CW laser action in acentric NdAl3(BO3)4 and KNdP4O12

We report low-threshold, room-temperature, cw lasing in two new high-Nd-concentration materials, NdAl₃(BO₃)₄ and KNdP₄O₁₂, the first ones with acentric space groups. For both materials, thresholds below 1 mW and slope power conversion efficiencies exceeding 20% have been measured. Fluorescence spectra and lifetimes have been measured in Nd_xGd_1?xAl₃(BO₃)₄ and Nd_xGd_1?xP₄O₁₂.     

A 180 mW Nd:LaSc3(BO3)4 single-frequency TEM00 microchip laser pumped by an injection-locked diode-laser array

A TEM₀₀ single-frequency, diode-pumped microchip laser of Nd(25%):LaSc₃(BO₃)₄ is operated with an output power of 180 mW. For best performance the laser was pumped by the 450 mW diffraction-limited single-frequency radiation of an injection-locked AlGaAs diode-laser array and cooled to the temperature of liquid nitrogen. The active and passive losses of the microchip laser were investigated by measuring the relaxation oscillation frequency and by comparing the experimental results with values obtained from appropriate rate equations. The power-dependent far-field pattern is in good agreement with the intensity distribution calculated by assuming a thermally induced waveguide cavity.     

Passively Q-switched microchip Er, Yb:YAl3(BO3)4 diode-pumped laser

We report, for the first time to our knowledge, a diode-pumped cw and passively Q-switched microchip Er, Yb:YAl(3)(BO(3))(4) laser. A maximal output power of 800 mW at 1602 nm in the cw regime was obtained at an absorbed pump power of 7.7 W. By using Co(2+):MgAl(2)O(4) as a saturable absorber, a TEM(00)-mode Q-switched average output power of 315 mW was demonstrated at 1522 nm, with pulse duration of 5 ns and pulse energy of 5.25 μJ at a repetition rate of 60 kHz.     

Efficient, resonantly pumped, room-temperature Er3+:GdVO4 laser

We report an efficient room-temperature operation of a resonantly pumped Er3+:GdVO4 laser at 1598.5 nm. The maximum continuous wave (CW) output power of 3.5 W with slope efficiency of 56% was achieved with resonant pumping by an Er-fiber laser at 1538.6 nm. With pumping by a commercial laser diode bar stack, a quasi-CW (QCW) output of 7.7 W and maximum slope efficiency of ~53% versus absorbed pump power were obtained. This is believed to be the first resonantly (in-band) pumped, room-temperature Er3+:GdVO4 laser.     

NdP5O14 and NdAl3(BO3)4 lasers at 1.3 μm

We report, for the first time, on room temperature cw laser action of NdP₅O₁₄ and NdAl₃(BO₃)₄ at 1.3 μm wavelength. The emission cross sections of the transition⁴ F _3/2→⁴ I _13/2 are 0.24·10^?19 cm² and 1.74·10^?19 cm², respectively. The lowest observed threshold was 45 mW and the slope efficiency was nearly 10%. The minimum threshold is expected to be about 5 mW of absorbed pump light for both materials.     

High-efficiency resonantly pumped room temperature Ho:YVO4 laser

An efficient 2 μm room temperature Ho:YVO(4) laser resonantly pumped by a 1.94 μm Tm:YAP laser is demonstrated, for the first time to our knowledge, in this Letter. Up to 8.58 W of laser output at 2053 nm is obtained with the optical-to-optical conversion efficiency as much as 41.2%. The output beam had quality of M² factor with Mx(2) of 3.58 and My(2) of 1.76 at 8 W output level. In addition, we also obtained 4.18 W laser output at 2066 nm and 7.04 W at 2040 nm from the Ho:YVO(4) laser with conversion efficiency of 27.8% and 33.8%, respectively.     

