Daniel-Timo Marzahl

High-power red, orange, and green Pr 3+ :LiYF 4 lasers

Laser experiments with Pr(3+):LiYF4 under excitation with a frequency doubled optically pumped semiconductor laser emitting 5 W at 479 nm were performed at seven different laser wavelengths of 523, 546, 604, 607, 640, 698, and 720 nm. At all these wavelengths the output power exceeded 1 W. The best performance at 523 nm with an output power of 2.9 W at a slope efficiency of 72% and an optical-to-optical efficiency of 67% with respect to the incident pump power represents the highest efficiency ever reported for a praseodymium-doped laser material.

Diode pumped laser operation and spectroscopy of Pr 3+ :LaF 3

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 laser operation of Pr 3+ , Mg 2+ :SrAl 12 O 19

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.

Wide wavelength tunability and green laser operation of diode-pumped Pr 3+ :KY 3 F 10

We report on wide spectral tunability of a quasi-continuous wave Pr(3+):KY(3)F(10) laser under InGaN laser diode excitation at 445 nm. The total tuning range exceeded 100 nm in the visible spectral range on several intervals between 521 nm and 737 nm. The broadest continuously tunable region of almost 50 nm extended from 688 nm to 737 nm. Furthermore we present what is to the best of our knowledge the first demonstration of continuous wave laser operation in Pr(3+):KY(3)F(10) on three transitions in the green spectral region. The highest output power of 121 mW was achieved at an emission wavelength of 554 nm with a slope efficiency of 27%.

Efficient visible laser operation of Pr,Mg:SrAl 12 O 19 channel waveguides

We report the fabrication and visible laser operation of Pr,Mg:SrAl12O19 waveguides. Waveguiding structures were created by focusing the radiation of a femtosecond Ti:sapphire laser into bulk material. Guiding losses were determined to be as low as 0.12 dB cm(-1) at 632.8 nm. By employing a frequency-doubled optically pumped semiconductor laser, waveguide laser operation was realized at wavelengths of 525.3, 644.0, and 724.9 nm with output powers as high as 36, 1065, and 504 mW, respectively. To the best of our knowledge this is the first demonstration of green laser operation in a Pr(3+)-doped crystalline waveguide laser.

Spectroscopy and laser operation of Sm(3+)-doped lithium lutetium tetrafluoride (LiLuF(4)) and strontium hexaaluminate (SrAl(12)O(19)).

We report on laser operation in the orange and red spectral range in samarium (Sm(3+))-doped fluoride and oxide crystals at 300 K. Sm(3+)-doped LiLuF(4) (LLF) and SrAl(12)O(19) (SRA) crystals were grown by the Czochralski-technique and utilized for spectroscopic investigations and laser experiments. The spin-forbidden transitions of Sm(3+)exhibit low cross sections the order of 10(-21) cm(2), but high radiative upper state lifetimes of several ms in both crystal systems. Under 2ω-OPSL-pumping at 480 nm, orange laser operation was achieved with Sm:LLF and Sm,Mg:SRA at lasing wavelengths of 606 nm and 593 nm, respectively. Furthermore laser oscillation was demonstrated at 648 nm in the red and 703 nm in the deep red spectral range with Sm:LLF and Sm,Mg:SRA, respectively. Output power levels of several 10 mW were obtained at slope efficiencies of up to 15 %. Most of the realized lasers were operating in a strongly modulated or even self-pulsing regime.

Prospects of Holmium-doped fluorides as gain media for visible solid state lasers

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 5F4,5S2 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 μs. To the best of our knowledge this constitutes the first green laser emission of a Ho3+-doped crystal at room temperature.

Thin-disk laser operation of Pr 3+ ,Mg 2+ :SrAl 12 O 19

We present first results in applying the thin-disk concept to lasers directly emitting in the visible spectral range. The pump light was provided by 24 InGaN laser diodes emitting 1 W each at 444 nm, which were coupled into a 200 μm fiber. A 300 μm thin Pr3+,Mg2+:SrAl12O19 crystal served as gain medium. In continuous-wave operation an output power of 0.88 W and a slope efficiency of 12% with respect to the absorbed pump power were achieved at an emission wavelength of 643.5 nm. Modulating the pump source at a duty cycle of 10% yielded an instantaneous output power of 1.67 W, corresponding to a slope efficiency of 26%.

Performance and wavelength tuning of green emitting terbium lasers

Wavelength tuning experiments in the green spectral range applying Tb³⁺-doped LiLuF₄ and Tb³⁺/Na⁺-codoped CaF₂ single crystals are presented. While in the former case almost 100 mW could be obtained throughout a total range of 7 nm, the inhomogeneously broadened emission features of Tb³⁺ in the CaF₂-matrix allowed for a continuous tuning range exceeding 10 nm. For initial characterization, free running continuous wave laser experiments using Tb³⁺-doped LiLuF₄, Na⁺:CaF₂, and stoichiometric TbF₃ crystals were carried out resulting in efficient continuous wave laser operation in the green spectral region. The density of active centers in TbF₃ is among the highest that can be obtained in solid state gain materials. Nevertheless, a slope efficiency as high as 32% was obtained from this crystal. High Tb³⁺-densities are essential to compensate for the adherent low absorption cross sections at useful pump-wavelengths.

Novel rare earth solid state lasers with emission wavelengths in the visible spectral range

Recent developments in blue emitting laser sources, in particular InGaN laser diodes (InGaN-LDs) and frequency doubled optically pumped semiconductor lasers (2ω-OPSLs), opened access both to visible laser operation with unprecedented efficiencies in the well-established praseodymium doped laser systems [1, 2] as well as to the realization of new rare earth based solid state laser systems with emission wavelengths in the visible spectral range [3].