基于环腔内光学缓存装置的高速扫频激光光源

傅里叶域锁模(FDML)技术可在保持扫频光源各项指标性能优越的前提下,将扫频速度提高至调谐滤波器的设计极限。为进一步提升FDML扫频激光光源的扫频速度,在激光谐振腔内引入光学缓存装置来实现对扫频光的备份。实验中基于环腔内光学缓存装置的扫频光源中心波长为1310nm,扫频范围为95nm,瞬时线宽为0.1nm,扫频速度翻倍提升至202kHz,平均输出光功率为7.5mW。利用光学缓存装置可将传统FDML高速扫频光源的扫频速度翻倍提升,对提升扫频光学相干层析成像(SS-OCT)系统的综合成像性能具有重要意义。     

30kHz窄瞬时线宽扫频激光光源的研制

搭建了一个中心波长为1340 nm、扫频速度为30 k Hz的光纤型窄瞬时线宽扫频激光光源,光源相位和光强稳定性高,扫频范围为10 nm,半峰全宽为6 nm,瞬时线宽小于0.018 nm,输出平均光功率为9.1 m W。实验扫频激光光源在傅里叶域锁模技术的基础上,使用精密度为5578、窄透射窗口的法布里-珀罗滤波器(FFP-TF)作为调谐滤波器,以腔内增益介质的自发辐射为背景光,经过单模长光纤后,到达FFP-TF并对腔内的激光进行调谐滤波,最后稳定地输出窄瞬时线宽的扫频激光。讨论了影响光源瞬时线宽的因素。搭建的窄瞬时线宽扫频激光光源具有极高的精密度和稳定性,可直接应用于对分辨率要求比较高的高速分子光谱学、分子吸收光谱学等领域。     

基于傅里叶域模式锁定的扫频光源实验研究

扫频光源是光纤传感解调的关键部件,高质量的扫频光源可提高光纤传感系统的信噪比和解调精度。研制了一种基于傅里叶域模式锁定(FDML)的扫频光源。光源采用环形腔结构,由半导体光放大器(SOA)、光纤法布里-珀罗(FP)可调谐滤波器、隔离器、光纤耦合器和光纤延迟线组成。同时设计了基于FP腔的滤波器,对输出光谱进行平坦滤波。得到扫频范围为60 nm(1506~1566 nm),扫频速度为250 Hz,平坦度优于0.3 d B,线宽小于0.16 nm,平均输出光功率为4.53 m W的扫频光源。研制出的扫频光源结构简单、成本低廉、平坦度好,在光纤传感解调系统中作为光源有一定的实用价值。     

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。     

自制宽带光源及其在光纤光栅制作中的应用

在光纤光栅制作过程中,宽带光源经常被应用于在线监测光纤光栅的反射率,以便适时有效地控制生成的光栅的透射率的高低程度.利用中心波长为971nm的半导体激光器抽运一段Yb+掺杂双包层光纤,制作出了一个宽带超荧光光源,该光源在最大功率输出时谱宽达到了75nm,并在1085nm附近10nm范围内荧光谱的输出功率高,有较好的光谱平坦性.还利用该宽带光源作为光纤光栅制作的监控光源,制作出了单模和多模光纤布喇格光栅,取得了令人满意的实验结果.结果表明,该宽带光源完全可以适应监控光纤光栅制作的需要.     

激光二极管阵列的窄线宽、可调谐输出

外腔反馈的激光二极管阵列(LDA)可获得窄线宽、可调谐的光谱输出。外腔由快轴准直镜、准直光学系统和闪耀光栅组成。由于阵列中各发光单元的排列弯曲导致不同波长的光原路返回,引起谱线展宽,在输出光路中加入光谱滤波器,使激光二极管阵列的线宽进一步窄化。这样,激光二极管阵列的输出光谱由自由运转时的2 nm压缩到0.12 nm,在恒定温度23℃时,实现了激光在806～818 nm的调谐,调谐范围达12 nm。     

