Fabrication and characterization of shape- and topology-optimized optical cavities with deep sub-wavelength confinement for interfacing with colloidal quantum dots

TL;DR

This paper introduces a novel design and fabrication method for ultra-compact optical cavities with deep sub-wavelength confinement, enabling enhanced interaction with colloidal quantum dots.

Contribution

It combines shape and topology optimization to create manufacturable nanocavities with extremely small mode volumes and demonstrates their optical performance with colloidal quantum dots.

Findings

Cavities achieve mode volumes below 0.1 (λ/2n)^3

High Purcell enhancement observed in photoluminescence

Fabrication process yields high-performance, reliable cavities

Abstract

We employ a combined shape- and topology-optimization strategy to design manufacturable two-dimensional photonic crystal-based optical nanocavities that confine light to length scales well below the resonance wavelength. We present details of the design strategy as well as scanning electron micrographs of the fabricated indium phosphide cavities with a compact footprint of ~"4.5{\lambda}*4.5{\lambda}" , which feature gaps on the order of 10 nm and theoretical mode volumes in the gap center below (0.1 ({\lambda}/2n_air))^3. Subsequent optical characterization of the far-field emission as well as Purcell-enhanced photoluminescence from the cavities with and without spin-coated colloidal quantum dots are compared to numerical simulations. The results corroborate the potential of the design strategy and fabrication process for ensuring high yield and reliable performance as well as the viability of the material platform for exploring light-matter interaction with colloidal QDs.