可调谐纳秒脉冲锁模光纤激光器

采用非线性放大环形镜的被动锁模机制,通过加入手动可调滤波器及光纤光栅等实现单波长光谱输出,设计出一种可调谐纳秒脉冲光纤激光器.纳秒矩形脉冲由被动锁模掺铒光纤激光器产生,激光器的腔长为430 m,脉冲的重复频率为465 kHz.被动锁模光纤激光器中实现可调谐脉冲输出的关键器件包括宽带锁模器件和可调谐滤波器,其中宽带锁模器...     

2 μm可调谐高重复频率主动锁模光纤激光器

本文报道了一种2 μm波段可调谐主动锁模光纤激光器,增益介质为4 m铥钬共掺光纤。主动锁模脉冲采用强度调制方式实现,调制信号为高频正弦信号。可调谐窄带宽光滤波器用来窄化激光线宽,抑制噪声,同时可实现波长调谐。实现了稳定的2.2 GHz重复频率主动锁模脉冲输出,对应649阶谐波锁模脉冲序列,脉冲宽度约为200 ps,频谱信噪比可达68 dB,激光线宽为0.05 nm,光谱调谐范围为1907 nm~1927 nm。     

宽可调谐SG-DBR激光器波长测试控制系统

采用传统设备结合虚拟仪器的方法,研制了一套宽可调谐取样光栅DBR(SampledGratingDBR,SG-DBR)激光器的波长测试控制系统。系统能自动向SG-DBR激光器提供电流扫描,同时对激光器输出的光谱数据进行采集、处理,生成SG-DBR激光器的“波长-电流”数据查询表;通过快速查找数据查询表数据,并对激光器提供相应驱动电流,准确控制SG-DBR激光器输出波长。系统数据处理采用了一种新颖的算法,利用输出光边模抑制比(SMSR)来筛选激光器模式稳定工作点,确保数据查询表中的工作点数据均不会发生模式跳变。实验证明,本系统稳定、可靠,波长控制精度高,波长控制误差不超过±0.02nm。     

温度调谐掺Yb3+ 双包层光纤激光器研究

实验研究了掺Yb^3＋双包层光纤激光器的温度调谐特性。当光纤的温度从13℃变化到95℃时,输出激光的中心波长从1084．9nm增加到1096．3nm,输出激光功率从0．95W减小到0．58W。波长的调谐范围为11．4nm。理论分析表明,当光纤的温度升高时,高于零点的增益范围向长波方向移动,同时增益呈下降趋势。理论分析可以很好地解释实验现象。     

室温准连续多量子阱二极管激光器调谐特性

为了将应变补偿多量子阱（SC-MQW）激光器用于调谐激光吸收光谱（TDLAS）技术进行气体分子检测,研究了SC-MQW激光器在室温、准连续工作模式下的调谐特性.从半导体激光器的速率方程出发,分析了SC-MQW激光器输出波长与温度和注入电流的关系;使用傅里叶变换红外光谱仪（FT-IR）测量了激光器分别在不同电流、温度条件下的调谐特性,得到SC-MQW激光器在允许工作电流范围内的调谐范围接近20nm,电流调谐率约为0.03nm/mA;温度调谐率约为0.25nm/℃;电流和温度联合调谐的波长覆盖范围达50nm.结果表明,该激光器在带状吸收谱的挥发性有机物气体检测方面有很好的应用前景.     

短腔的高浓度掺铒光纤激光器

本文提出采用高浓度掺铒光纤的短腔环形光纤激光器,研制出铋铝共掺和铋镓铝共掺两种石英基高浓度掺铒光纤,这两种掺铒光纤的吸收系数在1530 nm处分别达到了66.3dB/m和59.5dB/m.利用这两种石英基高浓度掺铒光纤,采用环形结构制作出了短腔的光纤激光器,光纤激光器中铒光纤长度分别仅为30 cm和90 cm.对采用这两种高浓度掺铒光纤制作的光纤激光器的输出特性进行了测试和分析.实验结果表明,采用铋镓铝共掺的掺铒光纤制作的光纤激光器具有更高的输出功率和斜率效率,在980 nm泵浦源输出功率330 mW时可以实现15 dBm的激光输出,激光器的斜率效率达到了22%.     

DFB激光器调谐过程的动态线宽特性

为了获取分布反馈(DFB)激光器在调谐过程的动态线宽特性,提出一种基于光纤延时自外差的激光动态线宽测量方法,对于激光器线宽和测量原理做了理论分析.对商品化DFB激光器的实验结果表明:在整个电流工作范围内,激光动态线宽为20.38～4.73 MHz;工作电流为最大电流的0.58～0.66倍时,激光器的动态线宽最窄,激光器动态线宽最佳工作电流为最大电流的0.5～0.8倍.     

