3-D IR imaging with uncooled GaN photodiodes using nondegenerate two-photon absorption

TL;DR

This paper demonstrates 3D infrared imaging using uncooled GaN photodiodes enhanced by nondegenerate two-photon absorption, enabling high depth resolution and broad wavelength compatibility in IR imaging.

Contribution

It introduces a novel IR imaging technique leveraging enhanced two-photon absorption in GaN photodiodes for 3D imaging with sub-wavelength depth resolution.

Findings

Depth resolution can be less than a wavelength.

System works across a wide IR wavelength range.

Imaging achieved with femtosecond IR pulses.

Abstract

We utilize the recently demonstrated orders of magnitude enhancement of extremely nondegenerate two-photon absorption in direct-gap semiconductor photodiodes to perform scanned imaging of 3D structures using IR femtosecond illumination pulses (1.6 um and 4.93 um) gated on the GaN detector by sub-gap, femtosecond pulses. While transverse resolution is limited by the usual imaging criteria, the longitudinal or depth resolution can be less than a wavelength, dependent on the pulsewidths in this nonlinear interaction within the detector element. The imaging system can accommodate a wide range of wavelengths in the mid-IR and near-IR without the need to modify the detection and imaging systems.