Lu2O3 Ceramic Laser Research Articles

Passively Q-switched and broadly tunable continuous-wave operations of a 2-μm Tm3+:Lu2O3 ceramic laser upconversion pumped at 1.064 μm

We report passively Q-switched and broadly tunable continuous-wave operations of a trivalent thulium ion-doped Lu2O3 ceramic laser near 2 μm by employing upconversion pumping at 1 μm. Upconversion pumping was performed with a commercial 1064-nm Yb:fiber laser and nonlinear absorption of up to 41 % was obtained. In the continuous wave case, a four-mirror x-cavity generated as high as 257 mW of output power at 2.06 μm with a power slope efficiency of 12 % with respect to the incident pump power. Tuning performance was further investigated with a quartz birefringent tuning plate and broad, continuous tuning was obtained in the 1950–2090 nm wavelength range. In addition, passively Q-switched operation was demonstrated with a semiconductor saturable absorber, yielding stable, 4.15-μs-long pulses at the pulse repetition frequency of 28.8 kHz.

Self-Q-switched and widely tunable continuous-wave operation of a Tm3+:Lu2O3 ceramic laser near 2 μm

We report, for the first time to our knowledge, self-Q-switched (SQS) operation of a Tm3+:Lu2O3 ceramic laser near 2 μm based on the 3F4→3H6 optical transition. By careful optimization of cavity focusing, SQS operation could be achieved at several curved mirror separations without any external modulator and the laser delivered 9.7-μs pulses at the wavelength of 2091 nm with a pulse repetition rate of 26 kHz. In the experiments, a tight-focusing resonator design was further employed to achieve low-threshold continuous-wave (CW) operation of the laser with lasing threshold pump powers as low as 33 mW. With an incident pump power of 590 mW at 776 nm, a maximum output power of 164 mW was obtained at 2097 nm with a slope efficiency of 30% with respect to the incident pump power. The tuning range of the CW Tm3+:Lu2O3 ceramic laser could be extended up to the wavelength of 2235 nm.

High-Efficiency Diode-Resonantly-Pumped Tm:Lu2O3 Ceramic Laser with Near Diffraction-Limited Beam Quality

High-Efficiency Diode-Resonantly-Pumped Tm:Lu2O3 Ceramic Laser with Near Diffraction-Limited Beam Quality

1940 nm, 1966 nm and 2066 nm multi-wavelength CW and passively-Q-switched operation of L-shaped Tm3+:Lu2O3 ceramic laser in-band fiber-laser pumped at 1670 nm

A Tm3+:Lu2O3 ceramics laser with the L-shaped cavity in-band pumped by a fiber laser at 1670 nm was studied in CW and passively Q-switched multi-wavelength regimes. The CW laser operated at 2066 nm at the weak pump power and self-tuned to 1966 nm and further to 1940 nm at higher pump power. The maximum power in the CW regime at 1940 nm reached 9.5 W, while the average power of 3.6 W was registered in the Q-switched regime with the pulse repetition rate of 110–170 kHz and the pulse duration of 200–240 ns. The Q-switched operation was obtained using a Cr2+:ZnSe saturable absorber. Pulsed regime started at the shortest wavelength of 1940 nm and self-tuned to the double-wavelength of 1940 nm and 1966 nm at higher pump power.

Characterisation of passively Q-switched Yb:Lu2O3 ceramic laser based on graphdiyne absorber

A stable pulsed Yb:Lu2O3 ceramic laser using graphdiyne (GDY) as a saturable absorber has been successfully demonstrated for the first time. The nonlinear optical absorption of GDY was obtained by a homemade picosecond pulsed solid-state laser at ~1064 nm as the source, which indicate the feasibility of GDY in laser modulation. The passively Q-switched Yb:Lu2O3/GDY laser was carried out. A 288 mW maximum average output power was achieved. The obtained repetition rate, pulse energy and peak power were 46.20 kHz, 6.23 μJ and 3.85 W, respectively, when the absorbed pump power of Yb:Lu2O3 ceramics was 2.3 W. These results indicate that GDY is a promising saturable absorption material and is expected to be widely used in ceramic laser.

