图形分析法求半导体激光器端面减反膜的有效反射率

采用图解的方法,对镀制在半导体激光二极管(LD)端面的单层减反射膜的实际效果进行了分析.研究表明:在减反膜的反射率曲线的谱线宽度有限的情况之下,LD镀膜面上的有效反射率Reff一般均高于反射率曲线的最小值Rmin;对LD来说,存在着一个最佳波长λopt,当反射率曲线的最小值所处的波长λf与之相等时,Reff最接近Rmin.     

镀膜法获得的超辐射发光二极管的特性分析

在考虑了反射率与波长有关这一基本事实后，用图示方法对由镀膜法获得的超辐射发光二极管（ＳＬＤ）的特性进行了分析。结果表明：在判定减反射膜镀得好与不好的时候，最低反射处波长控制的准确性与最低反射率本身的大小都很重要；同时，也可以看到单面镀膜的ＳＬＤ振荡波长与增益峰值波长不重合的现象。     

渡膜法获得的超辐射发光二极管的特性分析

在考虑了反射率与波长有关这一基本事实后，用图示方法对由镀膜法获得的超辐射发光二极管（ＳＬＤ）的科特性进行了分析。结果表明：在判定减反射膜镀得好与不好的时间，最低反射处波长控制的准确性与最低反射率本身的大都很重要；同时，也可以香到单面镀膜的ＳＬＤ振荡波长与增益峰值波长不重合的现象。     

单层膜对超短脉冲的减反效果分析

利用多光束干涉方法分析了超短光脉冲通过单层介质膜的情况，研究了半导体激光器端面镀制的单层减反射膜中的电场变化，透过减反膜电场的时间特性，以及脉冲的能量反射率。     

光学薄膜的损耗测试与分析

随着激光基准系统和高精度激光测量系统的发展和应用,推动了超低损耗薄膜技术的发展,进一步控制损耗各分量的大小和分布,需要对光学薄膜总损耗进行测试分析.采用DIBS镀膜工艺在超光滑基底上镀制了高反膜和减反膜,给出了镀膜的工艺方法及工艺参数.通过分析时间衰减法测试总损耗的原理,分别采用时间衰减法和频率扫描法测试了光学薄膜的总损耗,在632.8nm波长点的测试结果为:高反膜层吸收为19.6×10-6,反射率达到99.996 86%;减反膜层总损耗为78×10-6.最后对光学薄膜总损耗的构成和工艺改进进行了探讨.     

等离子体增强化学气相沉积端面减反膜的研究

利用等离子体增强化学气相沉积(PECVD)技术制作半导体有源器件端面减反膜的方法简单易行,且适合进行大规模在片制作.采用1/4波长匹配法对减反膜的折射率、膜厚及其容差进行了理论设计,并在选定折射率下,对PECVD的沉积速率进行了测量.在此基础上,制作了1.31 μm InGaAsP氧化膜条形结构超辐射发光二极管,通过测定输出光谱调制系数的方法确定出减反射膜的反射率为6.8×10-4,并且具有很好的可重复性.     

太阳电池减反膜的设计

设计良好的减反膜系,提高太阳电池的光电转换效率是太阳电池研制中的一个重要问题.文章从减反膜理论出发,利用计算机软件模拟分析,获得了单层膜、双层膜系反射率百分比与波长的关系,并给出了具体入射波长(即632.8 nm、800 nm)条件下膜的最佳厚度.采用PC1D软件模拟了覆盖减反膜的单晶硅电池的I-V曲线,证实电池转换效率大大提高.研究结果可应用于太阳电池的设计中.     

平面反射镜光学薄膜的制备

以薄膜原理为基础,通过Essential Macleod软件进行膜系设计.采用电子束加热蒸发的镀膜方式,利用设计工装制备了介质ZrO2-SiO2高反射膜层和金属铝反射膜层.介质高反膜层在1.064μm波长处的反射率达到95%,金属铝反射膜层的在3μm～5μm波段内的平均反射率超过95%.膜层的技术指标和环境适应性能具有优质的质量.     

