光栅型可调谐掺铥连续光纤激光器研究进展

2 μm波长可调谐掺铥连续光纤激光器具有调谐范围宽、输出线宽窄和噪声低等特点,在激光雷达、遥感、光通信、光谱分析、环境监测及激光医疗等领域具有重要应用,近年来成为光纤激光技术领域的研究热点.文章首先介绍了可调谐光纤激光器中实现波长选择的各类光栅元件的基本结构及工作原理,涉及到的光栅元件主要包括闪耀光栅、体布拉格光栅和光纤光栅;其次重点阐述了基于光栅的可调谐掺铥连续光纤激光器在国内外的研究进展,最后对其未来的发展趋势做出展望.     

飞秒激光烧蚀玻璃基质金属薄膜直写衍射光栅

提出了一种新的制备光栅的方法,利用800 nm的飞秒激光扫描蒸镀在石英玻璃衬底表面的金薄膜,通过烧蚀金薄膜在衬底表面形成衍射光栅。用波长为532 nm的激光照射光栅,测量其一级衍射效率,测得的衍射效率最高为6.98%。通过改变激光扫描速度、激光功率、光栅周期等实验参数研究其对制备的光栅的一级衍射效率的影响,结果表明,降低激光扫描速度,减小光栅周期,或增加激光功率都能提高制备光栅的一级衍射效率。     

Reversible Diffraction Efficiency of Photochromic Polymer Gratings Related to Photoinduced Dimensional Changes

In this Full Paper, the possibility of reversibly changing the diffraction efficiency of gratings, fabricated by soft molding lithography on polymer films, containing photochromic molecules, is demonstrated. In particular, alternating UV and visible laser irradiation of the gratings causes the doped photochromic molecules to undergo transformations, which induce reversible dimensional changes to the samples. As a result, reversible changes are monitored in the intensity of the beams of a diode laser, transmitted and diffracted from the gratings. These changes affect the diffraction efficiency, which is increased upon irradiation with UV and decreased after irradiation with visible laser light. Such gratings are promising candidates for the fabrication of modern optical components such as optical switching devices.     

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。     

一步激光直写制作透射式相位光栅

利用一步激光直写灰阶光刻方法制作了具有连续浮雕结构的透射式相位光栅.原子力显微镜测量结果表明制作的透射式相位光栅具有连续外形轮廓、理想的周期和深度.飞秒激光实验系统测量的光栅的衍射效率结果表明:最大衍射角效率为66.8%、零级能量仅为入射光能量的3.3%,这在光限幅中有重要应用价值.     

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。     

液晶闪耀光栅波前相位测量方法

电控液晶光栅在卫星激光通信、激光雷达的光束指向应用中具有体积小、光束灵活可控的优势。而获取电控液晶光栅对光波前的相位调制分布则是评价液晶光栅性能的关键。提出液晶光栅调制波前相位的共轭移相干涉测量技术,通过实验对比验证了实测远场分布与近场相位计算远场分布的一致性,由此可实现由近场相位测量的光束指向控制新方法。     

紫外写入光纤Bragg光栅及其发展

把要评述了光纤光栅的理论背景、光纤的光敏性，对至今发展起来的几种主要光纤光栅紫外写入技术和chirp光栅生成技术进行了全面的评介，最后介绍了光纤光栅在激光和通信方面的一些重要应用。     

飞秒激光直写金属反射光栅的实验研究

提出了利用800 nm的飞秒激光在Ni金属表面直写反射型衍射光栅的新方法.研究了激光刻写速度、激光功率以及光栅周期等实验参数与直写出的反射光栅衍射效率的关系.在现有实验条件下,由50 fS激光脉冲单光束直写获得的Ni质金属反射光栅的一级衍射效率η为7.47%.     

Azimuthal mode discrimination in radially chirpedconcentric-circle-grating distributed feedback lasers

We report a theoretical investigation analyzing the threshold modes of a concentric-circle-grating (CCG) distributed feedback laser with a radially chirped first-order Bragg grating. A numerical coupled-mode analysis of a chirped CCG laser shows improved azimuthal mode discrimination for chirped gratings with linear, quadratic, and square-root radial dependence. Negatively chirped gratings, in which the grating period decreases with radius, result in improved threshold discrimination between the circularly symmetric fundamental mode and higher order modes; positively chirped gratings, in which the grating period increases with radius, result in decreased threshold for higher order modes in general. Also, the intensity for the fundamental mode at the grating center can be reduced by an order of magnitude using linearly chirped gratings     

