Tunable dual-mode operation in a chirped gratingdistributed-feedback laser

We report on the tunable dual-mode operation of a chirped grating distributed-feedback (DFB) laser device with two integrated modulators which act as tuning sections. A transfer-matrix model is used to simulate the amplified spontaneous emission spectrum for a chirped grating DFB laser. Several types of dual-mode operation are observed for wavelength spacings of 0.5 nm and 1.4 nm corresponding to frequency detunings of 63 GHz and 175 GHz     

Self-compensated dispersion tuning of a mode-locked fiber laserusing a linearly chirped fiber grating

A new approach of self-compensated dispersion tuning is developed to generate wavelength-tunable pulses from a fiber laser. A linearly chirped fiber grating is used in conjunction with a pair of optical circulators and modulators in the cavity. The wavelength has been electrically tuned while maintaining a constant operating frequency of 1 GHz. The laser exhibits a linear tuning relation with respect to the delay time between the electrical control signals. Three chirped gratings providing dispersions of 1446, 50, and 10 ps/nm are used respectively in the experiment and the results are compared. The highest tuning range is about 1 nm and is limited by the chirped bandwidth of the gratings     

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。     

基于CFG的连续TTD系统研究

提出并实验验证了一个四通道的基于啁啾光栅的连续可调光控延时系统,该系统适合于频率达10 GHz的相控阵天线的波束形成及扫描,使用一种基于啁啾光栅的延时网络和一种新型的波长等间隔增大或减小的多波长可调谐线性腔光纤激光器.光纤激光器的等波长间隔,通过相等增量的作用力挤压或拉伸激光谐振器中固定在一个有机塑料盘上成一定的角度相邻的布拉格光栅来调谐.光控延时是通过被调制光在一个线性啁啾光栅的不同位置反射而实现,波长等间隔激光可获得等间隔的延时.     

两节分布反馈激光器的性能

详细讨论了两节(两电极)分布反馈(DFB)激光器的重要特性,其中包括调谐理论、频率调制响应以及频率交换速率。两节DFB激光器的调谐机理可根据波导光栅反射特性的基本相位和幅度来解释。波长调谐由不均匀电流注入的纯电子效应所引起。激光器的调制带宽由有源区中受激载流子寿命所决定。在激光器红移和蓝移静态调谐状态下,FM响应和频率交换是不同的。对高速FSK调制,激光器应偏置于蓝移状态下工作。FM响应的大小和相位变化影响激光器的高速频率交换。     

Continuously tunable organic solid-state DFB laser utilizing molecular reorientation in molecular glasses

We report a facile way for continuously tuning the lasing wavelength of an organic thin-film distributed feedback (DFB) laser after device fabrication by varying the effective refractive index seen by the one-dimension DFB laser structure. Varying the effective refractive indices of the organic gain medium and thus the effective refractive index of a one-dimension DFB laser structure after device fabrication is made possible with reorientation of molecules in a molecular glass at elevated temperatures. Distributions of molecular orientations can be fine controlled by annealing temperatures and times, permitting continuous tuning of optical properties and lasing wavelengths. Molecular reorientation can be conducted after devices are made, thus giving one the freedom to set or tune the lasing wavelength to meet a particular purpose with a common structure.     

Time-resolving wavelength chirp with Fabry-Perot etalons andgratings: a theoretical approach

Basic dynamic properties of Fabry-Perot (FP) etalons and gratings are investigated for a square-wave shaped input pulse with a linearly changing wavelength. It is shown that for the chirp rates present in distributed feedback (DFB) laser pulses a simultaneous good resolution in the wavelength and time domain is attainable with an etalon due to its small FWHM time-bandwidth product of 0.11. This is not possible with the grating, which has a time∞bandwidth product of 0.89. A simulation of time resolving the dynamic chirp of a DFB laser pulse is presented. The result is compared to the actually calculated incident wavelength variation. The dynamic aspects of FP etalons and gratings for time resolving the wavelength chirp in laser pulses are given     

纳米压印制作半导体激光器的分布反馈光栅

分布反馈(DFB)光栅的制作是半导体激光器芯片的关键工艺,通过纳米压印技术在InP基片表面涂覆的光刻胶上压印出DFB光栅图形,并分别通过湿法腐蚀和干法刻蚀技术将光栅图形转移到InP基片上。所制作的DFB光栅周期为240nm(对应于1 550nm波长的DFB激光器),光栅中间具有λ/4相移结构。采用纳米压印技术制作的DFB光栅相对于通常双光束干涉法制作的光栅具有更好的均匀性以及更低的线条粗糙度,而且解决了双光束干涉法无法制作非均匀光栅的技术难题。相对于电子束直写光刻法,采用纳米压印技术制作DFB光栅具有快速与低成本的优势。采用纳米压印技术在InP基片上成功制作具有相移结构的DFB光栅,为进一步进行低成本高性能的半导体激光器芯片的制作奠定了良好基础。     

Control of lasing wavelength in distributed feedback lasers byangling the active stripe with respect to the grating

We proposed and demonstrated a new and very simple technique of varying the lasing wavelength of distributed feedback (DFB) lasers with the need for fabricating gratings with different pitches. This is accomplished by angling the active stripe at an oblique angle with respect to the axis of the grating lines. This technique should be particularly suitable for fine tuning of lasing wavelength, and it eases the stringent demand on precise control of absolute grating pitches. It should be useful and important for dense (wavelength division multiplexing (WDM) applications and monolithic integration of multi-wavelength DFB lasers     

