Kathirvel Nallappan

3D printed hollow core terahertz Bragg waveguides with defect layers for surface sensing applications

We study a 3D-printed hollow core terahertz (THz) Bragg waveguide for resonant surface sensing applications. We demonstrate experimentally that powder layer thickness variations as small as 3μm can be reliably detected with our sensor.

Exploiting k-space/frequency duality toward real-time terahertz imaging

Imaging at terahertz frequencies has recently received considerable attention because many materials are semitransparent to THz waves. The principal challenge that impedes a widespread use of THz imaging is the slow acquisition time of a conventional point-by-point raster scan. In this work, we present a theoretical formulation and an experimental demonstration of a novel technique for fast compressionless terahertz imaging based on broadband Fourier optics. The technique exploits k-vector/frequency duality in Fourier optics that allows the use of a single-pixel detector to perform angular scans along a circular path, while the broadband spectrum is used to scan along the radial dimension in Fourier domain. The proposed compressionless image reconstruction technique (hybrid inverse transform) requires only a small number of measurements that scales linearly with an image’s linear size, thus promising real-time acquisition of high-resolution THz images. Additionally, our imaging technique handles equally well and on an equal theoretical footing amplitude contrast and phase contrast images, which makes this technique useful for many practical applications. A detailed analysis of the technique’s advantages and limitations is presented, and its place among other existing THz imaging techniques is clearly identified.

Exploiting k-space/frequency duality in Fourier optics towards real-time compression-less terahertz imaging

We present theoretical formulation and experimental demonstration of a novel technique for the fast compression-less terahertz imaging based on the broadband Fourier optics. The technique exploits k-vector/frequency duality in Fourier optics which allows using a single-pixel detector to perform angular scan along a circular path, while the broadband spectrum is used to scan along the radial dimension in Fourier domain. The proposed compression-less image reconstruction technique (hybrid inverse transform) requires only a small number of measurements that scales linearly with the image linear size, thus promising real-time acquisition of high-resolution THz images. Additionally, our imaging technique handles equally well and on the equal theoretical footing the amplitude contrast and the phase contrast images, which makes this technique useful for many practical applications. A detailed analysis of the novel technique advantages and limitations is presented, as well as its place among other existing THz imaging techniques is clearly identified

Real time transmission of ultra-high bit rate data using photonics based terahertz wireless communication system

A Terahertz wireless communication link operating at 140 GHz has been established using photonics based technologies. An error free transmission of pseudo random bit sequence at the rate of 5 Gbps has been demonstrated over the link distance of 30 cm.