Broadly tunable continuous-wave diode-pumped Cr4+:YAG laser

We describe a widely tunable, continuous-wave, room temperature Cr⁴⁺:YAG laser with direct pumping by two high brightness 4 W InGaAs laser diodes. In a tunable configuration, the output wavelength covered a span of 197 nm (1356–1553 nm) and provided a maximum power of 195 mW. A maximum non-tunable output power of 260 mW was obtained with a 0.6% transmission output coupler (OC) and 6.6 W of incident pump power. Pumping at two different wavelengths, 911 and 968 nm, was investigated.     

Directly diode-pumped tunable continuous-wave room-temperature Cr4+:YAG laser

We report what is to our knowledge the first directly diode-pumped tunable (over 120 nm) continuous-wave Cr(4+): YAG laser, operating near 1.5 mum . At room temperature the laser delivered as much as 200 mW of power at 4 W of absorbed pump power. We also report observation of slow laser output degradation and bleaching in highly concentrated cyrstals, which we suggest is due to a photorefractive phenomenon.     

Broadly tunable compact continuous-wave Cr(2+):ZnS laser

We report the development of a continuous-wave, room-temperature Cr(2+) ZnS laser that is compact and tunable over 700 nm. The laser is pumped by a diode-pumped Er-fiber laser and generates 0.7 W of linearly polarized radiation at 2.35microm , at up to 40% slope efficiency. Cr(2+) ZnS directly diode-pumped at 1.6microm yields polarized radiation that is tunable over 400 nm at up to 25 mW of output power. A comparison of Cr(2+) ZnS with Cr ZnSe (70 mW, 350 nm) in a similar setup is given. As opposed to Cr ZnSe, the Cr ZnS laser is intrinsically polarized. Finally, we observe sensitization of the output radiation by a few milliwatts of the visible (470-500-nm) and near-infrared (740-770-nm) radiation.     

Widely tunable continuous-wave diode-pumped 2-microm Tm-Ho:KYF4 laser

Continuous-wave laser action at approximately 2 microm is demonstrated in a Tm-Ho:KYF4 single crystal at room temperature. Crystal growth, spectroscopic measurements, and laser results are presented. An output power in excess of 250 mW is obtained with a tuning range of 99 nm, the largest ever published, to our knowledge, for Tm-Ho in any crystalline host.     

Performances of Cr:LiSrAlF(6) and Cr:LiSrGaF(6) for continuous-wave diode-pumped Q-switched operation

We have developed a Cr:LiSrGaF(6) laser that produces, in Q -switched operation, four times as much energy (12 microJ at 10 kHz) as a Cr:LiSrAlF(6) laser under the same conditions of pumping (four red diodes emitting 400 mW). By using a theoretical model for small-signal gain calculations, we show that these better performances are mainly attributable to the fact that thermal quenching of fluorescence is lower in Cr:LiSrGaF(6) than in Cr:LiSrAlF(6).     

Efficient continuous-wave and Q-switched operation of a diode-pumped Yb:KLu(WO4)2 laser with self-Raman conversion

Efficient cw and passively Q-switched operation with self-stimulated Raman scattering conversion was demonstrated in a compact diode-pumped Yb:KLu(WO4)2 laser. A cw output power of 3.28 W was obtained with an optical efficiency of 48.2% and a slope efficiency of 78.2% with respect to the incident pump power. Stable Q-switched operation was achieved with a Cr4+:YAG saturable absorber, generating 32.4 microJ fundamental pulses with a duration of 1.41 ns at 1030.6 nm and 14.4 microJ Raman pulses with a duration of 0.71 ns at 1137.6 nm. At an incident pump power of 7.0 W, the average output power reached 0.9 and 0.4 W for fundamental and Raman radiation, with slope efficiencies of 32.1% and 14.1%, respectively.     

Efficient laser operation of heavily doped Cr4+:forsterite

Pulsed laser operation of a new high Cr4+ concentration forsterite crystal is reported. Slope efficiencies of 13% and 5% have been obtained for 1064 and 532nm pumping. Results are compared with the performance of three other forsterite crystals. A threefold enhancement in operating efficiency is obtained over standard low dopant-level material. Tuning ranges have also been investigated. This revised version was published online in November 2006 with corrections to the Cover Date.     

