Optical phase conjugation by backscattering in barium titanate.

Area of Science:

• Nonlinear Optics
• Materials Science
• Holography

Background:

• Optical-beam phase conjugation is crucial for correcting aberrations and enabling applications like optical computing.
• Photorefractive materials offer a promising medium for nonlinear optical interactions due to their unique light-induced charge transport properties.

Purpose of the Study:

• To demonstrate optical-beam phase conjugation using two-beam coupling in photorefractive barium titanate.
• To investigate the efficiency and characteristics of the phase conjugation process.

Main Methods:

• Utilizing two-beam coupling in barium titanate crystals to amplify a counterpropagating wave.
• Employing an incident, image-bearing beam to induce exponential gain for the conjugate wave.
• Conducting experiments with laser beams at 515 nm and 488 nm with power ranging from 10 to 50 mW.

Main Results:

• Successful demonstration of optical-beam phase conjugation with a phase-conjugate wave emerging with approximately 10% of the incident beam's power.
• Observed exponential gain for counterpropagating waves fed by noise.
• Confirmed no significant frequency shift (<1 Hz) in the phase conjugation process, consistent with theoretical predictions.

Conclusions:

• Two-beam coupling in photorefractive barium titanate is an effective method for optical-beam phase conjugation.
• The process exhibits high fidelity and minimal frequency shift, making it suitable for various optical applications.
• The results align with theoretical models for phase conjugation via stimulated Brillouin backscattering.