A High‐Efficiency All‐Fiber Laser Operated in High‐Order Mode using Ring‐Core Yb‐Doped Fiber

An all‐fiber laser generating a cylindrical vector beam is proposed and demonstrated using a home‐made ring‐core Yb‐doped fiber (RC‐YDF). In the RC‐YDF, not only annular doping but also ring‐type beam pump is realized. This is believed to be the first report describing the realization of annular doping and ring‐type beam pump in active fiber simultaneously, which can enhance the efficiency for high‐order mode oscillation. This laser operates in the high‐order mode stably with a slope efficiency of as high as 55.7%. Cylindrical vector modes can be obtained easily through adjusting the polarization controller. This work may have great potential for providing high‐efficiency and high‐power cylindrical vector beam and vortex beam sources.     

Ultra‐large effective‐area,higher‐order mode fibers: a new strategy for high‐power lasers

This paper describes the physics and properties of a novel optical fiber that would be attractive for building high‐power fiber lasers and amplifiers. Instead of propagating light in the fundamental, Gaussian‐shaped mode, we describe a fiber in which the signal is forced to travel in a single, desired higher order mode (HOM). This provides for several advantages over the conventional approach, ranging from significantly higher ability to scale mode areas (and hence laser powers) to managing dispersion for ultra‐short pulses – a capability that is practically nonexistent in conventional fibers. Particularly interesting is the fact that this approach challenges conventional wisdom, and demonstrates that for applications requiring meter‐length fibers (as in high‐power lasers), signal stability actually increases with mode order. Using this approach, we demonstrate mode areas exceeding 3200 μm², and propagate signals with negligible mode distortions over up to 50‐meter lengths. We describe several pulse propagation experiments in which we test the nonlinear response of this fiber platform, ranging from managing dispersive effects in femtosecond pulse systems, to reducing Brillouin scattering impairments in systems operating with the nanosecond pulses.     

Parametric Amplification of Phase‐Locked Few‐Cycle Pulses and Ultraviolet Harmonics Generation in Solids at High Repetition Rate

A high‐power femtosecond Yb:fiber system is seeded by a phase‐locked Er:fiber source and drives an ultra‐broadband optical parametric amplifier that operates at 10 MHz repetition rate. The resulting pulses display precise control of the carrier‐envelope phase. Their 8.3 fs temporal duration corresponds to 2.3 optical cycles of the 1100 nm carrier wavelength. Focusing 200 nJ of pulse energy into widegap materials generates optical harmonics up to fifth order. Even in a perturbative regime, strong effects of the carrier‐envelope phase on the emitted spectra are observed.     

Three‐dimensional ultra‐broadband integrated tapered mode multiplexers

The demonstration of a three‐dimensional tapered mode‐selective coupler in a photonic chip is reported. This waveguide‐based, ultra‐broadband mode multiplexer was fabricated using the femtosecond laser direct‐write technique in a boro‐aluminosilicate glass chip. A three‐core coupler has been shown to enable the multiplexing of the LP₀₁, LP and LP spatial modes of a multimode waveguide, across an extremely wide bandwidth exceeding 400 nm, with low loss, high mode extinction ratios and negligible mode crosstalk. Linear cascades of such devices on a single photonic chip have the potential to become a definitive technology in the realization of broadband mode‐division multiplexing for increasing optical fiber capacity.     

Q‐switched and modelocked all‐fiber lasers based on advanced acousto‐optic devices

The interest in all‐fiber lasers is stimulated by the inherent advantages they have over bulk lasers in aspects such as heat dissipation and robustness. The performance of Q‐switched and modelocked fiber lasers can benefit enormously from the development of all‐fiber configurations. A fiber laser with strictly all‐fiber components can fulfil the requirements of mechanical stability, low maintenance, enhanced power efficiency, simplified assembly process, and low cost. In this framework, recent developments infiber acousto‐optic devices are reviewed that have demonstrated new possibilities for actively Q‐switched distributed feedback fiber lasers, modelocking lasers and doubly active Q‐switched modelocked lasers. The aim is to demonstrate the great potential of infiber devices for the active control of different types of fiber lasers.     

双向使用高非线性光纤实现同时解复用出两路10 Gbit/s信号

提出一种利用双向使用高非线性光纤(HNLF)实现同时解复用出两路信号的全光解复用方案.将复用信号和控制光的混合信号从HNLF的两端同时注入,复用信号中的某一路信号通过交叉相位调制使控制光产生蓝移或红移,在HNLF的输出端用窄带滤波器将控制光的蓝移或红移部分滤出从而同时实现两路信号解复用.理论分析了信号光和控制光在HNLF中的相互作用和解复用原理.搭建80 Gbit/s光时分复用系统,对双向使用HNLF的解复用结构进行了实验研究.在HNLF的两个输出端同时实现不同信道的无误码解复用,其中信道解复用的最大功率代价为2.6 dB.     

