arXiv subjects

Ivan Sinev

Publications and source records attributed to Ivan Sinev.

12 recordsLinked to original sources

arXiv2026

Optical Control of Chirality by Ultrafast Symmetry Breaking in Membrane Metasurfaces

Chirality underpins a wide range of light-matter interactions, yet methods for its dynamic control in photonic systems remain limited. Here, we demonstrate ultrafast all-optical control of chirality in silicon metasurfaces through transient symmetry breaking. Our approach exploits photonic eigenstates of opposite spatial parity engineered to be highly susceptible to symmetry perturbations. Optical excitation generates free carriers that establish a transient refractive-index gradient across the membrane thickness, breaking out-of-plane mirror symmetry and facilitating hybridization of the parity-opposite modes into chiral photonic states. This enables the reversible creation and modulation of chirality on a 10-100 ps timescale, manifested by pronounced changes in the metasurface circular dichroism. By dynamically reconfiguring a fundamental symmetry property of the photonic structure rather than merely its optical response, our work establishes a route towards ultrafast control of chiral light-matter interactions and opens opportunities for active nanophotonic and information processing technologies.

physics.optics↗

arXiv2026

Nonlinear chiral response governed by meta-atom rotation

Chiral photonics provides powerful routes for controlling the light handedness, yet nonlinear chiral responses are typically associated with intricate three-dimensional systems. Here, we demonstrate that strong nonlinear chirality can emerge and be precisely tuned in planar metasurfaces. We study free-standing membrane metasurfaces composed of periodic lattices of tilted elliptic holes, which preserve out-of-plane mirror symmetry while breaking all in-plane mirror symmetries through the in-plane rotation of the meta-atoms. We demonstrate that optical resonances play a decisive role in governing the nonlinear chiral response, enabling pronounced circular dichroism in third-harmonic generation even when symmetry is broken only in plane. We experimentally reveal strong nonlinear chiral response from the metasurfaces and a striking swapping of nonlinear chiral channels for complementary meta-atom rotation angles. This behaviour arises from the interplay between lattice symmetry and meta-atom orientation, which controls the symmetry of the resonant modes and the resulting nonlinear selection rules. Our results establish meta-atom rotation as a powerful mechanism for engineering nonlinear chiral responses in planar metasurfaces, opening new opportunities for tunable chiral nonlinear metaphotonics devices.

physics.optics↗

arXiv2026

Digital nanophotonic biosensing empowered by silicon Mie voids

Optical biosensors are indispensable in medical and environmental diagnostics, yet existing approaches are fundamentally limited in their sensitivity due to ensemble-averaged measurements. Digital biosensing has emerged as a promising solution for resolving individual binding events, thereby providing signals at very low analyte concentrations down to the single-molecule level. Here, we present a novel concept for digital optical biosensing empowered by dielectric Mie voids, combining nanoparticle-based contrast enhancement and deep learning for ultrasensitive biomarker detection. The resonantly trapped light in the air cavities of the periodic Mie void arrays ensures strong overlap between the near-fields and the single gold nanoparticles that are captured on the surface in the presence of the protein biomarker. Remarkably, this strong interaction creates high-contrast digital signals for the precise counting of single nanoparticles located both within and outside the voids, yielding efficient use of the entire sensor area for high sensitivity. We employ deep-ultraviolet (DUV) lithography for the scalable and low-cost production of Mie voids in silicon wafers and automated image analysis with a convolutional neural network for robust nanoparticle counting. As a proof of our concept, we demonstrate the detection of an important disease biomarker, interleukin-6 (IL-6), from small sample volumes at concentrations as low as 1.84 pg/ml, within the physiological range of healthy individuals. Owing to its scalability, precision, and adaptability, our digital nanophotonic biosensing approach based on silicon Mie voids establishes a versatile route for applications ranging from bioanalytics to health and environmental monitoring.

