Abstract
In this paper, we present a shutter-based electro-optical modulator made of two parallel nanoelectromechanical silicon nitride string resonators. These strings are covered with electrically connected gold electrodes and actuated either by Lorentz or electrostatic forces. The in-plane string vibrations modulate the width of the gap between the strings. The gold electrodes on both sides of the gap act as a mobile mirror that modulate the laser light that is focused in the middle of this gap. These electro-optical modulators can achieve an optical modulation depth of almost 100% for a driving voltage lower than 1 mV at a frequency of 314 kHz. The frequency range is determined by the string resonance frequency, which can take values of the order of a few hundred kilohertz to several megahertz. The strings are driven in the strongly nonlinear regime, which allows a frequency tuning of several kilohertz without significant effect on the optical modulation depth.
Highlights
Optomechanical systems have generated a lot of interest [1,2,3], in part because of their many applications as sensors for precision measurements [4, 5], and because of their usefulness as reconfigurable metamaterials [6,7,8,9,10,11] and as plasmomechanical resonators [12,13,14,15,16,17,18]
Reconfigurable metamaterials made of arrays of silicon nitride string resonators have been demonstrated as effective electro-optic modulators, where the strings were actuated using either electrostatic forces [6], Lorentz forces [9], or electrostriction [11]
We present a different kind of electrooptical modulator, made of two gold covered and electrically connected silicon nitride string resonators, separated by a small gap in their center, similar to the structures used by Thijssen et al in Ref. [12], but actuated electromagnetically using Lorentz forces to change the width of the gap between the strings, by driving one of the strings at the resonance frequency of its in-plane fundamental mode
Summary
Optomechanical systems have generated a lot of interest [1,2,3], in part because of their many applications as sensors for precision measurements [4, 5], and because of their usefulness as reconfigurable metamaterials [6,7,8,9,10,11] and as plasmomechanical resonators [12,13,14,15,16,17,18]. Reconfigurable metamaterials made of arrays of silicon nitride string resonators have been demonstrated as effective electro-optic modulators, where the strings were actuated using either electrostatic forces [6], Lorentz forces [9], or electrostriction [11]. These metamaterial-based electro-optical modulators suffer from having either low optical modulation depths [9] or requiring high driving voltages [6, 11]. We tested similar structures that were actuated using electrostatic forces
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