High Efficient Continuous-Wave Ho：Y/kG Laser Pumped by a Diode-pumped Tm：YLF Laser at Room Temperature

DUAN Xiao-Ming, YAO Bao-Quan, ZHANG Yun-Jun, SONG Cheng-Wei, GAO Jing, JU You-Lun, WANG Yue-Zhu（ National Key Laboratory of Tunable Laser Technology, Harbin Institute of Technology, Harbin 150001）     

In-Band Pumped High Power Ho：YAG Ceramic Laser by a Tm：YLF Laser

High-power 2 μm lasers are promising candidates for a variety of applications including remote sens- ing, wind lidar, and medicine as well as mid- infrared generation via pumping of optical parametric oscillators. Due to the advantages of low quantum defects and high efficiency, resonantly pumped Ho- doped lasers have attracted great attention. Ho：YAG single crystals have also been widely studied to ob- tain cw and Q-switched laser operation in the 2 μm wavelengths range.     

Diode Pumped Operation of Tm,Ho：YVO4 Microchip Laser

A cryogenic and room-temperature diode pumped Tm,Ho：YVO4 microchip laser with 0.5 mm crystal length lasing around 2μm is demonstrated for the first time to our knowledge. Under cryogenic temperature of 77 K, as much as 1.2 W output and slope efficiency of 35% with respect to absorbed pump power are obtained. At temperature of 5℃ the maximum output power of 48mW is obtained at an absorbed pump power of 503 mW, representing a 9.5% optical to optical conversion efficiency. In addition, as much as 8 mW single-frequency output lasing at 2052.6 nm is achieved at room temperature of 15℃.     

A High Efficient Stable Intracavity Doubling Nd：YAG Laser Pumped by a Laser Diode

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A Continuous-Wave Ho：YA103 Laser with Output 8.5 W Pumped by a 1.91μm Laser at Room Temperature

A cw high efficient Ho：YAI03 laser pumped by 1.91 μm diode-pumped Tm：YLF laser at room temperature is realized. The maximum output power reaches 8.5 W when the incident pump power is 15.6 W. The slope efficiency is 63.7%, and the Tm：YLF to Ho：YAP optical conversion efficiency is 54.5%. The laser wavelength is 2118.3nm when the transmission of output coupler is 30%. The beam quality factor is M2 -1.39 measured by the traveling knife-edge method.     

High Power Continuous-Wave Diode-End-Pumped 1.34-μm Nd：GdVO4 Laser

A high power cw all-solid-state 1.34-μm Nd：GdVO4 laser is experimentally demonstrated. With a diode-double-end-pumped configuration and a simple plane-parallel cavity, a maximum output power of 27.9 W is obtained at incident pump power of 96 W, introducing a slope efficiency of 35.4%. To the best of our knowledge, this is the highest output power of diode-end-pumped 1.3-μm laser. With the experimental data, the thermal-stress- resistance figure of merit of Nd：GdVO4 crystal with 0.3 at% Nd^3＋ doped level is calculated to be larger than 9.94 W/cm.     

Compact High—Power Blue Light from a Diode—Pumped Intracavity—Doubled Nd：YAG Laser

We report an efficient continuous wave(cw) operationof 946nm and 473nm laser beams generated from a diodepumped composte Nd:YAG rod.A very simple compact linear cavity was employed with cavity length of 35mm.A composite Nd:YAG laser rod was used to release thermal effects.The maximum cw output of 3.3W at 946nm was obtained with slope efficiency of 22% at incident pump power of 17.5W.By intracavity doubling with an LBO crystal,as much as 590mW of single-ended blue output at 473nm was achieved with an optical-optical conversion efficiency of 3.4%.The total blue output would be 1.06W with overall conversion efficiency of 6.1% if the lasers emitted in both the directions were taken into account.     

Dynamics of Efficiency Change by Temperature in Diode Pumped Nd：YAG Heat Capacity Laser

We investigate the influence of temperature on the efficiency of diode pumped Nd：YAG heat capacity laser is studied. It is shown that the efficiency of such a laser system is greatly reduced at higher temperature. This bad behaviour is mainly caused by the doped-ion redistribution among various Stark levels of the ground state, and by a thermal equilibrium between the upper laser level and the pump level. Meanwhile, the thermal excitations from the ground state to the lower laser level also play a role. We derive a model to describe those effects, with the considerations of emission spectrum of laser diodes, the subtle Stark structures and the linewidth of absorption and of simulated-emission.     