Mid‐infrared supercontinuum covering 2.0–16 μm in a low‐loss telluride single‐mode fiber

A mid‐infrared (MIR) supercontinuum (SC) has been demonstrated in a low‐loss telluride glass fiber. The double‐cladding fiber, fabricated using a novel extrusion method, exhibits excellent transmission at 8–14 μm: < 10 dB/m in the range of 8–13.5 μm and 6 dB/m at 11 μm. Launched intense ultrashort pulsed with a central wavelength of 7 μm, the step‐index fiber generates a MIR SC spanning from ∼2.0 μm to 16 μm, for a 40‐dB spectral flatness. This is a fresh experimental demonstration to reveal that telluride glass fiber can emit across the all MIR molecular fingerprint region, which is of key importance for applications such as diagnostics, gas sensing, and greenhouse CO₂ detection.

     

用于不锈钢薄板切割的直接半导体激光源

针对高功率半导体激光器存在的光束质量差、单元功率低的缺点,利用合束技术来提高激光功率及光束质量,配合QBH光纤前端帽优化聚焦镜以实现高效耦合。采用11个条宽5.4 mm的迷你线阵合束,通过光束整形、空间合束、偏振合束和波长合束,聚焦耦合进200μm/0.2光纤。在50 A电流下,实现连续386 W输出,功率密度为1.23 MW/cm2,电光效率为43.6%。在200 W的功率下,该激光器可以切割厚度为1 mm的不锈钢薄板。     

Self-excited brillouin–erbium fiber laser for DWDM applications

The operation of the self-excited Brillouin/erbium fiber laser (BEFL) is experimentally demonstrated. It uses a forward pumped erbium-doped fiber (EDF) as a gain medium to generate a Brillouin-pump (BP) and amplify the Stokes frequency signals generated in a single-mode fiber (SMF). The operating wavelength varies with changes of coupling ratio of the looping arm. The optimum BEFL operation is obtained with a center wavelength at 1567.5 nm by looping back 20% of BEFL output into the other end of the SMF. The BEFL output power and number of lines increases gradually as 980-nm pump power increases. At the maximum 980-nm pump power of 118 mW, a stable and strong BEFL comb of up to 16 lines with 11 GHz spacing is demonstrated. The self-excited BEFL has the potential to be used in the future dense wavelength division multiplexing (DWDM) communication system.     

基于单个光纤光栅的Sagnac干涉仪的理论与实验研究

提出了一种结构新颖的Sagnac干涉仪,分析计算了所含光纤光栅分别为均匀Bragg光栅和线 性啁啾光栅时的透射响应,得到了均匀光栅Sagnac环的解析解,发现含均匀光栅时可得到间隔均匀的通带结构,而含啁啾光纤光栅时只能得到间隔非均匀的通带结构.这两种结构都可 能有应用价值,前者可用在密集波分复用系统中,后者可用在光纤传感领域中.实验制作了 两种通带间隔不同的、通带数分别为8和16的多通带滤波器,实验证实了理论计算得到的结果. 关键词： 光纤光栅 Sagnac干涉仪 光学滤波器     

Performance comparison of slow‐light coupled‐resonator optical gyroscopes

We investigate the connection between group velocity and rotation sensitivity in a number of resonant gyroscope designs. Two key comparisons are made. First, we compare two conventional sensors, namely a resonant fiber optic gyroscope (RFOG) and an interferometric fiber optic gyroscope (FOG). Second, we compare the RFOG to several recently proposed coupled‐resonator optical waveguide (CROW) gyroscopes. We show that the relationship between loss and maximum rotation sensitivity is the same for both conventional and CROW gyroscopes. Thus, coupling multiple resonators together cannot enhance rotation sensitivity. While CROW gyroscopes offer the potential for large group indices, this increase of group index does not provide a corresponding increase in the maximum sensitivity to rotation. For a given footprint and a given total loss, the highest sensitivity is shown to be achieved either in a conventional RFOG utilizing a single resonator, or a conventional FOG.     

Fiber optical parametric amplifiers in optical communication systems

The prospects for using fiber optical parametric amplifiers (OPAs) in optical communication systems are reviewed. Phase‐insensitive amplifiers (PIAs) and phase‐sensitive amplifiers (PSAs) are considered. Low‐penalty amplification at/or near 1 Tb/s has been achieved, for both wavelength‐ and time‐division multiplexed formats. High‐quality mid‐span spectral inversion has been demonstrated at 0.64 Tb/s, avoiding electronic dispersion compensation. All‐optical amplitude regeneration of amplitude‐modulated signals has been performed, while PSAs have been used to demonstrate phase regeneration of phase‐modulated signals. A PSA with 1.1‐dB noise figure has been demonstrated, and preliminary wavelength‐division multiplexing experiments have been performed with PSAs. 512 Gb/s have been transmitted over 6,000 km by periodic phase conjugation. Simulations indicate that PIAs could reach data rate x reach products in excess of 14,000 Tb/s × km in realistic wavelength‐division multiplexed long‐haul networks. Technical challenges remaining to be addressed in order for fiber OPAs to become useful for long‐haul communication networks are discussed.

