High-power double-clad large-mode-area photonic crystal fiber laser

A high power double-clad ytterbium-doped large-mode-area photonic crystal fiber (LMA PCF) laser was demonstrated using a unique Fabry-Perot (F-P) configuration. The pump source is a fiber coupled diode array operating at 976 nm. A continuous wave (CW) output power of 50 W at ～ 1.04 μm with a slope efficiency of 76.3% is obtained. Single transverse mode operation is achieved without any thermal-optical problems. This laser has the potential for scaling to much higher output power.     

大模场面积光子晶体光纤耗散孤子锁模激光器

研制了一种基于掺Yb3+的双包层大模场面积偏振光子晶体光纤的耗散孤子锁模激光器.利用数值模拟分析了光纤激光器中耗散孤子动力学过程,与全正色散锁模激光器相比,脉冲窄化机理更加丰富,半导体可饱和吸收镜(SESAM)的非线性吸收,啁啾脉冲的光谱滤波以及光纤的增益色散同时起作用,这些因素使耗散孤子锁模更加容易实现,并且稳定运行.其中,光谱滤波的耗散过程是稳定锁模机制的主导因素,滤波片能够在频域和时域同时窄化脉冲,并且去除脉冲啁啾,限制脉冲在腔内始终小于1ps.在实验上实现了无色散补偿腔中直接输出脉冲宽度777fs,最高平均功率达到1W,重复频率48·27MHz,对应单脉冲能量20nJ的飞秒激光.     

新型抗弯曲大模场面积光子晶体光纤

研制出一种新型抗弯曲大模场面积石英光子晶体光纤. 利用光子晶体光纤结构设计的灵活性, 通过规划缺陷的位置及空气孔的尺寸, 实现了大模场面积单模及低弯曲损耗特性.应用建立的实际光子晶体光纤特性分析模型, 研究了研制光纤的模式特性和弯曲特性, 在波长1064 nm处, 平直状态下光纤的模场面积可以达到2812 μm², 基模限制损耗为0.00024 dB/m, 高阶模限制损耗高于1.248 dB/m. 基模和高阶模之间的高传输损耗差, 保证了在获得大模场面积的同时实现单模传输. 弯曲半径和弯曲方向角所带来弯曲损耗变化的研究结果显示, 即使在弯曲半径小到5 cm时, 弯曲损耗也在10^-3 dB/m量级以下, 而且在弯曲半径为30 cm时光纤可承受的弯曲方向角范围扩展至-60°–60°. 研制的光纤具有良好的低弯曲损耗特性, 可有效解决非对称结构所带来的光纤弯曲特性对弯曲方向角敏感的问题. 该光纤在高功率光纤激光器、放大器及高功率传输等技术领域具有重要的应用价值. 关键词： 光子晶体光纤 大模场面积 低弯曲损耗 弯曲方向角     

自由耦合输出的大模场面积光子晶体光纤锁模激光器

对一种基于高增益掺Yb³⁺大模场面积光子晶体光纤（PCF）的锁模激光器进行了简化线型腔结构的实验和理论研究.实验中直接使用塌陷打磨为0°角的光纤端面作为一端腔镜,利用其端面反馈获得了激光振荡,并进一步利用半导体可饱和吸收镜（SESAM）和光栅对的滤波作用实现了稳定的锁模运转.通过调节滤波程度,使激光器实现了从宽带滤波锁模到窄带滤波锁模的连续可调谐.在宽带滤波锁模的条件下,得到了最大平均输出功率2.2 W,单脉冲能量29.3 nJ,脉冲宽度367 fs的锁模脉冲输出;在窄带滤波锁模的条 关键词： 飞秒激光 光纤激光器 光子晶体光纤 大模场面积光纤     

High power single-mode large-mode-area photonic crystal fiber laser with improved Fabry-Perot cavity

An Yb3+-doped double-clad large-mode-area photonic crystal fiber (LMA PCF) laser with 103-W single mode continuous-wave output power is demonstrated using an improved Fabry-Perot (F-P) configuration.The slope efficiency of 83.2% and good beam quality (M2 = 1.2 ± 0.1) are achieved without any thermo optical problems,dichroic mirror surface damage,and drop of the slope efficiency in this system.     

双包层大模场面积保偏掺镱光子晶体光纤研究

采用改进的化学气相沉积法和溶液掺杂法制备出掺镱石英光纤预制棒,以该预制棒为有源纤芯制备芯区直径约为30μm的双包层保偏掺镱光子晶体光纤.模拟计算得到该保偏光纤的模场面积约232μm2,双折射系数B为5×10-5.利用该光纤分别进行了脉冲激光和连续激光的放大测试实验,在国内首次实现了高效率的飞秒激光放大,2 m长的光子晶体光纤可得到1.64 W的激光输出,激光放大斜率效率为49.8%.同时5 m长的光纤还能够实现8.12 W的连续激光放大输出,斜率效率达到55.9%,具有较高的斜率效率.此外,该光纤消光比约10 dB,具有良好的保偏特性.     

