表面液晶-垂直腔面发射激光器阵列的热特性

液晶与垂直腔面发射半导体激光器(VCSELs)阵列结合可实现波长可调谐、偏振精确控制等,同时液晶的引入也会改变垂直腔面发射半导体激光器阵列的热特性,本文设计了表面液晶-垂直腔面发射激光器阵列结构,并开展了阵列的热特性实验研究.对比分析了向列相液晶层对VCSEL阵列热特性的影响,实验结果表明,1×1,2×2,3×3三种表面液晶-VCSEL阵列的阈值电流温度变化率最高可降低23.6%,热阻降低26.75%;同时,激光器阵列各发光单元之间的温度均匀性显著提高,出光孔与周围温差小于0.5℃.综上所述,VCSEL阵列中液晶层的引入不仅大大加速激光器阵列单元热量扩散,而且降低了有源区结温,提高了VCSELs激光器阵列热特性,为实现高光束质量的单偏振波长可控VCSEL激光器阵列打下了良好的理论和实验基础.     

宽范围可调谐内腔液晶垂直腔面发射激光器设计与研究

为增加可调谐激光器的波长调谐范围,提高系统的可靠性和稳定性,基于液晶的电控双折射特性,设计了一种中心波长为852 nm的内腔液晶可调谐垂直腔面发射激光器结构。分析了该结构获得宽范围波长调谐和单偏振稳定输出的物理原理,利用传输矩阵法进一步计算整个器件下不同液晶层厚度所对应的反射谱,得出不同液晶厚度和折射率下激光器的激射波长。结果表明,液晶可调谐激光器单偏振波长调谐范围达到31 nm,调谐效率大于10 nm/V。     

可调谐垂直腔面发射激光器支撑结构优化设计

基于微机电系统（MEMS）的850 nm可调谐垂直腔面发射激光器（VCSEL），设计了一种双曲线梁结构，以提升器件机械和调谐特性。通过分析传统等截面梁结构的受力情况，提出了双曲线结构优化设计，将梁结构端面的面积增大从而降低最大应力。理论仿真结果表明：优化后器件上反射镜的最大偏移量基本保持不变，支撑梁上下表面的最大应力分别降低了23.4%和17.0%，谐振频率增大了7.9%；当MEMS-VCSEL分别为半导体腔主导（SCD）结构和空气腔主导（ACD）结构时，波长调谐范围分别为16.6 nm和42 nm。该优化方式的优势在于不需要改变激光器的结构，同时可与其他优化方式兼容，具有一定的应用前景。     

具有宽调谐范围的微纳光机电系统可调谐垂直腔面发射激光器研究

基于微纳机械技术设计得到了可调谐垂直腔面发射激光器结构,将具有Al_0.8Ga_0.2As牺牲层结构的DBR反射镜制备成微纳光机电系统,并与多量子阱有源区光纵向耦合结构相结合.其中,微纳光机电DBR结构不再是简单的分布布拉格反射镜,而是对光波具有高调制作用的可动微纳机械反射镜系统,并在静电力作用下可以动态调谐VCSEL谐振腔的激射波长.实验结果显示,当激光器调谐电压从0 V增加到7 V时,对应激射波长将从968.8 nm蓝移到950 nm,整个调谐范围达到了18.8 关键词： 垂直腔面发射激光器 微纳光机械 波长可调谐     

基于导模共振滤波器的波长可调谐垂直腔面发射激光器的研究

基于光栅层控制光波传播耦合波方程,设计了能够实现共振波长可调谐的亚波长光栅导模共振滤波器.通过调谐空气层的厚度,滤波器可以实现波长75nm的调谐,线宽均小于或等于1nm.将共振波长可调谐滤波器与中心波长为1.55μm的垂直腔面发射激光器(VCSEL)集成,形成了激射波长可调谐VCSEL.研究发现激射波长调谐范围与共振波长可调谐滤波器相同,而且在相同空气层厚度下,激射波长可调谐VCSEL的激射波长和共振波长可调谐滤波器的共振波长相同.该VCSEL不仅可以选择激射波长还可对输出横向模式进行选择.     

垂直腔面发射激光器电、光特性分析

根据增益波导垂直腔面发射激光器(VCSELs)直接耦合的准三维理论模型,通过有限差分法对泊松方程、注入电流密度、载流子浓度和光场分布方程求自洽解,研究了垂直腔面发射激光器的电特性和光波导特性.计算结果表明,氧化限制层位置是影响激光器特性的主要因素之一,如果忽略N型DBR层的影响,将与实际的垂直腔面发射激光器有较大偏差.     

