In this project we propose and fabricate a hyperbolic metamaterials-based narrowband notch filter for the infrared regime with a center wavelength that remains fixed as the angle of incidence changes from 0 to 30 degrees for TM polarization. This novel device modifies a conventional Bragg reflector by including a middle resonance layer that opens up a narrow, highly transmissive band. To achieve angular independence, a subwavelength sized array of silver wires are inserted in a vertical orientation and permeate all 7 Si and SiO2 layers of the structure.
In this work the theoretical underpinnings are explored using Maxwell-Garnett Theory, and simulated with 3D finite element full wave electromagnetic modeling software. Simulations demonstrate that the device is capable of up to 60% transmission at a fixed center wavelength for TM polarization in the infrared.
The device is fabricated using typical microfabrication techniques. The silver nanowires are fabricated via DC electrodeposition. The angle and polarization dependent transmission, reflection and absorption of the device are experimentally measured, and scanning electron microscopy images of the structure are shown.
Though the experimental validation of this device is performed for the infrared regime, scaling the structural sizes can extend the operating regime to higher and lower wavelengths. Whether used as a stand-alone filter, or integrated into a hyperspectral array, the angle-independent response of this filter has many uses in remote sensing applications.