Efficient continuous-wave YVO<Subscript>4</Subscript>/Nd:YVO<Subscript>4</Subscript> Raman laser at 1176 nm

We present a simple and compact continuous-wave (CW) 1176 nm laser based on self-frequency Raman conversion in continuous-grown YVO₄/Nd:YVO₄ composite crystal. With a composite crystal 30 mm in length, a maximum output power up to 1.84 W was achieved at the incident diode pump power of 23.6 W. Corresponding to overall optical conversion, the efficiency was 7.8% and the slope efficiency was 8.5%. The conversion efficiency has been doubled compared with the conventional Nd:YVO₄ CW self-frequency Raman laser. The excellent performance of this laser shows that the long continuous-grown YVO₄/Nd:YVO₄ composite crystal is promising in the application of CW Raman lasers and ideal for miniaturization.     

Continuous-wave intracavity Raman laser at 1179.5 nm with SrWO<Subscript>4</Subscript> Raman crystal in diode-end-pumped Nd:YVO<Subscript>4</Subscript> laser

We report a continuous-wave intracavity Raman laser at 1179.5 nm with a SrWO₄ Raman crystal in a diode-end-pumped Nd:YVO₄ laser. The highest output power of 2.23 W is obtained at the laser diode power of 21.2 W corresponding to the slope efficiency of 17.3% and a diode-to-stokes optical conversion efficiency of 10.5%. The dependence of the Raman laser performance on the pump polarization is also studied. The measured Raman thresholds are about 9.3 and 8.3 W in the diode pump laser power for the a- and b-polarized configurations, respectively. The Raman gain coefficients of the c-cut SrWO₄ crystal for a- and b-polarized pumps are estimated to be about 4.9 and 4.7 cm/GW, respectively.     

Continuous-wave laser oscillation at 1.06 µm in silicon ion-implanted Nd:YVO<Subscript>4</Subscript> planar waveguide

This work, for the first time to our knowledge, reports continuous-wave laser oscillation at 1.06 μm in Nd:YVO₄ planar waveguide formed by 3.0 MeV Si⁺ ion implantation at a dose of 1 × 10¹⁵ ions/cm² at room temperature. The effective refractive indices of the waveguide propagation modes were measured by using a prism-coupling method after the annealing at 240°C for 60 min in air. The performance of the waveguide laser has been studied in terms of the threshold pump power and slope efficiency. The laser outputs show a very high stability operating in cw regime at room temperature.     

Pulse characteristics of passively Q-switched 1.34 μm Nd:GdVO<Subscript>4</Subscript>/Co<Superscript>2+</Superscript>:MgAl<Subscript>2</Subscript>O<Subscript>4</Subscript> laser

Passively Q-switched output of a diode-pumped 1.34 μm Nd:GdVO₄ laser was demonstrated by using Co²⁺:MgAl₂O₄(Co²⁺:MALO) crystal as the saturable absorber for the first time. When the transmission of output mirror is 15%, the Q-switched pulse width is 110 ns and a corresponding average output power is 460 mW under the pump power of 9.69 W. The optical-optical conversion efficiency is 36%. At about 330 kHz repetition rate, the single Q-switched pulse energy and the peak power are about 1.39 μJ and 12.6 W, respectively.     

Passively Q-switched laser performance of Nd:Lu<Subscript>0.15</Subscript>Y<Subscript>0.85</Subscript>VO<Subscript>4</Subscript> operating at 1.34 μm with a V:YAG saturable absorber

A diode-pumped passively Q-switched Nd:Lu_0.15Y_0.85VO₄ crystal laser at 1.34 μm with V:YAG employed as the saturable absorber was demonstrated for the first time to our best knowledge. The maximum average output power of 0.529 W was achieved under the pump power of 5.6 W, corresponding to an opticaloptical conversion efficiency of over 9.4% and slope efficiency of over 16%. The pulse width was shortened to 85.6 ns, corresponding to the maximum pulse repetition rate of 250 kHz. The largest single pulse energy and peak power were 5.57 μJ and 58.74 W, respectively.     

A comprehensive study of Nd:YAG,Nd:YAlO<Subscript>3</Subscript>, Nd:YVO<Subscript>4</Subscript> and Nd:YGdVO<Subscript>4</Subscript> lasers operating at wavelengths of 0.9 and 1.3 μm. Part 2: passively mode locked-operation

This paper reports on the generation of picosecond (ps) laser pulses by self-phase-adjusting additive-pulse-mode-locking (PSA) at wavelengths of 0.9 and 1.3 μm. The main objective of this work was to investigate and compare the characteristic optical properties of ps lasers based on different Nd-doped laser crystals like Nd:YAG, Nd:YAlO₃, Nd:YVO₄ and Nd:GdVO₄. As a result of these investigations a mode-locked Nd:YVO₄ laser for example, generated, ps pulses at 1.3 μm with a duration of 7 ps, a repetition rate of 160 MHz and an average power of 4.7 W. At 0.9 μm pulses with a duration of 1.9 ps were obtained at a repetition rate of 158 MHz and an average power of 2.8 W. PACS  42.70.Hj; 42.65.Re; 42.65.Ky     

