A Compact SOI-Integrated Multiwavelength Laser Source Based on Cascaded InP Microdisks

We report on the performance of a compact multi- wavelength laser (MWL) source heterogeneously integrated with and coupled to a silicon-on-insulator (SOI) waveguide circuit. The MWL consists of four InP-based microdisk lasers, coupled to a common SOI wire waveguide. The microdisk lasers operate in continuous-wave regime at room temperature, with a threshold current around 0.9 mA and a waveguide-coupled slope efficiency of up to 8 muW/mA, for a microdisk diameter of 7.5 mum. The output spectrum contains four laser peaks uniformly distributed within the free-spectral range of a single microdisk. While thermal crosstalk is negligible, laser peak output powers vary up to 8 dB for equal microdisk drive currents, as a result of loss due to coupling with higher order modes supported by the 1-mum-thick microdisks. This nonuniformity could be eliminated by reducing the microdisk thickness.     

高效率半导体激光器波导层掺杂的优化设计

为获得高效率半导体激光器,理论分析并计算了p型波导层四种不同掺杂浓度分布对器件内损耗、串联电阻、阈值电流以及电光转换效率的影响,由此优化了p型波导层的掺杂浓度分布和厚度。根据计算及优化结果,p型波导层采取线性s杂分布,厚度为0.45μm,制备了腔长1200μm的980nm半导体激光器,其阈值电流为324mA,内损耗为1.62cm-1,串联电阻为136mΩ。当输入电流为1.98A时,激光器的斜率效率和输出光功率分别为1.05W/A和1.74W,对应的电光转换效率从未优化时的54.6%提高到58.4%。     

非对称异质波导半导体激光器结构

提出了一种非对称异质波导半导体激光器外延结构,即通过优化选择材料体系和结构厚度,对器件外延层的P侧限制结构和N侧限制结构分别设计,从而降低器件的电压损耗,使其满足高输出功率以及高的电光转换效率的要求.从载流子的输运和限制等微观机制出发,对器件的主要输出特性进行了理论分析和数值模拟,并以此为根据设计和制作了一种1060 nm In Ga As/Ga As单量子阱非对称异质波导结构半导体激光器,并对器件的主要输出特性进行了测试.实验结果表明,非对称异质结构是降低器件的电压降、增大限制结构对注入载流子的限制,提高半导体激光器电光转换效率的有效措施.     

大功率小垂直发散角980nm量子阱激光器

提出了一种新型非对称宽耦合波导结构,通过理论计算优化了结构中n型波导层和限制层厚度,并采用低压金属有机化学气相沉积方法生长了设计的器件结构.测试了器件的光电特性,1200μm腔长器件的阈值电流为590 mA,斜率效率为0.96 w/A,最大输出功率达2000mW;当注入电流为0.6 A时,其远场发散角为16.1°(θ⊥)×10.2°(θ//).实验结果表明:新型非对称宽耦合波导结构能实现器件大功率输出,有效减小器件远场垂直发散角,改善器件光束质量.     

Coupling Analysis of GaAs-Based Microdisk Lasers With Different External Claddings

In this paper, we analyze the coupling of light from a GaAs microdisk laser into a waveguide. Starting from an air cladding, we examine several configurations to couple light into the waveguide with different cladding structures aimed to foster light coupling into the waveguide: photonic crystal and metallic (plasmonic cladding). In these coupling schemes, we tried to optimize the coupling of the emitted light into the waveguide, while maintaining a reasonable quality factor to allow the lasing operation of the device. We show that a plasmonic layer, introduced beside the waveguide can lead to a significant improvement in the coupling efficiency, reaching an efficiency close to 80%.     

Selectively etched tunnel junction for lateral current and optical confinement in InP-based vertical cavity lasers

We demonstrate a thin, selectively lateral-etched, AlIn(Ga)As tunnel-junction (TJ) layer as a current and optical confinement aperture in the InP-based long-wavelength vertical cavity surface-emitting lasers (VCSELs). A high etch selectivity was demonstrated by etching the aperture a distance of several microns without affecting the surrounding InP etch-resistant layer. Edgeemitting lasers enclosing the TJ aperture showed high injection efficiency and low current spreading underneath the aperature. Single-mode continuous-wave operation of a 1.55-μm VCSEL was demonstrated successfully with a room-temperature differential efficiency of 21% using a 6-μm-wide TJ aperature.     

Optical mode converter integration with InP-InGaAsP active and passive waveguides using a single regrowth process

A new method for integration of optical mode converters with InP-based photonic integrated circuits is described and demonstrated. The mode converter is integrated to a Sampled Grating DBR (SG-DBR) laser to demonstrate integration and to facilitate accurate fiber-coupling loss measurements. The entire fabrication process requires a single MOCVD regrowth, making it compatible with low-cost integration with other photonic components. The mode converter utilizes a vertically tapered geometry and yields a record 86% coupling efficiency using a lensed, uncoated, single-mode fiber. Cleaved fiber to InP-based waveguide coupling loss sensitivity is measured to be better than 1 dB with /spl plusmn/ 1.85-/spl mu/m lateral fiber misalignment and /spl plusmn/1.5-/spl mu/m transversal fiber misalignment.     

