Y2O3 Ceramic Laser Research Articles

Wavelength-tunable Tm:Y2O3 ceramic vortex laser with a changeable orbital angular momentum state.

Wavelength-tunable orbital angular momentum (OAM) lasers with controllable topological charges have the potential for serving as light sources for large-capacity optical communication by combining conventional wavelength division multiplexing (WDM) with OAM mode-division multiplexing (OAM-MDM). In this study, we demonstrate a wavelength-tunable Tm-bulk laser that can control OAM states in the 2-µm spectral range. The excitation conditions for different Laguerre-Gaussian (L G 0,l ) modes in a bulk laser cavity are theoretically determined by measuring the spatial propagation dynamics of the annular pump beam. As a proof-of-principle study, we experimentally generate OAM states of |ℏ| and |2ℏ| from a T m:Y 2 O 3 ceramic laser with a tunable emission wavelength using a Lyot filter (LF). The spatial properties of the scalar optical vortices are well conserved during wavelength tuning, indicating the feasibility of our approach for producing wavelength-tunable structured light. These OAM laser sources, which are characterized by their robustness and compactness, have potential applications in various areas such as optical communications, quantum optics, super-resolution microscopes, and more.

Reduction of depolarization loss in a Tm-doped sesquioxide ceramic laser using a ring-shaped pump beam.

We report on a simple method for reduction of the depolarization loss in an end-pumped Tm:Y2O3 ceramic laser by using a near-field ring-shaped pump beam. Initially, we theoretically derive the expression of the depolarization loss in a bulk laser end-pumped with a near-field flat-top-hat or ring-shaped beam, where a significant reduction of depolarization loss in the latter case is presented. Experimental verification is thereafter carried out with a Tm:Y2O3 ceramic laser employing these two different pump configurations. It shows that the experimentally measured depolarization losses are close to the simulated values; the loss in the case of the annular-beam pump is almost 18 times lower than that with a quasi-top-hat beam at a same absorption pump power of 7.4 W. This work, as a proof-of-principle study, indicates that depolarization loss in the end-pumped bulk lasers can be significantly reduced simply by using a ring-shaped pump beam.

Highly efficient lasing and thermal properties of Tm:Y2O3 and Tm:(Y,Sc)2O3 ceramics.

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, 167 nm) and high thermal conductivity of 4.48 W m-1 K-1. A Tm:Y2O3 ceramic laser generated 812 mW at 2.05 µm with a slope efficiency η of 70.2%. For the Tm:(Y,Sc)2O3 ceramic, the output power was 523 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.

High power Ho:Y2O3 ceramic laser with controllable output intensity profile at 2.1 µm.

We report on a high-power Ho:Y2O3 ceramic laser at 2.1 µm with controllable output beam profile ranging from LG01 donut, flat-top to TEM00 mode using a simple two-mirror resonator. In-band pumped at 1943nm using a Tm fiber laser beam shaped via a coupling optics comprising a capillary fiber and lens-combination to achieve distributed pump absorption in Ho:Y2O3 and hence selective excitation of the target mode, the laser yields 29.7 W of LG01 donut, 28.0 W of crater-like, 27.7 W of flat-top and 33.5 W of TEM00 mode output for absorbed pump power of 53.5 W, 56.2 W, 57.3 W and 58.2 W, respectively, corresponding to a slope efficiency of 58.5%, 54.3%, 53.8% and 61.2%. This is, to the best of our knowledge, the first demonstration of laser generation with continuously tunable output intensity profile at ∼2 µm wavelength region.

High-power Er:Y2O3 ceramic laser with an optical vortex beam output at ∼ 2.7 μm

We report on the direct generation of the high-power optical vortices at ∼2.7 μm from an Er:Y2O3 ceramic laser end-pumped by an annular pump beam using a simple capillary fiber-based pump beam conditioning scheme. Taking advantage of the thermal gradient on the gain medium and mode matching between the pump and oscillating modes, vortex beams with a controllable topological charge order of l = 1 and l = 2 were successfully achieved. The laser yields 4.65 W of output power at an absorbed power of 19.8 W, corresponding to a slope efficiency of 25.9% with respect to the absorbed pump power. Adaptable beam profiles from a shallow crater-shape to quasi-top-hat intensity patterns were directly produced by actively defining the gain distribution in the ceramic, generating 4-W shallow crater-shape beams and 3.9-W quasi-top-hat beams, corresponding to a slope efficiency of 22.0% and 22.7%, respectively. Such optical vortices and tailored spatial intensity profiles in the 3-µm spectral region will enable novel applications, such as super-resolution molecular spectroscopy and material processing.

Reduction of thermal effects in a 2.7-µm Er:Y2O3 ceramic laser with annular pumping.

