Operation Of Nd Research Articles

Continuous wave laser operation in Nd:GGG depressed tubular cladding waveguides produced by inscription of femtosecond laser pulses

Depressed tubular cladding waveguides have been produced in Nd:GGG crystals by using multiple inscription with femtosecond (fs) laser pulses. The guiding cores are located inside the tubular regions with cross-section diameters of 90-150 μm, which are surrounded by fs-laser induced low-refractive-index tracks. At room temperature continuous wave (cw) laser oscillations at wavelength of ~1063 nm have been realized through the optical pump at 808 nm. The slope efficiency of the cladding waveguide lasers is as high as 44.4% and the maximum output power at 1063 nm is 209 mW, which shows superior laser performance to the Type II stress induced Nd:GGG waveguides.

Improvement of laser characteristics for diode-pumped passively Q-switched and mode-locked Nd:Lu0.15Y0.85VO4 laser by AO modulator

The hybrid Q-switched and mode-locked (QML) operation of Nd:Lu0.15Y0.85VO4 crystal at 1.34 μm with V:YAG saturable absorber and acousto-optic (AO) modulator has been realized. The laser characteristics are distinctly improved by the hybrid QML if compared to those with the single V:YAG QML. At the pump power of 5.04 W, the Q-switched pulse energy is enlarged to 5.6 times and the Q-switched pulse width is shortened to 40% by the AO modulator in contrast to those of the single passively QML.

Simultaneous dual-wavelength operation of Nd:YVO_4 self-Raman laser at 1524 nm and undoped GdVO_4 Raman laser at 1522 nm

A diode-pumped, actively Q-switched dual-wavelength laser employing Nd:YVO(4) self-Raman emission at 1524 nm and undoped GdVO(4) Raman emission at 1522 nm is demonstrated. With a pump power of 21.5 W and pulse repetition frequency of 20 kHz, a maximum dual-wavelength output power of 1.62 W was obtained, comprising a 0.54 W, 1522 nm Raman component and 1.08 W, 1524 nm self-Raman component. The corresponding dual-wavelength Raman pulse width was 5.6 ns. The experimental results indicate that this laser, with quite small wavelength separation, was effective by virtue of simultaneous self-Raman and Raman shifts.

Note: Self Q-switched Nd:YVO4 laser at 914 nm

By exploiting the saturable nature of re-absorption loss under the quasi-three-level laser transition self Q-switching operation in Nd:YVO(4) laser at 914 nm is demonstrated. The stable self-pulsing operation was observed with Nd:YVO(4) crystal with doping concentration of 0.3 at.%. At an incident pump power of 30 W around 600 mW of average power was obtained. Individual pulse energy and FWHM pulse duration were experimentally measured to be 10 μJ and 460 ns, respectively. The performance of the laser was analyzed with the help of a rate equation model. The simulation results show good agreement with the experiment.

Diode-pumped Q-switched and mode-locked Nd:Gd 0.3Lu 0.33Y 0.37VO 4 laser with EO modulator and single-walled carbon nanotube

By using both the single-walled carbon nanotube saturable absorber (SWCNT-SA) and the electro-optic (EO) modulator, the stably doubly Q-switched and mode-locked (QML) operation of Nd:Gd 0.3Lu 0.33Y 0.37VO 4 laser has been demonstrated. The QML laser characteristics such as the pulse width, single-pulse energy, etc., have been measured for different modulation frequencies of the EO modulator ( f e ) and reflectivity ( R) of output coupler. In comparison with the solely passively QML laser with SWCNT-SA, the experimental results show that the doubly QML laser can generate more stable and shorter pulses with higher pulse energy. At 9.24 W pump power, f e =1 kHz and R=93.5%, the doubly QML laser has compressed the Q-switched envelope pulse width 88% and improved the mode-locked pulsed energy 55 times.

Crystal growth, spectral and laser properties of Nd:LSAT single crystal

Nd:(La, Sr)(Al, Ta)O3 (Nd:LSAT) crystal was grown by the Czochralski method. The absorption and fluorescence spectra of Nd:LSAT crystal at room temperature were investigated. With a fiber-coupled diode laser as pump source, the continuous-wave (CW) laser action of Nd:LSAT crystal was demonstrated. The result of diode-pumped laser operation of Nd:LSAT crystal single crystal is reported for what is to our knowledge the first time. The maximum output power at 1064 nm was obtained to be 165 mW under the incident pump power of 3 W, with the slope efficiency 10.9%.

Diode-pumped continuous wave and Q-switched operation of Nd:LuAG crystal

The continuous wave (CW) and passively Q-switched performances of Nd:LuAG crystal were demonstrated. With a laser diode as pump source, the CW output power of 2.18 W was obtained under the pump power of 4.62 W, corresponding to the optical conversion efficiency of 47.2% and the slope efficiency of 52.2%. For Q-switching experiments, the shortest pulse width, largest pulse energy, and highest peak power were measured to be 12 ns, 50.6 μJ, and 4.21 kW, respectively.