色散效应对GaAs太阳电池双层减反射膜的影响

考虑双层减反射膜材料的折射率色散效应,采用光学干涉矩阵法计算了SiO2/ZnSe和SiO2/ZnS两种GaAs太阳电池双层减反射膜的反射率与波长的函数曲线,以及加权平均反射率随着顶层减反射膜SiO2厚度变化的函数曲线,并与未考虑色散效应的情况进行了对比.计算结果表明,色散效应对双层减反射膜的反射率有较大的影响,特别是对300～500nm波长范围的影响更大,且对不同材料的减反射膜的影响也是不同的.与未考虑色散效应的情况相比,考虑色散效应后,SiO2/ZnSe双层减反射膜的最小加权平均反射率从1.14%增加到1.55%,而SiO2/ZnS双层减反射膜的最小加权平均反射率却从1.49%减小到1.46%.     

用于月基极紫外(EUV)多层膜样片反射率测量的小型真空试验台

用于探月二期工程的极紫外相机采用多层膜反射镜作为光学元件,多层膜反射镜整镜镀膜之前需进行样片镀膜并检测从而完善并确定镀膜工艺。本文介绍了搭建的一台样片反射率测量的小型真空试验台。该试验台由激光等离子体(LPP)光源系统、Mcpherson247单色仪、真空样品室探测系统、数据采集及处理系统组成。工作波段为1～120nm,光谱辐射稳定性好于±1%/h,角分辨率误差为0.015°。用本实验台对多层膜样片进行不同波长反射率测量,测量入射角一定时对不同波长的反射率曲线,根据测量结果完善多层膜镀膜工艺。     

Accurate measurement of reflectivity over wavelength of a laserdiode antireflection coating using an external cavity laser

A method for measuring laser diode facet antireflection coating over wavelength is presented. The laser diode is coupled to a wavelength-selective external cavity, and laser threshold current over the wavelength region of interest is measured. The coating reflectivity over wavelength is derived from the threshold current data. Reflectivities as low as 1×10^-5 have been measured with good fit over wavelength to an ideal single layer coating. The net external cavity feedback is also determined. An estimate of the accuracy of the reflectivity measurement is made     

Filter-response line shapes of resonant waveguide gratings

The line shape symmetry properties of planar dielectric resonant waveguide-grating filters are theoretically characterized for both TE and TM polarization. Classical antireflection theory is applied to the design of guided-mode resonance filters and it is shown that the symmetry of the line-shape response is determined by the location of the resonance relative to the minimum of the antireflection band. The conditions that allow a single dielectric layer to simultaneously function as both a waveguide grating and as an antireflection thin film are presented. Single-layer antireflection waveguide gratings are shown to yield highly symmetrical filter-response line shapes with suppressed sideband reflectivity and 100% reflectivity at the resonance wavelength. The parametric locations of the symmetrical line-shape responses are predicted approximately by solving the resonance-location equation with the grating thickness set equal to a multiple of a half-resonance-wavelength. Graphical representations of these solutions are provided. Symmetric waveguide-grating filters are shown to yield symmetrical line shapes with near-zero sideband reflectivity, whereas asymmetric filters produce symmetrical line shapes but suffer from increased sideband reflectance that increases as the asymmetry of the filter grows. Numerous calculated examples are presented to demonstrate that ideal reflection filters can be designed by combining thin-film antireflection effects and resonance effects in a single dielectric layer     

Effect of antireflection coatings and coverglasses on silicon solar cell performance

The high reflectivity of the polished silicon surface of the newer N⁺/P silicon solar cells has emphasized the need for properly designed antireflection coatings to obtain improved solar cell performance. The problem is complicated by the facts that solar cells are generally tested in air, but are for their final application covered with a glass or quartz slide which is adhesive-bonded to the cell surface, and further, that solar cells operating in a nuclear particle radiation environment change their spectral response and are frequently optimized for performance at the end of design-life. Experiments have been performed to explore the antireflection characteristics of thin films of silicon monoxide which have been evaporated on the solar cell surface. The effect of the antireflection coating thickness on cell response as a function of wavelength has been determined and the improvement in cell short circuit current for Air Mass Zero space sunlight evaluated. Included in this study was the evaluation of the antireflection characteristics after the application of a coverglass with adhesive over the antireflection coating. For comparison, coverglasses were also applied to bare cells with no antireflection coating present. In all cases the various coating comparisons were based on the cell short-circuit current performance in Air Mass Zero sunlight.     