Highly efficient continuous-wave laser operation of laser diode-pumped Nd,Y:CaF_2 crystals

The effect of co-doping Y3 tand the doping concentration of Nd3 ton the spectroscopic properties and laser performance of Nd:CaF2 crystals are investigated systematically. For a 0.5% Nd:CaF2 crystal, the emission lifetime at 1.06 μm increases from 18 to 361 μs by co-doping 10 at.% Y3 t, while the emission cross section increases to 4.27 × 10-20cm2 at 1054 nm. With a 10 at.% doping concentration of Y3 t, Nd; Y:CaF2 crystals concentrate emission bands that peak at 1054 nm with shoulders at 1063 nm, and FWHM at about 30 nm. A diode-pumped,highly efficient laser operation is obtained with 0.5% Nd, 10% Y:CaF2 and 0.6% Nd, 10% Y:CaF2 crystals, with slope efficiencies over 30% and 27%, respectively, and a maximum output power up to 901 m W.     

Cr4+:Ca2GeO4激光晶体生长及结构表征

采用助熔剂法,以CaCl₂为助熔剂,生长Cr⁴⁺ :Ca₂GeO₄新型近红外可调谐激光晶体.通过X射线衍射(XRD)、激光Raman光谱、X射线光电子能谱(XPS)等方法对晶体进行结构表征.结果表明,得到的晶体为单斜晶系镁橄榄石结构的低温γ-Cr⁴⁺ :Ca₂GeO₄单晶,晶格参数为a=5.3209 (1 =0.1 nm)     

Frequency-stable operation of a diode-pumped continuous-wave RbTiOAsO(4) optical parametric oscillator

Frequency-stable operation of a diode-pumped continuous-wave optical parametric oscillator (OPO) of RbTiOAsO(4) is demonstrated. Piezoelectric and fast electro-optic control of the optical length of the two-mirror OPO cavity (resonant for the pump and the idler waves) compensates for thermal changes in the refractive index of the OPO crystal (induced by absorption of pump light) and acoustic perturbations of the cavity length. Pumped by 405mW of the 810-nm output of a GaAlAs masterf-oscillator-tapered-amplifier diode laser system, the OPO generates a power-stable single-frequency signal wave at 1.24microm with an output of 84mW and a spectral bandwidth of less than 10MHz.     

High-power diode-pumped Q-switched and mode-locked Nd:YVO(4) laser with a Cr(4+):YAG saturable absorber

We demonstrate a high-power passively Q -switched and mode-locked Nd:YVO(4) laser with a Cr(4+):YAG saturable absorber. 2.7 W of average power with an 18-kHz Q -switched repetition rate was generated at a 12.5-W pump power. The peak power of a single pulse near the maximum of the Q -switched envelope was greater than 100 kW.     

Erbium fiber laser-pumped continuous-wave microchip Cr(2+):ZnS and Cr(2+):ZnSe lasers

Efficient continuous-wave (cw) lasing of Cr(2+):ZnS and Cr(2+):ZnSe crystals in external hemispherical cavities and in a microchip configuration under Er-fiber-laser pumping at room temperature are reported. The key result is what is believed to be the first successful demonstration of cw Cr(2+):ZnS and Cr(2+):ZnSe microchip lasers with maximum output powers of 63 and 100 mW at 2320 and 2520 nm, with slope efficiencies of 53% and 20%, respectively.     

High-power diode-pumped picosecond Nd(3+):YVO(4) laser

A diode-pumped Nd(3+):YVO(4) laser passively mode locked by a nonlinear mirror based on second-harmonic generation has been developed. Pumping with a fiber-coupled 10-W diode array, we generated nearly diffraction limited, linearly polarized 11-ps pulses at 1064nm, with average power of 2.7 W at a 150-MHz repetition rate. Pulses as short as 7.9 ps were measured with reduced output power (1.35 W) by optimal focusing in the nonlinear crystal.     