双波长垂直腔面发射激光器及特性研究

基于光子晶体技术在一维光子晶体带隙内引入缺陷态模式,并对激光器谐振腔内部电磁场分布和共振波长进行调制,从而将单一波长分裂为双波长输出.最终制备出了一种新的具有双波长光谱输出特性的垂直腔面发射激光器,缺陷层为Al_0.8Ga_0.2As材料,厚度为5λ/4.所得到的双波长输出光谱具有低吸收损耗、输出波长容易控制及同方向垂直输出特性.同时,通过调整一维光子晶体的折射率差和缺陷层厚度可以有效调谐双波长的间距及输出波段.所设计的双波长垂直腔面发射激光器结构同样 关键词： 垂直腔面发射激光器 光子带隙 双波长     

向列相液晶染料可调谐激光器的研究

对向列相液晶染料的可调谐激光器进行了光学特性研究. 以650 nm为中 心波长设计了SiO₂和TiO₂多层膜的一维光子晶体, 以激光染料与向列相液晶的混合物作为增益介质层, 制备了波长可调谐激光器.用Nd: YAG倍频脉冲激光器输出的532 nm激光抽运所制备的激光器样品得出如下光学特性: 激光发射波长随温度调谐范围为605.5---639.8 nm, 达到34.3 nm, 随电压调谐范围为634.5---619.5 nm, 达到15 nm. 发射激光每脉冲的阈值能量为12.3 μJ, 激光线宽小于1 nm.     

基于二维光栅的偏振无关波长可调谐垂直腔面发射激光器

为了能够实现垂直腔面发射激光器(VCSEL)偏振无关特性,提出了将偏振无关光栅与half-VCSEL集成的方法。基于严格耦合波法,分析了光栅参数对偏振无关二维光栅反射特性的影响,经过模拟计算,发现在光栅周期为691～719 nm、光栅宽度为408.73～467.60 nm时,偏振无关二维光栅有210 nm的高反射带宽。将偏振无关二维光栅与中心波长为1.55μm的half-VCSEL进行集成,得到了中心波长为1.55μm的偏振无关波长可调谐VCSEL,经过光学传输矩阵计算,可得该偏振无关波长可调谐VCSEL的波长调谐范围可达93 nm。     

N-DBR和双氧化限制层对VCSEL电、光、热特性的影响

根据增益波导垂直腔面发射激光器直接耦合的准三维理论模型，通过有限差分法对注入电流密度、载流子浓度、光场和热场分布方程求自洽解.研究了垂直腔面发射激光器的电、热和光波导特性，同时提出了一种具有双氧化限制层的增益波导垂直腔面发射激光器结构，并通过对比研究了N-型分布布喇格反射镜和双氧化限制层对增益波导垂直腔面发射激光器特性的影响.计算结果表明，如果忽略N-型分布布喇格反射镜的影响将与实际的垂直腔面发射激光器有较大偏差；双氧化限制层结构对激光器特性有较大的改善，它为增益波导垂直腔面发射激光器提供了一种降低阈值，抑制高阶横模的方法.     

基于悬臂梁的光纤光栅线性调谐器研究

分析了基于悬臂梁的光纤光栅线性调谐的基本原理及调谐公式,指出了调谐范围、调谐灵敏度和反射波谱展宽与悬臂梁结构的关系,并提出了优化方案.实验中选用适当尺寸的悬臂梁,对粘贴其上的光纤光栅的反射波长实现了线性调谐,并可对调谐范围、灵敏度等指标进行灵活控制.     

Single-mode and tunable VCSELs in the near- to mid-infraredInvited Paper

Single-mode, long-wavelength vertical-cavity surface-emitting lasers (VCSELs) in the near- to mid-infrared covering the wavelength range from 1.3 to 2.3μm are presented. This wide spectral emission range opens applications in gas sensing and optical interconnects. All these lasers are monolithically grown in the InGaA1As-InP material system utilizing a buried tunnel junction (BTJ) as current aperture. Fabricated with a novel high-speed design with reduced parasitics, bandwidths in excess of 10 GHz at 1.3 and 1.55 μm have been achieved. Therefore, the coarse wavelength division multiplexing (CWDM) wavelength range of 1.3 to 1.6 μm at 10 Gb/s can be accomplished with one technology. Error-free data-transmission at 10 Gb/s over a fiber link of 20 km is demonstrated. One-dimensional arrays have been fabricated with emission wavelengths addressable by current tuning. Micro-electro-mechanical system (MEMS) tunable devices provide an extended tuning range in excess of 50 nm with high spectral purity. All these devices feature continuous-wave (CW) operation with typical single-mode output powers exceeding 1 mW. The operation voltage is around 1 - 1.5 V and power consumption is as low as 10 - 20 mW. Furthermore, we have also developed VCSELs based on GaSb, targeting at the wavelength range from 2.3 to 3.0 μm. The functionality of tunable diode laser spectroscopy (TDLS) systems is shown by presenting a laser hygrometer applying a 1.84-μm VCSEL.     

