Photorefractive Double Phase-conjugate Mirror Research Articles

Recovery of Laser-Diode Coherence Length by a Photorefractive Double Phase-Conjugate Mirror

We report an experimental study of dynamic coupling of two laser diodes (LD’s) with a double phase-conjugate mirror (DPCM) in a Bi12TiO20 fiber-like crystal. After the DPCM is recorded in the crystal, one of the LD’s is switched to the multimode regime, while the other remains lasing in the single longitudinal mode. Nevertheless, the DPCM produces phase locking of the single-mode laser with one of the longitudinal modes of the multimode laser. Only the longitudinal mode survives after the transmission through the DPCM, demonstrating the coherence length recovery of the multimode laser.

Laser-diode injection locking with a double phase-conjugate mirror in photorefractive Bi_12TiO_20 fiberlike crystal under external alternating voltage

Injection locking of two laser diodes operating at 681–684 nm with a double phase-conjugate mirror recorded in photorefractive Bi12TiO20 crystal under an external alternating electric field is studied. It was found that there are three different regimes of laser-diode coupling distinguished by the various coherences of the light emitted by the coupled laser diodes. The ability of the photorefractive double phase-conjugate mirror to recover the coherence length is experimentally demonstrated. Advantages of photorefractive Bi12TiO20 fiberlike samples over bulk BaTiO3 crystals to record the double phase-conjugate mirror are listed.

Double phase-conjugate mirror: to oscillate, or not to oscillate?

A physical picture of the differences in operation of the photorefractive double phase-conjugate mirror for TM versus TE polarization is presented.

Order-disorder phase transition and critical slowing down in photorefractive self-oscillators.

We study self-oscillation in a photorefractive double phase-conjugate mirror and show that it undergoes an order-disorder phase transition at a critical gain-threshold point. We present theoretical and experimental results on two key properties of this phase transition: critical slowing down and the characteristic order parameter. We show that the correlation distance of the refractive index variation responsible for the double phase conjugation changes abruptly from very small values (disorder, below threshold) to a large unique value (order, above threshold) determined primarily by the boundary conditions. Finally, we point out similarities and important differences between this combined light and matter phase transition and the mean field and Ginzburg-Landau theories.

Conjugation fidelity and reflectivity in photorefractive double phase-conjugate mirrors

We present an experimental study of the behavior of photorefractive double phase-conjugate mirrors that illustrates recent theoretical predictions. We observe a sharp fidelity threshold that significantly depends on the specific feature size in the input beams. Furthermore, we find that if the two input beams have unequal intensities the conjugation process is asymmetric and the steady-state fidelity is better on the side of the crystal on which the more-intense beam enters.

Operation of the double phase conjugate mirror for TE polarization: exact solution and failure of the slowly varying envelope approximation

The steady-state two-dimensional coupled wave equations describing the photorefractive double phase conjugate mirror with TE-polarized pumps, and which are derived directly from Maxwell's equations without employing the slowly varying envelope approximation (SVEA), are solved analytically in the undepleted pumps approximation for equal pump intensities and angles of incidence. The solutions are compared with those obtained using the SVEA, and the predictions of each approach with regard to the operation of the double phase conjugate mirror are discussed.

Experimental investigation of a system of two coupled double phase conjugate mirrors

The results of an investigation of a nonlinear resonator formed by two coupled photorefractive double phase conjugate mirrors are presented. In steady-state the resonator exhibits bistable behavior versus both pumping beam power ratio and the Fresnel number of the cavity. The dynamics of the development of the scattering is characterized by the relatively long “silence” zone preceding the appearance of conjugate beams.

Wide-field-of-view heterodyne receiver using a photorefractive double phase-conjugate mirror

The use of a double phase-conjugate mirror to increase the angular field of view of an optical heterodyne receiver is investigated. Fields of view and overall efficiencies far larger than those predicted by the antenna theorem for conventional heterodyne systems are obtained.