Efficient High-Power Ho:YAG Laser Pumped by Dual-End-Diode-Pumped Tm:YLF Laser

We report a Ho:YAG (Ho-doped yttrium aluminum garnet) laser pumped by a dual-end-diode-pumped Tm:YLF (Tm-doped yttrium lithium fluoride) laser to obtain an efficient experimental device with high output-power characteristics. We study the influence of the specific values of the output coupling mirror transmittance, the resonant cavity length, and the radius of curvature of the output coupling mirror on the Ho:YAG laser output characteristics. Under optimum experimental conditions, under which the output coupling mirror transmittance was 30%, the resonant cavity length was 25 mm and the output coupling mirror radius of curvature was 300 mm, and the maximum pumping power of the dual-end-diode-pumped Tm:YLF laser was 15.2 W. We obtain an efficient high-power 2.122-μm laser output of 7.98 W from the Ho:YAG laser. The optical-to-optical conversion efficiency is 52.5%, and the beam quality factor figures are M _x ² ?=?2.89 and M _y ² ?=?2.97.     

A Tm:YLF End-Pumped Acousto-Optic <Emphasis Type="Italic">Q</Emphasis>-Switched Ho:YAG Laser

We report an acoustic Q-switched Ho:YAG laser end-pumped by a 1,908 nm Tm:YLF laser. The doping concentration of Ho:YAG crystal is 2 at.%, and dimensions ø5×20 mm. We measure the pulsedlaser output characteristics of the Ho:YAG laser at different repetition rates (RF). Under optimum experimental conditions, the high-power 2.1 μm output power reaches 4.17 W at a given pump power of 13.25 W and repetition frequency of 8.0 kHz. For a slope efficiency of 16.88%, the corresponding optical-to-optical conversion efficiency reaches 31.47%. We obtain a minimum single pulsed energy of 7.36 mJ and a pulse width of 52.8 ns at a pump power of 10.52 W and repetition rate of 0.5 kHz, with a peak power of 139 kW.     

Narrow Linewidth Tm:YLF Laser with Volume Bragg Grating Dual-End-Pumped by Equidirectional-Polarization Fiber-Coupled Laser Diode

We demonstrate a narrow linewidth Tm:YLF laser with a volume Bragg grating (VBG) that was pumped by an equidirectional-polarization fiber-coupled laser diode using a dual-end-pumping configuration. For an optimized output coupler with a radius of curvature of 150 mm and transmission of 15% at a wavelength of 1.91 μm, the maximum output power was 15.6 W for an absorbed pump power of 51.7 W at 1,907.93 nm, and the output had a narrow linewidth of 0.22 nm. This corresponds to an optical-to-optical conversion efficiency of 30.2% and the slope efficiency was 36.7%.     

An Efficient Continuous Wave Ho:LSO Laser Double-Pass Pumped by a Linewidth-Narrowed Tm Fiber Laser

We report for the first time an efficient continuous wave Ho:LSO laser double-pass pumped by a Tm fiber laser. We achieve a maximum output power equal to 3.6 W at an absorbed pump power of 10.5 W, which corresponds to an optical-to-optical conversion efficiency of 34.3% and a slope efficiency of 59.3%. The output laser wavelength is centered at 2,105.1 nm with a linewidth of ≈2.2 nm, and the beam quality factors \( {\mathrm{M}}_x^2 \) = 1.2 and \( {\mathrm{M}}_y^2 \) = 1.1 measured by the 90/10 knife-edge method.     

An Intracavity-Triggered Passively-Switched Nd:YVO<Subscript>4</Subscript> Laser

We demonstrate an intracavity-triggered passively Q-switched Nd:YVO₄ laser within a diode-end-pumped configuration. We employ a Cr⁴⁺:YAG saturable absorber as the passive Q switch and an Nd:LiYF₄ (YLF) laser as the laser triggering of the Q-switched laser. Since we use the same Cr⁴⁺:YAG crystal and output coupler with the Nd:YVO₄ laser, the Cr⁴⁺:YAG Q switch is triggered inside the Nd:YLF laser cavity. As a result, the timing jitter in standard deviation of Nd:YVO₄ laser can be reduced to 16 ns.     

