Study on ultra-fast nonlinear optical functional devices

我们主要研究了以下四个方面的内容来创造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微米多量子阱半导体光放大器(SOA)中实现了亚皮秒光脉冲之间的高度非简并四波混频。通过该装置的电流脉冲泵浦，可以直接测量输出光谱中的四波混频信号。在小于1th_z的频率转换范围内，我们获得了超过10%的高转换效率。(2)四波混频在SOA中的光学采样我们已经展示了在SOA中使用四波混频过程的超快光采样。我们可以测量采样波形作为FWM信号的包络。结果表明，当输入能量为1fJ~0.1pJ时，四波混频强度与输入探测能量呈良好的线性关系。(3)锁模激光二极管中多脉冲的抑制我们提出了一种从主动锁模激光二极管获得无拖尾脉冲的短脉冲的新方法。输出的一部分通过正交偏振反射回激光二极管。由激光二极管端面的额外增益和残余反射引起的拖尾脉冲被显著抑制。(4)锁模激光二极管产生亚皮秒光脉冲我们用快速可饱和吸收体对激光二极管进行了Hibrid锁模，获得了短光脉冲(1-2ps)。波长可在1.49微米到1.54微米的范围内变化。采用光纤压缩的方法将脉冲宽度缩短到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.