| With the high power semiconductor lasers are widely applied and researched in the optical fiber communication, industrial processing, spaceflight aviation, medical service and national defense and military, etc. The demands for the high-power semiconductor lasers are getting greater and greater. Cavity facet coating is the key technology of semiconductor laser and its performance will affect output power, power efficiency, reliability and stability. Based on the degradation mechanism of laser cavity facet and the design theory of optical films, we mainly discussed how to plate the passivation coating, antireflection coating and high-reflection coating on the cavity facet of808nm GaAs/AlGaAs laser, respectively. The main research contents include:(1) We analyzed the origin of the surface states, and then discussed the effect of surface states on the cavity facet degradation of semiconductor laser. The results indicated that the non-radiative recombination caused by surface states was the main factor to cause catastrophic optical damage. Then, the basic process and principle of plasma cleaning was described in detail. Finally, we studied the optical properties and design theory of single-layer AR coating, multilayer AR coating and multilayer HR coating, respectively, and discussed the mechanism of weak absorption in multi-layer dielectric films. It provided a theoretical foundation and reference for the design and preparation of cavity surface films with a high laser damage threshold.(2) A new plasma cleaning process for GaAs surface using Ar/H2plasma was introduced. The process for Ar/H2plasma cleaning and surface activation was studied comprehensively to remove various contaminants, oxide layer on GaAs surface, and the influence of Ar/H2plasma under different plasma parameters was discussed in detail. The results show that GaAs samples treated under the condition of Ar/H2flow rate10,30cm3/min, sputtering power20W and cleaning time15min give the best cleaning effect, the photoluminescence intensity increases nearly140%, and the As-O and Ga-O bonds on the GaAs surface decrease greatly.(3)An ultrathin passivation layer of ZnO on GaAs substrate was prepared by RF deposition method to control the interface trap densities and to prevent the Feimi level pinning. The passivation performance of ZnO coating have been investigated by the photoluminescence (PL) and X-ray photoelectron spectroscopy (XPS).An increase in intrinsic PL intensity up to112.5%and a decrease in impurity PL intensity down to82.4%were observed after depositing ZnO coating compared to unpassivated GaAs surface. XPS measurement results show that the atomic concentration ratio of Ga/As (originally-1.47) has been modified to a value of～0.94, signifying an improvement of the surface stoichiometry in GaAs, Ga-O, As-O bonding are found to get effectively suppressed in RF deposited ZnO/GaAs interface structures. Research results indicated that the GaAs surface deposited with an ultrathin ZnO thin film was a feasible surface passivation method.(4) We mainly researched on the design and preparation technology of the various cavity facet coatings of808nm high-power semiconductor laser. The single-layer ZnO passivation coating was first deposited on the front and rear facets of the LD by RF magnetron sputtering technology, respectively. Then, a single-layer of SiO2as the antireflection coating was deposited on the front facet and three pairs of Si/SiO2layers as the high-reflection coatings were fabricated on the rear facet of semiconductor laser. The results of test demostrate that the reflectivity of AR/HR coatings is up to6.7%and98.86%at the wavelength of808nm, respectively. And the maximum output power of808nm GaAs/AlGaAs laser is5.92W,57%COD ability enhanced. |
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