RESUMEN
A Tm:LiYF4 laser operating on the 3H4 â 3H5 transition is embedded in a high-power diode-pumped Nd:ASL laser for intracavity upconversion pumping at 1.05â µm. This leads to a record-high output power at 2.3â µm for any bulk thulium laser pumped by an upconversion process. The continuous-wave Tm:LiYF4 laser delivers 1.81â W at 2.3â µm for 32â W of laser-diode pump power, making this kind of pumping competitive with direct diode pumping. The intracavity pumping process allows for counteracting the low absorption inherent to upconversion pumping and to dispatch the thermal loads on two separate laser crystals. The proposed laser architecture also features a relatively weak heating of the Tm:LiYF4 crystal and an increased tolerance to Tm3+ absorption. This laser design opens a new paradigm that holds great promise for high-power 2.3-µm solid-state lasers based on thulium ions.
RESUMEN
We report on the investigation of continuous-wave (CW) and SEmiconductor Saturable Absorber Mirror (SESAM) mode-locked operation of a Yb:GdScO3 laser. Using a single-transverse-mode, fiber-coupled InGaAs laser diode at 976â nm as a pump source, the Yb:GdScO3 laser delivers 343â mW output power at 1062â nm in the CW regime, which corresponds to a slope efficiency of 52%. Continuous tuning is possible across a wavelength range of 84â nm (1027-1111â nm). Using a commercial SESAM to initiate mode-locking and stabilize soliton-type pulse shaping, the Yb:GdScO3 laser produces pulses as short as 42 fs at 1065.9â nm, with an average output power of 40â mW at 66.89â MHz. To the best of our knowledge, this is the first demonstration of passively mode-locking with Yb:GdScO3 crystal.
RESUMEN
We present the growth, spectroscopy, continuous-wave (CW) and passively mode-locked (ML) operation of a novel "mixed" tetragonal calcium rare-earth aluminate crystal, Yb3+:Ca(Gd,Y)AlO4. The absorption, stimulated-emission, and gain cross-sections are derived for π and σ polarizations. The laser performance of a c-cut Yb:Ca(Gd,Y)AlO4 crystal is studied using a spatially single-mode, 976-nm fiber-coupled laser diode as a pump source. A maximum output power of 347â mW is obtained in the CW regime with a slope efficiency of 48.9%. The emission wavelength is continuously tunable across 90â nm (1010 - 1100â nm) using a quartz-based Lyot filter. With a commercial SEmiconductor Saturable Absorber Mirror to initiate and maintain ML operation, soliton pulses as short as 35 fs are generated at 1059.8â nm with an average output power of 51â mW at â¼65.95â MHz. The average output power can be scaled to 105â mW for slightly longer pulses of 42 fs at 1063.5â nm.
RESUMEN
We report on the continuous-wave (CW) and, for what we believe to be the first time, passively mode-locked (ML) laser operation of an Yb3+-doped YSr3(PO4)3 crystal. Utilizing a 976-nm spatially single-mode, fiber-coupled laser diode as pump source, the Yb:YSr3(PO4)3 laser delivers a maximum CW output power of 333â mW at 1045.8â nm with an optical efficiency of 55.7% and a slope efficiency of 60.9%. Employing a quartz-based Lyot filter, an impressive wavelength tuning range of 97â nm at the zero level was achieved in the CW regime, spanning from 1007â nm to 1104â nm. In the ML regime, incorporating a commercially available semiconductor saturable absorber mirror (SESAM) to initiate and maintain soliton-like pulse shaping, the Yb:YSr3(PO4)3 laser generated pulses as short as 61 fs at 1062.7â nm, with an average output power of 38â mW at a repetition rate of â¼66.7â MHz.
RESUMEN
Depressed-cladding surface channel waveguides were inscribed in a 0.5 at.% Pr:LiYF4 crystal by femtosecond Direct Laser Writing. The waveguides consisted of a half-ring cladding (inner diameter: 17â µm) and side structures ("ears") improving the mode confinement. The waveguide propagation loss was as low as 0.14 ± 0.05â dB/cm. The orange waveguide laser operating in the fundamental mode delivered 274â mW at 604.3â nm with 28.4% slope efficiency, a laser threshold of only 29â mW and linear polarization (π), representing record-high performance for orange Pr waveguide lasers.
