# Spatial Sampling of Terahertz Fields with Sub-wavelength Accuracy via Probe Beam Encoding

## TL;DR

This paper presents a simple, non-invasive method for spatially sampling terahertz fields with sub-wavelength accuracy using probe beam encoding and a single-pixel camera, eliminating the need for specialized THz devices.

## Contribution

The authors introduce a novel approach that encodes an NIR probe beam to sample THz fields with high resolution without specialized THz modulation devices.

## Key findings

- Achieved 128×128 field measurement with 62 μm resolution
- Demonstrated sub-wavelength spatial resolution more than 15 times smaller than THz wavelength
- Method is suitable for biomedical sensing and industrial inspection

## Abstract

Recently, computational sampling methods have been implemented to spatially characterize terahertz (THz) fields. Previous methods usually rely on either specialized THz devices such as THz spatial light modulators, or complicated systems requiring assistance from photon-excited free-carriers with high-speed synchronization among multiple optical beams. Here, by spatially encoding an 800 nm near-infrared (NIR) probe beam through the use of an optical SLM, we demonstrate a simple sampling approach that can probe THz fields with a single-pixel camera. This design does not require any dedicated THz devices, semiconductors or nanofilms to modulate THz fields. Through the use of computational algorithms, we successfully measure 128$\times$128 field distributions with a 62 $\mu m$ transverse spatial resolution, more than 15 times smaller than the central wavelength of the THz signal (940 $\mu m$). Benefitting from the non-invasive nature of THz radiation and sub-wavelength resolution of our system, this simple approach can be used in applications such as biomedical sensing, inspection of flaws. in industrial products, and so on.