Harnessing Non-Boltzmann Steady States in Lanthanide Nanocrystals for Mid-Infrared Optoelectronics

TL;DR

This paper demonstrates that MIR irradiation can induce non-Boltzmann steady states in lanthanide nanocrystals, enabling sensitive, low-power MIR detection and imaging with new emission behaviors beyond thermal equilibrium constraints.

Contribution

It introduces a method to achieve non-thermal population control in lanthanide nanocrystals via MIR irradiation, enabling ultralow-power detection and room-temperature MIR imaging.

Findings

Achieved linear MIR detection from 6.8 to 8.6 micrometers.

Operation at ultralow excitation power of 10 microWatts.

Room-temperature MIR imaging with detection limits near 4 nW/μm².

Abstract

Converting mid-infrared (MIR) radiation to visible or near-infrared wavelengths is essential for imaging and sensing, yet achieving sensitive, low-power, and scalable detection remains challenging. Lanthanide nanocrystals provide an alternative through ratiometric luminescence but are typically constrained by Boltzmann statistics, which tie population distributions to lattice temperature and limit signal contrast. Here we show that MIR irradiation rebalances dissipative relaxation pathways, driving lanthanide emitters into a non-Boltzmann steady state that enables non-thermal control of population distributions. This allows emission behaviors inaccessible under thermal equilibrium. We exploit this regime to achieve linear MIR detection with respect to MIR power across 6.8 to 8.6 micrometers. The ratiometric response is intrinsically independent of the pump power, enabling operation at an ultralow excitation power of 10 uW, several orders of magnitude lower than conventional approaches. Using standard silicon photodetectors, we then demonstrate room-temperature MIR imaging with detection limits approaching 4 nW um-2. Our results establish lanthanide nanoparticles as an efficient platform for MIR conversion and sensing in nanophotonic systems.