RESUMEN
A compact Tm:GdVO4 laser pumped by a 794â nm laser diode generated 6.09â W at 2.29â µm (3H4 â 3H5 Tm3+ transition) with a high slope efficiency of 30.8% and linear laser polarization (π). The polarized spectroscopic properties of Tm3+ in GdVO4 were also revised. The peak stimulated-emission cross section of Tm3+ is 2.97 × 10-20 cm2 at 2280â nm, corresponding to an emission bandwidth of 42â nm for π-polarized light.
RESUMEN
We study a cascade laser scheme involving the 3H4 â 3H5 and 3F4 â 3H6 consecutive transitions in Tm3+-doped materials as a promising technique to favor laser emission at 2.3 µm. We examine the conditions in terms of the Tm3+ doping levels for which the cascade laser is beneficial or not. For this, Tm:LiYF4 lasers based on crystals with several doping levels in the range of 2.5 - 6 at.% with and without cascade laser are studied. For low doping of 2.5 at.% Tm3+, adding the laser emission at 1.9 µm allows to double the output power at 2.3 µm, whereas for high doping of 6 at.%, allowing the laser to operate at 1.9 µm totally suppresses the laser emission at 2.3 µm. An analytical model is developed and confronted with experimental results to predict this doping-dependent phenomenon and forecast the potential benefits. This study of cascade laser emission on the 3H4â 3H5 and 3F4â 3H6 transitions versus the Tm3+ doping level is finally extended to other well-known Tm3+-doped laser materials.
RESUMEN
We report on the first laser operation of a Sm3+-doped monoclinic KGd(WO4)2 double tungstate crystal in the red spectral range. Pumped by a frequency-doubled optically pumped semiconductor laser (2ω-OPSL) at 479.1â nm, the 0.8 at. % Sm:KGd(WO4)2 laser generated an output power up to 17.6â mW at 649.1â nm (the 4G5/2 â 6H9/2 transition) with a slope efficiency of 16.9%, a laser threshold down to 29â mW and a linear polarization. The laser exhibited a self-pulsing behavior, delivering µs-long pulses with a repetition rate of a few kHz. The polarized spectroscopic properties of Sm3+ ions were determined as well.
RESUMEN
We report on thermal, spectroscopic, and laser properties of transparent 5 at.% Tm3+-doped yttria and "mixed" yttria-scandia ceramics fabricated by vacuum sintering at 1750°C using nanoparticles produced by laser ablation. The solid-solution (Tm0.05Y0.698Sc0.252)2O3 ceramic features a broadband emission extending up to 2.3 µm (gain bandwidth, 167â nm) and high thermal conductivity of 4.48 W m-1 K-1. A Tm:Y2O3 ceramic laser generated 812â mW at 2.05 µm with a slope efficiency η of 70.2%. For the Tm:(Y,Sc)2O3 ceramic, the output power was 523â mW at 2.09 µm with η = 44.7%. These results represent record-high slope efficiencies for any parent or "mixed" Tm3+-doped sesquioxide ceramics.
RESUMEN
We report on the first deep-red laser operation of a heavily Eu3+-doped cesium gadolinium double molybdate crystal with a perfect cleavage. A 17 at. % Eu:CsGd(MoO4)2 laser based on cleaved single-crystal plates generated a maximum continuous-wave output power of 212â mW at 703.1â nm (5D0 â 7F4 transition) with a slope efficiency of 30.1%, a low laser threshold of 51â mW, linear polarization, and a beam quality factor M2 = 1.6-1.7. This monoclinic crystal is promising for deep-red microchip lasers.
