基于等离子体增强化学气相沉积技术的光电子器件多层抗反膜的设计和制作

针对光电子器件端面抗反镀膜的要求,研究了基于等离子体增强化学气相沉积(PECVD)技术的多层抗反膜的设计和制作.首先,对影响SiN_x折射率的因素进行了实验研究,确定了具有大折射率差的SiO₂/SiN_x材料的PECVD沉积条件.根据理论计算分析,设计了四层SiO₂/SiN_x抗反膜结构,能够在70 nm的波长范围内实现低于10^-4的反射率     

Graded index broadband antireflection coating prepared by glancing angle deposition for a high-power laser system

This paper reports that SiO₂ is selected to fabricate broadband antireflection (AR) coatings on fused silica substrate by using glancing angle deposition and physical vapour deposition. Through accurate control of the graded index of the SiO₂ layer, transmittance of the graded broadband AR coating can achieve an average value of 98% across a spectral range of 300--1850~nm. Moreover, a laser-induced damage threshold measurement of the fabricated AR coating is performed by using a one-on-one protocol according to ISO11254-1, resulting in an average damage threshold of 17.2~J/cm$^{2}$.     

Investigation on antireflection coatings for Al:ZnO in silicon thin-film solar cells

We numerically investigate the role of antireflection (AR) coatings, composed of SiO₂ and/or ZnO, in suppression of interfacial reflections in the presence of the transparent conducting oxide, Al-doped ZnO (AZO). Three structures are simulated: (a) AR coatings in organic light-emitting diodes (OLEDs) and flat panel displays, (b) AR coating located between the glass and the AZO, and (c) same as the case b except the involvement of another AR coating between the AZO and the amorphous silicon layers. The weighted average transmittance according to the AM1.5 solar spectrum, the photovoltaic transmittance (T_pv), suggests that there is no evident difference between the structures a and b, especially when the layer number of AR coatings is less than three. An effective way to improve T_pv is presented in the structure c, where T_pv is increased from 73.54% to 76.32% with a three-layered AR coating located between AZO and a-Si. It implies that the suppression of interfacial reflections, resulting from the considerable mismatch of refractive indices at the interface of AZO and a-Si, would benefit the efficiency improvement of silicon thin-film solar cells.     

Spectral characteristics for a fiber grating external cavity laser

A numerical investigation has been carried out on the influence of the antireflection (AR) coating of laser, the coupling efficiency of laser and fiber (), and the reflectivity of fiber grating (R _g) on the side-mode suppression ratio (SMSR) of the fiber grating external cavity laser (FGECL). The FGECL was fabricated by the assembly of the multimode Fabry–Perot (FP) laser chip and fiber grating. The results showed that the FGECL with a lower AR coating, higher and R _g exhibited a better SMSR. A comparison of the SMSR dependence on the and R _g showed that SMSR increased more rapidly with increasing than SMSR for R _g. These spectral characteristic studies of the SMSR dependence on the device parameters of the AR coating, , and R _g may provide useful device designs for the practical fabrication of a FGECL for use in dense wavelength division multiplexing (DWDM) applications.     

二维空气孔型光子晶体负折射平板透镜的减反层

提出并优化了由单排渐变介质波导构成的二维空气孔型光子晶体负折射平板透镜表面的减反层，改善了成像质量.二维时域有限差分模拟计算结果表明，采用减反层后，在入射角小于23°的范围内，在使得有效折射率n_eff=-1的工作频率处，光子晶体表面对从空气一侧入射的平面波的反射率可降低到1％以下. 关键词： 光子晶体 负折射 平板透镜 减反层     

Thorium free antireflection coating in MWIR region on Silicon optics

Most infrared transmitting optics have high refractive indices which in turn have high per surface reflection loss. So antireflection coating has very important role in increasing the transmission in the desired wavelength region. In this paper a study has been carried out on the design and fabrication of Thorium free antireflection coating effective for Silicon substrate in MWIR (3.6–4.9 μm) region. The wave band 3.6–4.9 μm is chosen for the reported work because the detected system used in MWIR region has a band selection filter effective in the same wavelength region. Comprehensive search method was used to design the multilayer stack on Silicon substrate. The coating materials used in the design were Germanium (Ge) and Silicon dioxide (SiO₂). The fabrication of coating was made in a coating plant fitted with Cryo pump system and Residual Gas Analyzer. The evaporation was carried out at high vacuum (2–6 × 10–6 mbar) using Electron Beam Gun and layer thicknesses were measured with crystal monitor. The result achieved for the antireflection coating was 96% average transmission in 3.6–4.9 μm band which withstood MIL-F-48616 environmental testing. This work provides an alternate antireflection coating on Silicon by replacing radioactive Thorium Fluoride, used as a coating material in most IR antireflection coating designs.     

