading to the depletion of a low-intensity signal beam. Finally we measured a diffraction efficiency of 20% of the transmission-gain grating by diffracting a probe beam at λ = 1.06 μm under the Bragg condition.