Blue Up-Conversion Fibre Laser Pumped by a ll20-nm Raman Fibre Laser

A Tm^3 -doped ZrF4-BaF2-LaF3 AlF3-NaF (ZBLAN) fibre up-conversion laser pumped by a 1120-nm Raman fibre laser is demonstrated with blue output power levels up to 116mW. For the output mirror with 80^ reflectivity, the slope efficiency is about 15%, the optical-to-optical conversion efficiency is 11%, and the maximum un-saturated output power is 116mW. For 60% reflectivity, the slope efficiency is about 18% and the opticalto-optical conversion efficiency is 12%, whilst the maximum saturated output power is about 80roW due to the existence of photo-degradation effect in Tm^3 doped ZBLAN glass fibre.     

A 980 nm Yb-doped single-mode fibre laser with 946 nm Nd:YAG laser as pump source

Based on rate equations,this paper gives expressions of the output power,the pump power threshold,the slope efficiency,the fibre optimal length and the laser gain of a quasi-three-level Yb-doped fibre laser.The gain relationship between quasi-three-level system and four-level system is also given,which provides a theoretical basis for suppressing the four-level transmissions.In the experiment,we adopt the backward pumping configuration and use a linear cavity.The Yb-doped fibre laser has an output power of 372 mW of single-mode laser emission at 980 nm with a slope efficiency of 21.2% when the fibre length is 29.5 cm close to an optimal fibre length in theory.The experimental results accord well with the theoretical analyses.     

Lasing Characteristics of Tm^3＋：Ho^3＋ Codoped Silica Fibre Laser Pumped by 1.18-μm Raman Fibre Laser

The fundamental characteristics of Fabry-Perot-cavity continuous-wave Tm-Ho codoped silica fibre lasers pumped by a 1.18μm Raman fibre laser are presented. A maximum output power of 930mW at 1880nm is generated for a fibre length of 1 m from the transition of Tm^3 , with a slope efficiency of 32.4%. For a 3-m-long fibre, the maximum output power decreases to 650 mW at 1960 nm due to the laser emission from Ho^3 with a lower slope efficiency of 25%, which clearly shows the effective energy transfer from Tm^3 to Ho^3 . The wavelength redshifting of the laser emission originates from the transition competition and the emission cross section difference between Tm^3 and Ho^3 .     

Laser Characteristics of Cladding-Pumped Short Er^3＋/yb^3＋ Codoped Single Mode Phosphate Glass Fibre

We experimentally investigate the laser characteristics of a series of short pieces of newly-developed Er^3＋/ Yb^3＋ codoped single mode phosphate glass fibres via the cladding pump of a 976nm multimode laser diode. A stable continuous-wave single transverse mode laser with over 85 m W at 1553nm is generated from a 5.5-em-long active fibre. Single mode laser output power per unit length is up to 15 mW/cm. Moreover, the slope efficiency is 11.8% when the pump power is below 940mW and the 3dB linewidth is 0.06nm at the maximum pump power. The numerical simulation results show that the laser emission slope efficiency can exceed 20% by means of increasing the coupling efficiency of the pump to the fibre core further.     

Experimental and Numerical Analysis of a Two—Order Cascaded Raman Fibre Laser

A two-order cascaded Raman fibre laser based on GeO2-SiO2 fibre and fibre Bragg gratings is fabricated.output power 309mW of the second Stockes light around 1176.2nm is obtained with a slope efficiency of 45.3%.The experimental results agree well with the simulation results obtained by using the double-pass model.     

High Efficiency Continuous-Wave Tm：Ho：GdVO4 Laser Pumped by a Diode

We report a high efficiency cw diode-pumped cryogenic Tin(Sat.%), Ho(0.5at.%):GdV04 laser. The pumping source is a fibre-coupled laser diode with fibre core diameter of 0.4 mm and numerical aperture of 0.3, supplying power 14.8 W at 793.6nm. For input pump power of 13.6 W at 794.2nm, the maximum output power of 4.2 W,optical-to-optical conversion efficiency of 31% and slope efficiency 38% have been attained at 2.0485 μm. To our knowledge, the operating performance is the best among the previously reported Tm:Ho:GdVO4 lasers. We also analyse the influence of pump wavelengths (from 792nm to 794.2nm) on the output power, the optical-to-optical conversion efficiency increases with the longer pump wavelength which is closer to the absorption peak of 797nm in Tm,Ho:GdV04.     

