Research On Key Technologies Of High-Order Curved Grating Semiconductor Laser

Semiconductor lasers have the advantages of narrow spectral width,high Side-Mode Suppression Ratio(SMSR),stable wavelength and easy integration,and are widely used in modern industry,military defense,biomedicine and other fields.With the rapid development of lidar,laser communication,laser gyro and other information sensing and inertial guidance applications in recent years,a high-performance laser light source with high power,narrow spectral width and stable frequency is urgently needed.In response to this need,this paper investigates a semiconductor laser based on a high-order curved grating that can achieve watt-level power and sub-nanometer spectral width.Since no secondary epitaxy is required,the cost is low and the reliability is high,which has a broad application prospect.The main research of the paper is as follows:(1)To clarify the effect of high-order gratings on the light output characteristics of lasers.Based on the grating diffraction principle and coupling wave theory,MODE Solutions is used to simulate and analyze the effects of structural parameters such as duty cycle,etching depth,morphology,period and refractive index on the coupling characteristics of high-order surface gratings.The coupling coefficient of grating is effectively controlled,and the optimized grating parameters provide reference for subsequent device preparation.(2)Structural design and fabrication of high-order curved gratings.The unstable cavity structure is composed of curved grating and high reflectivity posterior cavity surface.The grating radius gradually decreases from the posterior cavity surface to the anterior cavity surface,and the grating period gradually increases from the middle to the edge.Its unique feature is that the beam is divergent and the geometric deflection loss is large,thus increasing the loss difference between different oscillation modes and improving the mode resolution.In other words,the higher-order mode is suppressed while the fundamental mode is resonantly stabilized and output,and at the same time,the spectral width is well limited and controlled within a certain range.In this paper,high-order curved gratings with standard morphology and high uniformity are prepared by ultraviolet lithography and Inductively Coupled Plasma(ICP)etching technology.(3)Preparation and test analysis of devices.The high-order curved grating semiconductor laser was successfully prepared by Plasma Enhanced Chemical Vapor Deposition(PECVD)deposition,magnetron sputtering electrode,cleavage packaging and other technological steps.At room temperature,the threshold current of the device with a cavity length of 2 mm is 220 m A,the continuous output power is 1.48 W,the slope efficiency is 0.63 W/A,the lasing wavelength is 980.55 nm,the spectral width is 0.121 nm,and the side mode suppression ratio is 32 d B at the injection current of 1 A.By comparing the spectra of Fabry-Pérot(FP)lasers,linear grating Distributed Feedback(DFB)laser and curved grating DFB laser,it is shown that curved grating plays a key role in the mode selection of semiconductor laser,which is beneficial to realize to the narrow spectral width and single mode output of high-power DFB laser.