Emission frequency stability in single-mode-fibre optical feedback controlled semiconductor lasers

A newly designed semiconductor laser emitter with adjustable linewidth by controlling the coupling to a single-mode fibre is described with emphasis on thermal requirements to obtain a high-frequency stability. A stable operation has been achieved during more than 1 h using an AlGaAs laser diode with optical feedback from a 50 cm-long single-mode fibre resulting in a 50-fold reduction of the spectral linewidth.     

浅析元件参数对外腔半导体激光器输出谱宽影响

半导体抽运碱金属蒸气激光器（DPAL）需大功率窄线宽泵浦源,但市售半导体激光器输出线宽远远大于碱金属原子吸收谱宽,难以实现有效泵浦,因此需采用Littrow 外腔法压窄半导体激光器输出谱宽。Littrow 外腔系统中元件参数的选择直接影响大功率半导体激光器输出谱宽。为此文中沿入射光线方向构建外腔压窄模型,利用球面镜替代柱面镜,分析了微柱透镜阵列、光学系统和光栅元件对外腔输出谱宽的影响,模拟结果为微柱透镜阵列焦距越小、光栅刻线越密、球面镜焦距越大,外腔输出谱宽越窄,实验结果符合理论模型。     

光纤光栅外腔半导体激光器特性的研究

对谐振式集成光学角速率传感器 IORS 的关键器件之一——大功率、窄线宽光源进行了分析与实验 .分析结果表明 ,为达到优于 1°/ h的分辨率 ,光源应选用线宽小于 1MHz的强反馈光纤光栅外腔半导体激光器 FBG- L D ;研究了 FBG- LD的单纵模机制和线宽压窄特性 ,着重考虑了反馈端面的残留反射率对 FBG- L D输出功率的影响 ,以及耦合效率对 FBG- L D线宽的影响 ;在实验研究中采用了大功率、窄线宽、单纵模的 FBG- L D,并应用于光纤谐振腔 ,实测的谐振腔的清晰度与理论计算值是一致的 .     

Estimation of the linewidth enhancement factor for a PbCdS diodelaser

An estimation of the linewidth enhancement factor α for a PbCdS diode laser is reported. The measurement method, which is an extension of an earlier procedure involving studies of mode spectra, was devised particularly for this lead-salt diode laser of very low output power. A quite low α of 1.3 was obtained, well below the values for other types of diode lasers     

250 kHz spectral linewidth operation of 1.5 μm multiple quantumwell DFB-LDs

The spectral linewidth observed in a 1.5 μm multiple-quantum-well distributed-feedback laser diode (MQW-DFB-LD) with 1500 μm cavity length is discussed. The spectral linewidth was drastically reduced in long-cavity MQW-DFB0-LDs through a reduction in threshold carrier density. A spectral linewidth of 250 kHz, the narrowest ever achieved, was obtained     

The semiconductor laser linewidth due to the presence of side modes

The laser linewidth is evaluated by solving the rate equations for a nearly single-mode laser with two modes. The resulting linewidth contribution due to the presence of side modes is introduced by the nonlinear gain in the laser diode. For weak side modes, the linewidth contribution is proportional to the third power of the side mode intensity. A linewidth contribution of about 20 MHz for a side-mode power of 100 μW has been found experimentally for a 1.3-μm buried-heterostructure laser     

Effect of phase shift position on spectral linewidth of the π/2distributed feedback laser diode

The dependence of the spectral linewidth on the phase shift position (PSP) of a phase-shifted distributed-feedback (DFB) laser diode is investigated theoretically, using the coupled wave model. In particular, the analysis is performed to find an optimum PSP so as to minimize the spectral linewidth of the laser diode. This optimum PSP is compared to that obtained by maximizing the stability of the laser oscillation. Since both narrow spectral linewidth and good stability are essential for the light source in coherent optical communications, the analysis revealed the suitability of using phase-shifted DFB laser diodes in coherent transmissions     

Intensity noise and linewidth of laser diodes with integrated semiconductor optical amplifier

It is shown that the relative intensity noise and the linewidth of a laser diode can increase significantly if an optical amplifier is integrated with the laser diode. This increase is due to the amplified spontaneous emission from the optical amplifier.     

Novel measuring method for spectral linewidth of laser diodes using fibre-optic ring resonator

A novel measuring technique for the spectral linewidth of a laser diode was developed by using a fibre-optic ring resonator. Although the method is simple, a measuring accuracy within ±10% was obtained in the wide spectral linewidth range from 1 to 100 MHz.     

