Controlling all Degrees of Freedom of the Optical Coupling in Hybrid Quantum Photonics

Nanophotonic quantum devices can significantly boost light-matter interaction which is important for applications such as quantum networks. Reaching a high interaction strength between an optical transition of a spin system and a single mode of light is an essential step which demands precise control over all degrees of freedom of the optical coupling. While current devices have reached a high accuracy of emitter positioning, the placement process remains overall statistically, reducing the device fabrication yield. Furthermore, not all degrees of freedom of the optical coupling can be controlled limiting the device performance. Here, we develop a hybrid approach based on negatively-charged silicon-vacancy center in nanodiamonds coupled to a mode of a Si$_3$N$_4$-photonic crystal cavity, where all terms of the coupling strength can be controlled individually. We use the frequency of coherent Rabi-oscillations and line-broadening as a measure of the device performance. This allows for iterative optimization of the position and the rotation of the dipole with respect to individual, preselected modes of light. Therefore, our work marks an important step for optimization of hybrid quantum photonics and enables to align device simulations with real device performance.Comment: 20 pages, 7 figure

An electroluminescent and tunable cavity-enhanced carbon-nanotube-emitter in the telecom band

Emerging photonic information processing systems require chip-level integration of controllable nanoscale light sources at telecommunication wavelengths. Currently, substantial challenges remain in the dynamic control of the sources, the low-loss integration into a photonic environment, and in the site-selective placement at desired positions on a chip. Here, we overcome these challenges using heterogeneous integration of electroluminescent (EL), semiconducting carbon nanotubes (sCNTs) into hybrid two dimensional – three dimensional (2D-3D) photonic circuits. We demonstrate enhanced spectral line shaping of the EL sCNT emission. By back-gating the sCNT-nanoemitter we achieve full electrical dynamic control of the EL sCNT emission with high on-off ratio and strong enhancement in the telecommunication band. Using nanographene as a low-loss material to electrically contact sCNT emitters directly within a photonic crystal cavity enables highly efficient EL coupling without compromising the optical quality of the cavity. Our versatile approach paves the way for controllable integrated photonic circuits

Interlaboratory study on Sb2S3 interplay between structure, dielectric function, and morphous-to-crystalline phase change for photonics

Antimony sulfide, Sb2S3, is interesting as the phase-change material for applications requiring high transmission from the visible to telecom wavelengths, with its band gap tunable from 2.2 to 1.6 eV, depending on the amorphous and crystalline phase. Here we present results from an interlaboratory study on the interplay between the structural change and resulting optical contrast during the amorphous-to-crystalline transformation triggered both thermally and optically. By statistical analysis of Raman and ellipsometric spectroscopic data, we have identified two regimes of crystallization, namely 250_C % T < 300_C, resulting in Type-I spherulitic crystallization yielding an optical contrast Dn _ 0.4, and 300 % T < 350 _ C, yielding Type-II crystallization bended spherulitic structure with different dielectric function and optical contrast Dn _ 0.2 below 1.5 eV. Based on our findings, applications of on-chip reconfigurable nanophotonic phase modulators and of a reconfigurable high-refractive-index core/phase-change shell nanoantenna are designed and proposed.The authors acknowledge the support from the European Union’s Horizon 2020 research and innovation program (No 899598 - PHEMTRONICS)

Purcell-enhanced emission from individual SiV− center in nanodiamonds coupled to a Si3N4-based, photonic crystal cavity

Hybrid quantum photonics combines classical photonics with quantum emitters in a postprocessing step. It facilitates to link ideal quantum light sources to optimized photonic platforms. Optical cavities enable to harness the Purcell-effect boosting the device efficiency. Here, we postprocess a free-standing, crossed-waveguide photonic crystal cavity based on Si3N4 with SiV− center in nanodiamonds. We develop a routine that optimizes the overlap with the cavity electric field utilizing atomic force microscope (AFM) nanomanipulation to attain control of spatial and dipole alignment. Temperature tuning further gives access to the spectral emitter-cavity overlap. After a few optimization cycles, we resolve the fine-structure of individual SiV− centers and achieve a Purcell enhancement of more than 4 on individual optical transitions, meaning that four out of five spontaneously emitted photons are channeled into the photonic device. Our work opens up new avenues to construct efficient quantum photonic devices

Controlling All Degrees of Freedom of the Optical Coupling in Hybrid Quantum Photonics

Nanophotonic quantum devices can significantly boost light–matter interaction, which is important for applications such as quantum networks. Reaching a high interaction strength between an optical transition of a spin system and a single mode of light is an essential step that demands precise control over all degrees of freedom of the optical coupling. While current devices have reached a high accuracy of emitter positioning, the placement process remains overall statistically, reducing the device fabrication yield. Furthermore, not all degrees of freedom of the optical coupling can be controlled, limiting the device performance. Here, we develop a hybrid approach based on negatively charged silicon vacancy center in nanodiamonds coupled to a mode of a Si3N4-photonic crystal cavity, where all terms of the coupling strength can be controlled individually. We used the frequency of coherent Rabi oscillations and line-broadening as a measure of the device performance. This allows for iterative optimization of the position and rotation of the dipole with respect to individual preselected modes of light. Therefore, our work marks an important step for optimization of hybrid quantum photonics and enables us to align device simulations with real device performance

Narrow Line Width Quantum Emitters in an Electron-Beam-Shaped Polymer

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.We would like to thank Josep Canet Ferrer and Vittoria Finazzi. This project has received funding from the EraNET Cofund Initiatives QuantERA under the European Union’s Horizon 2020 research and innovation programme grant agreement No. 731473 (Project acronyme: ORQUID). C.C. acknowledges financial support by the ICFOstepstone - PhD Programme for Early-Stage Researchers in Photonics, funded by the Marie Skłodowska-Curie Co-funding of regional, national, and international programmes (GA665884) of the European Commission. C.D. acknowledges financial support by the European Union’s Horizon 2020 research and innovation programme (ERC Grant No. StG637116). A.L. and E.B. acknowledge “Ente cassa di risparmio di Firenze” for financial support given for the acquisition of the TESCAN GAIA3 electron microscope , and Regione Toscana for the project FELIX (POR FESR 2014-2020, grant number no. 6455). We also acknowledge financial support from the Spanish Ministry of Economy and Competitiveness (MINECO), through the “Severo Ochoa” Programme for Centres of Excellence in R&D (SEV-2015-0522 and SEV-2015-0496), support by Fundaciò Cellex Barcelona, Generalitat de Catalunya through the CERCA program. This work received funding from the European Union’s Horizon 2020 research and innovation program Quantum Flagship (Grant No. 820378). Funded by the Agency for Management of University and Research Grants (AGAUR) 2017 SGR 1656.Peer reviewe