Quantum emitters are essential for quantum optics and photonic quantum information technologies. To date, diverse quantum emitters such as single molecules, quantum dots, and color centers in diamond have been integrated onto chips by various methods which typically have complex operation. Here, our quantum emitters are colloidal CdSe/ZnS quantum dots (QDs) embedded in polymeric nanostructures. We report two approaches based on photo-polymerization for deterministically integrating quantum emitters on chips. Firstly, based on one-photon polymerization (OPP), we coupled an external excitation laser into surface ion exchanged waveguides (IEWs), the surface evanescent wave resulting in the QD-polymer ridges. In order to scale down the dimension of the QD-polymer structures, we secondly fabricated QD-polymer nano-dots on glass substrates by a direct laser writing platform (DLW) based on two-photon polymerization (TPP). A deep fabricating parameters study has been made enable us to control the dimensions of the polymer-QDs nanocomposites. Moreover, photoluminescence (PL) measurement results demonstrate the feasible and potential of our method for integrating quantum emitters onto future complex photonic chips.
Hybrid nanoplasmonics is a recent and promising branch of research, that attempts to control the energy transfer between nano-emitters and surface plasmons. Colloidal quantum dots are good emitters due to their unique set of optical properties. In our work, quantum dots were excited in close proximity to a silver nanowire and the quantum dot emission was transferred into guided propagating nanowire surface plasmons (SPs) that were scattered at the nanowire end. Compared with metallic nanoparticles, silver nanowires enable the propagation of SPs in a well-defined direction along the nanowire axis, allowing for long-distance energy transfer between the nano-emitter and a specific nanowire point of interest. The challenge related to this promising hybrid system is to control the position of quantum dots on the nanowire. Our approach of nano-emitters positioning is based on two-photon photopolymerization of a photosensitive material containing quantum dots. This approach allows one to use light for positioning the quantum dots on the plasmonic nanosystem in a controlled manner. We report on a new controlled hybrid plasmonic nanoemitter based on coupling between quantum dots and propagating surface plasmons that are supported by silver nanowires, considered as surface plasmons resonators and observed through their scattering at the nanowire ends. A parametric study of the distance between the quantum dots and the nanowire extremity shows that precise control of the position of the launching sites enables control of light intensity at the wire end, through surface plasmon propagation length. This new approach is promising to produce efficient acceptor-donor hybrid nano-systems.
Very recently, the interest for quantum technologies by the scientific community and industry has strongly increased. Different types of implementations have been proposed as a practical implementation for a quantum bit. In particular, quantum photonics is a strong candidate for such applications. We are interested in using single photons and single spins in diamond as a solid state host matrix (nanodiamonds or membranes). Integration of nanosources of light is currently a major bottleneck preventing the realisation of all-photonic chips for quantum technologies and nanophotonics applications. Ideally, one needs optical circuitry, on-chip photodetection and on-chip generation of quantum states of light (single photons, entangled photons…). Our recent work on a new platform for quantum photonics using integrated optics can offer an easier and robust way to create compact quantum circuits that can be on chip and scalable. In this context, the coupling between waveguides and single photon emitters is critical. The goal of our research is to efficiently couple single photon emitters with a new platform made of optical glass waveguides. These waveguides are based on the so-called ion-exchange glass technology and is know in the photonics industry for quite some time but has never been used in the context of quantum technologies. Efficient light-matter interface is of primordial importance in this system. To achieve this goal, several paths are undertaken such as the use of dielectric and plasmonic structuration in order to increase the light interaction with the waveguide or to develop fabrication techniques to insert the emitters directly inside the guide (for nanodiamonds). We will show what is our current state of the art for placing single emitters at the right place on our optical waveguides made of ion-exchange in glass and in particular what can be done to improve our first promising results in order to get near unity coupling between the optical bus and single photon emitters. We will show first results with semiconductor nanocrystals (NCs) but also using nitrogen-vacancy and silicon-vacancy defects in nanodiamond. The very first step in of our approach consists in the design of the structured waveguide using electromagnetic FDTD. We demonstrated that it is possible to achieve more than 90% coupling. In practice, before using coloured centres in diamond, we started working with CdSe/ZnS semiconductor nanocrystals. So far, we use straight waveguides defined to be single modes at the nominal wavelength of the emission line of the nanoemitters. The positioning of nanoemitters is still a challenge to be achieved. We developed an original technique based on photopolymerisation of light where the nanocrystals are grafted into a light sensitive polymer and can be placed at adequate positions.