Er~(3+)-doped fluorogallate glass for mid-infrared applications

We report an Er3t-doped fluorogallate glass with good thermal and chemical stability. The low maximum phonon energy and high mid-infrared(IR) transmittance of the glass are confirmed by Raman and IR spectra,respectively. Based on Judd–Ofelt theory, intensity parameters and radiative properties are determined from the absorption and emission spectra. The proposed glass possesses a large fluorescence branching ratio β(21.71%) and a maximum stimulated emission cross-section σemof Er3t:4I11∕2→4I13∕2transition at 2.71 μm(1.04 × 10-20cm2). The results indicate that it can be potentially applied in high-power 2.7 μm fiber lasers.     

Efficient 521 nm all-fiber laser: splicing Pr(3+)-doped ZBLAN fiber to end-coated silica fiber

We demonstrated a green all-fiber laser by splicing both ends of a Pr(3+)-doped ZBLAN fiber to silica fibers, whose ends were coated with a dielectric thin film. The output power and the slope efficiency were 322 mW and 53%, respectively, and the coupled pump power of the two blue GaN pump lasers in the silica fiber core was 652 mW. We estimated that the damage threshold of the spliced structure was at least 21 MW/cm2. This splicing technique should be applicable for other wavelengths and glass fibers having low melting temperatures.     

Compact 2 W wavelength-tunable Er:ZBLAN mid-infrared fiber laser

We report a high-power diode-pumped wavelength-tunable (2.7-2.83 mum) erbium-doped ZBLAN mid-infrared fiber laser. Continuous-wave output of >2 W with a spectral linewidth of 1.27 GHz was obtained. Nevertheless, the wavelength-tunable range was found to shrink with increasing pump power. The gain bandwidth narrowing under strong pumping may be ascribed to the enhanced reabsorption process and the weakened population inversion associated with shorter-wavelength emissions.     

Experimental and numerical investigation of mid-infrared laser in Pr~(3+)-doped chalcogenide fiber

We report on a chalcogenide glass fiber doped with Pr~(3+) that can be used for commercialized 1.5-μm and 2-μm laser excitations by emitting broadband 3 μm–5.5 μm fluorescence, which is extruded into a preform and then drawn into a step-index fiber. The spectroscopic properties of the fiber and glass are reported, and the mid-infrared fiber lasers are also numerically investigated. Cascade lasing is employed to increase the inversion population of the upper laser level. The particle swarm approach is applied to optimize the fiber laser parameters. The output power can reach 1.28 W at 4.89-μm wavelength, with a pump power of 5 W, excitation wavelength at 2.04 μm, Pr~(3+) ion concentration at 4.22 × 10~(25) ions/m~3,fiber length at 0.94 m, and fiber background loss at 3 dB/m.     

Co(2+)-doped flatband optical fiber attenuator

The attenuation properties of Co(2+) -doped single-mode optical fibers were experimentally and analytically investigated for preparation of a stable flatband attenuator. By controlling the Co(2+) -doped region in a fiber core, we could prepare a flatband attenuator in which the attenuation in wavelengths 1530-1610 nm was held to within 9.9-10.2 dB (3% variation) and the fluctuation of attenuation was less than 0.1 dB with 1-W input power for 100 h.     

Practical low-noise stretched-pulse Yb(3+)-doped fiber laser

We report on the development of what we consider to be a practical and highly stable stretched-pulse laser based on Yb(3+) -doped silica fiber. The Fabry-Perot cavity uses nonlinear polarization rotation as the mode-locking mechanism, and a semiconductor saturable-absorber mirror to ensure robust self-starting and incorporates a diffraction grating pair to compensate for the normal dispersion of the fiber. Use of a single-mode grating-stabilized telecommunications-qualified pump laser diode ensures reliable, low-noise operation (~0.05% amplitude fluctuations at 10-Hz measurement bandwidth). The laser generates high-quality, 60-pJ pulses of <110-fs duration at a repetition rate of ~54 MHz (3-mW average power).     

Yb~(3+)-doped double-clad fiber laser with all fiber cavity

A novel all fiber cavity Yb~(3+)-doped double-clad fiber laser (DCFL) based on two double-clad fiber (DCF) Bragg grating is presented. The fiber Bragg gratings (FBGs) as the input and output mirrors have been formed in Yb~(3+)-doped DCF with the phase-mask method, and their reflectivities are 99% and 22%, respectively. When the input pump power is 417 mW, the maximum output power is 144 mW with linewidth <0.1 nm at the wavelength of 1.057 μm, over 40-dB signal-to-noise ratio (SNR), and 50.8% slope efficiency.     

