研究了激光器扫描步长和线宽两种特性对可调谐半导体激光吸收光谱检测系统的影响,理论上推导出激光与气体吸收谱线的作用原理,分析出扫描信号(锯齿波)的台阶间隔和高度影响激光器中心波长的扫描原理.设定了仿真参数,仿真出锯齿波台阶数与最大扫描误差关系曲线,得出扫描信号的一个周期内具有4000个台阶时,半高全宽(FWHM)大于0.01 cm-1,误差小于1‰；仿真出激光器线宽与最大幅值、线宽误差关系曲线,给出线宽误差最大为1%,0.5%时激光器线宽对应的最小FWHM.在温度系数n取0.9,大气展宽系数γair取0.005的条件下,给出温度T ,压强P与FWHM关系图,推出了适用的压强与温度范围.为指导选取激光器与气体吸收谱线、提高系统检测限提供了相关理论依据.%In this paper, we study the effects of laser scanning step length and width characteristic on tunable diode laser absorption spectrum detection system, theoretically derive the principle of interaction between laser and gas absorption line, and analyse the principle of effects of step duration and height about scanning signal (ramp) on the laser central wavelength. After setting the simulation parameters, the curve between the number of ramp steps and the maximum scanning error is obtained. If the scanning signal has 4000 steps in one cycle, the error is less than 1‰ with full width at half maximum (FWHM) value being greater than 0.01 cm-1. The curves between laser linewidth and maximum amplitude or linewidth error are simulated, and also the relationship between laser linewidth and minimum FWHM is given with linewidth error maximum values being 1%and 0.5%. On condition that temperature coefficient n is 0.9 and air-broadened coefficient is 0.005, this paper gives the relationship among pressure, temperature and FWHM, from which the suitable pressure P and temperature T range are deduced. It can provide the relevant theoretical basis for selecting the laser and gas absorption lines and also for improving the system detection limit.
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