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     

双波长可调谐TEA CO2激光器的脉冲输出特性

为了获得两束波长不同的可调谐CO2激光脉冲,采用了双光栅与输出镜构成双谐振腔的结构没计。实验中,对影响激光器脉冲输出能量和调谐范围的参量作了具体分析。结果表明,两个谐振腔可以独立振荡输出不同波长的两束激光,二者之间不存在竞争影响,并且均可在大范围内调谐输出;通过对两个光栅做小幅度失谐调整,可以实现两束激光脉冲同步输出。     

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。     

Finite Beams in Reflective Volume Bragg Gratings: Theory and Experiments

We present a theoretical model to describe finite beams incident on reflective volume Bragg gratings. We also give experimental results that verify our model. From these results, we identify certain properties of reflective volume Bragg gratings, such as beam waist, incidence angle and beam profile, that have direct impact on the design of laser cavities that include such gratings. We also show how these gratings can act as spatial mode filters.     

A distributed feedback ridge waveguide quantum well heterostructurelaser

A method for incorporating distributed feedback in a ridge waveguide laser by means of lateral gratings and a single growth step is discussed. The necessary Bragg condition for distributed feedback is satisfied by etching gratings along the ridge in the top confining layer of the laser on either side of the contact stripe. Both Fabry-Periot modes and a single emission peak away from the peak of the gain profile are observed in lasers with cleaved facets. The Bragg reflection emission peak does not shift with increasing drive current, which is characteristic of a distributed-feedback (DFB) laser     

光纤光栅在高功率连续光纤激光器中的发展及展望

目前光纤光栅在高功率连续光纤激光器中的应用主要有两个方面,一是作为谐振腔腔镜,二是用来抑制激光器的非线性效应。首先论述了光纤光栅作为腔镜技术的发展现状,然后着重论述了能够抑制光纤激光器中非线性效应的特殊光纤光栅的发展状况。并详细描述了倾斜布拉格光纤光栅抑制受激拉曼散射和受激布里渊散射、长周期光纤光栅抑制受激拉曼散射以及相移长周期光纤光栅抑制自相位调制或四波混频等非线性效应引起的光谱展宽的研究进展。最后展望了光纤光栅在高功率光纤激光器领域的发展趋势,认为光纤光栅将朝着更高承载功率与长波长方向发展,同时认为基于飞秒激光刻写的光纤光栅技术、能够同时抑制多种非线性效应的光纤光栅技术、以及基于光纤光栅的光纤激光器激光偏振控制技术等将成为新的研究热点。     

飞秒激光加工微光学元件的研究

利用低功率飞秒激光振荡器进行材料表面加工的研究并将其应用于微光学元件的加工制作领域;对飞秒激光倍频光以及飞秒激光与光刻胶材料相互作用进行了实验;以光刻胶作为牺牲层进行表面加工获得了各种玻璃光栅及光掩模板;利用光学显微镜和原子力显微镜(AFM)对实验结果进行检测,得到微米量级的特征线宽;所得光栅的光学性能通过He-Ne激光器进行检测,实验结果与理论值一致。该研究为微光学元件的加工制作提供了新的方法。     

Short multiwavelength fiber laser made of a large-band distributed Fabry-Pe/spl acute/rot structure

Multiwavelength fiber lasers are obtained by writing two superimposed chirped fiber Bragg gratings in a photosensitive Er/sup 3+/--Yb/sup 3+/ codoped optical fiber. The chirped gratings create a distributed Fabry-Pe/spl acute/rot structure in which the resonating fields of the different laser lines are spatially separated, thus, reducing cross-gain modulation. We demonstrate multiwavelength lasers emitting simultaneously over 8 and 16 lines spaced by 50 GHz. The active structure is very compact having a total active length of 8 cm. We discuss how the properties of the device are governed by the parameters of the chirped gratings giving high flexibility in the laser design.     

具有时间同步性的双脉冲TEA CO2激光器实验研究

设计了一种新型双波长TEA CO2激光器,该激光器由两个空间上部分重叠的光栅和一个锗镜构成光栅-平面腔,两光栅一前一后放置,相互利用,共同建立双频振荡,由锗镜输出频率不同的双波长激光.输出双脉冲不仅具有一定的空间重叠性,而且具有一定的时间同步性.文章在简述激光器结构的基础上,重点介绍了对输出双脉冲的时间同步性的研究.