Design Of VCSEL Laser Drive Circuit And Laser Frequency Stabilization For Atomic Optics

Vertical cavity surface emitting lasers(VCSELs)are widely used as light sources for precision optical instruments such as atomic clocks,atomic magnetometers,atomic gyroscopes,etc.due to their advantages of low power consumption,small size,and tunability.With the development of VCSEL technology,its application field has also expanded.Low-power VCSELs play an important role in precision instruments such as 5G communications and gyroscopes.In recent years,VCSEL is developing in the direction of high power and small volume.This VCSEL will be used in lidar and driverless cars.In order to drive the laser,according to the working requirements of VCSEL,a constant current source circuit with an output range of 0 ~ 2 mA is designed to drive VCSEL.The circuit design adopts the principle of negative feedback,which can output a stable voltage,which is converted into a constant current output after the voltage and current.To make the output current more stable,a field programmable gate array(FPGA)chip EP4CE10F17C8 is added to the circuit to form a control circuit.Finally,the output performance of the circuit is tested.The test results show that the current ripple coefficient is 0.01 and the current stability is ± 0.02 mA.Because the laser is susceptible to environmental influences and its output frequency shifts,it is very important to study the frequency locking of the laser.In this paper,the atomic absorption spectrum is used as a reference signal,combined with the FPGA chip and peripheral circuits to form a servo control system to achieve laser frequency locking.In the experiment,if you want to lock the laser frequency to the lowest point of the absorption line,first modulate and demodulate the laser to obtain the error signal.The FPGA uses an incremental PI control algorithm.After collecting the error signal,the feedback is obtained and fed back to the laser to achieve closed loop.After the frequency lock is achieved,let the laser run freely.Using the error signal at this time as a reference,the Allan variance is used to calculate the frequency lock stability.