Cold Brownian motion in aqueous media via anti-Stokes photoluminescence

TL;DR

This paper demonstrates local cooling in aqueous media using laser-trapped YLF crystals, analyzing cold Brownian motion to quantify refrigeration effects enabled by anti-Stokes photoluminescence.

Contribution

It introduces a novel method to induce and measure local cooling in water via single-beam laser trapping and photoluminescence analysis of YLF crystals.

Findings

Achieved >21°C local cooling below ambient temperature.

Used cold Brownian motion analysis to quantify refrigeration.

Demonstrated potential for thermal management applications.

Abstract

Advances in cryogenic sciences have enabled several observations of new low-temperature physical phenomena including superconductivity, superfluidity, and Bose-Einstein condensates. Heat transfer is also critical in numerous applications including thermal management within integrated microelectronics and the regulation of plant-growth and development. Here we demonstrate that single-beam laser-trapping can be used to induce and quantify the local refrigeration of aqueous media through analysis of the cold Brownian dynamics of individual Yb3+-doped yttrium lithium fluoride (YLF) crystals in an inhomogeneous temperature field via forward light scattering and back-focal-plane interferometry. A tunable, NIR continuous-wave laser is used to optically trap individual YLF crystals with an irradiance on the order of 1 MW/cm2. Heat is transported out of the crystal lattice (across the solid / liquid interface) by anti-Stokes photoluminescence following upconversion of Yb3+ excited states mediated by optical-phonon absorption. The cold Brownian motion (CBM) analysis of individual YLF crystals indicates local cooling by >21 C below ambient conditions suggesting a range of potential future applications.