A l15-W Ytterbium-Doped Fibre Laser

We report a highly efficient ytterbium-doped double-clad fibre laser, one-end pumped by a 975-nm diode stacksource and generating up to 115.6 W of cw output power at 1.1 μm. The maximum optical-to-optical conversionefficiency with respect to the launched pump power is 79% at 65-W output power, and the overall slope efficiencyis about 69%.     

150-W Tm3+-Doped Fiber Lasers With Different Cooling Techniques and Output Couplings

A home-made double-clad Tm3＋ -doped silica fiber laser with over 150-W output power is reported. Pumped with a diode bar at 793nm, the fiber laser is operated at 2.04μm with a slope efficiency of 56.3%. A quantum efficiency of 〉 140% is achieved owing to the efficient cross-relaxation process in heavily Tm3＋-doped fibers. By using different fiber-cooling techniques, the slope efficiency shows a deviation over 10%. The influence of output coupling on the laser characteristics is also investigated.     

Diode-pumped high-efficiency broadband tunable Tm:YAP laser

A laser diode-pumped high-efficiency widely tunable Tm:YAP laser with excellent comprehensive properties is reported.The output power is stable at a given pump power.Under the absorbed pump power of 12.95 W,the maximum output power at 2,010 nm is 5.16 W,corresponding to a slope efficiency of 45.5%.The generated beam profile is close to the Gaussian TEM00 near the maximum pump power.Furthermore,the laser working wavelength can be continuously tuned through optimization from 1,894 to 2,066 nm,which is the widest tunable range for Tm:YAP lasers to date.     

The LD-Cladding-Pumped High Power Tm^3＋ -doped Silica Fibre Amplifying at Approximately 1.99 μm

A laser diode （LD） cladding-pumped cw Tm^3＋ -doped silica fibre amplifier is reported that provides up to 3 W output with the slope efficiency nearly 30%. The gain fibre is 27.5/400μm D-shaped Tm^3＋ -doped silica double- cladding fibre, and the input signal sources is an LD-pumped Tm^3＋：YAP lasing at 1.99μm. The measured amplified spectrum only stretches a little relative to the input signal spectrum. This is the first report to the authors＇ knowledge of general experimental investigation of cladding-pumped Tm^3＋ -doped fibre amplifier of high power cw at 1.99μm.     

Performance of a liquid-nitrogen-cooled CW Tm, HorYLF laser

A liquid-nitrogen-cooled Tm, Ho:YLF laser is constructed with a 10-mm-long Tm(6%) and Ho(0.5%) co-doped yttrium lithium fluoride crystal pumped by a laser diode operating at 792 nm. The laser output power is improved by cooling the Tm, Ho:YLF crystal from 300 to 77 K. When the crystal is kept at 77 K, the laser threshold pump power is 230 mW, the slope efficiency is 27.4%, and the maximum optical-to-optical efficiency is 19.9%. At the same time, the relation between the input power and the output power at different temperatures is obtained.     

A Diode-Pumped 1617 nm Single Longitudinal Mode Er：YAG Laser with Intra-Cavity Etalons

We demonstrate the continuous wave p-polarized single longitudinal mode （SLM） operation of an Er：YAG laser at 1617.6nm pumped by a diode-laser with three inserted Fabry-Perot （FP） etalons at room temperature. The Brewster angle inserted FP is applied to obtain the p-polarized laser. For free running, the maximum output power is 570 m W with a pump power of 12.5 W. An incident pump power of 12.5 W is used to generate the maximum p-polarized single longitudinal mode output power of 78.5 m W, corresponding to a slope efficiency of 1.6% and an optical-to-optical efficiency of 0.61%. The beam quality M2 is measured to be 1.15 at the highest SLM output power. This stable polarized SLM oscillation is encouraging due to its application for an injection-locked system used as a master laser.     

Experimental Investigation of Tm3＋-Doped Silica Double-Cladding Fibre Laser

Using a Tm^3＋-doped double-cladding silica fibre, we produce a maximum cw 2.2 W output at approximately 2μm. The highest achieved slope efficiency is 29.3% respect to the launched pump power. The lowest threshold is 1.85 W using the double pass pump method with the fibre length 2. 7m, which is the lowest reported threshold of cladding pump of the ^3H4 level. The fibre laser output peak wavelength ranges from 1.967μm to 2.018μm with cavity 1 （R1 = 1 and R2=0.04） and from 1.95μm to 1.99μm with cavity 2 （R1=0.04 and R2=0.04）, as the fibre length varies.     

