Design of driving and temperature control circuitry for VCSEL

Abstract

We design a laser driver and temperature control circuit based on the Field Programmable Gate Array (FPGA). Vertical-Cavity Surface-Emitting Laser (VCSEL) is the core device of the nuclear magnetic resonance gyroscope (NMRG). The accuracy of the laser output wavelength greatly affect the detection accuracy of NMRG. In order to improve the accuracy of VCSEL in this application system, in this paper we research the working principle of the laser and analyze the relationship between the laser output wavelength, the driving current and the laser operating temperature through theoretical analysis. We design and built the laser driving and temperature control circuit by using constant current source and the MAX1978, which use FPGA as the main control chip. By setting different voltage values, the laser output corresponds to different wavelengths. We analyze the result of experiment and theoretical calculate through the spectrometer. The result shows that the current regulation error is better than 0.03mA. For the laser temperature control circuit, we used the LTSPICE to simulate the PID control circuit of the compensation loop ,the finally result is consistent with the expected results.