title: Three-dimensional IR imaging with uncooled GaN photodiodes using nondegenerate two-photon absorption.
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 three-dimensional (3D) structures using IR femtosecond illumination pulses (1.6 µm and 4.93 µm) 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.
authors.forename: Himansu S
authors.initials: HS
authors.lastname: Pattanaik
authors.forename: Matthew
authors.initials: M
authors.lastname: Reichert
authors.forename: David J
authors.initials: DJ
authors.lastname: Hagan
authors.forename: Eric W
authors.initials: EW
authors.lastname: Van Stryland