Resonant bending of silicon nanowires by light

TL;DR

This paper investigates how light resonantly interacts with silicon nanowires, causing significant bending due to optical forces, with potential applications in nanomechanical systems.

Contribution

It reveals a new anti-bonding resonance mode in coupled silicon nanowires that leads to unprecedented optical force enhancement and mechanical deflections.

Findings

Optical forces reach several nano Newtons per micron of wire length.

Wires experience elastic deflection of about 100 nm under specified light conditions.

Resonant coupling causes strong optical force oscillations with incidence angle.

Abstract

Coupling of two dielectric wires with rectangular cross-section gives rise to bonding and anti-bonding resonances. The latter is featured by extremal narrowing of the resonant width for variation of the aspect ratio of the cross-section and distance between wires when the morphology of the anti-bonding resonant mode approaches to the morphology of the Mie resonant mode of effective circular wire with high azimuthal index. Then plane wave resonant to this anti-bonding resonance gives rise to unprecedent enhancement of the optical forces up to several nano Newtons per micron length of wires. The forces oscillate with angle of incidence of plane wave but always try to repel the wires. If the wires are fixed at the ends the optical forces result in elastic deflection of wires of order $100 nm$ for wires's length $50\mu m$ and the light power $1.5mW/\mu m^2$.