Abstract
We used a reversal imprinting-in-metal (RIM) process to fabricate various three-dimensional (3D) metal structures under low pressure. Molds featuring different shapes were used to pattern various subwavelength metal structures, including pyramidal, hole-array, and crater-like structures. Refractive index matching and cavity effects both enhanced the degree of transmission of these structured metal films. The crater-like structure appears to be a promising material because of the unique properties imparted by the elongated and gradually tapering spacing of its cavities. From both near-field simulations and experimentally obtained optical spectra, we found that the cavity effect in the crater-like structure led to significantly enhanced transmission of the optical intensity. Thus, this RIM process allows the ready fabrication of various two- and three-dimensional metallic structures for use in surface plasmon-based devices.
Highlights
Surface plasma resonance (SPR) phenomena are at the core of many fascinating studies in physics [1,2,3,4], chemistry [5,6] and surface plasmon resonance sensors [7]
A SPR transmittance enhancement can be obtained in the corrugated gold films having a period of 400nm and a height of 120nm which is attributed to its larger curvature than the larger period structures
The transmission spectrum of the corrugated gold film having a period of 400 nm reveals that SPR, induced by the periodic metal structure, caused the transmittance peak to shift to 530 nm, with the peak intensity increasing to 27.2% from the value of 19.5% of the flat gold film
Summary
Surface plasma resonance (SPR) phenomena are at the core of many fascinating studies in physics [1,2,3,4], chemistry [5,6] and surface plasmon resonance sensors [7]. There are two main approaches through which the missing momentum can be provided for the extra wave-vector generating SPs: (i) sub-wavelength hole-arrays allowing scattering from a topological defect on the metal surface or (ii) the use of periodic corrugation in the metal surface. Combining hole-arrays with sinusoidal profiles leads to this certain type of 3D metal structure that possesses unique optical characteristics. These complicated structures are almost impossible to fabricate using conventional lithographic methods. We demonstrate the fabrication of complicated 3D metallic structures featuring a variety of patterns through RIM processing using various shaped molds Some of these metallic structures have potential use in SPR-based and photonics devices. We have observed extraordinary transmittance assisting through cavity- and refractive index-matching effects in our sub-wavelength hole-array structures
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