Spectroscopic characteristics of Pr<Superscript>3+</Superscript> in biaxial La<Subscript>2</Subscript>(WO<Subscript>4</Subscript>)<Subscript>3</Subscript> crystal

A Pr³⁺-doped La₂(WO₄)₃ crystal grown by the Czochralski method has been investigated as a promising laser material. The principal axes of the optical indicatrix and Pr³⁺ concentration of the crystal were determined. The polarized absorption, fluorescence spectra and fluorescence decay curves of the main emission multiplets of the crystal were measured at room temperature. The spectroscopic parameters were obtained by the modified Judd–Ofelt theory combined with the normalized method. The peak stimulated emission cross-sections of the major emission lines were estimated. The good spectroscopic properties imply that the Pr³⁺:La₂(WO₄)₃ crystal is a potential laser gain medium for solid-state laser and self-stimulated Raman laser applications. PACS 78.20.-e; 42.70.Hj     

Diode-pumped Nd:LuVO<Subscript>4</Subscript>-Nd:YVO<Subscript>4</Subscript> laser at 492 nm with intracavity sum-frequency-mixing in LiB<Subscript>3</Subscript>O<Subscript>6</Subscript>

We present for the first time a Nd:YVO₄ laser emitting at 1064 nm intracavity pumped by a 916 nm diode-pumped Nd:LuVO₄ laser. A 809 nm laser diode is used to pump the Nd:LuVO₄ crystal emitting at 916 nm, a Nd:YVO₄ laser crystal was pumped at 916 nm and lased at 1064 nm. Intracavity sum-frequency mixing at 916 and 1064 nm was then realized in a LiB₃O₆ (LBO) crystal to reach the blue range. We obtained a continuous-wave output power of 216 mW at 492 nm under 19.6 W of incident pump power at 809 nm.     

Efficient blue emission of ytterbium-doped Sr<Subscript>5</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript>F under quasi-three-level intracavity pumping

We report an Yb:Sr₅(PO₄)₃F (Yb:S-FAP) laser emitting at 985 nm intracavity pumped by a 912 nm diode-pumped Nd:GdVO₄ laser. A 808 nm diode laser is used to pump the Nd:GdVO₄ crystal emitting at 912 nm, and the Yb:S-FAP laser emitting at 985 nm intracavity pumped at 912 nm. With incident pump power of 17.5 W, intracavity second harmonic generation has been demonstrated with a power of 131 mW at 492.5 nm by using a LBO nonlinear crystal.     

Crystal growth,spectroscopic and CW laser properties of Nd<Subscript>0.03</Subscript>Lu<Subscript>2.871</Subscript>Gd<Subscript>0.099</Subscript>Al<Subscript>5</Subscript>O<Subscript>12</Subscript> crystal

Nd_0.03Lu_2.871Gd_0.099Al₅O₁₂ (Nd:LuGdAG) crystal was grown by the Czochralski method. The absorption, fluorescence spectra and fluorescence lifetime of Nd:LuGdAG crystal at room temperature were investigated for the first time. We reported the continuous-wave (CW) Nd:LuGdAG laser operation under diode pumping. Output power of 1.43 W at 1064 nm was achieved with a slope efficiency of 34.1%. All the results show that Nd:LuGdAG crystal is a promising laser material.     

Passively Q-switched laser performance of a diode-pump mixed Nd:Lu<Subscript>0.15</Subscript>Y<Subscript>0.85</Subscript>VO<Subscript>4</Subscript> crystal

A diode-pumped passively Q-switched Nd:Lu_0.15Y_0.85VO₄ laser with a GaAs output coupler is demonstrated. By using a mixed crystal Nd:Lu_0.15Y_0.85VO₄ as laser medium, the passively Q-switched laser can generate shorter pulse width with higher peak power in comparison with the passively Q-switched Nd:LuVO₄ or Nd:YVO₄ lasers under the same laser cavity. At the incident pump power 11.9 W, the minimum pulse width of 3.23 ns and the maximum peak power 1.67 kW can be obtained. The average output power and the pulse repetition rate of the laser are also measured. The experimental results show that the mixed crystal is a promising laser medium for shorter Q-switched pulse with higher peak power.     

