Design And Implementation Of Linear Frequency Sweep Laser Based On DFB Laser Array

Lidar ranging technology based on Frequency Modulated Continuous Wave(FMCW)is a non-contact,high-precision,high-efficiency,and large-scale absolute distance measurement technology with no blind spots.It has been widely used in geometric shape detection,optical fiber sensing,health monitoring,integrated optical path diagnosis and other fields.Among them,the linear tunable laser is a key component of FMCW lidar technology,and its performance such as light output power,linearity,line width,and frequency sweep width has a key impact on the application of FMCWbased optical coherent sensing systems.Its sweep linearity and sweep range affect the resolution of the system,its line width determines the system's farthest measurement distance and spatial resolution,and its volume and cost affect whether the system can be commercialized on a large scale.However,there is no such ideal linear tunable laser light source in the market.Therefore,the research on low-cost,miniaturized linear frequency sweep narrow linewidth single longitudinal mode laser is very urgent.In this thesis,a series-parallel distributed feedback(DFB)laser array chip based on Reconstruction Equivalent Chirp(REC)technology builds a control system that can achieve linear frequency sweeping,designs and develops a linear frequency sweep DFB laser based on a four-channel DFB laser array.The thesis first introduced the development of FMCW,and introduced the FMCW test system based on Michelson interferometer in detail.At the same time,the development and research status of linear frequency sweep light sources are described at home and abroad.The key chip processing technology used in the DFB laser array used in this thesisReconstructed Equivalent Chirp technology can effectively control the wavelength accuracy of the laser,high yield,low manufacturing cost,and suitable features such as large-scale commercial use.Therefore,the main body of this thesis first introduces the principles and advantages of REC technology.Next,the paper introduces the internal structure and characteristics of a four-channel series-parallel DFB laser array chip based on REC technology.By exploring the influence of the internal working temperature and injection current of the laser on its output wavelength,a new DFB laser wavelength tuning method is proposed,which is to control the internal working temperature of the laser while changing the injection current of the laser and realize the switching between the channels of the DFB laser array.In this way,not only the linear output of the laser wavelength is realized,but also the broadband tuning of the laser is realized through the switching of the array.Next,the thesis introduces the overall design scheme of the fourchannel linear sweep laser circuit drive system.The system includes control module,steady current module,temperature control module and power supply design module and other parts.Finally,we completed the PCB Layout according to the designed schematic diagram,and developed the linear sweep laser drive circuit module in kind.Then,we conducted a comprehensive test on the various performances of the fourchannel linear sweep laser.The test found that the module has good light output performance and stability.In a test environment where the ambient temperature is 25 ?and the drive current of each channel is 100 mA,the output optical power of the four channels is close to 0 dBm,and the side mode suppression ratio of each channel is higher than 40 dB,which proves The laser module has good single-mode performance and stability.Among them,the average wavelength interval between channels is 2.488 nm,which is only 0.48% relative error from 2.4 nm when designed.The measured results are in good agreement with the original design.This theis also uses the delayed selfheterodyne method to test the output linewidth of the laser,and the test shows that its 3dB linewidth is 5 MHz,which basically meets the linewidth requirements of the sensing system.Next,the thesis tested the stability of the laser injection current and got the ideal PIV curve.Finally,the thesis tested the laser's injection current change during the frequency sweep process,and verified its good sweep linearity.The 2x2 four-channel DFB laser array module developed in this dissertation has the characteristics of fast speed,high linearity,low cost and high integration.This module is oriented to a FM continuous wave-based sensor system.After further testing and improvement,it is expected to replace its signal light source,improve the overall performance of the sensor system and reduce manufacturing costs,and provide a basis for its large-scale commercial use.