量子阱激光器的阈值电流和外量子效率

地于半导体分别限制单量子阱激光器，为了降低阈值电流，提高外量子效率，分析和讨论了影响阈值电流和外量子效率的各种因素，并做了一定的数值计算，给出了量佳结构参数。     

低偏置电流下大功率半导体激光器低频电噪声特性

测量了大功率InGaAsP/GaAs量子阱半导体激光器在五十分之一阈值电流下的电压低频噪声功率谱密度.实验结果显示,激光器的低频电噪声呈现1/f噪声,在不同的偏置电流范围内,1/f噪声幅度随电流的变化关系不同,整体上随偏置电流的增大而减小,实验中并未发现g-r噪声.结合低偏置电流时激光器动态电阻的大小,给出了1/f噪声的模型,分析了在低偏置电流下的1/f噪声主要来自有源区和漏电电阻,其幅度的大小及其随偏置电流的变化趋势与激光器的可靠性有密切的关系.     

Temperature dependence of threshold current of GaAs quantum well lasers

The radiative recombination rate in a quantum well structure is calculated using a constant density of states and the k-selection rule. This calculation shows that the threshold current of a GaAs quantum well laser has low temperature sensitivity (T0 ? 330 K for T > 300 K).     

Threshold current of 670-nm AlGaInP strained quantum well lasers

By means of gain-current calculations we have examined the factors which determine the threshold current of compressively strained Ga_x In_1-xP/AlGaInP quantum well lasers for the various well width/composition (x) combinations which give a transition wavelength of 670 nm. In addition to valence band modifications we find that the increasing depth and decreasing width of the well are important in decreasing the current as the strain increases. We reveal the important role of well width fluctuations in devices with high compressive strain     

量子阱半导体激光器调制特性和噪声的电路模拟

给出一种量子阱半导体激光器（QWLD）小信号等效电路模型,可以作为含有QWLD系统计算机辅助设计的模型。模型包括QWLD的高速调制特性和噪声,对QWLD的调制特性和噪声进行了模拟,并对比了已发表的模拟和实验结果。     

High power and low optical feedback noise AlGaAs single quantum well lasers

GaAs-AlGaAs single quantum well self-aligned lasers have been developed for optical disc recording. The lasers emitting at 834 nm have realised low optical feedback noise as well as high output power. The lasers have shown less than -130 dB/Hz relative intensity noise at 3 mW, and stable 50 mW operation (over 500 hours at 50 degrees C ambient).<>     

Auger recombination effect on threshold current of InGaAsP quantum well lasers

The Auger recombination effect on the threshold current of the InGaAsP quantum well (QW) laser is studied theoretically. All possible transitions between the quantized subbands of two-dimensional carriers are taken into account in evaluating the radiative process with thek-selection rule and the Auger process. The calculated threshold current agrees well with the reported experimental results for 1.07 μm InGaAsP QW lasers. The Auger component of the threshold current and its temperature dependence strongly depend on the QW structure, resulting in the necessity for an elaborate QW structure design, although both cannot be optimized at the same time. A design procedure is elucidated for a structure which gives the lowest threshold current density for the 1.07, 1.3, and 1.55 μm InGaAsP QW lasers.     

Analysis of threshold current density and optical gain in InGaAsP quantum well lasers

Single-mode and multimode quantum well (QW) laser diodes with emission wavelengths λ=1.0 and 1.58 μm, based on MOCVD-grown separate-confinement heterostructures, have been studied. An analysis of the threshold current density and optical gain is made on the basis of experimental dependences of the threshold current and differential quantum efficiency on the cavity length. The threshold current is decomposed into principal components in terms of model approximations taking into account the Auger recombination, ejection of electrons from QWs into waveguide layers, and lateral current spreading to passive regions of a mesa-stripe laser. __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 36, No. 3, 2002, pp. 364–374. Original Russian Text Copyright ? 2002 by Pikhtin, Sliptchenko, Sokolova, Tarasov.     

