Laser temperature controller

Abstract

A laser temperature controller is disclosed for controlling the temperature of a laser device. The controller includes a bridge circuit connected to a thermistor device which is mounted on the laser package. The bridge circuit generates error signals representing a need for cooling or heating as the operating temperature of the laser rises or falls about a set threshold. A voltage conversion circuit converts the error signals to a positive or negative polarity voltage. The output of the voltage conversion circuit is applied to a pair of operational amplifiers which input the voltage and compare it to a set reference voltage. When cooling is required a first amplifier provides a biasing voltage to a transistor when a set threshold is exceeded. The associated transistor switches drive current to a thermoelectric device mounted on the laser package thereby, cooling the laser. Similarly, when heating is required a second amplifier and transistor switches current of an opposite polarity to the thermoelectric device, which heats the laser. The output signal from the voltage conversion circuit is also applied to a laser temperature alarm circuit which provides a visual indication and an alarm signal to a controller interface when a set threshold of laser temperature is exceeded.