Continuous-wave and passively Q-switched Nd:LYSO lasers

Continuous-wave (CW) and passively Q-switched performance of a Nd-doped oyorthosilicate mixing crystal, (Nd0.005Lu0.4975Y0.4975)2SiO5 (Nd:LYSO), were reported. As a result, new dual-wavelength all-solid-state lasers at 1075 and 1079 nm were achieved. When the absorbed pump power was 3.87 W, the CW laser produced 1.1 W output, corresponding to an optical conversion efficiency of 28.4% and a slope efficiency of 32.4%. By using a Cr4+:YAG wafer as the saturable absorber, we achieved Q-switching operation of Nd:LYSO crystal. The maximal average output power, shortest pulse width, largest pulse energy and highest peak power were measured to be 294 mW, 27.5 ns, 34.3 μJ and 1.18 kW, respectively. By difference frequency, these dual-wavelength lasers have potential applications for the generation of a broadband coherent radiation from 0.7–1.3 THz.

Efficient dual-wavelength operation of Nd:LYSO laser by diode pumping aimed toward the absorption peak

By aiming the pump wavelength of the laser diode to the absorption peak at 811 nm of the (Nd0:005Lu0:4975Y0:4975)2SiO5 (Nd:LYSO) crystal, an efficient dual-wavelength operation at 1,075 and 1,079 nm is obtained. The maximum output power is 702 mW when the incident pump power is 2.53 W, corresponding to an optical conversion efficiency of 27.7% and a slope efficiency of 37.0%.

Passive Q-switching performance of intracavity frequency-doubled red laser with mixed Nd:GdxY1−xVO4 crystals

Passive Q-switching laser operation of Nd:GdxY1−xVO4 mixed crystals at 671nm has been compared in the same V-shape folded cavity. Based on our comparative analysis, the best laser characteristics – the highest pulse energy and peak power and the shortest pulse width – were demonstrated by Nd:Gd0.63Y0.37VO4 crystal. At the same time, this crystal possesses the lowest thermal conductivity in comparison with the other Nd:GdxY1−xVO4 crystals, which could result in decreasing the average laser output power. To verify this assumption we also measured the focal lengths of thermal lens induced in the crystals during the laser operation.

Quasi-three-level laser operation of Nd:Y0.53Gd0.47VO4 mixed vanadate crystal oscillating at 913 nm

Efficient continuous-wave (CW) laser operation on the 4 F 3/2 → 4 I 9/2 transition of Nd:Y0.53Gd0.47VO4, a mixed vanadate crystal, is demonstrated at room temperature employing a compact plano-concave resonator, generating a polarized output power of 0.39 W at 913.2 nm with 2.85 W of pump power absorbed, the optical-to-optical and slope efficiencies being 14 and 25%, respectively.

Diode-pumped continuous wave and Q-switched operation of Nd:CaYAlO_4 crystal

The continuous wave (CW) and passively Q-switched performances of Nd:CaYAlO(4) crystal with both a- and c-cut were demonstrated. The CW output powers of 1.15 W and 1.26 W were obtained under the pump power of 8.96 W with slope efficiencies of 15.2% and 16.8% for a- and c-cut samples, respectively. As a result, new dual-wavelength all-solid-state lasers at 1080 nm and 1081 nm were achieved with c-cut crystal. By using Cr(4+):YAG wafer as saturable absorber, we performed Q-switching experiments. The highest average output powers and shortest pulse widths were measured to be 0.798 W, 10.6 ns and 0.537 W, 9.6 ns for a- and c-cut samples, respectively.

Continuous-wave and Q-switched laser operation of Nd:Gd 0.18Y 0.82VO 4 mixed crystal

Efficient continuous-wave (cw), passively Q-switched, and actively Q-switched laser operations are demonstrated with a mixed vanadate crystal of Nd:Gd 0.18Y 0.82VO 4 under diode pumping. In a cw operation, an output power of 8.25 W is obtained at a maximum available incident pump power ( P in) of 15 W, with a slope efficiency of 56%. Using a Cr 4+:YAG crystal of initial transmission of 62% as the saturable absorber for Q-switching, an average output power of 3.05 W is generated at pulse repetition frequency (PRF) of 16.7 kHz when the laser is pumped with the same maximum P in. The pulse energy, pulse duration, and peak power are 183.3 μJ, 6.0 ns, and 30.6 kW, respectively. When actively Q-switched by an acousto-optic modulator, the laser produces an average output power of 5.5 W at PRF of 30 kHz with 16.2 W of pump power incident upon the laser crystal. The pulse energy, duration, and peak power are measured to be 183 μJ, 10.5 ns, and 17.5 kW, respectively.

