Conference Agenda

Upconversion luminescence enables single-molecule detection

through a nonlinear process converting NIR excitation into visible emission,

but its low quantum yield limits the performance, making nanoparticle- or

photonic-engineering approaches essential for emission enhancement. Hybrid

plasmonic–photonic crystal nanostructures facilitate enhancement by convert

ing dissipative in-plane plasmonic propagation into efficient, vertically redi

rected emission, compensating for metal ohmic losses. We present here a three

fold total enhancement enabled by a gold grating structure coupled to a multi

layer substrate. It offers a promising route toward highly resolved images and

directionally optimized collection of the emission.

The ability to dynamically control light at the nanoscale remains a central challenge in photonic device design, where optical properties are typically fixed at fabrication. Quantum materials, with their strongly correlated electronic and magnetic degrees of freedom, offer a compelling route to overcome this limitation. Here, we exploit CrSBr, a van der Waals antiferromagnetic semiconductor, as an active nanophotonic medium, demonstrating two complementary platforms that together illustrate the broad potential of this material class. First, we fabricate photonic crystal slabs from CrSBr and leverage its exceptionally large refractive index near excitonic resonances to engineer guided resonances with high Q-factors exceeding 1200, small mode volumes, and intrinsic strong light-matter coupling. These resonances are continuously tunable via external magnetic fields, realizing a new paradigm for reconfigurable nanophotonic cavities. Second, we integrate thin CrSBr flakes into silicon nitride waveguides, achieving up to 5 dB of optical attenuation from a 2-µm-long device, a 25–250× reduction in footprint compared to conventional modulators, through field-tunable excitonic absorption. Across both platforms, magnetic field control of CrSBr's excitons enables precise, in situ manipulation of photonic modes at near-visible and infrared wavelengths, establishing 2D magnets as a powerful building block for next-generation tunable photonic architectures.

We analyze coupled surface plasmon resonances in symmetric metal–dielectric–metal microcavities under total internal reflection using generalized Fresnel coefficients. A closed-form expression for the core normal flux shows that intracavity flux maxima coincide with transmission peaks, while reflectance resonances are slightly shifted by direct input-mirror reflection. Experiments at 800 nm with 40 nm Ag–air–Ag cavities in BK7 confirm the predicted resonances and thickness-dependent peak shifts

We develop a microscopic theory for the optical response of nearly 2D J-Aggregate films, including anisotropic excitonic polarizability, dipole-dipole interactions, dielectric screening, and electromagnetic retardation within a coupled-dipole mean-field framework. The model predicts three collective excitation branches: longitudinal and transverse in-plane modes and an out-of-plane mode. The in-plane branches coalesce into one at small wavevector but split at finite momentum, while the out-of-plane branch remains spectrally distinct due to anisotropy. We also analyse surface exciton polaritons (SEPs) using generalized boundary conditions for a polarizable two-dimensional sheet. The anisotropic response results in two TM-polarized SEP branches associated with in-plane and out-of-plane excitations, in contrast with conventional two-dimensional materials supporting a single TM polariton mode

We present the design of high-Q one-dimensional photonic crystal cavities with ad hoc number of frequency modes and controlled spectral distance. Integrated multi-mode operations such as frequency comb generation as well as single-wavelength operations are enabled by the presented design technique. Light confinement is achieved by applying the gentle confinement concept through the shaping of the width of the photonic structure. Control over the number of modes is obtained by interrupting at will the variation of the width of the cavity. Experimental demonstration of single-mode lasing at telecom wavelength with a side mode suppression ratio of 40 dB is reported within an integrated InP-based PhC cavity nanolaser.

We compute the dipole response of an interacting electron gas from Path Integral Monte Carlo simulations. We perform a comparison to the Drude model, the phenomenological version of the noninteracting gas. Our results match the Drude model from an ensemble perspective to errorbars within 1%.