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Lasing and spectroscopic properties of an LiY0.3Lu0.7F4:Pr3+ crystal grown by the Bridgman–Stockbarger method were investigated in detail. Absorption and luminescence spectra were recorded using polarized light. Lifetimes of excited states 3PJ were determined. Absorption and emission transition intensities were calculated according to f–f-transition intensity theory taking into account interconfiguration interaction. Stimulated emission transverse cross sections were determined using the Fuchtbauer–Ladenburg method. Pumping by an InGaN laser diode produced continuous-wave laser generation at 522.6 nm (3P1 → 3H5) in Pr-doped mixed fluoride crystals with a maximum output power of 0.38 W and a slope efficiency of 19%.

We present a compact diode-pumped Tm:KYW laser passively Q-switched with polycrystalline Cr:ZnSe saturable absorber. The laser operates at around 1910 nm and 1940 nm and produces pulses with duration as short as 10 ns and energy up to 40 μJ.

Ca9Nd(VO4)7 single crystal was grown by the Czochralski method in inert atmosphere. The crystal structure and chemical composition were studied. Polarized absorption and luminescence spectra were investigated in details. It was found that the Ca9Nd(VO4)7 crystals belongs to self-activated laser materials with a weak concentration quenching of luminescence. Judd-Ofelt analysis was performed. The emission cross-sections spectra for 4F3/2 → 4I9/2, 4I11/2, 4I13/2 transitions were determined. For the first time Raman spectra of the Ca9Nd(VO4)7 single crystal were recorded and interpreted.

Pure and Nd-doped Ca 10 Li(VO 4 ) 7 single crystals were grown by the Czochralski method. The structure of Ca 10 Li(VO 4 ) 7 single crystal was refined starting from a model of Ca 10 K(VO 4 ) 7 using the powder diffraction data collected at a laboratory high-resolution diffractometer. The defect structure of the single crystal was studied with the use of both, high-resolution diffraction using a laboratory instrument and X-ray topographic techniques employing synchrotron radiation at the Hasylab laboratory (Hamburg). Polarized absorption and luminescence spectra of Nd-doped Ca 10 Li(VO 4 ) 7 crystal were investigated in details. The laser oscillation was obtained under flash lamp pumping and the slope efficiency of 0.87% was achieved in the free-running mode. Preliminary examination of lasing properties points that Ca 10 Li(VO 4 ) 7 :Nd crystal can be a highly efficient solid state laser medium. Crystals of this kind are expected to be suitable for application as efficient non-linear optics materials.

We report on a comprehensive spectroscopic and laser characterization of monoclinic Yb,Tm:KLu(WO4)2 crystals. Stimulated-emission cross-section spectra corresponding to the 3F4 → 3H6 transition of Tm3+ ions are determined. The radiative lifetime of the 3F4 state of Tm3+ ions is 0.82 ms. The maximum Yb3+ → Tm3+ energy transfer efficiency is 83.9% for 5 at.% Yb – 8 at.% Tm doping. The fractional heat loading for Yb,Tm:KLu(WO4)2 is 0.45 ± 0.05. Using a hemispherical cavity and 5 at.% Yb – 6 at.% Tm doped crystal, a maximum CW power of 227 mW is achieved at 1.983–2.011 μm with a maximum slope efficiency η = 14%. In the microchip laser set-up, the highest slope efficiency is 20% for a 5 at.% Yb– 8 at.% Tm doped crystal with a maximum output power of 201 mW at 1.99–2.007 μm. Operation of Yb,Tm:KLu(WO4)2 as a vibronic laser emitting at 2.081–2.093 μm is also demonstrated.

Up to 15 mW of continuous wave deep red laser output at 702 nm are demonstrated using an Eu-(7.6 at.%):LiYF 4 crystal under pumping with a frequency doubled Ti:sapphire laser at 393.5 nm.

We report on yellow Tb3+:LiLuF 4 solid-state lasers. Under 2.1 W of 2ω-OPSL-pumping at 486.2 nm the laser delivers 0.45 W of cw output at a wavelength of 587.5 nm and a slope efficiency of 23 %.

