Preparation, spectroscopic characterization and energy transfer investigation of iron-chromium diffusion co-doped ZnSe for mid-IR laser applications

•Cr,Fe:ZnSe polycrystalline was first prepared by controlled thermal diffusion method.•The spectroscopic characterization and energy transfer mechanism of Cr,Fe:ZnSe were reported.•The transfer rate is much faster than the photoluminescence decay.•Laser operation at 3.7–4.5 μm via Cr2+ → Fe2+ energy transfer is feasible.

The spectroscopic characterization and energy transfer mechanism of iron-chromium co-doped ZnSe polycrystalline (Cr,Fe:ZnSe) were reported with dimension of 15 mm × 15 mm × 2 mm obtained by controlled post-growth thermal diffusion method. The infrared absorption is characterized by a strong broad-band centered at 1770 nm which can be attributed to the only spin-allowed transition 5T2 → 5E within the 3d4 shell of Cr2+ ions. Photoluminescence spectrum shows a relatively strong broad emission band centered at 4.1 μm with a width of 0.8 μm (FWHM) under 1770 nm excitation at room temperature and reveals effective Cr2+ → Fe2+ energy transfer process. Room temperature photoluminescence decay about 8 μs was measured. All the results indicate that Cr,Fe:ZnSe could achieve laser operation at 3.7–4.5 μm via Cr2+ → Fe2+ energy transfer using a more convenient laser pump source in the near IR region.