高重复频率飞秒掺镱光纤放大器

 数值分析了掺镱单模光纤放大器的最佳增益光纤长度，并在实验上对掺镱单模光纤放大器和光栅对压缩器进行了研究。以最大平均输出功率为7 mW、重复频率为25.4 MHz、脉宽为56 ps的被动锁模环形腔掺镱光纤激光器作为种子脉冲，用250 mW的976 nm单模半导体激光器分别泵浦3种不同长度的掺镱单模光纤，对种子光进行放大，并用光栅对压缩器对放大后的脉冲在不同光栅距离上进行了压缩实验研究。当掺镱单模光纤长度为1.2 m时得到了较好的放大效果，种子脉冲被放大到140 mW，相应的增益为13 dB，放大后的单脉冲能量为5.5 nJ。在光栅距离为14.1 cm时获得了最短440 fs的脉冲，压缩后的功率为43 mW，相应的峰值功率为3.8 kW。     

Single-frequency Yb:YAG non-planar ring oscillator fiber amplifier source at 1030 nm

We report on amplification of a single-frequency Yb:YAG non-planar ring oscillator using Yb-doped fibers. The amplifier system operated at 1030 nm with up to 18.7 W output power, 75% slope efficiency and an M²-value better than 1.1.     

Power transfer characteristics among N parallel single-mode optical fibers

Based on the coupled-mode theory, the power transfer among “- - - -” arranged parallel single-mode optical fibers has been investigated. The analysis shows that the distances between each two of the N fiber centers have effects on the coupling coefficient and power transfer. The solution of the coupled-equations for three parallel single-mode optical fibers is given, and is studied for different initial conditions comparatively. Numerical simulations show that power transfer will be periodical during coupling among parallel single-mode optical fibers. These results can be extended to multi-parallel single-mode optical fibers.     

A high spectral brightness Fourier-transform limited nanosecond Yb-doped fiber amplifier

In this paper, we present a frequency-doubled pulsed Yb-doped fiber amplifier exhibiting Fourier-transform limited 10-ns pulses at a repetition rate of up to 5 kHz. The amplifier is seeded by an external cavity diode laser whose output is chopped into light pulses of 10- to 1200-ns duration. The first stage is operated with a single-mode fiber, while the other two stages employ multi-mode double clad fibers. Output energies of up to 516 μJ per pulse have been recorded. The output power is limited by the onset of stimulated Brillouin scattering. As an example of the possible applications, we demonstrate the temperature measurement of water by Brillouin scattering employing the frequency-doubled radiation from the amplifier.     

72-kW high-peak-power linearly-polarized single-mode pulsed fiber laser with 80 kHz repetition rate and 4.5 ns duration

We reported a 26 W linearly polarized single-mode Yb-doped photonic crystal fiber amplifier, working at 80 kHz repetition rate with 4.5 ns duration, corresponding 72 kW peak power. Using a acousto-optic Q-switched Nd:YVO₄ laser as the seed source, the 26 W average power of 1064 nm laser was obtained at a repetition rate of 80 kHz from a Yb-doped photonic crystal fiber amplifier, with 4.5 ns duration, polarization extinction ratio 11 dB and M ² < 1.2.     

Random distributed feedback fiber laser pumped by an ytterbium doped fiber laser

A random distributed feedback fiber laser operating at 1115 nm has been demonstrated experimentally in standard communication optical fibers by using a LD-pumped Yb-doped fiber laser as the pump source. We have studied the effect of different fiber spans on this new type of random fiber laser output power. It is shown that the generation power is the highest up to 198 mW in a 50 km fiber span. The slope efficiency is more than 28.7%. Stable, high-power continuous-wave (CW) lasing can be generated when the pump power is 3.6 W. The threshold power has also been calculated which well proves a random fiber laser operating via Rayleigh scattering, amplified through the Raman scattering.     

High-power continuous-wave output of master oscillator power amplifier system at 1053 and 1083 nm

We report the efficient generation of high-power laser radiation at 1053 and 1083 nm wavelength by using of a hybrid master oscillator fiber power amplifier system, consisting of a diode-pumped Yb-doped oxyorthosilicate solid state laser as the master oscillator and an Yb-doped large-mode-area fiber as the power amplifier. Efficient tunable diode-pumped Yb-doped oxyorthosilicate lasers at 1053 and 1083 nm have been constructed, which was scaled up to a maximum output power of 34.5 W at 1053 nm and 30.2 W at 1083 nm by a fiber power amplifier, corresponding to a slope efficiency of 93.9 and 87.8%, respectively.     

