Wave front adaptation using a deformable mirror for adiabatic nanofocusing along an ultrasharp gold taper

TL;DR

This paper presents an adaptive wave front optimization method using a deformable mirror to significantly improve nanofocusing efficiency of surface plasmon polaritons along a gold taper, advancing nanoscale light control.

Contribution

It introduces a novel adaptive wave front control scheme for adiabatic nanofocusing, achieving eight-fold efficiency enhancement on complex gold taper geometries.

Findings

Eight-fold increase in nanofocusing efficiency.

Optimized wave front shape analysis.

General applicability for nanoscale light control.

Abstract

We describe and demonstrate the use of an adaptive wave front optimization scheme for enhancing the efficiency of adiabatic nanofocusing of surface plasmon polariton (SPP) waves along an ultrasharp conical gold taper. Adiabatic nanofocusing is an emerging and promising scheme for controlled focusing of far field light into nanometric volumes. It comprises three essential steps: SPP excitation by coupling far field light to an SPP waveguide, SPP propagation along the waveguide and adiabatic SPP nanofocusing towards a geometric singularity. For commonly used complex waveguide geometries, such as, e.g., conical metal tapers, a realistic modeling and efficiency optimization is challenging. Here, we use a deformable mirror to adaptively control the wave front of the incident far field light. We demonstrate an eight-fold enhancement in nanofocusing efficiency and analyze the shape of the resulting optimized wave front. The introduced wave front optimization scheme is of general interest for guiding and controlling light on the nanoscale.