Hugo M. Doeleman

Antenna–Cavity Hybrids: Matching Polar Opposites for Purcell Enhancements at Any Linewidth

Strong interaction between light and a single quantum emitter is essential to a great number of applications, including single photon sources. Microcavities and plasmonic antennas have been used frequently to enhance these interactions through the Purcell effect. Both can provide large emission enhancements: the cavity typically through long photon lifetimes (high

Experimental observation of a polarization vortex at a bound state in the continuum (Conference Presentation)

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Hybrid plasmonic-photonic resonators(Conference Presentation)

), and the antenna mostly through strong field enhancement (low mode volume

Perturbing open cavities: Anomalous resonance frequency shifts in a hybrid cavity-nanoantenna system

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Experimental observation of a polarization vortex at an optical bound state in the continuum

). In this work, we demonstrate that a hybrid system, which combines a cavity and a dipolar antenna, can achieve stronger emission enhancements than the cavity or antenna alone. We show that such systems can be used as a versatile platform to tune the bandwidth of enhancement to any desired value, while simultaneously boosting emission enhancement. Our fully consistent analytical model allows to identify the underlying mechanisms of boosted emission enhancement in hybrid systems, which include radiation damping and constructive interference between multiple-scattering paths. Additionally, we find excellent agreement between strongly boosted enhancement spectra from our analytical model and from finite-element simulations on a realistic cavity-antenna system. Finally, we demonstrate that hybrid systems can simultaneously boost emission enhancement and maintain a near-unity outcoupling efficiency into a single cavity decay channel, such as a waveguide.

Trapping Light in Plain Sight: Embedded Photonic Eigenstates in Zero‐Index Metamaterials

Bound states in the continuum (BICs) are modes that, although energy and momentum conservation allow coupling to far-field radiation, do not show any radiation loss. As such, energy can theoretically be stored in the mode for infinite time. Such states have been shown to exist for e.g. photonic and acoustic waves, and show great promise for applications including lasing, (bio)sensing and filtering. Despite intense research, the mechanism behind these states and their robustness is still poorly understood. Recently it was proposed theoretically that BICs occur at points where the far-field polarization of the radiated waves shows a vortex, i.e. points where the polarization is undefined [1]. Due to the integer winding number associated to such vortices, the modes should be topologically protected against disorder. In this work, we verify this claim experimentally. We fabricate a SiN grating and use reflection measurements to show that it supports an optical BIC around 700 nm wavelength. We then perform polarimetry measurements in a Fourier reflection microscopy scheme to map the far-field polarization at every angle and wavelength, demonstrating the existence of a vortex at the BIC. We use a simple dipole model to characterize the BIC as a Friedrich-Wintgen type, arising from the interference between two electromagnetic dipoles induced in the grating. Our method can be used to characterize the polarization structure of any leaky photonic mode, including those supporting polarization vortices of arbitrary winding numbers. [1] Zhen, B., et al. (2014). Physical review letters, 113(25), 257401.

Topological photonic crystals in the visible: Design and angle-resolved characterization of the bulk and edge states

Hybrid nanophotonic structures are structures that integrate different nanoscale platforms to harness light-matter interaction. We propose that combinations of plasmonic antennas inside modest-Q dielectric cavities can lead to very high Purcell factors, yielding plasmonic mode volumes at essentially cavity quality factors. The underlying physics is subtle: for instance, how plasmon antennas with large cross sections spoil or improve cavities and vice versa, contains physics beyond perturbation theory, depending on interplays of back-action, and interferences. This is evident from the fact that the local density of states of hybrid systems shows the rich physics of Fano interferences. I will discuss recent scattering experiments performed on toroidal microcavities coupled to plasmon particle arrays that probe both cavity resonance shifts and particle polarizability changes illustrating these insights. Furthermore I will present our efforts to probe single plasmon antennas coupled to emitters and complex environments using scatterometry. An integral part of this approach is the recently developed measurement method of `k-space polarimetry’, a microscopy technique to completely classify the intensity and polarization state of light radiated by a single nano-object into any emission direction that is based on back focal plane imaging and Stokes polarimetry. I show benchmarks of this technique for the cases of scattering, fluorescence, and cathodoluminescence applied to directional surface plasmon polariton antennas.