纳米压印制作半导体激光器的分布反馈光栅

分布反馈(DFB)光栅的制作是半导体激光器芯片的关键工艺,通过纳米压印技术在InP基片表面涂覆的光刻胶上压印出DFB光栅图形,并分别通过湿法腐蚀和干法刻蚀技术将光栅图形转移到InP基片上。所制作的DFB光栅周期为240nm(对应于1 550nm波长的DFB激光器),光栅中间具有λ/4相移结构。采用纳米压印技术制作的DFB光栅相对于通常双光束干涉法制作的光栅具有更好的均匀性以及更低的线条粗糙度,而且解决了双光束干涉法无法制作非均匀光栅的技术难题。相对于电子束直写光刻法,采用纳米压印技术制作DFB光栅具有快速与低成本的优势。采用纳米压印技术在InP基片上成功制作具有相移结构的DFB光栅,为进一步进行低成本高性能的半导体激光器芯片的制作奠定了良好基础。     

全息光刻制备808nm分布反馈半导体激光器的光栅

实验优化设计了808 nm分布反馈(DFB)半导体激光器的二级布拉格光栅结构,介绍了808 nm DFB半导体激光器光栅制备的工艺过程。采用全息光刻方法和湿法腐蚀技术在Ga As衬底片上制备了周期为240 nm的光栅图形,全息光刻系统采用条纹锁定技术降低条纹抖动和提高干涉稳定性,腐蚀液中H3PO4、H2O2和H2O的体积比为1:1:10,腐蚀时间为30 s。光学显微镜、扫描电子显微镜(SEM)和原子力显微镜(AFM)测试显示,光栅周期为240 nm,占空比为0.25,深度为80 nm,具有完美的表面形貌及良好的连续性和均匀性。     

808nm DFB半导体激光器的光栅制备

实验优化设计了808nm DFB半导体激光器的二级布拉格光栅结构,介绍了808 nm分布反馈（DFB）半导体激光器光栅制备的工艺过程。采用全息光刻方法和湿法腐蚀技术在GaAs衬底片上制备了周期为240nm的光栅图形,全息光刻系统采用条纹锁定技术降低条纹抖动和提高干涉稳定性,腐蚀液采用H3PO4 : H2O2 : H2O (1 : 1 : 10),腐蚀时间为30s。光学显微镜、扫描电子显微镜（SEM）和原子力显微镜（AFM）测试显示,光栅周期为240nm,占空比为0.25,深度为80nm,具有完美的表面形貌,及良好的连续性和均匀性。     

宽温度锁定808 nm激光器阵列

为了提高808 nm激光器对固体激光器的泵浦效率，对其波长稳定性进行了研究。阐述了光栅设计的理论基础。将纳米压印、干法刻蚀及湿法腐蚀工艺相结合，制备了含有一阶光栅的808 nm分布反馈（DFB）激光器阵列。在准连续条件（脉宽为200μs，频率为20 Hz）下对所制备的激光器进行性能测试。测试结果表明：所制备的808 nm DFB激光器阵列的发射波长随温度的漂移系数为0.06 nm/℃，温度锁定范围可达70℃（-10～60℃），随电流的漂移系数为0.006 nm/A。     

975nm分布反馈激光器一级光栅的制备

优化设计了975 nm分布反馈激光器的一级布拉格光栅结构.将纳米压印技术与干法刻蚀工艺相结合制备周期为148 nm的光栅结构,通过优化调整刻蚀气体流量比、腔室压强和偏压功率等参数,得到了合适的光栅刻蚀工艺参数.扫描电子显微镜测试显示,光栅周期为148 nm,占空比接近50％,深度合适,表面形貌、连续性和均匀性良好.将所制备光栅应用于975 nm分布反馈激光器中,激光器输出性能良好,波长随温度漂移系数小,光栅对波长的锁定效果良好.     

