Study On High-Power Surface-Emiting Lasers

Optically-pumped vertical external-cavity surface-emitting semiconductor lasers(VECSELs) combining the advantages of both the surface-emitting lasers and thediode-pumped solid-state lasers, can produce near diffraction limited circular TEM00mode and high-power output. Due to the presence of the external-cavity, the frequencydoubling and mode-locking components can be inserted conveniently into the cavity toachieve efficient frequency doubling or mode-locking operation. As a novel kind ofsemiconductor laser resources, it can be used in the optical fiber communication, laserdisplay, laser medicine as well as biochemistry analysis and other fields.The history and the recent developments of the semiconductor lasers werereviewed. A new type of semiconductor laser—VECSELs was introduced. Comparedwith diode-pumped solid-state lasers and traditional surface-emitting lasers, theadvantages and characteristics of VECSELs were presented. The researches andapplications of it were summarized.The related basic theory of VECSELs was described. The structure of theVECSELs was introduced. The reflectivity formulas of distributed Bragg reflector(DBR) were derived using the transfer matrix method, and the reflectivity and reflectionbandwidth were simulated and analyzed with different pairs, different incident and exitmedium. The theoretical formulas of the optical field distribution and longitudinalconfinement factor of the periodic gain structure were derivated. The quantum wellstrained theory, critical thickness, gain spectrum and spontaneous emission spectrum ofquantum wells were introduced and calculated. The output characteristics of VECSELswere simulated and analyzed.The thermal managements of VECSELs were introduced. The experiments ofsoldering and liquid capillary bonding methods are used to bond the980nm VECSELchip to the surface of an optically transparent SiC heat sink. In order to obtaine a goodoptical surface of the etched substrate wafer, mechanical thinning and chemical etchingmethods are used to etch the wafers’ substrate.A VECSEL laser of an etched substrate wafer was realized, and its specificitieswere experimentally studied and discussed. First, the gain material properties of DBR reflectivity spectrum and the spontaneous emission spectrum were measured andcompared with the theoretical results. Then, the VECSELs output characteristics,including the output laser spectrum, the output beam quality and the output powerspectrum under different pump powers, were measured and analyzed in detail. At last,the reasons of laser thermal rollover were summarized according to the experimentalresults and the theoretical model.