High efficient Tm3+ doped double cladding silica fiber laser with an intracavity biconical taper

A high efficient LD (laser diode) pumped Tm³⁺ doped double clad silica fiber laser with an intravacity biconical taper was reported. A biconical taper located ～3 cm from the output end of the fiber laser was fabricated by heating and stretching method with a length 1.5 cm and waist diameter ～20 µm. The slope efficiency was 49.8% with respected to the launched pump power, and the maximum output power was 1.97 W. Pre and post output laser power ratio was ～10. This fiber laser was compared with other three biconical tapered fiber lasers (the same fiber with different tapers) and a uniform geometry fiber laser. With intracavity biconical tapers, fiber lasers’ thresholds were ～1 W higher than the fiber laser without the taper (1.97 W). The pump end’s slope efficiencies of fiber lasers with tapers were 3–5% in contrast with 37.6% of the uniform one. After tapered, the pre and post laser power ratios were much higher than the un-tapered one’s, but not changed much with the launched pump power.     

Power scaling of Tm3+ doped ZBLAN blue upconversion fiber lasers: modeling and experiments

Power scaling of Tm³⁺ doped ZBLAN blue upconversion fiber lasers was investigated by a simple model. Based on our experimental results on blue fiber lasers, we discuss the effects of photodegradation and photocuring, fiber length, the reflectivity of the coupler mirror and fiber core diameter on further enhancement of blue fiber laser, respectively. The optimal parameters (including fiber length, fiber core diameter and the reflectivity of the coupler mirror) for the operation of high power (>1 W) blue fiber laser were presented through simple numerical simulations, which are valuable for the future design of high power blue upconversion fiber laser. PACS 42.55.Wd; 42.60. Lh     

Tm3+/Ho3+共掺碲酸盐微结构光纤激光器

用棒管法拉制了Tm³⁺/Ho³⁺掺杂的碲酸盐微结构光纤,并获得了2 μm的激光输出。以1 560 nm的Er³⁺掺杂石英光纤激光器作为泵浦源,在22 cm长的微结构光纤中,得到了最大功率为8.34 mW、波长为2 065 nm的连续激光输出,泵浦光功率为507 mW,斜率效率为2.97%。研究结果表明,Tm³⁺/Ho³⁺共掺碲酸盐微结构光纤是一种用于研制2 μm激光器的理想材料。     

High-power multi-mode laser to single-mode pump conversion

A novel pump-sharing module for multi-channel amplifiers based on integration of high-power multimode semiconductor lasers and planar waveguide circuits is proposed. The feedback-free modules are designed for optimum coupling, throughput and power uniformity on silicon using BPM method and fabricated via the sol-gel process of photo patternable precursors. Modal properties of the multimode lasers are considered by studying spectrum and spatial distribution of laser output power at different temperatures. Employing an 1500 mW 980 nm multimode laser (TE polarized), via lens and Butt coupling up to 1250 mW of laser output is coupled into the multimode channel waveguides, which are tapered and branched to four single mode waveguides. The measured pump power from splitter outputs, randomly polarized, exceeds 600 mW. At constant temperatures ranging from 22 °C to 30 °C, the pump-sharing modules exhibit good stability with a power uniformity of <0.5 dB over hours.     

LD-clad-pumped nanosecond Tm<Superscript>3+</Superscript> doped silica fiber amplifier at 1.99 μm

ALD-clad-pumped nanosecond Tm³⁺ doped silica fiber amplifier was reported that provided up to a 2-W average power output with a slope efficiency of 48.6% with respect to the absorbed pumped power. The input signal central wavelength was at 1.99 μm, with a 119.5-ns pulse duration and 5-kHz repeat rates. The pump sources were a 793-nm LD output with a 400-μm pigtail fiber. The gain fiber was D-shaped Tm³⁺ doped silica double-clad fiber with a diameter of 27.5/400 μm. The output amplified pulse and spectrum were in accordance with the input signal. This is the first report to the authors’ knowledge on the general experimental investigation of a LD-clad-pumped Tm³⁺ doped silica nanosecond-fiber amplifier at 1.99 μm.     

光纤光栅选频掺Yb3+双包层光纤激光器

利用相位掩模法，在D形内包层掺Yb3+双包层光纤一端直接写制出Bragg光栅，用作双包层光纤激光器的输出腔镜.试验得到了线宽为0.196nm，波长为1058.2nm，最高输出功率为570mW的稳定激光输出，解决了激光器中模式竞争造成的输出不稳定现象.从速率方程出发，对激光器的输出功率与抽运功率、光栅反射率的关系以及最佳光纤长度进行了理论分析，结果与实验符合很好. 关键词： 双包层光纤光栅 掺Yb3＋双包层光纤激光器 相位掩模 速率方程     

All-fiber clad-pumped Tm3+-doped fiber amplifier using high power fiber combiner

The diode laser (LD) clad-pumped 1947.6 nm continuous wave (CW) Tm³⁺-doped fiber amplifier is reported using the master oscillation power amplifier (MOPA) method. The injected seed laser is provided by an all-fiber LD-clad-pumped Tm³⁺-doped single-mode fiber laser, which has a nearly 2.4 W maximal output power and 0.1 nm ultra-narrow linewidth based on the intracore reflection FBG. Using the 25/400 μm double-clad LMA Tm³⁺-doped fiber as the gain fiber, the output maximal output power is 30.6 W from the fiber amplifier, with a slope efficiency of 39.1% respected to the LD total output power. A high power multi-mode fiber combiner is used to couple high power LD light into the gain fiber. The output wavelength is also located at 1947.6 nm, with the slightly expanded laser linewidth of 0.2 nm.     

