An Integratable Distributed Bragg Reflector Laser by Low-Energy Ion Implantation Induced Quantum Well Intermixing

An integratable distributed Bragg reflector laser is fabricated by low energy ion implantation induced quantum well intermixing.A 4 6nm quasi continuous wavelength tuning range is achieved by controlling phase current and grating current simultaneously,and side mode suppression ratio maintains over 30dB throughout the tuning range except a few mode jump points.

Wet Oxidation of Al_x Ga_(1-x)As/GaAs Distributed Bragg Reflectors

The wet oxidation of AlGaAs with high Al content in a distributed Bragg reflectors （DBR） is studied by scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. Some voids distribute along the oxide/GaAs interfaces due to the stress induced by the wet oxidation of the AlGaAs layers. These voids decrease the shrinkage of the Al2O3 layers to 8% instead of the theoretical 20% when compared to the unoxidized AlGaAs layers. With the extension of oxidation time, the reactants are more completely transported to the front interface and the products are more completely transported out along the porous interfaces. As a result,the oxide quality is better.

Dual-wavelength distributed Bragg reflector semiconductor laser based on a composite resonant cavity

We report a monolithic integrated dual-wavelength laser diode based on a distributed Bragg reflector （DBR） composite resonant cavity. The device consists of three sections, a DBR grating section, a passive phase section, and an active gain section. The gain section facet is cleaved to work as a laser cavity mirror. The other laser mirror is the DBR grating, which also functions as a wavelength filter and can control the number of wavelengths involved in the laser action. The reflection bandwidth of the DBR grating is fabricated to have an appropriate value to make the device work at the dual-wavelength lasing state. We adopt the quantum well intermixing （QWI） technique to provide low-absorption loss grating and passive phase section in the fabrication process. By tuning the injection currents on the DBR and the gain sections, the device can generate 0.596 nm-spaced dual-wavelength lasing at room temperature.

Au Microdisk-Size Dependence of Quantum Dot Emission from the Hybrid Metal-Distributed Bragg Reflector Structures Employed for Single Photon Sources

We investigate metallic microdisk-size dependence of quantum dot （QD） spontaneous emission rate and micro- antenna directional emission effect for the hybrid metM-distributed Bragg reflector structures based on a particular single QD emission. It is found that the measured photolumineseence （PL） intensity is very sensitive to the size of metMlic disk, showing an enhancement factor of 11 when the optimal disk diameter is 2μm and the numerical aperture of microscope objective NA=0.5. It is found that for large metal disks, the Purcell effect is dominant for enhanced PL intensity, whereas for small size disks the main contribution comes from plasmon scattering at the disk edge within the light cone collected by the microscope objective.

Modeling of resistance characteristics of a continuously-graded distributed Bragg reflector in a 980-nm vertical-cavity surface-emitting laser

The resistance characteristics of a continuously-graded distributed Bragg reflector（DBR） in a 980-nm verticalcavity surface-emitting laser（VCSEL） are modeled in detail.The junction resistances between the layers of both the p-and n-DBR mirrors are analysed by combining the thermionic emission model and the finite difference method.In the meantime,the intrinsic resistance of the DBR material system is calculated to make a comparison with the junction resistance.The minimal values of series resistances of the graded p-and n-type DBR mirrors and the lateral temperature-dependent resistance variation are calculated and discussed.The result indicates the potential to optimize the design of the DBR reflectors of the 980-nm VCSELs.

Spatial and spectral filtering of tapered lasers by using tapered distributed Bragg reflector grating

A 1040 nm tapered laser with tapered distributed Bragg reflector(DBR) grating is designed and fabricated. By designing the grating with tapered layout, the tapered DBR grating exhibits the scattering effect on side backward-traveling waves, thus achieving additional suppression of parasitic oscillation. Under the suppression of parasitic oscillation, the spatial and spectral characteristics of the tapered laser are improved. The experimental results show that a near-Gaussian far-field distribution and a kink-free P–I characteristics are achieved, and a single peak emission with a wavelength of1046.84 nm and a linewidth of 56 pm is obtained.

Photoluminescence and X-ray Diffraction of Distributed Bragg Reflector

Spectral and structural characteristics of distributed Bragg reflector (DBR) in vertical-cavity surface-emitting lasers were studied with photoluminescence and double-crystal X-ray diffraction measurement.The expected high quality epitaxial DBR structure was verified.In the X-ray double-crystal rocking curves of DBR the zeroth-order peak,the first and second order satellite peaks were measured.Splitting of diffraction peak appeared in the rocking curves was analyzed.The effects of introduced deep energy levels on the structural perfection and optical properties were discussed.