Polarized spectral properties and laser operation of Nd^3+-doped La_2(WO_4)_3 crystal

A Nd3+:La2(WO4)3 single crystal was grown by the Czochralski method. The orientation relationship between the optical indicatrix axes and the crystallographic axes was determined. Polarized spectral properties were studied in detail. Laser oscillations of this crystal under Ti:sapphire laser pumping at 802 nm were demonstrated. The achieved highest slope efficiencies were 51.3% and 12.1% for 1058 and 1332 nm, respectively, and the corresponding thresholds were 30 and 93 mW, respectively.

Ultraviolet emission excitation in RE 3+ activated fluoride fibers

Short-wavelength (∼280–410 nm) fluorescence in Er 3+, Tm 3+, Nd 3+ and Ho 3+ doped ZBLAN glasses was studied experimentally and attributed to transitions from the 2P 3/2, 1I 6 and 1D 2, 4D 3/2, 3D 3 states, respectively. Properties of these high-lying metastable levels, such as state energies, transition wavelengths, lifetimes, emission branching ratios and cross-sections, which are important for laser action analysis, were determined. In particular, up-conversion UV emission excitation schemes for Nd 3+ and Ho 3+ doped ZBLAN were studied experimentally and modeled by time dependent rate equations. Violet and ultraviolet laser operation in Nd 3+ and Ho 3+ doped ZBLAN fibers under up-conversion pumping was studied theoretically basing on measured spectroscopic parameters.

Continuous-wave, intracavity doubled, self-Raman laser operation in Nd:GdVO_4 at 586.5 nm

We report a continuous-wave self-Raman laser based on diode-pumped Nd:GdVO(4) giving first-Stokes output at 1173 nm and intracavity frequency-doubled output at 586.5 nm. A maximum cw output power at 1173 nm of 2 W was obtained for diode pump powers of 22 W and a maximum cw power at 586 nm of 678 mW with 16.3 W pump power. Infrared and yellow powers were limited by thermal lensing in the gain medium and parasitic oscillations of weak Nd(3+) transitions. Quasi-cw operation at 50% duty-cycle reduced the thermal load in the laser/Raman crystal, allowing cavity stability to be obtained near maximum available pump power (25.7 W) for which the maximum quasi-cw yellow output power was 1.88 W.

Temperature-independent lasers using output couplers with temperature-dependent reflectivity

The temperature dependence of the reflectivity of volume Bragg grating mirrors is shown to determine the performance of a solid-state laser. Mirrors with reflectivities that vary with temperature are then considered that make the temperature-independent operation of Nd:YAG (and other) lasers possible.

Passively Q-switched laser operation of Nd:LaB3O6 cleavage microchip

Pumped by a Ti:sapphire laser, a passively Q-switched laser oscillation from an unprocessed Nd:LaB3O6 cleavage microchip with a Cr4+:YAG saturable absorber has been demonstrated. The influence of the transmission of the output coupler on the pulse width and repetition rate at various absorbed pump powers has been investigated. A pulse with 2.8μJ energy, 2.2ns duration, and 29kHz repetition rate at 1060nm was obtained at the absorbed pump power of 1.25W and output coupler transmission of 3.2%, which results in 1.25kW peak power. The polarization and spectral properties of laser radiation were measured.

Visible Micro Solid-State Lasers

We review the recent trends of visible light sources based on nonlinear frequency conversion from the Nd3+-doped micro-lasers. In order to evaluate the emission properties of 1.3, 1.0, and 0.9 in Nd3+-ion doped materials, the spectroscopic parameters were summarized. Recently appeared Nd: GdV4O has the large absorption and emission cross-sections with high thermal conductivity, as high as YAG. After the demonstration of near quantum limit highly efficient operation in Nd: GdVO4, the intra-cavity frequency doubled micro-laser was reviewed as a high power compact green laser. On the other hand, we have demonstrated the high power stable green and deep blue laser under extra-cavity frequency doubling with periodically-poled MgO: LiNbO3 (PPMgLN) for quasi-phase matched second harmonic generation (QPM-SHG). Finally, edge pumped Yb: YAG microchip laser was discussed for the high-power visible microchip lasers.

Nd:YAG microdisk laser generating in the fundamental mode

Systematic numerical studies of the non-linear operation of Nd:YAG microdisk laser are presented. An approximate formula is relating small signal gain to the output power and the characteristic parameters of the structure, taking into account gain saturation effect. Output power characteristics revealing a saturation effect are discussed. Presented formulas and characteristics can be used for designing the optimal structure providing maximum output power.