外腔半导体激光器动态模稳定性的研究

为了研究调谐过程中外腔半导体激光器的模稳定性,采用多光束干涉理论推导Littrow结构外腔半导体激光器的腔增益,并模拟其模结构。分析了光栅面和转臂不在同一平面的情形下,在光栅转动调谐时,通过匹配光栅的反馈波长变化率与外腔波长变化率,推导出最佳的初始外腔长度,并研究了动态模稳定（无跳模调谐）的范围;采用严格的耦合理论和光线变换矩阵分析了准直（耦合）透镜的位置对系统后向耦合效率的影响。结果表明,系统后向耦合效率最大可达99%,极大地压窄了中心波长为780nm半导体激光器的线宽,外腔半导体激光器的理论线宽为未加外腔时的0.96%,动态模稳定范围可达6.8nm。     

光纤光栅外腔半导体激光器输出特性耦合效率的研究

本文采用射线追踪法,导出了光纤光栅外腔半导体激光器(FGESL)的连续输出谱P(λ)及输出功率的隐函表达式.在此基础上,结合载流子速率方程,对外腔半导体激光器的P(λ)及P-I特性进行了研究.结果表明:光纤光栅外腔的输出谱在反射带宽内呈现出多峰结构,峰值与耦合效率有关;随着祸合效率的增大,输出功率整体上呈现上升的趋势,并在上升过程中出现的抖动越来越小.     

Very high CW output power and power conversion efficiency from current-confined CDH-LOC diode lasers

CDH-LOC lasers with tight current confinement to the lasing region provide CW output powers as high as 165 mW. The overall power conversion efficiency in CW operation reaches values of 35% (front-facet emitted power/overall input electrical power). Single-longitudinal-mode and fundamental-mode operations are achieved to 40 mW CW and 60 mW peak power (50% duty cycle), respectively. The threshold-current temperature coefficient T0 reaches values of 185 K.     

A linearized theory for the diode laser in an external cavity

A simple model for a semiconductor diode laser in an external cavity is developed. The stability and small-signal modulation characteristics of the new model is investigated and compared with experiment.     

Line broadening and intensity noise due to polarization switchingin external cavity diode lasers

The authors report on polarization switching as a new source of linewidth broadening and intensity noise in external grating diode laser setups that emit in a sequence of alternating wavelength intervals having TE and TM polarization, respectively. At the borders between two consecutive intervals, the continuous random hopping of the system between the two polarizations results in line broadening and in RIN values of -100 dB/Hz at frequencies below 100 MHz. In the middle part of each wavelength interval, linewidth of less than 300 kHz and low noise (<-145 dB/Hz) have been measured     

Polarization of the output of InGaAsP semiconductor diode lasers

Measurements of the degree of polarization (ρ) of the output of 1.3-μm InGaAsP semiconductor diode lasers as a function of current are discussed. It is found that ρ measured for well below threshold (ρ_b) is a better indicator of mechanical strain in the active region than ρ measured near or above threshold. ρ_b exhibits little dependence on drive level, mode reflectivity, threshold, or saturation of the gain. A possible correlation between the magnitude of ρ_b and device operating characteristics was found. More work is required to confirm this possibility. Data which provide experimental evidence for the magnitude of the difference between the reflectivities of the TE and TM modes are presented     

双体光栅外腔二极管激光器光谱特性研究

为了研究双体布喇格光栅外腔二极管激光器的衍射特性,采用一块体布喇格光栅与一块横向啁啾体布喇格光栅组成双体布喇格光栅,理论分析了组合前后体布喇格光栅的衍射特性,实验研究了双体布喇格光栅外腔二极管激光器的输出光谱特性。结果表明,在双体布喇格光栅外腔反馈的作用下,可以实现双波长同时输出,通过横向移动横向啁啾体布喇格光栅,可以在保持其中一个中心波长不变的情况下,使另外的一个波长在800nm~815nm的范围内线性调谐。此研究为基于双体布喇格光栅实现双波长输出的大功率二极管激光器提供了实验指导。     

光纤光栅外腔半导体激光器输出谱的射线法研究

本文采用射线法,计及增益随波长的变化,首次导出了光纤光栅外腔半导体激光器(FGESL)输出谱的表达式.利用该表达式,结合载流子速率方程,对FGESL输出谱的精细结构进行研究.研究结果表明:光纤光栅外腔将引起位于反射带宽附近波长处能量分布发生变化,在反射带宽内出现多峰结构,峰的数目与外腔长度有关;随着电流的增大,FGESL的输出功率和边模抑制比总体呈现上升的趋势,上升过程中存在波动,波动的幅度和频率随着前端面反射的减小而减小.     