Study on characteristics of diode-pumped continuous-wave tunable and passively Q-switched Tm:SSO laser

In this paper, we present a diode-pumped continuous-wave tunable and Q-switched Tm:SSO laser with a semiconductor saturable absorber mirror. In continuous-wave regime, a maximum output power of 340 mW at 1,980.7 nm was obtained. With a quartz plate, wavelength-tunable continuous-wave operation was achieved from 1,922 to 2,020 nm. In Q-switched regime, a maximum output pulse energy of 14.7 μJ under a repetition rate of 800 Hz and a minimum pulse width of 7.6 μs corresponding to a repetition rate of 8.8 kHz around 1,974.4 nm were obtained from the passively Q-switched Tm:SSO laser.     

Excited state absorption measurements and laser potential of Cr4+ doped Ca2GeO4

4+ doped Ca₂GeO₄ in the 450–2000 nm spectral region at room temperature are presented. Weak ESA bands due to the transition are observed between 1200 and 2000 nm and stronger ESA bands due to peak below 1200 nm. The overlap of the ESA band with the emission which extends from 1100 to about 1600 nm will significantly affect the laser performance of Cr⁴⁺ doped Ca₂GeO₄. The effective peak stimulated emission cross section at 1350 nm in E∥b polarization is only about 3×10^-20 cm². However, our results indicate that tunable laser action between 1300 and 1500 nm should, in principle, be possible. Received: 28 October 1996     

Tunable continuous-wave operation of a Cr3+,Li+:Mg2SiO4 laser

Room-temperature tunable cw laser oscillation of Cr3+ ions in forsterite crystals (Mg2SiO4) codoped with chromium and lithium has been demonstrated, for the first time to the authors' knowledge, in pumping a crystal with a Ti:sapphire laser into the first excited level of Cr3+ ions (4A2-4T2 transition). The laser is smoothly tunable in the region of 1095-1170 nm. A slope efficiency as great as 4.4% has been achieved.     

Real-time two-dimensional imaging in scattering media by use of a femtosecond Cr(4+):forsterite laser

An original femtosecond Cr(4+):forsterite laser source associated with a nonlinear optical correlator was used for imaging through scattering media with 1220-nm light. The system, which operates as an ultrafast optical gate by sum-frequency generation in a nonlinear crystal, was able to detect the light reflected from a resolution chart hidden in a turbid medium, at an attenuation of as much as 15 mean free paths. When the object was illuminated with a collimated beam, real-time two-dimensional images were obtained, with a maximum transverse resolution of ~20 microm.     

Phase conjugation in a continuous-wave diode-pumped Nd:YVO4 laser

We demonstrate phase conjugation and dynamic holography by degenerate four-wave mixing in a continuous-wave diode-pumped Nd:YVO₄ laser for the first time. A phase-conjugate reflectivity of 1.4% is obtained with a 12 W diode power. The experimental results and the optimizing parameters, such as the cavity mirror reflectivities, are compared with results from a steady-state theoretical analysis. Received: 6 April 1999 / Published online: 24 June 1999     

CW and Q-switched diode-pumped laser operation of Yb3+:NaLa(MoO4)2

Continuous wave (CW) and Q-switched diode-pumped laser operation of Yb³⁺:NaLa(MoO₄)₂ single crystal was to our knowledge, demonstrated for the first time. A CW output power of 220 mW and slope efficiency of 46% were obtained. Q-switched laser operation was achieved with a pulse duration of 60 ns average output power of 70 mW and slope efficiency of 22%. PACS 42.55.Xi; 42.60.Pk; 42.60.Gd.     

Spectroscopy and continuous-wave diode-pumped laser action of Yb3+:YVO4

The growth, spectroscopic properties, and laser performance of Yb:YVO4 crystal with laser diode pumping are reported. A peak absorption cross section of 7.4 x 10(-20) cm2 at 985 nm, a radiative lifetime of 0.25 ms, and a stimulated-emission cross section of 1.25 x 10(-20) cm2 at 1008 nm for pi polarization were determined for the Yb3+ ions in YVO4. Continuous-wave laser action of Yb:YVO4 at 1020-1027 nm was demonstrated with an output power of 610 mW and a slope efficiency of 49%.