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。     

Analysis of nonplanar wave propagation through multilayered Braggreflectors for folded cavity and vertical cavity surface emitting laserstructures

A theoretical approach to nonplanar wave propagation through Bragg reflector multilayer structures is presented. The theory is applied to the optical coupling and feedback in a folded cavity surface emitting laser using a 45° deflection mirror-epitaxial Bragg reflector arrangement. The effects of the nonplanar wave propagation on the Bragg mirror reflectivity in vertical cavity surface emitting lasers is also examined. Experimental verification of the theory is presented in a novel folded cavity surface emitting laser structure integrating a horizontal cavity InGaAs-GaAs laser grown on a structured substrate with a high reflectivity Bragg reflector     

Multi-element Bragg-grating based fibre-laser strain sensor

A fibre laser configuration is described which uses multiple fibre Bragg grating sensors as feedback elements. By tuning a wavelength selective filter located within the laser cavity over the gain bandwidth, the laser selectively lases at each of the Bragg wavelengths of the sensors, thus allowing strain induced shifts in the Bragg wavelengths to be monitored. A four sensor system is reported.<>     

基于线型腔拉曼光纤激光器的长距离光纤布拉格光栅传感

提出了一种基于线型腔拉曼光纤激光器的长距离分布式光纤布拉格光栅(FBG)传感解调系统,并进行了理论分析和实验验证。传感光纤布拉格光栅构成拉曼光纤激光器腔镜的一端,受一维调节器调节控制的匹配光纤布拉格光栅构成腔镜的另一端。一维调节器与步进电机相连,步进电机由计算机(PC)通过可编程逻辑控制器(PLC)进行控制,一维调节器通过调节匹配光纤布拉格光栅的周期来控制激光器的输出。实验结果表明,传感解调系统能很好地实现长距离分布式传感及传感信号的检测。30 km非归零色散位移光纤(NZDSF)用于拉曼增益可以产生信噪比大于40 dB的稳定拉曼激光输出,在4.2 nm范围内系统解调精度为0.05 nm。     

S-Band long-distance fiber Bragg grating sensor system

We propose and investigate experimentally a sigma fiber laser scheme, which uses multiple fiber Bragg grating (FBG) sensors as the feedback elements, for a long-distance sensor system with 20-km long in S-band at first. By tuning a wavelength selective filter located in a laser cavity over the gain bandwidth, the laser selectively lases at each of the fiber Bragg wavelengths of the sensors, thus allowing strain-induced shifts in the Bragg wavelengths to be monitored. In our experiment, an S-band four-sensor system is proposed and investigated experimentally.     

A compact Cherenkov laser with a Bragg cavity composed ofdielectric gratings

The growth and saturation characteristics of a Cherenkov laser with a Bragg cavity composed of dielectric gratings are investigated in detail with the aid of numerical simulation based upon the fluid model of the electron beam, For the analysis of the problem, a two-dimensional (2-D) model of the Cherenkov laser is considered which consists of a planar relativistic electron beam and a parallel plate waveguide, one plate of which is loaded with a dielectric sheet. For confinement and extraction of the electromagnetic wave, a Bragg cavity is formed by dielectric gratings fabricated at both ends of a dielectric-loaded parallel plate waveguide. The result of numerical simulation shows that a compact Cherenkov laser, the longitudinal dimension of which is about one order of magnitude smaller than that of the corresponding single-pass Cherenkov laser, can be realized by using a Bragg cavity composed of dielectric gratings     

Fiber laser source/analyzer for Bragg grating sensor arrayinterrogation

This paper reports on the application of a calibrated, narrow-linewidth, single-frequency, continuously wavelength-tunable erbium fiber laser to the interrogation of a multipoint Bragg grating temperature sensor. The fiber laser was wavelength-tuned, through an array of three fiber Bragg grating sensors, to determine the temperature of each individual grating. The temperatures of the three gratings were measured as a function of grating Bragg wavelength. The minimum wavelength resolution, due to electro-mechanical repeatability, of the fiber laser source/analyzer was determined to be approximately 2.3 picometers. This corresponds to a frequency resolution of approximately 300 MHz     

A new DBR laser structure for improved side-mode suppression

The authors propose and analyze a novel distributed Bragg reflector (DBR) laser structure that exhibits superior side-mode suppression when compared to the well-known DBR laser. This is achieved by introducing a strong symmetry in the reflectivity of the DBR section and results in a high (>36 dB) and ideally constant side-mode suppression ratio as the laser is tuned. This asymmetry in reflectivity can be achieved by nonlinearly chirping the local spatial frequency of a regular (periodic) Bragg grating.<>     

