半导体激光器输出光功率的最佳值

本文分析了半导体激光器输出光功率与镜面反射率的关系,数值计算结果表明镀制介质腔控制正反镜面反射率可以得到最佳输出光功率.此外,分析表明减少腔内损耗,减薄有源层厚度和缩小条宽对输出功率都有显著的增加.     

Modal analysis of semiconductor lasers with nonplanar mirrors

We present a formalism for analyzing laser resonators which possess nonplanar mirrors and lateral waveguiding [e.g., an unstable resonator semiconductor laser (URSL)]. The electric field is expanded in lateral modes of the complex-index waveguide and is required to reproduce itself after, one roundtrip of the cavity. We show how the waveguide modes, their gain and loss, and hence the criterion for truncation of the infinite set of modes can be derived from the Green's function of the one-dimensional eigenvalue equation for the waveguide. Examples are presented for three cases of interest-a purely gain-guided URSL, an index-guided URSL, and a gain-guided tilted-mirror resonator. We compare theoretical calculations to previous experiments.     

沟道台面衬底三段大光腔激光器

本文报道了一种新型结构的半导体激光器——沟道台面衬底三段大光腔激光器,它具有阈值电流低、高输出功率和易获得基横模单纵模工作的特点.     

High output power 1540 nm vertical cavity semiconductor optical amplifiers

Vertical cavity semiconductor optical amplifiers operating at 1540 nm are presented. The use of AlInGaAs multiple quantum well active regions resulted in record-high saturation output power of +0.5 dBm and 16 dB of fibre-to-fibre gain. These results were achieved in reflection mode operation using optical pumping by a 980 nm semiconductor laser.     

Generation of self-sustained optical pulses from transients inexternal cavity, semiconductor lasers

A novel technique to achieve self-sustained picosecond optical pulse-train generation at Gbit/s rates is presented. The technique relies on the nature of external cavity laser-switching transients and injection-locking. Preliminary experimental results confirm the practicality of the proposed technique     

Spectral linewidth reduction in semiconductor lasers by an external cavity with weak optical feedback

The linewidth narrowing of a semiconductor laser due to weak optical feedback is analysed, taking into account both phase condition and threshold change for the feedback-induced modes. The achievable linewidth reduction lies in between two limiting cases, 1/(1 + X ?(1 + ?2))2 and 1/(1 + X)2, where ? and X are the linewidth enhancement factor and the feedback parameter, respectively.     

Edge-emitting lasers with short-period semiconductor/air distributed Bragg reflector mirrors

We demonstrate a short-cavity edge-emitting 0.98-/spl mu/m GaAs-based laser with semiconductor/air distributed Bragg reflector (DBR) mirrors made by reactive ion etching (RIE). The dc and small-signal modulation properties of 100-/spl mu/m-long lasers have been measured and are characterized by I/sub th/=4.5 mA and f/sub -3dB/=30 GHz under pulsed conditions, respectively. The far-field pattern of light emanating from the DBR is also measured.     

Correlation between the optical output characteristics and the time-dependent behaviour of semiconductor lasers

Various optical output characteristics of double-heterostructure lasers have been examined, together with the response of laser emission current pulses. Correlations between the two have been observed.     

Effect of external optical feedback on spectral properties of external cavity semiconductor lasers

The effects of external optical feedback on the spectral properties of single-mode external cavity semiconductor lasers that use a graded-index (GRIN) lens in the optical cavity have been investigated. Mode rejection ratio and intensity drop-out rate of the dominant mode as a function of optical strength have been measured. These measurements show that a laser with a short (160 ?m) GRIN-lens external cavity can tolerate optical feedback as large as ?20 dB without significant penalty. This minimum optical feedback can be larger when lasers with shorter cavity length are used.     

基于半导体可饱和吸收镜的可调谐光纤激光器

为了实现锁模光纤激光器的波长可调谐, 采用半导体可饱和吸收镜(SESAM), 搭建了环形腔被动锁模掺镱光纤激光器。在腔内无偏振控制器及可调谐滤波器等器件的前提下, 通过改变光纤跳线端面至SESAM的距离, 实现光谱在1029.5nm~1042.7nm之间的稳定可调谐, 基频重复频率为18.0MHz, 脉冲宽度为130ps, 锁模脉冲信噪比达44dB。结果表明, 该锁模光纤激光器具有较高的信噪比及较宽的可调谐范围。该研究为可调谐被动锁模光纤激光器的研制提供了重要的参考价值。     

Spectral characteristics of semiconductor lasers with optical feedback

Optical feedback-induced changes in the output spectra of several GaAlAs lasers operating at 0.83 μm are described. The feedback radiation obtained from a mirror 60 cm away from the laser is controlled in intensity and phase. Spectral line narrowing or broadening is observed in each laser depending on the feedback conditions. Minimum linewidths observed with feedback are less than 100 kHz. Improved wavelength stability is also obtained with optical feedback resulting in 15 dB less phase noise. An analytical model for the three-mirror cavity is developed to explain these observations.     

Gain measurements on semiconductor lasers by optical feedback from an external grating cavity

We report on new methods to determine the curvature around maximum of the mode gain curve of homogeneously line-broadened semiconductor lasers, either by measuring the wavelength dependence of threshold current of the laser coupled to an external grating cavity or by measuring the tuning range of the laser versus the amount of optical feedback. We experimentally found the mode gain width and the current-induced peak-gain wavelength shift of a GaAlAs CSP laser to 175 Å and 2.1 Å/ mA, respectively.     