physics.optics↗

arXiv2026

Infrared photonics for healthcare: A roadmap for proactive and predictive health management

The field of infrared (IR) photonics is currently undergoing remarkable progress, moving rapidly towards practical sensing applications demanded by medical therapy and diagnostics (theranostics). The Developments can be divided into three main categories: (i) novel devices and measurement concepts including advanced updates of classical approaches that push medical sensing into the spotlight; (ii) new demonstrations of photonic integrated circuit (PIC-)based IR devices enabling highly miniaturized sensors for point-of-care application as well as medical and wellness wearables; and (iii) technologically-mature IR demonstrators that enable first medical sensing and treatment applications. This roadmap paper provides a consolidated overview of this highly dynamic and interdisciplinary research field with a focus on the major roadblocks that limit the widespread adoption of IR photonics in large-scale medical diagnostics. Special attention is given to the ambivalence between the molecular-level spectroscopic interpretation and a broader health-state assessment, highlighting the need for a common framework. Additionally, the paper discusses the critical importance of unified measurement standards, calibration protocols, and medical certification processes to ensure the validity of experimental results, reproducibility, and clinical trust, particularly when novel experimental techniques and AI algorithms are involved. Perspectives from major past and current contributors to application-oriented IR photonics will be provided.

physics.app-ph↗

arXiv2025

Metasurface-Enhanced Mid-Infrared Imaging Spectroscopy with Broadband Quantum Cascade Lasers

Mid-infrared (mid-IR) spectroscopy offers unparalleled opportunities in sensing through chemically specific detection of molecular absorption fingerprints. Yet, its practical applications are limited by the weak light-matter interaction in the mid-IR range and low brightness of mid-IR light sources. Surface-enhanced infrared absorption (SEIRA) spectroscopy addresses the sensitivity limitations by leveraging resonant photonic structures, in particular, plasmonic and frequency-selective dielectric metasurfaces. However, current implementations of SEIRA approach mainly rely on complex instruments and scanning components such as Fourier-transform infrared spectroscopy and tunable external cavity quantum cascade lasers (EC QCLs). Here, we present a compact and high-throughput imaging-based SEIRA platform that combines broadband gradient metasurfaces with a radiofrequency-modulated QCL that generates remarkably broad instantaneous emission spectrum (250 cm$^{-1}$) covering absorption bands of multiple distinct molecular vibrational modes. By matching the resonance spectrum of the compact (1 mm$^2$) broadband gradient metasurface with the laser emission projected on its surface through a dispersive element, we ensure that every QCL spectral component is uniquely addressed for an efficient targeted enhancement of the electromagnetic field. This enables us to use a low-cost and room-temperature mid-IR camera, acquiring in a single frame the enhanced absorption signatures of analytes deposited on the metasurface as a barcode image, thus reducing the acquisition time by up to 3 orders of magnitude compared to the FTIR and EC QCL based measurements. Eliminating the need for tunable light sources, bulky spectrometers, and expensive low-temperature detectors, our approach enables high-throughput, miniaturized, and highly specific molecular diagnostics for diverse chemical and biological applications.

physics.optics↗

arXiv2025

Mid-IR Light Modulators Enabled by Dynamically Tunable Ultra High-Q Silicon Membrane Metasurfaces