All-solid-state intracavity frequency-doubled Nd:Y<Subscript>0.36</Subscript>Gd<Subscript>0.64</Subscript>VO<Subscript>4</Subscript>-GdCa<Subscript>4</Subscript>O(BO<Subscript>3</Subscript>)<Subscript>3</Subscript> green laser under direct 880 nm pumping

We report a green laser at 532 nm generation by intracavity frequency doubling of a continuous wave (CW) laser operation of a 1064 nm Nd:Y_0.36Gd_0.64VO₄ laser under in-band diode pumping at 880 nm. An GdCa₄O(BO₃)₃ (GdCOB) crystal, cut for critical type I phase matching at room temperature is used for second harmonic generation of the laser. At an incident pump power of 17.8 W, as high as 2.92 W of CW output power at 532 nm is achieved. The optical-to-optical conversion efficiency is up to 16.4%, and the fluctuation of the green output power was better than 2.5% in the given 30 min.     

Radiation Resistance of Yb:LaSc<Subscript>3</Subscript>(BO<Subscript>3</Subscript>)<Subscript>4</Subscript> and Yb:LuYSiO<Subscript>5</Subscript> Laser Crystals

The optical transmission (OT) spectra of Yb:LaSc₃(BO₃)₄ and Yb:LuYSiO₅ laser crystals have been analyzed before and after irradiation from a ⁶⁰Co source with doses up to 45 Mrad. The OT spectra of the Yb:LuYSiO₅ crystal are found to be the same (within the measurement error) before and after irradiation. The irradiation of the 10 at.%Yb:LaSc₃(BO₃)₄ crystal significantly changes its OT spectra in a wide spectral range (330 to 700 nm). A 975-nm laser based on a previously irradiated 4 at.%Yb:LuYSiO₅ crystal has exhibited a differential efficiency of 23% under diode pumping. The up-conversion luminescence spectra in the visible range of the crystals under study have been explained.     

Passive mode-locking Yb<Subscript>3+</Subscript>:Sc<Subscript>2</Subscript>SiO<Subscript>5</Subscript> laser at 1040 nm with SESAM

Passive mode locking of the new crystal Yb₃₊:Sc₂SiO₅ (Yb:SSO) laser at 1040 nm in a w-type cavity is reported for the first time to our knowledge. The laser operated at a repetition frequency of 94 MHz. A pulse duration of 4.2 ps was produced with an average power of 543 mW and a highest pulse energy of 5.7 nJ, corresponding it’s maximum peak power can reach to 1.4 kW.     

CW Nd:LuVO<Subscript>4</Subscript>-GdCa<Subscript>4</Subscript>O(BO<Subscript>3</Subscript>)<Subscript>3</Subscript> red laser under direct 888 nm pumping

We report a red laser at 672 nm generation by intracavity frequency doubling of a continuous wave (CW) laser operation of a 1343 nm Nd:LuVO₄ laser under in-band diode pumping at 888 nm. An GdCa₄O(BO₃)₃ (GdCOB) crystal, cut for critical type I phase matching at room temperature is used for second harmonic generation of the laser. At an incident pump power of 17.8 W, as high as 1.73 W of CW output power at 672 nm is achieved. The optical-to-optical conversion efficiency is up to 9.7%, and the fluctuation of the red output power was better than 3.3% in the given 30 min.     

Efficient Nd:Y<Subscript>0.36</Subscript>Gd<Subscript>0.64</Subscript>VO<Subscript>4</Subscript>-GdCa<Subscript>4</Subscript>O(BO<Subscript>3</Subscript>)<Subscript>3</Subscript> red laser under diode pumping into the emitting level

We report a red laser at 671 nm generation by intracavity frequency doubling of a continuous wave (cw) laser operation of a 1342 nm Nd:Y_0.36Gd_0.64VO₄ laser under diode pumping into the emitting level ⁴ F _3/2. An GdCa₄O(BO₃)₃ (GdCOB) crystal, cut for critical type I phase matching at room temperature is used for second harmonic generation of the laser. At an incident pump power of 17.8 W, as high as 1.12 W of cw output power at 671 nm is achieved. The optical-to-optical conversion efficiency is up to 6.3%, and the fluctuation of the red output power was better than 3.5% in the given 30 min.     

