Method for the determination of dopant concentrations of luminescent ions.

We report on a new method for determining dopant ion concentrations in laser materials. This method is based on optical absorption spectroscopy. In contrast to other methods used to measure the dopant concentration that are based on absorption measurements, this method does not require the knowledge of the absorption cross sections. An advantage of this method compared to the micro probe analysis is that only concentrations of dopant ions of a certain valency, which are luminescent, are detected. The method is sensitive especially for small doping concentrations of ions with high absorption cross sections. Another application of this method is the determination of the ratio between luminescent dopant ions to the total number of dopant ions in the case that not all dopant ions are on crystal sites that allow for optical transitions.

Correction of reabsorption artifacts in fluorescence spectra by the pinhole method.

Reabsorption of spontaneously emitted photons by optically active ions in a laser material can significantly affect the measured emission spectra. A measurement technique to suppress reabsorpion artifacts in fluorescence spectra is reported. A theoretical description of the method as well as experimental results are presented. In combination with another version of the pinhole method for the determination of reabsorption-free fluorescence lifetimes, this technique allows one to suppress the influence of reabsorption artifacts in emission cross sections calculated by the Füchtbauer-Ladenburg equation.

Monocrystalline Yb(3+):(Gd,Lu)(2)O(3) channel waveguide laser at 976.8 nm.

We report on a Yb(3+)-doped sesquioxide waveguide laser based on a lattice-matched Yb(3+)(3%):(Gd,Lu)(2)O(3) film that has been epitaxially grown on Y(2)O(3) using pulsed laser deposition. Rib-channel waveguides have been structured by reactive ion etching. Laser emission at 976.8 nm was observed under pumping with a Ti(3+):Al(2)O(3) laser at 905 nm. A laser threshold of 17 mW and a slope efficiency of 6.7% have been achieved with respect to input power. For an incident pump power of 200 mW, a maximum output power of 12 mW could be realized.

Low threshold monocrystalline Nd:(Gd, Lu)2O3 channel waveguide laser.

We report the first waveguide laser based on a rare-earth-doped sesquioxide. A 2 microm thick lattice matched Nd(0.5%):(Gd, Lu)(2)O(3) film with a nearly atomically flat surface has been epitaxially grown on a Y(2)O(3) substrate, using pulsed laser deposition. The film has been structured with reactive ion etching and a rib channel waveguide laser has been realized. Laser radiation at 1075 nm and 1079 nm has been observed under 820-nm pumping. The laser possesses a threshold power of about 0.8 mW and a preliminary slope efficiency of 0.5% versus incident pump power. A maximum output power of 1.8 mW has been obtained for 370 mW incident pump power.

Model for the calculation of radiation trapping and description of the pinhole method.

Radiation trapping is a well-known process that results in the lengthening of observed fluorescence lifetimes in laser materials with significant overlap in their emission and absorption spectra. The pinhole method is a measurement technique that allows the intrinsic fluorescence lifetime of an excited state to be determined in a nondestructive manner. A theoretical description of this method is proposed. A model is developed that identifies the lifetime extrapolated to a zero radius pinhole as the intrinsic fluorescence lifetime. The application of this method to bulk materials and thin discs is discussed.