Circuit Design Of Gas Sensor Based On Quantum Cascade Laser

Quantum cascade laser’s (QCL) wide tuning range, high output power and single-mode operating characteristics make it very suitable for high resolution spectroscopy. Combined with the strong absorption in the fundamental frequency of infrared gas molecules, gas detection based on QCL, which has the characteristic of high sensitivity, selectivity and fast response, have gradually become the best way to trace gas detection.However QCL, is very expensive and is easily damaged by over current and overheating. these features increase the difficulty of driver design and integration system design, also make it not convenient for Held application. Based on the above, a precise nanosecond pulse laser drive system and a photo electric detector system were designed. This paper listed the hardware schematic and the method of selecting device. and analyzing the key parameter in detail.1he hardware system of the driver includes low-noise power, wave generator, pulsed constant current source, over-current protection, over average power protection and thermal control module. The hardware system of the detector includesⅠ-Ⅴ converter, low pass11Her, programmable gain amplifier, and synchronous detection module. This system is a high integration design, cooperate with the structural design, it is greatly convenient for filed application and portable application.This system can be simulated by global and independent module. From the result of simulation, the pulse amplitude can reach to1.1A, and can be modulated from0.6A to1.1A between a frequency of1KHz and10KHz; the pulse’s rise and fall time is less than3.5ns with10ns pulse width; the response time of protection module is less than8ns. The detector system can complete signal acquisition with a high signal-to-noise ratio.