Performance comparisons of passively Q-switched intracavity-frequency-doubled Nd:Gd<Subscript>0.19</Subscript>Y<Subscript>0.81</Subscript>VO<Subscript>4</Subscript> and Nd:Gd<Subscript>0.83</Subscript>Y<Subscript>0.17</Subscript>VO<Subscript>4</Subscript> lasers at 671 nm

Performance comparisons of laser-diode pumped passively Q-switched intracavity-frequency-doubled Nd:Gd_0.19Y_0.81VO₄ and Nd:Gd_0.83Y_0.17VO₄ lasers at 671 nm are demonstrated for the first time to our knowledge. KTP crystal is used as the frequency doubling material and V:YAG crystal as the saturable absorber with initial transmission of 89%. The dependences of average output power, pulse width, pulse repetition rate, single-pulse energy and peak power on incident pump power are measured and contrasted. The experimental results show that, Nd:Gd_0.83Y_0.17VO₄ laser has more excellent properties than Nd:Gd_0.19Y_0.81VO₄ laser at 671 nm.     

Diode-pumped passively mode-locked Nd:CaNb<Subscript>2</Subscript>O<Subscript>6</Subscript> laser

We have experimentally demonstrated a diode-pumped passively mode-locked Nd:CaNb₂O₆ laser for the first time to our best knowledge. With a semiconductor saturable absorber mirror (SESAM) as a passive mode locker, the laser generated stable mode-locked pulses with pulse duration of 17.3 ps and repetition rate of 88.4 MHz. With a singe-emitter laser diode pumping, the maximum average output power of the mode-locked laser was 0.843 W, with a slope efficiency of 23%. The experimental results show the Nd:CaNb₂O₆ crystal is a promising laser gain medium for picosecond pulse generation.     

Experimental study on doubly QML Nd:Lu<Subscript>0.15</Subscript>Y<Subscript>0.85</Subscript>VO<Subscript>4</Subscript> laser with AO modulator and central SESAM

By using double-mixed crystal Nd:Lu_0.15Y_0.85VO₄ as laser medium, a diode-pumped doubly Q-switched and mode-locked (QML) Nd:Lu_0.15Y_0.85VO₄ laser with acousto-optic (AO) modulator and central semiconductor saturable absorption mirror (SESAM) is realized for the first time. The Q-switched envelope modulation depth is nearly 100%.The average output power and the pulse width of the Q-switched envelope etc. for different AO modulator repetition rates have been measured. The experimental result show that Nd:Lu_0.15Y_0.85VO₄ crystal is an excellent laser medium for doubly QML lasers.     

All-solid-state CW intracavity frequency-doubling Nd:Lu<Subscript>2</Subscript>O<Subscript>3</Subscript>/LBO red laser at 679.5 nm

We report an efficient intracavity second-harmonic generation (SHG) at 1359 nm in a non-linear optical crystal, LiB₃O₅ (LBO), performed with a diode end pumped continuous-wave (cw) Nd:Lu₂O₃ laser. In the case of a laser with a Nd:Lu₂O₃ crystal frequency-doubled with a LBO crystal cut for type I frequency doubling. A cw SHG output power of 462 mW has been obtained using a 10 mm long LBO crystal. The red power stability was 3.4% in 4 h.     

Lasing from a solid-state Ca<Subscript>3</Subscript>Ga<Subscript>2</Subscript>Ge<Subscript>3</Subscript>O<Subscript>12</Subscript>:Nd<Superscript>3+</Superscript> laser at a high power of diode pumping

Experimental data for cw lasing from a compact solid-state laser based on a neodymium-doped calcium-gallium-germanium-garnet crystal (Ca₃Ga₂Ge₃O₁₂:Nd³⁺) at a wavelength of 1.06 μm in the case of intense diode pumping are reported. The laser output reaches 0.7 W for a cavity 15 mm long and an active element 1 mm thick. It is shown that the output power is limited by a thermal lens placed in the active element.     