一种低偏振可调谐光滤波器的优化设计

光通信系统要求可调谐光滤波器(TOF)隔离度高,偏振敏感性低,目前基于角度调谐滤光片技术的TOF很难满足这一要求.通过膜系仿真分析了此类TOF透射谱劣化的原因.针对不同偏振态的光束在倾斜入射时中心波长及带宽分离现象,提出一种对称反转光路对TOF透射谱进行优化,可在整个透射范围内(C波段)将TOF的隔离度提高到30dB以...     

基于模式耦合器的锁模掺镱光纤激光器

本文提出了一种可以实现光纤高阶模式(HOM)在激光腔内振荡的锁模掺镱光纤激光器。通过使用一对级联的模式选择耦合器(MSC)作为有效的模式转换器,获得光纤锁模激光腔内HOM产生。其中,制备的MSC中心波长为1064 nm,可实现80 nm的模式转换带宽和94%的高阶模式纯度。通过搭建掺镱锁模光纤激光器,实验获得了3 dB谱宽7.4 nm、脉冲重复频率10.9 MHz、射频信噪比55 dB的锁模脉冲激光,输出功率的斜率效率为2.3%。实验证明,这种方法可在激光器内部通过模式级联转换,且能参与腔内锁模过程获得脉冲HOM激光。     

光纤光棚温度调谐特性分析与实验

提出了均匀调制光纤光栅的热调谐数学模型,确定了储热与布拉格波长之间的数学关系,分析光纤光栅热敏度,计算出热调谐的响应时间.设计和建立了一套光纤光栅温度调谐实验装置,利用光谱分析仪测试出光纤光栅反射波长漂移量受温度变化的关系曲线.测试了0-100℃的温度变化过程中光纤光栅反射波中心波长调谐量,测得光纤光栅反射中心波长λB为1546.8～1548.8nm,每摄氏度光纤光栅反射光波的中心波长平均漂移量为0.0210nm/℃.讨论了波长调谐量与温度的变化方向的关系和调谐响应速度等问题.实验结果表明光纤光栅反射波长漂移量与温度具有比较好的线性关系,且与温度的变化方向无关.     

A long cavity passive mode-locking fibre laser with the reflective non-linear optical loop mirror

In this paper, we report a long cavity passively mode-locked fibre laser. The proposed mode locker is a reflective long cavity non-linear optical loop mirror (NOLM) which consists of a 50:50 coupler and 2-km single-mode fibres. The laser achieves stable mode locking at a fundamental repetition rate of 100 kHz. The rectangular pulses operating in dissipative soliton resonance region is generated in the laser. The relationship between the pulse duration and the pump power is investigated in detail. When the pump power is 200 mW, the laser generates rectangular pulses at 1565.57 nm (central wavelength) with pulse duration of 81.5 ns. The single pulse energy as high as 33.34 nJ is obtained. The results show that the reflective NOLM is an efficient mode locker and useful for the generation of high energy pulse.     

Wavelength switchable L-band erbium-doped fiber laser employing C-band EDFA as gain medium

A new structure for the L-band multiwavelength switchable erbium-doped fiber laser is proposed. Overlapping laser cavities are formed by cascading fiber Bragg gratings as reflectors in a ring structure with a C-band EDFA as a common gain medium. The proposed laser is made to be wavelength-switchable by individually adjusting the loss of each overlapping cavity. Instead of using an L-band EDFA as the gain medium in the L-band fiber laser, we have experimentally demonstrated that by tailoring the gain of the C-band EDFA to have a significant gain tilt in the L-band, a lasing power efficiency of 26% can be achieved over a wide range of switchable lasing wavelengths. Following this optimal design, the side-mode suppression ratio and the minimal separation between two switchable lasing wavelengths were found to be over 42 dB and 0.33 nm, respectively.     

基于光纤耦合的光纤激光阵列像差探测

提出了一种基于光纤耦合的光纤激光阵列像差探测方法,介绍了其结构和波前复原过程,采用数值仿真模拟其复原湍流像差的过程,并进行了7单元自适应光纤准直器(AFOC)阵列复原静态像差的实验。仿真结果表明,本文提出的波前传感方法能够有效复原出湍流畸变波前,且对于不同单元数的六边形排布阵列,存在不同的最优复原阶数。阵列填充因子的降低会增大复原残差,填充因子大于0.8可保证复原残差RMS相较于填充因子为1时的增幅不超过10%。实验结果表明,利用填充因子为0.875的7单元AFOC阵列,复原以离焦为主的低阶像差时,初始畸变波前RMS为0.433 μm,复原残差小于0.075 μm。仿真和实验结果验证了本文提出的基于光纤耦合的光纤激光阵列像差探测方法的有效性。该技术有望在激光阵列大气传输及湍流校正等系统中得到进一步应用。     

Switchable and tunable multiple-channel erbium-doped fiber laser using graphene-polymer nanocomposite and asymmetric two-stage fiber Sagnac loop filter