Design and optimisation of high-brightness 980 nm laser diodes with distributed phase correction

Designs for 980 nm Al _x Ga_1–x As/In_0.2Ga_0.8As/GaAs high-power, high-brightness semiconductor lasers/amplifiers with distributed phase correction and short-cavity lengths (i.e. cavity lengths 560–1040 m) are presented. The proposed lasers/amplifiers employ a single mode feed waveguide coupled to a power amplifier with a laterally graded effective refractive index (GRIN) profile to control the lateral mode shape and phase. The lateral index of the power amplifier has a hyperbolic secant (HYSEC) profile, which can be approximately realised by tailoring the effective refractive index of the amplifier using a series of discrete etches. The epitaxial and structure designs of the laterally discretised GRIN lasers/amplifiers are presented. Finally, a method for improving the effective refractive index discretisation is described.     

ECRCVD技术淀积太阳电池的减反膜

本文报道了用电子回旋共振化学气相淀积(ECRCVD)技术实现了低温(50℃)淀积SiON/SiN膜作硅太阳电池减反射膜的实验研究.探讨了影响薄膜性能的主要工艺参数,设计了具有较佳抗反效果的双层减反膜,并对膜层的反射率和太阳电池参数进行了测定.结果表明:该减反膜具有良好的减反效果,能实现较宽波段范围内的均匀增透,使太阳电池短路电流密度提高了42%,电池转换效率提高了45%.     

基于时间控厚离子束溅射技术的宽带减反膜制备

 为了制备满足设计要求的宽角度、宽波段减反膜,利用离子束溅射沉积技术,在时间-功率控厚的模式下,对膜层沉积速率进行了精确修正。在实验中,利用时间-功率控厚的离子束溅射沉积技术,选择HfO₂和SiO₂作为高低折射率组合,在超抛ZF6玻璃基底上制备了宽角度、宽带减反膜,通过对实验后的透过率光谱曲线的数值反演计算,获得膜层厚度修正系数,初步得到了沉积速率随沉积时间变化的规律。利用修正后的沉积参数制备设计的膜系,在0°~30°入射角度下,600~1 200 nm波段的平均透过率达到99%以上。     

Optimization of facet coating for highly strained InGaAs quantum well lasers operating at 1200 nm

The optical output power of a laser diode can be enhanced by anti-reflection (AR) and high-reflection (HR) facet coatings, respectively, at the front and back facet. AR and HR coatings also serve the purpose of protection and passivation of laser diode facets. In this work, we have designed and optimized a single layer λ/4 thick Al₂O₃ film for the AR coating and a stack of λ/4 thick Al₂O₃/λ/4 thick Si bi-layers for the HR coating for highly strained InGaAs quantum-well edge emitting broad area (BA) laser diodes. Effect of the front and back facet reflectivities on output power of the laser diodes has been studied. The light output versus injected current (L–I characteristics) measurements were carried out on selected devices before and after the facet coatings. We have also carried out the numerical simulation and analysis of L–I characteristics for this particular diode structure. The experimental results have been compared and verified with the numerical simulation.     

Design, formation and characterization of a novel multifunctional window with VO2 and TiO2 coatings

A novel multifunctional window was demonstrated using VO₂-based thermochromic films with a TiO₂ antireflection coating. A strong enhancement in luminous transmittance of VO₂ was calculated using either a single layer or a double layer of TiO₂ for antireflection, with the double layer giving the better performance. A TiO₂ (25 nm)/VO₂ (50 nm)/TiO₂ (25 nm) structure, of which the film thickness has been optimized to a maximum integrated luminous transmittance (T_lum) by calculation, was formed on SiO₂ glass by sputtering in turn a V target in Ar+O₂ for VO₂ and a TiO₂ target in Ar for TiO₂. Optical properties were measured with a spectrophotometer, and the integrated solar and luminous properties were calculated based on the measured spectra. A maximum increase in T_lum by 86% (from 30.9% to 57.6%) was obtained for VO₂ after double-layer TiO₂ antireflection coating. The deposited VO₂ film on SiO₂ exhibits good thermochromism with a sharp optical transition at 58.5 °C, which decreased slightly to 57.5 °C after TiO₂ coating. The proposed window is the most advanced among those similarly reported in being multifunctional with automatic solar/heat control, ultraviolet stopping and possibly a wide range of photocatalytic functions in addition to a high value of the luminous transmittance. PACS 42.79.Wc; 78.20.-e; 71.30.+h     

