This PDF file contains the front matter associated with SPIE Proceedings Volume 13110, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

Recent advancements in ultrafast electron microscopy have provided direct access to polariton dynamics, visualizing such dynamics in space and time. This work presents new experimental results revealing a myriad of phenomena involving interactions of vortex-anti-vortex pairs, their creation and annihilation. We show new behaviors that became accessible thanks to a new development in electron microscopy - Free-Electron Ramsey Imaging (FERI) - which enabled extracting both the sub-cycle and group dynamics of polariton wavepackets. Our demonstrations involve optical phonon-polaritons in hexagonal boron nitride (hBN) and Molybdenum oxide, renowned for their unique dispersion and novel wavepacket propagations behaviors. These discoveries not only enhance our understanding of vortex phenomena across various systems, but also offer promising avenues for accessing new kinds of light-matter interactions.

Plasmonic Parametric Resonance (PPR) provides a novel method to excite plasmonic modes that are typically difficult to access by direct illumination due to linear or angular momentum mismatch between the modes and the incident field. By temporally modulating the permittivity near a plasmonic structure, PPR enables energy transfer into these modes, overcoming the constraints of energy and momentum conservation. This paper reviews the theory of PPR, explores its implementation via three-wave mixing interactions, and discusses applications in optical limiting through reverse saturable absorption processes. Additionally, we present a time-domain perturbation formalism to address pump saturation, depletion effects, and cascaded second-order nonlinear interactions, highlighting the potential for intermodal conversion.

Recent advances indicate that enhanced light-matter interaction in plasmonic nanocavities can create hybrid properties in integrated plasmonic metal nanostructures and soft materials. Here, by integrating polyelectrolytes and surface ligands in gold nanorod-on-mirror nanocavities and detecting the nanocavity resonance and vibrational Raman scattering simultaneously, we found that the plasmon-vibration interaction modifies both the nanocavity and molecular responses. Large enhancement of Raman scattering accompanied by the plasmon resonance linewidth broadening are observed as the laser-plasmon detuning approaches the CH vibrational frequency of the molecular systems in the nanocavities. The experimental observations are consistent with the molecular optomechanics theory that predicts dynamical backaction amplification of the vibrational modes and high sensitivity of Raman scattering when the plasmon resonance overlaps with the Raman emission frequency. The results presented here suggests that molecular optomechanics coupling may be manipulated for creating hybrid properties based on quantum mechanical interaction of molecular oscillators and nanocavity electromagnetic optical modes.

Exciton-polaritons (EPs) are an emerging approach to achieve strong light-matter coupling and robust quantum phenomena, with application to areas such as photonic neuromorphic computing for instance reservoir computing. 2D transition metal dichalcogenides (TMDs) are promising candidates to host EPs due to their potential for strong coupling as evidenced by large Rabi splitting energies, which in the case of few-layer MoS2 has been demonstrated to reach 293 meV when coupled to the C exciton, placing it in the ultrastrong coupling regime, at room temperature. Here we examine how the Rabi splitting of CVD-grown monolayer MoS₂ in a cavity can be optimized by tuning two variables: cavity geometry (thickness of silver and dielectric spacers) and the targeted exciton for coupling (A at about 1.9 eV, B at about 2.06 eV, or C at about 2.9 eV). With the cavity geometry, there is a tradeoff between optical field confinement and transmission. With the targeted exciton, there may be a tradeoff between Rabi splitting and lifetime. Transfer matrix simulations are used to inform how thick the cavity layers need to be, and at what angle measurements should be performed, to achieve Rabi splitting at a certain exciton energy. Experimentally, the Rabi splitting is measured by placing the cavity at a specified angle and measuring the optical reflectance and transmittance. By fitting the data, we find Rabi splittings of 124 meV, 194 meV, and 288 meV for the A, B, and C excitons, respectively, which places them in the strong, and on the edge of the ultrastrong, coupling regime.

In this work, we used effective medium approximation and the Drude-Lorentz model with one oscillator for transparent conducting oxide optical permittivity to design multilayered stacks of transparent conducting oxides and dielectrics. The influence of the material parameters for the multilayered metamaterial on nonlinearity and higher-order dispersion are presented. The finite-difference time domain (FDTD) numerical simulations are used to investigate the pulse propagation at the ENZ spectral point. The results based on a full wave analysis study performed using FDTD numerical algorithm show a dramatic pulse shaping for femtosecond pulses at the epsilon-near-zero spectral point.

We report recent developments in Bragg soliton dynamics on an ultra-silicon-rich nitride chip, including gap soliton-based tunable slow light and pure quartic Bragg solitons.