LD-pumped 6 W cw Tm^3＋-Doped Silica Double-Cladding Fibre Laser

We report a thulium-doped silica fibre laser that generates a maximum cw output power of 6 W in a 2 μm wavelength range when cladding-pumped by a laser diode （LD） operating at approximately 791 nm at room temperature. The slope efficiency with respect to the launched pump power is 50% and 38.4%, with and without an output coupler mirror, respectively. The corresponding thresholds are 2.8 W and 4.8 W, respectively. The beam qualities Mx^2 and My^2 are 1.26 and 1.32, respectively. The experimental results are also analysed.     

All-Fibre Ytterbium-Doped Photonic Crystal Fibre Laser with High Efficiency

A double-cladding ytterbium-doped photonic crystal fibre （PCF） with a 350-μm^2 effective area is fabricated. The measurement results show that the PCF has high absorption peak at 915 nm. Its fluorescence lifetime is 840μs. Laser experiments with all-fibre configurations are carried out with this fibre. A continuous-wave output power of 3.96 W is achieved with a 5.2 W launched pump power. The central wavelength of the output spectrum is 1080.22nm. The results show that the PCF laser has a high slope efficiency of 79.6% and light conversion efficiency of 76.2%.     

A Stable Diffusion-Bonded Tm：YLF Bulk Laser with High Power Output at a Wavelength of 1889.5 nm

A high power diode-pumped diffusion-bonded Tm：YLF laser operating at 1889.5nm with a FWHM linewidth of less than 0.1 nm is reported. A Brewster plate and two Fabry-Perot etalons are inserted in the laser cavity for spectral narrowing and stabilization. Under an incident pump power of 136.8 W, 46.1 W of output power is achieved, corresponding to an optical-to-optical conversion efficiency of 33.7% and a slope efficiency of 42.8%. The laser wavelength shift of only 0.07nm with the incident pump power from 20.1 W to 136.8W is observed. The M2 factor at maximum output power is calculated to be 2.3 in the x-axis and 2.0 in the y-axis, respectively.     

Compact, Low Threshold Nd^3＋：YVO4 Self-Raman Laser at 1178 nm

A compact low-threshold Raman laser at 1178 nm is experimentally realized by using a diode-end-pumped actively Q-switched Nd^3＋ ：YVO4 self-Raman laser. The threshold is 370mW at a pulse repetition frequency of S kHz. The maximum Raman laser output is 182 m W with the pulse duration smaller than 20 ns at a pulse repetition frequency of 30kHz with 1.8 W incident power. The optical efficiency from the incident power to the Raman laser is 10% and the slope efficiency is 13.5%.     

Theoretical study and optimization of a high power mid-infrared erbium-doped ZBLAN fibre laser

Based on the rate equations describing the erbium-doped fluoride glass(ZBLAN) fibre lasers with different pumping configurations being taken into account,this paper presents theoretical calculations related to the dynamic population density and the operation performance of a high power mid-infrared all-fibre erbium-doped ZBLAN fibre laser.It shows that the ground-state absorption,excited-state absorption and energy-transfer-upconversion processes co-exist and produce a population balance,causing the laser to operate stably at a continuous wave state.A good agreement between the theoretical results and recent experimental measurement is obtained.Furthermore,the laser structure parameters including fibre length,reflectance of output fibre Bragg grating and pumping configurations are quantitatively optimised to achieve the best performance.The results show,as expected,that the slope efficiency of the fibre laser can be improved significantly through optimisation,which then provides an important guide for the design of high-performance mid-infrared erbium-doped ZBLAN fibre lasers.     

Ld-Clad-Pumped All-Fiber Tm^3＋-Doped Silica Fiber Laser

The CW 39.4 W all-fiber LD-clad-pumped Tm^3＋-doped fiber laser output is reported with a slope efficiency of 34% in respect to the pump power. The all-fiber laser is made up by progressively splicing the pigtail fiber, matched FBG fiber and Tin-doped fiber. The reflective FBG and Tm-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 power output, whereas the total spectrum width is less than 2nm at nearly 1.94μm.     

Experimental Investigation of High Power Erbium-Ytterbium Co-doped Double Clad Fibre Laser

All-fibre high power erbium-ytterbium co-doped double clad fibre lasers are proposed and demonstrated. By using different back-cavity mirrors, the different double clad fibre lasers are constructed. It is experimentally found that the output behaviour of laser can be controlled by a back-cavity mirror. The lower the reflectivity of the back-cavity mirror, the higher the output power and the high the slop efficiency. The maximum output power is about 1.6 W and the slop efficiency is 27.6%.