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.     

High-power cladding-pumped Tm-doped silica fiber laser with wavelength tuning from 1860 to 2090 nm

A high-power double-clad Tm-doped silica fiber laser, pumped by two beam-shaped and polarization-coupled diode bars at 787 nm, was wavelength tuned by use of an external cavity containing a diffraction grating. The Tm fiber laser produced a maximum output power of 7 W at 1940 nm for 40 W of incident diode power and was tuned over a wavelength range of 230 nm from 1860 to 2090 nm, with >5-W output power over the range 1870-2040 nm. The prospects for further improvement in performance and extension of the tuning range are discussed.     

High-power and highly efficient diode-cladding-pumped Ho3+-doped silica fiber lasers

We demonstrate high-power operation from a singly Ho3+-doped silica fiber laser that is cladding pumped directly with diode lasers operating at 1150 nm. Internal slope efficiencies approaching the Stokes limit were produced, and the maximum output power was 2.2W. This result was achieved using a low Ho3+-ion concentration and La3+-ion codoping, which together limit the transfer of energy between excited Ho3+ ions.     

Multi-peak output Tm-doped silica fiber laser based on femtosecond-written multi-mode fiber Bragg grating

The all-fiber Tm-doped double-clad laser was reported, incorporating a phase mask scanning technology writing FBG directly into the Tm-doped multi-mode fiber core as cavity mirror, using 800 nm femtosecond laser sources. A fiber grating of 12 mm length was realized with a period of 1.35 μm. Pumped by the 793 nm pigtail fiber output LD, the continuous wave (CW) power could scale to 25.4 W at 1.96 μm with the slope efficiency of 38% respected to the LD output power. The output laser spectrum exhibited multi-peak, due to the multi-mode FBG reflective characteristic.     

High-power,high-energy Ho:YAG oscillator pumped by a Tm-doped fiber laser

A high-power, high-energy Ho:YAG oscillator resonantly pumped by a Tm-doped fiber laser is presented. A maximum continuous output power of 38 W with a slope efficiency of 51.9% is achieved at the wavelength of 2.09 μm, and M2≈1.48. In the Q-switching regime, the maximum pulse energy of 12.8 mJ, corresponding to a 514.5 kW peak power, is obtained at the pulse repetition frequency of 1 kHz. Furthermore, the thermal lens effect of the system is studied theoretically, and the radius of the transverse electromagnetic(TEM_(00)) mode of the laser crystal under different pump powers is given.     

Linearly-polarized Tm-doped double-clad fiber laser

We report a linearly polarized Tm doped fiber laser. The fiber laser was set up by using a piece of polarization maintaining Tm doped double clad fiber of 5 m length as gain medium and a polarization beam splitter as a polarization selector. The fiber laser was pumped by a fiber pigtailed laser diode working at 790 nm with a maximum output power of 90 W. The linearly polarized Tm laser operated at wavelength around 2030 nm. A maximum output power up to 21.9 W was achieved when the pump power was 63.27 W with a threshold of 11.92 W, a slope efficiency of about 43.7%, and a polarization extinction ratio of 92.7% (11.37 dB). In addition to the blue fluorescence, we also observed the violet fluorescence under high pump power level. The up-conversion fluorescence was considered to be attributed to the ¹ G ₄ → ³ H ₆, and ¹ D ₂ → ³ F ₄ transitions of Tm ions, respectively.     

Efficient single-axial-mode operation of a Ho:YAG ring laser pumped by a Tm-doped silica fiber laser

Efficient single-frequency operation of a Ho:YAG ring laser at room temperature with a traveling-wave TeO2 acousto-optic modulator to enforce unidirectional operation is reported. By use of a 2-at. % Ho3+-doped 10-mm-long Ho:YAG rod, end pumped by a cladding-pumped tunable Tm-doped silica fiber operating at 1.9 microm, the Ho:YAG ring laser yielded 3.7 W of single-frequency output at 2.1 microm in a diffraction-limited TEM00 beam with M2 < 1.1 for an incident pump power of 8.8 W. The rf power required for unidirectional operation was 0.3 W and corresponded to an increase in cavity loss for the lasing direction (due to diffraction) of only 0.5%. The prospects for further improvement in efficiency are discussed.     