新型结构可调谐全光波长转换器的理论与实验研究

可调谐波长转换器是智能化光网络中的关键光电子器件. 提出了一种基于半导体光放大器的环形激光器实现连续可调全光波长转换的方案，建立了该方案的理论模型. 理论计算和实际测定了不同条件下波长转换的输出特性，实验结果与理论计算基本符合. 实验中实现了40nm范围内连续可调、转换速率为2.5Gb/s的交叉增益调制型波长转换. 关键词： 可调谐波长转换 半导体光放大器 环形腔     

Transmission characteristics of Mach–Zehnder interferometer comb filter based on thermal operation

We propose and experimentally demonstrate switchable and tunable transmission characteristics of a Mach–Zehnder interferometer comb filter based on thermal operation. Its temperature characteristics are investigated to reveal a shift in the peak wavelength position from 0.003 to 0.004 nm/°C and a tunable range of wavelength spacing of 0.76–0.90 nm for maximum and minimum effective lengths, respectively. This configuration provides the unique advantages of an all-fiber structure, tunable wavelength spacing, switchable spectral peaks, independent tuning of the center wavelength and wavelength spacing of the spectral peaks, and low polarization sensitivity. It is relatively simple to fabricate and expected to have applications in temperature fiber optic sensors and multiwavelength fiber laser sources.     

Tunable optical add-drop multiplexer based on long-period fiber gratings for coarse wavelength division multiplexing systems

We propose and experimentally demonstrate a voltage-controllable add-drop multiplexer with a tunable coupler based on long-period fiber gratings (LPFGs). The tunable coupler is based on cladding mode coupling between two parallel LPFGs with divided coil heaters, which controls the resonant wavelength positions of the two LPFGs. The wavelength tunability of the tunable coupler is measured to be -0.45 nm/degrees C in the temperature range from 20 to 120 degrees C. The large tuning range of optical signals (approximately 50.54 nm) from 1502.32 to 1552.86 nm, which covers both the short (S) and the conventional (C) bands, is achieved. The channel isolation is as high as approximately 40 dB. It has several advantages, including a broad tuning range of wavelength in both the S- and C-bands, high channel isolation, no backreflection, and so on.     

Wavelength Tuning of Double-Cavity Micromachined Filter with Electrical and Thermal Actuations

We demonstrate double-cavity micromachined tunable filters with electrical actuations for both blue and red wavelength tuning. Electrical actuations for both shifts can be achieved by combining electrostatic and electro-thermal actuations below and above the breakdown voltage of p-n junctions in the micromachined cantilevers. The measured tuning range with the actuation is 8 nm for both tuning sides and the micromachined filter with a cantilever length of 80 μm exhibits a switching time of less than 115 μs for both turn-on and turn-off states. We also present the theoretical and measured temperature dependence of fabricated micromachined filters at various cantilever lengths, which experimentally gives us a temperature dependence of 0.14 nm/K for a cantilever length of 100 μm.     

Size Reduction of Tunable Micromachined Filters for High Speed Operations

The size reduction of tunable micromachined filters is carried out for high-speed wavelength tuning. We fabricated micromachined filters having a miniature structure with an air gap of 300 nm and a short cantilever of 45 μm, exhibiting fast response of below 3 μs.     

C-band three-port tunable band-pass thin film optical filter with low polarization-sensitivity

According to the oblique incidence characteristics of thin film narrowband filter, the stack of 100 GHz DWDM four cavities angle-tuned thin film filter has been designed and optimized. The two polarization modes’ central wavelengths of the thin film filter can be centered at the same one in oblique incidence, and it has a stable tuning range of 20 nm without the phenomenon of polarization central wavelength separation. Using this kind of angle-tuned thin film filter and the polarization beam-splitters, the tuning range of the angle-tuned thin film filter can be further expanded due to the reason that it can transmit only the s-polarization light. In this paper we also developed a three-port bandpass tunable filter device with new structure, which tuning range can cover the whole C-band and its adjacent channel isolation degree is high. The experiments show that the three-port tunable filter has an effective tuning range of 33 nm, and its adjacent channel isolation degree is more than 35 dB. It has a bright application opportunity for its flexibility and effective performance.     

Tunable fiber Bragg gratings for application in tunable fiber lasers

The resonance wavelength of the fiber Bragg gratings (FBGs) is tuned using two methods. Tunable FBGs are used as the selecting elements in the cavities of tunable lasers. An ytterbium-doped fiber laser with a wavelength tuning range of 1063–1108 nm and an output power of 6 W, a Raman fiber laser with a wavelength tuning range of 1252–1303 nm and an output power of 3 W, and an erbium-doped fiber laser with a wavelength tuning range of 1530–1580 nm are realized, and their characteristics are studied.