Study On Monolithic Integrated Dual-frequency DFB Laser Based Microwave Generation And Its Application

People has researched many kinds of lasers with different gain medium since the invention of laser.Semiconductor laser which uses semiconductor as the gain medium is an important research area among them.Semiconductor laser has been applied into many areas with its advantages of compact,reliable,direct modulation,long lifetime,etc.In the area of microwave photonics,microwave generation utilizing semiconductor laser has attracted much interest,because it has the advantages of high speed,low power consumption,low cost and high reliability.In the area of laser velocimetry,using dual-frequency semiconductor laser can reduce the influence of noise and improve the accuracy of the measurement.In this thesis,by using the monolithic integrated dual-frequency DFB laser based on reconstruction-equivalent-chirp technique,we have realized the microwave generation system and the laser velocimeter and have studied the properties of them.The main contents and results are as follows:(1)This thesis proposes a kind of microwave generation system based on the monolithic integrated dual-frequency DFB laser.The results of the experiments are given including the characteristics of original beat signals,injection locking,frequency up-conversion and phase noise.We can tune the frequency of the original beat signal by changing the current of master laser and slave laser.The tunable range of the beat frequency is 13 GHz to 40 GHz.By using the sideband injection locking technique,the quality of the generated microwave signals is enhanced.The linewidth of the microwave signal is reduced to 102 Hz,which has reduced 5 orders of magnitude compared to the original beat signal.The locking range of the sideband injection locking technique is 1.8 GHz.We study the optical spectrum of the laser and the electrical spectrum of the generated signals under the condition of frequency-doubled up-conversion.Besides,tunable frequency-doubled and frequency-quadrupled signals are achieved respectively.Finally,the phase noise of the microwave signal is-100.9dBc/Hz at 10kHz frequency offset.(2)This thesis proposes two kinds of laser velocimeters based on the monolithic integrated dual-frequency DFB laser.This thesis builds the platform of velocity measurement independently and realizes the one photodiode scheme and the two photodiodes scheme for velocity measurement.In the two photodiodes scheme,we realize the measurement of the direction of the movement,and the relative error of velocity measurement is 0.38%.In the one photodiode scheme,the relative error of velocity measurement is 1.1%,and we realize the velocity measurement under the condition of frequency-doubled up-conversion.