Slope efficiency of up to 73% for Yb:Ca4YO(BO3)3 crystal laser pumped by a laser diode

Yb:Ca₄YO(BO₃)₃ (Yb:YCOB) crystal with good quality and large size has been grown by the Czochralski method. The polarization absorption and fluorescence spectra have been measured. The laser action of the Yb:YCOB crystal has been demonstrated when it is pumped by a fiber-coupled laser diode (LD) at the wavelength of 976.4 nm. The pumping threshold is 55 mW, the light-light conversion efficiency is 58.7%, and a slope efficiency of up to 73% is thus calculated. Received: 16 December 1998 / Revised version: 4 February 1999 / Published online: 7 April 1999     

二极管泵浦双掺杂YAG微片自调Q激光器

 利用激光二极管泵浦双掺杂YAG微片晶体，在连续泵浦时获得了重复频率为2.78kHz，脉冲宽度为6ns的自调Q激光输出。并通过预泵浦加脉冲调制电流的方法，实现可控重复率的自调Q脉冲输出。与外腔式自调Q微片激光器相比，这种一体化微片激光器具有更高的转换效率、更窄的输出脉冲宽度和更高的重复频率，同时结构更为简单紧凑，易于调整。     

Passive mode locking of a self-frequency-doubling Yb:YAl(3) (BO(3))(4) laser

We report passive mode-locking experiments with a novel self-doubling laser crystal Yb:YAl(3)(BO(3))(4) (Yb:YAB). The diode-pumped laser was mode locked by an ion-implanted semiconductor saturable absorber mirror. Far off phase matching, soliton mode locking produced pulse widths of 198 fs to 1.4 ps, with up to 660-mW output and optical efficiency of 24% at 1040 nm. The shortest pulses had a peak power of 28 kW with 440-mW average power and 16% efficiency. A few degrees off phase matching, a total of 60 mW of green femtosecond pulses was generated simultaneously. Close to phase matching, the laser produced picosecond pulses and, without infrared output, a total of 270 mW of green output, corresponding to 10% conversion efficiency (absorbed pump to green output).     

Specific heat of YFe3(BO3)4, Y0.5Gd0.5Fe3(BO3)4, and GdFe3(BO3)4

The specific heat was measured in the range 0.4–300 K in YFe₃(BO₃)₄, Y_0.5Gd_0.5Fe₃(BO₃)₄, and GdFe₃(BO₃)₄ single crystals. Sharp anomalies were found at temperatures of first-order structural, second-order antiferromagnetic, and first-order spin-reorientational transitions. A Néel temperature of about 37 K was found to be virtually independent of presence of rare-earth ions, indicating rather weak coupling of Gd and Fe subsystems. The contribution of the magnetic system to specific heat was separated through the scaling procedure allowing determination of the magnetic entropy of Fe and Gd subsystems. At the lowest temperatures, the specific heat in GdFe₃(BO₃)₄ exhibits a Schottky-type anomaly, which is due to Gd³⁺ eightfold degenerate ground-level splitting by the internal magnetic field of the Fe subsystem of about 7 T. The text was submitted by the authors in English.     

Thermo-optic characterization of Yb:YAl3(BO3)4 laser crystal

Principal thermo-optic coefficients, dn _o/dT and dn _e/dT, are determined for 7at.%Yb: YAl₃(BO₃)₄ crystal by the use of a minimum deviation method, modified for anisotropic, optically uniaxial crystals. Direct measurements are accompanied by modeling of the dn/dT versus light wavelength dependence, yielding analytic thermo-optic dispersion formulae for the spectral range of 0.4–1.6 μm. At the wavelength of 1030 nm, dn _o/dT = 3.5 and dn _e/dT = 6.0 [10^?6 K^?1]. Sellmeier formulas are evaluated for the principal refractive indices n _o and n _e. The thermal coefficients of the optical path are determined for the principal crystal cuts of Yb:YAl₃(BO₃)₄, a-cut and c-cut, and light polarizations, π or σ. Finally, thermal lens parameters are evaluated for Yb:YAl₃(BO₃)₄ crystals on the basis of measured material parameters.     

Output-coupling-dependent polarization state of a continuous-wave Yb:YCa4O(BO3)3 laser

High-power continuous-wave laser operation was demonstrated with a y-cut Yb:YCa(4)O(BO(3))(3) crystal, showing critical dependence on the output coupler used. Polarized laser oscillation with E||x was obtained at 1085.6 nm by using a coupler of 0.5% transmission, yielding an output power of 7.3 W with an optical-to-optical efficiency of 63%. Higher output couplings (>/=2%) led to polarized oscillation with E||z at laser wavelengths 相似文献   

Generation of 90-fs pulses from a mode-locked diode-pumped Yb(3+):Ca(4)GdO(BO(3))(3) laser

A diode-pumped Yb>(3+):Ca(4)GdO(BO>(3))(3) (Yb:GdCOB) laser generating 90-fs pulses at a center wavelength of 1045 nm is demonstrated. This is, to our knowledge, the shortest pulse duration obtained from an ytterbium laser with a crystalline host. This laser is mode locked with a high-finesse semiconductor saturable-absorber mirror and emits 40 mW of average power at a repetition rate of 100 MHz.     

