The Design And Study Of Driver For Quantum Cascade Laser

Quantum Cascade Laser becomes the ideal light source in the infrared trace gas detection system because of its advantages such as single mode output and high output power. The paper developed a good driver for the quantum cascade laser to improve the performance of the laser and gas detection system. Our work is supported by National Technology and Support Project: The development of infrared CO detector(sensor) used for coal mine.Firstly, the principle, the advantages, the development and applications of quantum cascade lasers are introduced. Then, the domestic and foreign research status of quantum cascade laser drivers is explained. In accordance with the detailed requirements of the laser, we propose the overall design scheme.Secondly, the hardware design is described. It includes microprocessor module, regulating and slow starting module, current control module, over-current protection module, current detection and control module, temperature control module, display and serial communication module. A DC signal, a ramp signal and a sinusoid signal with adjustable amplitude and frequency are generated by current control module to form the superimposed drive current signal to modulate the laser output wavelength. The over-current protection module limits the maximum working current of the laser, which guarantees the laser working reliability. The deep voltage negative-feedback theory is used to improve the stability of drive current. The temperature control module effectively stabilizes the laser temperature, which reduces the laser output wavelength drift and light power fluctuation.Thirdly, the software design is introduced. It includes the main program design and the interrupt program design. The main program consists of six sub modules, which are sinusoid signal program, ramp signal program, DC signal program, LCD display program, A/D acquisition program and serial communication program.Finally, some driving tests of the quantum cascade lasers( the center wavelength is 4.76μm) was made. The driving parameters are as follows: the drive current range is 0-400 mA, the frequency of ramp signal is 10 Hz, the frequency of sinusoid signal is 5KHz. Experimental results show that the linearity of the drive current is 0.0068%, the long-term stability of the drive current is 4.99×10-5 within 240 hours, the light power stability is 5.07×10-4, the stable control process is 17 s, the temperature stability is 0.01℃. When the drive current is 330 mA, the laser temperature is 21.166℃, the output wavelength of the laser effectively matches with the absorption line of carbon monoxide. When the temperature is 21℃, the drift of wavelength at peak within 240 h is ±0.02 nm. Those results fully meet the driving requirements of the quantum cascade laser.