The successful development of future photonic quantum technologies will much depend on the possibility of realizing robust and scalable nanophotonic devices. These should include quantum emitters like on‐demand single‐photon sources and non‐linear elements, provided their transition linewidth is broadened only by spontaneous emission. However, conventional strategies to on‐chip integration, based on lithographic processes in semiconductors, are typically detrimental to the coherence properties of the emitter. Moreover, such approaches are difficult to scale and bear limitations in terms of geometries. Here an alternative platform is discussed, based on molecules that preserve near‐Fourier‐limited fluorescence even when embedded in polymeric photonic structures. 3D patterns are achieved via direct laser writing around selected molecular emitters, with a fast, inexpensive, and scalable fabrication process. By using an integrated polymeric design, detected photon counts of about 2.4 Mcps from a single cold molecule are reported. The proposed technology will allow for competitive organic quantum devices, including integrated multi‐photon interferometers, arrays of indistinguishable single‐photon sources, and hybrid electro‐optical nanophotonic chips.

In this manuscript we demonstrate the potential of a hybrid technology which combines single organic molecules as quantum light sources and dielectric chips. In particular, we discuss our approach based on evanescent coupling of dibenzoterrylene molecules to silicon nitride waveguides and show a coupling efficiency of up to 42 +/- 2% over both propagation directions. Our results open a novel path towards a fully integrated and scalable photon processing platform.

A major challenge in quantum technologies is the on-chip integration of quantum emitters in a way that can be scaled up and preserves the emitter coherence properties. In the unconventional platform presented by Costanza Toninelli and co-workers in article number 2000004, molecular single-photon sources are embedded in three-dimensional polymeric structures, obtained by direct laser writing. Anthracene nanocrystals doped with dibenzoterrylene chromophores (chemical structure in the zoom) are previously selected and integrated in a scalable way, without perturbing the emitter optical features. In particular, suspended waveguides are designed to route the emitted fluorescence towards convenient output modes while micro-dome solid immersion lenses efficiently redirect the emission enabling unprecedented collected single-photon rates from a cold molecule.

Solid-state quantum emitters are a mainstay of quantum nanophotonics as integrated single-photon sources (SPS) and optical nanoprobes. Integrating such emitters with active nanophotonic elements is desirable in order to attain efficient control of their optical properties, but it typically degrades the photostability of the emitter itself. Here, we demonstrate a tunable hybrid device that integrates state of the art lifetime-limited single emitters (line width ∼40 MHz) and 2D materials at subwavelength separation without degradation of the emission properties. Our device's nanoscale dimensions enable ultrabroadband tuning (tuning range >400 GHz) and fast modulation (frequency ∼100 MHz) of the emission energy, which renders it an integrated, ultracompact tunable SPS. Conversely, this offers a novel approach to optical sensing of 2D material properties using a single emitter as a nanoprobe.

Practical implementations of quantum technologies, ranging from optical quantum computing to metrological measurements, suffer from the lack of high-rate, on-demand sources of indistinguishable single photons.

The efficient interaction of light with quantum emitters is crucial to most applications in nano and quantum technologies. Effective excitation and collection are key ingredients for the use and manipulation of the generated single photons. We have recently demonstrated how single molecules as quantum emitters can be deposited in a planar optical antenna, resulting in a narrow radiation pattern and increased collection efficiency [1]. On-chip integration and miniaturization allows for minimized losses and tailored interaction. In the present contribution we demonstrate the deterministic integration in 3-dimensional polymeric structures of single quantum emitters close to the lifetime limit. This is achieved by 3D Laser Writing (3DLW) of commercial photoresists around self-assembled organic nanocrystals containing fluorescent molecules. Thanks also to the high 3D resolution of the two-photon absorption process, this solution offers a big advantage in terms of coupling efficiency of the emitted fluorescence to the photonic structure.

Solid-state single photon sources (SPSs) with narrow line width play an important role in many leading quantum technologies. Within the wide range of SPSs studied to date, single fluorescent molecules hosted in organic crystals stand out as bright, photostable SPSs with a lifetime-limited optical resonance at cryogenic temperatures. Furthermore, recent results have demonstrated that photostability and narrow line widths are still observed from single molecules hosted in a nanocrystalline environment, which paves the way for their integration with photonic circuitry. Polymers offer a compatible matrix for embedding nanocrystals and provide a versatile yet low-cost approach for making nanophotonic structures on chip that guide light and enhance coupling to nanoscale emitters. Here, we present a deterministic nanostructuring technique based on electron-beam lithography for shaping polymers with embedded single molecules. Our approach provides a direct means of structuring the nanoscale environment of narrow line width emitters while preserving their emission properties.

The successful development of future photonic quantum technologies heavily depends on the possibility of realizing robust, reliable and, crucially, scalable nanophotonic devices. In integrated networks, quantum emitters can be deployed as single-photon sources or non-linear optical elements, provided their transition linewidth is broadened only by spontaneous emission. However, conventional fabrication approaches are hardly scalable, typically detrimental for the emitter coherence properties and bear limitations in terms of geometries and materials. Here we introduce an alternative platform, based on molecules embedded in polymeric photonic structures. Three-dimensional patterns are achieved via direct laser writing around selected molecular emitters, which preserve near-Fourier-limited fluorescence. By using an integrated polymeric design, record-high photon fluxes from a single cold molecule are reported. The proposed technology allows to conceive a novel class of quantum devices, including integrated multi-photon interferometers, arrays of indistinguishable single photon sources and hybrid electro-optical nanophotonic devices.

