Current self-distribution effects in oxide-confined vertical-cavity surface-emitting lasers

We develop a self-consistent electro-optical model for oxide-confined Vertical-Cavity Surface-Emitting Lasers, including optical polarization and spin-flip dynamics. When subject to large signal modulation, current self-distribution effects reduce the amount of spatial-hole burning in the device, leading to a reduced overshoot during transients and an increased damping of the relaxation oscillations.     

Power dissipation in oxide-confined 980-nm vertical-cavity surface-emitting lasers

We presented 980-nm oxide-confined vertical-cavity surface-emitting lasers (VCSELs) with a 16-μm oxide aperture. Optical power, voltage, and emission wavelength are measured in an ambient temperature range of 5℃ C-80℃. Measurements combined with an empirical model are used to analyse the power dissipation in the device and the physical mechanism contributing to the thermal rollover phenomenon in VCSEL. It is found that the carrier leakage induced selfheating in the active region and the Joule heating caused by the series resistance are the main sources of power dissipation. In addition, carrier leakage induced selfheating increases as the injection current increases, resulting in a rapid decrease of the internal quantum efficiency, which is a dominant contribution to the thermal rollover of the VCSEL at a larger current. Our study provides useful guidelines to design a 980-nm oxide-confined VCSEL for thermal performance enhancement.     

Radiation fields from whispering-gallery modes of oxide-confined vertical-cavity surface-emitting lasers

Near- and far-field radiation patterns are analyzed for whispering-gallery-mode lasing in native-oxide-confined vertical-cavity surface-emitting lasers. Calculations from classical antenna theory based on the higher-order Bessel functions are compared with experiment and shown to be a useful predictor of the measured radiation fields. The most interesting features of the lasing modes are the multiple and uniformly distributed intensity spots in the near and far fields.     

Transverse-mode selectivity in possible nitride vertical-cavity surface-emitting lasers

Excitation of various transverse modes in possible nitride vertical-cavity surface-emitting lasers (VCSELs) is investigated and compared using the effective frequency optical model. In the comparative analysis of laser mode selectivity, two distinctly different configurations of possible nitride VCSELs are considered: the traditional VCSEL design with both (n-side and p-side) ring contacts as well as the uniform-current-injection (UCI) VCSEL design. Our simulation reveals that, during the continuous-wave device operation at room temperature, a multi-mode operation dominated by higher-order transverse modes is typical for traditional nitride VCSEL configurations whereas a desirable single-mode (based on the fundamental LP₀₁ mode) operation turns out to be characteristic for the wide current range in UCI ones. The above different threshold device behaviours are an immediate consequence of essentially different current-spreading phenomena in both VCSEL designs, resulting in completely different not only gain profiles but also temperature distributions within the laser active regions of both VCSELs. Seemingly similar behaviour has been also reported in arsenide VCSELs but it is expected to be much more severe in the case of nitride ones as a result of much higher both electrical resistivities of p-type nitrides and their temperature derivatives of refractive indices.     

Temperature behaviour of top mirror reflection spectrum in intra-cavity-contacted oxide-confined vertical-cavity surface-emitting lasers

The thermal dependence of mirror reflective properties in oxide-confined vertical-cavity surface-emitting lasers is investigated. The temperature distribution over a cavity versus applied current is then calculated. The refractive indexes of the mirror layers are subsequently redefined using the temperature coefficients, and changes in radial reflectance spectra of the mirror are analysed. Results show a shift of stop-band and Bragg wavelengths of the mirror, as well as a shift of laser operation wavelength at different injection currents and the formation of a temperature lens in the mirror due to a decrease in temperature close to the edge of the oxide windows.     

Double vertical-cavity surface-emitting lasers with transverse mode filtration

Methods for improving radiative characteristics of a double vertical-cavity surface-emitting laser operating in one-and two-frequency regimes have been considered. The influence of the surface relief and conductive properties of the output mirror on the laser mode structure and power has been investigated. In simulation, the effective-frequency method was used to solve the wave equation.     

长波长垂直腔面发射激光器研究

垂直腔面发射激光器（简称VCSEL）近年来受到了国内外科技界和企业界的高度关注，它在光通信领域具有潜在的应用．文章主要介绍了长波长垂直腔面发射激光器的发展历史、基本应用、器件结构、材料和制备工艺，最后分析了研制长波长VCSEL所遇到的问题及相应解决方法，并进行了展望．     

Micromechanical tunable vertical-cavity surface-emitting lasers

We report the study on a short wavelength-tunable vertical-cavity surface-emitting laser utilizing a monolithically integrated bridge tuning microelectromechanical system. A deformable-bridge top mirror suspended above an active region is utilized. Applied bridge-substrate bias produces an electrostatic force which reduces the spacing of air-gap and tunes the resonant wavelength toward a shorter wavelength (blue-shift). Good laser characteristics are obtained: such as continuous tuning ranges over 11 nm near 940 nm for 0--9 V tuning bias, the peak output power near 1 mW and the full-width-half-maximum limited to approximately 3.2--6.8 nm. A detailed simulation of the micromechanical and optical characteristics of these devices is performed, and the ratio of bridge displacement to wavelength shift has been found to be 3:1.     

Optical feedback induces polarization mode hopping in vertical-cavity surface-emitting lasers

Vertical-cavity surface-emitting lasers subjected to weak polarization-insensitive optical feedback are studied experimentally and theoretically. We find that the feedback induces random anticorrelated hopping between the two orthogonal linearly polarized modes. This polarization mode hopping is accompanied by rapid anticorrelated oscillations in the linearly polarized intensities at the external-cavity frequency. The study of a simple stochastic delay differential equation suggests that these oscillations generated by the delay are typical of any hopping phenomenon between states.     