Double-loss-modulated q-switched and mode-locked Nd:Lu<Subscript>0.15</Subscript>Y<Subscript>0.85</Subscript>VO<Subscript>4</Subscript> laser at 1.34 μm with single-walled carbon nanotube saturable absorber and AO modulator

A diode-pumped dual-loss-modulated Q-switched and mode-locked (QML) Nd:Lu_0.15Y_0.85VO₄ laser at 1.34 μm with single-walled carbon nanotube saturable absorber (SWCNT-SA) and acousto-optic (AO) modulator is demonstrated. The modulation depth of the dual-loss-modulated QML laser reaches 90%, being deeper than 75% that obtained by the single passively QML laser. The stability of the hybrid QML laser is significantly improved if compared to that only with SWCNT-SA. The Q-switched pulse energy and the Q-switched pulse width of the QML laser with the dual-loss-modulation are 487 and 27% of those only with SWCNT-SA, respectively.     

Diode-pumped Nd:YVO<Subscript>4</Subscript> and Nd:KGd(WO<Subscript>4</Subscript>)<Subscript>2</Subscript> 1.3 μm lasers passively Q-switched with PbS-doped glass

Diode-pumped Nd:YVO₄ and Nd:KGW lasers passively Q-switched with PbS-quantum dot-doped phosphate glass were demonstrated. For the Nd:YVO₄ laser, pulses 110 ns in duration with a 13% Q-switching efficiency were obtained. The absorption recovery time of the PbS-doped glass was measured to be 27±4 ps. Some recommendations for more efficient use of PbS-doped glasses for Q-switching of diode-pumped lasers are suggested on the basis of our analysis. Received: 29 July 2002 / Revised version: 18 September 2002 / Published online: 12 February 2003 RID="*" ID="*"Corresponding author. Fax: +375-17/232-6286, E-mail: savitski@eudoramail.com     

Experiment and modeling of a diode-pumped 1.3 μm Nd:YVO<Subscript>4</Subscript> laser passively Q-switched with PbS-doped glass

A diode-pumped 1.34 m Nd:YVO₄ laser passively Q-switched with PbS quantum dots doped glass is presented. An average output power of 24 mW with a Q-switching efficiency of 13% and a Q-switched pulse width of 15 ns was obtained. A four level spectroscopic model of a PbS quantum dots doped glass saturable absorber is applied to numerically simulate passively Q-switched Nd:YVO₄ laser operation. It has been shown that for the simulation of passive Q-switching of 1.3 m Nd:YVO₄ lasers with PbS doped glasses as the saturable absorbers, it is necessary to take into account intensity dependence of bleaching relaxation times. PACS 42.60.Gd; 42.55.Xi; 42.70.Hj     

Steady state mode-locking of a 1.34 μm Nd:YVO<Subscript>4</Subscript> laser using a single-walled carbon nanotube saturable absorber

Steady state mode-locked operation of a neodymium laser operating on the ⁴F_3/2 → ⁴I_13/2 transition around 1.3 μm is achieved for the first time using transmitting single-walled carbon nanotube (SWCNT) saturable absorber. The Nd:YVO₄ laser cavity was optimized for large fundamental mode volume generating an average power of 0.8 W at a repetition rate of 127 MHz in a stable train of 16.5 ps long pulses.     

110 W ceramic Nd<Superscript>3+</Superscript> : Y<Subscript>3</Subscript>Al<Subscript>5</Subscript>O<Subscript>12</Subscript> laser

A high-power, continuous-wave 0.6% Nd³⁺-doped ceramic Y₃Al₅O₁₂ (Nd:YAG) laser has been developed. 110 W laser output at 1064 nm was obtained, with a slope efficiency of about 41%. The M² factor was found to be around 6. The laser performance of the ceramic laser material was found to compare favorably with that obtained with single crystal Nd:YAG. PACS 42.55.-f; 42.55.Xi; 42.70.Hj     

20 W single longitudinal mode Nd:YVO<Subscript>4</Subscript> retro-reflection ring laser operated as a self-intersecting master oscillator power amplifier

We demonstrate the stable operation of a 20 W single longitudinal mode TEM₀₀ Nd:YVO₄ ring laser at 1064 nm. Unidirectionality of 2500:1 was imposed through retro-reflection of one of the output arms. An additional extra-cavity pass of the intra-cavity gain medium, in a self-intersecting master oscillator power amplifier setup, is shown to improve the stable TEM₀₀ operation power from ≈15 to 20.0 W. The spatial quality improvement involves splitting of the gain region into oscillator and amplifier sections leading to enhanced fundamental mode selection. It is believed that the segregation is, at least in part, self-organising.     

Characterization of 1.06 μm optical vortex laser based on a side-pumped Nd:GdVO<Subscript>4</Subscript> bounce oscillator

We directly produced for the first time a high-power 1.06 μm vortex mode from a diode-pumped Nd:GdVO₄ bounce amplifier. A maximum output of 17.8 W was achieved for a pump power of 55 W. The corresponding optical efficiency from the diode to the output was above 30%.     