平坦功率输出的宽带波长可调光纤环型激光器

为了获得一种平坦功率输出的宽带波长可调的掺铒光纤环型激光器，提出采用一高双折射光纤环镜获得其平坦功率输出，在高双折射光纤环镜中，采用了大量的高双折射光纤段和偏振控制器，它们的反射光谱可补偿掺铒光纤环型激光器输出功率光谱的不平坦，通过压缩或者延伸激光腔里的分布式光纤布喇格光栅即可实现波长调谐。实验验证可以获得一种宽达38nm的宽带波长调谐(1527nm～1565nm)，输出功率的不平坦被控制在±0．8dB范围之内，总输出功率大约4dBm、3dB线宽为0．01nm、旁瓣抑制比为48dB的光纤环型激光器。     

可调谐全正色散掺镱光纤激光器

利用相位长周期光纤光栅作为光谱滤波器,熔接于全正色散掺镱光纤激光系统中,从而实现了具有波长可调谐的连续激光输出和被动锁模激光脉冲输出,可调谐激光波长范围分别为11.4 nm和10.5 nm.通过调节偏振片改变激光腔内的偏振状态,输出锁模脉冲实现脉冲宽度的可调谐,其调谐范围为3.6~1.2 ns.在530 mW的最大泵浦功率下,得到了重复频率为2.5 MHz、最大单脉冲能量为38.9 nJ的锁模脉冲输出和最大输出功率为124 mW的连续激光输出.     

倍频傅里叶域模式锁定扫频激光源

搭建完成了基于单偏振助推光学放大器的傅里叶域模式锁定扫频激光源,并在此基础上实现了倍频傅里叶域模式锁定扫频激光源,将光源的成像速度提高了一倍。该倍频激光源输出功率达到2mW左右,扫描频率为45kHz,输出光谱的中心波长为1 315nm,光谱宽度为107nm。利用该光源进行相干层析成像实验时,系统的A-Scan速率为90kHz,纵向分辨率为12.9μm左右,相干长度为0.9mm左右,灵敏度为105dB。     

双光栅外腔可调谐掺Yb3+双包层光纤激光器

采用一种新颖的双光栅装置作为外腔调谐结构 ,实现了掺Yb3+ 双包层光纤激光器的调谐输出 ,调谐范围10 37～ 110 6nm。双光栅结构的应用 ,使调谐输出的激光光谱的线宽大大变窄 ,小于 0 1nm。检偏器测量结果表明 ,整个调谐范围内的激光输出均为线偏振光。     

Continuous True-Time-Delay System Employing a Novel Tunable Chirped Fiber Grating Delay Line and a Sampled Grating Based Multiwavelength Fiber Laser

A photonics true-time-delay system for phased array antenna beam steering employing a novel tunable chirped fiber grating delay line and a multi-wavelength erbium-doped fiber ring laser source based on a sampled grating filter is proposed. The tunable chirped fiber grating, which act as a continuous time-delay element, is achieved by bending a uniform fiber Bragg grating bonded at a slant onto the lateral surface of a simply supported beam. This technique allows the dynamic control of the chirp rate and spectral width of the grating without center wavelength shift. By adjusting the chirp rate of the fiber grating via bend strain, this kind of tunable chirped fiber grating could achieve very low and adjustable delay times, therefore provides higher angle resolution for scanning microwave beam, even the wavelengths of laser source are fixed and un-tunable. The true-time-delay system using proposed tunable chirped fiber grating delay element and sampled grating based laser source is constructed and demonstrated experimentally.     

External Line-Cavity Wavelength-Swept Source at 850 nm for Optical Coherence Tomography

We constructed a novel and compact wavelength-swept laser source at the 850-nm region using an external line cavity in a modified Littman configuration filter. The angle alignment stability was improved by separating the function of output coupling and the wavelength selection of diffraction grating with gold coating. Our swept source produces laser output at the center wavelength of 849 nm and the average power of 2 mW with the full-width at half-maximum of 48 nm. The system performance is discussed and a two-dimensional image of a biological sample is presented     

分布式光纤光栅传感网络的复用解调技术

波长编码信号解调是实现光纤光栅多参量、多点分布式传感网络的核心技术之一。本文总结了光纤光栅传感信号解调的一般原理和技术难点,分类评述了常用解调方法的工作机理、特点和性能。同时,提出了一种新型的、用宽带光源和可调谐光滤波器(TOF)构成的可调谐窄带光源,对测量光栅阵列和参考光栅进行波长扫描,借助光电探测器和信号处理系统实现复用传感系统的解调技术。     