A High-Power,Long-Wavelength Infrared ZnGeP<Subscript>2</Subscript> Opo Pumped by a <Emphasis Type="Italic">Q</Emphasis>-Switched Tm,Ho:GdVO<Subscript>4</Subscript> Laser

We report a high-power, long-wavelength infrared ZnGeP₂ (ZGP) optical parametric oscillator (OPO) pumped by a Q-switched Tm,Ho:GdVO₄ laser. The wavelength tuning range of 7.8–9.9 μm is realized by rotating the external angle of the ZGP crystal. We obtain an output power over 30 mW across the whole wavelength range and achieve a 1.71 W output power at 8.08 μm by transmitting the OPO parameters, corresponding to an idler laser slope efficiency of 12.1%.     

A Novel 1,066 nm Nd:Gd<Subscript>0<Emphasis Type="Italic">.</Emphasis>69</Subscript>Y<Subscript>0<Emphasis Type="Italic">.</Emphasis>3</Subscript>NbO<Subscript>4</Subscript> Passively <Emphasis Type="Italic">Q</Emphasis>-Switched Pulse-Burst Laser

We demonstrate for the first time a Cr⁴⁺:YAG passively Q-switched 1066 nm pulse-burst laser under 879 nm direct pump with a novel Nd:Gd_0.69Y_0.3NbO₄ crystal. The output laser characteristics with different pump repetition rates and different Cr⁴⁺:YAG initial transmission are studied. Without the Cr⁴⁺:YAG, we obtain a maximum output energy of 2.55 mJ at an absorbed pump energy of 5.79 mJ with the highest 48% slope efficiency. The pulse-burst laser contains a maximum of 7 pulses for a Cr⁴⁺:YAG initial transmission of 55% and a pump repetition rate of 1 kHz. The single-pulse energy and narrowest pulse width reach 160 μJ and 5.5 ns at 38.2 kHz, with a peak power of 32 kW.     

Acousto-optic <Emphasis Type="Italic">Q</Emphasis>-switched Tm:Ho:YbAG laser pumped at 1678 nm

Acousto-optic Q-switched lasing has been obtained for the first time in a Tm:Ho:YbAGcrystal. The laser output power is analyzed as a function of the laser pulse repetition rate. It is found that at rates above 30 kHz the laser slope efficiency reaches maximum values (~20 to 30%), comparable with the efficiency in the cw mode. The shortest laser pulse width is about 40 ns, and the average output power reaches about 80mW.     

Anti-Stokes Luminescence in LiYF<Subscript>4</Subscript>:Ho<Superscript>3+</Superscript>, Yb<Superscript>3+</Superscript> Ceramics Excited at 1.93 μm

Conversion of IR radiation of a Tm:YAP laser with a wavelength of 1930 nm into visible light by ceramics of composition LiY_(1–x–y) Ho _x Yb _y , where х = 1–5 mol % and y = 0–15 mol %, is demonstrated. It is shown that the threshold power density of IR light visualization decreases with increasing concentration of Ho³⁺ ions, while additional doping of ceramic samples with Yb³⁺ ions changes the anti-Stokes luminescence spectrum. The threshold power density of visualization of the Tm:YAP laser radiation decreases with increasing concentration of holmium ions and is I_thr ≈ 0.8 W cm^–2 in the samples of composition LiYF₄:5%Ho³⁺–15%Yb³⁺.     

Stable and Efficient Pulsed Mid-Infrared Laser Generation from an Er<Superscript>3+</Superscript>-Doped ZBLAN Fiber Laser

We demonstrate a stable and efficient passively Q-switched 2.8 μm Er³⁺-doped ZBLAN fiber laser with a broadband semiconductor saturable absorber mirror. Enabled by the broadband optical modulator, the stable Q-switched fiber laser can deliver a maximum average power over 700 mW with corresponding per-pulse energy of 8.19 μJ and a pulse width of 1.3 μs at a repetition rate of 88.6 kHz under an incident pump power of 3.8 W. In addition, the slope efficiency can reach 22.5%. To the best of our knowledge, this is the highest reported slope efficiency for the passively Q-switched Er³⁺-doped ZBLAN fiber laser.     

