Rare-earth-doped photonic crystals for the development of solid-state optical cryocoolers

Angel J. Garcia-Adeva; Rolindes Balda; Joaquín Fernández

doi:10.1117/12.809418

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9 February 2009 Rare-earth-doped photonic crystals for the development of solid-state optical cryocoolers

Angel J. Garcia-Adeva, Rolindes Balda, Joaquín Fernández

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Proceedings Volume 7228, Laser Refrigeration of Solids II; 72280I (2009) https://doi.org/10.1117/12.809418
Event: SPIE OPTO: Integrated Optoelectronic Devices, 2009, San Jose, California, United States

Abstract

Optical cryocoolers made of luminescent solids are very promising for many applications in the fields of optical telecommunications, aerospace industry, bioimaging, and phototherapy. To the present day, researchers have employed a number of crystal and glass host materials doped with rare-earth ions (Yb³⁺, Tm³⁺, and Er³⁺) to yield anti-Stokes optical refrigeration. In these host materials, the attainable minimum temperature is limited by the average phonon energy of the lattice and the impurity concentration. However, recently Ruan and Kaviany have theoretically demonstrated that the cooling efficiency can be dramatically enhanced when the host material doped with rare-earth ions is ground into a powder made of sub-micron size grains. This is due to two facts: firstly, the phonon spectrum is modified due to finite size of the grains and, secondly, light localization effects increase the photon density, leading to an enhanced absorptivity. In the present work, we propose that using a photonic crystal doped with rare earth ions offers many advantages with regards to getting a larger cooling efficiency at room temperature when compared to standard bulk materials or nano-powders. Indeed, apart to analogous phenomena to the ones predicted in nano-crystalline powders, there is the possibility of directly controlling the spontaneous emission rate of the ions embedded in the structure and, also, the absorption rate in the Stokes side of the absorption band by adequately tuning the density of photonic states, thus obtaining a large improvement in the cooling efficiency.

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Angel J. Garcia-Adeva, Rolindes Balda, and Joaquín Fernández "Rare-earth-doped photonic crystals for the development of solid-state optical cryocoolers", Proc. SPIE 7228, Laser Refrigeration of Solids II, 72280I (9 February 2009); https://doi.org/10.1117/12.809418

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