Analysis of the spectral linewidth of distributed feedback laser diodes

The spectral linewidth of distributed feedback (DFB) laser diodes is theoretically studied. Numerical calculation shows that DFB lasers with long cavity lengths and large coupling coefficients have very narrow spectral linewidth less than 1 MHz, The effects of the phase shift and mirror facets on the spectral characteristics of DFB lasers are also analyzed, It is shown that the phase-shifter further narrows the spectral linewidth of DFB lasers. Its numerical result and physical meaning are also shown.     

Analysis of the spectral linewidth of distributed feedback laser diodes

The spectral linewidth of DFB laser diodes is analysed. DFB lasers with long cavities are shown to have very narrow spectral linewidth, and it is further narrowed if a phase shift is introduced at the centre of the cavities.     

Demonstration of saturation spectra of caesium D/sub 2/line with a low linewidth distributed feedback laser diode

Low linewidths for Al-free active region distributed feedback lasers using a self-heterodyne measurement method (minimum beat width of 0.8 MHz at 20 mW and 12 C, 1.2 MHz at 852.12 nm 35 mW and 36 C) are demonstrated. Singlemode emission was achieved at 852.12 nm corresponding to the D₂ caesium transition, with an optical output power of 35 mW at 140 mA under CW operation. Finally, the saturation spectra of caesium atoms with the DFB laser diode was recorded with a resolution close to the natural linewidth.     

Measurement of spectral linewidth of AlGaAs/GaAs distributed feedback lasers

The spectral linewidth of AlGaAs/GaAs distributed feedback (DFB) lasers was measured for the first time. The linewidth-power product decreased with temperature, which indicates that the relative position of the oscillation wavelength and the gain peak strongly affects the linewidth of DFB lasers.     

A novel distributed feedback fiber laser based on equivalent phase shift

A distributed feedback fiber laser employing an equivalent phase shift (EPS) of /spl pi/ is studied theoretically and experimentally for the first time. The EPS is formed through extending one sampling period by 50% in the center of a sampled Bragg grating. An output power of 0.20 mW with sidemode suppression of 67 dB is experimentally observed.     

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。     

Strained multiquantum-well corrugation-pitch-modulated distributed feedback laser with ultranarrow (3.6 kHz) spectral linewidth

Introducing a 1% compressive strained multiquantum-well (MQW) active layer into a corrugation-pitch-modulated distributed feedback (CPM-DFB) laser reduces the linewidth floor (residual linewidth for extrapolated infinite output power) to 2 kHz and results in a linewidth-power product of 140 kHz. mW. Strained MQW CPM-DFB lasers produced a 55 mW output with a spectral linewidth of only 3.6 kHz.<>     

Effect of 1/f noise on the spectral linewidth of corrugation-pitch-modulated multiquantum-well distributed feedback lasers at high output power

The mechanism by which spectral linewidth reduction saturates in CPM-MQW-DFB (corrugated-pitch-modulated multiquantum-well distributed feedback) lasers at high output powers is investigated by measuring the spectral power density of their FM noise. Linewidth saturation is caused by the 1/f component of this noise.<>     

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.<>     

Extremely narrow spectral linewidth and low chirping of theMQW-DFB-PPIBH laser diode

The low threshold current of 9 mA, the high side-mode suppression ratio of more than 45 dB, the extremely narrow spectral linewidth of 1.1 MHz, and the low chirping of 2.8 Å at -20 dB at 2 Gb/s nonreturn to zero (NRZ) modulation have been achieved in the multiple quantum well (MQW) distributed feedback (DFB) p-substrate partially inverted buried heterostructure (PPIBH) laser diode. The spectral linewidth of 1.1 MHz is the narrowest value among 300-μm-length solitary laser diodes. These results suggest that the MQW-DFB laser diodes are a promising light source for longer distance and higher bit-rate optical communication systems and coherent optical communication systems     

An optimized π/2 distributed feedback laser

The effects of a periodicity interruption (phase slip) in distributed feedback lasers are investigated with attention given to the practical aspects of today's semiconductor lasers in the 1.5 μm region. We find that effects on gain threshold and mode discrimination should be large and favorable if the size and placement of a phase slip are correct.     