20 W all fiber supercontinuum generation from picosecond MOPA pumped photonic crystal fiber

An all fiber high power supercontinuum (SC) source is demonstrated by pumping a section of photonic crystal fiber (PCF) with a picosecond MOPA laser. The core of the PCF is enlarged at the input end through a serious of PCF post processing method to match the output fiber of the picosecond laser, to ensure low loss splicing, hence high power operation of the whole system. The supercontinuum output spectrum covers the wavelength range from 650 nm to beyond 1700 nm. Limited by available pump power, 20 W super-continuum output power is obtained under 29.5 W picosecond pump power, giving a high optical to optical conversion efficiency of 67.8%.     

空气包层大模场面积掺镱光子晶体光纤研究

采用改进的化学气相沉积法和气相液相混合掺杂技术制备大芯径掺镱石英光纤预制棒, 以此作为有源纤芯制备了纤芯直径约90 μm的掺镱双包层光子晶体光纤, 纤芯组分为镱铝磷共掺.双包层光子晶体光纤的模场面积约1330 μm², 纤芯数值孔径0.065,包层数值孔径0.5.首次实现了国产掺镱光子晶体光纤的高功率高效率激光输出, 1 m长的光子晶体光纤激光器实现102 W 激光输出,斜率效率76%.     

High pulse energy mode-locked multicore photonic crystal fiber laser

A high pulse energy passively mode-locked fiber laser operating in the all-normal dispersion regime is demonstrated. The gain material is an Yb-doped multicore photonic crystal fiber with 18 cores in array-type geometry. Robust and self-starting mode locking is achieved using a fast semiconductor saturable absorber mirror. The laser generates 180?nJ chirped pulses at a 14.48?MHz repetition rate for an average power of 2.6?W. The 1.15?ps output pulses are compressed to 690?fs outside the cavity.     

新型三角芯抗弯曲大模场面积光子晶体光纤

提出了一种新型三角芯抗弯曲大模场面积光子晶体光纤.该结构采用单一尺寸的圆形空气孔, 降低了制作难度.在波长1.064 μm处, 在平直状态和弯曲半径为30 cm时, 模场面积分别为1386 μm²和1153 μm², 弯曲带来的模场面积减少量仅为16.85%. 当弯曲半径为30 cm时, 基模的损耗为0.087 dB/m, 二阶模的损耗大于1.5 dB/m, 大的损耗差有效保证了光纤单模运转.此外, 弯曲半径30 cm时, 弯曲方向角扩展至±180°, 光纤弯曲不再受弯曲方向的限制. 所设计的光纤结构具有大模场面积、小的模场面积减少量、 低的弯曲损耗以及低的弯曲方向敏感度等优势, 为小型化、集成化高功率激光传输及光纤激光器和放大器的研究奠定了基础. 关键词： 光子晶体光纤 大模场面积 抗弯曲 弯曲方向角     

大模场面积光纤激光器79.4 W单横模输出

 采用光纤缠绕方法,对国产大模场面积多模光纤激光器缠绕前后的输出性能进行了对比研究。将光纤激光器输出端在半径为65 mm的圆筒上缠绕两圈后,获得了单横模输出。光纤缠绕前后,激光器的光束质量因子由1.24减小为1.06,斜率效率由64.7％减小为54.3％。当泵浦功率为149 W时,缠绕前后的输出功率分别为94.7 W和79.4 W。虽然缠绕后功率有所减小,但激光亮度增加了15％。同时对实验所用光纤的缠绕损耗进行了理论计算,实验结果与理论计算值符合得较好。     

亚百飞秒高功率掺镱大模面积光子晶体光纤飞秒激光放大器的实验研究

实验研究了掺镱双包层保偏大模面积光子晶体光纤飞秒激光放大器. 获得了平均功率达16W的飞秒激光放大输出,在50MHz重复频率下,对应的单脉冲能量达到320nJ. 增益光纤长3.5m,由于自相位调制效应,种子光脉冲光谱在放大过程中同时展宽,从而支持更窄的脉冲宽度. 经过光栅后,脉冲宽度压缩到了85fs. 系统中的振荡器和放大器基于同一种具有偏振结构的大模面积光子晶体光纤,具有很好的环境稳定性和进一步集成的可能. 关键词： 光子晶体光纤 大模场面积光纤 飞秒激光 光纤放大器     

100W高光束质量光子晶体光纤棒皮秒脉冲放大器

使用光子晶体光纤棒作为增益介质,设计了皮秒脉冲放大器的实验光路。通过实验研究分析了光子晶体光纤棒皮秒脉冲放大器的输出功率、斜率效率与光光转换效率、光束质量、重复频率、脉宽、光谱。获得了最大平均功率为101.7 W,重复频率为30 MHz,脉宽为6.4 ps,横向和纵向光束质量分别为1.111,1.017的近衍射极限输出,放大器的斜率效率达到了65%,光光转换效率达到了58.9%。     

