Comparative spectroscopic studies of Ho: KPb2Cl5, Ho: KPb2Br5, and Ho: YAG for 2 µm laser cooling applications

Ei E. Brown; Uwe Hömmerich; Eric Kumi-Barimah; Althea Bluiett; Sudhir B. Trivedi

doi:10.1117/12.2077722

10 March 2015 Comparative spectroscopic studies of Ho: KPb₂Cl₅, Ho: KPb₂Br₂, and Ho: YAG for 2 μm laser cooling applications

Ei E. Brown, Uwe Hömmerich, Eric Kumi-Barimah, Althea Bluiett, Sudhir B. Trivedi

Author Affiliations +

Proceedings Volume 9380, Laser Refrigeration of Solids VIII; 93800O (2015) https://doi.org/10.1117/12.2077722
Event: SPIE OPTO, 2015, San Francisco, California, United States

Abstract

The infrared (IR) absorption and emission properties of Ho:KPC, Ho:KPB, and Ho:YAG were compared for possible applications in 2 µm laser cooling. Ho:KPC and Ho:KPB crystals were grown by vertical Bridgman technique using purified starting materials. A commercial Ho:YAG crystal was included in this study for comparison. Under resonant pumping at ~1.907 µm, the Ho-doped KPC/KPB crystals exhibited broad IR emission centered at ~2 µm based on the Ho³⁺ intra-4f transition ⁵I₇ → ⁵I₈. Under similar experimental conditions, Ho:YAG showed a narrow-structured emission band reflective of individual Stark levels. The average emission wavelength for Ho:YAG was determined to be ~2.03 µm. Initial heat loading/cooling experiments under ambient air were performed using a fiber laser operating at ~2.036 µm with an output power of 2 W. The Ho:KPC/KPB crystals exhibited small temperature increases of ~1.0 ºC. A significantly larger temperature increase of ~5 ºC was observed for Ho:YAG. IR transmission studies revealed the existence of OH impurities in the Ho-doped halides, which possibly lead to non-radiative decay channels.

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Ei E. Brown, Uwe Hömmerich, Eric Kumi-Barimah, Althea Bluiett, and Sudhir B. Trivedi "Comparative spectroscopic studies of Ho: KPb₂Cl₅, Ho: KPb₂Br₂, and Ho: YAG for 2 μm laser cooling applications", Proc. SPIE 9380, Laser Refrigeration of Solids VIII, 93800O (10 March 2015); https://doi.org/10.1117/12.2077722

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