Efficient tunable laser operation of Tm:KGd(WO4)2 in the continuous-wave regime at room temperature

Tm:KGd(WO/sub 4/)/sub 2/ is studied as a three-level laser on the /sup 3/F/sub 4/ /spl rarr/ /sup 3/H/sub 6/ transition and a tunable source in the 2-/spl mu/m spectral range, operating at room temperature. An overall tunability extending from 1790 to 2042 nm is achieved with maximum output powers of 400 mW for an absorbed pump power of 1 W. Various doping levels, pump wavelengths and polarization configurations are compared and the advantages of the monoclinic double tungstates over other Tm-hosts are outlined

Green luminescence of Er3+ in stoichiometric KYb(WO4)2 single crystals

We grew good-optical-quality KYb~WO4)2 single crystals doped with erbium ions by the top seeded solution growth slow cooling method. Optical absorption of erbium was performed at room temperature ~RT! and at 6 K. Green photoluminescence of erbium was achieved at RT and 6 K after selective excitation of ytterbium ions at 940 nm (10 638 cm21). The splitting of all found excited energy levels and the ground energy level of erbium in KYb~WO4)2 is presented derived from the accurate absorption and emission measurements, respectively. The lifetime of the Stokes and the anti-Stokes green emissions of erbium were measured after excitation at 488 nm (20 490 cm21) and 940 nm(10 638 cm21), respectively. We propose applying the up-conversion model to the observed green emission

1.48 and 1.84 µm thulium emissions in monoclinic KGd(WO4)2 single crystals

By exciting at 788 nm, we have characterized the near infrared emissions of trivalent thulium ions in monoclinic KGd(WO4)2 single crystals at 1.48 and 1.84 mm as a function of dopant concentration from 0.1% to 10% and temperature from 10 K to room temperature. We used the reciprocity method to calculate the maximum emission cross-section of 3.0310220 cm2 at 1.838 mm for the polarization parallel to the Nm principal optical direction. These results agrees well with the experimental data. Experimental decay times of the 3H4!3F4 and 3F4!3H6 transitions have been measured as a function of thulium concentration

Efficient tunable laser operation of Tm:KGd(WO4)2 in the continuous-wave regime at room temperature

Tm:KGd(WO/sub 4/)/sub 2/ is studied as a three-level laser on the /sup 3/F/sub 4/ /spl rarr/ /sup 3/H/sub 6/ transition and a tunable source in the 2-/spl mu/m spectral range, operating at room temperature. An overall tunability extending from 1790 to 2042 nm is achieved with maximum output powers of 400 mW for an absorbed pump power of 1 W. Various doping levels, pump wavelengths and polarization configurations are compared and the advantages of the monoclinic double tungstates over other Tm-hosts are outlined

Sensitization of Er3+ emission at 1.5m (mu)m by Yb3+ in KYb(WO4)2 single crystals

We present our recent achievements in the growth and spectroscopic characterization of KYb(WO4)2 crystals doped with erbium ions ~hereafter KYbW:Er!. We grew single crystals of KYbW:Er at several erbium concentrations with optimal crystalline quality by the top-seeded-solution growth ~TSSG! slow-cooling method. We carried out spectroscopic measurements related to the polarized optical absorption and optical emission at room temperature ~RT! and low temperature ~6 K!. The splitting of the excited energy levels and the ground energy level of erbium in KYbW were determined, derived from the absorption and emission measurements at 6 K, respectively. We determined the near infrared, around 1.5 mm (6667 cm21), emission channels from the emission spectrum, and used the reciprocity method to calculate a maximum emission cross section of 2.7310220 cm2 for the polarization parallel to the Nm principal optical direction for the 1.534 mm (6519 cm21) infrared emission. We measured the lifetime of the 2F5/2→2F7/2 transition of ytterbium and the 4I13/2→4I15/2 transition of erbium at RT for several erbium concentrations. Finally, we present the Judd-Ofelt calculations for the KYbW:Er system

Erbium spectroscopy and 1.5-micrometre emission in KGd(WO4)2: Er,Yb single crystals

