可变偏振光注入垂直腔面发射激光器的频率诱导偏振双稳

为了探索垂直腔面发射激光器偏振敏感的双稳演 化规律,进一步拓展其在光信息处理领域方面的应 用,本文采用自旋反转模型,数值研究了可变偏振光注入下1 550 nm垂直腔面发射激光器频率诱导偏振双 稳的特性。研究结果表明:在可变偏振角度光注入下,通过沿不同路径扫描频率失谐,垂直 腔面发射激光 器的两个正交偏振分量可在负失谐和正失谐区域产生频率诱导的偏振双稳。对于一确定的注 入强度,注入 光偏振角度的增加可导致负失谐区域的偏振双稳宽度逐渐扩展,而正失谐区域双稳宽度无明 显的变化;给 定适当的注入光角度,较大的注入强度更易于在负失谐区域展宽偏振双稳宽度。此外,在注 入光偏振角度 和注入强度均一定时,不同偏置电流情况下激光器偏振分量的频率诱导双稳宽度存在较大差 异,系统可以 通过合理地调节注入光偏振角以及偏置电流等参量实现对频率诱导偏振双稳的灵活控制。     

Improvement of slow light performance for vertical-cavity surface-emitting laser using coupled cavity structure

We propose a vertical cavity semiconductor emitting laser(VCSEL)using a coupled-cavity(CC)design to broaden the bandwidths of gain and delay spectra.The structure is formed by constructing a passive cavity coupled with the active cavity.By rendering the strength of the two resonant cavities,the increased gain bandwidth by 340%and the increased delay bandwidth by 800%are achieved as compared with the signal-cavity(SC)VCSEL.The wideband spectra present more square-like passband which is expected for slow light system.By using it,a 20 Gbit/s super Gaussian signal is delayed by about 13 ps with high quality.     

径向偏振激光反射腔镜的研究

近年来,径向偏振光因为其特殊的偏振特性而受到广泛的关注。本文以耦合波理论中的T矩阵算法为基础,用Matlab语言编制了能够计算多层复合结构光栅的程序算法,并用此程序算法对多层光栅模型进行了理论模拟。综合模拟结果,设计出光栅周期为1000 nm、槽深为70 nm、占空比为0.5和Ti2O5/SiO2交替镀膜35层数的径向偏振反射腔镜,并通过微纳加工工艺制备出光栅反射腔镜样品,将其应用于自行搭建的Nd∶YAG激光器系统中,获得了输出功率12.6 W,偏振纯度为96%的径向偏振光。     

Temperature-dependent polarization characteristics of composite-resonator vertical-cavity lasers

We investigate the output characteristics from 10/spl deg/C to 160/spl deg/C of a monolithic dual-resonator vertical-cavity laser composed of three distributed Bragg reflector mirrors that separate two nominally identical optical cavities. The light output from the top ion-implanted cavity under forward bias is partitioned into two orthogonal polarizations of the fundamental transverse mode. A reverse bias of sufficient magnitude applied to the bottom oxide cavity causes the abrupt suppression of the dominant polarization and simultaneous emergence of the orthogonal polarization, consistent with wavelength dependent electroabsorptive loss in the reverse biased quantum wells of the oxide-confined cavity. We calculate the internal loss as a function of reverse bias and temperature, and characterize the polarization properties of the device based on the temperature dependence of the laser output. The polarization switching is consistent with increasing absorption with increasing temperature and decreasing absorption at longer wavelengths.     

Gain-switching in a vertical-cavity laser with high-contrastmirrors

Gain-switched operation of an optically pumped vertical-cavity surface-emitting laser with high-contrast Al_xO_y/GaAs distributed Bragg reflectors is characterised. A pulse width of less than 8 ps is obtained. The far-field radiation patterns at different pump levels are found to depend on the temporal response     

内腔He-Ne激光器的位相各向异性与偏振特性

较全面地报道了与位相各向异性有关的内腔He-Ne激光器振荡模偏振特性实验资料,并借助于Lamb理论对实验现象作了理论解释。     

Dynamic properties of vertical-cavity surface-emitting lasers with improved polarization stability

We describe dynamic properties of rectangular etched post vertical-cavity surface-emitting lasers designed for increased polarization stability. These lasers show polarization extinction ratios higher than 20 dB in CW and under high-speed large signal modulation. The high degree of polarization stability allows for error-free transmission in polarization selective free space optical links.     