一种新型光纤光栅复用传感解调技术的研究

用宽带光源和可调谐光滤波器(TOF)构成可调谐窄带光源,对测量光纤光栅(FBGs)阵列和参考FBGr进行波长扫描,借助光电探测器和信号处理系统实现复用传感系统的解调。实验证明,该解调方案是有效可行的,且可获得较高的信噪比和测量精度,具有对40个以上FBGs传感网络进行寻址解调的潜在能力。     

单FBG双波长掺铒光纤激光器的设计与实验研究

为给密集波分复用(DWDM)光纤通信及光纤传感系统提供理想光源,设计了一种双波长环形腔掺铒光纤激光器。该激光器采用单支光纤光栅(FBG)和2个3dB耦合器构成可调谐光滤波器,结合多模光纤的偏振烧孔效应,通过改变系统的偏振态来获得波长可调谐的双波长激光输出。实验结果表明:改变系统的偏振态时,可分别获得单波长和双波长激光输出,双波长光纤激光器的最大波长差为4.692nm。引入多模光纤后,激光跳模现象得到明显抑制。     

A double-element broad-band liquid crystal tunable filter-factorsaffecting contrast ratio

A double-element broad-band liquid crystal tunable filter consisting of a high-order quartz wave plate in series with a very-low-order electrooptically tunable liquid crystal phase plate and placed between crossed polarizers is described. A possible application for such a device is protection against intrusive laser radiation. The advantage of this double-element filter over a single-element low-order LC filter is that it increases the wavelength resolution of the device, which, when operated in the protect mode, allows continued sensing of the scene. Experimental and theoretical studies were made of the contrast ratios obtainable with such a filter     

Tunable Fiber Laser Using a Broad-Band Fiber Mirror and a Tunable FBG as Laser-Cavity Ends

By using a broad-band fiber mirror (BFM) and a tunable fiber-Bragg-grating at either end of laser cavity, a wavelength tunable erbium-doped fiber laser is demonstrated. In a forward pump scheme using 100 mW pump power at 1480 nm, stable lasing output power of 21.14-mW measured at 1544.8 nm is obtained with a threshold pump power of 4.7 mW. A side-mode suppression ratio as high as 57.9 dB, wavelength tuning range up to 30 nm with step resolution of 0.2 nm and power variation less than plusmn1.0 dB are achieved. For a backward pump scheme, the BFM acts as a broad-band reflector both for the lasing signal and pump source. The high performance, cost-effective BFM based tunable fiber laser may play an important role in fiber optics communication and fiber sensing applications.     

Fiber Laser Thermally Tunable by a Filter Composed of Two Sagnac Interferometers

Many applications, such as fiber Bragg grating characterization, wavelength division multiplexing, etc. require tunable laser sources with one emission line in a certain wavelength range. Generally, such sources are laser systems combined with tunable filters. In this work an all-fiber laser tunable by a filter composed of two Sagnac interferometers in series is described. The filter loops were constructed of high birefringence fibers (HiBiFi) and the filter was thermally tunable with a single transmission maximum in the Erbium gain spectrum. The results showed that for interferometers with 14 cm HiBiFi length a bandwidth reduction of the transmission peak, a single-line laser emission, a tuning sensitivity of approx. -0.8 nm/degC and a spectral full-width at half-maximum bandwidth of 0.03 nm in the range of 1538-1580 nm were obtained.     

采用可调Mach-Zehnder滤波的波长可切换掺铒光纤激光器

为了实现高稳定性的可调谐激光输出,提出并设计了一种基于马赫-曾德（M-Z）结构和光纤光栅串结合的掺铒光纤激光器,在M-Z干涉结构的一个干涉臂中加入光学延迟线（ODL）,实现对干涉间隔的灵活可调。系统结构设计采用976 nm波长的LD作为泵浦源,长度为6 m的掺铒光纤作为增益介质;采用光栅串将特定波长的光反射回环形腔形成振荡;采用M-Z结构产生梳状滤波用来对光栅串反射回的光进行选择;通过调节ODL来改变腔内损耗,进而实现激光的可调谐输出,并通过在系统中加入可饱和吸收体（SA）和子腔结构来抑制波长的跳变。实验中,在泵浦功率为100 mW时,实现了单波长双波长和三波长的稳定的激光输出。单波长共输出13个,调谐范围为1 570~1 596 nm,调谐间隔为2 nm,边模抑制比均大于50 dB。