High-resolution luminescence spectroscopy of CaWO$_4$:Ho$^{3+}$: Sensitive detection of internal strains, temperature, and magnetic field

TL;DR

This study demonstrates high-resolution luminescence spectroscopy of CaWO4:Ho3+ revealing hyperfine structure, sensitive detection of internal strains, magnetic fields, and temperature variations, with potential for advanced sensing applications.

Contribution

First observation of hyperfine structure in CaWO4:Ho3+ luminescence spectra and development of a sensitive luminescence-based thermometer.

Findings

Hyperfine structure observed in luminescence spectra for the first time.

Magnetic field variations as small as tenths of mT detectable.

PL spectra more sensitive to lattice strains than absorption spectra.

Abstract

We carried out high-resolution (0.02 cm-1) measurements of the photoluminescence (PL) spectra of CaWO4:Ho3+, including in magnetic field, and performed spectra modeling. Well-resolved hyperfine structure was observed in the luminescence spectra of CaWO4:Ho3+ for the first time. Energies of several crystal-field levels were specified, g-factors were determined. Variations of a magnetic field as small as several tenths of mT can be detected from the PL spectra. We show that the PL spectra are much more sensitive to lattice strains in CaWO4:Ho3+ than the absorption spectra. The spectra were simulated using refined crystal-field parameters and taking into account both hyperfine and deformation interactions. Here, we used the previously obtained distribution function of random strains induced by point lattice defects in an elastically anisotropic CaWO4 crystal. A luminescence thermometer for temperatures around 20 K based on CaWO4:Ho3+ is suggested.