大模场面积光纤激光器79.4 W单横模输出

采用光纤缠绕方法,对国产大模场面积多模光纤激光器缠绕前后的输出性能进行了对比研究。将光纤激光器输出端在半径为65 mm的圆筒上缠绕两圈后,获得了单横模输出。光纤缠绕前后,激光器的光束质量因子由1.24减小为1.06,斜率效率由64.7％减小为54.3％。当泵浦功率为149 W时,缠绕前后的输出功率分别为94.7 W和79.4 W。虽然缠绕后功率有所减小,但激光亮度增加了15％。同时对实验所用光纤的缠绕损耗进行了理论计算,实验结果与理论计算值符合得较好。     

Wavelength tunable,high energy femtosecond laser pulses directly generated from large-mode-area photonic crystal fiber

Wavelength tunable high energy ultrashort laser pulses are generated from a large-mode-area photonic crystal fiber in anomalous dispersion (AD) regime. A simplified laser cavity design with one fine polished facet of the fiber as a cavity mirror is used. The intra-cavity dispersion compensation is achieved by a grating pair, the spatial dispersed light from which also have optical spectrum filtering effects combined with the limited aperture of the fiber core. The laser system is able to generate ultrashort pulses ranging from 494 fs (with 56 nJ pulse energy) to 1.24 ps (with 49 nJ pulse energy) at 55 MHz repetition rate. The filtering mechanism benefits the generation of high energy pulses with narrowing pulse duration in AD regime. An undulation in frequency and time domain is also observed with the increase of the pump power. Furthermore, this laser system is directly used as seed for supercontinuum generation.     

高能量掺Yb偏振型大模场面积光子晶体光纤孤子锁模飞秒激光器

实验研究了基于掺Yb偏振型大模场面积光子晶体光纤的孤子锁模激光器,获得了高脉冲能量的飞秒激光输出. 激光器基于线形腔结构,利用光栅对补偿腔内色散,并通过半导体可饱和吸收镜实现锁模的自启动. 实验中从振荡级直接获得了平均功率为700mW, 重复频率为47.3MHz(对应于14.8 nJ的单脉冲能量),脉冲宽度为518 fs的稳定锁模脉冲输出. 与普通孤子锁模飞秒光纤激光器相比,输出的单脉冲能量提高了两个数量级. 关键词： 光子晶体光纤 飞秒 光纤激光器 孤子锁模     

Phase stabilization of a large-mode-area ytterbium-doped fiber amplifier

Measurements are reported on the open and closed-loop phase stability of a large-mode-area ytterbium-doped fiber amplifier. Phase fluctuations are characterized by a high-frequency low-amplitude jitter superimposed on a slow power-dependent drift. The amplifier may be phase locked to a precision of lambda/20 by using a low-bandwidth feedback loop.     

Deep-notch, ultracompact long-period grating in a large-mode-area photonic crystal fiber

An extremely short long-period grating (LPG) with strong resonance has been developed in a large-mode-area photonic crystal fiber (PCF) by use of the heat source of a CO2 laser. We believe that such a LPG in pure silica PCF is the first example to be obtained with the point-by-point technique. The fabrication method is simple and repeatable. The resulting LPG has 8 periods, written by a CO2 laser, within a 2.8-mm length of fiber, which yields a deep notch of core-cladding mode coupling of -31.5 dB at the telecommunication wavelength of 1529.2 nm, with a FWHM of approximately 0.7 nm. The principal advantages of this LPG are that it is practical, cost effective, and compact.     

Visible supercontinuum generation in tapered photonic crystal fiber pumped by picosecond pulse at 1064 nm

Short photonic crystal fibers (PCFs) with different tapered waist diameter are made to extend the continuum spectrum in the visible range. The diversification of output continuum spectrum with the diameter of the tapered waist is experimentally observed. An all fiber visible supercontinuum source with 1.88 W output is demonstrated in our experiments. To the best of our knowledge, it is the highest all fiber visible supercontinuum generation in tapered PCF, pumping by picosecond pulse at 1064 nm. The suitably designed short tapered PCF can extend the visible spectrum, while, how to preserve the tapered waist is crucial for the all fiber visible supercontinuum source in the practical applications.     

Q-switched thulium-doped photonic crystal fiber laser

We report a novel, Tm-doped photonic crystal fiber (PCF) actively Q-switched oscillator that provides ~8.9 kW peak power with 435 μJ, 49 ns pulses at 10 kHz repetition rate at 2 μm wavelength. This fiber has a mode-field area >1000 μm2, the largest of any flexible PCF providing diffraction-limited beam quality to the best of our knowledge. As an application, the oscillator is used as pump to generate >350 nm broadening in ~50 m of SMF-28 fiber.