Elucidating gigahertz acoustic modulation of extraordinary optical transmission through a two-dimensional array of nano-holes

Abstract

The ultrafast modulation of light transmitted by a metamaterial making up an extraordinary optical transmission geometry is investigated by means of optical pump-probe spectroscopy. Using a sample consisting of a lattice of square nano-holes in a gold film on a glass substrate, we monitor the high-frequency oscillations in the intensity of transmitted infrared light. A variety of gigahertz acoustic modes, involving the opening and shutting motion of the holes as well as the straining of the glass substrate below the holes, are revealed to be active in the optical modulation. Numerical simulations of the transient deformations and strain fields elucidate the nature of the vibrational modes contributing most strongly to the variations in optical transmission, and point to the hole-area modulation as the dominant effect. Potential applications include ultrafast acousto-optic modulators.

Gigahertz Optomechanical Photon–Phonon Transduction between Nanostructure Lines

“…δR also depends on the photoelastic coupling to the substrate and on surface deformations, which modulate the reflected intensity as well as diverting some light away from the optical collection system. (The photoelastic effect in gold at ∼800 nm probe wavelength is known to be small. , ) This optical detection becomes less sensitive to higher-order vibrational modes owing to the canceling between positively and negatively directed portions of the deformation fields, as previously noted . We suspect that this is the reason that our optical detection homes in selectively on the lower-order vibrational modes.…”

“…The scattering of the incident plane-wave surface phonon wavepacket on the receiver nanorod array enables optical detection from both the nanorod and substrate strain through the photoelastic effect as well as directly arising from surface deformations, as postulated for other nanostructures. ,, …”

Extraordinary nonlinear transmission modulation in a doubly resonant acousto-optical structure

“…This motion modulates the volume of the photonic cavities and hence the resonant optical frequency. Compared with recent attempts at designing periodic metal-dielectric structures showing enhanced AO modulation [24,25], a significant difference is that the ridges are here relatively free to vibrate with large amplitude, since they are attached to the substrate only at their base. Similar to the prongs of a tuning fork, each couple of ridges in a period of the array oscillates anti-symmetrically, creating a vibration node near the substrate surface that minimizes mechanical energy dissipation by radiation.…”

The Fabrication of Nanostructures on Polydimethylsiloxane by Laser Interference Lithography

“…A number of photoelectric and biological devices, for instance, nano-generators [1], sensors [2], and micro-flow paths [3], require flexibility to broaden their applications. Nano-patterns have extensive and prominent applications in various fields, because they are the bases for the realization of different phenomena and functions [4,5,6,7,8]. Therefore, the fabrication of nanoscale patterns on flexible substrates with a low cost, large area, and high throughput using laser interference lithography will have both commercial and scientific interests.…”