Well width dependence of gain and threshold current in GaAlAs single quantum well lasers

The optical gain of single quantum well GaAs/GaAlAs laser diodes is studied theoretically. The model uses a nok-selection rule and Fermi statistics to obtain the gain coefficient expression. Gain-current characteristics are then reported and allow comparison of structures with well widths between 50 and 400 Å. Comparison is also made to previous models which use a strictk-selection rule. Then theoretical threshold current densities are calculated for typical single quantum well lasers where the optical confinement is performed using a five-layer slab waveguide. They are shown to be relatively insensitive to the well width as long as Lzis larger than 80 Å. Comparison between two different structures shows that optical confinement plays a critical role for optimizing the threshold Current and should be carefully studied, especially if thek-selection rule is relaxed.     

Optimal quantum well width and the effect of quantum well position on the performance of transistor lasers

Transistor laser (TL) model based on InGaP/GaAs/InGaAs/GaAs is analyzed and presented. It is realized that quantum well (QW) with width of 10 nm may be formed for low base threshold current density J th . The emission wavelength is found to be 1.05 μm, and the indium (In) composition is 0.25 for optimal QW width. It is identified that J th decreases with the movement of QW towards the base-emitter (B-E) interface. Small signal optical response is calculated, and the effect of QW position is studied. The bandwidth is enhanced due to the movement of the QW towards the emitter base junction.     

Increase in the internal optical loss with increasing pump current and the output power of quantum well lasers

Semiconductors - The operating characteristics of semiconductor quantum-well lasers, calculated with consideration for an increase in the internal optical loss in the waveguide region with...     

On the current dependence of low-frequency noise in bipolar transistors

The bias dependent characteristics of the base input flicker noise or 1/f noise current generator in bipolar transistors is examined. A simple technique is presented for the determination of the flicker noise magnitude at selected low frequencies with varying collector bias current. The results indicate that the bias dependence of the flicker noise is intimately rated to that of the input conductance parameter gπin the common-emitter configuration. Practical methods are given for the determination of the bias-independent noise parameter ρ0, which, in conjunction with the small-signal network parameters, fully characterize the device noise performance at low frequencies, ρ0, is an equivalent noise resistance representing the open-circuit flicker noise voltage at the base terminal at 1 Hz. Results of noise figure measurements on several representative commercially available devices are compared with those calculated with a knowledge of ρ0.     

面阵半导体激光器的耦合理论设计

用光线追迹方法计算了面阵半导体激光器的光束在透镜导管内传播及分布情况。理论给出了设计透镜导管时主要考虑的参数及其选取原则,在输出平面上得到了近高斯分布的激光输出,理论表明,利用透镜导管对面阵半导体激光器进行耦合能够获得高功率密度的光束输出,这种方法将是今后高功率全固态激光器耦合系统的主要耦合方法。     

The correlation function of Gaussian noise passed through nonlinear devices

This paper is concerned with the output autocorrelation functionR^{y}of Gaussian noise passed through a nonlinear device. An attempt is made to investigate in a systematic way the changes inR^{y}when certain mathematical manipulations are performed on some given device whose correlation function is known. These manipulations are the "elementary combinations and transformations" used in the theory of Fourier integrals, such as addition, differentiation, integration, shifting, etc. To each of these, the corresponding law governingR^{y}is established. The same laws are shown to hold for the envelope of signal plus noise for narrow-band noise with spectrum symmetric about signal frequency. Throughout the text and in the Appendix it is shown how the results can be used to establish unknown correlation function quickly with main emphasis on power-law devicesy = x^{m}withmeither an integer or half integer. Some interesting recurrence formulas are given. A second-order differential equation is derived which serves as an alternative means for calculatingR^{y}.     

