共查询到19条相似文献,搜索用时 140 毫秒
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根据多模速率方程,利用MATLAB提供的SIMULINK软件包对垂直腔面发射激光器(VCSELs)和边发射激光器(EELs)多模弛豫振荡进行了研究。结果表明,与单模情况相比,多模时EELs弛豫振荡频率增大、弛豫和延迟时间缩短,而VCSELs动态特性变化不大。与此同时,在得出VCSELs的单模工作、高速调制以及提高偏置电流或自发辐射因子可改善两类器件动态特性等结论外还看到,VCSELs边模抑制比(SMSR)随偏置电流变化率高于EELs;自发辐射因子增大时,边模强度同比例增大、主模强度减小,利用微腔效应有效控制自发辐射因子可以优化VCSELs的单模特性。 相似文献
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光学微腔中偶极子自发辐射受到空间和频谱调制,能实现自发辐射增强或抑制效应,而且其有源区体积可以非常小,有利于极低阈值工作和极高的调制速率.在过去的二十多年来,垂直腔面发射激光器、回音壁模式(whispering-gallery mode)微腔激光器以及光子晶体微腔激光器三类光学微腔激光器的研究取得了很大的进展.回音擘模式微腔中,模式光线由于其在微腔界面的入射角大于全反射临界角而受到限制,是一种结构非常简单的光学微腔.微盘激光器作为典型的回音壁模式微腔激光器,可利用普通的边发射激光器外延片材料,采用半导体平面工艺制作,引起了人们很大的重视.但圆对称结构的微盘激光器易于实现回音壁模式的全反射限制,却难以得到定向的激光输出,限制了它的应用.人们往往采用局部破坏圆盘的对称性、整体变形以及消逝波耦合的输出波导实现微盘激光器的定向激光输出.在圆对称的微盘结构中,模式光线在微腔与空气界面上的入射角是恒定的,而在整体变形的圆盘中,如椭圆形微腔中,模式光线在界面的入射角则不断变化,并在某些位置上小于全反射临界角而折射出光学微腔,从而实现定向输出.这种变形微盘中模式光线往往具有混沌现象,因而吸引了人们的注意. 相似文献
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外光反馈下VCSELs噪声灵敏性的理论研究 总被引:3,自引:1,他引:2
从速率方程出发,仿真得到VCSELs在不同腔体结构、自发辐射因子和线宽限制因子情况下,相对强度噪声随外光反馈水平的变化规律。结果表明:减小电流孔径或线宽增强因子可以降低VCSELs对外光反馈的灵敏性,改变自发辐射因子对此影响不大。而传统边发射激光器不属于微腔结构,对外光反馈的抑制能力较弱。 相似文献
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Using a method based on measurement of modulation frequency harmonics, we have determined experimentally the spontaneous emission factors of GaAs-AlGaAs QW vertical cavity surface-emitting semiconductor lasers with square windows of widths 10, 15, and 30 μm. The values obtained are of the order 10-4 and scale as the reciprocal of the window width. We have also assessed the reliability and accuracy of the modulation frequency harmonic measurement technique by comparison with the prior technique based on curve fitting to the light-current characteristic 相似文献
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Cranch G.A. Englund M.A. Kirkendall C.K. 《Quantum Electronics, IEEE Journal of》2003,39(12):1579-1587
We present an experimental and theoretical investigation into the low-frequency intensity noise characteristics of erbium-doped distributed feedback (DFB) fiber lasers. The intensity noise characteristics of six nonidentical erbium-doped DFB fiber lasers are presented along with the characteristics of the grating and doped fibers. An analytical model has been used to predict the intensity noise generated in a linear fiber laser and explain the observed noise characteristics. Overall we find good agreement between our analytical model and observations. In particular, we find the intensity noise at frequencies close to the relaxation oscillation frequency significantly elevated due to excess noise from either spontaneous emission or cavity loss modulation. These results can be used to optimize the fiber laser design for sensor applications. 相似文献
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A general formalism based on the Green's function method is given for multielectrode semiconductor lasers. The effects of both spatial hole burning and nonlinear gain are included in this formalism. An effective nonlinear gain is introduced by taking into account the influence of the laser structure and the associated distribution of the mode intensity along the cavity length and the frequency and intensity modulation properties of multielectrode semiconductor lasers are studied. A general linewidth expression which includes contributions from spontaneous emission and carrier shot noise is given. It is found that the effective α-factor affecting the linewidth is in general different from its counterpart affecting modulation and injection locking properties due to spatial hole burning and nonlinear gain. The linewidth due to various contributions is calculated for both uniform intensity distributed lasers and phase-shifted distributed feedback (DFB) lasers 相似文献
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A Green's function approach to the analysis of semiconductor lasers is formulated in a form suitable for complex cavity structures. Both the spontaneous emission rate and the effective phase-amplitude coupling factor can be accurately evaluated. For distributed-feedback (DFB) lasers, the spontaneous emission rate is strongly dependent on both the facet reflectivities and the grating coupling coefficients. The effective phase-amplitude coupling factor depends on the wavelength detuning from the gain maximum. The calculated linewidth of DFB lasers differs considerably from previous calculated results and gives better agreement with experimental results. For composite-cavity lasers, the frequency dependence of the equivalent reflectivity has a strong impact on the phase-amplitude coupling factor and the spontaneous emission rate. Distributed Bragg reflector (DBR) lasers are investigated as an example of a composite-cavity structure 相似文献
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In conventional semiconductor lasers, the dimensions of the optical cavity greatly exceed the photon wavelength, and the photon density of states forms a continuum since it is essentially that of a bulk system. On the other hand, in an ideal laser, one would like to have a single optical mode coincident with the maximum in the gain spectrum of the active medium. We show that substantial density-of-states quantization and enhancement of the fraction of photons spontaneously emitted into the lasing mode can be obtained by reducing the lateral width of the surface-emitting laser. For emission at λ=0.954 μm, the threshold current density can be drastically reduced by increasing the coupling factor to a few percent. For a cavity structure width of 0.3 μm, the threshold current density is 50 A/cm2, compared with 250 A/cm2 for the 0.6-μm cavity. At lower still lateral widths, the cavity loses its vertical character, and confinement of the lateral optical mode rapidly deteriorates. The large-signal response of microcavity lasers is slightly improved primarily due to elimination of mode competition in intrinsically single-mode microcavities, with relaxation times close to 1 ns. The enhancement of the spontaneous emission coupling factor results in an increase of the relaxation oscillation frequency and improvement in the standard small-signal response of microcavity lasers. For J=10Jth, the -3 dB modulation frequency exceeds 40 GHz. Since low threshold current densities may be achieved in microcavity lasers, the gains in small-signal performance are primarily extrinsic, i.e., higher modulation bandwidths ace accessible for the same injection 相似文献