Fig. 1. Hyperfine energy level structure of Y₂SiO₅ crystal doped with Pr³⁺ ions

Fig. 2. Linear absorption Im(K) as a function of frequency of probe light, and the experimental data coming from Ref. [15]

Fig. 3. Structure and energy level diagrams of Pr³⁺∶Y₂SiO₅ crystal sandwich waveguide. (a) Schematic of sandwich waveguide structure; (b) hyperfine energy level structure of Pr³⁺

Fig. 4. Comparison of linear absorption relations in free-space system and confined sandwich waveguide system