A high-performance multiple-channel erbium-doped fiber laser (EDFL) is proposed and experimentally demonstrated, using graphene-polymer nanocomposite as a multiwavelength equalizer and an asymmetric two-stage polarization-maintaining fiber (PMF) Sagnac loop as a flexible comb filter. At first, the filtering characteristics of the PMF Sagnac loop filter (SLF) are investigated. Both theoretical and experimental results show that it can provide a flexibly switchable and tunable comblike filtering. Then, the two-stage PMF SLF is inserted into a graphene-assisted EDFL cavity for generating multiwavelength oscillation. The extreme-high third-order optical nonlinearity of graphene is exploited to suppress the mode competition of the EDFL, and a stable multiple-channel lasing is observed. By carefully adjusting the polarization controllers in the two-stage PMF SLF, not only can the lasing-line number per channel be switchable between single and multiple wavelengths, but also the wavelength spacing in the triple-wavelength condition can be tunable. In the case of triple wavelengths per channel, up to 12 wavelengths with four channels stable oscillations can be achieved. The multiple-channel EDFL can keep a high extinction ratio of >40 dB and a narrow linewidth of <0.01 nm.     

Wideband tunable Q-switched fiber laser using graphene as a saturable absorber

An ultra-wide wavelength tuning range, which covers three different band regions consisting of the S-, C-, and L-bands, is proposed and demonstrated for a graphene-based Q-switched erbium-doped fiber laser using a tunable bandpass filter as the wavelength tuning and filtering mechanism. A 3?m length of erbium-doped fiber is used as the gain medium in a ring laser cavity configuration, with absorption coefficients of between 11 and 13 dB?m^?1 at 980?nm and about 18?dB?m^?1 at 1550?nm. The tuning range of the Q-switching pulses covers a wide wavelength range of 58?nm, which spans from 1512.5?nm to 1570.5?nm. In addition, the lasing and Q-switching thresholds are considerably low, with respective values of ～11.0?mW and ～18.4?mW. A repetition rate of 55.3?kHz is obtained at the maximum pump power of 100.4?mW, together with pulse width and pulse energy of 1.6?μs and 25.8?nJ, respectively.     

碳纤维复合材料空间反射镜制造技术研究进展

碳纤维复合材料(CFRP)具有比刚度高、热稳定性好,可设计性强等特点,成为轻量化反射镜制造的新型理想材料,特别适合大口径、高分辨率空间反射镜的制造。简单介绍空间光学反射镜的国内外研究应用的现状。根据反射镜的特点介绍了碳纤维复合材料的材料选择要求,以及国外常用碳纤维复合材料预浸料体系。碳纤维复合材料反射镜制造方法与传统光学材料反射镜的制造不同,一般采用高效、快速、制造成本低的复制工艺来实现。总结了碳纤维复合材料反射镜的复制工艺和反射镜复制精度的影响因素,影响因素包括复制模具、预浸料铺层、反射镜变形、纤维印痕现象、尺寸稳定性以及反射镜尺寸等,并对前五项影响因素提出相应的控制措施来减小影响程度。重点阐述了反射镜纤维印痕现象的成因和解决方法,以及控制尺寸稳定性的关键。     

CO2激光器虚共焦腔凸面镜失调的实验研究

高功率激光器工作时，由于谐振腔反射镜上的光强分布不均匀，会导致镜面温度不均匀，从而造成镜面的角向偏转，致使激光器光轴发生偏转，严重影响输出光束质量，甚至造成不出光。文中主要从实验研究了CO2激光器虚共焦腔凸面镜失调对激光器输出光束质量的影响，实验结果表明，当凸面镜失调角接近于由理论计算而得的失调临界角时，输出光斑约为半个圆环，与理论分析非常符合，当凸面镜失调角达到约为失调临界角的4．5倍时，完全停止振荡。     

多波长掺镱光纤激光器实验研究

为了产生室温下掺镱光纤激光器稳定的多波长激光振荡,采用两个光纤环镜作为线形腔掺镱光纤激光器的端镜,在其中一个环镜中熔接一段保偏光纤构成梳状滤波器,通过优化掺镱光纤长度和腔损耗,实现了室温下1060nm附近稳定的多波长振荡.实验结果表明,在室温下,掺镱光纤存在比较明显的非均匀加宽效应,从而使得激光器的振荡波长数随泵浦功率的增加而增加.     

Wavelength conversion based on FWM in a HNLF by using a tunable dual-wavelength erbium doped fibre laser source

In this paper, we propose and demonstrate a cost-effective wavelength converter utilising a highly nonlinear fibre (HNLF) and a tunable dual-wavelength fibre laser as the pump source. The proposed system uses only the pump source and a signal probe to generate a partially degenerate four-wave mixing (FWM) effect. An FWM conversion efficiency of ?12?dB is obtained at pump and signal powers at +13.3?dBm and +5 dBm, respectively, and it is predicted that a higher conversion efficiency is possible if a high power dual-wavelength fibre laser source is used.