Edwards C S, Barwood G P, Gill P, Schirmer B, Venzke H, Melling A
Centre for Length Metrology, National Physical Laboratory, Queens Road, Teddington, Middlesex TW11 0LW, UK.
Appl Opt. 1999 Jul 20;38(21):4699-704. doi: 10.1364/ao.38.004699.
The development of a laser diode absorption spectrometer that uses a strong water vapor absorption at 1393 nm is reported. Three spectroscopic techniques were compared in approximately 0.4 m of laboratory air, namely, frequency modulation, wavelength modulation, and two-tone frequency modulation spectroscopy. The first two techniques use a single-frequency modulation at 9.2 GHz and 1 kHz, respectively, generated either by a phase modulator operating at 9.2 GHz or injection current modulation at 1 kHz. The two-tone method requires modulation at two frequencies, in this case 9.19 and 9.21 GHz. It is shown that the two-tone method should provide the highest sensitivity for a trace moisture detection system.
报道了一种利用1393nm处强烈的水蒸气吸收的激光二极管吸收光谱仪的研制。在大约0.4m的实验室空气中比较了三种光谱技术，即频率调制、波长调制和双音频率调制光谱。前两种技术分别使用9.2GHz和1kHz的单频调制，分别由工作在9.2GHz的相位调制器或1kHz的注入电流调制产生。双音方法需要在两个频率上进行调制，在这种情况下为9.19和9.21GHz。结果表明，双音方法应为痕量水分检测系统提供最高的灵敏度。