A control loop which ensures high side-mode-suppression ratio in atunable DBR laser

The authors present a control loop which ensures single-mode operation of a tunable distributed-Bragg-reflector (DBR) laser. This control loop uses no external optics. The error signal is derived from an integrated detector which measures the light transmitted through the Bragg section. Using this signal to control the current to the Bragg section, the laser is tuned to where the side-mode-suppression ratio is high. This guarantees that the laser remains single-mode, even when modulated. This servo is capable of application in wavelength-division-multiplexed (WDM) systems     

体光栅外腔半导体激光器列阵的光谱及调谐

对采用体布拉格光栅作为波长选择器件的外腔半导体激光列阵进行了实验研究。实验表明,在体光栅外腔作用下,高功率半导体激光器输出的线宽得到压窄、波长得到固定。与此同时,从布拉格衍射相关理论出发,分析了体光栅法线方向改变对激光器系统输出中心波长的影响。实验表明改变体光栅法线方向的角度,可以在一定范围内调整列阵的输出波长。     

Nonlinear operation of a planar circular-grating DBR laser

An approximate method for the analysis of the nonlinear operation of a planar circular-grating distributed Bragg reflector laser is presented. The analysis is based upon vector-wave self-consistent coupled-mode equations modified to take into account gain saturation effects. With the help of an energy theorem and threshold field approximation, an approximate formula relating small-signal gain to the output power and laser parameters is derived. The laser characteristics obtained reveal behavior of the optimal coupling strength of the Bragg reflector, which provides maximal power efficiency as a function of the laser parameters. It is also shown that the gain saturation effect provides mode selectivity in the laser structure     

Wavelength stabilization of a DBR laser using an in-fiber Braggfilter

A control loop that stabilizes the wavelength of a tunable distributed-Bragg-reflector (DBR) laser is discussed. An in-fiber Bragg grating is used as the wavelength reference. Over a 25-hour period, this control loop held the laser wavelength constant to within 0.022 nm. This variation is traced to the temperature dependence of the in-fiber Bragg grating and can be reduced by controlling the grating's temperature     

可调谐单纵模多波长光纤激光器的研究

为了实现对台阶高度和绝对距离等物理量的高精度干涉测量,采用在一个光纤激光器中构建多个激光谐振腔的方法,构建了能同时发出多波长激光的光纤激光器。每个激光谐振腔都利用掺铒光纤作为增益介质,利用光纤光栅作为波长选择元件,改变光纤光栅的布喇格波长,即可改变对应谐振腔的激光波长。各个激光谐振腔独立但部分重叠,在重叠区域利用光纤耦合器构成复合子腔,使每个激光谐振腔都是复合激光谐振腔,从而使每个激光谐振腔都发出单纵模激光。结果表明,该光纤激光器能同时发出功率和频率都稳定的多波长激光,且每个波长都是单纵模激光;在4h内,每个波长的波长稳定性优于0.01nm。该设计对可调谐单纵模多波长光纤激光器的研究是有帮助的。     

光纤光栅外腔半导体激光器理论模型分析与选取

为了讨论三腔镜近似或耦合腔近似两种等效腔模型对计算光纤光栅外腔半导体激光器等效反射率等参量的近似程度,挑选出最优的理论模型,采用数值计算的方法进行模拟仿真,得到了两种模型在采用切趾光纤Bragg光栅和非切趾光纤Bragg光栅情况下的阈值增益等特性曲线。结果表明,在采用切趾光纤Bragg光栅,特别是切趾深度较大的情况下,采用三腔镜近似模型更加符合实际情况。此研究结果对分析和设计单纵模光纤光栅外腔半导体激光器具有一定的参考价值。     

基于游标原理的可调谐分布反射全光纤激光器

报道了一种新型全光纤离散可调谐分布反射(DBR)光纤激光器。光纤激光器为短腔结构,其有源区采用Er-Yb共掺单模光纤,有源光纤长度为6 cm。激光器采用两组级联光纤布拉格光栅(FBG)为反射腔镜,前腔镜各级联光纤布拉格光栅的布拉格波长间隔为1 nm,后腔镜为0.8 nm,利用游标原理,通过对前腔镜级联光纤布拉格光栅进行机械调谐,使前后腔镜各反射波长分别对准,实现了四个固定波长间隔为0.8 nm的离散调谐。这种光纤激光器具有波长调节准确,调谐速度快,成本低的优点,可用于作为多波长光纤传输系统的发射光源或系统检测光源,进一步增加级联光栅的组数可实现更大调谐范围。     