Control of higher order leaky modes in deep-ridge waveguides and application to low-crosstalk arrayed waveguide gratings

In a lightwave circuit using a strongly confined waveguide, higher order leaky modes must be suppressed to obtain ideal characteristics, especially in arrayed waveguide gratings (AWGs). Propagation loss for higher order leaky modes in InP-based deep-ridge waveguides was investigated by simulation and experiment. A highly sensitive loss measurement method based on optical low-coherence reflectometry was used to determine the loss, and the relationship between the loss for the higher order mode and AWG crosstalk was investigated. Optimizing the deep-ridge waveguide parameters, especially the core thickness, the refractive index of the core, and the etch depth under the core, significantly reduced the propagation loss for the higher order leaky mode. The effective elimination of the higher order modes will enable fabrication of low-crosstalk AWG routers.     

Study of waveguide coupling efficiency in hybrid silicon lasers

This paper presents a new method to increase the waveguide coupling efficiency in hybrid silicon lasers. We find that the propagation constant of the InGaAsP emitting layer can be equal to that of the Si resonant layer through improving the design size of the InP waveguide. The coupling power achieves 42% of the total power in the hybrid lasers when the thickness of the bonding layer is 100 nm. Our result is very close to 50% of the total power reported by Intel when the thickness of the thin bonding layer is less than 5 nm. Therefore, our invariable coupling power technique is simpler than Intel＇s.     

聚合物波导光栅耦合器的衍射场仿真

为了实现横截面尺寸为50 m50 m的聚硅氧烷聚合物光波导的耦合转向问题,设计了一种表面覆盖高折射率包层的多层蚀刻光栅耦合器。首先,分析了影响聚合物波导光栅耦合器耦合效率的结构因素;然后,采用在光栅表面蚀刻高折射率层的方法,提高了聚合物波导光栅耦合器的耦合效率;接着,对不同的周期（范围:100~4 000 nm）和不同的蚀刻深度（范围:0~50 000 nm）进行排列组合,形成不同的光栅结构,基于时域有限差分法编写程序,遍历所有情况,得到不同光栅结构下的光场情况以及其耦合效率,找到使耦合效率最大的周期以及蚀刻深度。最后,设计了多层蚀刻的光栅耦合器,进一步提高耦合效率。当蚀刻深度为5 000 nm,光栅周期为2 600 nm时,带高折射率层的聚硅氧烷聚合物光波导均匀光栅耦合器的耦合效率达到最大,为17.2%。采用多层蚀刻的方式,对结构进行优化,其耦合效率能达到37.4%。为聚硅氧烷聚合物光波导在光互连中的实际应用提供了理论依据。     

Complex-Coupled DFB Laser Using a Buried SiO2 Grating

In this letter, we report a distributed feedback (DFB) laser having a dielectric grating formed by SiO and InP to explore both the large refractive index difference and the partial gain coupling. Epitaxy lateral overgrowth by metal-organic chemical vapor deposition is conducted to grow the top p-type InP waveguide layer in the dielectric grating template. An index coupling coefficient of about 250 cm is estimated on the laser vertical waveguide structure. The insulating nature of the dielectric grating also partially blocks the injection current flow and modulates the optical gain of the active quantum-well region underneath it. A prototype DFB laser was fabricated and showed a stable single-mode operation with a sidemode suppression ratio larger than 47 dB measured at room temperature and continuous-wave operation. The technology developed can also be used for other applications that require high efficiency grating structures.     

900nm三叠层隧道级联激光器的结构优化研究

采用金属有机化合物气相淀积方法生长了900nm的三叠层隧道级联激光器。针对隧道级联激光器存在工作电压高、材料各层的光场耦合等问题,分别采用δ掺杂、扩展波导等技术对激光器结构进行了优化,并通过模拟计算对隧道结耗尽区宽度进行了优化。通过优化隧道结δ掺杂的生长条件,得到n+GaAs的掺杂浓度大于1×1019/cm3,使工作电压下降1V;通过采用扩展波导,使垂直发散角由常规结构的35°减小到20°。将900nm的三叠层隧道级联激光器制作成条宽300μm、腔长800μm的条形激光器,采用同轴封装形式,在20A的脉冲工作电流下,输出功率达到55W,斜率效率达到2.9W/A,以上指标是普通激光器的3倍。     

Two-band lasing in epitaxially stacked tunnel-junction semiconductor lasers

Epitaxially stacked tunnel-junction laser hetero structures were grown by hydride metalorganic vapor-phase epitaxy in the system of AlGaAs/GaAs/In GaAs alloys. Based on such structures, mesa stripe lasers with an aperture of 150 s- 7 m were fabricated. The possibility of controlling the lasing wavelength by varying the active region thickness in each tunnel-junction laser structure was demonstrated. Independent two-band lasing at wavelengths of 914 and 925 nm (the difference frequency is 2.3 THz) was achieved at a maximum optical radiation power of 20 W in each band of the epitaxially stacked tunnel-junction semiconductor laser.     