垂直腔面发射激光器的电路模拟

通过分析垂直腔面发射激光器的速率方程,并结合电子电路的特点,建立了等效电路模型。采用数值计算和电路模拟两种方法给出了垂直腔面发射激光器的频率响应特性。通过分析,证明了电路模型的正确性。通过电路模拟得出了脉冲调制的响应特性,验证了激光器固有的电光延迟和张驰振荡现象。     

Using polarization properties to enhance performance of chaos synchronization communication between vertical-cavity surface-emitting lasers

Enhanced chaos synchronization communication between vertical-cavity surface-emitting lasers (VCSELs) is investigated numerically, by adopting a polarization communication protocol where one polarization mode is used as the chaotic carrier and the orthogonal polarization mode is used as the disturbed signal. The chaos synchronization quality for the receiver laser (RL) and attacker laser (AL) are analyzed in terms of the cross-correlation coefficient. There are two distinct regions of good synchronization quality in the injection parameters space. In the first region, good synchronization quality can be ensured for both the RL and AL. In the second region, only the RL can realize chaos synchronization. We further discuss the security enhancement by comparing the communication performance between RL and AL for injection parameters within the second region. The results show that successful and robust decoding is only achievable for the RL.     

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     

Bifurcation to polarization self-modulation in vertical-cavity surface-emitting lasers

Experiments have yielded polarization self-modulation in vertical-cavity surface-emitting lasers (VCSELs) subject to a pi/2 polarization-rotating optical feedback. The phenomenon has been simulated numerically, but its bifurcation has never been explained. We show that polarization self-modulation results from a Hopf bifurcation mechanism that can be analyzed in terms of the laser feedback parameters. Our analysis predicts other bifurcations for low values of the feedback rate, which explain why more-complex time-dependent outputs have been observed as alternatives to polarization self-modulation.     

Investigation polarization characteristics of vertical-cavity surface-emitting lasers

We have improved transmission line laser model to study the polarization characteristics by incorporating into spin-flip model (SFM). Theoretical studies on the influence of the Bragg reflectivity on the polarization switching of vertical-cavity surface-emitting laser (VCSEL) have been discussed in this paper. We have demonstrated that reflectivity of Bragg reflectors can be optimized to provide suitable hysteresis loops width which indicates the tolerance of the input power.     

Wave chaos in real-world vertical-cavity surface-emitting lasers

We report the onset of wave chaos in a real-world vertical-cavity surface-emitting laser. In a joint experimental and modeling approach we demonstrate that a small deformation in one layer of the complicated laser structure changes the emission properties qualitatively. Based on the analysis of the spatial emission profiles and spectral eigenvalue spacing distributions, we attribute these changes to the transition from regular behavior to wave chaos, and justify the full analogy to two-dimensional billiards by model calculations. Hence, these lasers represent fascinating devices for wave chaos studies.     

注入电流对垂直腔面发射激光器横模特性的影响

对980nm氧化限制型垂直腔面发射激光器横模进行测试和研究,理论上从时间、空间变量的速率方程出发,利用空间积分法分析了典型电注入参数对弱折射率导引垂直腔面发射激光器(VCSELs)横模行为的影响,通过实验测试,得到VCSELs的横模光场分布情况,并与理论分析进行对比,得出相应的实验结果,在氧化孔径不变的情况下,随着注入电流的增加,载流子分布从有源区中心向边缘移动,模式从低阶基模向高阶模转变,并发生了较强的模式竞争以及载流子空间烧孔效应,最终导致基模强度的降低.另一方面,通过比较不同注入孔径下高阶模的发生时 关键词： 横模 垂直腔面发射激光器 空间烧孔现象 模式竞争     

Waveguiding effects in self-pulsing vertical-cavity surface-emitting lasers

Self-pulsing in semiconductor lasers containing a saturable absorber is well documented. We propose an alternative mechanism leading to self-pulsing in vertical-cavity surface-emitting lasers. We specifically consider waveguiding effects and determine the conditions for self-pulsing. Our theoretical and numerical results agree with experimental observations reported by Willemsen et al. [Appl. Phys. Lett. 77, 3514 (2000)].     

Two-mode injection locking in vertical-cavity surface-emitting lasers

We report on the dynamics that accompany polarization switching induced by orthogonal optical injection in a vertical-cavity surface-emitting laser (VCSEL). As the injection strength increases, the VCSEL bifurcates to injection-locked steady states and time-periodic and possibly chaotic dynamics. Of particular interest is a two-mode injection-locking solution, i.e., locking of the two VCSEL polarization modes. A detailed stability analysis unveils new bistability mechanisms in optical injection problems.     

On the thermal resistance of vertical-cavity surface-emitting lasers

Thermal properties of vertical-cavity surface-emitting lasers (VCSELs) are studied using their comprehensive, three-dimensional, self-consistent, thermal-electrical simulation. The thermal resistance versus operation current relation is found to be completely different for two basic VCSEL configurations, i.e. for proton-implanted top-surface-emitting lasers (top-emitting VCSELs) and etched-well lasers (bottom-emitting VCSELs). The above fact is explained using a concept of the average centre of heat generation within a laser volume and its shift with an increase in an operation current. This revised version was published online in November 2006 with corrections to the Cover Date.     

Observation of low-frequency fluctuations in vertical-cavity surface-emitting lasers

Low-frequency fluctuations, which are typical irregular oscillations in edge-emitting semiconductor lasers, are experimentally observed for the y-polarization mode (y is the direction along the optical axis of a laser material) in a vertical-cavity surface-emitting laser with optical feedback.