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.     

Cr(2+):ZnSe and Co(2+):ZnSe saturable-absorber Q switches for 1.54-mum Er:glass lasers

Passive Q switching of Er:glass lasers has been demonstrated with Cr(2+):ZnSe and Co(2+):ZnSe saturable absorbers. A pulse duration of ~50ns and an output pulse energy of 5 mJ were obtained with both Co:ZnSe and Cr:ZnSe passive shutters. A Q-switched conversion efficiency of as much as 26% was obtained for Cr:ZnSe. Theoretical modeling exhibits satisfactory agreement with experimental data.     

Diode-pumped self-Q-switched single-frequency 946-nm Nd(3+), Cr(4+):YAG microchip laser

A stable low-threshold self-Q-switched diode-pumped 946-nm Nd(3+), Cr(4+):YAG microchip laser operating in single frequency and fundamental transverse mode is reported. The output characteristics of the microchip laser were investigated under cw and pulsed pumping. By combination of the infrared microchip and an external frequency doubler, 473-nm pulses with a conversion efficiency of 18% were achieved.     

1.9- m and 2.0- m laser diode pumping of Cr(2+) :ZnSe and Cr(2+) :CdMnTe

Efficient diode pumping at wavelengths of 1.9 and 2.0microm of a Cr(2+): ZnSe laser with an output power of 105 mW and a slope efficiency of 35% with respect to the absorbed pump power is presented. In addition, Cr(2+): CdMnTe has been laser diode pumped as well as operated in the continuous-wave regime, to the best of our knowledge for the first time.     

Continuous-wave operation and Q-switched mode locking of Cr(4+):YAG microchip lasers

Cw-operation, gain-switched, and passively Q -switched mode locking of Cr(4+): YAG microchip lasers with output powers of several hundred milliwatts is demonstrated experimentally in the eye-safe region near 1.5microm . Requirements for cw mode locking of such lasers are investigated by numerical simulations.     

Passively Q-Switched Ho:SSO Laser by Use of a Cr~(2+):ZnSe Saturable Absorber

A cw operation and a passively Q-switched(PQS) Ho:SSO laser(Cr~(2+):ZnSe as a saturable absorber) end-pumped by a Tm:YAP laser operating at near room temperature are reported. It is the first time to report a PQS Ho:SSO laser. For the cw mode, a maximum cw output power of 3.0 W is obtained, corresponding to a slope effciency of31.4%. For the PQS mode, a Cr~(2+):ZnSe is used as the saturable absorber, with transmission of 88.4% at 2112 nm.A maximum pulse energy of 1.29 mJ is obtained, corresponding to the pulse repetition frequency of 2.42 kHz. In this study, we change the distance between:Cr~(2+):ZnSe and the output mirror to research the pulse characteristic of the PQS Ho:SSO laser. The minimum pulse width of 73.5 ns is obtained, corresponding to the pulse energy of0.9 mJ and the pulse repetition frequency of 2.65 kHz.     

Mode-locked Cr(2+):ZnSe laser

We describe active mode locking of a Cr(2+):ZnSe laser operating near 2.5 mum. The laser produces 4.4-ps transform-limited Gaussian-shaped pulses and produces 82 mW of average power.     

ZnS:Cr and ZnSe:Cr thin‐film waveguide structures as electrically pumped laser media with an impact excitation mechanism

ZnS:Cr and ZnSe:Cr are the focus of studies as media for broadly tunable optically pumped lasers operating in the near‐ and mid‐IR regions. It is of great interest to obtain such lasers electrically pumped. The effective electrical excitation of Cr²⁺ ions was demonstrated only in the case of the impact mechanism for thin‐film structures with insulator layers between an electroluminescent film and electrodes, which prevent avalanche breakdown at high electric field (≥ 1 MV/cm). To obtain lasing, the waveguide electroluminescent structures were used. For the first time, the stimulated emission and the laser oscillation were demonstrated in the ZnS:Cr waveguide structures. Although the lasing is unstable as yet, these results lay the foundations of a new direction in laser physics aimed at creation of electrically pumped lasers by dint of impact excitation. Published results concerning various aspects of ZnS:Cr and ZnSe:Cr thin films and waveguide structures as promising electrically pumped laser media are reviewed. The causes of the instability of the laser oscillation and means of improving their characteristics are also considered.     

Continuous-wave broadly tunable Cr2+:ZnSe laser

We report room-temperature operation of an all-solid-state broadly tunable continuous-wave Cr(2+):ZnSe laser. Output power of 250 mW, an absorbed power slope efficiency of 63%, and continuous tunability from 2138 to 2760 nm are demonstrated.     

Direct diode-pumped continuous-wave near-inf rared tunable laser operation of Cr(4+):forsterite and Cr(4+):Ca(2)GeO(4)

Continuous-wave tunable laser operation of direct diode-pumped Cr(4+):Mg(2)SiO(4) (Cr:forsterite) and Cr(4+):Ca(2)GeO(4) (cunyite) crystal were demonstrated. Diode-pumped Cr:forsterite was tunable over the 1236-1300-nm spectral range. The maximum output of 10 mW was measured at 1260 nm for 640 mW of pump power absorbed by the crystal. Diode-pumped laser operation of cunyite was also demonstrated over the 1390-1475-nm range. Free-running 20-mW output was centered at 1410 nm.     

