# Probing the Hydrogen Enhanced Near-Field Emission of ITO without a Vacuum-Gap

## TL;DR

This study demonstrates that the thermal near-field of ITO can be effectively probed and extracted into the far-field without a vacuum-gap by using waveguides to facilitate photon tunneling, revealing enhanced plasmonic activity.

## Contribution

It introduces a novel method to probe and extract the thermal near-field of ITO without requiring a vacuum-gap, utilizing waveguides for photon tunneling.

## Key findings

- Waveguides enable efficient near-field to far-field photon tunneling.
- Thermal near-field of ITO can be observed without a vacuum-gap.
- Enhanced plasmonic activity at 1500nm wavelength in ITO was confirmed.

## Abstract

Thermal fluctuations of charged particles, fluctuations akin to Brownian motion, can excite optical surface-states leading to the concept of the thermal near-field, which is a highly localized, and, therefore, evanescent optical density of states that exist at distances much less than the thermal emission wavelength. By tunneling the surface charge emitted photons into nearby waveguides, the thermally excitable near-field optical density of states can be enhanced, engineered, and efficiently extracted to the far-field for observation. With this technique, the plasmonic thermal near-field of a 10nm thick ITO film, known to have plasmonic activity in the 1500nm wavelength region, was probed under external illumination and by thermal excitation at 873K. The results confirm that waveguides provide a large density of optical channels with spatial overlap and k-vector matching to facilitate plasmon de-excitation in the near-field through photon tunneling for extraction into the far-field. Furthermore, it is shown that the thermal near-field can be observed without the introduction of a vacuum-gap, a feature unique to this particular method.

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Source: https://tomesphere.com/paper/1704.01102