Q-Switched Tm：YAG Laser Intracavity-Pumped by a 1064nm Laser

We report a Q-switched 2-μm Tm：YAG laser based on intracavity-pumped by a 1064-nm Nd：YAG laser operating at room temperature for the first time. An average output power of 5.1W is obtained with the repetition rate of 30kHz and a pulse width of 300ns. In addition, we demonstrate a 12.5-W continuous-wave 2-μm Tm：YAG laser, which is, to our best knowledge, the highest power for intracavity-pumping configuration.     

Tm：Ho：YLF Amplifiers at 2.049 μm with a Tm：Ho：GdVO4 Oscillator

We report cw diode-pumped cryogenic Tm:Ho:YLF amplifiers at 2.049μm with a Tm:Ho:GdVO4 oscillator. Not only the single- and double-pass, but also the single- and double-end pump amplifiers with a 10-mm-length medium are compared. A measured maximum small-gain coetfficient of 1.3 cm^-1 is achieved for the double-pass and double-end pump amplifier. The maximum extracted power of 8.5 W, the gain of 3.2 and extracted etfficiency of 32% have been obtained with an input signal power of 3.9 W. The difference of the hosts in the oscillator and amplifier has little influence on the characteristic of the amplifier output. Additionally, the extracted etfficiency of the quasi-continuous-wave amplifier with a repetition rate of 10kHz is the same as the cw one.     

High Power Continuous-Wave and Acousto-Optic Q-Switched Nd：GdVO4 Laser Operated at 912 nm

We present a high power and efficient operation of the ^4F3/2 → ^4I9/2 transition in Nd：GdVO4 at 912nm. In the cw mode, the maximum output power of 8.6 W is achieved when the incident pump power is 40.3 W, leading to a slope efficiency of 33.3% and an optical-optical efficiency of 21.3%. To the best of our knowledge, this is the highest cw laser power at 912nm obtained with the conventional Nd：GdVO4 crystal. Pulsed operation of 912nm laser has also been realized by inserting a small aeousto-optie （A-O） Q-Switch inside the resonator. As a result, the minimal pulse width of 20ns and the average laser power 1.43 W at the repetition rate of lOkHz are obtained, corresponding to 7.1 kW peak power. We believe that this is the highest laser peak power at 912nm. Furthermore, duration of 65ns has also been acquired when the repetition rate is 100 kHz.     

Violet to Infraned Multiwavelength Generation in Periodically Poled Lithium Niobate Pumped by a Q—Switched Nd：YVO4 Laser

Six output wavelengths from violet to infrared have been observed simultaneously from an all-solid-state laser pumped optical parametric oscillator in a periodically poled lithium niobate crystal.The output wavelengths can be tuned by varying the quasi-phase matched period and/or temperature.The pump laser is a diode-pumped pasive Q-switched Nd:YVO4 laser operated at 1064nm.Using a crystal with a 29.9μm grating period,we measured six wavelengths at 448,515,532,630,773 and 1546nm and obtained efficient output.We explain the multiwavelength generation by multiwave coupling theory.This phenomenon may have novel applications in photonic devices.     

High Efficiency Multi-kW Diode-Side-Pumped Nd：YAG Laser with Reduced Thermal Effect

We demonstrate a high efficiency multi-kW diode-side-pumped Nd：YAG laser. High cooling efficiency of the diode-side-pumped module in the laser is achieved. The middle portion of the Nd：YAG rod in the module is cooled by a coolant jet with screwed side surface, and the end-caps of the rod without screwed side surface are cooled by Au coated on the surface. The thermal effect of the laser rod is reduced, which leads to high output power with high optical-optical conversion efficiency. By using three identical Nd：YAG laser modules, an output power of 4.2 kW and beam quality of 58 mm＆#12539;mrad with an optical-optical efficiency of 35% at 1064 nm is obtained in a laser oscillator. By using four identical Nd：YAG laser modules, an output power of 3.1 kW and beam quality of 17 mm＆#12539;mrad with an optical-optical efficiency of 25.8% is demonstrated in a master oscillator power-amplifier system.     

A Continuous-Wave Ho:YAlO3 Laser with Output 8.5W Pumped by a 1.91μm Laser at Room Temperature

A cw high efficient Ho:YAlO₃ laser pumped by 1.91μm diode-pumped Tm:YLF laser at room temperature is realized. The maximum output power reaches 8.5W when the incident pump power is 15.6W. The slope efficiency is 63.7%, and the Tm:YLF to Ho:YAP optical conversion efficiency is 54.5%. The laser wavelength is 2118.3nm when the transmission of output coupler is 30%. The beam quality factor is M²~1.39 measured by the traveling knife-edge method.     

