Showing papers in "ACS Photonics in 2022"
TL;DR: The concept of optical bound states in the continuum (BICs) underpins the existence of strongly localized waves embedded into the radiation spectrum that can enhance the electromagnetic fields in subwavelength photonic structures as mentioned in this paper .
Abstract: The concept of optical bound states in the continuum (BICs) underpins the existence of strongly localized waves embedded into the radiation spectrum that can enhance the electromagnetic fields in subwavelength photonic structures. Early studies of optical BICs in waveguides and photonic crystals uncovered their topological properties, and the concept of quasi-BIC metasurfaces facilitated applications of strong light-matter interactions to biosensing, lasing, and low-order nonlinear processes. Here we employ BIC-empowered dielectric metasurfaces to generate efficiently high optical harmonics up to the 11th order. We optimize a BIC mode for the first few harmonics and observe a transition between perturbative and nonperturbative nonlinear regimes. We also suggest a general strategy for designing subwavelength structures with strong resonances and nonperturbative nonlinearities. Our work bridges the fields of perturbative and nonperturbative nonlinear optics on the subwavelength scale.
47 citations
TL;DR: In this paper , the authors provide a discussion on the unique functionalities of a microwave space-time-modulated metasurface, including spatiotemporal decomposition, scattering and diffraction, digital coding, non-reciprocal transmission, serrodyne frequency translation, pure frequency conversion, parametric wave amplification, and multifunctional operations.
Abstract: Over the past decade, static metasurfaces have proved to be low-profile and efficient apparatuses for transformation of electromagnetic waves. However, such metasurfaces are restricted by their reciprocal and time- and frequency-invariant responses. To overcome these restrictions, space-time-modulated metasurfaces have recently been introduced for versatile, reciprocal/nonreciprocal, and frequency translation of electromagnetic waves. These are capable of changing both the momentum and energy of the incident wave and provide functionalities that are far beyond the capabilities of conventional static and reciprocal metasurfaces. This Perspective provides a discussion on the unique functionalities of a microwave space-time-modulated metasurface. In particular, we review various techniques that have been recently used for the realization of metasurfaces introducing spatiotemporal decomposition, scattering and diffraction, digital coding, nonreciprocal transmission, serrodyne frequency translation, pure frequency conversion, parametric wave amplification, and multifunctional operations. Although the paper focuses on microwave space-time metasurfaces, the described concepts can inspire realization of their optical counterparts.
42 citations
TL;DR: In this article , a generalized family of optical-analogous skyrmions, the Skyrme-Poincar\'e sphere, is proposed to visualize the topological evolution of tunable skyrms.
Abstract: In recent time, the optical-analogous skyrmions, topological quasiparticles with sophisticated vectorial structures, have received an increasing amount of interest. Here we propose theortically and experimentally a generalized family of these, the tunable optical skyrmion, unveiling a new mechanism to transform between various skyrmionic topologies, including N\'eel-, Bloch-, and antiskyrmion types, via simple parametric tuning. In addition, Poincar\'e-like geometric representation is proposed to visualize the topological evolution of tunable skyrmions, which we termed Skyrme-Poincar\'e sphere, akin to the spin-orbit representation of complex vector modes. To generate experimentally the tunable optical skyrmions we implemented a digital hologram system based on a spatial light modulator, showing great agreement with our theoretical prediction.
40 citations
TL;DR: In this paper , a tunable metasurface made of aluminum nanodisk array coated with ITO on a thin film of lithium niobate was demonstrated, and a spectral resonant shift of few nanometers and modulation contrast of ~40% were observed.
Abstract: We demonstrate a tunable metasurface made of aluminum nanodisk array coated with ITO on a thin film of lithium niobate. A spectral resonant shift of few nanometers and modulation contrast of ~40% are observed.
31 citations
TL;DR: In this article , the authors provide a map of the theoretical tools available to tackle chemical applications of molecular polaritons at different scales, and draw attention to both the successes and the challenges still ahead in the theoretical description of polaritonic chemistry.