Environmentally stable ytterbium figure-of-eight fiber laser producing 177-fs pulses

Pulses of 177 fs and 1035 nm, with average power of 1.2 mW, have been generated directly from a passively mode-locked Yb-doped figure-of-eight fiber laser, with a nonlinear optical loop mirror for mode-locking and pairs of diffraction gratings for intracavity dispersion compensation. To our knowledge, these are the shortest pulses ever to come from a passively mode-locked Yb-doped figure-of-eight fiber laser. This represents a 5-fold reduction in pulse duration compared with that of previously reported passively mode-locked Yb-doped figure-of-eight fiber lasers. Stable pulse trains are produced at the fundamental repetition rate of the resonator, 24.0 MHz.     

Single mode MOPA structured all-fiber Yb pulse fiber amplifier at low repetition

We describe a mopa structured all-fiber 15 μm fiber amplifier cascade. A single-mode diode laser generating 1064 nm wavelength, several nanosecond pulses at 100 Hz repetition was adopted to seed a corepumping amplifier featuring a 6 μm core Yb-doped fiber. Multi-stage pulse-pumping technology was applied to eliminate ASE as much as possible and ease the heat load of the system that leads to the freedom of temperature control of the laser diode. The master oscillator-power amplifier (MOPA) generated 1064 nm, 18 ns pulse-width, 100 Hz repetition of 220 μJ single pulse energy, peak power >12 kW with single transverse output. The pulse energy of 220 μJ is the largest to date in the all-fiber MOPA amplifier with core diameter around 15 μm to our knowledge.     

980 nm Yb-doped single-mode fiber laser and its frequency-doubling with BIBO

A quasi-three-level Yb-doped single-mode fiber laser at 980 nm by adopting two 0° fiber ends as cavity mirrors generated a total output power of 1.32 W with the slope efficiency of 75.3%. The fiber length was 36.5 cm close to the optimal theoretical fiber length. The corresponding optical conversion efficiency was 66% from the incident pump power at 946 nm to the laser power at 980 nm. Through frequency-doubling with BIBO crystal, a total output power of 15 mW at 490.8 nm was obtained.     

Diode-lasers based apparatus and method for single-mode fibers spectral splice loss measurements

Arc-discharge fusion splicing is widely used in the telecommunication industry for joining single-mode optical fibers to Er-doped fiber coils. These coils are used as the gain medium in erbium-doped amplifiers (EDFAs). The quality and integrity of splicing these coils to fibers can impact key EDFA performance parameters. This article describes an automated splice loss and Er-doped fiber absorption measurement system. The measurement system is equipped with 1310, 1550 and 1563 nm DFB lasers, broadband light source, InGaAs detectors and fiber-optic internal standards. Furthermore, the article describes a method for measuring splice loss between Er-doped fiber and the fibers spliced to coil ends. The system controls splice loss between SM-28 or HI980 fiber and Er-doped fiber to 0.094 ± 0.052 dB at 1550 nm. Moreover, the system can measure accurately Er-doped fiber absorption to within ±3.19% at 1563 nm.     

22 dB all-fiber green amplifier using Er-doped fluoride fiber

We demonstrate a 22 dB all-fiber amplifier at 546 nm using Er³⁺-doped fluoride fiber by forward upconversion pumping of a 974 nm laser diode. The gain saturation effects and the power conversion efficiency of this amplifier are investigated in detail based on gain characteristics and numerical simulations.     

Specialty Yb fiber amplifier for microchip Nd laser: Towards ∼1-mJ/1-ns output at kHz-range repetition rate

We demonstrate and optimize, for a mJ/ns release at the wavelength 1.064 μm, the operation of a compact laser system designed in the form of a hybrid, active-passive, Q-switched Nd³⁺:YAG/Cr⁴⁺:YAG microchip laser seeding an Yb-doped specialty multi-port fiber amplifier. As the result of the amplifier optimization, ∼1 mJ, ∼1 ns, almost single-mode pulses at a 1-10-kHz repetition rate are achieved, given by a gain factor of ∼19 dB for an 11-μJ input from the microchip laser. Meanwhile, a lower pulse energy, ∼120 μJ, but a much higher gain (∼25 dB) are eligible for the less powerful (0.35 μJ) input pulses.     

High efficiency Tm fiber laser of seed amplification

We use all-fiber single-mode lasers as seed source, amplifiers and pump laser coupling amplifier has been experimentally investigated, respectively. The maximum output power is 10.4 W, with the slope efficiency of 54.4% when the seed laser power is 1 W, and the slope efficiency is 48.7% when the seed laser power is 2 W. The slope efficiency of this scheme is higher than that of the all-fiber amplifier. This can be explained by the loss of pump power at the splice dots. The wavelength of the fiber amplifier is 1947.6 nm, the same as the seed laser's, with a linewidth of 2 nm. We estimate the beam quality to be M² = 2.39, clearly indicating nearly diffraction-limited beam propagation.     

