半导体激光器储备池计算系统的工作点选取方法

半导体激光器储备池计算系统的性能受很多因素的影响,如虚节点间隔、激光器的偏置电流和反馈强度等.对于光注入信号方式,注入强度和频率失谐的大小也会影响系统的性能,使得工作点更难确定.为此,本文以10阶非线性自回归移动平均任务为基础,提出一种选取半导体激光器储备池计算系统的最佳反馈强度与注入强度的方法.该方法通过寻找在某一反馈强度和连续光注入条件下,对应于储备池的注入锁定状态的最小注入强度来确定注入锁定状态的边缘;沿此边缘,通过测试系统性能选取最佳反馈强度以及与之配套的注入强度.综合前人对其他参数的研究,进一步提出完整工作点参数的选取方法.在所选取的工作点参数下,仅用50个虚节点即获得低至0.3431的归一化均方根误差,说明所提出的工作点选取方法是可行的.通过混沌时间序列预测和手写数字识别任务,验证了该方法对回归和分类问题的通用性.

Cavity-Mode Properties of Semiconductor Lasers Operating in Strong-Feedback Regime

This paper investigates the modal properties of semiconductor lasers operating in the strong-feedback regime. Analytical expressions are developed based on an iterative travelling-wave model, which enable a complete and quantitative description of a compound cavity mode in its steady state. Additional information is provided about the physical inside into a compound laser system, such as a bifurcation diagram of the compound cavity modes for full variation range （from 0 to 1） of the external reflection coefficient and a more general shape for the diagram of photon density versus mode phase - this latter will reduce to the classical ＂ellipse＂ in the weak-feedback regime. It is shown that in the strong-feedback regime, a feedback laser is characterized by a small mode number and a high density of photons. This behavior confirms previous experimental observations, showing that beyond the coherence-collapse regime, the compound laser system could be re-stabilized, and that as a result power-enhanced low-noise stable laser operation with quasi-uniform pulsation is possible with external-mirror reflectivity close to 1. Moreover, it is also shown that for a compound system operating in the strong-feedback regime, an anti-reflection treatment of a laser can significantly reduce its current threshold, and that in the absence of this treatment excitation of a minimum-linewidth mode with higher output power would be possible inside such a system. Finally, it is shown that in the weak-feedback regime except for a phase shift the iterative travelling-wave model will reduce to the Lang-Kobayashi model in cases where the product of the feedback rate and the internal round-trip time is much less than unity （that would mean in situations of as-cleaved lasers）.

Experimental demonstration of λ/8 DFB semiconductor laser array for 1.3 μm CWDM system

In this article,we report the first experimental demonstration of an eight-wavelength λ/8 phased-shifted laser array based on the REC technique in the 1.3 μm wavelength domain.Measurement results exhibit good linearity of lasing wavelength with+/-0.35 nm wavelength residual.The SLM property was ensured with SMSRs all larger than 38 dB.Moreover,the directmodulation performance was also tested.The experimental results show that the modulation bandwidth can reach up to 13GHz even at the small injection current of 40 mA and the measured spurious-free dynamic range(SFDR)is up to 87 dB/Hz2/3,which shows good linearity.These measurements show that REC-based λ/8 phased-shifted laser array has good modulation performance and it may find potential application in actual fiber-optic systems.

A near-infrared methane detection system using a 1.654 μm wavelength-modulated diode laser

By adopting a distributed feedback laser(DFBL) centered at 1.654 μm, a near-infrared(NIR) methane(CH4) detection system based on tunable diode laser absorption spectroscopy(TDLAS) is experimentally demonstrated. A laser temperature control as well as wavelength modulation module is developed to control the laser's operation temperature. The laser's temperature fluctuation can be limited within the range of-0.02—0.02 °C, and the laser's emitting wavelength varies linearly with the temperature and injection current. An open reflective gas sensing probe is realized to double the absorption optical path length from 0.2 m to 0.4 m. Within the detection range of 0—0.01, gas detection experiments were conducted to derive the relation between harmonic amplitude and gas concentration. Based on the Allan deviation at an integral time of 1 s, the limit of detection(Lo D) is decided to be 2.952×10^(-5) with a path length of 0.4 m, indicating a minimum detectable column density of ~1.2×10^(-5) m. Compared with our previously reported NIR CH_4 detection system, this system exhibits some improvement in both optical and electrical structures, including the analogue temperature controller with less software consumption, simple and reliable open reflective sensing probe.

Compact diffraction grating laser wavemeter for cold atom experiments

We present an innovative and practical scheme of building a miniaturized wavemeter, with the advantages of low cost, high reliability and simple structure. Through a calibration test by a 780 nm external cavity diode laser(ECDL), the results show that our system gets a wavelength resolution of better than 1 pm, measurement accuracy of better than 2 pm(corresponding to a frequency of 1 GHz), and a measurement range of 8.5 nm. Finally, the multi-mode comparison test between our system and a commercial spectrum analyzer further indicates the high-precision, miniaturization and low cost of the proposed system, which shows that it is particularly suitable for ECDL and atom cooling and trapping experiments. The system design, experimental results and conclusions are of definite significance as a fine reference for other ranges of wavelength.