Studies On Driving Sources Of Linear Frequency Sweep Semiconductor Laser

Linear swept optical technology based on tunable diode laser has been developing vigorously in recent years.Linear sweep technology is widely applied in laser ranging,pilotless,optical fiber communication,aerospace and other fields.The linear frequency sweep optical technique requires that the output optical frequency of a semiconductor laser varies linearly with time.In the process of laser direct current modulation,the optical frequency does not vary linearly with time.There will be a certain frequency shift in the process of frequency modulation,which will have an adverse effect on the subsequent application of measurement.Based on the situation that the direct current modulation will generate larger FM nonlinearity,a photoelectric feedback system is mainly introduced.This system can compensate for the dynamic sweep frequency process,thus improving the linearity and stability of the sweep frequency.This paper mainly studies and analyzes the modulation characteristics of DFB laser based on integral circuit and integral circuit in optoelectronic feedback system.The main work of this paper is as follows:1.The principle of light-emitting diode and the development of tunable diode laser are reviewed in detail.The method and technology of realizing FM continuous light by tunable diode laser are discussed.On this basis,the method of producing FM continuous light based on the photoelectric feedback system is introduced.2.The core part of semiconductor laser drive system with photoelectric feedback loop is the integral circuit.The principle of the active integral circuit and the parameters that affect the performance of the integral circuit are deeply analyzed,and the integral-Schmidt type circuit is designed in the light of the actual situation.For the first time in our research group,the integrated circuit design,simulation,PCB board drawing and circuit experiment test and laser drive test are completed.3.The modulation principle of injection current in DFB laser is studied.The frequency range and frequency modulation linearity of the laser under static steady voltage are determined by static point measurement.Based on the measurement data of static bias point,the appropriate working point and modulation range are selected.By changing the modulation frequency of the standard triangular wave,the influence of the different modulation frequency on the sweep range under the same modulation range is explored.The square wave and active integral circuit are used to modulate the laser,and compared with the modulation of standard triangle wave under the condition of variable control.In the case of 1kHz modulation frequency and [-200 mV,200mV] modulation range,the modulation range of DFB laser driven by standard triangular wave is 11.089 GHz,and the modulation range of DFB laser driven by active integrated circuit is 7.243 GHz.Finally,the photoelectric feedback system is built at the core of the integral-Schmidt type circuit,which is compared and verified under the open loop and closed loop conditions.