Events

Morning Session

10:45am: Tunable Hyperbolic Polaritons in 2D Materials

Giacomo Venturi, City University of New York

Polaritonic platforms capable of confining light below the diffraction limit hold immense promise for dense waveguiding and energy-efficient integrated photonics. While conventional isotropic materials support standard polaritonic modes, van der Waals (vdW) anisotropic crystals enable the excitation of hyperbolic polaritons, which feature open isofrequency contours (IFCs) and directional propagation with exceptionally high optical momenta. Accessing and dynamically tailoring these sub-diffractional modes from the far field is a vital frontier for scalable on-chip nanophotonics. In this work, we demonstrate two distinct, integration-compatible avenues for achieving dynamic, time-varying tunability of hyperbolic polaritons in 2D material stacks utilizing linear grating couplers to overcome momentum mismatch.
First, we present a magneto-optical switch utilizing the vdW magnetic semiconductor chromium sulfide bromide (CrSBr). Below its Néel temperature (~130 K), CrSBr‬ is as an A-type antiferromagnet (AFM) with an exciton resonance strong enough to induce a negative dielectric permittivity, establishing an intrinsic hyperbolic window. By applying an out-of-plane magnetic field (‭B > 2 T‬‭‬‭‬), we drive a phase transition to a ferromagnetic (FM) state, shifting the exciton resonance and altering the IFC topology from open hyperbolas to closed ellipses. By fabricating a‬‭‬ grating on ‭CrSBr,‬ we can reversibly tune the far-field polaritonic coupling on and off, confirmed by a pronounced reflection dip in the AFM state that vanishes switching to FM. Direct Fourier imaging microscopy captures this field-driven topological transition.
Second, we unlock ultrafast optical tuning of hyperbolic plasmon-polaritons in ‭molybdenum oxide dichloride (MoOCl2‬) using a similar grating configuration. With an intense optical pump pulse, we drive sub-ps carrier distribution changes that modulate the effective electron mass, actively changing the material's photonic modes. 
Together, these platforms establish versatile knobs for tuning polaritonic dispersion.

11:00am: Colloidal Quantum Dot Based Integrated Gain

Reed Thomson, Columbia University

Within the field of integrated photonics, a major loss bottleneck remains for the coupling between fibers and waveguides integrated on chips. To overcome this loss, significant progress has been made toward developing fully integrated laser sources, so that fiber-to-chip coupling is not necessary for power input. However, much of this work involves complicated, non-CMOS-compatible fabrication involving III-V material integration, limiting scalability. We explore a different approach, leveraging recent advancements from the field of colloidal quantum dots, in which soluble materials have exhibited remarkably long gain lifetimes. Colloidal quantum dots have historically been plagued by short gain lifetimes around 100 ps, but a novel Type (I+II) architecture has recently achieved gain lifetimes of 19 ns [2]. Because this gain lifetime is long compared to the photon lifetime of high-quality factor silicon nitride ring resonators in the visible regime [1], Type (I+II) colloidal quantum dots can sustain optical gain over the many round trips a photon makes within the ring, enabling fully integrated low threshold lasing. This approach is also remarkably simple to fabricate. We begin by following the standard silicon nitride waveguide process, with e-beam lithography followed by a fluorine-based plasma etch. We then define windows where the rings are located using photoresist and deposit the Type (I+II) colloidal quantum dot material by drop-casting, evenly cladding the waveguide resonators with the gain material locally. As a result, we have achieved a gain source directly integrated into our high-Q resonators, with only a simple post processing step.

[1] Mateus Corato-Zanarella, Xingchen Ji, Aseema Mohanty, and Michal Lipson, "Absorption and scattering limits of silicon nitride integrated photonics in the visible spectrum," Opt. Express 32, 5718-5728 (2024)
[2] Hahm, D., Kim, C., Dang, T. H. et al. Low-threshold lasing from colloidal quantum dots under quasi-continuous-wave excitation. Nat. Photon. (2025).
 

