外部光反馈作用下垂直腔面发射激光器的电光特性

研究了外部光反馈对垂直腔面发射激光器（VCSELs）电光特性的影响。通过计算光反馈参数对比了VCSELs与边发射激光器（EELs）的光反馈灵敏性。基于复合腔理论计算了存在外部光反馈时垂直腔面发射激光器的阈值电流及斜率效率等电光特性参数。实验结果表明,分布布拉格反射镜（DBR）反射率不同的VCSEL,在反馈率为10%的外部光反馈作用下,其阈值电流及斜率效率发生了不同程度的变化。实验结果有效验证了理论计算的结论。     

电泵浦垂直外腔面发射激光器振荡特性的理论分析及实验研究

对具有InGaAs/GaAsP量子阱周期增益结构有源区的980 nm电泵浦垂直外腔面发射激光器(EP-VECSEL)的振荡特性进行了理论分析及实验研究.模拟并分析了耦合腔条件下EP-VECSEL的振荡特性与其分布布拉格反射镜(DBR)及外腔镜反射率之间的关系,并根据理论分析结果对器件结构进行了优化设计.在实验上制备出具有不同外腔镜反射率的EP-VECSEL器件,并对其连续波(CW)振荡特性进行了研究.实验结果表明,有源区直径为300 μm的EP-VECSEL器件在外腔镜反射率为90 %时阈值电流为1.2 A,注入电流为4 A时连续激光输出功率为270 mW; 在外腔镜反射率为95%时阈值电流为0.9 A,4 A下输出激光功率为150 mW.实验结果与理论分析结论符合较好,说明本文采用的理论分析方法能有效模拟及优化EP-VECSEL器件的振荡特性.     

二维光子晶体对面发射激光器横模控制研究

垂直腔面发射激光器的单模输出特性在光网络数据传输光互连、光存储和激光打印中有重要的应用.传统的氧化限制型垂直腔面发射半导体激光器由于串联电阻大、发热严重而很难工作在单模状态.二维光子晶体结构可以有效地控制垂直腔面发射激光器的横向模式,使器件工作在单模状态下.从理论上系统研究了光子晶体垂直腔面发射半导体激光器的单模条件,成功设计了一组单模光子晶体垂直腔面发射半导体激光器,并通过常规工艺制作出功率0.6 mW、边模抑制比大于30 dB、阈值电流4 mA、远场发散角8.4°、不受电流注入影响的单模光子晶体垂直腔面发射半导体激光器.实验证明:光子晶体可有效地进行横模控制.     

高斜效率高功率850nm氧化限制型垂直腔面发射激光器

报道了MOCVD生长的高性能850nm氧化限制型垂直腔面发射激光器.研制出的氧化直径为9μm的激光器25℃时的斜效率和阈值电流分别为0.82mW/mA和2.59mA,激光器在23mA时输出16mW最大光功率.氧化直径为5μm的激光器25℃时的最小阈值电流为570μA,其最大饱和光功率为5.5mW.     

高斜效率高功率850nm氧化限制型垂直腔面发射激光器

报道了MOCVD生长的高性能85 0 nm氧化限制型垂直腔面发射激光器.研制出的氧化直径为9μm的激光器2 5℃时的斜效率和阈值电流分别为0 .82 m W/m A和2 .5 9m A,激光器在2 3m A时输出16 m W最大光功率.氧化直径为5μm的激光器2 5℃时的最小阈值电流为5 70μA,其最大饱和光功率为5 .5 m W.     

高铝AlxGa1-xAs氧化层对垂直腔面发射激光器的影响

针对可见光垂直腔面发射激光器的制备,通过湿氮氧化实验和测量微区光致发光谱分别研究了高铝组分AlxGa1-xAs的氧化特性及氧化产物的收缩应力对有源区的影响,结合器件结构设计确定了氧化限制层AlxGa1-x-As的铝组分和最佳位置,并制备出了低阈值电流的AlGaInP系垂直腔面发射激光器.     

980nm垂直腔面发射激光器的外延生长

模拟了垂直腔面发射激光器(VCSEL)的反射谱和量子阱增益谱,采用金属有机物化学气相沉积设备外延生长了980 nm的垂直腔面发射激光器,制作了氧化孔径为14 μm的内腔式氧化限制型VCSEL器件,其阈值电流为3.3mA,阈值电压为1.8V,斜率效率为0.387 W/A,室温直流电流为22.8 mA时,输出光功率为5 mW.     

