Optical coupling between resonant dielectric nanoparticles and dielectric waveguides probed by third harmonic generation microscopy

TL;DR

This study experimentally investigates how resonant dielectric nanodisks couple with silicon waveguides using third harmonic generation microscopy, revealing significant modulation of nonlinear signals and insights into integrated photonics applications.

Contribution

It provides the first experimental analysis of optical coupling between dielectric nanodisks and waveguides, demonstrating modulation effects and field enhancement mechanisms.

Findings

Third harmonic intensity modulates by up to 4.5 times with nanodisk-waveguide distance.

Coupling alters local field enhancement and magnetic resonances within nanodisks.

Waveguide introduces additional loss but can increase local field strength in nanodisks.

Abstract

Localized electromagnetic modes and negligible Ohmic losses dictate the growing interest in subwavelength all-dielectric nanoparticles. Although an exhaustive volume of study dealt with interaction of all-dielectric nanostructures with free-space electromagnetic fields, their performance as integrated photonics elements remains untackled. We present an experimental study of optical coupling between a resonant subwavelength silicon nanodisk and a non-resonant silicon waveguide, as probed by third harmonic generation microscopy. By placing the nanodisks at different distances from the waveguide, we observe third harmonic intensity modulation by a factor of up to 4.5. This modulation is assigned to changes in the local field enhancement within the nanodisks caused by their coupling to the waveguides and subsequent modulation of their magnetic-type resonances. Interestingly, although the waveguide presents an additional loss channel for the nanodisk, we observe an increase in the local field strength within the nanodisk, as verified by rigorous full-wave simulations. This work makes a step toward integration of all-dielectric nanoparticles on photonic chips.