Absolute Primary Nanothermometry Using Individual Stark Sublevels of Rare-Earth-doped Crystals

TL;DR

This paper introduces two optical methods for absolute primary thermometry using rare-earth-doped nanoparticles, leveraging internal energy levels and population dynamics for accurate temperature measurement without external references.

Contribution

It demonstrates novel primary thermometry techniques based on internal energy levels of rare-earth ions, enabling nanoscale temperature sensing with optical readout.

Findings

Successful experimental demonstration with Y$_2$O$_3$: Yb$^{3+}$/Er$^{3+}$ nanoparticles.

Use of Boltzmann distribution between Stark sublevels for temperature measurement.

Potential for single-ion level thermometry at the nanoscale.

Abstract

We present two independent optical methods for absolute primary thermometry using rare-earth-doped nanoparticles. Both approaches rely exclusively on the internal energy levels and population dynamics of the dopant ions, eliminating the need for external temperature references. We experimentally demonstrate the concepts by using Y$_2$O$_3$: Yb$^{3+}$/Er$^{3+}$ nanoparticles, exploiting Boltzmann distribution between individual Stark sublevels of the Er$^{3+}$ ions, emitting in the green spectral region ($\sim$550 nm) and in the near-infrared spectral region ($\sim$1600 nm). Our strategy establishes rare-earth-based luminescence thermometers as genuine absolute primary probes, conceptually comparable to Johnson noise and acoustic gas thermometers, but with the fundamental advantage of possibly being employed at the nanoscale, potentially down to the single-ion limit, with optical readout and over wide temperature ranges.