电子束光刻制备1.5μm 波长的一级DFB激光器

英国 STC 及卡文迪斯实验室报导了采用高压电子束曝光、化学蚀刻配合 LPE 及 MOCVD外延技术,制备1.5μm InGaAsP 一级光栅的分布反馈(DFB)半导体激光器。该激光器采用一级分布反馈光栅,比起一般用的高阶光栅有较好的耦合效率及性能。一般的 DFB 激光器是采用全息曝光的方法制备光刻胶的周期光栅的,但由它得到的光栅     

具有表面二阶金属光栅的927nm分布反馈半导体激光器的研制

采用全息光刻和湿法腐蚀光栅技术,成功制备了表面二阶金属光栅宽条型分布反馈（DFB）半导体激光器,无需二次外延生长过程,实现了宽接触室温直流下大范围稳定单纵模工作。腔面未镀膜器件,在脉冲工作条件下,注入电流为2．28A时,单面输出功率大于600mW,斜率效率达0．37mW／mA,功率效率大于11％。在连续电流注入下,当注...     

基于表面曲线光栅的高功率窄线宽半导体激光器

随着智能感知技术的快速发展，高功率、窄线宽的半导体激光光源成为研究热点。通过在边发射半导体激光器件表面引入高阶曲线光栅，设计了一种独特的非稳谐振腔结构，可实现高功率和窄线宽。采用紫外光刻和电感耦合等离子体（ICP）刻蚀技术，制备了周期为6.09μm、占空比为0.66、刻蚀深度为500 nm的曲线光栅。在室温条件下，测得腔长为2 mm的器件的阈值电流为220 mA，连续输出功率为1.48 W，斜率效率为0.63 W/A。比较了法布里-珀罗激光器、直线光栅分布式反馈（DFB）激光器和曲线光栅DFB激光器的光谱，结果表明，曲线光栅对半导体激光器的模式选择起到了关键作用，有利于实现高功率DFB激光器的窄线宽单模输出。该器件具有制作工艺相对简单、性能优异、可靠性高等特点，具有广阔的应用前景。     

光栅衬底液相外延技术

光栅衬底液相外延是分布反馈激光器研制的关键技术之一。利用 Sn-In-p 和 GaAs 单晶作为光栅衬底表面的高温热保护盖片,有效地解决了光栅表面高温热损伤问题,在光栅表面重复地生长出了高质量的外延层,并以此为基础,研制出了DFB 激光器。     

湿法腐蚀DFB半导体激光器的均匀光栅的研究

论述了用湿法腐蚀电子束光刻的均匀光栅DFB激光器亚微米光栅的过程,研究了几种腐蚀液对半导体激光器外延材料中InP的腐蚀过程.用扫描电子显微镜(SEM)对其腐蚀情况进行了分析,通过调节腐蚀液HB1:HNO3:H2O的体积比,找到了对InP腐蚀的最佳配比(1:1:30)以及合适的腐蚀条件(室温23℃).利用这种腐蚀液得到的光栅图形可以满足DFB激光器的要求.     

Realization of dot DFB lasers

Dot lasers with first-, second- and third-order gain coupled distributed feedback (DFB) gratings have been realized by low damage dry etching in combination with wet chemical etching and epitaxial over-growth. This technique allows above room temperature (RT) operation of dot DFB lasers with dot diameters down to 85 nm. The laser spectra show the expected emission of gain coupled DFB lasers. Threshold current densities between 1.1 kA/cm/sup 2/ and 2.6 kA/cm/sup 2/ could be obtained depending on size of the active region. An improvement in T/sub 0/ could be demonstrated comparing 0-D/1-D/2-D lasers on the same wafer. Based on the dot grating geometry improvement of the side mode suppression ratio (SMSR) was observed for broad-area dot DFB lasers.     

High device yield and performance of InGaAsP MQW DFB lasers with absorptive grating

AR/HR-coated, loss-coupled, InGaAsP multiple quantum well distributed feedback lasers emitting at 1.55 mum are reported, indicating a high device yield of ~66% for the quarter of a two-inch wafer and a good reliability as long as 5000 h operation at 85degC with a constant power of 5 mW. The high device yield was achieved by the automatically buried InAsP absorptive grating formed during the heat-up process on InP corrugations and the uniform surface-facing upward wet chemical etching process.     

