Abstract:

As a novel cryocooler, a cryogenic optical refrigerator utilizing an anti-Stokes fluorescence process provides cooling power to a payload. Cryogenic optical refrigerators exhibit a compact structure, wide temperature range, and non-vibration. Hence, they are promising for applications in space technology, defense, and precision measurement. In this study, the principle prototype of a cryogenic optical refrigerator is introduced based on a cooling-grade Yb³⁺:LuLiF₄ crystal. Furthermore, the fluorescence escape coefficient and thermal loads of a heat link in an optical refrigerator is analyzed. Various heat link structures are designed, the fluorescence transmission process in these heat links is simulated using an optical simulation software, and the fluorescence escape coefficients of the different structures are determined based on the ray tracing results. The thermal loads of the heat link in the optical refrigerator are analyzed, and the thermal loads of the refrigerator with different angles of D-type bending structure heat links at low temperatures are calculated. The most suitable heat-link structure for cryogenic optical refrigerators is identified by optimizing the fluorescence escape coefficient and thermal loads of the heat link. The heat link design proposed in this study provides a good solution for high-efficiency cryogenic optical coolers.

Key words: laser cooling of solid materials, cryogenic optical coolers, thermal load, fluorescence analysis