11:15am: Simulating realistic cavities with QEDFT

Leon Orlov-Sullivan, City University of New York

Recent experiments have shown that strong light-matter coupling can significantly influence chemical reactivity, energy transfer, and photochemical processes. One promising theoretical approach to understanding light-matter coupling is quantum-electrodynamical density-functional theory (QEDFT), which extends density-functional theory (DFT) to strongly coupled light-matter systems. The recently introduced photon many-body dispersion (pMBD) functional accounts for the anisotropic properties of materials and incorporates long-range correlation energy through higher-order corrections[1]. While QEDFT has advanced our understanding of light–matter interactions, existing studies have not incorporated realistic cavity setups. To address this limitation, Svendsen et al. [2] introduced a macroscopic-QED (MQED) framework that captures complex cavity geometries and dissipative effects.
Here, we apply QEDFT with the pMBD functional to explore how molecular properties change under realistic cavity setups. Using the MQED approach, we can directly calculate the coupling strength and mode frequencies of experimentally relevant Fabry–Pérot cavities and spherical microcavities, allowing us to model observable, tunable effects of strong light–matter coupling. Our results provide a path toward quantitatively connecting ab initio theory with polaritonic chemistry experiments.

[1] C. Tasci, L.A. Cunha, and J. Flick, Phys. Rev. Lett., 134, 073002 (2025).
[2] M.K. Svendsen, K.S. Thygesen, A. Rubio, and J. Flick, J. Chem. Theory Comput., 20 (2), 926-936, (2024).

11:30am: Pulsed Optomechanics with Microfabricated High-Overtone Bulk Acoustic Wave Resonators

Bulent Kanmaz, Yale University

Microfabricated high-overtone bulk acoustic wave resonators (μHBARs) provide a robust solid-state platform for realizing quantum control of high-frequency mechanical excitations. These systems exhibit exceptional thermal anchoring and negligible optical absorption, enabling efficient photon–phonon coupling and long-lived mechanical modes under cryogenic operation. Building upon our recent demonstration of ground-state laser cooling of ultra-massive (7.5 μg) acoustic modes, we investigate the temporal dynamics of key processes such as thermal repopulation and laser-induced cooling in this platform using pulsed optomechanical protocols. By applying precisely timed optical cooling pulses followed by time-resolved thermometry, we aim to quantify phonon population decay, coherence times, and the recovery dynamics that govern quantum state stability. Access to this pulsed regime provides a new experimental understanding for exploring non-stationary optomechanical interactions, offering insight into transient phonon dynamics and establishing the foundation for controllable, time-domain quantum operations and long-lived storage protocols in bulk acoustic systems.

11:45am: Photon Many-Body Dispersion for Materials: A Method for Studying Cavity Modified van der Waals Interactions

Mohammad Hassan, City University of New York

In polaritonic chemistry, strong light-matter interactions between matter and cavity photons have
been experimentally shown to modify physical and chemical properties. Here, of particular interest is the
cavity-induced modification to weak inter- and intramolecular interactions. The recent development of
the photon many-body dispersion (pMBD) method [1], an exchange-correlation functional in quantum
electrodynamical density-functional theory (QEDFT), has made possible the ab initio study of cavity-
induced van der Waals interactions for molecules under strong light-matter coupling. We extend the
pMBD method to the study of material systems. We then use this extension of pMBD to study bilayer
graphene and hBN, along with other heterostructures. We show that pMBD can accurately capture
effects that arise in the context of strong light-matter interactions, such as anisotropic electron-photon
interactions, beyond single-photon effects, and cavity-modulated van der Waals interactions. Moreover,
we show that this extension allows for efficient k-point sampling of the unit cell for the ab initio study
of experimentally relevant systems.

12:00pm: Distilled Remote Entanglement between superconducting qubits across optical channels

Nicolas Dirnegger, University of California Los Angeles

A promising quantum computing architecture comprises modules of superconducting quantum processors linked via optical channels using quantum transducers. As quantum transducer hardware improves, a need has arisen to understand the quantitative relationship between transducer-device characteristics and the strength of the resulting remote entanglement. Using Monte Carlo simulations that incorporate 2-to-1 and 3-to-1 entanglement distillation methods, our model maps transducer device performance up to system-level channel performance, thereby allowing the performance of remote entanglement approaches to be compared and optimized. We find the extreme photon loss (EPL) distillation protocol to be particularly high performing. Moreover, even without distillation, present-day transducers with added noise of photons are at the threshold of enabling remote Bell pairs with fidelities exceeding 50%. If the next generation of transducers can improve by 3 orders of magnitude in added noise, efficiency, and repetition rates, then they would allow for remote two-qubit gates achieving 99.7% fidelities at MHz rates. These results set practical targets for transducers to be ready for deployment into modular quantum computing systems.