In recent years, non-Hermitian degeneracies, so-called exceptional points, have attracted immense attention in photonics and optics. Among a range of interesting fundamental aspects, exceptional points have great potential for applications, such as topological mode switching, non-reciprocal devices, and ultrasensitive sensors. Although the research on exceptional points has grown enormously in the last years, the construction of high-order exceptional points, where more than two eigenfrequencies and corresponding modes coalesce, is still challenging.

We tackle this challenge by a robust implementation of high-order exceptional points in microring cavities. To do so, we combine the known mirror-induced asymmetric backscattering with the unidirectional coupling between microcavities via adjacent waveguides. We investigate the topology of eigenfrequencies around the exceptional points and demonstrate a cavity-selective sensing scheme. Our numerical results are also intuitively described by effective Hamiltonians. Our scheme allows for the robust and scalable construction of high-order exceptional points in integrated semiconductor platforms.

We propose to achieve sensitive, low-noise, and fast detection of incoherent thermal photons using a novel optomechanical spring sensing principle. In this unique active sensing approach, the coherent optomechanical oscillation (OMO) greatly amplifies the long-wavelength-infrared (LWIR)-induced eigenspectrum modification, leading to a noise-equivalent power (NEP) of < 0.07pW/Hz^1/2. Meanwhile, our detection signal bandwidth is only determined by the frequency-demodulation circuit, which can reach > 100kHz. Both performance parameters are revolutionary and significantly above the current state of the art. Our success, based on mature photonic integrated circuit platforms, can easily scale up to multipixel arrays.

Heterogeneous integration of new materials promises to significantly expand the range of capabilities accessible by silicon photonic integrated circuits (PICs). However, the classical integration protocols, which involves etching trenches through the backend-of-the-line (BEOL) layers to access the PIC for subsequent material bonding or deposition, face severe limitations in integration capacity, packaging density, and process complexity. Moreover, the inability to utilize the BEOL layers is a major missed opportunity for innovative 2.5-D photonic device designs. In this talk, we will unveil a new, universal heterogeneous integration platform: Substrate-inverted Multi-Material Integration Technology (SuMMIT). The SuMMIT integration scheme leverages advanced wafer-scale 3-D packaging technologies such as through-Si vias and direct bond interconnects to enable seamless integration of non-CMOS materials.

We propose the use of a periodic set of dielectric rods considered in the high frequency regime as a reservoir for computing. We show that such a system presents a chaotic behavior that can be analyzed within the K.A.M. approach, with the formation of tori in phase space. The conditions for which the system can be used to encode information is then addressed. Finally, we try to extend these ideas to quantum metamaterials and investigate the possibility of using these structures for quantum reservoir computing.

We experimentally study the spectral lasing response of on-chip InP network random lasers under illumination of different input image shapes. Deep-learning models have become increasingly omipresent throughout society. However, they are blighted by exponentially soaring energy demands. Physical implementations of neural networks are emerging as an attractive solution for performing machine learning more energy-efficiently than conventional GPU hardware by mimicking the complex structure of biological brains. However, not many platforms which can natively receive unprocessed raw image data as light have so far been demonstrated – a highly-appealing approach which deserves attention. Here, we demonstrate an optical system with spectral response to image input. Specifically, we report on designable solid-state InP network random lasers, based on random graph networks etched into wafer-bonded InP. The networks lase over a broad wavelength range and show a plethora of modes formed by multiple scattering paths. These modes are highly sensitive to illumination patterns due to their unique and highly overlapping spatial distribution.

Phase change materials (PCM) have gained a considerable interest in the photonics community as active materials in reconfigurable devices. Their significant change of optical properties upon the amorphous to crystalline reversible phase transition enables a large and dynamical tuning of devices’ response. Among the various PCM, Ge₂Sb₂Te₅ (GST) is the most widely used thanks to its fast phase change as well as the large modulation of its refractive index (Δn > 1). Although this PCM has been mainly exploited for simple binary on-off functions, it presents an additional degree of freedom: the multi-level partial change of state. Indeed, we show in this paper multi-level continuously tunable reflectivity allowed by the electrically-controlled partial crystallization of GST. This is achieved via the Joule effect, by injecting short voltage pulses (few tens of μs) through platinum microheaters underneath GST patches. This electrically-induced phase transition is the most promising strategy for PCM integration in industrial foundries and shows promises for individual pixel addressing in multi-level applications such as neuromorphic computing or grayscale displays.