Er,Yb:YAl<Subscript>3</Subscript>(BO<Subscript>3</Subscript>)<Subscript>4</Subscript>—efficient 1.5 μm laser crystal

This article summarizes the latest achievements in the growth and characterization of Er,Yb:YAl₃(BO₃)₄ laser crystal emitting in the 1.5–1.6 μm spectral range. Fundamental spectroscopic parameters relevant to laser performance of Er,Yb:YAB derived from absorption and emission spectra and from excited state dynamics are presented. The laser performance of Er,Yb:YAB in the cw and mode-locked regimes is reported.     

Laser characteristics of 2-µm microchip Tm,Ho:Lu<Subscript>2</Subscript>SiO<Subscript>5</Subscript> laser

Cryogenic temperature operation of a 〈010〉-cut microchip Tm,Ho:Lu₂SiO₅ laser end-pumping by a fiber-coupled laser-diode is presented. A 2.73 W absorbed pump power is used to generate a maximum laser output of 470 mW, representing a 17.2% optical-to-optical conversion efficiency and a 61.7% slope efficiency corresponding to absorbed power. In the experiment, the oscillating wavelength shifting from 2.03 to 2.08 μm has been observed and a single 2.03 μm wavelength oscillation has obtained. To our knowledge, this work is the first time to investigate the Cryogenic temperature operation of microchip Tm,Ho:Lu₂SiO₅.     

Actively Q-switched performance of a mixed crystal Nd:Lu<Subscript>0.5</Subscript>Y<Subscript>0.5</Subscript>VO<Subscript>4</Subscript> at 1.34 μm

The actively Q-switched laser performance of the mixed Nd:Lu_0.5Y_0.5VO₄ crystal was demonstrated for the first time. At the pump power of 7.26 W, the minimum pulse width of 46.6 ns was obtained at the pulse repetition rate of 5 kHz with the cavity length of 80 mm, and the single pulse energy and peak power were calculated to be 42 μJ and 901.3 W, respectively.     

Investigation of the spatial profile of stimulated Raman scattering beams in D<Subscript>2</Subscript> and H<Subscript>2</Subscript> gases using a pulsed Nd:YAG laser at 266 nm

The stimulated Raman scattering (SRS) beam spatial mode structure is studied in H₂ and D₂ gases, in a 60 cm-long high-pressure Raman cell, using a pulsed Nd:YAG laser at 266 nm. The conversion efficiencies of the first and second Stokes in H₂, D₂ and H₂/D₂ mixtures have been measured precisely in the 1–14 atm range. The SRS beam profiles were recorded for different gas pressures in the high-pressure Raman cell and interesting behaviour is revealed. Homogeneous SRS spatial profiles were obtained only for pressures higher than 7 atm. For lower pressures the profiles are either in the form of a ring or of a more complicated shape. The results are explained in terms of nonlinear self-focusing processes during the pump beam propagation in the Raman cell. Also, from our measurements, a more precise value of the nonlinear index of refraction for the H₂ and D₂ at 266 nm is proposed. PACS 42.65.Dr; 42.60.Jf; 42.60.Lh; 42.65.Jx     

End-pumped Tm,Ho:NaY(WO<Subscript>4</Subscript>)<Subscript>2</Subscript> crystal laser at 2.07 μm

We presented an infrared laser output at 2.07 μm with Tm,Ho:NaY(WO₄)₂ crystal end-pumped by 795 nm laser diode at room temperature. The crystal was grown by the Czochralski method with the concentrations of 5 at % Tm³⁺ and 1 at % Ho³⁺. The highest output power was up to 2.7 W corresponding to the crystal temperature being controlled at 283 K. The overall optical conversion efficiency was 5.4% and the slop efficiency was 26%. The output characteristics and the laser threshold affected by the pulse duration and temperature have been studied. We found the stability of the output power was correlative with the crystal temperature heavily. In addition, the wider pulse duration of pump could promote the output power efficiently.     

Self-Q-switched diode-end-pumped Nd: BGO laser

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Growth of β-Ga<Subscript>2</Subscript>O<Subscript>3</Subscript> nanoparticles by pulsed laser ablation technique

This work investigates pulsed laser ablation for Ga₂O₃ nanoparticles. Nanoparticles with diameters of 10 to 500 nm were deposited on silicon substrates in large quantities, by KrF excimer laser ablation of a GaN (99.99% purity) target in high purity nitrogen (99.9995%) background gas at room temperature, without a catalyst. The particle size and phase structure of the as-deposited nanoparticles are examined by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM), and selected-area electron diffraction (SAD). FE-SEM images show that the nanoparticles aggregate to form micron-size nanoclusters at chamber pressures of 1 and 5 Torr. On the other hand, nanoparticles aggregate with chain-like nanostructures, are synthesized at high chamber pressures (10 Torr). TEM images further reveal that chain-like nanostructures are formed by the aggregation of individual spherical and ellipsoidal nanoparticles. Photoluminescence measurement shows stable and broad blue emission at 445 nm. PACS 81.20.-N; 81.15.Fg; 75.50.Vv