Project 3: Toward plasmonic enhancement and site-templated telecom quantum emitters

The dream of a quantum internet, in which quantum entanglement can be widely distributed over fiber optic networks, relies on having bright high quality single photon sources at telecom wavelengths. We will pursue two approaches to develop material and device platforms that could enable an array of telecom-wavelength quantum emitters. The first approach will combine the expertise of Zide, Doty, and Balakrishnan. We will start with III-V substrates that are templated by Doty to create preferential nucleation sites for QDs. Balakrishnan will then adapt the methods developed by Zide to grow GaSb QDs within these nucleation sites. Balakrishnan’s group has been working on the growth of GaSb QDs for over a decade and has been able to demonstrate a variety of results including single dot emission, type II laser operation, and the fabrication of GaSb quantum rings, as shown in Fig G. Once Balakrishnan has succeeded in growing GaSb QDs at the site-templated locations, he will cap the QDs with a GaAs dielectric layer so that Habteyes can explore coupling of these QDs to plasmonic structures. Our goals are to achieve a Purcell enhancement of the photon extraction efficiency and understand plasmon enhanced photoabsorption and light emission nonlinearities that could provide additional photonic functionality. Specifically, we will investigate the nonlinear dependence of light emission on incident laser power using GaSb/GaAs QDs coupled to colloidal AuNRs through dielectric spacers optimized to block hot electron transfer while staying close to the maximum near-field enhancement regime, as depicted in Fig. H. Our second approach to achieving an array of telecom-wavelength quantum emitters is based on 2d semiconductors and will extend the research described in Project 1. Specifically, we will explore α-phase 2H-molybdenum ditelluride (MoTe2), which has a layer-dependent bandgap in the NIR regime, holding promise for telecom-compatible single-photon emission in the O and C band.

Fig G Caption: Nanopatterned semiconductor QDs. (left) complete GaAs nanopyramid structures, (center) facet-selective nucleation of InAs dots, and (right) Hybrid VLS/selective-area epitaxy approach for growth of GaSb QDs. [ Ref 1, Ref 2 ]

Fig H Caption: Calculated scattering spectra of AuNR on GaAs (a) and on AuF (b) with different dielectric (n = 1.45) spacer thicknesses, and near-field localization displaced on a vertical plane that cuts the rod through its long axis for representative spacer thickness (d).