Ultraviolet optical properties of CaSrF2 crystal grown by the cone die Czochralski method

• Published in: Journal of crystal growth 2025-01, Vol.649, p.127949, Article 127949
• Main Authors: Akabe, Yugo, Enomoto, Kotaro, Shinohara, Keito, Raduban, Marilou, Shimizu, Toshihiko, Sarukura, Nobuhiko, Okumura, Rui, Kodama, Ryosuke, Takahashi, Kazuya, Kawamata, Toru, Sugiyama, Kazumasa, Fukuda, Tsuguo
• Format: Article
• Language: English
• ISSN: 0022-0248
• DOI: 10.1016/j.jcrysgro.2024.127949

•Large calcium strontium fluoride single crystal grown by cone die Czochralski method.•Refractive index measurement in the UV region using a double prism system.•Potential applications: ultraviolet and vacuum ultraviolet optics. Fluoride crystals with extremely wide band gaps are ideal optical materials in the UV wavelength range. Large 4-inch diameter calcium strontium fluoride (Ca0.582Sr0.418F2) single crystal was grown using the Czochralski method with a Cone-shape Die (CD-CZ). The refractive index and relative transmittance of the crystal was evaluated by cutting it into a triangular prism and polished. The direct measurement of the refractive index and relative transmittance was done by using a spectrograph to image the refraction of light as it passes through a dual prism set-up consisting of a SQ prism as reference and either CaF2 or Ca0.582Sr0.418F2 as the material under evaluation. Characterization results showed that Ca0.582Sr0.418F2 has excellent refractive index dispersion and transmittance in the UV region, confirming the applicability of the dual prism with spectrograph setup to measurements of the refractive index and relative transmittance in the UV region.