Abstract: Polaritonic chemistry exploits strong light-matter coupling between molecules and confined electromagnetic field modes to enable new chemical reactivities. In systems displaying this functionality, the choice of the cavity determines both the confinement of the electromagnetic field and the number of molecules that are involved in the process. While in wavelength-scale optical cavities the light-matter interaction is ruled by collective effects, plasmonic subwavelength nanocavities allow even single molecules to reach strong coupling. Due to these very distinct situations, a multiscale theoretical toolbox is then required to explore the rich phenomenology of polaritonic chemistry. Within this framework, each component of the system (molecules and electromagnetic modes) needs to be treated in sufficient detail to obtain reliable results. Starting from the very general aspects of light-molecule interactions in typical experimental setups, we underline the basic concepts that should be taken into account when operating in this new area of research. Building on these considerations, we then provide a map of the theoretical tools already available to tackle chemical applications of molecular polaritons at different scales. Throughout the discussion, we draw attention to both the successes and the challenges still ahead in the theoretical description of polaritonic chemistry.
29 citations
TL;DR: This Perspective is aimed at piecing together the puzzle of SERS in biomarker monitoring, with a view on future challenges and implications, and addresses the most relevant requirements of plasmonic substrates for biomedical applications, as the implementation of tools from artificial intelligence or biotechnology to guide the development of highly versatile sensors.
Abstract: Future precision medicine will be undoubtedly sustained by the detection of validated biomarkers that enable a precise classification of patients based on their predicted disease risk, prognosis, and response to a specific treatment. Up to now, genomics, transcriptomics, and immunohistochemistry have been the main clinically amenable tools at hand for identifying key diagnostic, prognostic, and predictive biomarkers. However, other molecular strategies, including metabolomics, are still in their infancy and require the development of new biomarker detection technologies, toward routine implementation into clinical diagnosis. In this context, surface-enhanced Raman scattering (SERS) spectroscopy has been recognized as a promising technology for clinical monitoring thanks to its high sensitivity and label-free operation, which should help accelerate the discovery of biomarkers and their corresponding screening in a simpler, faster, and less-expensive manner. Many studies have demonstrated the excellent performance of SERS in biomedical applications. However, such studies have also revealed several variables that should be considered for accurate SERS monitoring, in particular, when the signal is collected from biological sources (tissues, cells or biofluids). This Perspective is aimed at piecing together the puzzle of SERS in biomarker monitoring, with a view on future challenges and implications. We address the most relevant requirements of plasmonic substrates for biomedical applications, as well as the implementation of tools from artificial intelligence or biotechnology to guide the development of highly versatile sensors.
29 citations
TL;DR: In this article , the authors highlight a few mistaken concepts and distinguish them from the many interesting works that continue to emerge from the fruitful marriage of terahertz with biology and medicine.
Abstract: Within the field of terahertz science and technology, one of the most active areas of current research focuses on the intersection of terahertz measurements and methods with the world of biology and medicine. Current activities revolve around numerous diverse questions, ranging from studies of the vibrational spectra of biomolecules and macromolecular complexes to biosensing to medical diagnostics based on noninvasive imaging techniques. Unlike many other areas in which terahertz science is now making inroads, this research domain has been plagued with a number of misleading ideas, which originated at least two decades ago and continue to crop up in current literature. In the worst case, these unfortunate notions can distract from, and even obscure, fascinating and meaningful results. The purpose of this Perspective is to highlight a few of these mistaken concepts and, more importantly, to distinguish them from the many interesting works that continue to emerge from the fruitful marriage of terahertz with biology and medicine.
28 citations
TL;DR: Toth et al. as mentioned in this paper proposed a site-specific fabrication of blue quantum emitters in hexagonal boron nitride hexagonal hexagonal BORON nitride.
