A Digital Pulse Drive Circuit for Continuously Modulated Semiconductor Laser

Abstract

A digital designing way of laser drive circuit for continuously modulate the frequency, pulse width and amplitude of the output of semiconductor laser has been demonstrated. Complex programmable logic device (CPLD) was utilized to generate square waves with tunable frequency, the accurate delaying chip and logic circuit which are digital controlled were used to generate electrical pulses with adjustable pulse width. The pulses were amplified by the laser diode driver. The maximum output current of the driver can be up to 600 mA. When the signal was used to drive the semiconductor laser, the shape of the pulses generated by the laser is identical with the electrical pulses. The repetition rate and pulse width of the laser pulse can be continuously adjustable from 1 to 10 kHz and 3 to 20 ns, respectively. Furthermore, the time of rising and falling edges for the laser pulse were less than 2 ns.