【作者】 王云华；

【导师】 薄报学；

【作者基本信息】 长春理工大学 ， 光学工程， 2013， 博士

【摘要】 随着高功率半导体激光器在光纤通信、工业加工、宇宙航天、医疗卫生和国防军事等领域的广泛应用及研究,社会对高功率半导体激光器的需求越来越大。其中,腔面膜技术是研制半导体激光器的关键技术之一,腔面膜性能的优劣直接影响到半导体激光器的输出功率、功率效率、可靠性和稳定性等方面。本论文从半导体激光器的腔面退化机理和腔面光学膜的设计理论展开,以典型的808nm GaAs/AlGaAs高功率半导体激光器作为研究对象,提出了以ZnO薄膜作为腔面钝化膜,前腔面镀制单层SiO2增透膜,后端面镀制Si/SiO2高反射膜的方法,以获得高激光损伤阈值腔面光学膜,从而提高半导体激光器的输出功率和可靠性。主要研究内容分为下几个方面：(1)分析了半导体材料的表面态来源和表面态对激光器退化的影响,指出表面态引起的非辐射复合是GaAs/AlGaAs激光器腔面发生光学灾变损伤的主要根源。然后,详细介绍了等离子体清洗的基本过程和原理。最后研究了薄膜光学中的单层增透膜、多层增透膜以及多层高反膜的光学特性和设计原理,并对多层介质膜中的弱吸收情况进行了讨论。为设计和制备出高质量GaAs/AlGaAs激光器腔面光学薄膜提供了理论依据和参考。(2)采用射频磁控溅射设备,以辉光放电方式引入等离子体并对GaAs样品表面污染物和氧化层进行清洗。分别探讨了氩等离子体清洗技术、氢等离子体清洗技术以及氩、氢混合等离子体清洗技术对GaAs表面特性的影响。实验结果表明,三种等离子体清洗技术均能对GaAs样品表面进行有效清洗,其中氩、氢气混合等离子体清洗技术结合了化学反应和物理刻蚀的双重作用,对GaAs样品的清洗效果最佳。在氩气和氢气流量分别为10cm3·min-1和30cm3·min-1,工作压强为2.5Pa,溅射功率为20W,清洗时间为15min的氩、氢混合等离子体清洗条件下,GaAs样品的光致发光强度提高约140%,表面的As-O键和Ga-O键基本消失。(3)采用射频磁控溅射方法在GaAs (110)衬底上制备了ZnO薄膜,并通过低温PL和XPS等测试手段分析了ZnO薄膜对GaAs表面的钝化效果。结果表明,经ZnO薄膜钝化后的样品本征光致发光峰强度提高了112.5%,杂质峰强度下降了82.4%。XPS光谱表明ZnO钝化层能够有效抑制镓、砷氧化物的形成,GaAs表面的镓、砷原子比值由1.47减小到0.94。证实了在GaAs表面沉积ZnO薄膜是一种可行的表面钝化方法,为GaAs基光电器件性能的进一步提高提供了新的途径。(4)围绕808nm GaAs/AlGaAs激光器的腔面光学薄膜设计及其制备工艺展开研究。利用射频磁控溅射技术分别在激光器谐振腔的前后腔面上沉积单层ZnO钝化膜,然后在前腔面沉积单层SiO2增透膜,后腔面沉积三对Si/SiO2高反射膜,测试结果表明,在中心波长808nm处,增透膜和高反射膜的反射率分别达到6.7%和98.86%。808mGaAs/AlGaAs激光器的输出功率达到5.92W,ZnO薄膜钝化技术可使激光器的COD阈值提高约57%。更多还原

【Abstract】 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.更多还原