High-power photonic-bandgap fiber laser

An original architecture of an active fiber allowing a nearly diffraction-limited beam to be produced is demonstrated. The active medium is a double-clad large-mode-area photonic-bandgap fiber consisting of a 10,000 ppm by weight Yb(3+)-doped core surrounded by an alternation of high- and low-index layers constituting a cylindrical photonic crystal. The periodic cladding allows the robust propagation of a approximately 200 microm(2) fundamental mode and efficiently discriminates against the high-order modes. The M(2) parameter was measured to be 1.17. A high-power cw laser was built exhibiting 80% slope efficiency above threshold. The robust propagation allows the fiber to be tightly bent. Weak incidence on the slope efficiency was observed with wounding radii as small as 6 cm.     

High-power 83 W holmium-doped silica fiber laser operating with high beam quality

A high-power 83 W cladding-pumped Tm3+-Ho3+-doped silica fiber laser is reported. Using bidirectional 793 nm diode pumping, a maximum slope efficiency of 42% was produced after a threshold launched pump power of 12 W was exceeded. The laser operated at wavelengths near 2105 nm with moderate beam quality, i.e., M2 approximately 1.5. Further power scaling of the fiber laser was limited by thermal failure of the fiber ends.     

高功率窄线宽光纤激光技术

以波长拓展为主线介绍了单频光纤振荡器的研究进展,以功率提升为主线介绍了单频连续光纤放大器的发展现状,以产生窄线宽种子源的方法为依据总结了1 μm波段高功率窄线宽连续光纤激光器的国内外研究成果。分析当前高功率单频光纤激光器和高功率窄线宽光纤激光器的发展趋势和面临的主要挑战,梳理并讨论高功率窄线宽光纤激光的关键技术,并基于当前高功率窄线宽光纤激光器的发展现状介绍其在各领域的应用价值。     

CsPbBr_3 nanocrystal for mode-locking Tm-doped fiber laser

CsPbBr_3 nanocrystal is used as the saturable absorber(SA) for mode-locking Tm-doped fiber laser in a ring fiber cavity.The modulation depth, saturable intensity, and non-saturable loss of the fabricated SA are 14.1%, 2.5 MW/cm~2,and 5.9%, respectively.In the mode-locking operation, the mode-locked pulse train has a repetition rate of 16.6 MHz with pulse width of 24.2 ps.The laser wavelength is centered at 1992.9 nm with 3-dB spectrum width of 2.5 nm.The maximum output power is 110 mW with slope efficiency of 7.1%.Our experiment shows that CsPbBr_3 nanocrystal can be used as an efficient SA in the 2-μm wavelength region.     

色散管理掺铥光纤激光器高能量脉冲的产生

设计了一种基于色散管理的掺铥光纤激光器。通过调节泵浦功率以及腔内偏振态，首先实现了稳定的展宽脉冲输出，中心波长和脉冲宽度分别为1 939.4 nm和482 fs。最大输出功率为15 mW，对应的单脉冲能量为0.52 nJ。增加泵浦功率到645 mW时，通过适当调节偏振控制器可以实现类噪声脉冲锁模，中心波长为1 940.1 nm。所实现的锁模脉冲具有飞秒量级的尖峰以及皮秒量级的基底。最大输出功率为20.4 mW，相对应的单脉冲能量为0.7 nJ。相比于传统孤子，采用色散管理所实现的锁模脉冲具有更高的脉冲能量。此外，所设计的掺铥光纤激光器可作为理想的主振荡功率放大以及啁啾脉冲放大结构的种子源，进一步提高脉冲能量，拓展2 μm高能光纤激光器的实际应用。     

High-power Yb-doped multicore ribbon fiber laser

A highly elongated double-clad ribbon fiber that comprises a pure-silica inner cladding with transverse dimensions of approximately 1.4 mm by 0.23 mm with a linear array of ten ytterbium-doped cores has been fabricated and operated in a simple laser configuration pumped by two diode stacks. The fiber laser yielded 320 W of output power at a center wavelength of 1045 nm in a combined beam with beam propagation factors of approximately 2 (perpendicular to the array) and approximately 150 (parallel to the array) for 576 W of launched pump power. The slope efficiency with respect to absorbed pump power was 62%. The prospects for further power scaling and improved beam quality and efficiency are discussed.     

High-power linearly-polarized tunable Raman fiber laser

In this study, we demonstrate an all-fiber high-power linearly-polarized tunable Raman fiber laser system. An inhouse high-power tunable fiber laser was employed as the pump source. A fiber loop mirror(FLM) serving as a high reflectivity mirror and a flat-cut endface serving as an output coupler were adopted to provide broadband feedback. A piece of 59-m commercial passive fiber was used as the Raman gain medium. The Raman laser had a 27.6 nm tuning range from1112 nm to 1139.6 nm and a maximum output power of 125.3 W, which corresponds to a conversion efficiency of 79.4%.The polarization extinction ratio(PER) at all operational wavelengths was measured to be over 21 d B. To the best of our knowledge, this is the first report on a hundred-watt level linearly-polarized tunable Raman fiber laser.     

