Luminescence properties of CdF2 single crystals co-doped with Er3+ and Y3+ ions.

The luminescence properties of erbium and yttrium co-doped cadmium difluoride with three different concentrations of yttrium were investigated. First, we synthesized single crystal samples with good optical quality using the Bridgman technique. From the optical absorption spectra, recorded at room temperature, both in the ultraviolet-visible and infrared spectral ranges, Judd-Ofelt analysis was performed based on yttrium concentrations to predict the radiative properties of Er3+ luminescent ions. For the 10% optimum concentration of yttrium, a detailed photoluminescence investigation was carried out. We mainly explored green, red, and near-infrared fluorescence under different excitation wavelengths and presented their highlight spectroscopic characteristics. The desired transitions had relatively high emission cross-sections both under visible and near-infrared excitation. Optical gain followed a similar trend. Furthermore, the dynamic fluorescence study showed a significant increase in the measured lifetime under an 800 nm infrared excitation. The upconversion process under an 800 nm excitation produced quantum efficiency greater than 100% due to the contribution of more than one energy transfer mechanism.

Operation of a fiber-coupled laser-cooler down to cryogenic temperatures.

We report on the optical cooling of a 7.5%Yb:LiYF4 crystal down to 125 K in a multi-pass Herriott absorption cell, coupled via a single mode polarization maintaining optical fiber to the laser source. This configuration, never exploited before, is more practical for potential applications, in particular for spaceborne cryogenics setups. Moreover, the temperature reached is exactly the one needed in many setup embarked in small and medium satellites. We evaluate the heat load on the crystal at the minimum attainable temperature, which is comparable to state of the art systems.

Operation of a fiber-coupled laser-cooler down to cryogenic temperatures: publisher's note.

This publisher's note contains a correction to [Opt. Express30, 12929 (2022)10.1364/OE.448930].

Deep Red Tunability and Output Power Performances of Visible Laser Emission in a Pr:Ba(Y1-xLux)2F8 Single Crystal.

The demand for tunable visible laser sources with high power and high beam quality, for application ranging from metrology to remote sensing, is constantly increasing. In this work, we report on the details of crystal growth, via the Czochralski method, and laser characterization of a Pr-doped Ba(Y1-xLux)2F8 (BYLF) single crystal, which is a promising candidate for fulfilling these requirements, both in terms of tunability and high-power capabilities. We measured for the first time the laser tunability curve in the deep red region obtaining a continuous range of 17 nm. The laser emission of the three main Pr3+ lines in the visible (orange, red, and deep red) was tested under increased pump power with respect to previous studies on this material, demonstrating output powers of more than 360 mW and no thermal rolloff, up to 1.9 W of absorbed power.

First demonstration of optical refrigeration efficiency greater than 4% at room temperature.

In this work, we present the cooling efficiency of a LiYF4 (lithium yttrium fluoride,YLF) sample co-doped with 10at.% ytterbium (Yb3+) and 0.0040at.% thulium (Tm3+). For the first time at room temperature, the cooling efficiency of a sample overcomes the 4%-barrier, and it must be compared with the best values reported in literature, about 3%, obtained with a YLF:10at.%Yb sample. We also investigated the frequency behaviour of energy transfer mechanisms between Yb and Tm ions in order to have a better understanding of the contribution of phonons to the cooling cycle. These mechanisms can explain the cooling efficiency enhancement in the co-doped system.