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We report on the continuous-wave and passively Q-switched operation of a compositionally “mixed” heavily doped 16.6 at.% Yb:(Y,Lu)3Al5O12 garnet crystal at cryogenic temperatures (100–200 K), pumped by a volume Bragg grating stabilized diode laser emitting at 969 nm. At 140 K, in the continuous-wave regime, a maximum output power of 10.65 W was achieved at ~ 1029 nm with a slope efficiency of 56% (versus the incident pump power), a laser threshold of 1.05 W and excellent beam quality. Using Cr4+:YAG as a saturable absorber, the passively Q-switched laser generated pulses with an energy/duration of 0.15 mJ/201 ns, respectively, at a repetition rate of 39.7 kHz, corresponding to a peak power of 0.39 kW.

We present the laser characteristics of a 5 at.% Tm:YLF crystal using a modular setup at cryogenic temperatures emitting around 2 µm. Continuous-wave laser operation was achieved by pumping the laser crystal using a Volume Bragg Grating-stabilized laser diode emitting at 793 nm. A maximum output power of 6.5 W was achieved at 80 K corresponding to a slope efficiency of 66.0% with respect to the absorbed power with excellent beam quality.

We report on the optical spectroscopy and continuous-wave (CW) laser operation of ytterbium-doped yttrium gallium garnet (Yb:YGG) crystal at cryogenic temperatures. A maximum absorption cross-section of 1.7 × 10-20 cm2 with spectral bandwidth of 2.4 nm centered at 970.5 nm and a maximum emission cross-section of 6.5 × 10-20 cm2 with spectral bandwidth of 4.6 nm centered at 1024 nm were determined at 120 K. Cryogenic continuous-wave laser operation was achieved using a VBG stabilized laser diode emitting around 969 nm as pump source. At 120 K, a maximum output power of 17.50 W was achieved around 1024 nm corresponding to a slope efficiency of 87% with respect to the absorbed power.

© 2020, The Author(s). We present the spectroscopic and laser characteristics of a 3 at.% Tm:Y2O3 transparent ceramic at cryogenic temperatures. An absorption cross section of 4.7 × 10−21 cm2 with a bandwidth of 0.7 nm centered at 793.3 nm and an emission cross section of 29.0 × 10−21 cm2 centered at 1930.9 nm were estimated at 80 K. Continuous-wave laser operation was achieved using broadband and VBG stabilized laser diodes emitting around 793 nm as pump sources. With the VBG pump diode, a maximum output power of 6.4 W was achieved at 80 K corresponding to a slope efficiency of 52.0% with respect to absorbed power.

© 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement. : We report on the first erbium (Er3+) doped double tungstate waveguide laser. As a gain material, we studied a monoclinic Er3+:KLu(WO4)2 crystal. A depressed-index buried channel waveguide formed by a 60 µm-diameter circular cladding was fabricated by 3D femtosecond direct laser writing. The waveguide was characterized by confocal laser microscopy, µ-Raman and µ-luminescence mapping, confirming that the crystallinity of the core is preserved. The waveguide laser, diode pumped at 981 nm, generated 8.9 mW at 1533.6 nm with a slope efficiency of 20.9% in the continuous-wave regime. The laser polarization was linear (E || Nm). The laser threshold was at 93 mW of absorbed pump power.

© 2018 Elsevier B.V. We report on the crystal growth, structure, room- and low-temperature (6 K) absorption and emission spectroscopy of a 3 at% Yb 3+ -doped trigonal ordered langasite-type silicate crystal, Ca 3 NbGa 3 Si 2 O 14 (Yb: CNGS). The Rietveld refinement data are presented. Absorption, stimulated-emission and gain cross-sections are determined for the Yb 3+ ion in CNGS for ? and ? polarizations. The maximum stimulated emission cross-section amounts to ? SE = 0.97 × 10 ?20 cm ?2 at 1014 nm (?-polarization). The Stark splitting of the Yb 3+ multiplets is resolved. Microchip laser operation is obtained with both a-cut and c-cut 3 at% Yb: CNGS samples under end-pumping at 976 nm by a Volume Bragg Grating-stabilized diode laser. For the latter cut, the maximum output power reaches 7.61 W at 1048–1060 nm with a slope efficiency of 59%. By varying the output coupling, multi-watt emission over a 50 nm-broad spectral range is achieved.

We report on the first erbium (Er3+) doped double tungstate waveguide laser. As a gain material, we studied a monoclinic Er3+:KLu(WO4)2 crystal. A depressed-index buried channel waveguide formed by a 60 ¿m-diameter circular cladding was fabricated by 3D femtosecond direct laser writing. The waveguide was characterized by confocal laser microscopy, ¿-Raman and ¿-luminescence mapping, confirming that the crystallinity of the core is preserved. The waveguide laser, diode pumped at 981 nm, generated 8.9 mW at 1533.6 nm with a slope efficiency of 20.9% in the continuous-wave regime. The laser polarization was linear (E || Nm). The laser threshold was at 93 mW of absorbed pump power

© 2017 Optical Society of America. Multi-watt continuous-wave (CW) operation of tetragonal rare-earth calcium aluminate Yb:CaLnAlO 4 Ln Gd;Y) crystals in plano–plano microchip lasers was demonstrated with an almost quantum-defect-limited slope efficiency. Pumped at 978 nm by an InGaAs laser diode, a 3.4 mm long 8 at. % Yb:CaGdAlO 4 laser generated 7.79 W at 1057–1065 nm with a slope efficiency of ? 84% (with respect to the absorbed pump power). An even higher ? 91% was achieved with a 2.5 mm long 3 at. % Yb:CaYAlO 4 laser, from which 5.06 W were extracted at 1048–1056 nm. Both lasers produced linearly polarized output (?-polarization) with an almost circular diffraction-limited beam (M 2 x,y < 1.1). The output performance of the developed lasers was modeled, yielding an internal loss coefficient as low as 0.004?0.007 cm ?1 . In addition, their spectroscopic properties were revisited.