Multi-photon upconversion luminescence of Er~(3+)-doped Y_2O_3 nanocrystals

Visible upconversion emission intensities are investigated in Er3＋-doped Y203 nanocrystals. We also find that the upconversion intensity varies nonlinearly with the excitation power with a threshold of 110 mW, which indicates that the green and red emissions would be photon avalanche upconversion when the excitation power exceeds the threshold.     

Er~(3+)-Yb~(3+) codoped borosilicate glass for optical thermometry

Infrared to green up-conversion emissions centered at the wavelengths of about 524 and 550 nm of the Er3+-Yb3+ codoped borosilicate glass are recorded,using a 978 nm semiconductor laser diode(LD) as an excitation source.The fluorescence intensity ratio(FIR) of the green up-conversion emissions at about 524 and 550 nm in the Er3+-Yb3+ codoped borosilicate glass has been studied as a function of temperature over the temperature range of 295-873 K.The maximum sensitivity and the temperature resolution derived ...     

被动谐波锁模Er3+/Yb3+共掺双包层光纤环形腔激光器

为了实现高重复频率和高功率的光脉冲,实验采用Er3+/Yb3+共掺双包层光纤作为增益介质,稳定的中心波长为976 nm的高功率半导体激光器作为泵浦源,利用非线性偏振旋转锁模技术,得到稳定的自起振锁模光脉冲。当泵浦功率为2.4 W时,激光器输出重复频率为8.829 MHz的连续锁模光脉冲,平均输出功率为52.5 mW,自起振锁模泵浦阈值功率为0.6 W,并观测到了稳定的高阶谐波锁模、调Q和调Q-锁模光脉冲输出。     

Spectral analysis of short-wavelength emission by up-conversion in a Tm~(3+):ZBLAN dual-diode-pumped optical fiber

The fluorescence evolution along Tm3+-doped Zr F4–Ba F2–La F3–Al F3–Na F(ZBLAN) optical fibers, as well as amplified spontaneous emission in the UV-IR region with emphasis on 350 nm, 365 nm, and 450 nm, is studied,estimating optimal fiber lengths for amplification within the region. The fibers were diode-pumped with single and double lines(687 and/or 645 nm). Double-line pumping presents a quite superior efficiency for producing UV-blue signals with the benefit of requiring very short fibers, around 20 cm, compared to single-line pumping requiring more than 50 cm. A virtual cycle in which the pumps enhance each other's absorption is the key to these systems.     

Up-conversion luminescence tuning in Er~(3+) -doped ceramic glass by femtosecond laser pulse at different laser powers

The up-conversion luminescence tuning of rare-earth ions is an important research topic for understanding luminescence mechanisms and promoting related applications. In this paper, we experimentally study the up-conversion luminescence tuning of Er~(3+)-doped ceramic glass excited by the unshaped, V-shaped and cosine-shaped femtosecond laser field with different laser powers. The results show that green and red up-conversion luminescence can be effectively tuned by varying the power or spectral phase of the femtosecond laser field. We further analyze the up-conversion luminescence tuning mechanism by considering different excitation processes, including single-photon absorption(SPA), two-photon absorption(TPA), excited state absorption(ESA), and energy transfer up-conversion(ETU). The relative weight of TPA in the whole excitation process can increase with the increase of the laser power, thereby enhancing the intensity ratio between green and red luminescence(I_(547)/I_(656)). However, the second ETU(ETU2) process can generate red luminescence and reduce the green and red luminescence intensity ratio I_(547)/I_(656), while the third ESA(ESA3) process can produce green luminescence and enhance its control efficiency. Moreover, the up-conversion luminescence tuning mechanism is further validated by observing the up-conversion luminescence intensity, depending on the laser power and the down-conversion luminescence spectrum under the excitation of 400-nm femtosecond laser pulse. These studies can present a clear physical picture that enables us to understand the up-conversion luminescence tuning mechanism in rare-earth ions, and can also provide an opportunity to tune up-conversion luminescence to promote its related applications.     

掺Er3+氟化物光纤振荡器中红外超短脉冲的产生

基于非线性薛定谔方程建立了氟化物(ZrF₄-BaF₂-LaF₃-AlF₃-NaF, ZBLAN)光纤振荡器中产生中红外超短脉冲的理论模型, 在此基础上研究了中红外超短脉冲在氟化物光纤振荡器中形成的物理机理, 数值模拟了氟化物光纤振荡器中中红外超短脉冲的演化过程. 分析了腔内净色散和小信号增益系数对振荡器中锁模脉冲产生的影响, 并给出了参数设置范围. 研究发现: 当掺Er³⁺氟化物光纤长度, 小信号增益系数, 不饱和损耗为一定值时, 腔内净色散在一定范围内才会出现稳定的锁模脉冲, 且随着腔内净色散增加脉冲宽度变宽, 光谱变窄, 峰值功率降低; 当掺Er³⁺氟化物光纤长度及不饱和损耗一定, 腔内净色散量为合理值, 小信号增益系数在合理的范围时可以得到稳定的锁模脉冲, 且随着小信号增益系数的增加脉冲宽度变宽, 光谱变宽, 峰值功率增加.     

