Power Supply and Currentmodulation Circuits for Semiconductor Lasers

Design and construct ion of a stable current supply with protect ion circu its are Abstract described. The reported circuit provides a high-stable and high-level current variable from 0.5 -1.2 A with the prot ect ion circu its to prevent over load cur ren t , voltage and off-range temperature operat ion. A detailed analysis of the circu it parameters is given and the time behaviors of the load voltage/current and shut-off voltage/current are presented. Theoret ical analysis shows a turn-on time of about 20 ns for the load current and a shut-off time of about 150 ns. The proposed scheme is verified both by simulat ion and by constructing a prototype. The prototype version of this circuit shows a good stability in load current, and the laser diode temperature can be monitored with an accuracy of about 1 degree. In addit ion, design and analysis of the cu rrent modula tor and switching circu it s for laser diodes are repor ted. Modulation process and different modulation techniques are explained in detail. Drive circuits for positive and negative intensity modulation are presented. Transient analysis for the proposed drivers is performed by using PSPICE software and the results are reported here. Evaluation of the resu lts indicates that the reported modulators can be used successfu lly for direct current modulations.