Integration of organic semiconductor lasers and single-mode passive waveguides into a PMMA substrate

Efficiently combining active and passive elements in integrated optics is a key ingredient for their successful employment. Here, we present the fabrication of an optimized PMMA substrate structure for improved coupling of laser light generated by organic semiconductor distributed feedback lasers into single-mode deep ultraviolet induced waveguides. For production, electron beam lithography on an oxidized silicon wafer and subsequent reactive ion etching is used to form the feedback grating of the laser. Afterwards, an aligned second electron beam lithography step on top of the grating allows the fabrication of a topographical step of 1.67 μm on the edges of the grating area. Metal is evaporated on this resulting master structure serving as a plating base for electroforming of a Ni tool. The tool is then used for hot embossing of the structure into PMMA bulk material. On a length of 500 μm the imprinted grating lines, having a period of 200 nm, are 100 nm wide and 60 nm high. Aligned deep ultraviolet exposure to induce a passive single- or multi-mode waveguide and co-evaporation of the active material Alq₃:DCM finish the coupling region. This structure optimizes the coupling of laser light generated in the laser structure into the passive waveguide. In combination with microfluidic channels, the laser light can be considered for sensing applications on a PMMA lab-on-chip system.     

CW performance of an InGaAs-GaAs-AlGaAs laterally-coupleddistributed feedback (LC-DFB) ridge laser diode

Single-mode distributed feedback (DFB) laser diodes typically require a two-step epitaxial growth or use of a corrugated substrate. We demonstrate InGaAs-GaAs-AlGaAs DFB lasers fabricated from a single epitaxial growth using lateral evanescent coupling of the optical field to a surface grating etched along the sides of the ridge. A CW threshold current of 25 mA and external quantum efficiency of 0.48 mW/mA per facet were measured for a 1 mm cavity length device with anti-reflection coated facets. Single-mode output powers as high as 11 mW per facet at 935 nm wavelength were attained. A coupling coefficient of at least 5.8 cm^-1 was calculated from the subthreshold spectrum taking into account the 2% residual facet reflectivity     

半导体/超晶格分布布拉格反射镜(DBR) 的分子束外延生长

用分子束外延技术(MBE)生长了以GaAs/AlAs超晶格替代AlxGa1-xAs所形成的P型半导体/超晶格分布布拉格反射镜(DBR)．此分布布拉格反射镜的反射谱中心波长为850nm．由实验表明,19个周期的反射镜获得了高达99％以上的高反射率．与此同时,采取自行设计的二次钨丝掩膜质子注入法制成15μm×15μm的正方形电流注入区,以此测定P型反射镜的串联电阻,克服了湿化学腐蚀法中腐蚀深度不易控制及侧面同时被腐蚀的缺点,实验得出此P型反射镜的串联电阻仅为50Ω左右．在生长过程中,发现在只含一个铝源的分子束外延生长系统中,生长这种半导体/超晶格反射镜相对其他半导体/半导体反射镜要节省很多外延生长时间,因此较适合应用于多层结构的光电器件中．     

Monolithic DWDM source with precise channel spacing

We report a low-cost manufacturing approach for fabricating monolithic multi-wavelength sources for dense wavelength division multiplexing(DWDM)systems that offers high yield and eliminates crystal regrowth and selective area epitaxy steps that are essential in traditional fabrication methods.The source integrates an array of distributed feedback(DFB)lasers with a passive coupler and semiconductor optical amplifier(SOA).Ridge waveguide lasers with sampled Bragg side wall gratings have been integrated using quantum well intermixing to achieve a fully functional four-channel DWDM source with 0.8 nm wavelength spacing and residual errors<0.13 nm.The output power from the SOA is>10 mW per channel making the source suitable for use in passive optical networks(PONs).We have also investigated using multisection phase-shifted sampled gratings to both increase the effective grating coupling coefficient and precisely control the channel lasing wavelength spacing.An 8-channel DFB laser array with 100 GHz channel spacing was demonstrated using a sampled grating with twoπ-phase-shifted sections in each sampling period.The entire array was fabricated by only a single step of electron beam lithography.