Metasurfaces have emerged as a powerful platform to control free-space light at the subwavelength scale, enabling applications in sensing, lasing, nonlinear optics, and quantum photonics. However, their practical deployment is hindered by two key limitations: a tradeoff between low-Q resonances and weak amplitude contrast, and their predominantly static nature allowing only passive functionalities. These challenges are further aggravated in the application-relevant mid-infrared (mid-IR) range, where the lack of suitable low-loss materials and the strong absorption of common substrates such as silicon oxide or sapphire severely constrain performance and scalability. Here, we address these issues with actively tunable single-crystalline silicon membrane metasurfaces that combine high-Q resonances, strong amplitude contrast, and wafer-scale fabrication compatible dimensions for high throughput manufacturing. Our platform achieves record-high measured Q-factors up to 3000 in the mid-IR spectrum, supporting efficient dynamic modulation through two distinct schemes: (i) on-chip electro-thermal tuning via Joule heating, sustaining 50% modulation depth at CMOS-compatible voltages and speeds up to 14.5 kHz, and (ii) ultrafast all-optical modulation via carrier generation in silicon, reaching nanosecond response times and estimated sub-GHz modulation rates. By uniting sharp resonances, strong contrast, large-scale manufacturability, and dynamic tunability, our active silicon membrane metasurfaces advance the frontier of mid-IR nanophotonics and open new opportunities in sensing, free-space communication, thermal radiation management, and quantum technologies.

physics.optics↗

arXiv2025

Unconventional high-harmonic generation in resonant membrane metasurfaces

High-harmonic generation (HHG) in solids has rapidly emerged as a promising platform for creating compact attosecond sources and probing ultrafast electron dynamics. Resonant metasurfaces are essential for enhancement of the otherwise small harmonic generation efficiency through local field enhancement and are essential to circumvent the need of phase matching constraints. Until now, the metasurface-enhanced HHG was believed to follow the conventional integer-power scaling laws that hold for non-resonant bulk HHG. Here, we discover that highly resonant metasurfaces driven by quasi-bound states in the continuum break this principle, manifesting non-integer intensity dependencies of the generated harmonic powers. We show experimentally and theoretically that these unconventional nonlinearities arise from the high-Q resonances that generate local fields strong enough to substantially alter the contribution of higher order susceptibility tensors to the effective nonlinearities of the system. Our findings reveal how harmonic generation rooted in resonant field-driven modification of effective nonlinear susceptibilities can reshape our understanding of light-matter interaction at the nanoscale.

physics.optics↗

arXiv2024

Chirality encoding in resonant metasurfaces governed by lattice symmetries

Chiral metasurfaces provide invaluable tools capable of controlling structured light required for biosensing, photochemistry, holography, and quantum photonics. Here we suggest and realize a universal strategy for controlling the chiral response of resonant metasurfaces via the interplay of meta-atom geometry and lattice arrangements within all five possible planar Bravais symmetries. By introducing chiral gradient metasurfaces, we illustrate how our approach allows producing a predictable chiral response tunable by simple parameter variations. We highlight that symmetry-controlled chiral response provides an additional degree of freedom in optical signal processing, and showcase this with simultaneous mid-IR image encoding in two fundamental quantities, transmission and circular dichroism. Our proposed concept represents a universal toolkit for on-demand design and control of chiral metastructures that has potential for numerous applications in life sciences, quantum optics and more.

physics.optics↗

arXiv2023

Thermo-optical bistability enabled by bound states in the continuum in silicon metasurfaces

The control of light through all-optical means is a fundamental challenge in nanophotonics and a key effect in optical switching and logic. The optical bistability effect enables this control and can be observed in various planar photonic systems such as microdisk and photonic crystal cavities and waveguides. However, the recent advancements in flat optics with wavelength-thin optical elements require nonlinear elements based on metastructures and metasurfaces. The performance of these systems can be enhanced with high-Q bound states in the continuum (BIC), which leads to intense harmonic generation, improved light-matter coupling, and pushes forward sensing limits. In this study, we report on the enhanced thermo-optical nonlinearity and the observation of optical bistability in an all-dielectric metasurface membrane with BICs. Unlike many other nanophotonic platforms, metasurfaces allow for fine control of the quality factor of the BIC resonance by managing the radiative losses. This provides an opportunity to control the parameters of the observed hysteresis loop and even switch from bistability to optical discrimination by varying the angle of incidence. Additionally, we propose a mechanism of nonlinear critical coupling that establishes the conditions for maximal hysteresis width and minimal switching power, which has not been reported before. Our work suggests that all-dielectric metasurfaces supporting BICs can serve as a flat-optics platform for optical switching and modulation based on strong thermo-optical nonlinearity.