We study cryogenic laser operation of an Yb-doped KLu(WO4)2 crystal pumped with a volume Bragg grating (VBG) stabilized diode laser at 981 nm. In the continuous wave laser regime, a maximum output power of 4.31 W is achieved at 80 K with a slope efficiency of 44.0% with respect to the incident pump power. Using a 85% initial transmission Cr:YAG crystal for passive Q-switching, an average output power of 2.11 W is achieved at 100 K for a repetition rate of 19 kHz. The pulse energy, pulse duration and peak power amount to 111 ¿J, 231 ns and 0.48 kW, respectively.

© 2017 Optical Society of America. Multi-watt continuous-wave (CW) operation of tetragonal rare-earth calcium aluminate Yb:CaLnAlO 4 Ln Gd;Y) crystals in plano–plano microchip lasers was demonstrated with an almost quantum-defect-limited slope efficiency. Pumped at 978 nm by an InGaAs laser diode, a 3.4 mm long 8 at. % Yb:CaGdAlO 4 laser generated 7.79 W at 1057–1065 nm with a slope efficiency of ? 84% (with respect to the absorbed pump power). An even higher ? 91% was achieved with a 2.5 mm long 3 at. % Yb:CaYAlO 4 laser, from which 5.06 W were extracted at 1048–1056 nm. Both lasers produced linearly polarized output (?-polarization) with an almost circular diffraction-limited beam (M 2 x,y < 1.1). The output performance of the developed lasers was modeled, yielding an internal loss coefficient as low as 0.004?0.007 cm ?1 . In addition, their spectroscopic properties were revisited.

A diode-pumped Tm,Ho:KLu(WO4)2 microchip laser passively Q-switched with a Cr:ZnS saturable absorber generated an average output power of 131 mW at 2063.6 nm with a slope efficiency of 11% and a Q-switching conversion efficiency of 58%. The pulse characteristics were 14 ns / 9 ¿J at a pulse repetition frequency of 14.5 kHz. With higher modulation depth of the saturable absorber, 9 ns / 10.4 ¿J / 8.2 kHz pulses were generated at 2061.1 nm corresponding to a record peak power extracted from a passively Q-switched Tm,Ho laser of 1.15 kW. A theoretical model is presented predicting the pulse energy and duration. The simulations are in good agreement with the experimental results

A diode-pumped Tm,Ho:KLu (WO4)(2) microchip laser passively Q-switched with a Cr:ZnS saturable absorber generated an average output power of 131 mW at 2063.6 nm with a slope efficiency of 11% and a Q-switching conversion efficiency of 58%. The pulse characteristics were 14 ns/9 mu J at a pulse repetition frequency of 14.5 kHz. With higher modulation depth of the saturable absorber, 9 ns/10.4 mu J/8.2 kHz pulses were generated at 2061.1 nm, corresponding to a record peak power extracted from a passively Q-switched Tm,Ho laser of 1.15 kW. A theoretical model is presented, predicting the pulse energy and duration. The simulations are in good agreement with the experimental results. (C) 2016 Optical Society of America

We describe a compact Yb: YAG laser Q-switched by a graphene-based saturable absorber and pumped by a laser diode at 932 or 969 nm. The compact laser generates a maximum average output power value of 185 mW at 1032 nm with a slope efficiency value of 12%. The shortest duration of the Q-switched pulse achieved is 228 ns at a repetition frequency of 285 kHz. The maximum pulse energy amounts to 0.65 µJ.

We present the crystal growth, optical spectroscopy, and room temperature continuous-wave (CW) laser operation of monoclinic Ho:KLu(WO4) 2 crystals. Macro defect-free crystals of several dopant concentrations were grown by top-seeded solution growth slow-cooling method. The evolution of unit cell parameters with holmium doping level and temperature was studied using X-ray powder diffraction. The spectroscopic properties were characterized in terms of room- and low-temperature optical absorption and photoluminescence. From low-temperature optical absorption measurements, the energy of the Stark levels was determined. Calculation of the emission and gain cross sections is presented. CW laser action was realized for 3 and 5 at. % Ho-doped KLu(WO4)2 by in-band pumping using a Tm:KLu(WO4)2 pump laser. A maximum output power of 507 mW with a slope efficiency of ∼38 % with respect to the incident power was achieved at 2,080 nm with the Ho:KLu(WO4)2 laser.

We demonstrate continuous wave (CW) room temperature laser operation of the monoclinic Ho3+-doped KLu(WO4)2 crystal using a diode-pumped Tm3+:KLu(WO4)2 laser for in-band pumping. The slope efficiency achieved amounts to ∼55% with respect to the absorbed power and the maximum output power of 648 mW is generated at 2078 nm. © 2010 Optical Society of America.