Dual-polarization and dual-wavelength diode-pumped laser operation from a birefringent Yb3+-doped GdAl3(BO3)4 nonlinear crystal

From two positions of the concave output mirror of the laser cavity, diode-pumped ordinary or extraordinary polarization lasing of an Yb³⁺-doped GdAl₃(BO₃)₄ nonlinear birefringent crystal is obtained. Translating the mirror at an intermediate position, simultaneous ordinary and extraordinary polarization lasing at 1046 (2.5 nm FWHM) and 1040 nm (2.2 nm FWHM), respectively, is obtained with up to 53% slope efficiency. Using a YAG:Cr⁴⁺ saturable absorber for passive Q-switching the cavity, ordinary and extraordinary pulses are obtained with an energy as high as 236 μJ and with about 30 ns duration. The two pulses of orthogonal polarizations can be separated by up to a few hundred ns, depending on the experimental conditions. The simultaneity of the pulses is observed but is difficult to maintain. A model constituted by two coupled equations reproduces reasonably well the experimental data. Repetition rates up to 3 kHz have been explored, corresponding to 4.65 W absorbed pump power. PACS 42.55.Xi; 42.60.Gd; 42.25.Ja     

New green self-frequency-doubling diode-pumped Nd:Ca4GdO(BO3)3 laser

3+ :Ca₄GdO(BO₃)₃ (Nd:GdCOB). 21 mW of green cw laser emission for an absorbed pump power of 820 mW were achieved under laser diode-pumping. 64 mW of green cw laser output were obtained with 1 W of absorbed pump power under titanium-sapphire pumping. Its availability in large-size crystals with good optical quality makes Nd:GdCOB a true challenger to the best SFD laser crystal reported so far: Nd:YAl₃(BO₃)₄ (Nd:YAB or NYAB). Received: 2 March 1998/Revised version: 20 May 1998     

Type-I non-critically phase-matched second-harmonic generation in Gd1-xYxCa4O(BO3)3

Second-harmonic generation was z-cut observed Gd_1-xY_xCa₄O(BO₃)₃ (Gd_1-xY_xCOB) and the dependence of the phase-matching wavelength on the mixing ratio x has been investigated. The dependence on both temperature and angle tuning was examined as well. We found the suitable composition for noncritical frequency doubling at 930 nm, which is the lasing wavelength of Nd:YAlO₃ on the ⁴F_3/2?⁴I_9/2 transition. Received: 19 April 1999 / Published online: 5 May 1999     

Optical properties and laser potential of dysprosium doped YAl 3 (BO 3 ) 4 (YAB) crystal

The absorption and emission spectra were measured at 5 and 300 v K. The positions of the selected Dy 3+ levels and their Stark components, determined from optical spectra at 5K, are presented. In this work an attempt is made to assess the potential of dysprosium doped YAl 3 (BO 3 ) 4 crystal as a laser active material operating near 570 v nm. The emission cross-section of a potential laser line at 570 v nm connected with 4 F 9/2 M 6 H 13/2 transition was estimated.     

Second-harmonic generation from a KBe(2) BO(3)F(2) crystal in the deep ultraviolet

By use of KBe(2)BO(3)F(2) (KBBF) crystal with a size of 10 mmx10 mm x1.2 mm and a special prism-coupling technique (PCT), fourth-harmonic generation of Ti:sapphire laser systems from 200 to 179.4 nm has been achieved. Moreover, with a Ti:sapphire laser with a 50-fs pulse duration and a 1-kHz repetition rate, conversion efficiency as high as 13% from 400 to 200 nm without any surface-loss correction has also been obtained. The data show that with the PCT a KBBF crystal can produce deep-UV coherent light with measurable power output.