Type II femtosecond laser writing of Bragg grating waveguides in bulk glass

Low-loss singlemode waveguides with inherent Bragg grating responses were laser written for the first time in a single process step. A periodic array of refractive index voxels were imprinted point-by-point in bulk borosilicate glass by a type II ultrafast laser photosensitivity interaction, yielding permanent grating-waveguides with 1550 nm Bragg reflection     

Parametric optimization of the Bragg reflectors in a laser with the vertical cavity and nonlinear frequency conversion

The structure of the Bragg reflectors in a vertical-cavity laser in which three-wave nonlinear mixing is used to generate the emission in the mid-infrared spectral region is optimized. It is shown that the reflection band of the Bragg reflectors can be broadened appreciably in comparison with conventional quarter-wavelength reflectors formed of the same pair of materials. Using this approach, it becomes possible to produce a laser with nonlinear frequency conversion based on the lattice-related nonlinearity in a GaAs/AlGaAs system; this laser emits in the region of <10 μm. The output characteristics of such a laser with the emission wavelength of about 9.7 μm are analyzed numerically.     

色散管理光纤锁模激光器在近零色散域的非线性优化

目前,飞秒激光脉冲因脉冲宽度窄和峰值功率高的特点被广泛运用在多种领域中。其中,色散管理光纤锁模激光器因其特有的腔内呼吸机制使输出的激光脉冲能量更高,光谱更宽、脉宽更窄。使用啁啾布拉格光纤光栅进行色散管理的光纤锁模激光器能够实现真正的全光纤结构,提升激光器的紧凑性和稳定性,因此基于啁啾布拉格光纤光栅进行色散管理的光纤锁模激光器具有更加实际的应用意义。采用数值模拟的方法,研究了基于啁啾布拉格光纤光栅进行色散管理的掺镱光纤锁模激光器中单模光纤在腔内的不同分布对脉冲动力学过程和输出脉冲参数的影响。系统分析了谐振腔内净色散值不同时,腔内单模光纤的分布对脉冲在腔内的动力学过程的影响。模拟结果表明,在腔内净色散值为负时,啁啾布拉格光纤光栅与增益光纤间的单模光纤越短,光纤激光器维持稳定单脉冲运行的最大泵浦强度更高且输出光谱更宽,从而能够获得脉宽更窄的去啁啾脉冲;腔内净色散值越接近零时,啁啾布拉格光纤光栅与增益光纤间的单模光纤长度对输出脉冲参数作用的影响越显著;腔内净色散值为正时,单模光纤在腔内的分布对输出脉冲影响逐渐减弱,优化单模光纤分布提升锁模激光器性能并不明显。最后,提出了一种通过改变单模光纤在腔内的分布来提高激光器输出性能的优化方法。     

Single-longitudinal-mode fiber ring laser employing an equivalent phase-shifted fiber Bragg grating

A novel single-longitudinal-mode (SLM) fiber ring laser that incorporates an equivalent phase-shifted fiber Bragg grating acting as an ultra-narrow bandpass filter in the laser cavity is proposed. The equivalent phase-shifted fiber Bragg grating has an ultra-narrow transmission bandwidth which ensures an SLM lasing. Stable SLM operation without mode hopping is demonstrated.     

Threshold of a Symmetrically Pumped Distributed Feedback Fiber Laser With a Variable Phase Shift

In this paper, we study, both theoretically and experimentally, the threshold characteristics of a distributed feedback fiber laser that depend on the value of a phase shift introduced into the fiber Bragg grating structure. We show that as the phase shift possesses a noticeable birefringence, the laser oscillates at any phase shift value. We also reveal that the laser threshold is different for the cavity eigen polarizations and depends on the phase shift value. We derive a simple analytical formula to calculate the laser threshold in the case of pi phase shift; this formula can be utilized to estimate a minimal threshold value for the laser with certain active fiber and Bragg grating parameters. The developed theory allows us to fairly model the experimentally measured dependence of the laser threshold on induced phase shift value.