石英基掺Tm3+包层抽运光纤激光器

在MCVD车床上利用“湿法”掺杂方法研制出纤芯高掺Ge的石英基掺Tm³⁺光纤预制棒,采用侧面研磨和抛光工艺制成横截面为正六边形的光纤预制棒.经拉丝,内层涂覆低折射率材料后制成包层抽运光纤.测试其吸收谱,并对光纤参数进行优化.通过在光纤两端紫外写入光纤Bragg光栅,制成线形光学谐振腔,在工作波长793nm的激光抽运下,获得工作波长1947.1031nm、功率2.05W的激光输出.由此证明这种光纤具有优异的光学特性. 关键词： 3+光纤')" href="#">石英基掺Tm³⁺光纤 光纤Bragg光栅 包层抽运 光纤激光器     

Top-hat beam Tm<Superscript>3+</Superscript>-doped fiber laser using an intracavity abrupt taper

The top-hat beam clad-pumped Tm³⁺-doped fiber laser was realized simply using an intracavity multi-mode abrupt taper. The ratio of the flat-top diameter to the spot diameter reaches 53%, with a small intensity variation less than 6%, and the top-hat beam’s half-divergence angle is only 5.3°. The fiber laser has a maximal output power of 5 W with slope efficiency of 39.7%, pumped by the 792 nm diode laser (LD). The abrupt taper is directly made on the multi-mode double-clad Tm³⁺-doped fiber near the fiber laser output end with the 0.45 ratio of taper waist diameter to fiber clad diameter, and this fiber end 4% Fresnel reflection is used to be the output coupler. The fiber laser’s high reflective coupler is an intracore multi-mode FBG, which is directly written into the multi-mode Tm³⁺-doped fiber core using femtosecond laser and phase mask, at the other fiber end. The abrupt taper has no obviously influence on the fiber laser output power, and the output laser spectrum.     

Tapered diode lasers and laser modules near 635nm with efficient fiber coupling for flying-spot display applications

Flying-spot displays require light sources in the red, green and blue with a high optical output power and nearly diffraction limited beams. In this paper we present experimental results of red-emitting, AlGaInP based, tapered diode lasers and their integration into diode laser modules. The laser modules emit a collimated, almost diffraction limited beam with an optical output power as high as 1W at a wavelength close to 635 nm. The tapered laser chips were designed with emphasis on achieving a good beam quality in vertical and lateral directions of a collimated beam. To test the suitability for flying-spot display applications, we performed fiber coupling experiments with a low mode number optical fiber with an etendue as low as 6 × 10^?6 mm² sr. A maximum transmission of 70% of the launched power behind the uncoated fiber as well as a usable power in excess of 580mW were measured.     

Comparative study of continuous wave Tm<Superscript>3+</Superscript>-doped silica and fluoride fiber lasers

We compare Tm³⁺-doped silica and fluoride fiber lasers in continuous wave operation using the same experimental setup. For incident pump powers of up to 50 W, the fluoride fiber is shown to have higher output power and efficiency compared to silica and reaches a maximum output power of 20 W at 1.94 μm. A slope efficiency of 49% (41%) and a maximum optical-to-optical efficiency of 45% (35%) at an incident pump power of 25 W (37 W) were determined for the fluoride (silica) fibers, respectively. These optical-to-optical efficiencies are the highest reported for directly diode-pumped Tm³⁺-based fiber lasers. We establish that in free-running mode, fiber lasers using fluoride glass are temporally more stable than fiber lasers using a silica host. PACS 42.55.Wd; 42.55.Xi; 42.60.Mi; 42.70.Hj     

Double-clad Tm3+-doped silica fiber laser with Bragg grating inscribed directly into active core by femtosecond laser

We report for the first time to inscribe the Fiber Bragg Grating (FBG) in Tm³⁺-doped multimode double-clad silica fiber by 800 nm femtosecond laser with a phase mask. The 1.35 μm period Bragg grating is written into the fiber core, which is responded to the laser center wavelength located at nearly 1960 nm. Continuous wave total output power of 11.5 W is obtained under the launched pump power of 29.8 W, corresponding to a slope efficiency of 45.0% and a conversion efficiency of 38.6%.     