We introduce multilayer structures with the phase-change material (PCM) germanium-antimony-tellurium (GST) for use as broadband switchable absorbers in the infrared wavelength range. We use a memetic optimization algorithm to optimize both the material composition and the layer thicknesses of the structures. We show that in the optimized structures near perfect absorption can be switched to very low absorption in a broad wavelength range by switching GST from its crystalline to its amorphous phase. In addition, we show that our design approach can be used for switchable radiative cooling based on PCMs. We also introduce multilayer structures based on PCMs for reconfigurable structural color generation. These structures generate multiple colors within a single pixel by switching between the two phases of the PCM. Our design approach leads to maximally distinct colors with large distances between them on the International Commission on Illumination (CIE) chromaticity diagram. Our optimized lithography-free structures have better performance than harder-to-fabricate three-dimensional structures. Our results could pave the way to novel switchable absorbers and multicolor pixels.

We present an analytical formalism to predict the minimal thickness of a film, with an intrinsic absorption resonance, required to perfectly absorb all incident light. We show that on resonance, perfect absorption can be achieved at thicknesses well below one-thousandth of a free-space wavelength. The developed analytical formalism is validated numerically using rigorous coupled wave analysis and finite element techniques, and experimentally using thin-film superlattices of tin-doped indium oxide nanocrystals with collective plasmon resonances mimicking the absorption resonances considered in our analytical model. We further consider perfectly absorbing structures consisting of thin, non-resonant, but high loss, films, and show that perfect absorption can often only be achieved at film thicknesses well below what can be fabricated experimentally. We overcome this limitation by introducing the concept of thin-film dilution, and show, analytically, numerically, and experimentally, that these diluted films can accurately mimic the theoretical optical properties of nanometer, or even sub-atomic, thickness films. This work provides a path towards the rational design of ultra-thin absorbers for bolometric or non-linear optical applications.

This work presents a numerical investigation into the performance metrics of photodetectors made from monolayer MoS2, a two-dimensional material with unique optoelectronic properties. The study introduces a one-dimensional drift-diffusion framework along with wave propagation in layered media analysis. Results demonstrate a peak quantum efficiency at 561 nm, influenced by the substrate. The precision of the model validates its utility for characterizing MoS2 photodetectors, emphasizing the importance of background inclusion in calculations. The efficient computation makes the model suitable for in-depth device analysis.

This study explores a novel photodetector based on the binary topological insulator bismuth selenide (Bi2Se3), leveraging its unique surface conduction properties and high surface-to-volume ratio. Unlike previous research focusing on heterojunctions, we investigate the intrinsic polarization selectivity of Bi2Se3. Our experimental results demonstrate a stable responsivity of 22.6 A/W under a -0.6 V bias voltage with 860 nm laser illumination and a polarization-sensitive switching of 10.9 dB. The device exhibits sensitivity across the near-infrared spectrum, showcasing its potential for applications in low-noise imaging, environmental monitoring, and optical communication. Additionally, the high polarization sensitivity paves the way for promising applications in non-destructive material assessment, hardware security enhancement, and secure communication systems.

We present an experimental and numerical investigation of a sub-threshold optoelectronic oscillator (OEO) subject to injection from an external RF signal. A time-delayed numerical model is introduced and the agreement with experiments is discussed. The sub-threshold OEO exhibits frequency selective RF amplification. The OEO sensitivity is investigated for different subthreshold internal gain values. As the internal gain of the system increases and the oscillation threshold is approached, the OEO exhibits larger amplification of an injected RF signal. When the injected RF signal is on resonance, the OEO exhibits a maximum RF gain of approximately 28 dB near 0.5% below threshold. Furthermore, the injected RF signal frequency is scanned, and the amplified response is measured. Finally, we highlight the role of the intrinsic time-delay within the OEO’s temporal response to a pulsed, injected RF signal.

A large mechanical sensitivity can be achieved by a mechanically tunable quantum tunneling barrier. The tunneling resistance across the nanometer-sized gap can be changed by several orders of magnitude through a sub-angstrom-scale displacement. Here, we demonstrate the performance of a strain sensor formed from pre-stretched Platinum (Pt) on PDMS, where perturbation of the thickness of the nanogap cracks due to strain change the resistance of the device. A gauge factor >500 is realized in a device that is mechanically stabilized by self-assembled monolayer (SAM). Then, we extend the application of the nanogap based strain sensor to temperature and infrared detection. Fabricated proof-of-concept metal/SAM/metal suspended bolometers yield a temperature coefficient of resistance (TCR) between -0.006 K^-1 and - 0.085 K^-1, and theoretical predictions show that with further optimization the TCRs could be improve to as much as -2.7 K^-1, which is more than one order of magnitude better than the state-of-the-art VO_x bolometers. Furthermore, this work quantifies the 50 Hz to 10 kHz noise performance of suspended metal/nanogap/metal bolometers and compares the noise spectrum of devices with and without SAM, as well as 10 nm Pt channel vs. 30 nm Pt channel devices. Finally, early stage 830 nm optical measurements show that the device sensitivity of a 10nm Pt / air nanogap / 10 nm Pt peaks at low bias (< 1V, <20 pA) and that the 3dB point of the sensor extends past 10 kHz. The experimental results of this work suggest that nanogap-based sensor architectures exhibit a high sensitivity and may also enable fast response time detectors.