长腔长体布拉格光栅外腔半导体激光器

为了实现体布拉格光栅外腔半导体激光器(VBL)的外腔腔内光束合成,研究了长腔长VBL的激光输出特性。采用焦距为25 mm的平凸柱透镜作为单管激光二极管(LD)的慢轴准直镜,同时快轴方向体布拉格光栅(VBG)离轴放置,使得VBL的外腔腔长达到约240 mm,线宽从自由运转时的1.8 nm压窄至0.14 nm。在实验中,改变LD的偏振特性,VBL的激光输出特性不变。通过调节VBG温度,该长腔长VBL的激光中心波长从779.18 nm到779.75 nm连续可调,调谐过程中线宽基本不变。     

Tunable operation of a gain-switched diode laser by nonresonantself-injection seeding

We report tunable operation of a gain-switched diode laser by nonresonant self-injection seeding from an uncoated glass slide used as an external cavity reflector. A spectral linewidth reduction from 11 to 0.05 nm has been achieved for picosecond pulses with little effect on other laser characteristics. Good agreement with numerical simulations based on a compound-cavity laser model is also reported     

240 GHz active modelocked laser diode

A 240 GHz optical millimetre-wave (mm-wave) signal is generated by an active modelocked laser diode (MLLD) integrated with a high-mesa electroabsorption modulator. The linewidth of the generated signal is less than 10 Hz. A -11 dBm mm-wave signal at 240 GHz was also generated using the active MLLD and a uni-travelling-carrier photodiode.     

Narrow linewidth (85 kHz) operation in long cavity 1.5 mu m-MQW DBR laser

An extremely narrow linewidth of 85 kHz operation was obtained at 10 mW output power in a 2.16 mm long, 1.5 mu m-MQW DBR laser. This is the narrowest linewidth ever reported in a semiconductor laser diode without an external cavity.<>     

Controling the linewidth of a semiconductor laser withphotorefractive phase conjugate feedback

A novel technique for narrowing the linewidth of a single laser diode using photorefractive phase conjugate feedback is presented. The behavior of this system can be modeled by adapting the previously developed theory to include the phase constraints of the phase conjugate external cavity. The experiments show excellent agreement with the model. This technique produces a stable, narrow linewidth in a semiconductor laser. The comparison to the conventional case is discussed     

10 kHz-linewidth diode-pumped Er:Yb:glass laser

A single-mode Er:Yb:phosphate glass laser pumped at 980 nm by an InGaAs diode laser is reported. The laser emits over 15 mW output power with 6% slope efficiency. The measured linewidth is 10.6 kHz and the RIN power is less than 140 dB/Hz.<>     

用于Rb蒸气激光泵浦的可调谐窄线宽半导体激光器

由于Rb蒸气的吸收峰随缓冲气体气压存在漂移,利用体布拉格光栅(VBG)实现线宽压窄的同时,实现泵浦半导体激光器中心波长的可调谐也是十分必要的。本文采用国内封装的半导体激光阵列(LDA),利用VBG的温度特性,实现了线宽不大于0.3nm的同时,激光器中心波长从779.89nm到780.35nm可调谐。该激光器可以通过叠阵方式用于Rb蒸气的泵浦和激励。     

Effects of laser diode parameters on power penalty in 10 Gb/soptical fiber transmission systems

A composite tradeoff study based on the influence of key laser diode parameters on frequency chirp induced power penalty, extinction induced power penalty, the turn-on delay, and the dispersion transmission limit is presented for 10 Gb/s optical fiber transmission systems. The simulated results reveal that an optimum range of differential gain and nonlinear gain coefficient exists, and it is advantageous to set an extinction ratio that minimizes both the total power penalty and the turn-on delay. In addition, it is shown that a reduction of chirp and maximization of the dispersion transmission limit can be realized by designing the laser diode with a linewidth enhancement factor near -0.8     

Experimental determination of parasitic optical feedback by diode laser linewidth measurements

Proposes a novel method for the characterisation of parasitic optical feedback by measuring the diode laser linewidth change with injection current. Results were obtained with a MCRW (metal-clad ridge-waveguide) laser and reflections from an optical isolator. A feedback signal 67 dB below the laser output was definitely measured.<>     

Linewidth and feedback sensitivity of semiconductor diode lasers

It is shown that the feedback sensitivity of a diode laser is closely related to the free-running laser linewidth and that several formally different expressions in the literature for the linewidth with and without the explicit use of K factors are indeed essentially equivalent     

Improvement of linewidth enhancement factor in 1.55-μmmultiple-quantum-well laser diodes

The improvement of the linewidth enhancement factor in complex-coupled laser diode (CC-LD), or loss-coupled, was confirmed by measuring the spontaneous emission spectra below threshold from the sidewall of laser diodes. In addition, the serial resistance of the device was measured. The linewidth enhancement factor is improved by the presence of a light absorbing InGaAs grating for loss coupled distributed-feedback (DFB) laser diode (LD). We report the comparison of the linewidth enhancement factors of Fabry-Perot (FP) LD, conventional DFB-LD, and loss coupled DFB-LDs