A Sm 2+ -containing Mg 0.5 Sr 0.5 FCl 0.5 Br 0.5 mixed crystal was synthesized by firing at 1,100°C 2 hours in a reducing stream of hydrogen gas and examined with an X-ray diffractometer for the crystalline structure. We measured the optical properties of Sm 2+ -ion and observed the efficiencies of persistent spectral hole burning depend on hole burning methods at 90 K and 300 K. At 90 K, PSHB was made much more efficiently by using the photon-gated (two color) spectral hole burning process compared to the one color hole burning process, while the one color hole burning process is much more efficient at 300 K.