Continuous-wave Ho Research Articles

High efficiency continuous-wave Ho: LSO laser wing-pumped by the laser diode at 1.91 μm

We present a high-efficiency continuous-wave Ho: LSO laser wing-pumped by a 1.91 μm laser diode. The impact of different output transmittances on the laser output power is compared and analyzed. The optimal result was achieved with a −500-mm radius curvature and a 6% transmission output coupler. The maximum output power of the Ho: LSO laser is 7.81 W, with a slope efficiency of 44.7%, a center wavelength of 2,106.6 nm, and beam quality factors of 1.4 in the x-direction and 1.3 in the y-direction.

Dual-wavelength collaboratively pumping scheme for a 3.9 µm continuous-wave Ho:YLF laser

A dual-wavelength collaboratively pumping scheme is proposed to realize the efficient operation of a 3.9 µm continuous wave Ho:YLF laser. An 888 nm laser is used to excite ions from the 5I8 ground-state manifold to the 5I5 laser’s upper manifold. Another 2.1 µm laser is used to excite ions from the 5I6 laser’s lower manifold to the short-lived 5I4 manifold to eliminate the self-terminated effect of 3.9 µm laser oscillation. Numerical simulation of 3.9 µm laser output performances is carried out, based on the developed rate equations. Simulation results indicate that the dual-wavelength collaboratively pumping scheme is feasible to realize the highly efficient output of the 3.9 µm continuous wave Ho:YLF laser. The relationship between the pump power for 888 nm and 2.1 µm laser sources is analyzed to obtain the optimal output. Furthermore, the impacts of crystal doping concentration, crystal length, output mirror transmittance, and important energy-transfer processes on the laser output performances are also analyzed. The dual-wavelength collaboratively pumping scheme provides beneficial guidance for the generation of a 3.9 µm high-power continuous-wave laser in an Ho:YLF laser.

Efficient Continuous-Wave Ho : LSO Laser Dual-End-Pumped by a Laser Diode at 1.94 μm

Efficient Continuous-Wave Ho : LSO Laser Dual-End-Pumped by a Laser Diode at 1.94 μm

Iterative 3D modeling of thermal effects in end-pumped continuous-wave Ho3+:YAG lasers

Iterative 3D modeling of thermal effects in end-pumped continuous-wave Ho³⁺:YAG lasers

Efficient continuous-wave Ho:GTO laser intracavity-pumped by an in-band pumped Tm:YAG laser

In this paper we demonstrate an efficient intra-cavity Tm:YAG-Ho:GdTaO4 (Ho:GTO) laser for the first time. Under 1617-nm pumping, the output power of 8.38 W at 2019.1 nm was obtained with an incident pump power of 15.5 W and a slope efficiency of 59.9% in Tm:YAG laser. At same incident 1617-nm power, the intra-cavity Ho:GTO laser produced 3.74 W continuous-wave (CW) output power at 2081.5 nm and 30.6% slope efficiency. In addition, the M2 factors of the intra-cavity Ho:GTO laser at maximum output was evaluated to be 1.21 and 1.14 in the x- and y-directions, respectively.

Compact intracavity-pumped Ho:YVO4 laser developed using a diode-pumped Tm:YAP laser

We developed a compact 2-μm intracavity-pumped Ho : YVO4 laser using a diode-pumped Tm:YAP laser at room temperature. Before applying the Ho laser, the lasing characteristics of the a-cut Tm:YAP laser were studied, and a maximum output power of 2.76 W at 1951.6 nm was obtained under an incident laser diode pump power of 25 W with a slope efficiency of 15.8%. Under the same cavity structure, the continuous-wave Ho : YVO4 laser yielded a maximum output power of 1.7 W at 2052.7 nm for an incident diode pump power of 29 W, corresponding to a slope efficiency of 10.4%. The beam quality factor (M2) of the Ho : YVO4 laser at the maximum output power was estimated to be 1.16 and 1.26 in the horizontal and vertical directions, respectively, which indicates the occurrence of near-diffraction-limited beam propagation.

Efficient Ho:(Sc0.5Y0.5)2SiO5 laser at 2.1 µm in-band pumped by Tm fiber laser.

In this paper, we demonstrate a new 2.1-µm Ho:(Sc0.5Y0.5)2SiO5 (Ho:SYSO) laser at room temperature. The absorption and emission spectra of Ho:SYSO crystal were studied at temperature of 300 K. The strongest absorption peak of 5I7 level of Ho ions in SYSO crystal is located at 1943 nm with cross section of 0.79 × 10-20 cm2. The maximum emission cross section of 1.74 × 10-20 cm2 is located at 2032 nm. A 1940.3-nm narrow-linewidth Tm fiber was used to pump the Ho:SYSO crystal. At absorbed pump power of 20.4 W, the continuous wave Ho:SYSO laser yielded 10.3 W maximum output power at 2097.67 nm and 54.7% slope efficiency respect with absorbed pump power. In addition, we have estimated the beam quality factor (M2) of Ho:SYSO laser to be 1.7 near maximum output level.

