Wide & Fast Wavelength Tuning Of Dfb Diode Laser And Applications For Gas Detection

Based on the tuning mechanism of DFB LD, the mathematical model of LD tuning characteristic was established in the paper. The transfer function of LD tuning characteristic is given to express the relation between radiation wavelength and current and temperature. A fast thermal tuning method of LD was proposed, which we changed the LD temperature fast and continuously by exerting a larger cyclic drive current to the thermoelectric cooler (TEC) in LD component. With TEC drive current of 1.5A, 4nm wavelength range can be achieved in less than 2.2s. Temperature tunning range can be broadened by improving the conditions of laser cooling to obtain a wider wavelength scanning range.It's very simple and effective. The prediction method of dynamic wavelength was proposed, that is, by measuring the temperature of NTC thermistor to predict the LD chip temperature, according to the injection current value and priori tuning characteristics of LD output wavelength can be estimated in real time. The experimental results showed that the deviation of absorption lines wavelength were less than 10pm, which proved the method described in this paper effective and feasible. An equivalent circuit model of LD module (LDM) was built and the performance of LDM has been simulated by PSPICE at different ambient temperatures,which proved the applicability of the wavelength prediction method.The second harmonic signal of wavelength modulation spectroscopy (WMS-2f) of CO₂ has been recorded between 6320 cm^-1 and 6336 cm^-1 by employing the wide range TDLAS system. 8 strong absorption lines and 14 weak lines were obtained in the region. The WMS-2f absorption spectra of CO₂ and CO gas mixture have been measured and analyzed as well. Therefore, wide range TDLAS technology can be used for high-precision measurement or simultaneous multiple gases detection.The innovations of this paper are that a fast tuning method of broad spectrum was proposed and the dynamic wavelength of the laser was identified precisely during the temperature tuning,which can be used for tunable diode laser absorption spectroscopy (TDLAS) technology and optical communication.