12:15pm: Green stripes in a scarab beetle arise from a multiscale photonic architecture: a subsurface array of photonic crystal slabs

Nicola Kubzdela, Columbia University

Vivid colours in nature often arise from photonic nanostructures that have inspired diverse technologies. Yet most known examples fall within a limited set of structural themes. Here, we describe a biologically and optically unusual structure in the bright green, violin-shaped stripes of the fiddler beetle Eupoecila australasiae. The green colour is produced by a composite, hierarchical structure comprising dense arrays of microscopic, fin-like elements located beneath the cuticle. Each vertical fin, decorated with complementary lattices of nanospheres and indentations, resembles two photonic crystal slabs mounted on a solid central core. Modelling shows that the fins are strongly iridescent, reflecting longer wavelengths near the normal and shorter wavelengths at oblique angles. However, disorder in fin orientation and filtering by the overlying cuticle converts the opaline cyan appearance of the fins into the bright diffuse green seen externally. Our work expands the known diversity of biological photonic nanostructures and offers new inspiration for biomimetic designs.   

Afternoon Session

3:30pm: Controlling integrated photonic chips like a display

Martin Stein, Yale University

While free-space light propagation can be dynamically controlled with many degrees of freedom using spatial light modulators (SLMs), post-fabrication tuning on photonic chips is usually severely limited by the number of physical electrodes. I will present our work sidestepping this bottleneck to enable high-dimensional and free-form control on integrated platforms by "virtual electrodes" projected onto chips by SLM technology. We fabricated silicon nitride and lithium niobate waveguides that are electro-optically controlled by projecting structured illumination patterns onto an overlying photoconductive layer. Using this approach, we have demonstrated a large optical neural network in lithium niobate (Onodera et al., 2025) and programmable spatio-spectral nonlinear processes in silicon nitride (Yanagimoto et al., 2025). Finally, I will discuss promising theoretical findings whose realization may be enabled by this free-form control paradigm, offering a route to scale optical computing devices.

3:45pm: Blinking Silver Nanoparticles

Haydee Pacheco, Rutgers University

In this work, we investigate the intrinsic luminescence blinking behavior of silver nanoparticles (AgNPs) using single-particle spectroscopy combined with X-ray photoelectron spectroscopy (XPS) and finite-difference time-domain (FDTD) simulations. We examine blinking phenomena at green and red emission wavelengths and correlate them with surface composition, particle size, and substrate conditions. Time-resolved optical measurements reveal size-dependent blinking dynamics, where smaller AgNPs (50–90 nm) exhibit intermittent emission, while larger particles (>120 nm) display continuous photoluminescence. XPS analysis uncovers shifts in the Ag 3d, O 1s, and C 1s core levels, indicating the formation of silver oxides and carbonates on blinking samples. These surface species, together with crystallization-induced changes in the electronic and crystal structure, are linked to modifications in blinking characteristics. Additionally, chromium interlayers are found to suppress blinking, and FDTD simulations suggest that this stabilization is associated with a passivation of scattering behavior. Overall, our findings highlight the surface-sensitive and substrate-dependent nature of AgNP blinking and provide new insights into the mechanisms governing plasmon-enhanced photoluminescence. These results hold promise for the rational design of plasmonic nanostructures for applications in sensing, imaging, optoelectronics, and anti-counterfeiting technologies.
Keywords: silver nanoparticles, blinking behavior, photoluminescence, time-resolved microscopy, XPS analysis

4:00pm: Measuring High-Order Spatial Derivatives of Vertical Gravity Field by Stacking Atom Interferometers