High-power continuous-wave cladding-pumped Raman fiber laser

We demonstrate a high-power single-mode cladding-pumped Raman fiber laser. The Raman fiber laser consists of a 1.2 km long germanium-doped double-clad fiber in a linear cavity, which is spliced to a single-mode fiber. The laser is end pumped by a multimode erbium-ytterbium-doped fiber, which is coupled to the inner cladding of the Raman fiber. The embedded core was designed to be single mode at the Raman Stokes wavelength, and up to 10 W of power was obtained at 1660 nm from the single-mode fiber end. The laser has a slope efficiency of 67% and a threshold of 6.5 W.     

227-W output all-fiberized Tm-doped fiber laser at 1908 nm

In this paper, we report that a diode-pumped thulium-doped double clad silica fiber laser can provide powers of up to 227 W at 1908 nm, corresponding to a slope efficiency of 54.3%, and an optical-to-optical efficiency of 51.2%. The output power, to the best of our knowledge, is the highest output at 1908 nm. The beam quality M2 factor is about 1.56. Also discussed in this paper is the dependence of the laser performance on fiber length.     

All-fiber Tm-doped double-clad fiber laser with multi-mode FBG as cavity

An all-fiber LD-clad-pumped Tm-doped fiber laser was reported, and the CW maximal output power reached 24 W at nearly 1.94 μm. The double-clad Tm-doped fiber had a demission of 25/250 μm with the core NA 0.1 and inner-clad NA 0.46. A matched passive multi-mode FBG acted as the front cavity. Cooling by the water, the 56% high slope efficiency was achieved and threshold was 6.4 W, respected to the launched pump power. At the low power pump, the fiber laser spectrum had only one peak at 1.936 μm. Increasing the launched pump power, the output laser wavelength grew to 3–4 peaks. Because the multi-mode FBG reflectivity was not very high, both ends of the fiber laser had laser output power, and the ratio was nearly 10:1.     

基于石墨烯可饱和吸收体的纳秒锁模掺铥光纤激光器

报道了一种基于石墨烯可饱和吸收体的纳秒锁模掺铥光纤激光器.该激光器采用环形腔结构,利用自制的三层石墨烯薄膜作为可饱和吸收体实现锁模.同时在腔内插入一个窄带光纤光栅,约束腔内起振的纵模数,适当调节抽运功率和偏振控制器的角度,得到了重复频率为3.8 MHz、脉宽在3.8—94.3 ns之间灵活可调的2μm纳秒锁模脉冲输出,整个脉宽调节范围超过90 ns.此外,由于获得的兆赫兹纳秒锁模脉冲时间带宽积在49—1119范围内,即存在强烈的啁啾,因而可作为2μm波段啁啾脉冲放大系统中的种子源使用.     

High-power double-clad large-mode-area photonic crystal fiber laser

A high power double-clad ytterbium-doped large-mode-area photonic crystal fiber (LMA PCF) laser was demonstrated using a unique Fabry-Perot (F-P) configuration. The pump source is a fiber coupled diode array operating at 976 nm. A continuous wave (CW) output power of 50 W at ～ 1.04 μm with a slope efficiency of 76.3% is obtained. Single transverse mode operation is achieved without any thermal-optical problems. This laser has the potential for scaling to much higher output power.     

High-power diode-cladding-pumped Tm<Superscript>3+</Superscript>, Ho<Superscript>3+</Superscript>-doped silica fibre laser

The fundamental characteristics of a continuous-wave high-power diode-pumped Tm³⁺, Ho³⁺-doped double-clad silica fibre laser are presented. A maximum output power of 5.2 W was measured and was generated at a slope efficiency of 42 (44)% with respect to the launched (absorbed) pump power. At the optimum length of 7 m (_effL=2.9, where _eff is the effective absorption coefficient of the fibre and L is the fibre length), the fibre laser output was measured to have a centre wavelength of 2105 nm and a line width of 20 nm. The centre wavelength of the emission was tunable over a 32-nm extent when 0.68<_effL<3.28 or for a 6.2-m change in L. PACS 42.55.Wd; 42.55.Xi; 42.60.Lh; 42.60.Pk