Study Of Short Pulse Seed Source With Semiconductor Laser

Benefiting from high beam quality,high stability,pulse width(PW)and pulse repetition frequency(PRF)that can be regulated by seed source,fiber laser based on pulse seed source with semiconductor laser and optical fiber amplifier is extensively applied in single photon detection,medical treatment,military,materials processing,and other fields.In the master oscillator power amplifier(MOPA)system,the output parameters of optical fiber amplifier,such as pulse width,repetition frequency,rise and fall time,are directly influenced by the output optical parameters of seed source.Therefore,the design of a high quality pulse seed source is the primary work of building a fiber laser system.Combined with the current pulse driving methods and technology,two kinds of pulse seed source with semiconductor lasers are presented in this thesis.One is the design of sub-nanosecond pulse seed source based on coaxial packaged semiconductor laser,and the other is the design of nanosecond pulse seed source based on butterfly packaged semiconductor laser.The design of sub-nanosecond pulse seed source based on coaxial packaged semiconductor laser,is composed of a power supply module,a short pulse generator module,a short pulse driving circuit module,and a laser source.The main function of the power supply is to provide the required voltage for other modules in the circuit.Digital signal generation is adopted in the short pulse generator,which is to generate the trigger signal with adjustable parameters.Under the driving of the trigger signal,thehigh-speed switch of MOSFET is opened and closed in the short pulse driver,which makes the semiconductor laser produce optical pulses.Performances of the pulse seed source were tested and the results showed that continuously adjustable pulse width ranging from 538 ps to 10 ns and pulse repetition frequency in the range of 500 kHz to 100 MHz were obtained,respectively.These seed pulses were injected into a fiber amplifier,and no optical pulse distortions and spectrums were found,which indicate that the seed source has a high stability.The design of nanosecond pulse seed source based on butterfly packaged semiconductor laser,includes a power supply module,a short pulse generator module,a short pulse driving circuit module,temperature control circuit module,and a laser source.Compared with the sub-nanosecond pulse seed source with coaxial packaged semiconductor laser,the temperature control circuit module is increased to the nanosecond pulse seed source with butterfly packaged semiconductor laser.The main function of this module is to make the laser work at a constant temperature and ensure its normal operation.Performances of the pulse seed source were tested.The results showed that the seed source achieved optical signals with adjustable pulse width ranging from 3.5 ns to 51 ns and pulse repetition frequency in the range of 5 kHz to 25 MHz,which have reached the expected goal.