Some considerations for reduction of noise and instability improvement in high-power crossed-field devices

The maximum potential of the high-power crossed-field devices has been restricted because of the presence of instability in these devices without any RF drive. The experimental investigation of the crossed-field instability as found from various tubes is briefly reviewed. It is believed that this instability is due to interaction of the slow cyclotron wave with the fast forward circuit wave. The theoretical work presented here refers to the interaction of both the slow and fast cyclotron waves with either of the circuit waves. The tuning characteristics of the interacting (oscillating) frequency due to slight changes in beam velocity resulting from changes in sole-to-anode voltage or magnetic field are derived. It is found that there is a good correlation between the theoretical and experimental results only for the case of interaction of the slow cyclotron wave with the fast forward circuit wave. For other interactions the tuning characteristics have opposite signs. In order to achieve a stable and less noisy operation of the device it is necessary to avoid the interaction of the cyclotron modes with the circuit wave. This limits the usable bandwidth which is plotted for different operating parameters. The electronic efficiency depending upon these operating parameters is also discussed. The problems in the gun design are reviewed. It is estimated that the conventional Kino gun may be used without any loss in bandwidth and efficiency up to frequencies in L band provided design procedures outlined in the paper are followed. For higher frequencies one has to use modified guns unless a reduction in bandwidth and efficiency can be tolerated.     

Monolithic integration of multiple quantum well DFB lasers and electroabsorption modulators

Advanced fibre optics telecommunication systems rely on high performance components amongst which photonic integrated circuits (PICs) play a major role. In particular, there has been a growing need for low chirp optical sources, such as externally modulated distributed feedback (DFB) lasers. In this paper, the various monolithic integration schemes of multiple quantum well DFB lasers and electro-absorption modulators are reviewed and typical applications of these devices are briefly presented.     

On the quantum limit of intensity and phase noise in negativefrequency feedback lasers

The quantum limit of intensity and phase noise in negative frequency feedback semiconductor lasers is calculated. It is shown that under some conditions the number-phase uncertainty can be reduced to the ultimate Heisenberg uncertainty limit     

Threshold current analysis of compressive strain (0-1.8%) inlow-threshold, long-wavelength quantum well lasers

A comprehensive study of the effect of compressive strain on the threshold current performance of long-wavelength (1.5 μm) quantum-well (QW) lasers is presented. Model predictions of threshold currents in such devices identify QW thickness as a parameter that must be considered in optimizing laser performance when Auger currents are present. Experimental comparisons between strained and unstrained devices reveal strain-induced reductions in internal transparency current density per QW from 66 to 40 A/cm², an increase in peak differential modal gain from 0.12 to 0.23 cm/A, and evidence for the elimination of intervalence band absorption as compressive strain increases from 0 to 1.8%. However, most of these improvements arise in the first ~1% of compressive strain. To fabricate low-threshold 1.5-μm buried heterostructure (BH) devices in InP using the strained QW active regions an optimized design which shows that threshold current is at its lowest when the stripe width is approximately 0.6-0.7 μm is derived. Results for uncoated BH lasers are reported     

Effect of electrical and thermal stress on low-frequency noise characteristics of laser diodes

In this paper, we study the electrical noise of commercially available laser diodes: a group of index guided AlGaInP diodes lasing at 635 nm (SDL3038-11) and a group of InGaAlP-multi-quantum-well diodes lasing at 670 nm (SVL71B). In particular, the effect of stress (high current and high temperature) on the noise is investigated. Measurements of the magnitude of the 1/f noise as a function of the operating current (10 nA to 10 mA) revealed an anomaly. After increasing proportionally with the current at small currents (10 nA to 10 μA), the 1/f noise tends to saturate with increasing currents in the range from 10 to 100 μA. For larger operating currents, the 1/f noise increases again with the current, proportional to I². This anomaly is even more pronounced after the devices have been stressed. We conclude that measurements of the 1/f noise at low bias currents are sensitive to the degradation of the active region of the laser diodes, while measurements of the 1/f noise at high bias currents can predict failure related to the quality of the crystal layers of the laser diodes.