Terahertz single pixel imaging with an optically controlled dynamic spatial light modulator

Abstract

We present a single pixel terahertz (THz) imaging technique using optical photoexcitation of semiconductors to dynamically and spatially control the electromagnetic properties of a semiconductor mask to collectively form a THz spatial light modulator (SLM). By co-propagating a THz and collimated optical laser beam through a high-resistivity silicon wafer, we are able to modify the THz transmission in real-time. By further encoding a spatial pattern on the optical beam with a digital micro-mirror device (DMD), we may write masks for THz radiation. We use masks of varying complexities ranging from 63 to 1023 pixels and are able to acquire images at speeds up to 1/2 Hz. Our results demonstrate the viability of obtaining real-time and high-fidelity THz images using an optically controlled SLM with a single pixel detector.

A low-voltage high-speed terahertz spatial light modulator using active metamaterial

“…From these set of single-pixel measurements, the reconstructed image can be represented by the matrix equation X image = Φ −1 × Y meas , where Y meas is a column vector with M-elements representing the M measurements taken, Φ is the M × N measurement matrix, in which each row represents a mask displayed in the SLM, and X image is the reconstructed image with N pixels. 10 Using compressed sensing (CS) techniques, a much smaller number of measurements are made than…”

“…The key to single-pixel imaging is to come up with the smallest set of coded masks at the SLM plane, where the image is reconstructed from those encoded single-pixel measurements [8][9][10] (for details see Section VI). The electronically controlled SLM avoids any mechanical movements as in raster scan, thus further improving the speed of acquisition.…”

“…10 The disadvantage of such a setup is higher complexity and cost. Recent research has demonstrated THz SLMs using all-electronic dynamic metamaterials used in single-pixel THz imaging systems.…”

“…Recent research has demonstrated THz SLMs using all-electronic dynamic metamaterials used in single-pixel THz imaging systems. 10,15,16 These dynamic metamaterial SLMs are electronically controlled by injecting charges or depleting them in the bulk semiconductor substrate, which is an inherently slow process due to the intrinsically large capacitance of what is essentially a large bulk diode structure. 15,17,18 This results in a slow switching speed and large dynamic power consumption.…”

Simulation of an Asymmetric Transvers Electric TE Metamaterial Absorber

“…Due to the resonant behavior of LHMs, LHMs can exhibit extreme values of the effective medium parameters such as large and negative dielectric permittivity and permeability [3] which usually renders them dissipative and can be scaled from microwave [4] and terahertz [5,6] through the infrared [7,8] almost into optical frequencies [10]. Optimized metamaterials with high absorption have been proposed for applications such as thermal spatial light modulators [11], plasmonic sensors [12,13], thermal bolometers [14], anti-reflection coatings [15] and solar thermo-photovoltaic [16]. The goal of photovoltaic structures is to absorb as much light as possible within specific layers.…”