全光纤超短脉冲掺Yb3+光纤环形激光器

讨论了自启动被动锁模掺Yb³⁺光纤环形激光器产生短脉冲的机理，并研制出全光纤结构超短脉冲掺Yb³⁺光纤环形激光器.采用两个976nm半导体激光器级联抽运作为抽运源，高掺杂浓度掺Yb³⁺光纤作为增益介质，利用光纤的非线性偏振旋转效应，得到自启动、十分稳定的ps量级锁模光脉冲.激光器锁模阈值功率260mW，输出功率25mW，锁模光脉冲中心波长1056nm，3dB带宽11.7nm，重复频率20MHz.与其他结构光纤激光器相比，这种全光纤结构具有更高的效率和更好的稳定性. 关键词： 环形光纤激光器 3+光纤')" href="#">高掺杂浓度掺Yb³⁺光纤 自启动 被动锁模     

石英基掺Tm3+光纤激光器特性的理论分析

基于速率方程理论建立了石英基掺Tm³⁺光纤激光器³H₆—³H₄抽运方式的理论模型,采用龙格-库塔 (Runge-Kutta) 法对该模型进行了数值分析,得出抽运光与激光功率在掺Tm³⁺光纤中的分布特性,并对Tm³⁺光纤长度、Tm³⁺的掺杂浓度等因素对掺Tm³⁺光纤激光器性能的影响进行 关键词： 3+光纤激光器')" href="#">石英基掺Tm³⁺光纤激光器 龙格-库塔法 抽运效率 掺杂浓度     

CW single transverse mode all-fiber Tm3+-doped silica fiber laser

The CW 25.6 W output power with a slope efficiency of 30.6% respected to the pump power from a CW single transverse mode all-fiber Tm³⁺-doped Silica Fiber Laser is reported. The all-fiber laser is made up by progressively splicing the pigtail fiber, matched FBG fiber and Tm fiber. The reflective FBG and Tm³⁺-doped fiber end Fresnel reflection build up the laser resonance cavity. Due to the multi-mode FBG as the reflective mirror, the output laser spectrum is multi-peaks at high output power, but the spectrum width is less than 2 nm at 1.94 μm. We estimate the beam quality to be M ² = 2.39, clearly indicating nearly diffraction-limited beam propagation.     

Low-cost low-threshold diode end-pumped Tm:YAG laser at 2.016?μm

We report a low-threshold continuous-wave Tm:YAG laser that can be excited near 785?nm with low-cost, single-mode AlGaAs laser diodes. Low-threshold operation was achieved using a tightly focused, astigmatically compensated x-cavity containing a 2-mm-thick Tm:YAG crystal with 5?% Tm³⁺ concentration. Two linearly polarized single-mode diodes operating at 785.8?nm were polarization coupled to end pump the resonator. With a 6?% output coupler, as high as 32?mW of output power could be obtained at 2016?nm with 184?mW of incident pump power. The output could be further tuned in the 1935?C2035?nm range. Slope efficiency measurements indicated that cross-relaxation was very effective at this doping level. With a 2?% output coupler, lasing could be obtained with as low as 32.3?mW of pump power. In the limit of vanishing output coupling, the incident threshold pump power could be reduced to as low as 25?mW. To our knowledge, this is among the lowest lasing thresholds reported to date for continuous-wave, room-temperature thulium lasers.     

被动锁模Yb3+光纤环形腔激光器的研究

 采用974 nm半导体激光器作为泵浦源，超高掺杂Yb³⁺光纤作为增益介质，利用光纤的非线性偏振旋转效应，得到稳定的ps量级锁模光脉冲。泵浦功率220 mW时，激光器锁模阈值功率150 mW，输出功率26 mW，锁模光脉冲中心波长1 046 nm，3 dB带宽6.01 nm，20 dB带宽16 nm，脉宽22 ps，重复频率20 MHz。与同类光纤激光器相比，该激光器输出功率高，具有更好的稳定性。     

钛宝石激光抽运的被动锁模Tm:YAG陶瓷激光实验研究

本文采用连续钛宝石激光作抽运,掺杂浓度为6 at.%、长度为2.7 mm的Tm:YAG陶瓷作增益介质,通过引入半导体饱和吸收体获得了稳定的被动锁模运转.实验中获得的激光锁模功率为116.5 mW,中心波长为2007 nm,重复频率为109 MHz,通过自行搭建的腔外非共线强度自相关测量得到的脉冲宽度是55 ps.     

650-nm laser emission under upconversion pumping at 1.064 μm in Tm<Superscript>+3</Superscript>: ZBLAN fiber laser

We report for the first time continuous wave (CW) red laser emission in Tm⁺³-doped ZBLAN fiber laser, operated at 650 nm (¹ G ₄ → ³ F ₄ transition of Tm⁺³). The excitation uses a three step upconversion scheme. The pump source is a Nd:YAG laser operated at 1.064 μm. A laser output power of CW 80 mW was obtained for 1.42 W of launched pump power. The slope efficiency with respect to launched pump power was measured to be 7.7%. The temporal behavior of the emitted laser is also addressed.