Dual-Wavelength Holmium-Doped Fiber Laser Pumped by Thulium-Ytterbium Co-Doped Fiber Laser

We present an all-fiber dual-wavelength holmium-doped veloped holmium-doped fiber （HDF） as a gain medium fiber laser operating in 2 #m region using a newly de- The proposed fiber laser is constructed by using a hybrid gain medium, i.e., a thulium ytterbium co-doped fiber （TYDF） and an HDF in conjunction with a simple half-opened linear cavity, which is formed by a broadband mirror and an output coupler reflector. Without the HDF, the TYDF laser operates at wavelengths of 1991 and 1999nm with a signal-to-noise ratio of more than 34dB and the slope efficiency of 26.16 %. With the HDF, dual-wavelength output lines are obtained at 2075 and 2083nm with signal-to-noise ratios of more than difference between the two peaks of less than 1 dB at 17dB, 3dB bandwidth of less than 0.2nm and the power the TYDF laser pump power of 320roW.

An Actively Mode-Locked Ho:YAG Solid-Laser Pumped by a Tm-Doped Fiber Laser

An actively mode-locked Ho： YAG laser pumped by a diode-pumped Tin-doped fiber laser is reported. For the cw operation, we obtain the maximum output power of 3.43 W with a central wavelength 2022.2nm at the maximum incident pump power of 11.4 W, corresponding to a slope efficiency of 34.5%. The beam quality factor M2 is 1.16, and the output beam is close to fundamental TEMoo. In the case of the CWML operation, a stable pulse train is generated with an average output power up to 3.41 W with a slope efficiency of 34.3% at the incident pump power of 11.4 W and a pulse duration of 294ps at a repetition rate of 81.92MHz. In addition, the maximum single pulse energy is 41.6nJ.

Theoretical and Numerical Study of Stress and Thermo-Optic in Photonic Crystal Fiber Laser in Different Pump Schemes

In this paper, we present a study of thermal, average power scaling, change in index of refraction and stress in photonic crystal fiber lasers with different pump schemes: forward pump scheme, backward pump scheme, forward pump scheme with reflection of 98%, backward pump scheme with reflection of 98% and bi-directional pump scheme. We show that management of thermal effects in fiber lasers will determine the efficiency and success of scaling-up efforts. In addition, we show that the most suitable scheme is the bi-directional.

Highly efficient cascaded P-doped Raman fiber laser pumped by Nd:YVO4 solid-state laser

A highly efficient cascaded P-doped Raman fiber laser （RFL） pumped by a 1064-nm continuous wave （CW） Nd：YVO4 solid-state laser is reported. 1.15-W CW output power at 1484 nm is obtained while the input pump power is 4 W, corresponding to the power conversion efficiency of 28.8%. The threshold pump power for the second-order Stokes radiation is 1.13 W. The slope efficiency is as high as 42.6%. The experimental results are in good agreement with theoretical ones. Furthermore, the power instability of the P-doped RFL at 1484 nm in an hour is observed to be less than 5%.

4-W single transverse mode Yb^(3+)-doped fiber laser pumped by 915-nm laser diode array

A cladding-pumped ytterbium-doped fiber laser is described in this letter. Using unusual pumping source with 915-nm wavelength, slope efficiency up to 75% with respect to absorbed input power and output power is obtained, a maximum output power of 4.006 W with fundamental mode is measured.

Tandem-pumped 1120-nm actively Q-switched fiber laser

We report on a tandem-pumped actively Q-switched fiber laser system emitting at 1120 nm.Parasitic oscillation is challenging in Yb-doped Q-switched 1120-nm fiber laser,which is suppressed by pumping with a fiber laser at 1018 nm.At least four times improvement in output peak power is demonstrated in a single laser setup with 1018-nm fiber laser pumping instead of 976-nm laser diode pumping.This is,to the best of our knowledge,the first demonstration of a tandem-pumped Q-switched fiber laser.

Tunable Supercontinuum Generated in a Yb^3＋-Doped Microstructure Fiber Pumped by Ti：Sapphire Femtosecond Laser

We experimentally demonstrate that a tunable supercontinuum（SC） can be generated in a Yb3＋-doped microstructure fiber by the concept of wavelength conversion with a Ti：sapphire femtosecond（fs） laser as the pump.Experimental results show that an emission light around 1040 nm in an anomalous dispersion region is first generated and amplified by fs pulses in the normal dispersion region. Then, SC spectra from 1100 to 1380 nm and 630 to 840 nm can be achieved by combined effects of higher-order soliton fission and Raman soliton self-frequency shift in the anomalous dispersion region and self-phase modulation, dispersive wave, and four-wave mixing in the normal dispersion region. It is also demonstrated that the 20 nm change of pump results in a 280 nm broadband shift of soliton and the further red-shift of soliton is limited by OH-absorption at 1380 nm.