Demonstration of room-temperature laser action at 2.5 mum from Cr(2+):Cd(0.85)Mn(0.15)Te

Room-temperature laser action from Cr(2+)-doped Cd(0.85)Mn(0.15)Te has been demonstrated for what is believed to be the first time. We achieved pulsed laser operation centered at ~2.5mu m by pumping into the mid-infrared absorption band of Cr(2+) ions by use of the 1.907- mum output of a H(2) Raman-shifted Nd:YAG laser. The output of the free-running Cr(2+):Cd(0.85)Mn(0.15)Te laser had a width of ~50 nm (FWHM), and the slope efficiency was calculated to be 5.5% under nonoptimum conditions.     

Generation of sub-10-fs pulses from a Kerr-lens mode-locked Cr(3+):LiCAF laser oscillator by use of third-order dispersion-compensating double-chirped mirrors

Pulses as short as 9 fs at 220-mW average power and a 97-MHz repetition rate are generated from a cw Ti:sapphire-pumped Kerr-lens mode-locked Cr(3+)LiCAF laser oscillator employing broadband double-chirped mirrors for second- and third-order dispersion compensation. Fine adjustment of dispersion is accomplished with a fused-silica prism pair. The result demonstrates that Raman-induced self-frequency shifting of the pulse does not limit sub-10-fs pulse generation from colquiriite crystals.     

Middle-infrared random lasing of Cr doped ZnSe, ZnS, CdSe powders, powders imbedded in polymer liquid solutions, and polymer films

Room temperature (RT) middle-infrared (Mid-IR) random lasing of chromium- (Cr) doped ZnSe, ZnS, and CdSe powders, powders imbedded in perfluorocarbon liquid polymer solutions, and fluorocarbon polymer films is reported. Laser active powders were prepared without a stage of bulk crystal growth by annealing of starting chemicals (pure, mixed ZnSe:CrSe; ZnS:CrS; CdSe:CrSe). Mixture of the different semiconductor hosts allows tuning oscillation wavelength from 2240 to 2630 nm.     

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.     

Intracavity-pumped Cr2+:ZnSe laser with ultrabroad tuning range between 1880 and 3100 nm

We obtained, what is to our knowledge, record tuning from an intracavity-pumped gain-switched Cr2+:ZnSe laser. In the experiments, a polycrystalline Cr2+:ZnSe sample with an absorption of about 43% at 1570 nm was used to minimize reabsorption losses at the lasing wavelengths below 2000 nm. By placing the gain medium inside the cavity of a pulsed KTP optical parametric oscillator (OPO) operating at 1570 nm, smooth, continuous tuning was achieved in the 1880-3100 nm range with four different sets of cavity optics. As high as 145 mW of average laser output power was obtained at 2365 nm with 1.2 W of intracavity OPO power.     

Picosecond tunable mode locking of a Cr2+:ZnSe laser with a nonlinear mirror

We report on a nonlinear mirror (NLM) scheme that enables, for the first time to the best of our best knowledge, tunable mode locking of a Cr2+:ZnSe laser in the picosecond regime. The NLM-used as the output coupler of the laser cavity-consists of a periodically poled lithium niobate (PPLN) crystal with a fan-out grating coupled with a dichroic mirror and a wedged dispersive YAG plate. The Cr2+:ZnSe laser, pumped by a CW thulium-doped fiber laser, delivers 85?ps pulses at a repetition rate of 220?MHz with a 300?mW average power. Thanks to the use of a fan-out PPLN crystal, we benefit from the wide tunability of the Cr2+:ZnSe laser and achieve mode locking over the whole 2.44-2.55?μm range while maintaining a narrow-linewidth emission suitable for time-resolved nonlinear spectroscopy applications.     

Crystalline Cr²⁺:ZnSe/chalcogenide glass composites as active mid-IR materials

We propose new transition metal (TM)-doped ZnSe/As?S?:As?Se? composite materials for mid-IR fiber lasers. The composites are the suspension of crystalline micro- and nanosized TM2?:ZnSe or TM2?:ZnS powders in chalcogenide glasses with the refraction index matching. Mid-IR room-temperature lasing of Cr2?:ZnSe/As?S?:As?Se? microcomposite material is demonstrated at the 2.4 μm wavelength.     

Highly efficient infrared-to-visible energy upconversion in Er(3+):Y(2)O(3)

Very intense green and red emission was observed at room temperature from the (4)S(3/2) and (4)F(9/2) levels of Er(3+):Y(2)O(3). A cw diode laser at 975 nm was used as a pump for resonant sequential excitation of the (4)I(11/2) and (4)F(7/2) levels. The fluorescence was easily visible to the naked eye, even with 27 mW of excitation power. It was found that at 850 mW of cw excitation power the total luminance was 39,000 cd/m(2). This corresponds to ~100 muW of green emission and 270 muW of red emission.     

Efficient grating-tuned mid-infrared Cr2+:CdSe laser

Room-temperature, all-solid-state, broadly tunable laser operation of Cr(2+) -doped CdSe has been demonstrated. Pumping with a Q -switched Tm, Ho:YLF laser running at a 1-kHz repetition rate achieved broadband output of 500 mW at 2.6mum with 48% absorbed power slope efficiency. With reduced efficiency, as much as 815 mW of power was obtained. With a diffraction grating, the Cr(2+): CdSe laser was tuned from 2.3 to 2.9mum with 10-nm bandwidth (FWHM) and output power up to 350 mW.     

Generation of 20-fs pulses by a prismless Cr(4+):YAG laser

Ultrafast optical pulses shorter than 20 fs with 400-mW average power at a 110-MHz repetition rate have been generated by a Cr(4+):YAG laser with only double-chirped mirrors for dispersion compensation. The corresponding pulse spectrum has a peak intensity at 1450 nm and extends from 1310 to 1500 nm full width at half-maximum (FWHM). These pulses, which are believed to be the shortest generated to date from a Cr(4+):YAG laser, are only four optical cycles within the FWHM intensity width.