Study on ultra-fast nonlinear optical functional devices

我们主要研究了以下四个主题来创建新的非线性光学功能器件。(1)半导体光放大器中的高度非简并四波混频我们在1.3 μ m多量子阱（MQW）半导体光放大器（SOA）中演示了亚皮秒光脉冲之间的高度非简并四波混频（FWM）。通过对器件进行电流脉冲抽运，可以直接测量输出频谱中的FWM信号。我们在小于1 TH_z的频率转换范围内实现了超过10%的高转换效率。(2)在SOA中使用FWM的光学采样我们已经演示了在SOA中使用FWM过程的超快速光学采样。信号光和采样光分别作为探测光和泵浦光注入SOA。我们可以测量采样波形作为FWM信号的包络线。结果表明，当输入能量为1 fJ ~ 0.1 pJ时，混流强度与输入探针能量呈良好的线性关系。(3)抑制锁模激光二极管中多重脉冲的形成我们提出了一种从主动锁模激光二极管中获得无拖尾脉冲的短光脉冲的新方法。输出的一部分以正交偏振反射回激光二极管。由于过量增益和激光二极管面处的残余反射所引起的尾脉冲被极大地抑制。我们用1.55 μ m In G_aA_sP激光二极管实验证明了过量增益导致的拖尾脉冲减少。(4)锁模激光二极管产生亚皮秒光脉冲我们利用激光二极管和快速饱和吸收器的混合锁模产生了1-2ps的短光脉冲。波长可以在1.49 ~ 1.54 μ m之间变化。利用光纤压缩将脉冲宽度缩短到800fs。

We have investigated mainly the following four topics to create new nonlinear optical functional devices.(1) Highly nondegenerate four-wave mixing in a semiconductor optical amplidierWe have demonstrated the highly nonfegenerate four-wave mixing (FWM) among subpicosecond optical pulses in a 1.3-mum multiple-quantum-well (MQW) semiconductor optical amplifier (SOA). We could directly measure the FWM signal in the output spectrum by current pulse pumping of the device. We achieved a high conversion efficiency of over 10% at a frequency conversion range of less than 1 TH_z.(2) Optical sampling using FWM in a SOAWe have demonstrated ultra-fast optical sampling using the FWM process in an SOA.A signal light and a sampling light are injected into an SOA as a probe light and a pump light, respectively. We can measure the sampling waveform as the envelope of the FWM signal. The result shows good linear relation between the FWM intensity and input probe energy for an input energy of 1 fJ to 0.1 pJ.(3) Suppression of multiple pulse formation in mode-locked laser diodesWe have proposed a new method for obtaining short optical pulses without trailing pulses from an actively mode-locked laser diode. A part of the output is reflected back into the laser diode with an orthogonal polarization. The trailing pulses caused both by the excess gain and the residual reflection at the laser diode facet are drastically suppressed. We experimentally demonstrated the reduction of the trailing pulses caused by the excess gain using 1.55mum In G_aA_sP laser diodes.(4) Sub-picosecond optical pulse generation from a mode-locked laser diodeWe have generated short optical pulses (1-2ps) by hibrid mode-locking of a laser diode with a fast saturable absorber. The wavelength could be changed in the range between 1.49mum and 1.54mum. The pulse width was shortened to 800fs using the fiber compression.