We present experimental, numerical, and analytical investigations of two time-delayed coupled optoelectronic oscillators (OEOs). Results demonstrate that bifurcation and exceptional point analyses can be combined to yield novel system predictions and behavior of interacting, nonlinear, time-delayed systems. Our model rate equations are developed by generalizing an established single OEO model to incorporate arbitrary coupling terms between the two OEOs. We focus on the case where the OEOs are independently on resonance and the cross-couplings are equal in magnitude and 180 degrees out of phase - experimentally achieved with a 180 degree hybrid coupler. To extract analytical predictions, we apply a linearized slowly varying envelope approach to derive a set of time-delayed linear rate equations. The OEO’s inherent time delay results in a transcendental characteristic equation. In distinct operating regimes, we find pairs of analytical eigenvalue solutions. Analytical solutions allow us to identify the boundaries that separate operation regimes. At the first bifurcation boundary, where the eigenvalues cross the imaginary axis, the OEO starts to self-oscillate in both experiment and simulation. An exceptional boundary is indicated by a coalescence of the eigenvalues and eigenfunctions along with a transition from purely real to complex eigenvalues. Where the bifurcation and exceptional boundaries intersect, experiment and simulation show that the coupled OEO has an enhanced output power sensitivity and marks a clear frequency splitting. This splitting experimentally manifests as two distinct single-frequency states, which correspond to the imaginary components of the linearized eigenvalues. This frequency splitting gives novel control over the operating frequency of the coupled OEO system via the coupling strengths. Finally, we discuss the relevance of the time scale separation, which allows phase control of the complex couplings.

Lingulodinium polyedra is a microalga capable of producing toxins with antibacterial, antitumoral, and antifungal properties. Our aim was to internalize molybdenum trioxide nanoparticles (MoO₃NPs) into the microalgae Lingulodinium polyedra, leveraging the optical properties of MoO₃NPs to enhance its solar absorption and other mechanisms such as charge carriers in its photosynthetic system, thereby increasing redox reactions during the photosynthesis process. Molybdenum nanoparticles (MoNPs) were synthesized using the Laser Ablation of Solids in Liquids (LASL) method with ultrashort pulse lasers. MoNPs were characterized by UV-Vis spectroscopy, Raman spectroscopy, and Transmission Electron Microscopy (TEM). Notably, the MoNPs exhibited interesting optical properties, including an absorption peak around 800 nm, identified as a plasmonic band absorption. Using the Tauc model for semiconductors, we determined the band gap energy to be approximately 2.7 eV. We compared the evolution of MoNPs in distilled water and sterilized seawater (SSW). Over time, both environments led to the formation of MoO₃ nanoparticles (MoO₃NPs), with the MoNPs in distilled water showing a significantly different absorption spectrum compared to those in SSW. Furthermore, MoNPs were internalized into the microalgae L. polyedra. Growth curve analyses revealed that treatments with MoO₃NPs resulted in increased cell density and a longer lifespan compared to untreated algae. Additionally, through Multiple Reaction Monitoring (MRM), characteristic molecular compounds of pectenotoxins (PTXs) were detected exclusively in the dinoflagellates that internalized the MoO₃ nanoparticles.

We introduce multilayer structures based on phase-change materials (PCMs) for reconfigurable structural color generation. These structures can achieve multiple colors within a single pixel. Our optimized structures with a single PCM layer generate two distinct colors by switching between the two phases of the PCM. Similarly, our optimized structures with two PCM layers generate four distinct colors. To achieve maximally distinct colors in the two-color structures, we maximize the distance between the color coordinates on the International Commission on Illumination (CIE) chromaticity diagram. Similarly, in the four-color structures we maximize the minimum distance between the coordinates of the four colors. We use a memetic optimization algorithm to optimize both the material composition and the layer thicknesses of the multilayer structures. To achieve different colors, we consider several PCMs. We find that our design approach leads to large distances between the generated colors on the CIE diagram. Our results could lead to a new class of single-cell multicolor pixels with no power consumption required to retain each color, making them appealing for low refresh rate displays.