Mariam Mchedlidze, Rutgers University - Newark

Light-pulse atom interferometry has been widely used to measure fundamental physics constants and test the laws of physics. Nowadays, compact atom interferometers have been developed to measure local gravity and the gravity gradient with high sensitivity and accuracy. Beyond the gravity gradient, the third-order derivative of the gravity field, the so-called gravity curvature, is sensitive to the changes in density. If made transportable, such measurements will open the door for providing horizontal resolutions in mining exploration and detecting near-surface or shallow density structures. We aim to develop a compact atomic gravimeter and implement atom interferometers at three vertically separated heights, obtaining gravity, gradient, and gravity curvature measurements simultaneously. These measurements are currently limited to being laboratory-based due to the complexity of the setup. We demonstrated a magneto-optical trap inside a back-to-back conical mirror for 87Rb atoms and implemented a vertical atom interferometer, with the capability to scale it into three atom interferometers using a single laser beam. We developed a compact and versatile laser system, compatible with 780-nm diode and 1560-nm fiber lasers to produce all the frequencies for laser cooling, driving Raman transition, and detecting atoms. We are assembling a 1-meter-long vacuum chamber to demonstrate three simultaneous atom interferometers using a single laser beam and constructing a transportable platform for gravity surveys.

4:15pm: Third Harmonic Generation Using an Integrated Distributed Bragg Reflector Cavity

James Eckstein, Columbia University

Distributed Bragg reflector (DBR) cavities are a promising platform for on-chip nonlinear optics. By combining pump enhancement in a DBR cavity with optimized modal phase matching to the third harmonic, we measure 385 μW of on-chip third-harmonic power, corresponding to a total conversion efficiency of 0.041%.

4:30pm: Narrow-linewidth telecom C-band emission from erbium-implanted diamond 

Sounak Mukherjee, Princeton University

Color centers in solid-state hosts are promising platforms for quantum networks. By virtue of its intra-4f transition, Er3+ is the only defect observed so far emitting in the telecom C-band, which exhibits the lowest fiber-optic loss for long-distance quantum communication. Thus, erbium-doped materials have gained significant interest as a spin-photon interface. Diamond offers several advantages as a host, including a low magnetic-noise environment, high Debye temperature, and wide bandgap. However, Er3+ incorporation into diamond is challenging as its large ionic radius induces strain and lattice damage. In this work, we report telecom C-band emission from erbium-implanted diamond, with the principal transition at 1508 nm and an inhomogeneous ensemble linewidth of ~90 GHz. This is enabled by a high-pressure high-temperature annealing process that preserves near-surface implanted layers and mitigates lattice disorder. The optical lifetime is observed to be ~3 µs. From temperature dependence of photoluminescence, we assign the lowermost crystal-field levels and identify multiple sites. Zeeman splitting of the optical transitions at high magnetic fields reveals information about the g-factor anisotropy and site symmetry. Finally, by comparing the experimental results with crystal field theory, we tentatively assign the dominant site to a split-vacancy configuration of erbium in diamond.

4:45pm: C̶i̶r̶c̶u̶l̶a̶r̶ Hyperbolic Bragg Grating

Emroz Khan, City University of New York

Polaritons present new degrees of freedom in tailoring light at the nanoscale through its rich dispersion assortment in natural anisotropic crystals. Of particular interest are the surface phonon polaritons with in-plane hyperbolicity that show high-quality propagation of deep-subwavelength directional modes on the interface of many low-symmetry van der Waals materials. To harness their supremacy over traditional diffraction-limited light, one, however, first needs to simultaneously excite all polaritonic states lying on the hyperbolic dispersion.

So far, success with line gratings has been inherently limited because they can excite only a single state, determined by their pitch and orientation. Here, to couple far-field radiation with the entire hyperbolic branch, which is crucial for many field confinement applications and engineering of local density of states, we present a new class of surface structure that acts as the hyperbolic analog of a bullseye grating. The resulting grating gets its design blueprint from the two-dimensional inverse Fourier transform of the dispersion hyperbola, and owing to the smooth variation of local pitch and orientation, the grating transfers the correct momenta in all directions, concomitantly.

A realistic implementation of the proposed grating excites all hyperbolic polariton states on a calcite substrate when illuminated with normally incident radiation at the design frequency. The absorption spectrum shows high coupling efficiency with a very high quality factor. The grating also exhibits strong angular selectivity in absorption and a rich anisotropic structure in its emission pattern. Additionally, the grating focuses incident field at its center which leads to emission enhancement from single molecules. The proposed hyperbolic Bragg grating opens a new route to far-field polaritonic control in an all-dielectric environment with a broad range of potential applications, from integrated photonics to quantum emitter design.