The Study On The Coupling Effect In Optical Superlattices

In the past decades, with the development of the quasi-phase matching technology, the solid state lasers, which are made up of optical superlattice, has been made great progress. The advantage of the solid state laser is that it can be made compact, high power and good stability. The LiNbO3 and LiTaO3, with which the optical frequency conversion is easy realized, are widely used by more and more researchers to construct varies of solid state laser. Optical superlattice has been extensively studied for efficient frequency conversion efficiency. The excellent performances such as high amplification, low threshold, and easiness to realize phase matching make optical superlattice especially useful for solid state lasers. As excellent optical materials, LiNbO3 and LiTaO3 also have outstanding electro-optic effect and acousto-optic effect, which can be used to control and modulate the propagation of light in the optical superlattice. In this thesis, we studied experimentally the influence of electro-optic effect on the generation of second harmonic in periodic and quasiperiodic optical superlattice, the electro-optic modulation on coupled quasi-phase matched frequency conversion process. We studied theoretically the modulation of acousto-optic effect on the generation of second harmonic in periodic optical superlattice. The main results are as follows:1. We designed the periodic LN and quasi-periodic LT optical superlattice and realized the modulation of the output of second harmonic generation of 1064nm light. The amplitude and polarization of 532nm were tuned by using the external DC electric field along the Y axis of the sample. 2. We designed the periodic LT optical superlattice for third harmonic generation. With Nd:YVO4 as the laser crystal and an 808nm diode laser as the pump source, the coupled quasi-phase matched frequency conversion was realized. The modulation of the third harmonic in the coupled quasi-phase matched frequency conversion of 1342nm could be modulated by applying an external electric field along the Z axis of the sample.3. We studied theoretically the effect of acousto-optic modulation on quasi-phase matched frequency conversion. An acoustic wave is introduced to modulate the second harmonic generation in an optical superlattice. The wave-coupling equations governing acousto-optic (AO) polarization coupling and frequency doubling in periodically poled lithium niobate are proposed and analyzed. The numerical simulation results show that there is a competition between the AO polarization modulation and second harmonic generation (SHG). The output of second harmonic can be switched or manipulated by the longitudinal acoustic-wave.