Abstract: Site-specific fabrication of blue quantum emitters in hexagonal boron nitride Angus Gale1,#, Chi Li1,#, Yongliang Chen1, Kenji Watanabe2, Takashi Taniguchi3, Igor Aharonovich1,4, Milos Toth1,4* 1. School of Mathematical and Physical Sciences, University of Technology Sydney, Ultimo, New South Wales 2007, Australia 2. Research Center for Functional Materials, National Institute for Materials Science, Tsukuba 3050044, Japan 3. International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba 305-0044, Japan 4. ARC Centre of Excellence for Transformative Meta-Optical Systems, University of Technology Sydney, Ultimo, New South Wales 2007, Australia *Email: Milos.Toth@uts.edu.au
27 citations
TL;DR: In this paper , the main steps recently undertaken to achieve high quality photonic components, and outline some of the current challenges SiC faces to establish its relevance as a viable photonic technology.
Abstract: In the last two decades, bulk, homoepitaxial, and heteroepitaxial growth of silicon carbide (SiC) has witnessed many advances, giving rise to electronic devices widely used in high-power and high-frequency applications. Recent research has revealed that SiC also exhibits unique optical properties that can be utilized for novel photonic devices. SiC is a transparent material from the UV to the infrared, possess nonlinear optical properties from the visible to the mid-infrared and it is a meta-material in the mid-infrared range. SiC fluorescence due to color centers can be associated with single photon emitters and can be used as spin qubits for quantum computation and communication networks and quantum sensing. This unique combination of excellent electronic, photonic and spintronic properties has prompted research to develop novel devices and sensors in the quantum technology domain. In this perspective, we highlight progress, current trends and prospects of SiC science and technology underpinning the development of classical and quantum photonic devices. Specifically, we lay out the main steps recently undertaken to achieve high quality photonic components, and outline some of the current challenges SiC faces to establish its relevance as a viable photonic technology. We will also focus on its unique potential to bridge the gap between classical and quantum photonics, and to technologically advance quantum sensing applications. We will finally provide an outlook on possible alternative applications where photonics, electronics, and spintronics could merge.
26 citations
TL;DR: In this paper , a metasurface-coated two-dimensional (2D) slab waveguide enables the generation of arbitrary complex light fields by combining the extreme versatility and freedom on the wavefront control of optical metamurfaces with the compactness of photonic integrated circuits.
Abstract: We show that a metasurface-coated two-dimensional (2D) slab waveguide enables the generation of arbitrary complex light fields by combining the extreme versatility and freedom on the wavefront control of optical metasurfaces with the compactness of photonic integrated circuits. We demonstrated off-chip 2D focusing and holographic projection with our metasurface-dressed photonic integrated devices. This technology holds the potential for many other optical applications requiring 2D light field manipulation with full on-chip integration, such as solid-state LiDAR and near-eye AR/VR displays.
TL;DR: In this paper , the uncertainty of a temperature measurement with luminescent nanocrystals was predicted quantitatively using the measurement noise and background signal, and the predicted uncertainty matched the temperature uncertainties obtained from repeated measurements, over a wide temperature range (303 −473 K).
Abstract: Materials with temperature-dependent luminescence can be used as local thermometers when incorporated in, for example, a biological environment or chemical reactor. Researchers have continuously developed new materials aiming for the highest sensitivity of luminescence to temperature. Although the comparison of luminescent materials based on their temperature sensitivity is convenient, this parameter gives an incomplete description of the potential performance of the materials in applications. Here, we demonstrate how the precision of a temperature measurement with luminescent nanocrystals depends not only on the temperature sensitivity of the nanocrystals but also on their luminescence strength compared to measurement noise and background signal. After first determining the noise characteristics of our instrumentation, we show how the uncertainty of a temperature measurement can be predicted quantitatively. Our predictions match the temperature uncertainties that we extract from repeated measurements, over a wide temperature range (303–473 K), for different CCD readout settings, and for different background levels. The work presented here is the first study that incorporates all of these practical issues to accurately calculate the uncertainty of luminescent nanothermometers. This method will be important for the optimization and development of luminescent nanothermometers.