LD-pumped 2.8 μm Er:Lu2O3 ceramic laser with 6.7 W output power and >30% slope efficiency

We present a high-power, high-efficiency, laser-diode-pumped 2.8 μm Er:Lu2O3 ceramic laser generating record power at room temperature. Careful thermal management and pump-radius enlargement resulted in a continuous-wave output power of 6.7 W at 2845 nm, with a 30.2% slope efficiency. To our knowledge, this is the highest output power and slope efficiency ever achieved from a laser-diode-pumped 3 μm Er-doped ceramic laser. These results confirm the possibility of generating high-output-power, high-efficiency laser using transparent ceramics.

Comparative study of Yb:Lu3Al5O12 and Yb:Lu2O3 laser ceramics produced from laser-ablated nanopowders

We present a comparative study of two Lu-based oxide ceramics doped with Yb3+ ions, namely Yb:Lu3Al5O12 (garnet) and Yb:Lu2O3 (sesquioxide), promising for thin-disk lasers. The ceramics are fabricated using nanopowders of 3.6 at.% Yb:Lu2O3 and Al2O3 produced by laser ablation: Yb:Lu3Al5O12 – by vacuum sintering at 1800 °C for 5 h with the addition of 1 wt% TEOS as a sintering aid, and Yb:Lu2O3 – by vacuum pre-sintering at 1250 °C for 2 h followed by Hot Isostatic Pressing at 1400 °C for 2 h under Ar gas pressure of 207 MPa. The comparison includes the structure, Raman spectra, transmission, optical spectroscopy and laser operation. The crystal-field splitting of Yb3+ multiplets is revealed for Lu3Al5O12. A continuous-wave (CW) Yb:Lu3Al5O12 ceramic microchip laser generates 5.65 W at 1031.1 nm with a slope efficiency of 67.2%. In the quasi-CW regime, the peak power is scaled up to 8.83 W. The power scaling for the Yb:Lu2O3 ceramic laser is limited by losses originating from residual coloration and inferior thermal behavior.

Mid-IR Optical Parametric Oscillator Based on Periodically Polled LiNbO3 Pumped by Tm3+:Lu2O3 Ceramic Laser

Optical parametric oscillator based on a periodically poled MgO:LiNbO3 crystal pumped by a repetitevely pulsed Tm3+:Lu2O3 ceramics laser at 1966 nm was studied. The OPO average output power up to 530 mW at wavelength of 3.7–4.2 μm was achieved at the ceramics laser power of 7.9 W. The optical-to-optical efficiency of OPO energy conversion was up to 6.7%, and the slope efficiency was up to 8%.

Optical parametric oscillator at MID-IR spectral region based on periodically polled LiNbO3 pumped by Tm3+:Lu2O3 ceramic laser

Optical parametric oscillator at MID-IR spectral region based on periodically polled LiNbO3 pumped by Tm3+:Lu2O3 ceramic laser

Dual-Wavelength Temporal Dynamics of a Gain-Switched 2-μm Tm3+:Lu2O3 Ceramic Laser

We provide a detailed experimental investigation of the energy efficiency and rich temporal dynamics of a gain-switched 2-μm Tm3+:Lu2O3 ceramic laser pumped near 800 nm. A tunable Ti3+:sapphire laser was used to determine the full excitation spectrum and the optimum pumping bands for the 1.5% Tm3+:Lu2O3 ceramic gain medium. These bands were centered at 774, 796, and 811 nm. The highest output pulse energy was obtained when the pump wavelength was set to 796 nm. In the experiments, a free-running x-cavity was used to investigate the energy efficiency of the Tm 3+:Lu2O3 ceramic laser. Extracavity grating-dispersed output and prism-tuned resonator were used to further assess the role of cross-relaxation for the 1.5% Tm3+:Lu2 O3 ceramic. Finally, we demonstrate that as the pump energy was increased, a transition occurred from single-wavelength output (2068 nm) to dual-wavelength multipulse output (2068 and 1968 nm). We performed systematic temporal and spectral characterization measurements by using the free-running resonator, extracavity-grating-dispersed laser output, and prism-tuned resonator to investigate how the laser pulses at 1968 and 2068 nm evolved in time. A plane-wave rate equation model was further used to investigate the temporal dynamics of the Tm3+:Lu2O3 ceramic laser and provided predictions in qualitative agreement with experimental data.

