用直接模拟法分析量子阱半导体激光器瞬态响应

根据光增益与载流子密度的对数关系 ,通过适应于多量子阱激光器的速率方程的直接模拟分析 ,得到了注入电流、阱数和腔长对多量子阱激光器的激射阈值、开关延迟时间、弛豫振荡频率和光输出等参量之间的依赖关系 .运用相图确立了在瞬态过程中 ,载流子数密度和光子数密度之间的转化过程 .从而为改善量子阱激光器的高频调制特性以及优化设计器件结构参数提供了理论依据     

用直接模拟法分析量子阱半导体激光器瞬态响应

根据光增益与载流子密度的对数关系,通过适应于多量子阱激光器的速率方程的直接模拟分析,得到了注入电流、阱数和腔长对多量子阱激光器的激射阈值、开关延迟时间、弛豫振荡频率和光输出等参量之间的依赖关系.运用相图确立了在瞬态过程中,载流子数密度和光子数密度之间的转化过程.从而为改善量子阱激光器的高频调制特性以及优化设计器件结构参数提供了理论依据.     

λ／4相移分布反馈半导体激光器在高输出功率时的特性分析

从光场限制因子周期性主烨这一概念出发，指出在纯折射率耦合分布反馈激光器中存在着增益耦合作用，这种作用在阈值附近较小，但在输出功率增加时迅速大，并因此使λ／４相移分布反馈激光器的单模特性主。量子效应对这种增益耦合作用影响不大。在λ／４相移量子阱分布反馈激光器中，量子效应对空间烧孔效应有很强的抑制作用，因此在其高力功率值出特性出中，增益耦合的影响将变得比较明显。     

Feasibility study of low-power multiquantum-well vertical transmission optical amplifiers for optical interconnection

Performance of 0.98-μm InGaAs strained multiquantum-well Fabry-Perot vertical transmission optical amplifiers (MQW FP VTOAs) for optical inter-board connection is analyzed theoretically, and compared with those of GaAs MQW, GaAs bulk, and InGaAsP bulk VTOAs. A low-power operation of about 2 mA and a cascadability of several hundred boards are predicted for an InGaAs strained MQW FP VTOA.     

Analysis of chirp characteristics of DFB lasers and integrated laser-modulators

A new method of analyzing the chirp characteristics of directly modulated lasers and integrated laser-modulators is presented in this paper. Phase-circuit has been introduced into the circuit model of distributed feedback (DFB) lasers in the analysis. Therefore, the chirp characteristics of the device can be obtained by simulating the modified circuit model. The simulation results agree well with the published data. Furthermore, this modified model is combined with the circuit model of electroabsorption (EA) modulators to simulate the chirp characteristics of the monolithic integration of a DFB laser and an EA modulator. The simulation is focused on the dependence of the frequency chirp of the integrated device on the isolation resistance between laser and modulator. Much lower chirp can be seen in the integrated lightwave source compared to the directly modulated laser.     

A simple model for optimization design of high performance In1−x−y Ga y Al x As strained MQW DFB lasers

It is well known that complex rate equations and the couple wave equation have to be solved by the method of iteration in the simulation of multi-quantum well (MQW) distributed feedback Bragg (DFB) lasers, and a long CPU time is needed. In this paper, from the oscillation condition of lasers, we propose a simple and fast model for optimization of In_1–x–y Ga _y Al _x As strained MQW DFB lasers. The well number and the cavity length of 1.55 m wavelength In_1–x–y Ga _y Al _x As MQW DFB lasers are optimized using the model. As a result, the simple model gives almost the same results as the complex one, but 90% CPU time can be saved. In addition, a low threshold, high maximum operating temperature of 550–560 K, and high relaxation oscillation frequency of over 30 GHz MQW DFB laser is presented.     

半导体微碟激光器设计原理与工艺制作

用经典量子电动力学理论初步研究了半导体碟型微腔激光器的设计原理，采用光刻、反应离子刻蚀和选择化学腐蚀等现代微加工技术制备出抽运阈值功率很低用品质因数很高的低温光抽运InGaAs/InGaAsP多量子阱微碟激光器。这种激光器制作工艺简单，对有效光子状态密度调制较大，是比较理想的半导体微腔激光器。     

三次啁啾光纤光栅的设计及其应用

针对直接调制的半导体激光器产生的非线性啁啾,设计了一种新型的三次啁啾光纤光栅,与线性啁啾光纤光栅相比,它能更为彻底地补偿此类非线性啁啾.     

应变多量子阱激光器的阱数与腔长

本文从理论上分析计算并给出了应变多量子阱激光器阱数与腔长的优化设计结果.考虑到多生子阱阱区的注入不均匀性,提出了一种新的分析和计算方法.以1.55μmInGaAs(P)1.5%压缩应变多量子阱激光器为例,最佳的阱数为4个,最佳腔长为500μm左右.     

1.3-μm GaInAsP/InP Multi-Quantum-Well Surface-Emitting Lasers

A multi-quantum-well (MQW) active layer has been introduced to 1.3-μm GaInAsP/InP surface-emitting (SE) lasers. Room temperature pulsed operation of a 1.3-μm MQW SE laser was obtained for the first time and its threshold current was 15 mA. CW (continuous wave) operation up to 7°C (threshold current 1_th=7.6 mA at 7°C) was achieved.     