Efficiency improvement of quantum well solar cell with the AuGeNi metallization and Si3N4 ARC design

This study demonstrates the power conversion efficiency enhancement on In_0.19Ga_0.81As/GaAs quantum well solar cells (QWSC). The solar cell structure was grown on n-type (100)-oriented GaAs substrate by using solid-source molecular beam epitaxy technique and divided into square pieces. In order to understand whether the eight quantum wells were grown or not, scanning electron microscopy (SEM), and secondary ion mass spectrometry characterizations were done at room temperature. After that, the Si₃N₄ antireflection layers were coated onto both two square pieces of In_0.19Ga_0.81As/GaAs QWSC structure and p-GaAs substrate at different temperatures by the radio frequency magnetron sputtering system. The optical properties of the Si₃N₄ coated and uncoated p-GaAs samples have been evaluated by means of ultraviolet-visible spectrometry measurements at room temperature. According to ultraviolet-visible spectrometry results, the best Si₃N₄ antireflection coated one was obtained at 100 °C substrate temperature. Thus, the In_0.19Ga_0.81As/GaAs QWSC structure with and without Si₃N₄ layer, which was coated at 100 °C substrate temperature, was selected for other measurements and processes. Moreover, the In_0.19Ga_0.81As/GaAs QWSC samples with and without Si₃N₄ antireflection coating were separately fabricated with different metallization materials for obtaining the solar cell electrical output parameters. AuGe and AuGeNi metallization materials were used for the fabrication processes. After fabrication, the electrical output parameters were extracted from the current-voltage measurements at room temperature both in dark and under AM1.5 – 1 Sun illumination. The proposed design which includes the AuGeNi metallization and Si₃N₄ antireflection layer enhanced the power conversion efficiency by 44.40%.     

Silicon solar cells with Al2O3 antireflection coating

The paper presents the possibility of using Al₂O₃ antireflection coatings deposited by atomic layer deposition ALD. The ALD method is based on alternate pulsing of the precursor gases and vapors onto the substrate surface and then chemisorption or surface reaction of the precursors. The reactor is purged with an inert gas between the precursor pulses. The Al₂O₃ thin film in structure of the finished solar cells can play the role of both antireflection and passivation layer which will simplify the process. For this research 50×50 mm monocrystalline silicon solar cells with one bus bar have been used. The metallic contacts were prepared by screen printing method and Al₂O₃ antireflection coating by ALD method. Results and their analysis allow to conclude that the Al₂O₃ antireflection coating deposited by ALD has a significant impact on the optoelectronic properties of the silicon solar cell. For about 80 nm of Al₂O₃ the best results were obtained in the wavelength range of 400 to 800 nm reducing the reflection to less than 1%. The difference in the solar cells efficiency between with and without antireflection coating was 5.28%. The LBIC scan measurements may indicate a positive influence of the thin film Al₂O₃ on the bulk passivation of the silicon.     

三硼酸锂晶体上1064 nm,532 nm,355 nm三倍频增透膜的设计

采用矢量法设计了三硼酸锂晶体上1064 nm、532 nm和355 nm三倍频增透膜,结果表明1064 nm、532 nm和355 nm波长的剩余反射率分别为0.0017%、0.0002%和0.0013%。根据误差分析,薄膜制备时沉积速率精度控制在 5.5%时,1064 nm、532 nm和355 nm波长的剩余反射率分别增加至0.20%、0.84%和1.89%。当材料折射率的变化控制在 3%时,1064 nm处的剩余反射率增大为0.20%,532 nm和355 nm处分别达0.88%和0.24%。与薄膜物理厚度相比,膜层折射率对剩余反射率的影响大。对膜系敏感层的分析表明,在1064 nm和355 nm波长,从入射介质向基底过渡的第二层膜的厚度变化对剩余反射率的影响最大,其次是第一膜层。在532 nm波长,第一和第三膜层是该膜系的敏感层。同时发现,由于薄膜材料的色散,1064 nm5、32 nm和355 nm波长的剩余反射率分别增加至0.15%、0.31%和1.52%。     