Er~(3+),Yb~(3+):glass-Co~(2+):MgAl_2O_4 diffusion bonded passively Q-switched laser

A Co~(2+):spinel passively Q-switched erbium-ytterbium-phosphate glass bonded laser pumped at 940 nm is reported.A pulse energy of 210 μJ, a peak power over 70 kW, and beam quality M~2 parameter of 1.2 are obtained under a pump power of 235 mW. An unbonded laser output experiment with the same dimension of the active material and the saturable absorber as the bonded laser output experiment is carried out. The reason why the output in the bonded laser is improved is determined.     

One-color one-beam pumping of Er(3+)-doped ZBLAN glasses for a three-dimensional two-step excitation display

We demonstrate a one-color one-beam pumping method for a three-dimensional two-step excitation fluorescent display with Er(3+) -doped ZBLAN glass. A localized green fluorescent spot is obtained by use of a focused pump-light beam at 979 nm. The quantum efficiency of the two-step excitation fluorescence is investigated in a time-dependent analysis and an experiment with a pulsed pump light.     

Stable high-power continuous-wave Yb(3+)-doped silica fiber laser utilizing a point-by-point inscribed fiber Bragg grating

We report on a narrowband 5 W cw fiber laser incorporating a point-by-point fiber Bragg grating inscribed into the core of a Yb(3+)-doped double-clad fiber. The laser featured excellent long-term wavelength and power stability (0.3%), as well as a very narrow (15 pm) linewidth, when passive temperature stabilization of the grating was implemented.     

Er^3＋／Yb^3＋掺杂全光纤环形激光器

本文报道利用Er~(3+)/Yb~(3+)掺杂单模光纤首次研制成功的环形谐振腔结构的可调谐(调谐范围宽于70nm)全光纤激光器的设计原理及其实验结果.     

Temperature dependence of spectral and laser properties of Er~(3+)/Al~(3+) co-doped aluminosilicate fiber

Using a heavily erbium-doped aluminosilicate fiber prepared by the sol-gel method combined with high temperature sintering, the temperature dependence of the spectrum around the 1.55 nm band and single-mode fiber laser properties were investigated, respectively. The absorption cross section increases 29.2% at ～1558 nm with the temperature increasing from 20°C to 140°C, while the emission cross section slightly increases4.3%. In addition, the laser slope of the heavily erbium-doped aluminosilicate fiber at 1558 nm decreases4.4% from 10.8% to 6.4% with the temperature increasing from 18°C to 440°C. Meanwhile, an experiment lasting3 h proves that the fiber laser has excellent stability below 440°C.     

Power scaling method for 2-microm diode-cladding-pumped Tm(3+)-doped silica fiber lasers that uses Yb(3+) codoping

Unidirectional dual-wavelength pumping at 805 and 975 nm of a Tm(3+)-doped silica double-clad fiber laser that has been codoped with Yb(3+) is demonstrated. With equal 2-wt. % concentrations of the Tm(3+) and Yb(3+) ions, slope efficiencies of 49% (57%) and 35% (40%) with respect to the launched (absorbed) pump power of the 805- and 975-nm pump wavelengths, respectively, were obtained. Efficient Yb(3+) --> Tm(3+) energy transfer and efficient cross relaxation combined with minimal upconversion losses were thus operating. At the maximum output power of 18 W, the fiber laser operated at a center wavelength of 2050 nm.     

Three-level all-fiber laser at 915 nm based on polarization-maintaining Nd~(3+)-doped silica fiber

Nd3+-doped fiber lasers at around 900 nm based on the 4F3/2→4I9/2 transition have obtained much research attention since they can be used as the laser sources for generating pure blue fiber lasers through the frequency doubling.Here,an all-fiber laser at 915 nm was realized by polarization-maintaining Nd3+-doped silica fiber.A net gain per unit length of up to 1.0 dB/cm at 915 nm was obtained from a 4.5 cm fiber,which to our best knowledge is the highest gain coefficient reported in this kind of silica fiber.The optical-to-optical conversion efficiency varies with the active fiber length and the reflectivity of the output fiber Bragg grating(FBG),presenting an optimal value of 5.3%at 5.1 cm fiber length and 70%reflectivity of the low reflection FBG.Additionally,the linear distributed Bragg reflector short cavity was constructed to explore its potential in realizing single-frequency 915 nm fiber laser.The measurement result of longitudinal-mode properties shows it is still multi-longitudinal mode laser operation with 40 mm laser cavity.These results indicate that the Nd3+-doped silica fiber could be used to realize all-fiber laser at 915 nm,which presents potential to be the seed source of high-power fiber laser.