CW operation of corner cavity semiconductor lasers

Etched facet semiconductor lasers have been fabricated and tested under CW operating conditions. The lasers consist of stripes formed by proton implantation, a total internal reflection (TIR) corner, and an output coupling facet. Devices with a variety of output coupling geometries were fabricated. Laser threshold currents and spectral characteristics were measured. Threshold current levels of devices with several different aperture sizes are compared to those of structures with standard Fabry-Perot reflectors     

Coherent optical pumping of semiconductor lasers

The influence of coherent optical pumping in semiconductor lasers is investigated theoretically. In particular the mathematical conditions under which an optically pumped system behaves like an electrically (incoherently) pumped system are derived. We show that it is practically impossible to reach the interesting regime where coherent effects are important because of the inherent constraints to absorb photons at the pump frequency and to reach threshold gain at the lasing frequency. The effects of changing the temperature and of reduced dimensionality are discussed     

Measurement of optical cavity properties in semiconductor lasers byFourier analysis of the emission spectrum

We present several observations on a novel method for the evaluation of the internal loss properties in semiconductor lasers. The method we use involves Fourier analysis of the Fabry-Perot mode spectrum when operating the device below lasing threshold. The observation of various structural features in the Fourier transform domain allows us to extract important information on the laser cavity. As one example, the amount of cavity propagation loss/gain, or net gain, can be derived from the decay rate of harmonics of the Fourier spectrum. A comparison between experimental and calculated gain versus wavelength data for lasers fabricated in the AlGaAs, AlGaInP, and AlGaInN material systems is given. As a second example, this method also allows the identification of the density and strength of intracavity scattering centers. This is an important capability for the fabrication of blue diode lasers in the gallium-nitride material system     

Digital optical signal processing with polarization-bistable semiconductor lasers

The operations of a complete set of optical AND, NAND, OR, and NOR gates and clocked opticalS-R, D, J-K,andTflip-flops are demonstrated, based on direct polarization switching and polarization bistability, which we have recently observed in InGaAsP/InP semiconductor lasers. By operating the laser in the direct-polarization-switchable mode, the output of the laser can be directly switched between the TM00and TE00modes with high extinction ratios by changing the injection-current level, and optical logic gates are constructed with two optoelectronic switches or photodetectors. In the polarization-bistable mode, the laser exhibits controllable hysteresis loops in the polarization-resolved power versus current characteristics. When the laser is biased in the middle of hysteresis loop, the light output can be switched between the two polarization states by injection of short electrical or optical pulses, and clocked optical flip-flops are constructed with a few optoelectronic switches and/or photodetectors. The 1 and 0 states of these devices are defined through polarization changes of the laser and direct complement functions are obtainable from the TE and TM output signals from the same laser. Switching of the polarization-bistable lasers with fast-rising current pulses has an instrument-limited mode-switching time on the order of 1 ns. With fast optoelectronic switches and/or fast photodetectors, the overall switching speed of the logic gates and flip-flops is limited by the polarization-bistable laser to < 1 ns. We have demonstrated the operations of these devices using optical signals generated by semiconductor lasers. The proposed schemes of our devices are compatible with monolithic integration based on current fabrication technology and are applicable to other types of bistable semiconductor lasers.     

Mode partition in semiconductor lasers with optical feedback

The authors point out that random noise processes induce mode partition fluctuations in semiconductor lasers. Mode partition depends on laser parameters and modulation current. However, external optical feedback can also increase mode partition noise. Here, a numerical solution of multimode noise-driven rate equations with time-delayed terms is utilized to investigate mode partition in semiconductor lasers with reflecting feedback. Photon statistics of the main and side modes in semiconductor lasers under both CW operation and dynamic operation are considered. Probability-density curves for the main and side modes are shown. The feedback-induced change of photon statistics of the main and side modes is clearly seen. Numerical results indicate that, if the laser used is exposed to reflections, a more stringent mode discrimination requirement for suppressing the buildup of laser-cavity longitudinal side modes may result. If mode discrimination is insufficient for avoiding the excitation of side modes, the feedback-induced power penalty depends on the fiber dispersion     

Waveguide external cavity narrow linewidth semiconductor lasers

Narrow linewidth light source is a prerequisite for high-performance coherent optical communication and sensing.Waveguide-based external cavity narrow linewidth semiconductor lasers(WEC-NLSLs)have become a competitive and attractive candidate for many coherent applications due to their small size,volume,low energy consumption,low cost and the ability to integrate with other optical components.In this paper,we present an overview of WEC-NLSLs from their required technologies to the state-of-the-art progress.Moreover,we highlight the common problems occurring to current WEC-NLSLs and show the possible approaches to resolving the issues.Finally,we present the possible development directions for the next phase and hope this review will be beneficial to the advancements of WEC-NLSLs.     

Transient effects in external cavity semiconductor lasers

In several important applications of external cavity operated semiconductor lasers, including studies for FM optical communication and frequency stabilized lasers for coherent communication systems, the transient response of the laser is of crucial importance. In this letter, we present a first study of the transient optical response following a step current excitation applied to an AlGaAs laser operating in a dispersive external cavity. The study shows for the first time that, for optical feedback near the gain peak of the laser, a steady state is reached after only three roundtrips in the external cavity. However, for optical feedback far (∼100 Å) from the gain peak, 20 or more roundtrips are required before a steady state can be reached. It is also shown that under certain operation conditions the optical feedback can induce damped relaxation oscillations at each subsequent roundtrip in the external cavity.     

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.