Low-Footprint Optical Interconnect on an SOI Chip Through Heterogeneous Integration of InP-Based Microdisk Lasers and Microdetectors

We present a proof-of-principle demonstration of a low-footprint optical interconnect on a silicon-on-insulator (SOI) chip. The optical link consists of a heterogeneously integrated, InP-based microdisk laser (MDL) and microdetector, coupled to a common SOI wire waveguide. Applying an electrical current to the MDL resulted in a detector current up to 1 $mu$A.      

Dependence of Ti-diffused Er:LiNbO3 laser efficiency onwaveguide fabrication parameters and pump wavelength

The mode size, effective pump area, and coupling efficiency as function of initial Ti-stripe width W, diffusion temperature T, and initial Ti-stripe thickness H in c-cut Ti-diffused Er:LiNbO₃ waveguide laser have been studied theoretically, taking into account optical pumping λ_p=1.477 μm and 0.98 μm. The main features of the mode sizes in terms of these diffusion parameters were collected and, as compared with the experimental results, a qualitative agreement has been achieved. The effective pump areas exhibit both significant initial Ti-stripe width and diffusion temperature dependence, especially for W>9 μm and T>1050°C, whereas the initial Ti-stripe thickness can hardly give influence when pumping with λ_p=0.98 μm radiation. On the other hand, coupling efficiency is approximately unchanged with values 0.76-0.78 for λ_p=1.477 μm and 0.8-0.85 for λ _p=0.98 μm, indicating that there are no optimized values of these parameters to increase slope efficiency through coupling efficiency. Moreover, the 0.98 μm pumping reveal lower threshold and higher coupling efficiency than 1.477-μm pumping. Finally, the appropriate waveguide fabrication parameters were proposed for the fabrication of a more efficient laser     

InGaAsP thin-film microdisk resonators fabricated by polymer wafer bonding for wavelength add-drop filters

10-/spl mu/m-diameter InGaAsP thin-film microdisk resonators have been fabricated using polymer-wafer bonding with benzocylobutene. This wafer bonding process is to provide strong two-dimensional mode confinement in the waveguide and reduce the optical propagation loss. The measured resonance linewidth at wavelength 1.55 /spl mu/m is about 0.22 nm with a free-spectral range of 20 nm. The narrow linewidth and large free-spectral range make these devices conducive to the applications in dense wavelength division multiplexed systems.     

Multichip optical hybrid integration technique with planarlightwave circuit platform

A two-step bonding technique for optical device assembly on a planar lightwave circuit platform was developed, which consists of a chip-by-chip thermo-compression prebonding step and a simultaneous reflow bonding step. The technique was used to realize multichip optical integration on the platform. The characteristics of the bonding technique were examined by investigating its strength and accuracy. The bonding accuracies in the horizontal and vertical directions were 1.1 and 0.8 μm, respectively, with high bonding strength. The technique was first applied to a 3 chip integrated transceiver module and the 136 fabricated modules exhibited good performance. The average coupling loss between the laser diodes and the waveguide was estimated to be 4.1 dB and stable characteristics were observed during 1200 cycle thermal shock tests between -40 and 85°C. Next, the two-step bonding technique was used for a 4 channel laser diode module on which 8 optical device chips were integrated and a low coupling loss was achieved of better than 4.2 dB which is as good as that of the 3 chip integrated optical modules     

键合方法研制InAsP/InGaAsP量子阱1.3μm垂直腔面发射激光器

设计并研制了由InAsP/InGaAsP应变补偿多量子阱有源层、SiO2/TiO2介质薄膜和GaAs/Al(Ga)As半导体分布布拉格反射镜（DBR）构成的垂直腔面发射激光器（VCSEL) . 采用直接键合技术实现InP基有源层与GaAs基DBR的晶片融合,并经过侧向湿法腐蚀定义电流限制孔径和沉积介质薄膜DBR等关键器件工艺,研制出InAsP/InGaAsP量子阱垂直腔面发射激光器,其阈值电流为13.5mA,单模激射波长为1288.6nm.     

端面抽运DPAL三维模型及激光输出特性的模拟研究

根据激光三能级速率方程理论,考虑抽运光聚焦的空间分布,建立三维DPAL速率方程组的理论模型,结合激光系统运行的边界条件,通过数值方法,对模型进行求解,对端面抽运铷蒸气激光器的输出特性进行了详细分析,包括抽运光聚焦光斑半径、聚焦位置、蒸气池长度等参量对模式匹配效率、阈值抽运功率和斜率效率的影响。在模式匹配最佳时,计算了对介质长度对激光输出和阈值的影响。根据抽运光功率,以获得最大激光输出功率为目标,给出了激光器系统的优化参数,包括介质长度、抽运光聚焦在介质中的聚焦位置、输出耦合反射率。     

InP基稀释光波导特性分析

从InP基稀释光波导的基本模型出发,利用有限差分波束传播（FD-BPM）算法,推导了InP基稀释光波导的有效折射率,对其进行了数值计算;根据光传输损耗方程,分析了稀释波导传输损耗产生的原因;对稀释光波导中TE/TM模式传输进行了详细的数值分析和模拟计算,并分析了其模场分布曲线。