Numerical Simulation of an All Optical Flip-Flop Based on a Nonlinear Distributed Bragg Reflector Laser Structure

A new design for an all optical flip flop is introduced. It is based on a nonlinear Distributed Bragg Reflector (DBR) semiconductor laser structure. The device does not require a holding beam. An optical gain medium confined between 2 Bragg reflectors forms the device. One of the Bragg reflectors is detuned from the other by making its average refractive index slightly higher, and it has a negative nonlinear coefficient that is due to direct absorption at Urbach tail. At low light intensity in the structure, the detuned Bragg reflector does not provide optical feedback to start a laser mode. An optical pulse injected to the structure reduces the detuning of the nonlinear Bragg reflector and a laser mode builds up. The device is reset by detuning the second Bragg reflector optically by an optical pulse that generates electron-hole pairs by direct absorption. A mathematical model of the device is introduced. The model is solved numerically in time domain using a general purpose graphics processing unit (GPGPU) to increase accuracy and to reduce the computation time. The switching dynamics of the device are in nanosecond time scale. The device could be used for all optical data packet switching/routing.

增厚DBR型894 nm窄线宽VCSEL

垂直腔面发射激光器(VCSEL)是芯片级原子钟(CSAC)的主流光源,其光束质量会影响CSAC的各项性能。扩展VCSEL内部有效腔长能够以压缩冷腔线宽的方式压窄器件最终辐射激光的线宽,从而可以减小CSAC短时间内的计时频率噪声。根据所计算的VCSEL表面反射谱,将VCSEL中4层下分布式布拉格反射镜(DBR)的厚度由常规的四分之一波长增加至404 nm,压缩了VCSEL冷腔线宽,并生长了对应的外延结构,制备了通过增厚DBR扩展有效腔长的894 nm窄线宽VCSEL。测试结果表明,研制的VCSEL在90℃下波长为893.1 nm,功率为0.335 mW,线宽约为32 MHz,且具有稳定的偏振特性。

975 nm multimode semiconductor lasers with high-order Bragg diffraction gratings

The 975 nm multimode diode lasers with high-order surface Bragg diffraction gratings have been simulated and calcu-lated using the 2D finite difference time domain(FDTD)algorithm and the scattering matrix method(SMM).The periods and etch depth of the grating parameters have been optimized.A board area laser diode(BA-LD)with high-order diffraction grat-ings has been designed and fabricated.At output powers up to 10.5 W,the measured spectral width of full width at half maxi-mum(FWHM)is less than 0.5 nm.The results demonstrate that the designed high-order surface gratings can effectively nar-row the spectral width of multimode semiconductor lasers at high output power.

基于DBR的窄线宽光纤激光器研究进展

分布式布拉格反射镜(DBR)线性腔结构因其腔长较短、结构简单,具有工作稳定、不易跳模、抗干扰能力强和易于实现全光纤化的优点。因此,DBR单频光纤激光器是目前实现单频激光输出的主要选择。本文首先回顾了DBR窄线宽光纤激光器自诞生以来发展的历程,介绍了在实际应用需求的牵引下催生出的新技术和新思路。然后,归纳了近年来DBR窄线宽光纤激光器的国内外研究进展。最后,讨论了当前面临的问题与挑战,并对未来发展趋势进行了展望。

基于DBR结构的蓝光及白光GaN LED的制备及光学性能改善

为改善GaN基发光二极管(LED)的光学性能,设计并制备了具有高反射率与宽反射带宽的SiO_(2)/Ti3O5分布式布拉格反射镜(DBR)结构的蓝光和白光GaN LED。制备了具有不同周期数的DBR结构,其中,17周期DBR结构在400~660 nm波长内平均反射率超过99.3%,其反射带宽度达到231 nm。测试并比较了封装后的基于DBR结构的LED芯片的电学与光学特性。通过电流-光输出功率(I-L)特性测试,发现具有17周期DBR结构的蓝光LED的光输出功率比5周期的提升了6.7%,而白光LED的光输出功率则提升了9.7%。在约100 mA的直流注入电流下,蓝光和白光LED的最大光输出功率分别达到134.9 mW和108.4 mW。

AlGaInN/InGaN应变补偿DBR结构设计

设计了中心波长为520 nm的AlGaInN/InGaN应变补偿分布布拉格反射镜(DBR)结构,通过调节组分参数实现应变补偿,使DBR整体应变为0,采用传输矩阵法,计算了Al_(0.7)Ga_(0.3-x)In x N/InGaN DBR、Al_(0.8)Ga_(0.2-x)In x N/InGaN DBR、Al_(0.9)Ga_(0.1-x)In x N/InGaN DBR的反射光谱。通过对DBR结构参数进行对比,优化了其结构和反射性能。首先对比高低折射率层生长顺序,发现对于Al_(0.8)Ga_(0.14)In_(0.06)N/In_(0.123)Ga_(0.877)N DBR,先生长高折射率层时,反射率高达99.61%,而先生长低折射率层时,反射率仅为97.73%;然后对比奇数层DBR和偶数层DBR,发现两者的反射谱几乎重合,没有显著区别;通过研究DBR对数对反射率的影响,发现对数在20~30对时,反射率随着对数的增加明显上升,30~40对时反射率增长缓慢;最后研究了材料组分对反射谱的影响,发现Al组分高的DBR折射率差大,反射性能更优,而相同Al组分的AlGaInN中In含量越低反射率越高。考虑到DBR制备过程中可能出现的厚度和组分偏差,模拟了厚度和组分出现偏差时反射谱的变化,发现高低折射率层厚度每增加或减少1 nm,反射谱红移或蓝移4~5 nm;而组分的偏差使高反射带带宽和中心波长处反射率发生明显变化。本文的研究为AlGaInN/InGaN DBR的设计和制备提供了一定的理论参考。

