基于频率补偿的窄脉冲量子级联激光器快速驱动技术

脉冲量子级联激光器(QCL)因自热效应会导致谱线展宽,故需极短的电流脉冲驱动。理论极限线宽所需的脉宽为5~15 ns,但由于环路寄生参数的影响,窄脉冲会引起信号过冲或振荡,因此目前商用的QCL驱动器无法满足这个要求。为获得更理想的激光器线宽,在常规脉冲恒流电路的基础上,采用频率补偿的方法来消除过冲和振荡,并设计了一款稳定的纳秒级激光器驱动电路。实验结果显示该驱动装置实现了峰值电流0~2 A、脉宽8.4~200 ns、上升时间4 ns、过冲1%的脉冲电流输出。使用中国科学院半导体研究所研制的波长4.6m激光器和傅里叶变换光谱仪进行测试,当驱动脉宽由100 ns减小到10 ns时,激光器线宽由0.35 cm-1线性递减到0.12 cm-1。综合验证表明,所设计的驱动装置实现了稳定的窄脉冲电流输出,尤其适用于量子级联激光器的窄线宽驱动及应用。

A fast driving technique for narrow pulsed quantum cascade lasers with frequency compensation

The line width of pulsed quantum cascade lasers(QCL) increases with the device heating up during the driving pulse, so QCL drivers need to generate ultra-short current pulse. Generally, pulses of 5 ns to 15 ns durations can reach the Fourier transform limit. However, due to the existence of parasitic parameters, narrow pulses will lead to overshoot or oscillation. Therefore, the current commercial QCL drivers can not meet this requirement. To obtain narrower line width of QCLs, a frequency compensation method based on conventional pulse constant current circuit was proposed in this work to eliminate overshoot and oscillation. And a stable pulse laser driving circuit was also designed which can output 0-2 A pulse current, with 8.4-200 ns pulse width, 4 ns rising time, and 1% overshoot. Function test was carried out with a QCL with 4.6m center wavelength made from Institute of Semiconductor of Chinese Academy of Sciences, and a Fourier transform infrared spectroscopy. The laser line width decreased almost linearly from 0.35 cm-1 to 0.12 cm-1, when the driving pulse width decreased from 100 ns to 10 ns. Experimental results show that the driver is able to output stable narrow pulses, which is suitable for narrow line width driving of QCLs and their applications.