TL;DR: In this paper , a broadband nonvolatile electrically controlled 2 × 2 programmable unit in silicon photonics based on the phase change material Ge 2 Sb 2 Te 5 is presented.
Abstract: : Programmable photonic integrated circuits (PICs) have recently gained signi fi cant interest because of their potential in creating next-generation technologies ranging from arti fi cial neural networks and microwave photonics to quantum information processing. The fundamental building block of such programmable PICs is a 2 × 2 programmable unit , traditionally controlled by the thermo-optic or free-carrier dispersion. However, these implementations are power-hungry and volatile and have a large footprint (typically >100 μ m). Therefore, a truly “ set-and-forget ” -type 2 × 2 programmable unit with zero static power consumption is highly desirable for large-scale PICs. Here, we report a broadband nonvolatile electrically controlled 2 × 2 programmable unit in silicon photonics based on the phase-change material Ge 2 Sb 2 Te 5 . The directional coupler-type programmable unit exhibits a compact coupling length (64 μ m), small insertion loss ( ∼ 2 dB), and minimal crosstalk (< − 8 dB) across the entire telecommunication C-band while maintaining a record-high endurance of over 2800 switching cycles without signi fi cant performance degradation. This nonvolatile programmable unit constitutes a critical component for realizing future generic programmable silicon photonic systems.
TL;DR: Inverse design is poised to empower metasurface research by embracing fastgrowing artificial intelligence as discussed by the authors , and many research efforts have been devoted to enriching inverse design principles and applications.
Abstract: Conventional human-driven methods face limitations in designing complex functional metasurfaces. Inverse design is poised to empower metasurface research by embracing fastgrowing artificial intelligence. In recent years, many research efforts have been devoted to enriching inverse design principles and applications. In this perspective, we review most commonly used metasurface inverse design strategies including topology optimization, evolutionary optimization, and machine learning techniques. We elaborate on their concepts and working principles, as well as examples of their implementations. We also discuss two emerging research trends: scaling up inverse design for large-area aperiodic metasurfaces and end-to-end inverse design that co-optimizes photonic hardware and post-image processing. Furthermore, recent demonstrations of inverse-designed metasurfaces showing great potential in real-world applications are highlighted. Finally, we discuss challenges in future inverse design advancement, suggest potential research directions, and outlook opportunities for implementing inverse design in nonlocal metasurfaces, reconfigurable metasurfaces, quantum optics, and nonlinear metasurfaces.
TL;DR: In this article , the authors highlight recent and important advances in this newborn field of research, where the interactions and exchanges between theory and experiments are particularly strong, and clearly point toward future designs for all-optical chiral separation strategies of high potential.
Abstract: Optical forces are involved in many physical processes and are used routinely in the laboratory for manipulating and cooling matter, from the micro down to the quantum scales. It has been realized recently that new forms of optical forces can emerge when a chiral system is immersed within a chiral light field. These new forces involve not only the chirality of the system on which they exert their mechanical action, but the chirality itself of the optical field that generate them. As such, they have fascinating properties, the crucial one being that they are enantioselective. We will highlight recent and important advances in this newborn field of research, where the interactions and exchanges between theory and experiments are particularly strong. The key advances selected in this Perspective are representative of the vitality of the current research activity. These advances clearly point toward future designs for all-optical chiral separation strategies of high potential. They also shape new means for controlling chiral systems, such as atoms and molecules, at the quantum level. The viewpoint adopted in this Perspective overall aims at showing how chiral optical forces shed new light on chiral light–chiral matter interactions.
TL;DR: In this paper , the authors show that quadrumer nanoparticle lattices enable lasing in a quasi-BIC mode with a highly out-of-plane character, and they show that the lasing mode has a topological charge.
