# Infrared and visible scintillation of Ho$^{3+}$-doped YAG and YLF crystals

## TL;DR

This study investigates Ho$^{3+}$-doped YAG and YLF crystals' luminescence, revealing strong infrared emission and high infrared light yield, which are promising for low-energy event detection.

## Contribution

It demonstrates the high infrared light yield of Ho-doped crystals and explains the role of Ho$^{3+}$ energy levels in efficient infrared emission at low dopant levels.

## Key findings

- Infrared emission dominates over visible in Ho:YAG and Ho:YLF.
- Infrared light yield estimated at 40 photons/keV for 30 keV X-ray excitation.
- Efficient cross relaxation processes enable high infrared emission at low dopant concentrations.

## Abstract

In our effort to develop a new kind of detector for low-energy, low-rate energy deposition events we have investigated the cathodo- and radioluminescence of Ho:YAG and Ho:YLF single crystals in an extended wavelength range from $200\,$nm to $2200\,$nm. The emission spectra of both crystals show a much more intense emission in the infrared range than in the visible one. We estimate an infrared light yield of $40\,$photons/keV when exciting the crystals with X-rays of energy $\approx 30\,$keV. The main reason of this high value is due to the Ho$^{3+}$ ions energy levels scheme that allows efficient cross relaxation processes to occur even at low dopant concentration.