Optical materials

A low-wavelength host absorption edge of cesium-lithium borate CsLiB$_6$O$_{10}$

I. N. Ogorodnikov

Ural Federal University named after the First President of Russia B. N. Yeltsin, 620002 Yekaterinburg, Russia

Abstract: We have carried out an experimental study of the VUV edge of the optical host absorption of cesium-lithium borate crystals CsLiB$_6$O$_{10}$ (CLBO). The transmission ($T$ = 293 K) and absorption ($T$ = 80, 293 K) spectra were studied, the short-wavelength edge of the transparency band (cutoff wavelength) and the energy position of the edge fundamental absorption at which the absorption coefficient $k$ = 50 cm$^{-1}$ were determined. The absorption edge temperature shift coefficient -5.5 $\cdot$ 10$^{-4}$ eV/K was determined. Based on low-temperature reflection spectra ($T$ = 10 K, $\theta$ = 17$^\circ$, $E$ = 7–30 eV) the Kramers–Kronig method was used to calculate the spectra of optical constants: refractive index $(n)$ and absorption index $(k)$, real $(\varepsilon_1)$ and imaginary $(\varepsilon_2)$ parts of the complex permittivity , as well as the absorption coefficient $\mu$. The lowest energy peak, due to electronic transitions from the top of the valence band to the states of the bottom of the conduction band, was studied in the $(\varepsilon_2)(E)$ spectrum, the thresholds for interband transitions were determined $E_g$ = 7.95 eV. The origin of the fundamental absorption edge of cesium-lithium borate is discussed.

Keywords: cesium-lithium borate CsLiB$_6$O$_{10}$ (CLBO), host absorption edge, optical properties.

Received: 10.08.2022
Revised: 11.10.2022
Accepted: 22.10.2022

DOI: 10.21883/OS.2022.12.54096.4011-22

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