All-fiber actively Q-switched Yb-doped laser

An all-fiber actively Q-switched Yb-doped laser is presented. Q-switching is performed by modulating a fiber Bragg grating via a magnetostrictive rod which is fixed to the fiber at the position of the grating. By exposing the rod to a changing magnetic field, the rod is stretched and relaxed causing the Bragg wavelength of the grating to shift and thereby changes the Q-factor of the cavity. Using Yb-doped fiber, pulses at 1052 nm are obtained at repetition rates from 1 to 200 kHz. At 75 kHz, 0.5 μJ pulses with peak powers of 3 W can be produced when 180 mW of pump power is applied. To the knowledge of the authors, this is the first all-fiber actively Q-switched Yb-doped laser presented to date.     

Characteristics of wave-breaking-free operation in a passively mode-locked all-fiber ring laser based on AS-Yb-PBGF

A passively mode-locked all-fiber ring laser is constructed based on all-solid Yb-doped photonic bandgap fibers (AS-Yb-PBGF), which provides the laser gain and anomalous dispersion simultaneously. Without any other dispersion compensators, the cavity is simple, compact, and maintenance- and alignment-free. The characteristics of wave-breaking-free operation in the laser are investigated by means of numerical simulations using the split-step Fourier method. The approximately parabolic pulses can be generated and evolved for maintaining the normal group-velocity dispersion intracavity, when the length of the single-mode fiber is between 2 and 4 m. The obtained highest energy of the output pulse is up to 2.27 nJ with the pulse duration of 8.61 ps, corresponding to the time-bandwidth product of 10.05. By dechirping out of cavity, the pulse duration is 0.70 ps.     

33 W continuous-wave single-frequency green laser by frequency doubling of a single-mode YDFA

A high power continuous-wave single-frequency green fiber laser by second-harmonic generation of a Yb-doped fiber amplifier(YDFA)is developed.A linearly polarized single-mode fiber amplifier produces a 60 W infrared laser at 1064 nm with a 103 W incident diode pump laser at 976 nm,corresponding to an optical conversion efficiency of 58%.An external bow-tie enhancement cavity incorporating a noncritically phase-matched lithium triborate crystal is employed for second-harmonic generation.A 33.2 W laser at 532 nm is obtained with a 45 W incident 1064 nm fundamental laser,corresponding to a conversion efficiency of 74%.     

Dual-wavelength high-power Yb-doped double-clad fiber laser based on a few-mode fiber Bragg grating

We report a high-power dual-wavelength Yb-doped double-clad fiber laser based on a few-mode fiber Bragg grating (FMFBG). The FMFBG was fabricated by using a piece of fiber in a length of fiber with a cutoff wavelength of 1225 nm, which supported two modes at 1060 nm. The laser was pumped by a fiber pigtailed laser diode working at 915 nm. Single-wavelength, dual-wavelength and triple-wavelength laser oscillations were observed when the fiber laser operated under different low pump powers. However, stable dual-wavelength operation was achieved at higher pump power of 3.9 W and remained unchanged until the output power reached 5.67 W under the maximum available pump power of 10.7 W. The laser wavelengths were centered at 1059.12 and 1060.80 nm with a full-width at half-maximum of 37 and 43 pm, respectively. The signal-to-noise-ratio was greater than 50 dB and the beam quality factor (M²) was about 1.9.     

Linearly polarized, 3.35 W narrow-linewidth, 1150 nm fiber master oscillator power amplifier for frequency doubling to the yellow

A high-power linearly polarized Yb-doped silica fiber master oscillator power amplifier at 1150 nm is reported. It produced 3.35 W cw and 2.33 W of average power in 1 micros pulses at a 100 kHz repetition rate, both with 8 pm linewidth. This is the first report, to the best of our knowledge, of a high-power Yb-doped fiber amplifier at a wavelength longer than 1135 nm. The pulsed output was frequency doubled in a bulk periodically poled near-stoichiometric LiTaO(3) chip to generate 976 mW of average power at 575 nm with an overall system optical-to-optical efficiency of 9.8% with respect to launched pump power.     

1018 nm短波长掺镱光纤激光高功率自组织相干合成

搭建了两台高功率、低量子损耗的1018 nm短波长掺镱光纤激光器,进行了全光纤结构下两路光纤激光器的相干合成实验。获得了功率为55 W、合成效率为90.2%的相干输出,这是当前严格单模1018 nm光纤激光器的最高功率水平。同时,验证了Michelson腔自组织相干合成技术能够实现光纤激光器的高功率单模输出。