Abstract

We demonstrate an efficient terahertz (THz) detector based on an optical hybrid cavity, which consists of an optically thin photoconductive layer between a distributed Bragg reflector (DBR) and an array of electrically isolated nanoantennas. Using a combination of numerical simulations and optical experiments, we find a hybrid cavity design which absorbs <75% of incident light with a 50 nm photoconductive layer. By integrating this optical hybrid cavity design into a THz detector, we see enhanced detection sensitivity at the operation wavelength (∼815 nm) over designs which do not include the nanoantenna array.

Highlights

  • A significant technological challenge in the terahertz (THz) frequency range is the development of efficient nanoscale THz detectors

  • The efficiency of photoconductive (PC) THz detectors based on low temperature grown (LT) GaAs is limited by the bulk material properties: the mean free path of photo-excited carriers, and the optical absorption length

  • An optically thin photoconductive layer of LT-GaAs is sandwiched between a distributed Bragg reflector (DBR) and a Gold nanoantenna array, which is electrically isolated from the photoconductive layer with a 15 nm thick layer of Al2O3

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Summary

INTRODUCTION

A significant technological challenge in the terahertz (THz) frequency range is the development of efficient nanoscale THz detectors. A popular method to mitigate the material limitations is to modify the photoconductive antenna to incorporate plasmonic nano-electrodes[1,2,3,4,5,6] These electrodes support an optical plasmon resonance, which strongly localizes the generation of electron-hole pairs to the vicinity of the nano-electrodes. An optically thin photoconductive layer of LT-GaAs is sandwiched between a DBR and a Gold nanoantenna array, which is electrically isolated from the photoconductive layer with a 15 nm thick layer of Al2O3.

THICKNESS OF THE PHOTOCONDUCTIVE LAYER
PERIODICITY OF THE NANOANTENNA ARRAY
SIZE OF THE NANOANTENNAS
TERAHERTZ CHARACTERISATION
CONCLUSIONS

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