Sub-90 fs pulses from a passively mode-locked Yb:YAl<Subscript>3</Subscript>(BO<Subscript>3</Subscript>)<Subscript>4</Subscript> laser

Passive mode locking of the self-frequency doubling Yb:YAB crystal with a saturable absorber mirror is studied at the fundamental wavelength. This laser has a very low threshold, and pulses as short as 85 and 87 fs are obtained for Ti:sapphire and diode laser pumping, respectively.     

Diode-pumped passively Q-switched and mode-locked Nd:Lu<Subscript>0.15</Subscript>Y<Subscript>0.85</Subscript>VO<Subscript>4</Subscript> laser with a GaAs saturable absorber

By using a-cut Nd:Lu_0.15Y_0.85VO₄ mixed crystal as laser gain medium, a diode-pumped passively Q-switched and mode-locked (QML) laser with a GaAs saturable absorber in a Z-type folded cavity is demonstrated for the first time. The Q-switched mode-locked laser pulses with about 90% modulation depth are obtained as long as the pump power reached the oscillation threshold. The repetition rate of the passively Q-switched pulse envelope ranges from 50 to 186 kHz as the pump power increases from 0.915 to 6.520 W. Under an incident pump power of 6.52 W, the QML pulses with the largest average output power of 694 mW, the shortest pulse width of 200 ns and the highest pulse energy of 3.73 μJ are obtained. The mode-locked pulse width inside the Q-switched envelope is estimated to be about 275 ps. The experimental results show that Nd:Lu_0.15Y_0.85VO₄ is a promising mixed crystal for QML laser.     

Diode pumped Nd:Lu<Subscript>0.5</Subscript>Y<Subscript>0.5</Subscript>VO<Subscript>4</Subscript>-LBO red laser at 671 nm

We report a efficient compact red laser at 671 nm generation by intracavity frequency doubling of a continuous wave laser operation of a diode pumped Nd:Lu_0.5Y_0.5VO₄ laser on the ⁴ F _3/2-⁴ I _13/2 transition at 1342 nm. An LBO crystal, cut for critical type I phase matching at room temperature is used for second harmonic generation of the laser. At an absorbed pump power of 17.8 W, as high as 2.25 W of continuous wave output power at 671 nm is achieved with 10-mm-long LBO. The optical-to-optical conversion efficiency is up to 12.6%, and the fluctuation of the red output power was better than 3.6% in the given 30 min.     

A novel prism beam-shaping laser diode bar end-pumped TEM<Subscript>00</Subscript> mode Nd:YVO<Subscript>4</Subscript> laser

A beam-shaping diode end-pumped TEM₀₀ mode CW Nd:YVO₄ laser is presented. A special beam-shaping element made up of isosceles right-angled prism pieces is adopted to realize beam symmetric. Two cylinder lenses are used to couple the shaped beam into a 3 × 3 × 9 mm Nd:YVO₄ crystal with 0.3 at % neodymium doping. By using this laser system, we have achieved 6.1 W CW laser operated in single transverse mode at 1064 nm with 95.2% reshaping efficiency and 25.6% optical-optical conversion efficiency.     

Study of LD pumped Q-switched Nd:Y<Subscript>0.5</Subscript>Lu<Subscript>0.5</Subscript>VO<Subscript>4</Subscript> laser with acousto-optic modulator

A laser-diode (LD) pumped Q-switched Nd:Y_0.5Lu_0.5VO₄ crystal laser with an acousto-optic (AO) modulator is presented in this paper. The maximum continuous wave (CW) output power of 5.53 W is achieved at the incident pump power of 14.09 W with the transmission of 10% for the output coupler, resulting in an optical-to-optical conversion efficiency of 39.2%. For Q-switching operation, the shortest pulse width of 8.3 ns and the highest peak power of 259 kW are generated under the incident pump power of 14.09 W at 1 kHz.