We report on organic nanocrystals doped with tunable concentration of fluorescent molecules, grown with an easy and inexpensive method and performing as bright and photostable single-photon sources at both room and cryogenic temperatures.

The on-chip integration of quantum light sources and nonlinear elements constitutes a major step toward scalable photon-based quantum information processing and communication In this work we demonstrate the potential of a hybrid technology that combines organic molecule-based quantum emitters and dielectric chips consisting of ridge waveguides and grating far-field couplers. In particular, dibenzoterrylene molecules in thin anthracene crystals are used as single-photon sources, exhibiting long-term photostability, easy fabrication methods, almost unitary quantum yield, and lifetime-limited emission at cryogenic temperatures. We couple such single emitters to silicon nitride ridge waveguides, showing a coupling efficiency of up to 42 +/- 2% over both propagation directions. Our results open a novel path toward a fully integrated and scalable photon processing platform.

We employ mirror enhanced grating couplers as convenient output ports for ridge Si3N4 waveguide to detect single photons emitted from Dibenzoterrylene (DBT) molecules coupled into propagating modes at room temperature. The coupling ports are designed for waveguide structures on transparent silica substrates for light extraction from the chip backside. Thus the coupling ports enable contact free readout of the waveguide devices by imaging through the silica substrate. Optimized grating structures provide maximum out-coupling efficiency at 785nm (the central emission wavelength of DBT) with a bandwidth of 50 nm and fulfill mode-matching to a Gaussian mode in free space (FWHM ≈ 4μm). Covering fully etched grating devices with a Hydrogen silsesquioxane buffer layer and a gold mirror increase the coupling efficiency compared to bare grating structures. The maximum single coupler efficiency predicted by finite element simulations is 90% which reduces to 60% when adapted to fabrication constrains, whereas the average measured coupling efficiency is 35±5%. We employ such grating ports to read out optical waveguides designed for single-mode operation at λ=785 nm. DBT molecules are coupled evanescently to the waveguides and transport emitted single photon signals to the coupling region upon optical pumping. Using a Hanbury Brown and Twiss setup we observe pronounced antibunching with g(2)(0)=0.50±0.05 from the grating couplers by excitation (λ=767nm) of a single DBT molecule which confirms the quantum nature of the outcoupled fluorescent light.

Quantum technologies could largely benefit from the control of quantum emitters in sub-micrometric size crystals. These are naturally prone to integration in hybrid devices, including heterostructures and complex photonic devices. Currently available quantum emitters in nanocrystals suffer from spectral instability, preventing their use as single-photon sources for most quantum optics operations. In this work we report on the performances of single-photon emission from organic nanocrystals (average size of hundreds of nm), made of anthracene (Ac) and doped with dibenzoterrylene (DBT) molecules. The source has hours-long photostability with respect to frequency and intensity, both at room and at cryogenic temperature. When cooled to 3 K, the 00-zero phonon line shows linewidth values (50 MHz) close to the lifetime limit. Such optical properties in a nanocrystalline environment recommend the proposed organic nanocrystals as single-photon sources for integrated photonic quantum technologies.

Summary form only given. Efficient quantum light sources and non-linear optical elements at the few photon level are the basic ingredients for most applications in nano and quantum technologies. On the other hand, a scalable platform for quantum information and communication typically requires reliable light matter interfaces and on-chip integration. In this work we demonstrate the potential of a novel hybrid technology which combines single organic molecules as quantum emitters and dielectric chips, consisting of ridge waveguides and grating far-field couplers [1].Here the emitters are integrated by spin-coating onto the photonic chip. We demonstrate at room temperature the emission of single photons from DBT molecules into ridge waveguides with a branching ratio up to 40%. The overall single-photon source efficiency, including emission into the guided mode, propagation losses, and emission into a quasi-gaussian mode in free space, is estimated around 16%. These results are competitive with state-of-the-art single photon emission into propagating guided modes from solid state systems [4], while offering a novel platform with unprecedented versatility. Single waveguided photons can be readily processed on-chip or efficiently extracted into a quasi-gaussian mode in free space. We also discuss options to further improve the collection efficiency and applications to quantum optics [5] and to study manybody-induced quantum correlation effects [6].

We report on our recent progress in the study of single Dibenzoterrylene (DBT) molecules as single photon sources and nanoscale probes. We consider DBT molecules embedded in thin anthracene films, a system that allows stable single photon emission both at room and at cryogenic temperatures. We investigate the most important optical properties of the DBT:anthracene system as a whole. We then perform a full statistical study of the coupling between single DBT molecules by measuring the lifetimes of DBT both in the coupled and in the uncoupled case. The experimental results are framed into a simple universal scaling model, where the magnitude of coupling depends solely on universal parameters and on the distance d between the single emitter and the graphene monolayer. We apply this model to infer d and provide a proof of principle for a position ruler at the nanoscale [1].

In this study we lay the groundwork for a graphene-based fundamental ruler at the nanoscale. It relies on the efficient energy-transfer mechanism between single quantum emitters and low-doped graphene monolayers. Our experiments, conducted with dibenzoterrylene (DBT) molecules, allow going beyond ensemble analysis due to the emitter photo-stability and brightness. A quantitative characterization of the fluorescence decay-rate modification is presented and compared to a simple model, showing agreement with the $d^{-4}$ dependence, a genuine manifestation of a dipole interacting with a 2D material. With DBT molecules, we can estimate a potential uncertainty in position measurements as low as 5nm in the range below 30nm.