Generation of 11 fs pulses by using hollow-core gas-filled fibers at a 100 kHz repetition rate

Using self-phase modulation in a hollow-core fiber filled with xenon, we were able to produce 2.3 microJ laser pulses with a duration of 10.9 fs at a repetition rate of up to 100 kHz. We started with 45 fs, 4.4 microJ, 800 nm pulses generated by a Coherent RegA Ti:sapphire regenerative amplifier system, then spectrally broadened the 30 nm bandwidth to more than 100 nm. Dispersion compensation was achieved with two pairs of chirped mirrors. This is believed to be the first time this type of compression was achieved at a repetition rate as high as 100 kHz. This brings the advantages of few-cycle laser pulses to experiments that require high-repetition-rate, low-energy laser systems, for example, coincidence experiments.     

Parametric amplification of few-cycle carrier-envelope phase-stable pulses at 2.1 microm

We demonstrate an optical parametric chirped-pulse amplifier producing infrared 20 fs (3-optical-cycle) pulses with a stable carrier-envelope phase. The amplifier is seeded with self-phase-stabilized pulses obtained by optical rectification of the output of an ultrabroadband Ti:sapphire oscillator. Energies of -80 microJ with a well-suppressed background of parametric superfluorescence and up to 400 microJ with a superfluorescence background are obtained from a two-stage parametric amplifier based on periodically poled LiNbO3 and LiTaO3 crystals. The parametric amplifier is pumped by an optically synchronized 1 kHz, 30 ps, 1053 nm Nd:YLF amplifier seeded by the same Ti:sapphire oscillator.     

Periodically poled lithium niobate optical parametric amplifier seeded with the narrow-band filtered output of an optical parametric generator

The results of a simple scheme to generate continuously tunable pulsed narrow-bandwidth (less than 0.1 cm (-1)) light in the infrared are presented. A periodically poled lithium niobate (PPLN) optical parametric amplifier is seeded with the filtered output of a PPLN optical parametric generator. A high-finesse Fabry-Perot etalon is used as the filtering element, giving bandwidths as narrow as 0.08 cm (-1) and tunable over 18 cm (-1) without any adjustments to the PPLN crystals. High efficiency is obtained with a 15-ns 1-kHz Nd:YAG laser, giving energies of up to 180 microJ of signal at 1.6 microm and 60 microJ of idler at 3.3 microm .     

Multiple-Output Fiber-Ring Lasers and Amplifiers in a Hybrid CATV and ADSL Broadcasting Optical Fiber Communication System

In this article we propose two kinds of new fiber ring structure with a semiconductor optical amplifier. The first structure is a one-fiber-ring amplifier with an 8 × 8 fiber coupler and a semiconductor optical amplifier (SOA). The second fiber ring structure is a two-fiber-ring laser including an 8 × 8 fiber coupler, a 2 × 2 E/O modulator, and an SOA. The 14-output spectra of the fiber laser are measured. The gain coefficients of each port of the multiple-output-fiber-ring amplifiers are also measured. We apply these two kinds of fiber ring structures in a hybrid CATV and ADSL broadcasting optical fiber communication system. This application can develop a broadcasting system with large coverage area without using many laser diodes and optical amplifiers. The performance of such a system is also analyzed in this article.     

Transform-limited 100 microJ, 340 MW pulses from a nonlinear-fiber chirped-pulse amplifier using a mismatched grating stretcher-compressor

We report on a compact double-stage ytterbium-doped-fiber chirped-pulse amplifier system delivering high temporal quality 270 fs pulses of 100 microJ energy at a repetition rate of 300 kHz resulting in a peak power of 340 MW. The recompression down to 1.1 times the Fourier limit is based on the exploitation of nonlinear phase shifts associated with mismatched stretcher-compressor units. A 1-m-long ytterbium-doped 80 mum core diameter photonic crystal fiber is implemented as the power amplifier and allows the production of 143 microJ pulses before compression with an accumulated B integral of 17 rad throughout the amplification stages.     

Multiple-Output Fiber-Ring Lasers and Amplifiers in a Hybrid CATV and ADSL Broadcasting Optical Fiber Communication System

In this article we propose two kinds of new fiber ring structure with a semiconductor optical amplifier. The first structure is a one-fiber-ring amplifier with an 8 × 8 fiber coupler and a semiconductor optical amplifier (SOA). The second fiber ring structure is a two-fiber-ring laser including an 8 × 8 fiber coupler, a 2 × 2 E/O modulator, and an SOA. The 14-output spectra of the fiber laser are measured. The gain coefficients of each port of the multiple-output-fiber-ring amplifiers are also measured. We apply these two kinds of fiber ring structures in a hybrid CATV and ADSL broadcasting optical fiber communication system. This application can develop a broadcasting system with large coverage area without using many laser diodes and optical amplifiers. The performance of such a system is also analyzed in this article.     