532 nm响应增强的AlGaAs光电阴极

AlGaAs光电阴极具有响应速度快和光谱响应范围可调的特性,可被应用于水下光通信领域.为了解决AlGaAs发射层较低的光吸收限制其量子效率提高的问题,利用分布式布拉格反射镜(DBR)结构对特定波长光的反射作用,将透过光重新反射回发射层进一步提高吸收率,从而增强阴极在532 nm波长处的响应能力.通过求解一维连续性方程,建立了具有DBR结构的AlGaAs光电阴极光谱响应模型.采用时域有限差分法,分析了DBR结构中子层周期对数、子层材料以及发射层、缓冲层厚度对发射层吸收率的影响,对比了有无DBR结构AlGaAs光电阴极的光吸收分布.结果表明,周期对数为20、子层材料为Al_(0.7)Ga_(0.3)As/AlAs的DBR结构对532 nm光的反射效果最优.基于该DBR结构,发射层和缓冲层厚度分别为495 nm和50 nm时,发射层对532 nm光具有最佳吸收率.通过对外延生长的AlGaAs光电阴极进行激活实验,结果表明具有DBR结构的AlGaAs光电阴极在532 nm波长处的光谱响应率相比无DBR结构的AlGaAs光电阴极光谱响应率提升了约1倍.

垂直腔面发射激光器DBR的优化设计

模拟分析了垂直腔面发射激光器分布布拉格反射镜铝组分不同分布对价带的影响,并对两种不同结构的器件进行了测试,测试结果表明抛物线渐变结构可以有效降低价带的势垒,进而可以改善垂直腔面发射激光器的电流热效应,为实现室温连续工作打下基础。

MOCVD生长InP/GaInAsP DBR结构及相关材料特性

采用金属有机化学气相沉积(MOCVD)法InP衬底上成功地制备了GaxIn1-xAsyP1-y/InP交替生长的分布布喇格反射镜(DBR)结构以及与之相关的四元合金GaxIn1-xAsyP1-y和InP外延层。利用X射线衍射、扫描电子显微镜(SEM)、低温光致发光(PL)光谱等测量手段对材料的物理特性进行了表征。结果表明,在InP衬底上生长的InP外延层和四元合金GaxIn1-xAsyP1-y外延层77K光致发光(PL)谱线半峰全宽(FWHM)分别为9.3meV和32meV,说明形成DBRs结构的交替层均具有良好的光学质量。X射线衍射测量结果表明,四元合金GaxIn1-xAsyP1-y外延层与InP衬底之间的相对晶格失配仅为1×10-3。GaxIn1-xAsyP1-y/InP交替生长的DBR结构每层膜的光学厚度约为λ/4n(λ=1.55/μm)。根据多层膜增反原理计算得出当膜的周期数为23时,反射率可达90％。

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 Ga As/Al As超晶格替代 Alx Ga1 - x As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 85 0 nm.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 15 μm× 15 μm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 5 0 Ω 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 .

扭转 DBR 光纤激光器的偏振特性研究

研究扭转ＤＢＲ光纤激光器的偏振特性，并导出ＰＭＢ频率和偏振模方向的解析公式。

Effect of DBR Geometry on Reflectivity and Spectral Linewidth of DBR Lasers

The linewidths of InGaAs-GaAs-AlGaAs DBR lasers with varied DBR dimensional parameters are measured and analyzed. These lasers were built with different DBR grating lengths and depths in order to explore the effect of the size of the DBR on its coupling coefficient and reflectivity,and hence on the linewidth of the laser diodes. The linewidths were measured by employing a self heterodyne linewidth measurement system. The experimental and calculated data for DBR reflectivity and spectral linewidth are given. The relationship between these data and the dimensions of the DBR is analyzed. Based on this analysis,the effect of the DBR geometry on the linewidth of the lasers is explored. The results give useful information related to the design and fabrication of such DBR lasers.

AlAs/GaAs分布布拉格反射镜(DBR)的反射谱拟合与优化生长

对分布布拉格反射镜(DBR)的原理和特征进行了分析,使用传输矩阵方法计算了不同对数GaAs/A lAs反射镜的反射率曲线。利用分子束外延(MBE)设备生长了波长为920nm和980nm的半导体多层膜DBR反射镜,分析了实验测得的反射谱与理论拟合曲线之间的差异及其产生原因,实现了材料的优化生长,获得了反射率大于99%、中心波长和带宽接近理论计算值的DBR材料。该DBR的反射谱拟合与优化生长研究可应用于VCSEL和VECSEL激光器。