In order to design high Purcell-factor systems, hybrid cavity-antenna systems have shown to be highly promising. We show in what way a system of a high-Q cavity combined with a low-V antenna can outperform its constituents, and give rules of thumb for their design for several applications. In particular, we will present experimental results of different hybrid systems including microdisk resonators and integrated photonic crystal nanobeams coupled to rod and dimer antennas respectively. By placing single quantum dots, we experimentally measure the high Purcell factors these systems promise.
We report on experiments where high-Q silicon nitride microdisks couple to arrays of plasmon antennas. Such hybrids promise `best of both world’ performances, i.e., subwavelength mode volume yet high Q, with exciting repercussions for spontaneous emission control, sensing, and plasmon-enhanced Raman scattering. In this framework it is particularly interesting to understand antenna-antenna interactions mediated through a resonant cavity. In a first experiment we examine cooperative dipole-dipole coupling of antenna dimers coupled through a whispering gallery mode, and demonstrate implications for high-Purcell factors with `chiral’, properties, i.e., unidirectional circulation. In a second experiment we studied far-field OAM generation by rings of antennas on cavities, demonstrating simultaneous pure OAM and pure polarization control through unit-cell design. Finally we report on the potential of such structures for molecular optomechanics.
Historically, strong light-matter interaction is achieved by using either high quality factor (Q) micro-resonators such as photonic crystal cavities which enable long photon lifetimes, or metallic nanoresonators which allow for strong field enhancements provided by localized plasmon resonances. However, it has been recently demonstrated that a hybrid system, which combines both a dielectric cavity and a dipolar plasmonic antenna, can achieve stronger emission enhancements than the cavity or antenna alone [ACS Photonics, 3 (10) (2016)].
We propose to use arrays of N plasmonic antennas to further engineer the directionality of this enhanced emission. We analyze the resonant mode structure and local density of states in high-Q hybrid plasmonic-photonic resonators composed of a dielectric disk, perturbed by dimers of plasmon antennas, systematically swept in position through the cavity mode. A simple cavity-perturbation-theory model shows how the degenerate clockwise and anticlockwise whispering gallery modes (WGMs) of the unperturbed cavity split into two new hybrid modes with different complex eigenfrequencies, showing an interesting evolution of the resonance frequencies and Q's as the antenna spacing is varied. We find that one may construct large LDOS enhancements exceeding those given by a single antenna, which are `chiral' in the sense of correlating with unidirectional injection into the cavity. We report an experiment probing the resonances of silicon nitride (Si3N4) microdisks decorated with Aluminium antenna dimers that confirms the predicted mode properties as function of antenna spacing.