Continuous-wave-tunable and passively Q-switched 2.9 µm Ho,Pr:LiLuF4 lasers

A wavelength tuning experiment of a continuous-wave Ho,Pr:LiLuF4 bulk laser operating at 2900 nm has been demonstrated for the first time. Two wavelength-tunable bands in the ranges of 2830–2902 nm and 2945–2956 nm were obtained. In addition, by using a semiconductor saturable absorber mirror, a high-peak-power passively Q-switched operation was realized. The shortest pulse width was 395 ns with a repetition rate of 7.29 kHz, corresponding to a peak power of 51.1 W. The results indicate the potential of Ho,Pr:LLF crystals for continuous-wave-tunable and passively Q-switched lasers operating at ~3.0 µm.

High power Ho:SSO laser resonantly pumped by a FBG-locked Tm fiber laser at 1940.3 nm

We demonstrate a high power continuous wave Ho:SSO laser resonantly pumped by a FBG-locked Tm fiber laser at 1940.3nm in this paper. The maximum output power of 8.72W was obtained under the incident pump power of 19.8W, corresponding to a slope efficiency of 54.3% and an optical conversion efficiency of 44.0%. The output wavelength of Ho:SSO laser was centered at 2113.5 nm. The Ho:SSO laser operated at TEM00 mode with a beam quality factor of Mx2 of 1.6 and My2 of 1.4 at maximum output level.

High-repetition-rate single-frequency Ho:YAG MOPA system.

A stable, 2.09μm single-frequency Ho:YAG master oscillator and power amplifier (MOPA) system at a pulse repetition frequency of 1.25kHz is demonstrated. The maximum output energy of the single-frequency injection-seeded laser is 13.76mJ, and the corresponding pulse width is 178.9ns. The seed laser is a continuous-wave Ho:YAG non-planar ring oscillator laser. The half-width of the pulse spectrum is measured to be 2.65MHz by using the heterodyne technique, which is about 1.06 times Fourier transform limited.

Highly-Efficient Ho:SiSc2O5 Laser Pumped by a Narrow Line-Width Tm:YAP Laser at 1.94 μm

We present a highly-efficient continuous-wave Ho:SSO laser pumped by a diode-pumped Tm:YAP laser with a narrow linewidth (NL) of 0.3 nm. With the free-running (FR) Tm:YAP laser, we obtain a maximum output power of 2.23 W at an absorption pump power of 7.2 W, corresponding to an optical conversion efficiency of 31% and a slope efficiency of 42.6%. With the NL Tm:YAP laser, we obtain a maximum output power of 2.88 W at the same absorption pump power. The optical conversion efficiency increases to 40% when the slope efficiency increases to 55.5%. The output linewidth of the Ho:SSO laser is 0.8 nm when we use the Tm:YAP laser with a narrow linewidth of 1.8 nm pumped by a FR Tm:YAP laser. The beam quality also changes from 1.31 to 1.22.

Compact resonantly intra-cavity pumped tunable Ho:Sc2SiO5 laser

A compact intra-cavity pumped low threshold continuous-wave Ho:Sc2SiO5 laser is reported. The characteristics of output wavelength tuning are investigated by use a intra-cavity briefringent (BF) filter. A wavelength tunable range of 140nm from 2020 to 2160nm is achieved. For the free-running mode, the laser slope efficiency is 24.8%, when the output central wavelength is 2110nm. The laser threshold is about 820mW of incident pump power. With the BF filter, a maximum output power of 870mW is obtained at the incident pump power of 5W, corresponding to a slope efficiency of 20.3%. The characteristics of output wavelength verse the crystal temperature are also investigated.

An Efficient Continuous Wave Ho:LSO Laser Double-Pass Pumped by a Linewidth-Narrowed Tm Fiber Laser

We report for the first time an efficient continuous wave Ho:LSO laser double-pass pumped by a Tm fiber laser. We achieve a maximum output power equal to 3.6 W at an absorbed pump power of 10.5 W, which corresponds to an optical-to-optical conversion efficiency of 34.3% and a slope efficiency of 59.3%. The output laser wavelength is centered at 2,105.1 nm with a linewidth of ≈2.2 nm, and the beam quality factors $$ {\mathrm{M}}_x^2 $$ = 1.2 and $$ {\mathrm{M}}_y^2 $$ = 1.1 measured by the 90/10 knife-edge method.

A single-longitudinal-mode continuous-wave laser at 2.05 μm pumped by a Tm-fibre laser**Project supported by the National Natural Science Foundation of China (Grant Nos. 61308009 and 61405047), the China Postdoctoral Science Foundation (Grant Nos. 2016T90287 and 2015M570290), the Fundamental Research Funds for the Central Universities of China (Grant No. HIT.NSRIF.2015042), and the Postdoctoral Science Foundation of Heilongjiang Province, China (Grant No.