physics.optics↗

arXiv2023

Spectral tuning of high-harmonic generation with resonance-gradient metasurfaces

High-index dielectric subwavelength structures and metasurfaces are capable of enhancing light-matter interaction by orders of magnitude via geometry-dependent optical resonances. This enhancement, however, comes with a fundamental limitation of a narrow spectral range of operation in the vicinity of one or few resonant frequencies. Here we tackle this limitation and introduce an innovative and practical approach to achieve spectrally tunable enhancement of light-matter interaction with resonant metasurfaces. We design and fabricate {\it resonance-gradient metasurfaces} with varying geometrical parameters that translate into resonant frequencies dependence on one of the coordinates of the metasurface. The metasurfaces are composed of bone-like nanoresonators which are made of germanium, and they support high-$Q$ optical resonances in the mid-IR spectral range. We apply this general concept to observe the resonant enhancement of the $3^{\text{rd}}$ and $5^{\text{th}}$ harmonics generated from the gradient metasurfaces being used in conjunction with a tunable excitation laser to provide a wide spectral coverage of resonantly-enhanced tunable generation of multiple optical harmonics.

physics.optics↗

arXiv2020

Experimental observation of topological exciton-polaritons in transition metal dichalcogenide monolayers

The rise of quantum science and technologies motivates photonics research to seek new platforms with strong light-matter interactions to facilitate quantum behaviors at moderate light intensities. One promising platform to reach such strong light-matter interacting regimes is offered by polaritonic metasurfaces, which represent ultrathin artificial media structured on nano-scale and designed to support polaritons - half-light half-matter quasiparticles. Topological polaritons, or 'topolaritons', offer an ideal platform in this context, with unique properties stemming from topological phases of light strongly coupled with matter. Here we explore polaritonic metasurfaces based on 2D transition metal dichalcogenides (TMDs) supporting in-plane polarized exciton resonances as a promising platform for topological polaritonics. We enable a spin-Hall topolaritonic phase by strongly coupling valley polarized in-plane excitons in a TMD monolayer with a suitably engineered all-dielectric topological photonic metasurface. We first show that the strong coupling between topological photonic bands supported by the metasurface and excitonic bands in MoSe2 yields an effective phase winding and transition to a topolaritonic spin-Hall state. We then experimentally realize this phenomenon and confirm the presence of one-way spin-polarized edge topolaritons. Combined with the valley polarization in a MoSe2 monolayer, the proposed system enables a new approach to engage the photonic angular momentum and valley degree of freedom in TMDs, offering a promising platform for photonic/solid-state interfaces for valleytronics and spintronics.

cond-mat.mes-hall↗

arXiv2019

All-Dielectric Silicon/Phase-Change Optical Metasurfaces with Independent and Reconfigurable Control of Resonant Modes

All-dielectric metasurfaces consisting of arrays of nanostructured high-refractive-index materials, typically Si, are re-writing what is achievable in terms of the manipulation of light. Such devices support very strong magnetic, as well as electric, resonances, and are free of ohmic losses that severely limit the performance of their plasmonic counterparts. However, the functionality of dielectric-based metasurfaces is fixed-by-design, i.e. the optical response is fixed by the size, arrangement and index of the nanoresonators. A far wider range of applications could be addressed if active/reconfigurable control were possible. We demonstrate this here, via a new hybrid metasurface concept in which active control is achieved by embedding deeply sub-wavelength inclusions of a tuneable chalcogenide phase-change material within the body of high-index Si nanocylinders. Moreover, by strategic placement of the phase-change layer, and switching of its phase-state, we show selective and active control of metasuface resonances. This yields novel functionality, which we showcase via a dual- to mono-band meta-switch operating simultaneously in the O and C telecommunication bands.

physics.optics↗