Trivalent praseodymium doped materials are the most established gain media for solid-state lasers with direct visible emission. The progress in blue InGaN laser diodes (LD) and frequency doubled optically pumped semiconductor lasers (2ω-OPSL) enables efficient pumping of Pr3+-doped materials and efficient laser operation was realized in the cyan, green, orange, red and deep red parts of the optical spectrum [1]. The high gain and corresponding short upper state lifetime of several of these transitions should allow for comparably high pulse energies at high repetition rates e.g. in microchip configuration. This motivates a thorough investigation of the Q-switched operation of Pr:LiYF4 (Pr:YLF) and suitable modulators for this purpose. Previously, passively Q-switched diode-pumped Pr:YLF lasers were realized by using semiconductor saturable absorber mirrors [2] and Cr4+:YAG crystals [3]. Co2+: MALO crystals are well-known saturable absorbers for Q-switched eye-safe 1.5–1.6 μm lasers [4]. Here we report for the first time to our knowledge on a passively Q-switched Pr:YLF laser with Co2+:MgAl 2 O 4 (Co:MALO) as a saturable absorber.

An investigation of Tm-Ho energy transfer in Tm(5at.%),Ho(0.4at.%):KYW single crystal by two independent techiques was performed. Based on fluorescence dynamics measurements, energy transfer parameters Psub71/suband Psub28/subfor direct (Tm→Ho) and back (Ho→Tm) transfers, respectively, as well as equilibrium constant Θ were evaluated. The obtained results were supported by calculation of microscopic interaction parameters according to the Förster-Dexter theory for a dipole-dipole interaction. Diode-pumped continuous-wave operation of Tm,Ho:KYW microchip laser was demonstrated, for the first time to our knowledge. Maximum output power of 77 mW at 2070 nm was achieved at the fundamental TEMsub00/submode.

We present, to the best of our knowledge, the most efficient solid-state laser directly emitting in the yellow spectral range. Without any nonlinear conversion steps, a Tb3+:LiLuF4 laser operates at a wavelength of 587.5 nm with an output power of 0.5 W and a record-high slope efficiency of 25% with respect to the absorbed pump power at 486.2 nm. Despite the detrimental influence of 4f-excited state absorption, this efficiency is comparable to those obtained by complex nonlinear methods to generate yellow laser emission. Our approach, in combination with the progress in laser diodes at the required pump wavelength, paves the way for the development of cost-efficient, robust, and easily manageable diode-pumped yellow laser sources.

Eu3+-doped LiYF4 is reexamined as a laser material for the visible spectral region. Polarized absorption and emission cross sections as well as the fluorescence lifetime are determined. Branching ratios and radiative lifetime are calculated within the theory of 4f-4f transition intensities, which takes into account the influence of an excited configuration of the opposite parity 4fN-15d. Continuous-wave laser operation at 702 nm is demonstrated with a maximum output power of 15 mW and a slope efficiency of 4.6% under pumping with a frequency-doubled Ti:sapphire laser at 393.5 nm.

We report on a 2ω-OPSL-pumped passively Q-switched Pr3+:LiYF4 laser operating at the wavelengths of 523, 607, and 640 nm. For this, we utilized a Co2+-doped MgAl2O4 (MALO) crystal as a saturable absorber in the visible range for the first time, to the best of our knowledge. In the green spectral region, the pulse duration was 210 ns with a pulse energy of 3.6 μJ and a repetition rate of 125 kHz. The minimum pulse duration of 87 ns at the highest pulse energy of 8.6 μJ was obtained at a repetition rate of 110 kHz at 607 nm. The highest Q-switched average laser power of 1.4 W was obtained at an absorbed continuous-wave pump power of 3.3 W with a slope efficiency of 47% at 640 nm. Absorption saturation measurements with Co:MALO were performed, and ground and excited state absorption cross sections in the visible spectral range were determined.

Fluoride crystals are the most common host materials for visible lasers due to large energy band gap and low phonon energy. Among the rare-earth ions, the Pr3+ is very attractive ion for visible solid-state lasers. Efficient laser operation in Pr-doped crystals was obtained around 480 nm, 523 nm, 607 nm, 640 nm, 698 nm and 720 nm [1]. Mixed fluorides LiY x Lu x-1 F 4 crystals posses higher optical quality and require less expensive lutetium fluoride during growth in contrast to LiYF 4 and LiLuF 4 , respectively. Moreover, in the case of Ce3+ and Nd3+ ions, the mixed fluorides have higher segregation coefficient comparing to both LiYF 4 and LiLuF 4 crystals [2, 3]. The optimal cationic composition is x = 0.6–0.7.