RESUMEN
We report on the first laser operation of a disordered Tm:CaGdAlO4 crystal on the 3H4 â 3H5 transition. Under direct pumping at 0.79 µm, it generates 264â mW at 2.32â µm with a slope efficiency of 13.9% and 22.5% vs. incident and absorbed pump power, respectively, and a linear polarization (σ). Two strategies to overcome the bottleneck effect of the metastable 3F4 Tm3+ state leading to the ground-state bleaching are exploited: cascade lasing on the 3H4 â 3H5 and 3F4 â 3H6 transitions and dual-wavelength pumping at 0.79 and 1.05 µm combining the direct and upconversion pumping schemes. The cascade Tm-laser generates a maximum output power of 585â mW at 1.77â µm (3F4 â 3H6) and 2.32â µm (3H4 â 3H5) with a higher slope efficiency of 28.3% and a lower laser threshold of 1.43 W, out of which 332â mW are achieved at 2.32â µm. Under dual-wavelength pumping, further power scaling to 357â mW at at 2.32â µm is observed at the expense of increased laser threshold. To support the upconversion pumping experiment, excited-state absorption spectra of Tm3+ ions for the 3F4 â 3F2,3 and 3F4 â 3H4 transitions are measured for polarized light. Tm3+ ions in CaGdAlO4 exhibit broadband emission at 2.3 - 2.5 µm making this crystal promising for ultrashort pulse generation.
RESUMEN
We report on the cascade continuous-wave operation of a diode-pumped Tm:YVO4 laser on the 3F4 â 3H6 (at â¼2â µm) and 3H4 â 3H5 (at â¼2.3â µm) Tm3+ transitions. Pumped with a fiber-coupled spatially multimode 794â nm AlGaAs laser diode, the 1.5 at.% Tm:YVO4 laser yielded a maximum total output power of 6.09 W with a slope efficiency of 35.7% out of which the 3H4 â 3H5 laser emission corresponded to 1.15 W at 2291-2295 and 2362-2371â nm with a slope efficiency of 7.9% and a laser threshold of 6.25 W.
RESUMEN
We report on a bulk thulium laser operating on the 3H4 â 3H5 transition with pure upconversion pumping at 1064â nm by an ytterbium fiber laser (addressing the 3F4 â 3F2,3 excited-state absorption (ESA) transition of Tm3+ ions) generating 433â mW at 2291â nm with a slope efficiency of 7.4% / 33.2% vs. the incident / absorbed pump power, respectively, and linear laser polarization representing the highest output power ever extracted from any bulk 2.3â µm thulium laser with upconversion pumping. As a gain material, a Tm3+-doped potassium lutetium double tungstate crystal is employed. The polarized ESA spectra of this material in the near-infrared are measured by the pump-probe method. The possible benefits of dual-wavelength pumping at 0.79 and 1.06â µm are also explored, indicating a positive effect of co-pumping at 0.79â µm on reducing the threshold pump power for upconversion pumping.
RESUMEN
We report on sub-40 fs pulse generation from a Yb:Sc2SiO5 laser pumped by a spatially single-mode fiber-coupled laser diode at 976â nm. A maximum output power of 545â mW was obtained at 1062.6â nm in the continuous-wave regime, corresponding to a slope efficiency of 64% and a laser threshold of 143â mW. A continuous wavelength tuning across 80â nm (1030 -1110â nm) was also achieved. Implementing a SESAM for starting and stabilizing the mode-locked operation, the Yb:Sc2SiO5 laser delivered soliton pulses as short as 38 fs at 1069.5â nm with an average output power of 76â mW at a pulse repetition rate of â¼79.8â MHz. The maximum output power was scaled to 216â mW for slightly longer pulses of 42 fs, which corresponded to a peak power of 56.6â kW and an optical efficiency of 22.7%. To the best of our knowledge, these results represent the shortest pulses ever achieved with any Yb3+-doped rare-earth oxyorthosilicate crystal.
RESUMEN
We report on the first sub-60 fs pulse generated from a diode-pumped SESAM mode-locked Yb-laser based on a non-centrosymmetric Yb:YAl3(BO3)4 crystal as a gain medium. In the continuous-wave regime, pumping with a spatially single-mode, fiber-coupled 976â nm InGaAs laser diode, the Yb:YAl3(BO3)4 laser generated 391â mW at 1041.7â nm with a slope efficiency as high as 65.1%, and a wavelength tuning across 59â nm (1019 to 1078â nm) was achieved. By implementing a commercial SESAM to initiate and sustain the soliton type mode-locking, and using only a 1â mm-thick laser crystal, the Yb:YAl3(BO3)4 laser delivered pulses as short as 56 fs at a central wavelength of 1044.6â nm with an average output power of 76â mW at a pulse repetition rate of â¼67.55â MHz. To the best of our knowledge, this result represents the shortest pulses ever achieved from Yb:YAB crystal.