We grew good-optical-quality KGd(WO/sub 4/)/sub 2/ single crystals doped with erbium and ytterbium ions at several concentrations of dopants using the top-seeded-solution growth slow-cooling method (TSSG). We performed the spectroscopic characterization of this material related to the 1.5-mm infrared emission of erbium which is interesting for laser applications. To do this, we carried out polarized optical absorption at room temperature (RT) and at low temperature (6 K) and performed luminescence studies of the emission and lifetime. We obtained the 1.5-mm emission of erbium after selective laser pump excitation of the ytterbium ion and energy transfer between the two ions. The maximum emission cross section for 1.5 mm was about 2.56/spl times/10/sup -20/ cm/sup 2/ for the polarization of light with the electric field parallel to the N/sub m/ principal optical direction. This value was higher than for other erbium-doped materials with application in solid-state lasers such as LiYF/sub 4/:Er(YLF:Er), Y/sub 3/Al/sub 5/O/sub 12/:Er(YAG:Er), YAlO/sub 3/:Er, and Al/sub 2/O/sub 3/:Er

Erbium spectroscopy and 1.5-micrometre emission in KGd(WO4)2: Er,Yb single crystals

We grew good-optical-quality KGd(WO/sub 4/)/sub 2/ single crystals doped with erbium and ytterbium ions at several concentrations of dopants using the top-seeded-solution growth slow-cooling method (TSSG). We performed the spectroscopic characterization of this material related to the 1.5-mm infrared emission of erbium which is interesting for laser applications. To do this, we carried out polarized optical absorption at room temperature (RT) and at low temperature (6 K) and performed luminescence studies of the emission and lifetime. We obtained the 1.5-mm emission of erbium after selective laser pump excitation of the ytterbium ion and energy transfer between the two ions. The maximum emission cross section for 1.5 mm was about 2.56/spl times/10/sup -20/ cm/sup 2/ for the polarization of light with the electric field parallel to the N/sub m/ principal optical direction. This value was higher than for other erbium-doped materials with application in solid-state lasers such as LiYF/sub 4/:Er(YLF:Er), Y/sub 3/Al/sub 5/O/sub 12/:Er(YAG:Er), YAlO/sub 3/:Er, and Al/sub 2/O/sub 3/:Er

Crystal growth and spectroscopic characterization of Tm3+-doped KYb(WO4)2 single crystals.

In this paper we present the crystal growth and optical characterization of thulium-doped KYb(WO4)2 ~hereafter KYbW!. We grew thulium-doped KYbW monoclinic single crystals with optimal crystalline quality by the top-seeded-solution-growth ~TSSG! slow-cooling method. Thulium spectroscopy was characterized in this host. The Judd-Ofelt parameters determined were V250.14310220 cm2, V450.21310220 cm2, and V650.10310220 cm2. The room temperature lifetimes measured for KYbW:Tm 1% were t(1G4) 560–70 ms, t(3H4)590 ms and t(3F4)5200 ms. We calculated the emission cross section for several channels. There was an important blue emission after pumping resonantly to the stoichiometric ytterbium at 980 nm, and we studied the emission channels of thulium. The presence of thulium luminescence is proof of the large transfer of energy in this compound

Growth, optical characterization, and laser operation of a stoichiometric crystal KYb(WO4)(2)

We present our recent achievements in the growing and optical characterization of KYb(WO4)2 (hereafter KYbW) crystals and demonstrate laser operation in this stoichiometric material. Single crystals of KYbW with optimal crystalline quality have been grown by the top-seeded-solution growth slow-cooling method. The optical anisotropy of this monoclinic crystal has been characterized, locating the tensor of the optical indicatrix and measuring the dispersion of the principal values of the refractive indices as well as the thermo-optic coefficients. Sellmeier equations have been constructed valid in the visible and near-IR spectral range. Raman scattering has been used to determine the phonon energies of KYbW and a simple physical model is applied for classification of the lattice vibration modes. Spectroscopic studies (absorption and emission measurements at room and low temperature) have been carried out in the spectral region near 1 µm characteristic for the ytterbium transition. Energy positions of the Stark sublevels of the ground and the excited state manifolds have been determined and the vibronic substructure has been identified. The intrinsic lifetime of the upper laser level has been measured taking care to suppress the effect of reabsorption and the intrinsic quantum efficiency has been estimated. Lasing has been demonstrated near 1074 nm with 41% slope efficiency at room temperature using a 0.5 mm thin plate of KYbW. This laser material holds great promise for diode pumped high-power lasers, thin disk and waveguide designs as well as for ultrashort (ps/fs) pulse laser systems