透明导电薄膜ITO对浅面浮雕VCSEL的影响

对于顶面出光的浅面浮雕VCSEL结构,有源区的电流密度分布的不均性制约着单模稳定性的提高。为此,提出了一种新型结构:氧化铟锡透明导电薄膜(ITO)浅面浮雕VCSEL。该结构不仅能够增大高阶模式的阈值增益,还能够提高基模的增益,实现基模对高阶模式的稳定抑制。研究了ITO的厚度对阈值增益的影响及ITO对VCSEL有源区电流密度分布的影响。研究结果表明:在ITO的厚度为半波长的整数倍时,基模对高阶模式的限制作用最强;ITO通过改善VCSEL有源区的电流密度分布,达到了增大基模的增益和降低高阶模式增益的目的,同时还降低了串联电阻和外电压。     

电光调制对外部光反馈垂直腔表面发射激光器输出矢量混沌偏振的操控

基于周期性极化铌酸锂晶体的线性电光效应耦合波理论,数值研究了电光调制对外部光反馈垂直腔表面发射激光器(VCSEL)输出矢量混沌偏振模的操控.研究结果表明,VCSEL输出的偏振度随着电光晶体的长度或施加于电光晶体的外电场强度成周期性转换,控制一定的施加外电场强度和晶体的长度,激光器的不同参数下引起初始混沌偏振态都可以转换为其他任意混沌偏振态.特别是合理选择一定的施加外电场强度或晶体长度,VCSEL输出的任意混沌偏振模可以转换为完全一致的两线性混沌偏振模(x和ŷ偏振),即两线性混沌偏振模的能量能够达到稳定和完全均衡.     

Optical modelling of photonic crystals and VCSELs using eigenmode expansion and perfectly matched layers

We present a modelling approach for photonic crystal structures and vertical-cavity surface-emitting lasers (VCSELs). This method is based on vectorial eigenmode expansion combined with perfectly matched layer (PML) boundary conditions. Compared to other methods, a relatively small computational effort is required, while at the same time accurate results are obtained, even in the presence of strong scattering and diffraction losses.     

Electro-optic mapping systems of electric-field using CW laser diodes

Two novel systems are proposed to perform the electro-optic (EO) mapping of the electric-field strength close to electrode structure using CW laser diodes. By these systems, mappings of both static (DC) and high-frequency electric-field can be obtained. For the static field, the field is chopped to increase the sensitivity performance. For the high-frequency field, an intensity modulation laser, instead of a pulse laser, is used to perform the mapping measurement in frequency domain, instead of in time domain. This approach greatly simplifies the system. An experiment set-up using a vertical cavity surface emitted laser diode (VCSEL) of a wavelength 850 nm and its mapping results for a coplanar waveguide (CPW) with the signal frequency around 1 GHz are reported.     

注入电流引起质子轰击VCSEL中的模式竞争

为了分析质子轰击垂直腔面发射激光器(VCSEL)中注入电流引起的激光模式竞争过程,在三维空间中对VCSEL激射后光电热进行了研究。给出仿真光电热的方程之后,在室温连续工作条件下,对电流孔半径r为4μm、阈值电流Ith为4.5 m A的VCSEL进行自洽求解。当注入电流Iin分别为5.0,5.5,6.0 m A时,得到了对应的外加电压和输出光功率,并绘制了VCSEL的电势、注入电流、载流子、光场和热场的空间分布,给出了连续工作下输出光功率随注入电流变化的曲线。仿真结果表明:随着注入VCSEL中的电流增加,电流密度增大,激光的横向基模和横向一阶模式同时增强。横向一阶模式增加的强度及扩展的范围大于横向基模,激光输出能量逐渐向横向一阶模式过渡,横向模式竞争的同时产生载流子空间烧孔,因此在电流孔半径r≥4μm的VCSEL中,连续工作激光模式不稳定。     

