Ultrafast spectroscopy by using laser diode

研究项目的目的分为两个项目。一个是找到一种简单的方法，利用商业上可获得的常规二极管激光器获得超短激光脉冲。二是利用半导体光学器件发展新的超快光谱技术。研究结果总结如下：1.我们可以在半导体激光器的输出端面上涂上良好的减反射膜。1.利用激光二极管的减反射膜实现了外腔锁模振荡。脉冲宽度、脉冲能量和重复频率分别为10 ps、10 pj和100 MHz。1.上述皮秒二极管激光器的输出（脉冲宽度30 ps，脉冲能量10 pJ）通过使用由Q开关YAG激光器的第二谐波光激发的染料单元放大器来放大。获得了约10^6的放大倍数，脉冲宽度、脉冲能量和重复频率分别为40 ps、40 uJ和1 Hz。1.我们发现多模半导体激光器和超辐射发光二极管可以用作非相干光光子回波实验的激发光源。1.利用非激光光源，即普通型发光二极管，我们首次成功地观测到了累积光子回波。非激光光源的使用将把光子回波实验扩展到目前激光无法利用的波长范围。

The purpose of the research project is divided into two items. One is to find a simple method to get ultrashort laser pulses by using commercially available conventional diode lasers. And the other is to develop a new technique of ultrafast spectroscopy by using semiconductor optical devices. Summary of the results are as follows: 1. We could apply good anti-reflection coatings to the output facets of laser diodes. 1. Mode-locking oscillation was obtained in an external cavity by using the anti-reflection coated laser diode. The pulse width, pulse energy and the repetition rate were 10 ps, 10 pj and 100 MHz, respectively. 1. The output of the above mentioned picosecond diode laser (pulse width 30 ps, pulse energy 10 pJ) was amplified by using a dye cell amplifier excited by the second harmonic light of a Q-switched YAG laser. The amplification of about 10^6 was obtained, and the pulse width, pulse energy and repetition rate of the output were 40 ps, 40 uJ and 1 Hz, respectively. 1. We showed that multi-mode diode lasers and superluminescent diodes can be used as the excitation light source for incoherent light photon echo experiments. 1. We succeeded in observing accumulated photon echoes for the first time by using a non-laser light source, a normal type light emitting diode. The use of non-laser light source will extend the photon echo experiment into the wavelengthregions where lasers are not presently available.