High Power and Short Pulse Width Operation of Passively Q-Switched Er:Lu2O3 Ceramic Laser at 2.7 μm

Using a low non-saturable loss Bragg-reflector-based semiconductor saturable mirror, a passively Q-switched Er:Lu2O3 ceramic laser at 2.7 μm demonstrated short pulse-width and efficient operation, generating stable pulses of 70 ns pulse-width and ~71 kHz repetition rates. Over 692 mW of average output power was measured, corresponding to a pulse energy of ~9.8 μJ. In a modified resonator design of reduced round-trip time, pulses of 32 ns duration were generated. The achieved results suggest that Er:Lu2O3 ceramic could be a promising gain medium for efficient and high power pulsed laser generation at 2.7 μm. The prospects for further improvement in laser performance at this wavelength are discussed.

1200 nm pumped Tm3+:Lu2O3 ceramic lasers.

We report on an experimental demonstration of a 1200-nm pumped Tm3+:Lu2O3 ceramic laser. By using a gain-switched, tunable Cr4+:forsterite laser, the excitation spectrum was measured, with optimum pumping bands centered near 1198nm, 1204nm, and 1211nm. The highest slope efficiency of 21.5% was obtained at the pump wavelength of 1204nm. Comparative energy efficiency measurements performed near 1200-nm and 800-nm pumping further showed that nearly 40% improvement was obtained in slope efficiency measured with respect to the incident pump energy for 1200-nm pumping. A transition was further observed from single-wavelength operation at 2066nm to dual-wavelength operation near 2066nm and 1967nm for absorbed pump energies above 50μJ. In this regime, two consecutive output pulses were observed in the time domain. The shortest temporal duration of the first pulse was 1.1μs at the incident pulse energy of 105μJ. The duration and build-up time of the second pulse remained around 5.9μs and 18.5μs. We believe that the improved energy efficiency demonstrated for the 1.5% Tm3+:Lu2O3 ceramic with 1200-nm pumping can be used as an alternative scheme for the excitation of Tm3+:Lu2O3 ceramic lasers.

Optimization of laser emission at 2.8 μm by Er:Lu2O3 ceramics.

We have demonstrated the continuous-wave operation of a highly efficient 2.8 μm Er-doped Lu2O3 ceramic laser at room temperature. An Er:Lu2O3 ceramic with a doping concentration of 11 at.% afforded a slope efficiency of 29% and an output power of 2.3 W with pumping at 10 W. To our knowledge, these are the highest slope efficiency and output power obtained to date for an Er:Lu2O3 ceramic laser at 2.8 μm. In addition, we prepared ceramics with various doping concentrations and determined their emission cross sections by fluorescence lifetime measurements and emission spectroscopy.

Passive Q-switching of ∼2.7 µm Er:Lu2O3 ceramic laser with a semiconductor saturable absorber mirror

We demonstrate the passively Q-switched operation of an Er:Lu2O3 ceramic laser at ∼2.7 µm for the first time, to the best of our knowledge. By using a semiconductor saturable absorber mirror (SESAM), stable pulse trains with a repetition rate of 20–33.3 kHz are produced in a compacted v-shaped resonator. The pulse duration (FWHM), pulse energy, and peak power are 660 ns, 1.8 µJ, and ∼2.73 W, respectively, at 33.3 kHz repetition rate. Prospects for further improvements in terms of laser performances are discussed.

Efficient continuous wave and quasi-continuous wave operation of a 2.8 μm Er:Lu2O3 ceramic laser.

We have demonstrated a highly efficient 2.8 μm Er-doped Lu2O3 ceramic laser and investigated the lasing dynamics by time-resolved spectroscopy. During room-temperature continuous wave operation, a slope efficiency of 22% was achieved with a high-quality transparent ceramic. To our knowledge, this is the highest slope efficiency obtained by an Er:Lu2O3 ceramic laser. In addition, an output peak power of 1.2 W was obtained during quasi-continuous wave operation. Time-resolved spectroscopy showed that the emission wavelengths exhibited a red shift from 2715 to 2845 nm, which indicated that continuous wave operation may be possible at 2740 and 2845 nm.