Abstract: Plasmonic lattices of metal nanoparticles have emerged as an effective platform for strong light–matter coupling, lasing, and Bose–Einstein condensation. However, the full potential of complex unit cell structures has not been exploited. On the other hand, bound states in continuum (BICs) have attracted attention, as they provide topologically protected optical modes with diverging quality factors. Here, we show that quadrumer nanoparticle lattices enable lasing in a quasi-BIC mode with a highly out-of-plane character. By combining theory with polarization-resolved measurements of the emission, we show that the lasing mode has a topological charge. Our analysis reveals that the mode is primarily polarized out-of-plane as a result of the quadrumer structure. The quality factors of the out-of-plane BIC modes of the quadrumer array can be exceedingly high. Our results unveil the power of complex multiparticle unit cells in creating topologically protected high-Q modes in periodic nanostructures.
TL;DR: In this paper , anisotropic PhPs supported by biaxial van der Waals (vdW) slabs are actively tuned by simply gating an integrated graphene layer, which enables controlling the canalization of PhPs along different in-plane directions in twisted heterostructures.
Abstract: Phonon polaritons (PhPs)─lattice vibrations coupled to electromagnetic fields─in highly anisotropic media display a plethora of intriguing optical phenomena, including ray-like propagation, anomalous refraction, and topological transitions, among others, which have potential for unprecedented manipulation of the flow of light at the nanoscale. However, the properties of these PhPs are intrinsically dictated by the anisotropic crystal structure of the host material. Although in-plane anisotropic PhPs can be steered, and even canalized, by twisting individual crystal slabs in a van der Waals (vdW) stack, active control of their propagation via external stimuli presents a significant challenge. Here, we report on a technology in which anisotropic PhPs supported by biaxial vdW slabs are actively tuned by simply gating an integrated graphene layer. Excitingly, we predict active tuning of optical topological transitions, which enable controlling the canalization of PhPs along different in-plane directions in twisted heterostructures. Apart from their fundamental interest, our findings hold promises for the development of optoelectronic devices (sensors, photodetectors, etc.) based on PhPs with dynamically controllable properties.
TL;DR: In this article , the optical constants of transition metal dichalcogenides (TMDs) were obtained using spectroscopic ellipsometry in the broad range of 300-1700 nm.
Abstract: Transition metal dichalcogenides (TMDs) attract significant attention due to their remarkable optical and excitonic properties. It was understood already in the 1960s and recently rediscovered that many TMDs possess a high refractive index and optical anisotropy, which make them attractive for nanophotonic applications. However, accurate analysis and predictions of nanooptical phenomena require knowledge of dielectric constants along both in- and out-of-plane directions and over a broad spectral range, information that is often inaccessible or incomplete. Here, we present an experimental study of optical constants from several exfoliated TMD multilayers obtained using spectroscopic ellipsometry in the broad range of 300–1700 nm. The specific materials studied include semiconducting WS2, WSe2, MoS2, MoSe2, and MoTe2, as well as in-plane anisotropic ReS2 and WTe2 and metallic TaS2, TaSe2, and NbSe2. The extracted parameters demonstrate a high index (n up to ∼4.84 for MoTe2), significant anisotropy (n∥ – n⊥ ≈ 1.54 for MoTe2), and low absorption in the near-infrared region. Moreover, metallic TMDs show potential for combined plasmonic–dielectric behavior and hyperbolicity, as their plasma frequency occurs at around ∼1000–1300 nm depending on the material. The knowledge of optical constants of these materials opens new experimental and computational possibilities for further development of all-TMD nanophotonics.
TL;DR: In this paper , a broadband nonvolatile electrically programmable 2 x 2 silicon photonic switch based on the phase change material Ge2Sb2Te5 is presented, which exhibits a compact coupling length (64 um), small insertion loss (<2 dB), and minimal crosstalk (<-8 dB) across the entire telecommunication C-band while maintaining a record high endurance of over 2,800 switching cycles.