Dual-core ytterbium fiber amplifier for high-power 1060 nm swept source multichannel optical coherence tomography imaging

A novel (to our knowledge) dual-core ytterbium (Yb(3+)) doped fiber, as an optically pumped amplifier, boosts the output power from a 1060 nm swept source laser beyond 250 mW, while providing a wavelength tuning range of 93 nm, for optical coherence tomography (OCT) imaging. The design of the dual-core Yb-doped fiber amplifier and its multiple wavelength optical pumping scheme to optimize output bandwidth are discussed. Use of the dual-core fiber amplifier showed no appreciable degradation to the coherence length of the seed laser. The signal intensity improvement of this amplifier is demonstrated on a multichannel in vivo OCT imaging system at 1060 nm.     

Development of a high-pulse-energy Q-switched Tm-doped double-clad fluoride fiber laser and its application to the pumping of mid-IR lasers

A diode-pumped Q-switched Tm-doped double-clad fluoride fiber laser is reported providing up to 90 microJ pulse energy (160 ns, 100 kHz, i.e., 9 W of average power). The dependence of the fiber laser's repetition rate on pump power and modulator repetition rate was investigated. By amplification even higher pulse energies of 410 microJ could be generated. In a second stage of the setup the Q-switched fiber laser serves as a pump for a gain-switched tunable Cr2+:ZnSe laser. The pulse energies reported are to the author's knowledge the highest generated by Tm-doped fluoride fiber lasers or amplifiers today.     

1410 nm波段分布式光纤拉曼增益放大器的研究

讨论了分布式光纤拉曼增益放大器的工作原理,采用1320nm固体激光器作为抽运源,获得了1410nm波段附近的光放大,在单模GI光纤长度为23km时,初步研究了拉曼放大器增益与光纤作用长度的关系,抽运脉冲峰值功率分别为50W、30W时,光纤的有效作用长度分别为15．5km和10.5km;研究了在不同的光纤有效作用长度时,拉曼放大器增益与抽运功率的关系;从光纤拉曼光谱图估算了光纤拉曼放大器的光谱宽度为50nm或250cm^-1。     

Pressure sensing utilizing linear cavity erbium-doped fiber laser

In this paper, we report a fiber laser pressure sensor based on linear cavity erbium-doped fiber laser. The fiber laser structure comprises of an erbium-doped fiber amplifier, a circulator, an optical coupler and a fiber Bragg grating (FBG) which acts simultaneously as a lasing wavelength selecting components as well as a pressure sensor. The FBG is fitted to the shock tube where the pressure is applied. The fiber laser pressure sensor has a low threshold power of 7 mW, an output power of 2.28 mW and an optical signal to noise ratio over 55 dB. The proposed fiber laser sensor is expected to be an attractive choice for long-distance pressure monitoring.     

Pulsed ytterbium-doped large mode area double-clad fiber amplifier in MOFPA configuration

A pulsed master oscillator fiber power amplifier working in nanosecond range has been developed. An ytterbium-doped double-clad (large mode area) optical fiber was used as an amplifying medium. Actively Q-switched Nd:YVO laser was used as a seed of light pulses. The system worked at the repetition rate from 10 kHz to 40 kHz. At the amplifier output, pulses of 10.9 kW peak-power were achieved. The laser system worked at the slope efficiency of 30%.     

158-microJ pulses from a single-transverse-mode, large-mode-area erbium-doped fiber amplifier

We report the amplification of 10-100-pJ semiconductor diode pulses to an energy of 158 microJ and peak powers >100 kW in a multistage fiber amplifier chain based on a single-mode, large-mode-area erbium-doped amplifier design. To our knowledge these results represent the highest single-mode pulse energy extracted from any doped-fiber system.     

300 microJ noncollinear optical parametric amplifier in the visible at 1 kHz repetition rate

We demonstrate an order-of-magnitude energy scaling of a white-light seeded noncollinear optical parametric amplifier in the visible. The generated pulses, tunable between 520 and 650 nm with sub-25-fs duration, had energies up to 310 microJ with 20% blue-pump-to-signal energy conversion efficiency at 540 nm. This new ultrafast source will make possible numerous extreme nonlinear optics applications. As a first application, we demonstrate the generation of tunable vacuum ultraviolet pulses.     

Intense self-compressed, self-phase-stabilized few-cycle pulses at 2 microm from an optical filament

We report the compression of intense, carrier-envelope phase stable mid-IR pulses down to few-cycle duration using an optical filament. A filament in xenon gas is formed by using self-phase stabilized 330 microJ 55 fs pulses at 2 microm produced via difference-frequency generation in a Ti:sapphire-pumped optical parametric amplifier. The ultrabroadband 2 microm carrier-wavelength output is self-compressed below 3 optical cycles and has a 270 microJ pulse energy. The self-locked phase offset of the 2 microm difference-frequency field is preserved after filamentation. This is to our knowledge the first experimental realization of pulse compression in optical filaments at mid-IR wavelengths (lambda>0.8 microm).     

