In this paper we report on the suitability of Ho3+:LiLuF4 and Ho3+:LaF3 as active media for solid state lasers emitting in the green spectral region. The ground state absorption spectra were measured and employed to calculate the emission cross section spectra via the reciprocity method. These allowed to derive the gain characteristics for various inversion ratios. The decay dynamics of the F-5(4),S-5(2) multiplet, which would act as upper laser level, were investigated to estimate the quantum efficiency. Measurements of the excited state absorption were conducted which showed that stimulated emission is the dominating effect around 550 nm. Laser operation was demonstrated in the green spectral region by employing Ho3+: LaF3 as gain medium. Laser oscillation occurred in a self-pulsed regime with a maximum average output power of 7.7 mW, a repetition rate of 5.3 kHz, and a pulse duration of 1.6 mu s. To the best of our knowledge this constitutes the first green laser emission of a Ho3+-doped crystal at room temperature. (C) 2014 Optical Society of America

We report on diode-pumped laser operation of Pr3+,Mg2+:SrAl12O19 at lasing wavelengths of λ L = 724.4 nm, λ L = 643.5 nm, and λ L = 622.8 nm. Furthermore, the laser threshold could be reached in the green spectral range. By pumping the crystal longitudinally from each side with two polarization beam combined InGaN laser diodes, a total pump power of ≈4 W was available. In the deep red spectral range, a maximum output power of 564 mW was achieved with a maximum slope efficiency of 50 % with respect to the absorbed pump power. The maximum possible internal losses were estimated to ≈1 %. Beam quality factors M 2 were in the range of 1.2–1.5.

A spectroscopic study of the population mechanisms in erbium-doped amorphous aluminum oxide up to the H-2(11/2)/S-4(3/2) levels is performed. Via luminescence decay measurements, absorption and emission spectra, and a Judd-Ofelt analysis, we determine luminescence lifetimes, radiative and nonradiative decay-rate constants, and branching ratios of the Er3+ intermanifold transitions. With a continuous-wave pump-probe technique, the excited-state absorption (ESA) spectrum is recorded between 900 and 1800 nm and the cross sections of the ESA transitions I-4(13/2) -> I-4(9/2), I-4(13/2) -> F-4(9/2), and I-4(11/2) -> F-4(7/2) are determined. The microparameters and efficiencies of resonant and phonon-assisted energy-migration and energy-transfer upconversion (ETU) processes among Er3+ ions occurring from the first and second excited states are evaluated. From the ratio of the S-4(3/2) and F-4(9/2) luminescence intensities as a function of Er3+ concentration, we prove the existence and quantify the macroscopic ETU coefficient of the two-phonon-assisted ETU process (I-4(13/2,) I-4(11/2)) -> (I-4(15/2,) F-4(9/2)). (c) 2013 Optical Society of America

In this Letter, we report on laser operation of Pr3+,Mg2+:SrAl12O19 pumped by a frequency-doubled optically pumped semiconductor laser. By employing a V-type cavity, we demonstrate cw laser operation at room temperature in the green spectral range in a doped oxide host for the first time to the best of our knowledge. Furthermore, efficient laser operation was realized in the orange, red, and deep red spectral range with output powers exceeding 1.1 W at emission wavelengths of 643.6 and 724.4 nm.

We report on crystal growth, spectroscopic investigations, crystal field tuning, and laser experiments of neodymium doped mixed sesquioxides (Lu1−x Sc x )2O3. Crystals were grown by the Nacken–Kyropoulos and the Heat-Exchanger method. Emission spectra for several mixing ratios are presented. Cw laser experiments were carried out with a 0.35 at.%-doped Nd:Lu1.82Sc0.18O3 crystal by using a Ti:sapphire laser as pump source, achieving a maximum slope efficiency of 47 % with respect to the absorbed pump power and a maximum output power of 356 mW at a wavelength of 952.7 nm. To the best of our knowledge, this represents the first continous wave (cw) laser operation of a Nd-doped mixed sesquioxide.

We report on the first results of diode pumped laser operation of Pr3+:LaF3 in a quasi continuous wave (qcw) mode with average output powers of up to 80.0 mW (≈ 161.3 mW qcw) and a maximum slope efficiency of 37% at 719.8 nm. Furthermore it was possible to operate the laser at 537.1 nm and 635.4 nm and to tune the emission wavelength from 609 nm to 623 nm. The pump source was an InGaN laser diode with a maximum output power of 1 W at a central emission wavelength of 442 nm.