Abstract: Programmable photonic integrated circuits (PICs) have recently gained significant interest due to their potential in creating next-generation technologies ranging from artificial neural networks and microwave photonics to quantum information processing. The fundamental building block of such programmable PICs is a tunable 2 x 2 switch, traditionally controlled by the thermo-optic or free-carrier dispersion. Yet, these implementations are power-hungry, volatile, and have a large footprint (typically>100 um). Therefore, a truly 'set-and-forget' type 2 x 2 switch with zero static power consumption is highly desirable for large-scale PICs. Here, we report a broadband nonvolatile electrically programmable 2 x 2 silicon photonic switch based on the phase-change material Ge2Sb2Te5. The directional coupler switch exhibits a compact coupling length (64 um), small insertion loss (<2 dB), and minimal crosstalk (<-8 dB) across the entire telecommunication C-band while maintaining a record-high endurance of over 2,800 switching cycles. This demonstrated switch constitutes a critical component for realizing future generic programmable silicon photonic systems.
TL;DR: In this article , an on-chip computational spectrometer in MIR (3.7 − 4.05 µm) using an MEMS-enabled silicon photonic integrated device, which is realized via the time-domain modulation of reconfigurable waveguide couplers.
Abstract: : On-chip spectrometers using silicon photonics offer a compact, energy-efficient, and cost-effective solution to biochemical spectroscopy and hyperspectral imaging in integrated and portable application scenarios. The mid-infrared (MIR) spectral band is critical to spectroscopic sensing. However, the existing on-chip spectrometer approaches are limited in the MIR. Here, we present an on-chip computational spectrometer in MIR (3.7 − 4.05 μ m) using an MEMS-enabled silicon photonic integrated device, which is realized via the time-domain modulation of reconfigurable waveguide couplers. The electrostatically actuated on-chip spectrometer intrinsically features low power consumption and single-pixel detection and offers multiplexing advantages, potentially leading to a high signal-to-noise ratio. We achieve laser spectrum reconstruction across a large bandwidth (350 nm) experimentally. Furthermore, based on a linear superposition assumption, we achieve the polychromatic light reconstruction of narrow spectral features (3 nm resolution) and a broad absorption spectrum of nitrous oxide gas using a regularized regression method.
TL;DR: In this article , the authors explore why higher index materials have not yet materialized and point out a few tentative directions for the search of these elusive materials, be they natural or artificial.
Abstract: While the photonic community is occupied with exotic concepts portending a grand future and fame if not fortune, I respectfully entertain the possibility that a humble concept of simply increasing the refractive index by a modest factor may have a far greater payoff in many walks of life. With that in mind, I explore why higher index materials have not yet materialized and point out a few tentative directions for the search of these elusive materials, be they natural or artificial.
TL;DR: In this article , a flexible hybrid OPD has been designed and fabricated by integrating organic materials with three-dimensional graphene (3DG) film, and the photodetector can detect light from visible to MIR at room temperature with an outstanding responsivity of 108 A W −1 in the NIR region (1000 nm).
Abstract: Near-infrared (NIR) and mid-infrared (MIR) photodetectors have wide applications in biometrics, military, industry, etc. NIR and MIR organic photodetectors (OPD) require narrow-bandgap semiconductors to achieve efficient light absorption. However, it is still a challenge to synthesize organic materials with efficient absorption region above 1000 nm. Herein, a flexible hybrid OPD has been designed and fabricated by integrating organic materials with three-dimensional graphene (3DG) film, and the photodetector can detect light from visible to MIR at room temperature with an outstanding responsivity of 108 A W–1 in the NIR region (1000 nm). Moreover, the hybrid device can detect picowatt-level light with ultrahigh responsivity of 5.8 × 105 A W–1 and specific detectivity of 3 × 1015 Jones in the visible region. Furthermore, the 3DG film/organic hybrid detector is well compatible with flexible substrates and opens up a novel approach to developing flexible photodetectors with high responsivity in a wide spectrum range, suggesting possible potential applications in flexible electronics.
