Efficient photoconductive terahertz detector with all-dielectric optical metasurface

Oleg Mitrofanov,Ting Shan Luk,Robert J Thompson,Thomas Siday,Igal Brener,John L Reno

doi:10.1063/1.5011420

Abstract

We designed an optically thin photoconductive channel as an all-dielectric metasurface comprising an array of low-temperature grown GaAs nanobeams and a sub-surface distributed Bragg reflector. The metasurface exhibited enhanced optical absorption, and it was integrated into a photoconductive THz detector, which showed high efficiency and sensitivity as a result. The detector produced photocurrents over one order of magnitude higher compared to a similar detector with an unstructured surface with only 0.5 mW of optical excitation while exhibiting high dark resistance required for low-noise detection in THz time-domain spectroscopy and imaging. At that level of optical excitation, the metasurface detector showed a high signal to noise ratio of 106. The detector showed saturation above that level.

Highlights

Detection of terahertz (THz) radiation with high sensitivity and efficiency remains a challenging problem for THz technology development.[1]
For efficient photo-carrier generation, the channel thickness is typically made comparable to the optical absorption length, which is in the range of 1 μm for bulk direct bandgap semiconductors.[5]
Plasmonic nanostructures introduce Ohmic losses, which can substantially reduce the responsivity of THz detectors

Summary

Introduction

Detection of terahertz (THz) radiation with high sensitivity and efficiency remains a challenging problem for THz technology development.[1]. Efficient photoconductive terahertz detector with all-dielectric optical metasurface

Objectives

Results

Conclusion