Separate Polarization Modes Synchronization and Synchronization Switches between Vertical-Cavity Surface-Emitting Lasers

For vertical-cavity surface-emitting lasers (VCSELs) with polarization-rotated feedback, there exist several synchronization types such as synchronizations between total powers and synchronizations between separate polarization modes. Based on the two-mode rate equations, we study and compare numerically the performances of different synchronization types. Our results show that three synchronization types exhibit good performances when their synchronization conditions are satisfied. They are the complete synchronization between total powers, complete synchronization between x-polarized modes, and generalized synchronization between x-polarized and y-polarized modes. The former two types are sensitive to the injection rate and spontaneous emission, while the third type is contrary. Synchronization type with the best performance may switch from one to another, with changing of injection rate and spontaneous emission factor.     

Spatiotemporal and Thermal Analysis of VCSEL for Short-range Gigabit Optical Links

High-speed Optoelectronic Modules using Vertical Cavity Surface Emitting Lasers (VCSEL) coupled to Multi Mode Fibers (MMF) are a performing and low-cost solution for 10 Gigabit Ethernet (10 GbE) in short-distance optical links. A complete model of the spatiotemporal behavior of multimode VCSELs, through static and dynamic response, noise, thermal effects, and its coupling to MMF has been investigated. Relative Intensity Noise shows modal dependence and can be affected by spatial filtering due to coupling and fiber propagation. Simulations permit to evaluate critical parameters, such as modulation formats, launching conditions, and operating temperature for global bandwidth and eye diagram optimization up to 10 Gb/s. Simulation results are compared to measurements on prototype optoelectronic modules.     

High-performance AlGaAs-based VCSELs emitting in the 760 nm wavelength range

Vertical-cavity surface-emitting lasers (VCSELs) showing continuous-wave operation with emission wavelengths ranging between 717 and 790 nm have been fabricated. The samples are grown by solid source molecular beam epitaxy on GaAs substrates and are entirely based on the AlGaAs material system. A maximum single-mode output power of 2.0 mW is obtained at 754 nm wavelength by using the inverted surface relief technique.     

高功率垂直腔面发射激光器的湿法腐蚀工艺

为提高高功率垂直腔面发射激光器(VCSEL)光电性能,对氧化限制型高功率VCSEL湿法腐蚀工艺进行了实验研究。实验中采用H₃PO₄系溶液替代以往制备此类器件常用的H₂SO₄系溶液作为高功率VCSEL外延片的腐蚀液,利用扫描电镜(SEM)研究了腐蚀后外延片氧化窗口的腐蚀形貌变化与腐蚀液浓度的关系,消除了以往采用H₂SO₄系溶液腐蚀时,高功率VCSEL氧化层侧壁出现的"燕尾"结构;通过改变湿法腐蚀工艺的外部温度条件和腐蚀液的浓度配比,实验研究了高功率VCSEL湿法腐蚀速率规律,最后得出了制备高功率VCSEL时湿法腐蚀工艺的最佳外部温度条件与腐蚀液的最佳浓度配比。     

Oxide aperture scaling effect on high-speed (>16 GHz) vertical-cavity surface-emitting lasers performance

High-speed, oxide-confined, polyimide-planarized 850 nm vertical-cavity surface-emitting lasers (VCSELs) with oxide aperture diameters of 9, 10, 12, 15, 20, and 30 μm have been fabricated and characterized. For a 9 μm oxide aperture diameter, the lasers exhibit a resonance frequency, a 3-dB modulation frequency, and a modulation current efficiency factor (MCEF) up to 12.4, 16.5 GHz, and 10.9 GHz/mA^1/2, respectively, at only 7.9 kA/cm². Threshold voltage and current were 1.45 V and 0.7 mA, respectively. It is demonstrated that increasing the resonance frequency with bias does not guarantee a higher modulation bandwidth. The influence of oxide aperture scaling effect on VCSEL performance is presented.