Improving the intensity and efficiency of compressed echo in rare-earth-ion-doped crystal

We investigate the intensity and efficiency of a compressed echo, which is important in arbitrary waveform generation(AWG). A new model of compressed echo is proposed based on the optical Bloch equations, which exposes much more detailed parameters than the conventional model, such as the time delay of the chirp lasers, the nature of the rare-earth-iondoped crystal, etc. According to the novel model of compressed echo, we find that reducing the time delay of the chirp lasers and scanning the lasers around the center frequency of the inhomogeneously broadened spectrum, while utilizing a crystal with larger coherence time and excitation lifetime can improve the compressed echo's intensity and efficiency. The theoretical analysis is validated by numerical simulations.     

Directly modulated lasers in negative dispersion fiber links

In the paper the impact of frequency chirp of directly modulated lasers is considered in context of high-speed data transmission over negative dispersion fiber. Chirp/dispersion induced signal distortions are described, and detailed investigations of their influence on 10 Gb/s transmission system performance are presented. The desired laser chirp characteristics and optimal driving conditions are determined. It is also demonstrated that directly modulated laser with low chirp offers similar or even better dispersion tolerance than unchirped (externally modulated) source. Experimental verification of described investigations is presented at the end.     

Characterization of semiconductor laser frequency chirp based on signal distortion in dispersive optical fiber

In the paper, the simple method of laser chirp parameters estimation is presented. It is based on measuring time-domain distortions of chirped signal transmitted through dispersive fiber and finding laser chirp parameters by matching measured distortions to calculated ones. Experiments undertaken with 1.55 μm telecommunication grade distributed feedback (DFB) lasers and standard single-mode fiber are described, together with some practical remarks on measurement setup and main conclusions.     

Exciton polariton in an organic–inorganic multiple-quantum-well crystal (C4H9NH3)2PbBr4

Exciton polariton in an organic–inorganic multiple-quantum-well (MQW) single crystal (C₄H₉NH₃)₂PbBr₄ at low temperature has been investigated by photoluminescence excitation (PLE), reflection, and time-resolved photoluminescence measurements. Since (C₄H₉NH₃)₂PbBr₄ has ideal two-dimensional excitons with an extremely large oscillator strength and forms self-organized MQW with a very short well-period (d～10 Å), polaritonic coupling among excitons is strong and extends over a large number of wells. Therefore, observed MQW polariton features were the same as those of bulk polaritons. We have also investigated relaxation dynamics of the MQW polariton in the same framework as discussions on bulk polaritons.     

量子阱半导体激光器阈值的理论分析

分析了单量子阱(SQW)、多量子阱(MQW)和分别限制异质结构量子阱(SCH-SQW)半导体激光器的阈值.求出了表示光增益随注入载流子密度变化的方程.利用这个结果,得到了上述三种量子阱半导体激光器的阈值电流密度的表达式.     

Dynamic analysis of directly modulated Fabry–Perot laser diodes using time-domain modeling with random noise fluctuations

Based on time-domain laser modeling, we have systematically evaluated multi-mode excitation and mode competition in directly modulated Fabry–Perot laser diodes biased with different current levels. In our simulation, random noise fluctuations depending on the bias current are included since they play an important role in determining the number of lasing modes. Multi-mode excitation and mode competition occurred at the biased current below the threshold current can be explained with the aid of frequency chirp at turn-on and gain difference in between '0' and '1' bits. The positive frequency chirp (25 GHz for lasers biased below the threshold current and 15 GHz for lasers biased above the threshold current) affects to enhance the probability of multi-mode excitation in low-frequency region during turn-on delay.     

碟型量子阱微腔激光器的低阈值激射

利用反应离子刻蚀(RIE)和湿法腐蚀方法在InGaAs/InGaAsP多量子阱材料上研制出直径为8μm、4.5μm和2μm的碟型半导体微腔激光器。其中2μm直径的微碟在液氮温度下其光泵浦激射阈值仅为3μW左右。对高光功率密度下泵浦时出现的多模激射、跳模和激射光谱强度饱和现象进行了研究。并对微碟激光器的激射光谱线宽特性进行了初步的分析。     

Modelling of RF CO2 Laser Pulses

The usual laser rate equations have been applied to fit energy and shape of pulsed emissions of RF CO₂ single mode lasers starting from the discharge and cavity parameters. The model well reproduce the laser behaviour, if to fit the turn-off normally observed in these lasers we introduce a phase laser gain correction related to the frequency chirp.     

Analysis of coupling effect on valence band structures of strained multiple quantum wells

The multi-well energy representation technique is presented for the analysis of the valence band structures of multiple quantum well (MQW) lasers. In terms of this technique and its relative formulae, calculations are performed for InGaAs/InGaAsP strained MQW structures. It is found that the coupling exists between the wells, and causes the energy split. So, on the basis of the computed results, the coupling between the wells is analysed, and the split of both the quantized energy levels at the Γ point and the quantized energy bands at the non-Γ points is described. It is also found that the structural parameters of the MQW system strongly influence the coupling property and the energy split, and hence these effects are also discussed in relation to the periodic length, the well width, the distance between the wells, and the ratio of the well width to the periodic length. This revised version was published online in June 2006 with corrections to the Cover Date.     

Pulse formation in synchronously pumped infrared dye lasers

Pulse formation in synchronously pumped dye lasers with fast relaxing dyes is treated by computer simulation. The influence of spontaneous emission and chirp, as well as cavity mismatch, on the pulse characteristics and stability of generation are discussed.