Photonic bound states in the continuum in Si structures with the self-assembled Ge nanoislands

TL;DR

This paper demonstrates a significant enhancement of photoluminescence in Ge nanoislands integrated with silicon photonic crystal slabs, leveraging bound states in the continuum to improve optoelectronic device performance.

Contribution

It provides the first experimental evidence of PL enhancement via bound states in the continuum in Ge nanoislands on silicon photonic structures.

Findings

Over two orders of magnitude PL enhancement observed

Theoretical analysis confirms the role of quasi-normal guided modes

Symmetry analysis of modes supports experimental results

Abstract

Germanium self-assembled nanoislands and quantum dots are very prospective for CMOS-compatible optoelectronic integrated circuits but their luminescence intensity is still insufficient for many practical applications. Here, we demonstrate experimentally that photoluminescence of Ge nanoislands in silicon photonic crystal slab with hexagonal lattice can be dramatically enhanced due to the involvement in the emission process of the bounds states in the continuum. We experimentally demonstrate more than two orders of magnitude peak photoluminescence enhancement and more than one order of magnitude integrated PL enhancement in a photonic crystal slab compared with the non-structured sample area. We theoretically study this effect by the Fourier modal method in the scattering matrix form and demonstrate the appearance of quasi-normal guided modes in our photonic crystal slab. We also describe their symmetry in terms of group theory. Our work paves the way towards a new class of optoelectronic components compatible with silicon technology.