Spatial Polarization Modulation for Terahertz Single-Pixel Imaging
Seth N. Lowry, James M. Flood, Glitta R. Cheeran, M. Reid, Christopher M. Collier
Abstract
Terahertz (THz) technology has been developed to meet advancements in spatial light modulation of frequencies in the THz regime, where fast modulation techniques designed for optical wavelengths perform poorly. Applications of THz frequencies in nondestructive imaging and quality testing have been thoroughly explored—specifically, polarization-resolved measurements can be scanned to image fiber anisotropy and birefringence in wood products and 3D printed materials and strains in plastics. There is a need to explore faster image acquisition techniques, such as single pixel imaging (SPI) via spatial light modulation, to realize fast polarization-resolved THz imagers. Such spatial light modulators are vital for patterning the THz imaging beam before interacting with the sample to reconstruct the response of the sample with a single detector via compressive sensing algorithms. In this work, a spatial polarization modulation scheme is employed using wire grid polarizer (WGP) mask patterns to acquire polarization-resolved images of polarizing samples at 0.1 THz. A laser ablation technique is used to fabricate 8 × 8 WGP masks with randomly vertical and horizontal wire grids to pattern the imaging beam and enable orthogonal polarization images. With various sampling amounts, 8 × 8 polarization images are successfully reconstructed for polarizing samples of low and high spatial frequencies.