1.5 μm GaInAsP angled-facet flared-waveguide traveling-wavelaser amplifiers

A broadband laser amplifier requires extremely low facet reflectivity (<0.1%). Previously, a low effective facet reflectivity of 0.05% was realized by an angle-facet structure in the 1.3-μm wavelength band. Present work reports an improved structure for the 1.5-μm wavelength band by flaring the waveguide ends near the angled facets. With a conventional antireflection coating of ~1% reflectivity, the measured effective facet reflectivity is less than 0.01% and the resultant devices have a fiber-to-fiber gain of 15 dB centered at 1.49 μm     

抗反膜设计改善半导体光放大器偏振不灵敏性的理论研究

通过理论分析和计算表明,适当地增加反射率,在同样的工作电流下,半导体光放大器(SOA)的增益将有所增大。合理地调节抗反膜的折射率和厚度,可以使TM模的反射率R_(TM)在一段波长范围内大于TE模的反射率R_(TE)。这样的反射率分布可以相对提高TM模的增益,在一定程度上改善SOA的偏振不灵敏性。通过抗反膜的设计来辅助解决偏振不灵敏的问题,可以使SOA在有源区和波导设计中获得更大的灵活性,更好地兼顾其他的性能要求。     

Ultra-low-reflectivity semiconductor optical amplifiers without antireflection coatings

High-performance, GaInAsP/InP tilted stripe ridge waveguide semiconductor optical amplifiers which require no antireflection coating to achieve reflectivities of less than -40 dB are demonstrated. This very low reflectivity is found to be both largely independent of polarisation and wavelength, and also easily reproducible from wafer to wafer.<>     

Low residual reflectivity of angled-facet semiconductor laseramplifiers

Ridge-waveguide angled-facet semiconductor laser amplifiers for the 1.5 μm band have been fabricated with facet angles of 7° and 10°. Gain measurements performed with a stable, computer-controlled setup have revealed gain ripples as low as 0.025 dB at 22 dB gain for a 10° device. This corresponds to a residual reflectivity of 1×10^-5. Results demonstrate that the residual reflectivity of angled devices with one-layer antireflection coatings can be as low as that for normal facet devices with highly controlled double-layer antireflection coatings     

Spectral investigation of multimode fiber Bragg grating based external-cavity semiconductor lasers

The output spectra of external-cavity semiconductor lasers (ECSLs) formed by using different antireflection (AR) coated laser diodes (LDs) with multimode fiber Bragg gratings (MMFBGs), are studied systematically. It is found that the side mode suppression ratio (SMSR) of the output spectra of ECSL is dependent on the relative position of the Bragg wavelength and the intracavity modes of the LD, and this effect is more apparent when the reflectivity of AR coating of LD is increased. Numerical simulations are provided to explain the experimental observations. Furthermore, the requirements of wavelength locking of ECSLs with MMFBGs are found to be different from those with single-mode fiber Bragg gratings (SMFBGs). The conditions of wavelength locking of the MMFBG-based ECSLs in terms of gain margin between the material gain peak and the gain corresponding to the selected Bragg wavelength, reflectivity of AR coating of LD and reflectivities of the Bragg wavelengths of MMFBG are comprehensively investigated, and compared with the experimental results.     

Measurement of the modal reflectivity of an antireflection coating on a superluminescent diode

A method for measuring the modal reflectivity of the antireflection coating applied to a laser diode is described and demonstrated. It is based on measurements of the Fabry-Perot modulation depth of the resulting superluminescent diode (SLD) output spectrum at the threshold current of the original laser. A modal reflectivity of less than2 times 10^{-4}has been obtained.