All-solid-state CW Nd:LuVO<Subscript>4</Subscript>-LBO laser at 533 nm under direct 888 nm pumping

We report an efficient laser emission on the 1066 nm ⁴ F _3/2 to ⁴ I _11/2 transition in Nd:LuVO₄ under the pump with diode laser at 888 nm. Continuous wave (CW) 11.2 W output power at 1066 nm is obtained under 18.3 W of incident pump power; the slope efficiency with respect to the incident pump power was 71.9%. Moreover, intracavity frequency doubling with LiB₃O₅ (LBO) nonlinear crystal yielded 4.2 W of green light at 533 nm. An optical-to-optical efficiency with respect to the incident pump power was 23.0%.     

High-Pulse-Energy Passively <Emphasis Type="Italic">Q</Emphasis>-Switched 1,123 nm Laser with a Nd:GdYAG Mixed Garnet as Laser Medium

We demonstrate a diode-pumped passively Q-switched Nd:GdYAG mixed garnet laser at 1,123 nm. A Cr⁴⁺:YAG crystal with an initial transmission of 97% is used as the saturable absorber. The maximum average output power is 1.05 W at an absorbed pumping power of 8.12 W. A single-pulse energy can reach up to 78.9 μJ, with a corresponding pulse repetition rate of 13.3 kHz.     

A 100 kHz Narrow-Pulse-Width Mid-Infrared Optical Parametric Oscillator Based on PPMgLN Crystal

We report a narrow pulse width optical parametric oscillator based on periodically poled MgO:LiNbO₃ (PPMgLN) with a high repetition rate under quasi-phase matched conditions. When the maximum pumping power of the 1,064-nm laser was 14.57 W, the acousto-optical (A-O) Q-switch repetition rate was 100 kHz, and the PPMgLN crystal grating period was 29.5 μm. A 1,474-nm signal light output power of 4.21 W and a 3,828 nm idler light output power of 1.547 W were obtained, corresponding to a pulse width of 9.52 ns and 9.65 ns, respectively. The overall optical–optical conversion efficiency was 39.5%. Additionally, by changing the temperature from 25°C to 150°C, a tunable signal wavelength of 1,474–1,499 nm and idler wavelength at 3,676–3,828 nm of the output laser were achieved.     

Temperature dependence of the lasing efficiency of the three-micrometer YAG:Er laser

Experimental results and calculated data on the study of the temperature dependence of the lasing efficiency of the pulsed three-micrometer YAG:Er³⁺ laser in the range T = ?80 ? +80°C are presented. It was shown that a decrease in the laser crystal temperature from room temperature to T = ?80°C leads to an increase in the laser output energy by a factor of 3?4 at the same energy of lamp pumping. Accordingly, the differential lasing efficiency increases (about three times).     

High-power diode-pumped Tm:YLF slab laser

A 2% Tm³⁺-doped LiYF₄(Tm:YLF) slab is double-end-pumped by two laser diode stacks. The pumped volume has a rectangular cross section. The Tm:YLF laser produced 148 W of continuos-wave output at 1912 nm in a beam with M _x ²≈199 and M _y ²≈1.7 for 554 W of incident pump power. The slope efficiency with respect to the incident pump power was 32.6%, and the optical-to-optical efficiency was 26.7%.     

