The Study Of Temperature Control And Drive Method About Low Power Semiconductor Laser Diode

Small power semiconductor lasers with the advantages of the small size, thelong service life and the easy modulation are widely used in all kinds of the opticaldetections and the analysis fields. Semiconductor lasers are often used as a lightsource and meanwhile the output optical power stability of laser has a direct impacton test results in some optical detection instruments, precision instruments andoptical analytical instruments. Recently, output optical power stability of domesticadvanced semiconductor lasers is up to1%-0.1%, however, the price of thesemiconductor lasers are thousands of dollars. The application cost is improved andlimit the use of the promotion is limited in the system design, however, commercialsmall semiconductor lasers can not reach the demand of the power stability ofdetection systems. Therefore, not replaced the laser diode as the premise condition, itis important and significant to improve the power stability of the light source outputin order to reduce the cost through enhancing the performance of the laser drivesystem.At present, the main factors that have the influence on the stability of LD outputpower include the stability of laser diode temperature and the stability of drivingcurrent. The technology target of the laser driving system is determined according tothe relationship of the influence, at the same time, the laser driving system isdesigned according to the target. The semiconductor laser driving system is mainlyconsisted of temperature control and current control. Using the principle of theclosed-loop negative feedback, the temperature control system is designed. Theelectricity is supplied for the temperature sensor with the constant current source sothat the laser temperature is converted to the voltage signal. It is achievable to controlconstantly the temperature of laser diode with the preamplifier circuit, differentialcomparison circuit and the proportional integral (PI) control circuit for driving thesemiconductor refrigeration device. Based on the principle of the closed-loop negative feedback, the constant current control is designed in this paper with thedriving current as the feedback signal.The assistant protection circuit is designed in order to ensure the stability andservice life of the laser including the temperature alarm circuit, the voltage limitcircuit, the delayed start circuit, the static protection circuit and the high currentalarm circuit.Finally, the experiments are designed in order to verify the system performanceaccording to the target. The temperature control system can last long time to keep thetemperature stability of the laser through the experimental verification. The deviationof temperature control is less that±0.02℃and the stability of driving current isbetter than0.1%. The design system can drive the laser with the rated power of5mW.The stability of light power output is better than0.2%, which reaches the designstandard.