We report, for the first time to our knowledge, diode-pumped cw laser oscillation of ${\mathrm{Pr}}^{3+}:{\mathrm{LiYF}}_4$ in the red spectral range. The pump power is provided by a GaN laser diode emitting a maximum output power of 25 mW at a wavelength of approximately 442 nm. The ${\mathrm{Pr}}^{3+}$ laser emits 1.8 mW of output power at a 639.7-nm wavelength. Threshold pump power and slope efficiency in a nonoptimized setup are determined to be 5.5 mW and 24%, respectively.

The letter reports on upconverted orange (607.5 nm, P03→3H6) and red (638.7 nm, P03→3F2) laser oscillation at room temperature observed in Pr3+, Yb3+:BaY2F8 under excitation at 822 or 841 nm at 300 K. The upconversion mechanism that populates the emitting level is an avalanche excitation mechanism. Output powers up to 55 mW and slope efficiencies up to 27% were demonstrated at 607.5 nm. At 638.7 nm, the maximum output power was 26 mW with a slope efficiency of about 13.5%.

We report on the spectroscopic investigation of ${\mathrm{Pr}}^{3+}$-doped binary, ternary, and quaternary fluoride compounds exhibiting photon cascade emission. Under vacuum-ultraviolet synchrotron excitation at wavelengths below 200 nm in the $4f5d$ bands of the ${\mathrm{Pr}}^{3+}$ ion the emission spectra show intraconfigurational $4f\text{−}4f$ transitions originating from the ${}^{1}S_0$ and ${}^{3}P_0$ multiplets. In the ternary and quaternary compounds investigated, i.e., Ca-, Sr-, Ba-, and Rb-fluorides, broadband emission due to transitions from the $4f5d$ level of ${\mathrm{Pr}}^{3+}$ are also observed. The different types of emission transitions observed in the compounds investigated were analyzed in detail. The internal quantum efficiency for the visible spectral range (390 nm–750 nm), ${\eta }_{\mathrm{vis}}$, is determined with the help of the Judd-Ofelt theory and the branching ratios of the ${}^{1}S_0$ emission transitions. The dependence of this quantum efficiency ${\eta }_{\mathrm{vis}}$ from the ionic radius of the second cation $\left(R_{2\mathrm{nd}}\right)$, the effective ligand distance, and the coordination number is investigated.

Optical coherence tomography (OCT) is a noninvasive, high-resolution, high-potential imaging method that has recently been introduced into medical investigations. A growing number of studies have used this technique in the field of gastroenterology in order to assist classical analyses. Lately, 3D-imaging and Doppler capabilities have been developed in different configurations, which make this type of investigation more attractive. This paper reviews the principles and characteristics of OCT and Doppler-OCT in connection with analyses of the detection of normal and pathological structures, and with the possibility to investigate angiogenesis in the gastrointestinal tract.