     

Phase‐specific Raman analysis of n‐alkane melting by moving‐window two‐dimensional correlation spectroscopy

We use moving‐window two‐dimensional correlation spectroscopy (MW‐2DCOS) for phase‐specific Raman analysis of the n‐alkane (C₂₁H₄₄) during melting from the crystalline solid phase to the intermediate rotator phase and to the amorphous molten phase. In MW‐2DCOS, individual peak‐to‐peak correlation analysis within a small subset of spectra provides both temperature‐resolved and spectrally disentangled Raman assignments conducive to understanding phase‐specific molecular interactions and chain configurations. We demonstrate that autocorrelation MW‐2DCOS can determine the phase transition temperatures with a higher resolving power than commonly used analysis methods including individual peak intensity analysis or principal component analysis. Besides the enhanced temperature resolving power, we demonstrate that asynchronous 2DCOS near the orthorhombic‐to‐rotator transition temperature can spectrally resolve the two overlapping peaks embedded in the Raman CH₂ twisting band in the orthorhombic phase, which had been only predicted but not observed because of thermal broadening near the melting temperature. Published 2016. This article is a U.S. Government work and is in the public domain in the USA.     

基于光子晶体光纤中FWM的4×10 Gbit/s全光波长转换

 多波长转换对于增强波分复用光网络的灵活性具有重要意义。基于光子晶体光纤中的多四波混频原理,实现了4×10 Gbit/s全光波长转换,深入调查了泵浦功率、光纤长度、信号光与泵浦光偏振失配对波长转换信号质量的影响。结果表明：当泵浦光功率从6 dBm到20 dBm增长的过程中,转换信号Q因子随泵浦光功率增大而增大,最大为82.01,光纤长度从50 m到120 m变化过程中,转换信号Q因子最大为57.41,而随着信号光与泵浦光偏振失配角的增大,转换信号Q因子逐渐降低,当失配角大于60°后,转换信号质量急剧下降。     

Low‐loss aluminium nitride thin film for mid‐infrared microphotonics

Mid‐infrared (mid‐IR) microphotonic devices including (i) straight/bent waveguides and (ii) Y‐junction beam splitters are developed on thin films of CMOS‐compatible sputter deposited aluminum nitride (AlN)‐on‐silicon. An optical loss of 0.83 dB/cm at λ = 2.5 µm is achieved. In addition, an efficient mid‐IR 50:50 beam splitter is demonstrated over 200 nm spectral bandwidth along with a <2% power difference between adjacent channels. With the inherent advantage of an ultra‐wide transparent window (ultraviolent to mid‐IR), our AlN mid‐IR platform can enable broadband optical networks on a chip.     

Experimental Demonstration of SCM-PON Monitoring with Baseband Embedded OTDR

The combination of subcarrier multiplexing and passive optical networks can provide an efficient and cost-effective solution for fiber and wireless convergence in access networks. Moreover, to reduce operational expenditures, a reliable monitoring technique should provide in-service evaluation of the physical layer. Here, we perform the experimental demonstration of an SCM-PON system with baseband embedded optical time-domain reflectometer monitoring. Different modulation formats were tested to evaluate the penalty generated by the monitoring system. Based on the long-term evolution downlink test model (E-TM 3.1), our results show negligible power penalty while achieving a ~12-dB dynamic range with 10-m spatial resolution.     

Recent advances in the development of discharge‐pumped oxygen‐iodine lasers

Chemical oxygen‐iodine lasers are unique in their ability to generate high‐power beams with near diffraction limited beam quality. The operating wavelength, 1.315 µm is readily transmitted by the atmosphere and compatible with fiber optics beam delivery systems. However, applications of the laser are severely limited by logistical problems associated with the complex chemistry used to power the device. Electrical or microwave discharge excitation of oxygen‐iodine lasers offers an attractive alternative that eliminates the chemical power generation problems and has the possibility of closed‐cycle operation. A discharge oxygen‐iodine laser was first demonstrated in 2005. Since that time the power of the device has been improved by a factor of 400 and much has been learned concerning the physics and chemistry of the discharge driven system. Although our current understanding of the chemical kinetics is incomplete, parametric studies of laser performance show considerable promise for further scaling. This article reviews the basic principles of the discharge oxygen iodine laser, summarizes the most recent advances, and outlines some of the unresolved questions regarding the production and removal of excited species in the gas flow.     

高重复频率短脉冲全光纤激光系统

采用时分复用技术在输出80MHz重复频率光纤锁模激光器的基础上,实现了重复频率倍增,获得了160MHz的高重复频率输出。理论和实验研究了高重复频率短脉冲在大模面积掺Yb3+光纤中的放大特性,实验上获得了输出平均功率105W,脉冲宽度12.4ps,重复频率160MHz的高重复频率短脉冲光纤激光系统。