高功率980nm垂直腔面发射激光器的温度特性

应变补偿量子阱结构因带宽大、增益高和波长漂移速度低等特点而成为近年来研究的热点.首次介绍了国内980 nm 高功率InGaAs/GaAsP应变补偿量子阱结构的垂直腔面发射激光器(VCSEL) 变温实验,测得脉冲条件下600 μm直径的器件在10-100℃温度范围内发射波长漂移速度为0.05 nm/K,阈值电流随温度变化呈现先缓慢下降后迅速上升的特性.结合VCSEL反射谱、PL谱和增益峰值波长漂移速度,对器件阈值电流特性进行了合理的分析和解释.连续工作状态下,测试得到器件峰值功率为1 W,根据波长与耗散功率的实验曲线及热阻计算公式,可估算出垂直腔面发射激光器热阻值为10 K/W.     

质子注入型光子晶体垂直腔面发射激光器制备

在光子晶体垂直腔面发射激光器中采用质子注入工艺,使台面工艺变成纯平面工艺,降低了光子晶体结构制备难度,简化了器件制备,提高了器件的均匀性。质子注入型光子晶体垂直腔面发射激光器中的光子晶体结构,在电流限制孔小于光子晶体缺陷孔时,仍能控制器件光束及模式特性,该结果可用于优化器件阈值电流,制备高性能低阈值电流基横模器件。实验所设计制备的器件,在注入电流小于12.5 mA时,阈值电流2.1 mA,出光功率大于1 mW,远场发射角小于7,有效验证了光子晶体结构在质子注入型面发射激光器中的光束改善及模式控制作用。     

高铝Al_xGa_(1-x)As氧化层对垂直腔面发射激光器的影响

针对可见光垂直腔面发射激光器的制备 ,通过湿氮氧化实验和测量微区光致发光谱分别研究了高铝组分Alx Ga1 - x As的氧化特性及氧化产物的收缩应力对有源区的影响 ,结合器件结构设计确定了氧化限制层 Alx Ga1 - x-As的铝组分和最佳位置 ,并制备出了低阈值电流的 Al Ga In P系垂直腔面发射激光器     

Light-current characteristics of vertical-cavity surface-emitting lasers with external optical feedback

The influence of external optical feedback (OFB) on the light-current characteristics of the vertical-cavity surface-emitting lasers (VCSELs) was investigated theoretically and experimentally. By calculating the OFB sensitivity parameter, the OFB sensibility of the VCSELs was compared with the edge emitting lasers. Based on the compound cavity theory, the light-current characteristic parameters of the VCSELs with external OFB, such as the threshold current and the slope efficiency, were calculated. The experimental results indicated that the threshold current of the VCSELs with different DBR reflectivities decreased to different degrees, accompanied with a decrease of slope efficiency when under 10% feedback ratio of the external OFB, which is in good agreement with the theoretical calculation.     

InGaAs vertical-cavity surface-emitting lasers

The authors give theoretical and experimental results for vertical-cavity surface-emitting lasers (VCSELs). The modeling is applied to the design of InGaAs VCSELs. A simple method to calculate the reflectivity of semiconductor stack mirrors with graded interfaces and compound metal/semiconductor stack mirrors is introduced. The theoretical predictions are compared to results from actual device measurements. A novel technique is introduced to determine material parameters: fabrication of in-plane lasers from VCSEL material. The procedure used to determine the optical mode in such an in-plane laser is described. Using the insight gained from modeling, the external efficiency was increased to >30% with a threshold current density of 1 kA/cm²     

Nonlinear dynamics of vertical-cavity surface-emitting lasers

The dependence of the transient response of a vertical-cavity surface-emitting laser (VCSEL) on its aperture size is investigated subject to direct current modulation and external optical feedback. It is shown that lasers with small aperture size suppress higher order bifurcations and chaos even under large-signal modulation and external optical feedback. Furthermore, the noise characteristics of VCSELs under the influence of external optical feedback are studied via the calculation of relative intensity noise. It is found that the level of external optical feedback for the onset of coherence collapse is high for devices with small aperture size. On the other hand, the small-signal response of lasers is also analyzed through the calculation of third-order harmonic distortion. It is shown that harmonic distortion is minimized in small devices. Therefore, VCSELs with small aperture size have better immunity to irregular response under direct current modulation and external optical feedback     

Current spreading and carrier diffusion in long-wavelengthvertical-cavity surface-emitting lasers

Current spreading and carrier diffusion in vertical cavity surface-emitting lasers (VCSELs) critically affect the threshold current density, transverse gain profile, and optical modal characteristics of the devices. We have numerically analyzed these effects for four popular long-wavelength VCSEL structures with wafer-bonded GaAs-AlGaAs Bragg bottom mirrors. The results show that current confinement for p-mirror VCSELs is approximately twice as effective as the corresponding n-mirror VCSEL's although the confinement factor for all practical VCSEL structures studied here is considerably lower than the “ideal” structure. Calculations also show a strong dependence of current confinement on device aperture size and a tradeoff between the optical modal property and the current confinement efficiency for different apertured devices     

