Implementation and design of a low cost laser diode temperature controller

Abstract

It has become apparent that many commercial products and military applications require high-endurance laser diodes. Testing the life cycles of laser diodes currently requires large and expensive equipment that is overreaching in terms of the overall goal. Finding a cheap and minimalistic solution will provide a large sample size and allow for rapid testing of hundreds of lasers. This paper aims to log the process of designing and implementing a temperature controller system for laser diodes. This system will use a thermoelectric cooler (TEC) to harness control of the Peltier effect to maintain a constant temperature on a laser diode. The system will contain a combination of hardware and software that work intimately to provide an intuitive and simple method of testing the life cycle of a laser diode. The hardware will consist of a cooling fan, heat sink, TEC, and metal plate that constitute the testing apparatus. The software will work with a number of peripherals to provide a steady temperature during testing and rapid transition between different temperature set points. The software will need to control the drive current to the TEC using a software-based PID (Proportional-Integral-Differential) controller and function as a watchdog, capable of giving error messages and raising alarms. The primary purpose of the temperature controller is to perform endurance testing on laser diodes. It will also free up high cost equipment for precision needs, rather than endurance testing. This system aims to maintain a constant temperature within 0.5°C of the set point. This will guarantee a relatively stable and consistent light-intensity on the laser diode. The basic model of this temperature controller can be scaled and/or modified for applications other than laser diodes. This expands the potential impact of this system to be more consumer-friendly and will provide individuals with their own low cost temperature controller.