Reduction of thermal effects is a challenging aspect for power scaling of 2.7-µm bulk Er-lasers due to the large quantum defect when pumping at ∼ 0.97 µm. Here, we demonstrate that thermal effects in an Er:Y2O3 ceramic laser can be significantly reduced pumping by an annular beam, thus improving the continuous-wave (CW) laser performance in the 3-µm spectral range. The excitation conditions of the TEM00 mode were determined theoretically by taking into account the propagation characteristics of the annular pump beam. For a comparison, the temperature and stress distributions are at first theoretically studied with three different pump configurations. In the experiment, output power of the Er:Y2O3 ceramic laser improved by ∼ 60% by changing the pump beam from coventional quasi-top-hat to a designed annular one. This work, as a proof-of-principle study, indicates the potential of power scaling of the 2.7-µm bulk Er-lasers pumping with an annular beam.

High power and efficient operation of a Ho:Y2O3 ceramic laser with over 210 W of output power at 2.1 µm.

We report on power scaling and efficient operation of a Ho:Y2O3 ceramic laser at 2.1 µm in-band pumped with an incoherently beam combined high power and narrow-linewidth Tm fiber source at 1931.2 nm. The 0.5 at.% Ho3+ doped Ho:Y2O3 ceramic is fabricated in-house with scattering loss of < 0.25% cm-1. Up to 210.5 W of continuous-wave output power has been generated at 2117 nm for 366 W absorbed pump power shaped with a one-dimensional top-hat profile, corresponding to a slope efficiency of 60.0% with respect to the absorbed pump power. A slope efficiency of 67.5% has been demonstrated with 160 W of output power using a circular beam pump configuration. Results presented in this work verify the superior power scaling capability of a Ho:Y2O3 ceramic laser with high efficiency at ∼2.1 µm.

SESAM mode-locked Tm:Y2O3 ceramic laser.

We demonstrate a widely tunable and passively mode-locked Tm:Y2O3 ceramic laser in-band pumped by a 1627-nm Raman fiber laser. A tuning range of 318 nm, from 1833 to 2151 nm, is obtained in the continuous-wave regime. The SESAM mode-locked laser produces Fourier-transform-limited pulses as short as 75 fs at ∼ 2.06 µm with an average output power of 0.26 W at 86.3 MHz. For longer pulse durations of 178 fs, an average power of 0.59 W is achieved with a laser efficiency of 29%. This is, to the best of our knowledge, the first mode-locked Tm:Y2O3 laser in the femtosecond regime. The spectroscopic properties and laser performance confirm that Tm:Y2O3 transparent ceramics are a promising gain material for ultrafast lasers at 2 µm.

Single longitudinal mode and widely tunable Er:Y2O3 ceramic laser at ~ 2.7 μm

Single longitudinal mode and widely tunable Er:Y2O3 ceramic laser at ~ 2.7 μm

Power scaling of diode-pumped Er:Y2O3 ceramic laser at 2.7 μm

We report on the high-power and room temperature operation of an Er:Y2O3 ceramic laser at ∼2.7 μm based on home-developed high optical quality ceramic samples. Pumped directly into the upper laser level with a spectrally narrowed 976 nm laser diode beam shaped to have a 1D top-hat profile, the laser-generated 13.4 W of CW output power with a slope efficiency of 16.0% with respect to absorbed pump power. In a modified resonator design, a lasing slope efficiency of 23.7% has been demonstrated. To our knowledge, this represents the highest power at ∼2.7 μm spectral region from a room temperature sesquioxide laser.

Efficient Resonantly-Pumped Tm:Y2O3 Ceramic Laser

Efficient Resonantly-Pumped Tm:Y2O3 Ceramic Laser

High-power 1640 nm Er:Y2O3 ceramic laser at room temperature.

We report on the high-power operation of an Er:Y2O3 ceramic laser at approximately 1.6 µm using a low-scattering-loss, 0.25 at. % Er3+-doped ceramic sample fabricated in-house via a co-precipitation process. The laser is in-band pumped by an Er, Yb fiber laser at 1535.6 nm and generates 10.2 W of continuous-wave (CW) output power at 1640.4 nm with a slope efficiency of 25% with respect to the absorbed pump power. To the best of our knowledge, this is the first demonstration of an approximately 1.6 µm Er:Y2O3 laser at room temperature. The prospects for further scaling of the output power and lasing efficiency via low Er3+ doping and reduced energy-transfer upconversion are discussed.

High Power Single Frequency Tm:Y2O3 Ceramic Laser at 2015 nm

We report on high power, single-frequency operation of a compact Tm:Y <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ceramic laser in 2 μm spectral region employing a volume Bragg grating in a simple linear resonator to serve simultaneously as a resonator mirror and mode selector. The home developed laser quality Tm:Y <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ceramic sample has a Tm doped concentration of 2 at.% and pumped with a fiber coupled 793 nm laser diode. Up to 1.5 W of CW single frequency output power at 2014.9 nm has been generated, corresponding to a slope efficiency of 37.9% with respect to absorbed pump power. M <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> factor of the output beam was measured to be ∼1.03.