Spectral linewidth estimation of a 1.5 µm range InGaAsP/InP distributed feedback laser

Spectral linewidth of a 1.5 μm range distributed feedback buried heterostructure (DFB-BH) laser in CW operation is estimated theoretically and experimentally. Considering the equivalent mirror facet loss coefficient and the confinement factor in the active layer, etc., we modified the conventional formula for the spectral linewidth of single-mode semiconductor lasers and presented a formula for the linewidth of DFB lasers. Furthermore, power-dependent linewidth measurements of a 1.5 μm range InGaAsP/InP DFB-BH laser with a window region were carried out using Fabry-Perot interferometers. The linewidth was observed to increase linearly with inverse output power. The measured result was explained by the calculated result through the modified formula. The full width at half maximum was estimated to be 50 MHz at an output power of 1 mW.     

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     

Lasing mode and spectral linewidth control by phase tunable distributed feedback laser diodes with double channel planar buried heterostructure (DFB-DC-PBH LD's)

Lasing mode selection between ±1 modes across the stop-band and spectral linewidth tunability have been experimentally observed with newly developed phase tunable distributed feedback laser diodes with double channel planar buried hetetostructure (DFB-DC-PBH LD's) for the first time.     

808nm DFB半导体激光器的光栅制备

实验优化设计了808nm DFB半导体激光器的二级布拉格光栅结构,介绍了808 nm分布反馈（DFB）半导体激光器光栅制备的工艺过程。采用全息光刻方法和湿法腐蚀技术在GaAs衬底片上制备了周期为240nm的光栅图形,全息光刻系统采用条纹锁定技术降低条纹抖动和提高干涉稳定性,腐蚀液采用H3PO4 : H2O2 : H2O (1 : 1 : 10),腐蚀时间为30s。光学显微镜、扫描电子显微镜（SEM）和原子力显微镜（AFM）测试显示,光栅周期为240nm,占空比为0.25,深度为80nm,具有完美的表面形貌,及良好的连续性和均匀性。     

分布反馈光纤激光水听器相位一致性的测试方法

在传统压电水听器相位一致性测试的基础上提出了分布反馈(DFB)光纤激光水听器相位一致性的测试方法,并搭建了测试系统.采用偏振无关的非平衡迈克尔逊干涉仪和归一化的相位载波(PGC)解调方案,解调出光纤激光水听器感受的水声信号,并与参考压电水听器作对比,使用高精度相位检测器将两信号转化为相位差信号:重复测量第二支光纤激光水...     

The optimal loop gain design for the spectral linewidth reductionin an electrical feedback semiconductor laser

The design of the optimal feedback loop gain for the spectral linewidth reduction in a semiconductor laser with electrical feedback is presented using a model of self-heterodyne type electrical feedback. The results show that the feedback loop gain must be suitably chosen to satisfy the requirement of narrowing linewidth. Due to the influence of AM noise in the feedback process, there is an optimal value for the feedback loop gain to reduce the linewidth for a given feedback condition. The influence of other feedback parameters on the linewidth reduction is also presented     

Narrow spectral linewidth 1.5 μm GaInAsP/InP distributed Braggreflector (DBR) lasers

The spectral linewidth of distributed Bragg reflector (DBR) lasers is discussed. The narrowest linewidth of 3.2 MHz was obtained at P =1.5 mW. It was found that narrow spectral linewidths can be obtained constantly for the DBR lasers with long and low optical loss corrugation regions, and with a small coupling coefficient. These results are explained by the external cavity model, which is used in the theoretical analysis. To increase the output power of the narrow-linewidth DBR lasers, AR (antireflection) coating was applied to the output facet. Improved quantum efficiency and submode suppression were achieved. Degradation of the linewidths by the AR coating was insignificant     

External feedback effects on I/L characteristics of laser diode

A new effect of an external cavity on the optical power against injected current curve of an AlGaAs laser diode is reported. A simple multimode rate equation model describes this feature and leads to a novel method of measuring the current-dependent frequency deviation in the low-frequency region, without using spectroscopic instrumentation.<>     

Surface emitting InGaAsP/InP distributed feedback laser diode at 1.53 mu m with monolithic integrated microlens

Monolithic integration of a distributed feedback (DFB) surface-emitting laser diode with a microlens is demonstrated. The transverse and longitudinal cross-sectional views of the laser diode are illustrated. The microlens and a DFB laser structure are located on opposite sides of an n-InP substrate. 11 mA minimum continuous wave (CW) threshold current and 5 mW CW emission perpendicular to the InP substrate are achieved at room temperature using a chemically etched 45 degrees mirror. Single mode emission at 1.53 mu m is obtained. The integrated microlens, etched by ion beam and coated with aluminum oxide, provides optical beam collimation and an ultralow laser mode reflectivity of <10/sup -4/.<>