Direct measurement of plasmon propagation lengths on lithographically defined metallic waveguides on GaAs

TL;DR

This paper reports direct measurements of plasmon propagation lengths on lithographically defined GaAs waveguides, demonstrating lengths of 10-40 μm and confirming high-quality fabrication for future plasmonic devices.

Contribution

It introduces a method for directly measuring plasmon propagation lengths on lithographic GaAs waveguides, with results matching theoretical predictions.

Findings

Propagation lengths range from 10 to 40 μm.

Waveguide width and wavelength influence propagation length.

High-quality lithographic fabrication is confirmed.

Abstract

We present optical investigations of rectangular surface plasmon polariton waveguides lithographically defined on GaAs substrates. The plasmon propagation length is directly determined using a confocal microscope, with independent polarization control in both excitation and detection channels. Surface plasmon polaritons are launched along the waveguide using a lithographically defined defect at one end. At the remote end of the waveguide they scatter into the far-field, where they are imaged using a CCD camera. By monitoring the length dependence of the intensity of scattered light from the waveguide end, we directly extract the propagation length, obtaining values ranging from LSPP = 10-40 {\mu}m depending on the waveguide width (w=2-5 {\mu}m) and excitation wavelength (760-920 nm). Results are in good accord with theoretical expectations demonstrating the high quality of the lithographically defined structures. The results obtained are of strong relevance for the development of future semiconductor based integrated plasmonic technologies.