Primary Research On Driving Circuit And Linewidth Reduction Of Low Power Semiconductor Laser

Semiconductor lasers which possess a series of advantages like broad tuning range, moderate output power, small size, long life, easy integration and direct current pump, are developed rapidly and applied widely. However,the typical semiconductor laser linewidth is on a magnitude of GHz and the central frequency is easily influenced by temperature or current, thus cannot fulfill the requirements of some research fields which demand laser coherence and frequency stability highly. Therefore, how to reduce the linewidth and stabilize the frequency of semiconductor lasers is still the hotspot of research nowadays. In order to obtain narrow-linewidth and stable-frequency semiconductor lasers, techniques like modification of the internal structure of the semiconductor laser, design of an external driving circuit, linewidth compression of external cavity etc. can be utilized. Starting from theoretical analysis, this thesis includes design and fabrication of an accurate driving circuit(including current-static module and temperature-static module). Also, the linewidth reduction of a semiconductor laser is realized based on V-shaped F-P cavity made by super-low expansion coefficient mini-crystal glass. The main contents are as follows.(1) The application value of narrow linewidth lasers and development potential of semiconductor lasers are summarized together with the linewidth reduction techniques and the latest research advancements focusing on semiconductor lasers.(2) Based on the operation properties of semiconductor lasers, an external driving circuit for laser diodes is developed. The driving circuit adopts the current-static control chip ATLS200MA103 and the temperature control chip TECA1-5V-5V-D to realize the accurate control of the working current and the temperature of the laser respectively. Parameter setting and controlling like temperature and current of the laser is realized by the main control circuit with a core of the single chip microcontroller C8051F007. After the relevant fabrication, the circuit is tested, the results of which show that the central frequency stability of the 635 nm semiconductor laser can reach a level of 10-4nm driven by this circuit(within a measurement time range of 10min).(3) The influence of the optical feedback effect on the semiconductor is analyzed. And detailed discussion and simulation are done focusing on the mechanisms of frequency locking and linewidth compression for semiconductor lasers using the method of F-P cavity optical feedback. Initial linewidth reduction is experimentally researched on a 635 nm semiconductor laser using a V-shaped F-P cavity made by super-low expansion coefficient mini-crystal glass. Measurement on the linewidth after compression is done by the confocal scanning F-P cavity interferometer with a result of 55.2MHz.