RESUMEN
We report on sub-50 fs pulse generation from a passively mode-locked Yb:SrF2 laser pumped with a spatially single-mode, fiber-coupled laser diode at 976â nm. In the continuous-wave regime, the Yb:SrF2 laser generated a maximum output power of 704â mW at 1048â nm with a threshold of 64â mW and a slope efficiency of 77.2%. A continuous wavelength tuning across 89â nm (1006 - 1095â nm) was achieved with a Lyot filter. By implementing a SEmiconductor Saturable Absorber Mirror (SESAM) for initiating and sustaining the mode-locked operation, soliton pulses as short as 49 fs were generated at 1057â nm with an average output power of 117â mW at a pulse repetition rate of â¼75.9â MHz. The maximum average output power of the mode-locked Yb:SrF2 laser was scaled up to 313â mW for slightly longer pulses of 70 fs at 1049.4â nm, corresponding to a peak power of 51.9â kW and an optical efficiency of 34.7%.
RESUMEN
We report on the first, to the best of our knowledge, laser operation on the 4I11/2 â 4I13/2 transition of erbium-doped disordered calcium lithium niobium gallium garnet (CLNGG) crystals with broadband mid-infrared emission properties. A 41.4â at.% Er:CLNGG continuous-wave laser generated 292â mW at 2.80â µm with 23.3% slope efficiency and a laser threshold of 209â mW. Er3+ ions in CLNGG feature inhomogeneously broadened spectral bands (σSE = 1.79 × 10-21â cm2 at 2.79â µm; emission bandwidth, 27.5â nm), a large luminescence branching ratio for the 4I11/2 â 4I13/2 transition of 17.9%, and a favorable ratio of the 4I11/2 and 4I13/2 lifetimes, exhibiting values of 0.34â ms and 1.17â ms (for 41.4â at.% Er3+), respectively.
RESUMEN
We report on the first, to the best of our knowledge, continuous-wave laser operation of a Tm3+,Ho3+-codoped calcium fluoride crystal at â¼2.1 µm. Tm,Ho:CaF2 crystals were grown by the Bridgman method, and their spectroscopic properties were studied. The stimulated-emission cross section for the 5I7 â 5I8 Ho3+ transition is 0.72 × 10-20 cm2 at 2025 nm, and the thermal equilibrium decay time is 11.0â ms. A 3 at. % Tm, 0.3 at. % Ho:CaF2 laser generated 737â mW at 2062-2088 nm with a slope efficiency of 28.0% and a laser threshold of 133â mW. Continuous wavelength tuning between 1985 and 2114â nm (tuning range: 129â nm) was demonstrated. The Tm,Ho:CaF2 crystals are promising for ultrashort pulse generation at â¼2 µm.
RESUMEN
We report on a Kerr-lens mode-locked laser based on an Yb3+-doped disordered calcium lithium niobium gallium garnet (Yb:CLNGG) crystal. Pumping by a spatially single-mode Yb fiber laser at 976â nm, the Yb:CLNGG laser delivers soliton pulses as short as 31 fs at 1056.8â nm with an average output power of 66â mW and a pulse repetition rate of â¼77.6â MHz via soft-aperture Kerr-lens mode-locking. The maximum output power of the Kerr-lens mode-locked laser amounted to 203â mW for slightly longer pulses of 37 fs at an absorbed pump power of 0.74 W, which corresponds to a peak power of 62.2â kW and an optical efficiency of 20.3%.
RESUMEN
We report on a double-clad fiber laser operating on the 3P0 â 3F4 Pr3+ transition (in the deep-red spectral range) pumped by a GaN diode laser at â¼442â nm. It employs a 0.8-mol% PrF3-doped ZBLAN double-clad fiber with a 7.5-µm core, a double D-shaped inner cladding, and a length of 3.0 m. The laser delivers a maximum output power of 0.71 W at 716.7â nm with a slope efficiency of 9.0% (versus the launched pump power) and a laser threshold of 0.90 W. The laser emission is partially polarized. The laser performance is simulated providing a guideline for watt-level deep-red fiber laser sources.