Stable Q-switched mode-locking of an in-band pumped Ho : Y2O3 ceramic laser at 2117 nm

We have demonstrated stable Q-switched mode-locked operation of an in-band pumped Ho : Y2O3 ceramic laser at 2117 nm by using an InGaAs/GaAs-based saturable absorber. An average output power of 330 mW is reached for 2.7 W of absorbed pump power with stable mode-locked pulses having a 98.9-MHz repetition rate and 100% modulation depth embedded inside Q-switched envelopes of ∼1.7-μs duration. The duration of the mode-locked pulses is estimated to be less than 1.5 ns.

High-efficiency CW and passively Q-switched operation of a 2050 nm L-shaped Tm3+:Y2O3 ceramic laser in-band fiber-laser pumped at 1670 nm

High-efficiency CW and passively Q-switched operation of a 2050 nm L-shaped Tm3+:Y2O3 ceramic laser in-band fiber-laser pumped at 1670 nm

High Peak Power Acousto-Optically Q-Switched Ho:Y2O3 Ceramic Laser at 2117 nm

We demonstrate high peak power acousto-optically (AO) Q-switched operation of a 2117 nm Ho:Y2O3 ceramic laser pumped with a high brightness fiber laser source at 1931 nm. Lasing output characteristics at different pulse repetition rate are examined, and over 20 W of average output power has been generated at a pulse repetition frequency (PRF) of 10 kHz for 42.6 W of absorbed pump power. The corresponding pulse energy, pulse duration and peak power are 2.0 mJ, 33.1 ns and 60 kW, respectively. The prospects for further improvement in output performance are discussed.

MXene Ti3C2Tx saturable absorber for passively Q-switched mid-infrared laser operation of femtosecond-laser–inscribed Er:Y2O3 ceramic channel waveguide

Abstract We report on an Er:Y2O3 ceramic channel waveguide laser operating at continuous-wave and passively Q-switched regimes, for the first time to the best of our knowledge. The Er:Y2O3 ceramic channel waveguide has been fabricated by a femtosecond laser direct-writing technique. The maximum output power reached 123.5 mW in continuous-wave mode with a slope efficiency of about 21%, and the lasing behavior has been found simultaneously at 2710.28, 2716.76, and 2723.18 nm. We have further fabricated an MXene Ti3C2Tx saturable absorber mirror to operate the Er:Y2O3 waveguide in passively Q-switched regime. At the same time, property of the MXene Ti3C2Tx saturable absorber has been characterized, and nonlinear saturable absorption of the saturable absorber has also been measured. The average output power is about 67.6 mW, and the shortest pulse width is about 58.1 ns. This work indicates that femtosecond laser direct writing is a reliable technique for processing mid-infrared ceramic waveguides, and MXene Ti3C2Tx is promising for operating pulsed mid-infrared lasers.

Ho3+:Y2O3 ceramic laser generated over 113 W of output power at 2117 nm.

We demonstrate efficient laser operation using a Ho:Y2O3 ceramic with low scattering loss and excellent optical quality fabricated in-house through an improved technique in support of high-power laser operation. The Ho:Y2O3 ceramic laser was in-band pumped by a Tm-fiber laser of 1931 nm at room temperature. With an optically polished but uncoated sample of 0.5 at. % Ho3+ doping, up to 113.6 W continuous-wave output power at 2117 nm has been generated with a slope efficiency of 55.6% with respect to the absorbed pump power. To the best of our knowledge, this is the highest output power achieved with a Ho-doped ceramic.

Single-mode oscillations of diode-pumped mid-infrared Er:Y2O3 ceramic microchip lasers at 2.7 μm.

Two compact mid-infrared microchip lasers at 2717 and 2740 nm have been demonstrated using a Er:Y2O3 ceramic as laser gain medium with thickness of 800 μm, for the first time to our knowledge. Under a 976-nm diode laser pumping, the 2717 nm microchip laser with linewidth of about 0.16 nm is achieved with a maximum output power of 234.8 mW and slope efficiency of about 10.9%. The laser beam quality expressed by M2 factor is measured to be about 1.23 and 1.45 in x and y directions. A single wavelength at 2740 nm with linewidth of about 0.15 nm is also achieved with maximum output power of 102 mW and slope efficiency of about 4.9%. Beam quality of the 2740 nm laser is found to be about 1.15 and 1.26 in x and y directions. Using a mechanical chopper to modulate the pump laser for thermal mitigation, the maximum output powers can be further improved to 312 mW for 2717 nm laser and 145 mW for 2740 m laser at higher pump powers. Such a mid-infrared microchip laser source with very compact size could be have great potential in various eye-safety-related applications.

2.7 μm optical vortex beam directly generated from an Er:Y2O3 ceramic laser.

We demonstrate, to the best of our knowledge, the first direct vortex beam generation in the 3μm spectral region by employing an Er:Y2O3 ceramic laser. Controllable handedness with high purity is achieved by introducing asymmetric cavity loss and reducing the number of longitudinal modes. The average orbital angular momentum of the produced scalar vortex beam is quantitatively evaluated to be 0.95ħ for the LG0,+1 mode and -0.94ħ for the LG0,-1 mode. The corresponding optical spectrum is centered at 2710.8 and 2710.5nm, respectively.