Basic research on optical distributor using orthogonally polarized four wave mixing

时间响应是光信号分配器的基本而重要的性能之一。本研究对正交极化泵浦四波混频（OPPFWM）对光信号分配器的响应进行了深入的研究：在第一年（FY2000），我们发现一些BaTiO_3晶体表现出一种反常现象，即在光栅擦除周期的前几秒，OPPFWM分配器的衍射效率增加。通过理论分析和实验表明，不同时间常数的负电荷载流子和正电荷载流子同时存在，且一次载流子的时间常数比二次载流子长。在第二年（FY2001），我们研究了两种情况：初级和次级光栅是同相的，它们完全不相。我们发现，在非相情况下，光栅的擦除速度比其他情况快得多。除此之外，我们还提出了一种新颖的方法，即在不擦除光栅的情况下，在晶体上施加外电场来切换分配器，从而破坏四波混频的相位匹配。通过这种方式，切换时间有可能缩短几个数量级。总之，我们对OPPFWM的基本特性，特别是光信号分配器的时间特性得到了一些有用的结果。

The temporal response is one of basic and important properties of optical signal distributor. The response of orthogonally polarized pump four wave mixing (OPPFWM) for optical signal distributor investigated intensively by this research :In the first year (FY2000), we discovered some BaTiO_3 crystals exhibit an anomalous phenomena that the diffraction efficiency of OPPFWM distributor increases for a first few seconds of grating erasure period. We showed, through theoretical analysis and experiment, the phenomena happens when both negative and positive charge carriers with different time constants exist and primary charge carrier has longer time constant, comparing to secondary charge carrier.In the second year (FY2001), we studied in the two cases : Primary and secondary gratings are in phase and they are totally out of phase. We showed in the out of phase case the grating erasure is much faster than the other. In addition to it, we proposed a novel way for switching the distributor by applying external electric field to the crystal and destroy the phase-matching of the four wave mixing, without erasing the gratings. By this way, it is possible that the switching time becomes shorter by several orders of magnitudes.In conclusion, we have obtained useful results on basic properties of OPPFWM, especially on its temporal behavior for optical signal distributors.