一种测量GaAs-GaAlAs行波激光放大器增益特性的实验方法

本文报导了一种测量光耦合效率η的新实验方法。这个方法是建立于p-n结短路光电流原理上的。本文推导出适合于行波激光放大器的光耦合效率的公式。短路光电流用一检流计测量,利用公式获得光耦合效率的实验值。利用实验所测光耦合效率,测量了行波激光放大器的增益随注入电流变化的规律,其结果和实验符合。另外本文还介绍了在脉冲注入电流条件下测行波半导体激光放大器增益的实验方法。     

间隔可调多波长光纤激光器的实验研究

半导体光放大器(SOA)的非均匀加宽特性对产生多波长激光非常有利。本文对两段式立奥-萨尼亚克(Lyot-Sagnac)滤波器进行了详细的理论分析,实现了一种基于半导体光放大器的新型多波长光纤激光器。它利用立奥-萨尼亚克滤波器的波长选择性,在室温下得到了约18个具有30 dB信噪比的多波长激光输出。波长范围1556~1577 nm。通过调节立奥-萨尼亚克环内的偏振控制器,多波长激光的波长间隔可在两种国际电信联盟(ITU)标准波长间隔(0.4 nm和0.8 nm)间选择。这种构型的光纤激光器具有稳定性好、波长间隔可控、信噪比高等优点。     

Multikilohertz optical parametric chirped pulse amplification in periodically poled stoichiometric LiTaO3 at 1235 nm

We demonstrate, for the first time to our knowledge, multikilohertz operation of a double-stage optical parametric chirped pulse amplifier with periodically poled stoichiometric LiTaO3 crystals, seeded by a homemade Cr:forsterite oscillator operating at 1235 nm. The repetition rate of the amplifier could easily be tuned without the use of electro-optic modulators by using a repetition-rate-tunable kilohertz pump laser operating at 532 nm and a time-synchronization unit. Amplified total (signal+idler) energies of 55.9 and 36.2 microJ were achieved at 1 and 5 kHz, respectively. After recompression, the pulse width of amplified idler pulses at 1235 nm amounted to 530 fs.     

Compact directly diode-pumped femtosecond Nd:glass chirped-pulse-amplification laser system

An all-solid-state longitudinally diode-pumped Nd:glass chirped-pulse-amplification laser system producing pulses of 50-MW peak power has been developed. The diode-pumped Nd:glass regenerative amplifier produces pulses with energies as great as 56microJ at a 1-kHz repetition rate and pulse durations as short as 450 fs after compression in a compact single holographic-transmission-grating stretcher-compressor arrangement. Further, spectral gain shaping was shown to extend the bandwidth that was supported in the low-gain amplifier. To the best of our knowledge, this system provides the highest peak and average power obtained from a directly diode-pumped femtosecond laser.     

基于高双折射光纤布拉格光栅的自动增益控制掺铒光纤放大器

掺铒光纤非均匀展宽引起的空间烧孔现象导致单波长激光并不能完全控制放大器增益,提出了一种新颖的自动增益控制掺铒光纤放大器的结构:即采用高双折射光纤布拉格光栅产生抽运光,其写制光栅的波峰对应的波长分别为1549.3 nm和1549.83 nm,波长间隔为0.53 nm。通过调整偏振控制器,就实现了单激光或双激光的增益控制。这种设计增益控制范围为40 nm(1530~1570 nm),当输入功率在-40~-15 dBm的动态范围内,双激光增益控制的掺铒光纤放大器的平均增益和噪声系数分别约为22.22 dB和8.69 dB,而它们的漂移分别被钳制在0.69 dB和1.51 dB。系统性能测试表明:双激光控制掺饵光纤放大器在稳定性方面比单激光有着明显的优势。     

High-power Tm-doped fiber distributed-feedback laser at 1943 nm

We report on high-power operation of a fiber distributed-feedback (DFB) laser fabricated from Tm-doped photosensitive alumino-silicate fiber and in-band pumped by an Er/Yb fiber laser at 1565 nm. The fiber DFB laser yielded up to 875 mW of single-ended output at 1943 nm on two orthogonally polarized modes for 3.5 W of absorbed pump power. Further scaling of the DFB laser output power was achieved with the aid of a simple Tm-doped fiber amplifier stage spliced directly to the DFB fiber without the need of an optical isolator. The maximum output power from the DFB laser and fiber amplifier was >3 W for a combined absorbed pump power of 8.1 W. The influence of thermal loading, owing to quantum defect heating in the Tm-doped core, on the output power and longitudinal mode behavior is discussed, and the prospects for further improvement in performance are considered.