Design and construction of Laser diode driver

Abstract

In the recent years semiconductor laser substitute the others types of laser in many fields and that is due to it is simplicity and easy to use. The main idea of this thesis is to design and construct of laser diode driver. Digital technique was used for driving the laser diode instead of the analogue traditional one. Digital technique offer the accuracy beside the tunability of the laser diodes, so with the same driver it is possible to drive different laser diodes which have different specification. The circuit was able to drive the laser diodes fall in the range form 1m watt to 1 watt power or that have wavelength range from infra red to ultra violet region. Replacing laser diode can be done just by some change in software with out need to touch any things in the hardware. To achieve this goal an interface card was used beside the main driver circuit, which enables the personal computer (PC) to control the laser diode operating current and other parameters. One of the important parameters that affects the radiated output power of the laser diode is the ‫‪temperature .Through this design the PC is able to protect the radiated‬‬ ‫‪through what is known as closed loop control. In which the PC loads the‬‬ ‫‪diode laser with the suitable operating current and then waiting for the‬‬ ‫‪data coming from the feed back circuit to decide either to increase or‬‬ ‫‪decrease the operating current. Most of the laser diodes now days come‬‬ ‫‪with a photodiode attached with it. The photodiode represent the essential‬‬ ‫‪part in the feedback circuit, which give a good indication for the emitted‬‬ ‫‪power of the laser diode. The main objective of this design is to have a‬‬ ‫‪constant radiated power and to eliminate the negative affect of the‬‬ ‫.‪increasing of the temperature‬‬ ‫‬