Optimization Design of Nonlinear Optical Frequency Conversion Devices Using Simulated Annealing Algorithm

Abstract

Laser has become to be a fundamental light source in modern communication, scientific research, and industrial applications. More and more laser frequencies are required for various applications. However, common laser crystals can provide only some fixed frequencies which cannot satisfy various requirement. Nonlinear optical process presents an alternative approach for generating rich laser frequencies. The traditional nonlinear optical processes usually require the so called phase-matching condition [1, 2], which requires the nonlinear optical crystals with birefringence. The phase-matching condition raises a restriction of the choice of natural birefringence materials in the applications of frequency conversion. Quasi-phase-matching method uses periodic modulation of the nonlinear property of a crystal to compensate the mismatch between the wave vectors of the interaction light beams [3]. This method allows utilization of the large component of the nonlinear susceptibility tensor, which is usually inaccessible with the common phase matching. Periodic optical superlattice provides a reciprocal vector to compensate the phase mismatch between the interacting light beams. Thus, only one nonlinear process can be performed in the periodic optical superlattice. This idea can be naturedly expended to the aperiodic optical supperlattice which can provide a series of reciprocal vectors. The reciprocal vectors can be preset for special nonlinear process. The key problem is how to design different aperiodic optical supperlattice for matching the specified nonlinear optical process with high conversion efficiency.