Efficient Long Wave IR Laser from Ho：YAG 2 μm Pumped ZnGeP2 Optical Parametric Oscillator

An efficient high power long wave infrared laser based on ZnGeP2 optical parametric oscillator pumped by a 2.09μm Tm：YLF/Ho：YAG laser at 10KHz pulse repetition rate is reported. The pump to idler conversion efficiency is 8% at 15.6W Ho pump power level and a quantum efficiency of 31% when the 1idler wavelength is tuned at 8.08μm. The wavelength tuning range from 8-9.1μm is also achieved by rotating the ZGP crystal.     

Design of a Compact Diode-Pumped Intracavity-Doubled Nd：GdVO4 Laser with 820-mW Red Light

We report a design of diode-pumped high power Nd:GdVO4/LBO red laser with a compact linear cavity, which can output 820-mW red light at 67Onto with an optical conversion efficiency of 9.6%. The maximum output power of the fundamental light at 1.34μm was 4W with a slope efficiency of 45%.     

A Stable Diffusion-Bonded Tm：YLF Bulk Laser with High Power Output at a Wavelength of 1889.5 nm

A high power diode-pumped diffusion-bonded Tm：YLF laser operating at 1889.5nm with a FWHM linewidth of less than 0.1 nm is reported. A Brewster plate and two Fabry-Perot etalons are inserted in the laser cavity for spectral narrowing and stabilization. Under an incident pump power of 136.8 W, 46.1 W of output power is achieved, corresponding to an optical-to-optical conversion efficiency of 33.7% and a slope efficiency of 42.8%. The laser wavelength shift of only 0.07nm with the incident pump power from 20.1 W to 136.8W is observed. The M2 factor at maximum output power is calculated to be 2.3 in the x-axis and 2.0 in the y-axis, respectively.     

8.30 μm singly resonant ZnGeP2 optical parametric oscillators pumped by a Tm,Ho:GdVO4 laser

A single resonator 8.30 μm ZnGeP₂ (ZGP) optical parametric oscillators (OPO) was reported in the paper. The OPO was pumped by a 10.2-W Tm,Ho:GdVO₄ laser at 8 kHz in a Q-switch mode, a 170-mW idler was obtained at 8.30 μm, and the output power of the idler and signal wave was 1.0 W, corresponding to an optical-optical conversion efficiency of 10.3% and a slope efficiency of 20.9%. Tm,Ho:GdVO₄ laser was pumped by a 30-W fiber-coupled laser diode (LD) at the center wavelength of 801 nm. The output wavelength of Tm,Ho:GdVO₄ laser was at 2.05 μm, and the energy per pulse of 1.28 mJ in 18 ns was achieved at 8 kHz with the peak power of 71.1 kW.     

Wildly Tunable,High-Efficiency MgO：PPLN Mid-IR Optical Parametric Oscillator Pumped by a Yb-Fiber Laser

We demonstrate a wildly tunable, high-eFficiency mid-infrared （mid-IR） output-coupled single resonant optical parametric oscillator （OC-SRO） pumped by a Yb-fiber laser. The compact mid-infrared source employs a 50- mm-long, multi-grating MgO-doped periodically poled lithium niobate （MgO-PPLN） crystal, providing as much as 1.73 W idler power at 3.012#m, and 1.27W signal power at 1645nm, corresponding to an overall conversion efficiency of 41.7% and a slope efficiency of 77.9%. In particular, the mid-infrared output power of 1.03 W and 0.67W are obtained at 3.7μm and 3.9μm, respectively, with an optical-to-optical conversion efficiency of 14.3% and 9.3%. Furthermore, the idler light is tunable from 3 μm to 3.9 μm by changing the periods from 31 to 28.5μm, with the output power 〉1 W over 78% of the tuning range. Our experimental results are pump power limited and further mid-IR power and conversion efficiency could be obtained with a suitable high-power pump source. The total OC-SRO output power rms at 2.6 W is about 0.6% during 2 h measurement.     

High-Power Continuous-Wave Diode-End-Pumped Intracavity Frequency Doubled Nd：YVO4 Laser at 671 nm with a Compact Three-Element Cavity

We report a high-power high-efficient continuous-wave （cw） diode-end-pumped Nd：YVO4 1342-nm laser with a short plane-parallel cavity and an efficient cw intracavity frequency-doubled red laser at 671 nm with a compact three-element cavity. At incident pump power of 20.6 W, a maximum output power of 7 W at 1342 nm is obtained with a slope effciency of 37.3%. By inserting a type-Ⅰ critical phase-matched LBO crystal as intracavity frequencydoubler, a cw red output as much as 2.85-W is achieved with an incident pump power of 16.9 W, inducing an optical-to-optical conversion efficiency of 16.9%. To the best of our knowledge, this is the highest output of diodepumped solid-state Nd：YVO4 red laser. During half an hour, the red output is very stable, and the instability of output power is less than 1%.