Abstract
We experimentally demonstrate the ability to create additional transmission resonances in a double-layer aperture array by varying the interlayer gap spacing. In the case of periodic aperture arrays, these additional resonances are sharply peaked, while for random aperture arrays the resonances are broad. Surprisingly, these additional resonances only occur when the interlayer gap spacing is greater than half the aperture spacing on a single array. Since there is no corresponding periodicity in the random arrays, these resonances occur regardless of how small the gap spacing is made. This phenomenon can be accurately modeled only if the correct frequency-dependent complex dielectric function of a metal film perforated with subwavelength apertures is used. Using THz time-domain spectroscopy, we are able to directly obtain the complex dielectric response function from the THz experimental transmission measurements. We conclude by demonstrating several passive free-space THz filters using multilayer aperture arrays. Importantly, we show that the magnitude of the lowest order resonance can be approximately maintained, while the background transmission can be significantly suppressed leading to a significant improvement in the optical filter fidelity.
Highlights
Technology development within the terahertz (THz) spectral range (1 THz = 1012 Hz) has lagged severely behind that of other regions of the electromagnetic spectrum [1,2]
Single layer periodic [5] and aperiodic [6] arrays of subwavelength apertures fabricated in metal films have been shown to exhibit resonantly enhanced transmission approaching unity [7,8], even for relatively small fractional aperture areas
We show that when two or more aperture arrays are placed in close proximity to one another, new transmission resonances arise that are associated with the gap spacing between the arrays, offering an additional mechanism for tailoring their optical properties
Summary
A significant reason for this lies in the fact that dielectric materials typically used for passive and active device applications in microwave and optical applications tend to exhibit high loss at THz frequencies. We show that when two or more aperture arrays are placed in close proximity to one another, new transmission resonances arise that are associated with the gap spacing between the arrays, offering an additional mechanism for tailoring their optical properties. Proper design of these additional resonances requires that the complex dielectric response of the single aperture array be determined. The resonant optical properties of subwavelength aperture arrays ( known as ‘plasmonic lattices’) have been explained in terms of SPPs that mediate the metal-light interaction via coupling to corrugated metal surfaces [5], where the electromagnetic field associated with the SPPs decays exponentially from the metal-dielectric interface. We show that this coupling forms additional resonances for small values of d that may be used in designing THz filters
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