We present a single-longitudinal-mode continuous-wave Ho :YVO4 laser at 2.05 pumped by a Tm-doped fibre laser. Use of a cavity etalon enables spectral selectivity for single-mode operation. The highest power achieved in the single longitudinal mode at 2052.5 nm is 282 mW at a slope efficiency of 6.9%, corresponding to an optical conversion efficiency of 3.0%. These features demonstrate that this single-longitudinal-mode Ho:YVO4 laser is suitable for use as a seed laser in some Lidar systems (e.g., coherent Lidar or differential absorption Lidar). To the best of our knowledge, this is the first report on such a single-longitudinal-mode Ho:YVO4 laser at 2.05 m.

Single-longitudinal-mode Ho:LuAG laser at 2.1 μm

In this letter we report a continuous wave Ho:LuAG laser running on single-longitudinal-mode operation. Two Fabry–Perot etalons were used to narrow the laser line-width. By regulating the angle of the etalons, single-longitudinal-mode lasing was achieved at a wavelength of 2100.65 nm. The maximum power and the slope efficiency of single-longitudinal-mode Ho:LuAG output are 264 mW and 14.5%, respectively. To our knowledge, this is the first time a Ho:LuAG laser with single-longitudinal-mode operation has been obtained.

A narrow linewidth continuous wave Ho:SSO laser with Fabry–Perot etalons

We report a narrow linewidth continuous wave Ho:SSO laser with Fabry–Perot etalons. The maximum output power reaches 2.35 W when the incident pump power is 15.5 W with the optical-to-optical conversion efficiency and slope efficiency 15.1 and 19.3 %, respectively. A stable output and a narrow linewidth less than 0.3 nm FWHM at 2112 nm are achieved. With the intra-cavity F–P etalons, the laser beam quality M2 = 1.26 ± 0.02, which is optimized obviously.

A Narrow Linewidth Continuous Wave Ho:YAG Laser Pumped by a Tm:YLF Laser**Supported by the Department of Science and Technology of Changchun City under Grant No 2013143.

A narrow linewidth cw Ho:YAG laser pumped by a 1908nm Tm:YLF laser based on the volume Bragg grating is established. The maximum output power of 9.6 W for the incident pump power of 16.9 W is obtained, and the corresponding slope efficiency and optical-to-optical conversion efficiency are 67.2% and 56.8%, respectively. The Ho:YAG laser operates stably at 2122.1 nm by using two Fabry-Perot etalons, with a full width at half maximum less than 0.2 nm.

Dual-end-pumped high-power Cr2+:ZnS passively Q-switched Ho:YAG ceramic laser

We demonstrated a high-power dual-end-pumped passively Q-switched Ho:YAG ceramic laser with a Cr2+:ZnS saturable absorber (SA). The influence of the beam diameter on SA on the Q-switched laser performance was investigated. Up to 30.3 W average output power was obtained, to our best knowledge, which is the highest average output power obtained in a Ho-doped passively Q-switched laser. The maximum pulse energy and peak power of 0.94 mJ and 33.5 kW were achieved, when the Cr2+:ZnS SA was placed far from the laser beam waist, corresponding to a pulse width of 28 ns and a pulse repetition frequency of 28.8 kHz. In addition, we achieved the highest output power of 40.4 W from continuous-wave Ho:YAG ceramic laser.

In-band-pumped Ho:KLu(WO4)2 microchip laser with 84% slope efficiency.

We report on a continuous-wave Ho:KLu(WO4)2 (KLuW) microchip laser with a record slope efficiency of 84%, the highest value among the holmium inband-pumped lasers, delivering 201 mW output power at 2105 nm. The Ho laser operating at room temperature on the (5)I8→(5)I7 transition is in-band-pumped by a diode-pumped Tm:KLuW microchip laser at 1946 nm. Ho:KLuW laser operation at 2061 and 2079 nm is also demonstrated with a maximum slope efficiency of 79%. The microchip laser generates an almost diffraction-limited output beam with a Gaussian profile and a M2<1.1. The laser performance of the Ng-cut Ho:KLuW crystal is very similar for pump light polarizations ‖Nm and Np. The positive thermal lens plays a key role in the laser mode stabilization and proper mode-matching. The latter, together with the low quantum defect under in-band-pumping (∼0.08), is responsible for the extraordinary high slope efficiency.

Highly efficient high power CW and Q-switched Ho:YLF laser

AbstractAn efficient operation of a Ho:YLF laser pumped by a Tm-doped fibre laser is reported. The research in a continuous-wave (CW) operation was done for two crystals of the same 0.5 at.%Ho dopant concentration and with different lengths (3×3×30 mm