外腔锁相改善半导体激光器列阵输出光束特性

采用一个由快轴准直透镜和一个高反射率平面镜组成的简单外腔,实现了半导体激光器列阵(DLA)锁相运行,改善了DLA的出射光束质量。DLA远场出现了3个瓣,每瓣发散角为10mrad左右;光谱从自由运行时的2 .2nm压缩到了0 .3nm ;阈值电流由7A降低到了5 .5A。     

Tapered diode lasers at 976 nm with 8 W nearly diffraction limited output power

High-efficiency tapered diode lasers with ridge-waveguide structure emitting at 976 nm have been realised. High wall-plug efficiencies of more than 57% result in output powers of more than 12 W for a single emitter with 3.5 mm resonator length. A nearly diffraction limited behaviour has been demonstrated up to 8.3 W CW.     

Lateral mode stabilization of diode lasers by means of apertured facet reflectors

We report the design, fabrication, and testing of an apertured facet reflector for a GaAs/GaAlAs room temperature CW diode laser. The reflector, composed of Al2O3, Si, Te, and Al2O3layers with the Te ablated by the laser beam itself at the mode center, has a higher reflectivity at its center compared to the unablated surrounding region. This nonuniform reflectivity acts to stabilize laterally the fundamental mode and substantially increase the "kink" level. Specifically, the "kink" level of a large optical cavity (LOC) heterostructure laser with an 8 μm wide stripe was increased from ≈ 10 mW before coating to above 30 mW by the addition of the apertured reflector.     

Linewidth of monolithic external cavity DFB lasers

An expression for the linewidth of DFB lasers with lossy external cavities is derived. The influence of facet reflectivity and high feedback levels is discussed     

外腔式He-Ne激光器的偏振特性

实验观察到外腔式He-Ne激光器由于增益管的应力双折射效应而呈现复杂的偏振特性.对几种典型的增益管的应力双折射相移进行了理论分析和实验测量.在增益管端口的增透片上施加适当的径向压力可获得单一的线偏振光输出.     

Effect of external reflectors on longitudinal modes of distributed feedback lasers

The effect of external reflectors on longitudinal modes of distributed feedback (DFB) lasers is analyzed. The general case of dissimilar reflectors arbitrarily located relative to the phase of the DFB structure is considered. An eigenvalue equation for the propagation constants is derived and solved numerically for a variety of practical cases. Longitudinal mode thresholds, wavelengths, separations, and field distributions are obtained for GaAs lasers and for DFB lasers with a single reflector. It is shown that these quantities are very sensitive not only to the relative strength of the discrete and DFB, but also to the relative phases. Quite asymmetric transmitted powers are shown to occur under a variety of circumstances.     

Broadly wavelength-tunable external cavity lasers with extremely low power variation over tuning range

Tunable external-cavity lasers with low power variation over a broad tuning range are demonstrated using asymmetric multiple quantum-wells with a wide and flat gain. For a 2.8-/spl mu/m-wide ridge waveguide laser of cavity length 380 /spl mu/m, when used in a grating external cavity and with an antireflection coating on one facet of laser diode chip, the power variation of less than -1 dB is obtained over a range of 80 nm. This extremely low power variation is a direct result of the spectrally flat gain.     

Polarization state of the emission of external grating diode lasers

The laser emission of transverse electric (TE) and transverse magnetic (TM) polarization, in alternating successive spectral ranges, that can occur when external grating diode lasers are wavelength tuned, is theoretically and experimentally investigated. The modulated threshold gain curves of the external cavity for the two polarizations can be made to intersect with each other if a grating is used in such a way as to practically eliminate the difference between the laser diode losses and confinement factors for TE and TM polarization. The result is a sequence of wavelength ranges where the threshold gain is alternately lower for the TE resp. TM polarization. Within each range, a wavelength tunable single mode laser emission is obtained. The phenomenon is described, taking into account the characteristics of the key components of the external cavity, i.e., laser diode structure, antireflective (AR) coating, and grating efficiency. Design tools are proposed for the characteristics of the components necessary for the development of such an external cavity. The theoretical and design concepts are experimentally confirmed in a number of external cavities, using diode lasers emitting around 1.5 μm, with different types of antireflective coatings, as well as different grating configurations     

外腔可调谐激光器调制特性研究

随着 WDM-PON(波分复用-无源光网络)应用中对低成本无色光发射模块需求的日益增长,基于混合集成的小型化外腔可调谐激光器,凭借其实现工艺简单、信号质量好和调谐范围宽等优良特性,受到越来越多的关注。文章在研究分析外腔激光器调制特性的影响因素的基础上,对特定结构的小型化外腔可调激光器进行了实验开发和特性研究,在激光谐振腔腔长对调制带宽的影响方面得到了一些有价值的结论,这可为后期器件开发提供理论支持。     

Relation between the cavity detuning and the output opticalintensity in free-electron lasers

The authors use a simple model of saturation in free-electron lasers operating with pulsed beams to study the intensity growth as a function of the cavity mismatch and of the coupling parameter. In spite of the simplicity of the model, the dependence of the intracavity power, as a function of the cavity detuning, is reproduced remarkably well. It is also pointed out that an enhancement of the optical power is obtained by adjusting the cavity length while the optical signal grows. The problem is analyzed qualitatively and realization schemes are proposed