Matthias Fechner

Crystalline Pr:SrAl 12 O 19 waveguide laser in the visible spectral region

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%.

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.

First ceramic laser in the visible spectral range

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.

Spectroscopy of upper energy levels in an Er 3+ -doped amorphous oxide

A spectroscopic study of the population mechanisms in erbium-doped amorphous aluminum oxide up to the 2H11/2/4S3/2 levels is performed. Via luminescence decay measurements, absorption and emission spectra, and a Judd-Ofelt analysis we determine luminescence lifetimes, radiative and non-radiative decay-rate constants, and branching ratios of the Er3+ inter-manifold 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 4I13/2 -> 4I9/2, 4I13/2 -> 4F9/2, and 4I11/2 -> 4F7/2 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 4S3/2 and 4F9/2 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 (4I13/2, 4I11/2) -> (4I15/2, 4F9/2).

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.

New Visible SrF2:Pr3+ Ceramic Laser at 639 nm

For the first time to our knowledge SrF2:Pr3+ fluoride ceramics was developed and visible 639 nm wavelength oscillations were obtained in diode pumped CW mode with slope efficiency above 9%.

Continuous-wave laser action of an Er:Sc 2 O 3 bulk crystal at 1.58 μm

This paper reports on a Er:Sc₂O₃ laser emitting a CW output power of 16.1 mW at 1583.7 nm for 890 mW of absorbed pump power, and with slope efficiency 4.2%. The Er:Sc₂O₃ of 4.75 mm length was grown by the Nacken-Kyropoulos method. Ti:Al₂O₃ laser emitting at 975 nm was used as the pump source.

First visible 639 nm SrF 2 :Pr 3+ ceramic laser

During the last years the interest for RE doped fluoride ceramics has arisen due to its improved thermo mechanical properties compared to analogous single crystal. Within short period of time number of fluoride nanoceramics were developed and rather efficient diode pumped lasing was demonstrated for LiF:F<inf>2</inf>⁻ [1], CaF<inf>2</inf>-SrF<inf>2</inf>:Yb³⁺ [2], CaF<inf>2</inf>:Yb³⁺ [3], SrF<inf>2</inf>:Nd³⁺ [4]. The common feature for all these ceramics was that laser oscillations in near IR spectral region 1–1.2 µm were obtained. It is well known that the optical losses in ceramic host material (scattering on grain boundaries, pores and inclusions) should strongly increase at shorter wavelengths. From this point of view the development and the investigation of laser ceramics which can oscillate at visible wavelengths is of great important. The recent success in visible light generation with Pr³⁺ ions [5] has become possible due to development of efficient blue GaInN diodes. In this work the results on oscillation properties of new Pr³⁺ doped SrF<inf>2</inf> ceramics are firstly presented.

Efficient in-band-pumped Er:Sc 2 O 3 -laser at 1.58 μm

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%.