THz Metal-Mesh Bandpass Filters with Diamond-shaped Apertures for Sensitive THz Receivers

TL;DR

This paper introduces high-performance THz metal-mesh bandpass filters with diamond-shaped apertures, designed to improve the sensitivity of superconducting THz receivers by reducing direct detection effects.

Contribution

The paper presents a simple, precise design of metal-mesh filters with diamond-shaped apertures, validated by simulations and measurements, enhancing THz receiver performance.

Findings

High peak power transmission (>90%) at normal incidence.

Accurate filter performance predicted by simple design equations.

Excellent agreement between measured and simulated transmission profiles.

Abstract

We present high-performance terahertz (THz) metal-mesh bandpass filters developed to mitigate direct detection effects in sensitive THz receivers based on superconducting hot-electron bolometer (HEB) mixers. These metal-mesh filters are free-standing 5-micron thick sheets of copper perforated with a periodic array of diamond-shaped apertures. The simple aperture design minimizes the effect of fabrication (rounding) errors on filter performance, allowing precise engineering of the center frequency (1.5-5.5 THz) while maintaining high (>90 %) peak power transmission at normal incidence and a relatively narrow bandwidth of 5-15 %. Based on finite-element method (FEM) simulation results, we provide simple design equations that can be used for rapid design with high accuracy. The measured transmission profiles of 1.9-THz, 2.5-THz, and 4.7-THz filters show excellent agreement with the simulation results. These filters are compatible with cryogenic operation and can substantially reduce the direct detection effects in HEB mixers.