The Catastrophic Optical Damage Monitoring And Failure Mechanism Of Power Semiconductor Laser Diode Based On A Light Reflection Method

High-power semiconductor laser diodes are widely used in infrared illumination,laser printing,laser measurement,material processing,laser diode pump source.The advantages of these devices include high power conversion efficiency,large power output,cost efficiency,size and reliability.However,as power output has increased,issues with performance and reliability have arisen.The most common failure mode of large power semiconductor laser diodes is Catastrophic Optical Damage(COD).This is the main issue affecting the maximum optical output power and service life of highpower laser diodes.The importance of studying the mechanisms of COD in high power semiconductor laser diodes cannot be underestimated.In this dissertation,a light reflection method is employed to study in real time the transient COD processes of the output facets of high-power Ga As-based semiconductor laser diodes with a lasing wavelength of 808 nm.Utilizing a fibre optical measurement system,a simple and easy to operate monitoring technique was developed to analyze both transient and relatively long-term aging failure mechanisms of the laser diode samples.The principle of the technique is based on the sample's reflectance.Usually a probe beam is reflected by the sample's front facet,and its intensity is then measured by photodiode.A variation in the beam intensity is caused by a variation in the reflectance,which is related to the morphology of the device under tested.Using multiple analysis methods to study the relatively long-term aging failure mechanism of high-power semiconductor lasers bars that failed by working under pulsed current.A conclusion related with mechanical strain induced by thermal strain at the solder layer and the active region of central bars obtained via wide varieties of measurements,including thermal resistance by using thermal resistance tester,temperature measurements with thermocamera and leakage current monitoring with Emission camera.In summary,thermally induced strain and mechanical strain produced by the difference between the thermal expansion coefficients of the heat sink material and the laser diode bar chip,which eventually caused COD damage on the facet of laser diode bars,especially at the central bars.