缓慢腔倒空激光器光腔偏振分析

以实验为基础,从激光器光腔的偏振态出发,应用琼斯矩阵方法对缓慢腔倒空激光器输出矩形脉冲的过程进行了分析,分析的结果与实验结果相符。     

Ultralow-threshold cryogenic vertical-cavity surface-emitting laser

Data are presented characterizing a low-threshold vertical-cavity surface-emitting laser designed for cryogenic operation. A threshold current of 12 μA and current density of 25 A/cm² are obtained at 77 K with the low-loss cavity design. From 77 K to 160 K, the threshold increases linearly with temperature, but only approximately tracks the detuning of the cavity resonance from the minimum energy transition of the quantum well. At 77 K, we estimate that the 25-A/cm² threshold current density is about twice that required for transparency     

High-speed vertical-cavity surface emitting laser

Planar, gain-guided vertical-cavity surface-emitting lasers (VCSELs) with a modulation bandwidth of 14 GHz are described. This bandwidth is reached at a drive current of only 8 mA. The intrinsic bandwidth of these devices is estimated to be greater than 50 GHz. Nonlinear light-current characteristics of these lasers may lead to a high level of nonlinear harmonic distortion of the high-frequency output. It is shown that the relative intensity of the second-harmonic response decreases rapidly at higher drive currents, in agreement with a phenomenological model based on the DC characteristics of the laser     

Three-terminal dual-stage vertical-cavity surface-emitting laser

A three-terminal dual-stage VCSEL, operating continuous-wave at room temperature has been fabricated. Independent biasing of the two active stages leads to an extended singlemode regime compared to conventional VCSELs. The parallel configuration reveals singlemode operation with a differential series resistance <35 Ω     

Elliptical polarization emission from GaAlAs laser diodes in anexternal cavity configuration

We report the experimental operation of an external-cavity laser capable of oscillating in TE, TM, and elliptical-polarization states. An intracavity polarizer is used to force the laser to emit polarized radiation with TE and TM components whose wavelength can be changed by rotating the polarizer, a simple model based on the Jones matrix and steady-stale rate equations is used to explain experimental data. Theoretical results for near threshold operation accurately predict the TE and TM power as a function of polarizer angle as well as the polarization dependence of wavelength     

Analysis of vertical-cavity surface-emitting laser multimodebehavior

This paper investigates problems associated with multimode oscillation in vertical-cavity surface-emitting lasers (VCSELs). The multimode rate equations for transverse mode were formulated. These equations take into account carrier diffusion and gain nonuniformity in the lateral direction. It was shown that multimode transverse mode excitation is due to carrier spatial hole burning, but many factors affect the number of lasing modes. The role of gain nonuniformity distribution, carrier diffusion, and modal loss compared with mirror loss in a cavity were demonstrated by numerical solution of the multimode rate equations     

Effects of built-in polarization on InGaN-GaN vertical-cavity surface-emitting lasers

We investigate the effect of built-in spontaneous and piezoelectric polarization on the internal device physics of current-injected GaN-based vertical-cavity surface-emitting lasers (VCSELs) with strained InGaN quantum wells. Advanced device simulation is applied to a previously manufactured device design featuring dielectric mirrors and an indium-tin-oxide current injection layer. Contrary to common perception, we show: 1) that only a small fraction of the built-in quantum-well polarization is screened at typical injection current densities and 2) that the polarization of the AlGaN electron stopper layer has a strong effect on the VCSEL threshold current which can be partly compensated for by higher p-doping.     