Amorphous Er2O3 films for antireflection coatings

This paper reports that stoichiometric, amorphous, and uniform Er2O3 films are deposited on Si(001) substrates by a radio frequency magnetron sputtering technique. Ellipsometry measurements show that the refractive index of the Er2O3 films is very close to that of a single layer antireflection coating for a solar cell with an air surrounding medium during its working wavelength. For the 90-nm-thick film, the reflectance has a minimum lower than 3% at the wavelength of 600 nm and the weighted average reflectances (400-1000 nm) is 11.6%. The obtained characteristics indicate that Er2O3 films could be a promising candidate for antireflection coatings in solar cells.     

Nanostructured porous SiO2 films for antireflection coatings

Thin films with a low refractive index play an important role in optics, optoelectronics, and microelectronics. In this study, we present nanostructured porous SiO₂ films fabricated by using a glancing angle deposition technique. These nanostructured porous SiO₂ films deposited at an angle of 85° show very low refractive indices of 1.08 at 633 nm. As an application, a four-layer antireflection coating for visible wavelength is designed and fabricated using SiO₂ material only. The normal incidence reflectance of the antireflection coating averaged between 400 and 800 nm is about 0.04%. The microstructure and the surface morphology are also investigated by using a scanning electron microscope.     

Ge1-xCx double-layer antireflection and protection coatings

The antireflection Germanium carbide (Ge_1-xC_x) coating, deposited using RF reactive sputtering, on both sides of ZnS substrate wafer has been developed. The infrared (IR) transmittance spectra show that the IR transmittance in the wavelength region between 8 and 12 μm for the designed system Ge_1-xC_x/ZnS/Ge_1-xC_x is greatly enhanced compared to that for ZnS substrate. In addition, the double-layer coated ZnS substrate is approximately four times as hard as uncoated ZnS substrate. This investigation indicates that a double-layer Ge_1-xC_x coating can be used as an effective antireflection and protection coating on ZnS infrared window.     

Evaporation of uniform antireflection coatings on hemispherical lenses to enhance infrared antenna gain

Infrared dipole-coupled bolometers receive radiation more efficiently when illuminated through a high permittivity, antireflection (AR) coated, hemispherical immersion lens. To maintain the enhanced responsivity for all illumination angles, the AR coating must be uniform over the hemispherical surface. An evaporation method for depositing a uniform AR coating on the hemispherical surface is presented. The lens is tilted relative to the source, which can be either electron-beam or thermal, and rotated throughout the deposition. Evaporation at an angle of 70° yields a uniform film with less than 10% thickness variation over a 120° full angle of the hemispherical surface. A theoretical model is developed and compared to profilometer measurements. In all cases, there is general agreement between theory and measurement. A single dipole is fabricated onto the flat surface of an AR-coated germanium immersion lens and the responsivity is measured for both substrate-side and air-side illumination. With a zinc sulfide (ZnS) single-layer AR coating, substrate-side illumination yields a broadside antenna response 49 ± 2.7 times greater than air-side illumination.     

Resonant cavity based antireflection structures for surface plasmon waveguides

The concept of antireflection coating in the theory of multilayer films is introduced to the two-dimensional metal–insulator–metal (MIM) structures to realize total transmission of optical energy at the waveguide discontinuities. The antireflection structure consists of a resonant cavity which is constructed by changing the insulator width of the waveguide. A numerical method is used to achieve the optimal design directly. A T-splitter with zero reflection is proposed, utilizing a cavity structure in the input waveguide. A transformer with enhanced transmission between different waveguides is presented for further validating the efficiency and generality of these cavity based antireflection structures. The simulation results show that such a structure can realize a perfect antireflection function.     

Plasmon based antireflection coatings containing nanostructured Ag and silica medium

The transmittance and scattering of the antireflection (AR) coatings based on nanostructured Ag and silica medium were enhanced by the exploitation of the localized surface plasmon resonance (LSPR). The transmittance and scattering values of AR coatings are relative to the annealing temperature, Ag concentration and thickness of AR coatings. The transmittance values of 95.7% and 97.2% of AR coatings with 0.10 wt.% Ag and annealed at 400 °C were obtained in the visible wavelength for a single-side and double-side coated glass slides, respectively. The enhanced transmittance and scattering of the AR coatings are primarily attributable to the large forward scattering of nanostructured Ag and the lesser refractive indices of Ag/SiO₂ coatings.