TL;DR: In this article , the authors propose a framework that maps the design of photonic resonators to a set of non-resonant design problems, and theoretically and experimentally demonstrate this framework and show a quality factor beyond 2 million on silicon-on-insulator with singlemode operation, and selective wavelength-band operation.
Abstract: : The automation of device design enabled by optimization and machine learning techniques has been transformative for photonics. While this automation has been successful for nonresonant devices, automated photonic design has remained elusive for resonant devices, key elements for on-chip communication technologies of biosensing and quantum optics, due to their highly nonconvex optimization landscapes. We propose a framework that solves this problem by mapping the design of photonic resonators to a set of nonresonant design problems. We theoretically and experimentally demonstrate this framework and show fl exible dispersion engineering, a quality factor beyond 2 million on silicon-on-insulator with single-mode operation, and selective wavelength-band operation.
TL;DR: In this paper , the hysteresis of the phase transition in voltage-biased vanadium dioxide (VO2) was exploited for optical data storage in silicon photonic integrated circuits.
Abstract: Vanadium dioxide (VO2) is an interesting material for hybrid photonic integrated devices due to its insulator–metal phase transition. Utilizing the hysteresis of the phase transition in voltage-biased VO2, we demonstrate a compact hybrid VO2–silicon optical memory element integrated into a silicon waveguide. An optical pulse writes the VO2 memory, leading to an optical attenuation that can be read out by the optical transmission in a silicon waveguide. Our on-chip memory cell can be optically written with energy as low as 23.5 pJ per pulse and with a 10–90% rise time of ∼100 ns. This approach is promising for optical data storage in silicon photonic integrated circuits.
TL;DR: In this article , the authors show that optical losses have a stronger impact on the resonance amplitude than on the Q-factor, and counterintuitively, optimization of the LOD is not achieved by maximization of the Q factor but by counterbalancing the optical losses and amplitude.
Abstract: Resonant photonic sensors are enjoying much attention based on the worldwide drive toward personalized healthcare diagnostics and the need to better monitor the environment. Recent developments exploiting novel concepts such as metasurfaces, bound states in the continuum, and topological sensing have added to the interest in this topic. The drive toward increasingly higher quality (Q)-factors, combined with the requirement for low costs, makes it critical to understand the impact of realistic limitations such as losses on photonic sensors. Traditionally, it is assumed that the reduction in the Q-factor sufficiently accounts for the presence of loss. Here, we highlight that this assumption is overly simplistic, and we show that losses have a stronger impact on the resonance amplitude than on the Q-factor. We note that the effect of the resonance amplitude has been largely ignored in the literature, and there is no physical model clearly describing the relationship between the limit of detection (LOD), Q-factor, and resonance amplitude. We have, therefore, developed a novel, ab initio analytical model, where we derive the complete figure of merit for resonant photonic sensors and determine their LOD. In addition to highlighting the importance of the optical losses and the resonance amplitude, we show that, counter-intuitively, optimization of the LOD is not achieved by maximization of the Q-factor but by counterbalancing the Q-factor and amplitude. We validate the model experimentally, put it into context, and show that it is essential for applying novel sensing concepts in realistic scenarios.
TL;DR: In this paper , the Fabry-Perot cavities with longitudinal chirality were designed by sandwiching between two smooth metallic mirrors a layer of polystyrene made planar chiral by torsional shear stress.
Abstract: We design, in a most simple way, Fabry–Perot cavities with longitudinal chiral modes by sandwiching between two smooth metallic silver mirrors a layer of polystyrene made planar chiral by torsional shear stress. We demonstrate that the helicity-preserving features of our cavities stem from a spin–orbit coupling mechanism seeded inside the cavities by the specific chiroptical features of planar chirality. Planar chirality gives rise to an extrinsic source of three-dimensional chirality under oblique illumination that endows the cavities with enantiomorphic signatures measured experimentally and simulated with excellent agreement. The simplicity of our scheme is particularly promising in the context of chiral cavity QED and polaritonic asymmetric chemistry.