High-power vertical-cavity surface-emitting laser with an extra Au layer

We report the performance of a high-power vertical-cavity surface-emitting laser (VCSEL) with an extra Au layer. By using the extra Au layer, the far-field divergence angle from a 600-/spl mu/m diameter VCSEL device is suppressed from 30/spl deg/ to 15/spl deg/, and no strong sidelobe is observed in far-field pattern. There is a slight drop in optical output power due to the introduction of the extra Au layer. By improving the device packaging method, the VCSEL device produces the maximum continuous-wave optical output power of 1.95 W with lasing wavelength of 981.5 nm. The aging test is carried out under constant current mode at 60/spl deg/C, and the preliminary result shows that the total degradation of output power is less than 10% after 800 h.     

A high-efficiency vertical-cavity surface-emitting switching laserfabricated with post-growth cavity mode positioning

The first room-temperature continuous-wave (CW) operation of the double heterostructure optoelectronic switching laser implemented as a vertical-cavity laser is described. A deposited dielectric top reflector of SiO₂/TiO₂ allowed the use of a cavity etch back technique after the sample was grown, to position the cavity mode at the desired wavelength. Room temperature CW threshold currents as low as 4.8 mA for a 14-μm-diameter device were obtained with slope efficiencies of 0.45 mW/mA. The maximum CW output power was 2.5 mW and the resistivity was 4×10^-4 Ωcm²     

Frequency response of polarization switching in vertical-cavity surface-emitting lasers

We present an experimental study of the current-driven polarization modulation properties of VCSELs. In some VCSELs, abrupt polarization switching (PS) between two polarization modes is observed at a particular value of the pump current. We investigate the dynamics and the associated dominating time scales of PS as these features are strongly linked with the underlying physical mechanism causing the PS. To this end, we measure both for gain- and index-guided VCSELs the critical modulation amplitude necessary to steadily force PS back and forth across the PS point as a function of the modulation frequency. This yields the current-driven polarization modulation frequency response, which we compare with the thermal frequency response of the studied devices. The dynamic behavior turns out to be strikingly different for the different VCSEL types. Thermal effects only play a minor role in the PS in our index-guided VCSELs, while they really seem to lie at the origin of PS in the gain-guided VCSELs. By implementing this in a rate-equation based theoretical model, we are able to explain the peculiarities of the measured response curves and to reproduce the experimental findings.     

Pixels consisting of a single vertical-cavity laser thyristor and adouble vertical-cavity phototransistor

Bidirectionally cascadable optical pixels that consist of a single-vertical-cavity surface-emitting laser (VCSEL) thyristor and a double-vertical-cavity phototransistor are proposed. Despite almost identical layer structures, each device characteristic can be independently optimized by introducing a λ/2-spacer layer into the phototransistor section. A lasing threshold of 0.8 mA and a slope efficiency of 0.25 W/A are obtained for the laser thyristor, and a flat-topped photocurrent spectrum over 30 A and a photocurrent gain of 70 A/W are obtained for the phototransistor at the resonant wavelength. This work demonstrates the possibility of monolithic integration using thermal desorption and a regrowth technique and the suitability of these devices for massively parallel optical interconnections     

底部出光纳米孔径面发射激光器的研究

在普通大功率垂直腔面发射激光器(VCSEL)基础上,制备出了底部出光纳米孔径VCSEL。利用聚焦离子束刻蚀技术完成纳米孔径的制作。当小孔直径为480nm×480nm时,测量得到器件的远场输出光功率为0.07mW。并分析了温度的变化对该器件远场输出光功率的影响。     

A proposal of broad-bandwidth vertical-cavity laser amplifier

We propose a generic vertical-cavity amplifier (VCA) using a coupled-cavity design to broaden the bandwidth. Calculations are made for cavities with GaAs-AlAs and GaAs-Al_xO₂ distributed Bragg reflectors (DBR). We found that at reasonable pumping levels the VCA increased the bandwidth by 85% (GaAs-AlAs) to 500% (GaAs-Al_xO₂) as compared to a simple two-mirror structure similar to vertical-cavity surface-emitting lasers. In particular, the GaAs-AlAs VCA shows a bandwidth of 2 nm at 6-dB signal gain, while the GaAs-Al_xO₂ VCA demonstrates a 5-nm bandwidth at 6-dB signal gain with no ripple at required single-pass power gain of ~2-2.5%. Furthermore, as large as 30-nm bandwidth in a lossless bandpass filter can be obtained