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

摘要

We utilize the recently demonstrated orders of magnitude enhancement ofextremely nondegenerate two-photon absorption in direct-gap semiconductorphotodiodes to perform scanned imaging of 3D structures using IR femtosecondillumination 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 imagingcriteria, the longitudinal or depth resolution can be less than a wavelength,dependent on the pulsewidths in this nonlinear interaction within the detectorelement. The imaging system can accommodate a wide range of wavelengths in themid-IR and near-IR without the need to modify the detection and imagingsystems.