The Comparative Study of the Temperature Distribution of Fiber Laser with Different Pump Schemes

Based on the structure of the long fiber laser (YDCFLs) with different pump schemes using high pump power, the nonlinear coupled and heat dissipation equations are solved numerically. Using the finite-difference method, we have determined the temperature distribution along the radial and axial directions of the fiber laser (YDCFLs) for the forward pump schemes of 200 W with reflection Rp2, backward pump schemes of 200 W with reflection Rp1 and for bidirectional pump scheme of 100 W each side. The results are: the temperature distribution for bidirectional pump mode is more even than that for forward pump with reflection Rp2 and than that for backward pump with reflection Rp1. The results show that the maximum temperature difference between different schemes is 57.51°C, and when the air-clad width decreases, the temperature in the core regions also decreases and does not affect to the cladding radius regions. We summarize that the temperature in the core and in cladding radius regions decreases when the outer radius cladding increases.

High conversion efficiency, high power density Q-switched fiber laser

An acoustic-optic Q-switched all-fiber laser With a high-repetition-rate, a short pulse width, a wide spectrum, and a high conversion efficiency is experimentally demonstrated. In the laser configuration, a （1＋1）x 1 side-pumping coupler is introduced to perform backward pumping, and a 10/130%tm Yb fiber is adopted. The acoustic-optic component operates in the first direction, achieving a Q-switched pulse with a repetition rate adjustable in the range of 20 kHz-80 kHz. Under a repetition rate of 20 kHz and a pump power of 6.76 W, the fiber laser obtains a highly efficient and stable pulse output, with an average power of 4.3 W, a pulse width of 56 ns, a peak power of 3.83 kW, and a power density of 1.39x 101~ W/cm2. Particularly, the optic-optic conversion efficiency of the laser reaches as high as 64%. Another feature of the pulsed laser is that the high reflection mirror reflects the pump light as well, which brings the secondary absorption of the pump power into the gain fiber.

基于锥形掺镱光纤实现20 kW高光束质量激光输出

锥形光纤能够有效兼顾非线性效应抑制和模式控制,具备实现高功率、高光束质量光纤激光的潜力。近期国防科技大学研制了锥形掺镱光纤,采用1 018 nm光纤激光后向级联泵浦实现了20.2 kW激光输出,光束质量β因子平均值优于2,拉曼抑制比为33 dB。研究结果展示了锥形光纤在实现万瓦级高光束质量激光方面的优势。

Comparative Study of the Birefringence in Photonic Crystal Fiber Lasers

In this paper, we study the birefringence in photonic crystal fiber lasers PCFs and in conventional fiber lasers in the bi-directional pump scheme in the linear cavity laser. We show that the value of birefringence in photonic crystal fibers is smaller than that of conventional fiber lasers [1].

可应用于光纤激光器的高稳定度泵浦源系统研制

为了提升光纤激光器的输出性能,研制了一个高稳定度泵浦源系统,包括激光泵浦模块和外围控制系统。泵浦源系统测试结果表明,输出光功率与驱动电流之间具有良好的线性关系,输出光功率的短期稳定度为0.0613%,长期稳定度为0.1080%,而且输出光谱的中心波长在长时间持续运行中稳定不变。将该泵浦源系统应用于光纤激光器,经过连续测试,输出光谱的中心波长仅发生4 pm的偏移。

用于太阳光泵浦光纤激光聚光系统的改进型复合抛物面聚光器的设计

为研制适用于太阳光泵浦光纤激光器的聚光系统,在分析了传统复合抛物面聚光器(CPC)用于耦合光纤的可行性及其缺陷的基础上,提出了一种改进型CPC用于光纤耦合。完成了由主级抛物面反射镜和次级改进型CPC组成的太阳光泵浦多级聚光方案,并与普通CPC和透镜组构成次级聚光器的方案以及无次级聚光器的方案进行了对比。光线追迹仿真模拟结果表明:改进型CPC能够克服普通CPC出射光线发散的缺陷,从而提高与光纤的耦合效率,当主镜接收角度在±0.55°范围内,其耦合效率维持在93.53%-96.43%,该结果优于其他方案。

掺铥光纤激光器设计与仿真

掺铥光纤激光器工作波段在人眼安全波段,凭借其结构紧凑、灵活性高、散热性强、光束质量好、量子效率高等优势得到了越来越多的关注。本研究设计1700~1800 nm波段的光纤激光器,将以泵浦光中心波长786 nm,去激发光纤激光器中心波长1740 nm。其中光纤长度设置为5 m。实验结果表明:泵浦光功率大于5 W时会产生激光,小于5 W时不会产生激光。通过实验可知,泵浦光功率会随光纤长度增长而减小,信号光功率会随光纤长度增大而增大。

LD直接泵浦全光纤激光器输出功率突破20 kW

高功率光纤激光器具有高效率、小体积、低成本、抗回光能力强等突出优点,在工业加工等应用领域中具有明显的竞争优势。近期,国防科技大学基于光纤耦合半导体激光器(LD)直接泵浦的主振荡功率放大器(MOPA)实现了单纤20.27 kW的功率输出。放大器采用纯后向泵浦方案,中心波长1080 nm,光光效率达到84.8%,拉曼散射抑制比大于50 dB。通过优化光纤和器件的设计,可进一步提升激光器的功率和光束质量。