Transverse-mode dynamics in directly modulated vertical-cavity surface-emitting lasers with optical feedback

Vertical-cavity surface-emitting lasers (VCSELs) with optical feedback are known to exhibit different transverse-mode regimes depending on the injection current. Close to threshold a VCSEL operates on the fundamental transverse mode, while for larger injection the dynamics is often multimode, with the optical feedback inducing either in-phase or anti-phase transverse mode oscillations. In this paper, we study numerically the influence of current modulation on these different feedback-induced transverse-mode regimes. The modulation amplitude and period are taken as control parameters. We find that the in-phase and anti-phase regimes are robust under weak modulation. As the modulation amplitude increases, there is a transition to a dynamics governed by the current modulation, where the total output power follows the injection current and there is either single-mode or in-phase multimode behavior. However, the effect of the current modulation depends on the modulation period. Under fast modulation, the laser cannot follow the modulation and the optical-feedback-induced effects are dominant. On the contrary, under slow modulation there is a superposition of modulation and feedback effects, with the total output following the modulated current and an underlying transverse-mode behavior mainly determined by the optical feedback. A resonant behavior was observed for modulation periods close to the internal oscillation period. In this case, current modulation induces pulsing output intensity with single-mode or in-phase multimode behavior.     

Investigation of polarization properties of VCSELs subject to optical feedback from an extremely short external cavity-part II: experiments

The effect of isotropic optical feedback from an extremely short external cavity on the emission properties of vertical-cavity surface-emitting lasers (VCSELs) is experimentally investigated. When changing the external cavity length a modulation of the total power and the wavelength emitted by the VCSEL is observed with a period of half the wavelength of operation of the device. When biasing the VCSEL around its solitary (without optical feedback) polarization switching (PS) current, PS between the two linearly polarized modes is observed by changing the external cavity length. This PS is found to occur through a hysteresis region. Our experimental results show a modulation of the PS currents and the hysteresis width when changing the external cavity length with a period of half the wavelength of operation. The experimental results are well explained by a two mode rate equation model.     

Uniform wafer-bonded oxide-confined bottom-emitting 850-nm VCSELarrays on sapphire substrates

Uniform bottom-emitting 850-nm vertical-cavity surface-emitting laser (VCSEL) arrays on sapphire substrates have been demonstrated using wafer bonding technology to transfer the epitaxially-grown VCSEL structures from GaAs substrates onto sapphire substrates. The uniformity of the VCSEL arrays were improved by placing thin oxide aperture at the standing wave node to reduce scattering loss for small aperture devices. The averaged threshold current of a 5×5 VCSEL array is as low as 346 μA, while the averaged external quantum efficiency approaches 57%. The maximum wall-plug efficiency is 25% and the single-mode output power is more than 2 mW under continuous-wave current excitation at room temperature. We have also demonstrated a large (10×20) VCSEL array with variations of threshold current and external quantum efficiency less than 4% and 2%, respectively     

850 nm垂直腔面发射激光器的辐射效应

为了探究850 nm高速垂直腔面发射激光器（Vertical-Cavity Surface-Emitting Laser,VCSEL）在空间辐射环境中的退化规律与机制,开展了10 MeV质子和γ-射线辐照实验,获得了光功率和阈值电流退化规律,分析了辐射导致VCSEL参数退化的物理机理,此外,还开展了236 h的电注入退火研究。研究结果表明:VCSEL对γ射线导致的总剂量效应不敏感,且在一定剂量范围内光电特性由于沉积能量促进了量子阱界面附近的晶体有序而产生了一定程度的恢复:但是在质子辐照下,VCSEL的阈值电流和外量子效率发生了不同程度的退化,计算获得阈值电流损伤因子为1.468×10?15 cm2/p。经过20 mA注入增强退火后,阈值电流恢复了20%,25 mA注入电流下,光输出功率恢复了10%。阈值电流和外量子效率的退化归因于质子辐照引入的非辐射复合中心。这些实验结果为VCSEL及包含VCSEL的数据通信与仪器的系统在恶劣空间辐射环境下的应用提供支持。     

Influence of optical feedback time-delay on power-drops in vertical-cavity surface-emitting lasers

The influence of optical feedback time delay on the average period of low-frequency fluctuations (LFF) in external cavity vertical-cavity surface-emitting lasers (VCSELs) is studied experimentally. The regularity of power dropouts is shown to increase with increased external cavity length. Coexistence of LFF and stable operation is observed when the external cavity length is close to the VCSEL coherence length.