This paper presents a novel tunable infrared filter applying a subwavelength grating that substitutes the distributed Bragg reflectors (DBRs) in tunable Fabry-Perot (FP) filters to reduce cost and fabrication effort. It consists of uniformly arranged disc resonators which are made of 100 nm thick aluminum at a 200 nm Si3N4 membrane carrier that stands freely after fabrication. The dimensions of the subwavelength structures were optimized based on finite difference time domain (FDTD) analysis. The fabrication sequence consists of silicon MEMS technology steps like deposition and patterning of electrodes and of isolation layers, silicon etching, and wafer bonding, and it includes nano imprint lithography for forming the subwavelength structures at wafer level. The samples have an aperture of 2 mm and are mechanically tuned by electrostatic forces with tuning voltages up to 80 V. They show the typical characteristics of FP filters but with high peak transmittance within a remarkably large wavelength range (T < 50% @ 2.5 μm … 6.5 μm) spanning over 5 interference orders of the optical resonator. The optical performance was measured by Fourier transform infrared spectrometer and compared to the simulation results. It shows a widely good agreement between calculation and measurement.
Driven by the demand of miniaturized and highly integrated functionalities in the area of photonics and photonic circuits,
the metal or plasmon optics has become a promising method for manipulating light at the nanometer scale.
Especially the application of periodic sub wavelength hole structures within an opaque metal film on a dielectric
substrate holds many advantages for the realization of optical filters, since the variation of the hole diameter and the
periodicity allows a selective filter response.
This paper is concerned with the modeling, fabrication and characterization of a sub wavelength hole array for surface
plasmon enhanced transmission of light . The theoretical backgrounds as well as the basics of the simulation by
Finite-Difference Time-Domain (FDTD) are described for the target structure with a hole diameter of 180 nm and a
periodicity of 400 nm.
By using a double-molding technology via nanoimprint lithography the fabrication of this sub wavelength hole array
with a peak wavelength of 470 nm and full width at half maximum of 50 nm from a silicon nanopillar master is
demonstrated. In order to ensure the dimensional stability of the molded structures, characterization was consequently
done by means of a self made non-contact mode atomic force microscope.