DELICACY

Optical cavities have been studied and used in many different contexts. Miniaturized cavities can be found in laser diodes and kilometers long ones in gravitational wave experiments. They also emerged as fundamental tools to control the light-matter interaction at an unprecedented level in the framework of cavity Quantum Electro Dynamics (cQED). The design of new cavities is still an active research field, mainly to improve linear or nonlinear light-matter interaction. At the level of a single (or few) emitter, light-matter interaction can be greatly enhanced with high-quality factor (Q) and small mode volume (V) optical cavities, with several applications such as nano-laser, low-power nonlinear optics, ultra-sensitive detection of biological molecules, cryptography or quantum computing... The strength of these effects typically scales as the ratio Q/V, where the effective quality factor (Q) is the lowest of those of the cavity an those of the emitter. Hence, two main approaches have emerged to maximize cavity effects: the plasmonic approach where V can be extremely small due to wavelength compression, but at the expense of Q because of the losses in the metals, and the dielectric approach where V is limited to a fraction of ?^3 due to diffraction but with very high values of Q. The realization of an optical cavity combining both a strongly sub-wavelength mode volume and a high quality factor is currently an open challenge of photonics which would unlock the access to new regimes of light-matter interaction and would open the door to new physics. This is the first objective of DELICACY. In the framework of cQED, nano-cavities exhibit their full potential when coupled to an individual quantum nano-emitter. The deterministic coupling of a nano-emitter to a cavity is usually a difficult task, which is sometimes solved on a trial and error basis, requiring the fabrication of a large number of devices. Here, we tackle this challenge on a deterministic approach: the cavity geometry is designed from the beginning to be as flexible as possible for efficient coupling to the emitter. To this end, the cavity architecture will be based on a flexible Fiber Fabry Perot (FFP) cavity. To reach sub-diffraction mode volume a purely dielectric nano-antenna that acts as a field “concentrator” will be integrated in the center of the cavity. The second objective of the DELICACY project is to efficiently couple a single nano-emitter to this innovative flexible cavity, combining high-quality factor, deeply sub-diffraction mode volume. Among the vast choice of possible quantum emitters, from cold atoms or ions to solid-state defects, graphene quantum dots (GQDs), synthesized via the bottom-up approach, emerge as a new player that combines a high brightness, room temperature operation, as well as great potential in terms of control of the intrinsic properties and adaptability towards targeted application, through the flexibility of the chemical synthesis. To exemplify the power of this innovative system, we propose to demonstrate the realization of an efficient, room temperature, tunable, single photon source, to perform highly sensitive single molecule absorption spectroscopy and to reach the strong coupling regime. For these objectives, DELICACY brings together complementary specialists in chemical synthesis (CEA-NIMBE), photo-physics of nano-objects (LUMIN) and micro-cavities and cQED with nano-emitters (LPENS ).