Crytur (Czechia)

Miniature diode-pumped solid-state lasers operating in the 2.1µm atmospheric window are crucial for spectroscopic applications and free-space optical communication. We report on the spectroscopic and laser properties of a new Tm,Ho-codoped gadolinium-scandium-aluminium garnet (Tm,Ho:GSAG), a promising alternative to conventional hosts like YLF, YAG, and YAP. The mixed-garnet structure enables broad absorption and emission while maintaining the favorable thermo-mechanical properties of oxides. A Tm,Ho:GSAG crystal was grown by the µ-PD method, yielding a 3mm diameter, 20mm long rod. This technique enables the rapid and cost-effective preparation of small yet sufficiently high-quality laser-grade samples, facilitating extensive testing of different material compositions. A 3mm long sample with polished facets was prepared for laser testing. Spectroscopic characterization included absorption and emission spectra as well as fluorescence decay time measurements at 2.1µm. Laser experiments were conducted with a 782nm pulsed diode pump. In an untuned resonator, the laser achieved a slope efficiency of 25% with respect to absorbed pump power, with a peak emission at 2094nm. Wavelength tuning was implemented using an MgF₂ birefringent filter, covering a range from 2025nm to 2134nm, with maximum output power at 2122nm. These results demonstrate that Tm,Ho:GSAG is a promising gain medium for tunable diode-pumped mid-IR laser sources.

An 850nm interferometer was constructed to assess Er:YAG rod WFE. Our results, presented alongside active output energy characteristics, confirm minimal thermal lensing and overall high quality of the rods.

Internal stress is inevitably induced in the production of a solid-state gain medium. By polarimetry, we show an effective post-processing method of stress reduction and increase in the extinction ratio of the laser component.

Abstract Doping of luminescent materials by rare-earth (RE) ions is a common practice to achieve desired emission properties in a broad spectral range for large variety of applications including lasers, light emitting diodes, scintillators, quantum technologies, thermoluminescence dosimetry, biomedical/theranostic platforms, etc. As several rare-earths ions are frequently combined, it is subsequently difficult to effectively detect and control their homogeneous distribution within the host material. In this work, the simple, rapid, large scale and precise method of RE mapping using the commercial UV-Vis scanner is presented on the example of Gd/Ce-doped YAG/LuAG single crystals with inhomogeneous RE distribution. Moreover, the influence of RE distribution on the physical, optical and luminescent properties is discussed, with no observable qualitative effect on photoluminescent emission, luminescence decay kinetic and moreover to optical anisotropy. In contrary, RE rich areas exhibit significantly higher values of refractive index, Faraday rotation as well as optical absorption and observed parameter changes precisely followed the RE distribution borders identified by commercial scanner device. Presented method thus provides accurate information about the RE distribution in the material volume in high resolution (≈20 μm) compared to other techniques and thus offers simple, cheap and precise tool for the RE ions mapping in transparent materials.

This work presents innovative methods for visualizing inhomogeneities and stress distributions in Ti:Sa (titanium-doped sapphire) crystals, which are challenging to assess due to their birefringent nature. Two experimental approaches were developed: the first enables two-dimensional mapping of the Figure of Merit (FoM) and absorption at wavelengths of 532 nm, 780 nm, and 1550 nm, revealing variations in absorption across the crystal. The second experiment utilizes circularly polarized light and polarization imaging to detect internal stress and defects. The results demonstrate the successful visualization of lateral absorption, stress, and core features within the crystals, offering insights into their optical quality. These techniques provide new possibility for evaluation of laser materials, with significant implications for improving the manufacturing and selection processes of Ti:Sa crystals in advanced laser applications.

By means of the photoluminescence decay temperature dependence, the energy migration in the Gd-sublattice was investigated in a promising host material, (Gd,Y)AlO 3 , intended for Ce-doped bulk scintillators for gamma radiation detection.

The PbWO4 scintillation detectors for the Electron-Ion Collider Electron Endcap Electromagnetic Calorimeter (EEEMCAL) cannot use vacuum photomultipler tubes due to the high magnetic field environment. We are presenting a readout solution with a 4 x 4 SiPM array directly coupled to a preamplification and summing stage. A second amplification stage with variable gain and offset adjustments is also included in the compact electronics module. The integrated power supply feeds the signal processing chain and the adjustable bias control. The parameter settings are saved locally on a EEPROM and are adjustable via the integrated communication interface through USB or RS485. The design was optimized to maximize signal collection energy resolution, for fast timing and wide dynamic range while keeping a small footprint with low power consumption and heat dissipation. The output response is fast enough to meet the 100 – 200 ns digitization gate requirements for the detector. The electronics assembly requires no active cooling and includes a temperature sensor and a gain compensation of thermal variations which are important features for stable operation in large scale detector structures. A detector prototype was constructed with 20 mm x 20 mm x 200 mm PWO crystals affixed with individual SiPM array readouts and arranged in a 3 x 3 array. This detector was tested at the Thomas Jefferson National Accelerator Facility with 5GeV positrons. We will present the results of these detector characterization measurements.