Efficient cw laser action of a Nd-doped mixed sesquioxide is shown at 952.7 nm. The maximum output power and slope efficiency of the quasi three-level-transition 4F3/2-4I9/2 are 356 mW and 49 % respectively.

Within cerium doped CaSc2O4 single crystals a ligand to metal Ce4+ ➔ Ce3+ charge transfer absorption band is identified. Crystal growth and its influence on the incorporation of different charged Cerium ions are discussed.

Polarization dependent ground state absorption, excited state absorption and emission cross sections of Pr, Mg:SrAl12O19 are determined in the visible and ultraviolet spectral region. It is shown that excited state absorption to the 4f5d configuration does neither occur on the pump wavelength in the blue region nor on any of the visible laser transitions. Efficient laser action at 643.5 nm is demonstrated with slope efficiencies of up to 47% with respect to the absorbed pump power. Output powers up to 75 mW are achieved by pumping with an InGaN laser diode at 444 nm.

Results for new fluoride ceramics doped with praseodymium ions in which, to the best of our knowledge, for the first time a laser in the visible spectral range (639 nm) was obtained under GaInN blue laser diode optical pumping. In our experiments, CW operation with lasing threshold less than 100 mW of absorbed pump power and slope efficiency exceeding 9% was realized.

We fabricated waveguides in Pr:SrAl(12)O(19) crystals by direct femtosecond laser writing. The propagation losses were calculated to be as low as 0.16 dB/cm at a wavelength of 633 nm. Laser oscillation in a diode-pumped waveguide at a wavelength of 643.5 nm was realized. The output power of the waveguide laser was 28.1 mW at a slope efficiency of 8%.

Efficient cw laser action of a Nd-doped mixed sesquioxide is shown at 952.7 nm. The maximum output power and slope efficiency of the quasi three-level-transition 4F3/2 → 4I9/2 are 356 mW and 49 %, respectively.

We report a fundamental spectroscopic research of Ho:Lu 2 O 3 in order to evaluate the laser potential of the green transition. Crystals were grown by the heat-exchanger and Nacken-Kyropoulos method and the spectroscopic investigations include temperature dependent lifetime measurements as well as the determination of the ground state absorption, the excited state absorption, and the emission cross sections.

We report the first diode-pumped laser oscillation of Pr:BaY2F8 in the green spectral range, related crystal growth and basic spectroscopic properties. Furthermore, recent results of experiments with Pr:LiYF4, showing efficient green laser action, are presented.

The use of Yb3+ as a sensitizer for Er3+ doped laser materials is a common technique because of the high Yb3+ absorption cross sections. Energy transfer processes from Yb3+ to Er3+ in Sc2O3 are studied by two different methods. Transfer parameters describing the interactions between Er3+ and Yb3+ ions are obtained on the one hand from the ratio of emitted photons around 1.55μm by Er3+ ions and around 1μm by Yb3+ ions at cw excitation of Yb3+, on the other hand by lifetime measurements of Yb3+ ions in the codoped samples. Laser experiments are performed to study the suitability of Er3+,Yb3+:Sc2O3 as a laser material. Comparisons with energy transfer in Er3+,Yb3+:glass are made.

We present an efficient in-band-pumped Er(0.2 at.%):Sc2O3-laser at 1581 nm with a maximum output power of 0.95 W and a maximum slope efficiency of 31%.

We present an efficient in-band-pumped Er(0.2 at%):Sc(2)O(3)-laser at 1581 nm with a maximum output power of 0.95 W and a maximum slope efficiency of 31%. (C) 2008 Optical Society of America

This work presents a clear improvement of the crystal growth by the heat exchanger method (HEM) leading to longer fluorescence lifetime and higher laser efficiency of this material. Polycrystalline boules of 40 mm diameter and 25 mm length with monocrystalline regions of up 5 cm3 have been grown with 6N LU2O3 and 5N Yb2O3 in a 40 mm diameter high purity Re-crucible under H2/N2 atmosphere. The fluorescence lifetime of the obtained crystals has been determined with the pinhole-method to exclude radiation trapping. In contrast to previous growth experiments no concentration quenching occurred up to the highest grown doping concentration of 5%. Additionally, the ratio of parasitic visible green fluorescence of Er3+ to the infrared emission was reduced by a factor of 7 compared to the crystals grown in previous experiments, which is a further indicator for less rare-earth impurities. An increase of more than 30% in cw laser efficiency of Yb:Lu2O3 promises likewise increased efficiencies in thin disk laser experiments planned for the near future.