Highly stable self-pulsed operation of an Er:Lu2O3 ceramic laser at 2.7 µm

We report on the highly stable self-pulsed operation of a 2.74 µm Er:Lu2O3 ceramic laser pumped by a wavelength locked narrow bandwidth 976 nm laser diode. The operating pulse repetition rate is continuously tunable from 126 kHz to 270 kHz depending on the pump power level. For 12.3 W of absorbed diode pump power, the Er:Lu2O3 ceramic laser generates 820 mW of average output power at a 270 kHz repetition rate and with a pulse duration of 183 ns. The corresponding pulse-to-pulse amplitude fluctuation is estimated to be less than 0.7%. In the continues-wave (CW) mode of operation, the laser yields over 1.3 W of output power with a slope efficiency of 11.9% with respect to the 976 nm pump power.

Efficient laser operation based on transparent Nd:Lu2O3 ceramic fabricated by Spark Plasma Sintering.

Efficient laser operation of Nd:Lu2O3 ceramic fabricated by Spark Plasma Sintering (SPS) was demonstrated. Transparent Nd:Lu2O3 ceramic was successfully fabricated by Spark Plasma Sintering and its laser experiment was done. On the 4F3/2 to 4I11/2 transition, the obtained maximum output is 1.25W at the absorbed pump power of 4.15W with a slope efficiency of 38% and two spectral lines at 1076.7nm and 1080.8nm oscillated simultaneously. The slope efficiency of 38% is near two times higher than the previously demonstrated SPSed Nd:Lu2O3 ceramic lasers. On the 4F3/2 to 4I13/2 transition, the laser operated at the wavelength of 1359.7nm and the maximum output of 200mW was obtained at the absorbed pump power of 2.7W.

2.92 µm Cr2+:CdSe single crystal laser pumped by a repetitively pulsed Tm3+:Lu2O3 ceramics laser at 2.066 µm

A laser oscillator based on Cr2+:CdSe single crystal pumped by 2.066 µm radiation of a Tm3+:Lu2O3 ceramic laser was created and investigated. Repetitively pulsed oscillations at a wavelength of 2.92 µm with a bandwidth of 80 nm were demonstrated. The output power was up to 350 mW at 10 kHz repetition rate with a pulse duration of ~200 ns in the good-quality beam.

Room temperature continuous-wave laser performance of LD pumped Er:Lu₂O₃ and Er:Y₂O₃ ceramic at 2.7 μm.

We report the demonstration of continue wave operation of diode end-pumped Er:Y2O3 and Er:Lu2O3 ceramic lasers operating at 2.7 μm at room temperature. The maximum output power of 320 mW and 611 mW was obtained from the Er:Y2O3 and Er:Lu2O3 ceramic lasers, with slope efficiency of 6.5% and 7.6%, respectively. Characteristics of Red-shift in lasing wavelength of the ceramic lasers was investigated and discussed. The study indicates that under 967 nm and 976 nm LD pumping, 15 at.% Er-doped Lu2O3 ceramic exhibit a better performance than that of Y2O3 at room temperature.

6-GHz, Kerr-lens mode-locked Yb:Lu_2O_3 ceramic laser for comb-resolved broadband spectroscopy

A laser diode (LD)-pumped, 6-GHz repetition rate, ytterbium (Yb)-doped Lu2O3 ceramic Kerr-lens mode-locked laser is described. A bow-tie ring cavity enabled the generation of femtosecond pulses centered at a wavelength of 1076 nm with an average power of 10 mW. The pulse duration after an amplifier was 161 fs whereas the transform-limited pulse duration directly from the oscillator was 148 fs. The repetition frequency was sufficiently high for each longitudinal mode to be spectrally resolved by a commercially available optical spectrum analyzer. The developed laser was successfully applied to the absorption spectroscopy of metastable helium4 and demonstrated the suitability of the system as a source for comb-resolved broadband spectroscopy.