Upconversion CW laser at 284 nm in a Nd:YAG-pumped double-cladding thulium-doped ZBLAN fiber laser

A successful continuous-wave (CW) ultraviolet (UV) laser in a Tm⁺³-doped ZBLAN fiber, operated at 284 nm (¹ I ₆ → ³ H ₆ transition of Tm⁺³) is demonstrated. The excitation uses a four-step upconversion scheme. The pump source is a Nd:YAG laser operated at 1.064 μm. A laser output power of 42 μW continuous wave was obtained for 590 mW of the launched pump power. The slope efficiency with respect to the launched pump power was measured to be 9%. Ultraviolet (at 365 nm) and visible (at 453 and 480 nm) radiation was also observed.     

High-power diode-pumped Tm:YLF laser

A high-power, continuous-wave 3.5% Tm³⁺ doped LiYF₄ (Tm:YLF) laser has been developed. Using two Tm:YLF rods in a single cavity, 55 W of laser output at 1910 nm was obtained with a slope efficiency of 49%. The M² factor was found to be <3. With a single Tm:YLF rod, a maximum laser power of 30 W was obtained with a slope efficiency of 50%. The laser was tuned to the peak absorption wavelength of Ho:YAG of 1907.5 nm by an intracavity quartz etalon with an output power loss < 1 W. PACS 42.55.-f; 42.55.Xi; 42.60.Pk     

Simultaneous dual-wavelength operation at 1.06 and 1.34 μm in Nd-vanadate laser crystals

Output performances of Nd-vanadate lasers with simultaneous dual-wavelength emission on the 1.06-μm ⁴ F _3/2 → ⁴ I _11/2 transition and the ⁴ F _3/2 → ⁴ I _13/2 transition at 1.34 μm are discussed. The design uses a linear resonator for emission at 1.06 μm and an L-type folded resonator for the 1.34-μm wavelength, and the ratio between the power of a single wavelength and the total power is adjusted by the choice of the output mirror transmissions. A continuous-wave (CW) Nd:GdVO₄ laser with total output power in the range of 3.9 to 6.8 W and the corresponding ratio of the output power at 1.06 μm to the total output power between 0.26 and 0.97 is realized. It is also shown that in comparison with the pump at 808 nm, the pump directly into the ⁴ F _3/2 emitting level at 879 nm improves the total output power. Furthermore, a Nd:GdVO₄ laser with simultaneous emission at 1.06 and 1.34 μm and that generates also green light at 0.53 μm by intracavity frequency-doubling with LiB₃O₅ (LBO) nonlinear crystal is demonstrated.     

Diode-pumped quasi-three-level Nd:CLNGG laser at 928 nm

We describe the output performances of the 928 nm ⁴ F _3/2 → ⁴ I _9/2 transition in Nd:CLNGG under diode-laser pumping. An end-pumped Nd:CLNGG crystal yielded 1.3 W of continuous-wave output power for 17.8 W of absorbed pump power. The slope efficiency with respect to the absorbed pump power was 11.2%. Furthermore, with 17.8 W of diode pump power and the frequency-doubling crystal LiB₃O₅ (LBO), a maximum output power of 260 mW in the blue spectral range at 464 nm has been achieved. The blue output power stability over 4 h is better than 3.2%.     

Generation regimes of a pulsed Nd:YAG laser with transverse LED pumping and multiloop self-pumped phase-conjugate cavity

The generation regimes in a pulsed Nd:YAG laser with transverse LED pumping and multiloop self-pumped phase-conjugate cavity on the gain gratings are studied. The differential efficiency of laser is 27% in the free-running regime at a pulse energy of up to 1 J and quality parameter M ² of no greater than 1.5. The pulse energy under passive Q-switching is no less than 60% of the pulse energy in the free-running regime at the same beam quality. The generation of the narrow-band radiation is demonstrated. A generation band of no greater than 1.2 GHz corresponds to the primary single-frequency high-power laser pulse in the free-running mode under conditions for self-Q-switching on the gain gratings. When additional elements (F ₂ ^? :LiF and Cr⁴⁺:YAG crystals) are introduced in the optical scheme of the phase-conjugate cavity, similar narrowband single-mode generation is observed in the passive Q-switching regime as a pulse train or monopulse. The laser pulse power is up to 2 MW at a pulse duration of 20 ns.