Three-dimensional THz lumped-circuit resonators.

Yanko Todorov,Pascal Desfonds,Loïc Becerra,Carlo Sirtori,Cherif Belacel

doi:10.1364/oe.23.016838

Abstract

Our work describes a novel three dimensional meta-material resonator design for optoelectronic applications in the THz spectral range. In our resonant circuits, the capacitors are formed by double-metal regions cladding a dielectric core. Unlike conventional planar metamaterials, the electric field is perpendicular to the surface and totally confined in the dielectric core. Furthermore, the magnetic field, confined in the inductive part, is parallel to the electric field, ruling out coupling through propagation effects. Our geometry thus combines the benefit of double-metal structures that provide parallel plate capacitors, while maintaining the ability of meta-material resonators to adjust independently the capacitive and inductive parts. Furthermore, in our geometry, a constant bias can be applied across the dielectric, making these resonators very suitable for applications such as ultra-low dark current THz quantum detectors and amplifiers based on quantum cascade gain medium.

Highlights

The electric field is perpendicular to the surface and totally confined in the dielectric core
In our geometry, a constant bias can be applied across the dielectric, making these resonators very suitable for applications such as ultra-low dark current THz quantum detectors and amplifiers based on quantum cascade gain medium
Metamaterials rely on arrays of miniature circuit-resonators, such as split-rings, that can confine the electromagnetic field into sub-wavelength volumes [1], down to nanometer sizes [2,3,4]

Summary

Introduction

Metamaterials rely on arrays of miniature circuit-resonators, such as split-rings, that can confine the electromagnetic field into sub-wavelength volumes [1], down to nanometer sizes [2,3,4]. In order to demonstrate that the resonant frequency can be tuned separately through the capacitive and inductive parts, we prepared arrays of resonators where the dimensions of the parameters W, Lx and Ly were varied from 2μm to 8μm, keeping a dielectric thickness T = 2μm This allowed us to vary independently the capacitor size W, and the perimeter of the inductive loop Lx + Ly. In Figs. Almost the same frequency is recovered by shrinking the loop and increasing the capacitor, as seen for the pair (444, 284) and the triplet (422, 224, 242) This indicates clearly that, provided the resonant frequency fres, the inductive part and the capacitive part can be adjusted separately so that very sub-wavelength values of the electric field confinement volumes Vcapa are achieved. For the double-metal capacitors, we use the two dimensional version of the Palmer formula [33, 34]: C

WE T

Findings

Conclusion