Self-aligned hybrid nanocavities using atomically thin materials

TL;DR

This paper introduces a novel method to create self-aligned hybrid nanocavities by partially covering photonic crystal waveguides with atomically thin 2D materials, achieving high quality factors and cavity enhancement.

Contribution

The authors demonstrate a new approach to form hybrid nanocavities using 2D materials directly on photonic waveguides, avoiding degradation of cavity quality and enabling self-alignment.

Findings

Achieved Q factors up to 4.0×10^5 in hybrid nanocavities.

Mono- and few-layer 2D flakes can induce nanocavity formation.

Observed cavity photoluminescence enhancement with a Purcell factor of about 15.

Abstract

Two-dimensional (2D) van der Waals layered materials with intriguing properties are increasingly being adopted in hybrid photonics. The 2D materials are often integrated with photonic structures including cavities to enhance light-matter coupling, providing additional control and functionality. The 2D materials, however, needs to be precisely placed on the photonic cavities. Furthermore, the transfer of 2D materials onto the cavities could degrade the cavity quality $(Q)$ factor. Instead of using prefabricated PhC nanocavities, we demonstrate a novel approach to form a hybrid nanocavity by partially covering a PhC waveguide post-fabrication with a suitably-sized 2D material flake. We successfully fabricated such hybrid nanocavity devices with hBN, WSe$_2$ and MoTe$_2$ flakes on silicon PhC waveguides, obtaining $Q$ factors as high as $4.0\times10^5$. Remarkably, even mono- and few-layer flakes can provide sufficient local refractive index modulation to induce nanocavity formation. Since the 2D material is spatially self-aligned to the nanocavity, we have also managed to observe cavity PL enhancement in a MoTe$_2$ hybrid cavity device, with a cavity Purcell enhancement factor of about 15. Our results highlights the prospect of using such 2D materials-induced PhC nanocavity to realize a wide range of photonic components for hybrid devices and integrated photonic circuits.