Broad-band continuously tunable all-fiber DFB lasers

Up to 27-nm continuous tuning is demonstrated from Er/Yb all-fiber distributed-feedback (DFB) lasers using a simple tuning technique for axial extension and compression. The demonstrated devices operate with powers up to 10 dBm and remain operating in single mode over the full tuning range. Our results represents the broadest tuning-range previously reported in any DFB laser configuration and demonstrate that uniform compression tuning of long Bragg gratings is possible with high reliability     

Investigation of a tuneable mode-locked fiber laser for application to multipoint gas spectroscopy

This paper reports on an initial investigation into the operation of a mode-locked fiber laser system for application in gas spectroscopy as a multipoint multigas sensor. Wavelength selection is performed by use of multiple chirped gratings and fine tuning by using the dispersion properties of the chirped gratings. A tuning rate of /spl sim/0.014 nm per kHz change in mode-lock frequency (at the third harmonic) has been demonstrated, which is suitable for scanning across gas absorption lines. Key issues that have an important bearing on the tuning are discussed, including gain flattening and polarization drift. This paper investigates a method of multiplexing the sensor cells with the mode-locked system. Preliminary results for a two cavity system are presented to verify the principles of the technique.     

Chirped Bragg Grating Waveguides Directly Written Inside Fused Silica Glass With an Externally Modulated Ultrashort Fiber Laser

A modulated fiber laser provided burst-trains of femtosecond pulses to directly write linearly chirped Bragg grating waveguides inside bulk fused silica glass in a single process step. The results represent the first demonstration of chirped gratings embedded in bulk glass with an ultrafast laser. Simple exposure controls offer facile means for tuning spectral and dispersion responses in three-dimensional optical circuits.      

基于分布反馈激光器布里渊散射的高精度光谱测量

实现了一种基于光纤中受激布里渊散射(SBS)效应 的高分辨率光谱测量技术。使用连续可调谐分布反馈(DFB) 激光器作为泵浦光,与待测信号光在单模光纤(SMF)中发生受激布里渊放大相互作用,由此 实现对待测光的高分 辨率光谱测量与分析。DFB激光器的波长扫描通过高精度温度调谐来实现。与相关报道 中使用的外腔 可调谐激光器对比,DFB激光器具有体积小、成本低的优势。同时在波长扫描过程中,对DFB 激光器的输出光进行自 拍频处理获得其实时扫描速率,以此校正激光器的实时扫描波长,提高测量准确度。实验 初步验证了本文高分辨率光谱测量技术的可行性,并获得了0.24pm 的光谱分辨率。     

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。     

Wavelength trimming by photoabsorption-included disordering for multiple-wavelength distributed-feedback laser arrays

In this letter, we describe a simple method to adjust the oscillation wavelength of distributed-feedback (DFB) lasers after the device fabrication without using any external active tuning. The method utilizes a permanent change of refractive index in the quantum well active layer induced by external laser beam irradiation. We have demonstrated 0.36 nm adjustment in a 1.55-/spl mu/m ridge waveguide DFB laser.     

Study of wavelength shift in InGaAs/InAlGaAs QW DFB lasers based onlaser parameters from a comparison of experiment and theory

Experimental data of InGaAs/InAlGaAs quantum well distributed feedback (DFB) lasers such as spectra, under continuous and pulsed biasing, relative intensity noise and linewidth, are compared with the results of model calculations based on a transfer matrix method. Using experimental data of different lasers, a set of physical DFB laser parameters was determined. We succeeded in describing all the experimental data of different lasers by the same set. The determined parameter set was further applied to study the influence of facet properties on the wavelength shift of DFB lasers. We found a very strong dependence of the wavelength tunability on the end facet phases. The wavelength shift varies by a factor up to three between different end facet phases and coatings. This is crucial for the yield of, for example, tunable multisection DFB lasers with an envisaged large tuning range     

20-mW widely tunable laser module using DFB array and MEMS selection

The authors describe a novel configuration for a wavelength selectable laser that provides wide tuning and distributed-feedback (DFB) performance and reliability at a fundamentally low cost structure. The configuration consists of a DFB laser array and a micromechanical mirror that selects one element of the array. The MEMS tilt mirror also loosens the tolerances, since the fine optical alignment is done electronically. Only one laser is operated at a time, with coarse tuning realized by selecting the correct laser and fine tuning by adjusting the chip temperature. The 33-nm total tuning at 20-mW fiber coupled power is obtained in a fully functional module.     

Tuning and chirping fiber Bragg gratings by deep etching

We have demonstrated a new method for tuning and chirping fiber gratings. It relies on etching of a fiber down to very small cladding diameter, so that the propagating optical mode in the fiber interacts with the surrounding media. A tuning range of 4.5 nm has been demonstrated with a potential of much larger tuning range by optimization of fibers. Chirped gratings were also demonstrated with this technique. These chirped gratings are very important for use in fiber dispersion compensation and optical pulse shaping.     

Mode-Locking in a Semiconductor Fiber Laser Using Cross-Absorption Modulation in an Electroabsorption Modulator and Application to All-Optical Clock Recovery

We demonstrate the use of cross-absorption modulation in an electroabsorption modulator to actively mode-lock a semiconductor fiber laser at 10 GHz. The laser cavity also comprises a linearly chirped fiber Bragg grating to obtain wavelength tunable operation based on the dispersion tuning approach. The laser exhibits uniform output pulse characteristics throughout the tuning range. We also investigate the impact of using different types of optical pump signals on the output pulses. Finally, we demonstrate the application of the mode-locked laser for all-optical clock recovery.