Development and Demonstration of Australian First Working Sodium Guide Star Laser

The Australian first working sodium guide star laser system has been designed and developed for various astronomical and space-related applications. A completely diode-pumped pulsed system was developed initially followed by a largely fiber-based continuous wave (CW) system operating at 589 nm achieved through a unique wavelength conversion scheme by combining 1342 and 1050 nm through a sum frequency generation process. For the CW system, single-mode laser beams at both 1342 and 1050 nm are achieved from fiber-based seed oscillators and fiber amplifiers. The output power of ~25 W at 1342 nm is achieved from a single frequency fiber Raman amplifier. Output power up to 70 W at 1050 nm is achieved from a Yb-doped fiber pre-amplifier followed by a Yb-doped fiber power amplifier. For the sum frequency generation process, optimum focusing parameters are evaluated and determined. The CW system has generated more than 20 W output power at 589 nm, a circularly polarised beam with a good beam quality, spectral linewidth ≤ 2 MHz, and the laser output locked on the sodium D2 line at 589.159 nm. The system has been successfully demonstrated at EOS Space Research Centre, Mt Stromlo, Canberra, and become the Australian first working sodium guide star laser system.

Multi-coupler side-pumped Yb-doped double-clad fiber laser

The side-coupler of angle polished method, using angle-polished multimode fiber and optical adhesive, is used to efficiently pump an Yb-doped double-clad fiber laser. The maximum coupling efficiency of 78.6% is achieved by the side-coupler for a multimode fiber with a circular core of 200μm and a double-clad fiber with a 350/400μm D-shaped inner cladding. While laser diodes (LDs) with three side-couplers are simultaneously used as pump sources, maximum output power of 1.38 W and slope efficiency of 48.9% are demonstrated in the fiber laser system.

Q-switched Er-doped fiber laser with low pumping threshold using graphene saturable absorber

We propose a Q-switched Er-doped fiber laser （EDFL） with a threshold pumping power as low as 7.4 mW, and demonstrate using graphene polyvinyl alcohol （PVA） thin film as a passive saturable absorber （SA）. The SA is fabricated from graphene flakes, which is synthesized by electrochemical exfoliation of graphite at room temperature in 1% sodium dodecyl sulfate aqueous solution. The flakes are mixed with PVA solution to produce a thin film, which is then sandwiched between two ferrules to form a SA and integrated in the EDFL ring cavity to generate a stable Q-switched pulse train. The pulse train operates at 1560 nm with a threshold pump power of 7.4 roW. At maximum 1480 nm pump power of 33.0 roW, the EDFL generates an optical pulse train with a repetition rate of 27.0 kHz and pulse width of 3.56/as. The maximum pulse energy of 39.4 nJ is obtained at a pump power of 14.9 roW. This laser can be used as a simple and low-cost light source for metrology, environmental sensing, and biomedical diagnostics.

3.6-W cryogenic Tm,Ho:YLF laser pumped by fiber-coupled diodes module

In this paper, we report a high power cryogenic cooling Tm(6 at.-%),Ho(0.5 at.-%):YLF laser end-pumped by a 19-fiber-coupled-diodes module with the central wavelength of 792 nm at 20°. The highest continuous-wave power of 3.6 W at 2.051 μm is attained under pumping power of 13.6 W, corresponding to optical-optical conversion efficiency of 26%, and the slope efficiency is larger than 30%. The threshold power is only about 0.16 W because of the long lifetime, large effective emission cross section, and low re-absorption in Tm,Ho:YLF crystal.

Tandem pumping architecture enabled high power random fiberlaser with near-diffraction-limited beam quality

In this contribution, we present the tandem pumping avenue leveraged performance scaling of random fiber laser to record 3 kW level with inherent temporal stability and near-diffraction-limited beam quality. The high power system employs a four-stage master oscillator power amplifier chain. The master oscillator is a half-opened cavity structured random distributed feedback fiber laser centered at 1080 nm and pumped by incoherent amplified spontaneous emission source. Narrowband random laser seed is selected by employing a spectral filtering module with a maximum output power of 1.08 W, full width at half maximum linewidth of 0.47 nm and spectral optical-signal-to-noise ratio of about 42 dB. As to the main amplification stage, for given 104 W pre-amplified random laser seed and 3.61 kW pump laser, an ultimate output power of 3.03 kW can be obtained,corresponding to an optical-to-optical conversion efficiency of 81.05%. Nearly single-transverse-mode amplified random laser can be achieved even at full power level for inherent high thermal modal instability threshold enabled by tandem pumping and inducing bending loss for high-order transverse-mode. Further performance scaling of this high power random laser system, such as power boosting, operation wavelength tuning and linewidth alteration, is the next goal.