Basic research on optical distributor using orthogonally polarized four wave mixing

时间响应特性是光信号分配器的基本和重要特性之一。本研究着重研究了光信号分配器的正交偏振泵浦四波混频（OPPFWM）响应：在第一年（2000财年），我们发现BaTiO_3晶体在光栅擦除周期的最初几秒内，OPPFWM分配器的衍射效率增加。通过理论分析和实验研究，我们发现了当正负电荷载流子同时存在且时间常数不同，且主电荷载流子的时间常数比次电荷载流子的时间常数大时，会出现这种现象，在第二年（2001财年）我们研究了主、次光栅同相和完全异相两种情况。我们表明，在异相的情况下，光栅擦除比其他快得多。此外，我们还提出了一种新的开关分配器的方法，即在晶体上施加外电场，破坏四波混频的相位匹配，而不擦除光栅。通过这种方法，可以使开关时间缩短几个数量级。总之，我们得到了关于OPPFWM基本性质的有用结果，特别是对于光信号分配器的时间特性。

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.