Enantiomeric excess detection in a chiral molecular mixture is paramount because very often opposite enantiomers exhibit profound functional dissimilarities that play decisive roles in biochemical applications. Existing chiral sensing methods mostly rely on large operational sample volumes, hindering compatibility with integrated sensing schemes. Here, we propose a novel chiroptical sensing technique based on the inverse Faraday effect in a photonic micro-capillary filled with nl-volume chiral drug solution. We theoretically demonstrate that, upon excitation by intense laser light, an isotropic assembly of chiral drugs produces a static magnetisation, with amplitude and direction depending on the enantiomeric excess. In turn, by measuring the chirally-sensitive static magnetic field in the vicinity of the micro-tube one can retrieve the enantiomeric excess of the chiral drug solution. Our theoretical predictions unlock new opportunities for the development of innovative nanophotonic devices suitable for efficient chiroptical sensing with nl-volume sensitivity.

Engineering the helicity of single photons is a central challenge in nanophotonics and quantum optics, with applications ranging from chiral light-matter interactions to quantum communication protocols. We investigate the effects produced by a chiral cavity consisting of two twisted anisotropic photonic crystal mirrors on the spontaneous emission of a quantum system. For a given vacuum wavelength, the considered mirrors can be engineered to concurrently exhibit high helicity-preserving reflectance for one circular polarization and high transmittance for the opposite one, for incidence angles up to 20◦ with respect to the optical axis. Considering an atomic two-level system within thecavity, we evaluate the total dyadic Green function, taking into account both inhomogeneous and scattering electromagnetic contributions. We demonstrate that optimal configurations can achieve a 3% imbalance between the spontaneous emission rates of right- and left-circularly polarized light when averaged over random dipole orientations. Remarkably, this imbalance increases to 20% under suitably tuned dipole orientations. Even larger values are expected for two-dimensional arrays of such dipoles that isolate the normal component of the emitted field, while the remaining contributions interfere destructively. We envision that the proposed system will expand the set of tools availablefor investigating chiral matter and support the development of compact sub-micrometer circularly polarized single-photon sources.

Self-diffraction is a four-wave mixing process proportional to the square modulus of third-order nonlinearity susceptibility χ(3), which is related to the material's electronic and thermal properties. In this study, we investigate the wavelength dependence of the self-diffracted signal generated by a femtosecond pulsed laser in a dye solution to directly evaluate the electronic third-order nonlinear susceptibility spectrum. By accounting for absorption effects and phase matching conditions, we determine the |χ(3)| for different concentrations. Experimental results complemented with theoretical predictions show that, in the low absorption and thin sample limits, the signal reproduces the |χ(3)| spectral profile. These findings demonstrate the feasibility of measuring nonlinear susceptibility spectra arising solely from the bound-electronic response across a wide spectral range and for various compounds.

Chiroptical sensing is central to gain fundamental insight into electronic, vibrational and rotational degrees of freedom of chiral molecules, and is a cornerstone for nanomedicine and drug discovery platforms. Current chiral sensing technologies to assess the enantiomeric imbalance of chiral pharmaceutical compounds are sensitive to ml volumes but are time-consuming and cannot be integrated on a chip, thus creating a major bottleneck for drug discovery and nanomedicine. Here, we propose a novel chiroptical sensing approach based on optical rectification in a photonic micro-cavity filled by a drug solution with nl volume. We theoretically demonstrate that, upon optical excitation by intense pulsed laser light, such a nonlinear effect produces a chirally-sensitive nV voltage burst at the electrically-gated micro-cavity boundaries, with sign depending solely on the drug enantiomeric imbalance. Our results shed light on the potential of optical rectification as a robust platform for innovative lab-on-a-chip devices enabling chiral sensing with nl sensitivity.

We propose a new laboratory strategy to generate and detect axion-like particles via third-harmonic generation induced by two non-collinear, polarised high-intensity laser beams of peak intensity of the order of 10^24 W/cm^2, where the third-harmonic signal is generated by the axion field. Starting from the axion-modified Maxwell equations, we analytically derive the axion-induced third-harmonic field, and show that by using state-of-the-art petawatt laser facilities, a detectable signal can be obtained over a broad range of axion masses and couplings. A key feature of the setup is that the axion-photon conversion rate can be resonantly enhanced by tuning the angle between the two beams through a mechanism that does not depend on the physical volume of the apparatus. The proposed configuration may therefore probe an unexplored region of axion parameter space and pave the way for next-generation high-power laser-based axion searches.

Electromagnetically induced transparency and lasing without inversion are optical manifestations of quantum coherence control. Here we theoretically investigate these effects in a chiral molecule, coherently driven by an optical pump, finding that signal fields can undergo chiroptical absorption quenching or amplification within particular spectral windows at pump intensities as low as approximate to 1kW/cm2. Our calculations reveal that molecular chirality has the capacity to dramatically alter quantum coherence phenomena at peculiar wavelength ranges, modulating efficiently circular dichroism depending on the polarisation state of both pump and signal fields and the molecular orientation. We find that, for a given molecular orientation, the dissymmetry factor probed upon right/left-circular polarisation excitation by the signal can get maximised by pump polarisation tuning and the signal direction. By averaging over impinging signal orientations, we find that the orientation-averaged dissymmetry factor can diverge owing to electromagnetically induced transparency producing vanishing averaged absorption cross-sections.

We analyze surface plasmon polaritons at noble metal interfaces for enhancing chiroptical sensing of dilute chiral drug solutions. Circular dichroism is amplified by plasmonic resonances to attain sensitivity to nano-scale drug volumes, demonstrating great potential for chiroptical sensing.

Nonlinear optics lies at the heart of classical and quantum light generation. The invention of periodic poling revolutionized nonlinear optics and its commercial applications by enabling robust quasi-phase-matching in crystals such as lithium niobate. However, reaching useful frequency conversion efficiencies requires macroscopic dimensions, limiting further technology development and integration. Here we realize a periodically poled van der Waals semiconductor (3R-MoS2). Owing to its large nonlinearity, we achieve a macroscopic frequency conversion efficiency of 0.03

We investigate the mid-infrared chiroptical response of Aluminum-doped Zinc Oxide (AZO)-based plasmonic nanostructures incorporating pharmaceutical chiral drug solutions. We systematically examine plasmon-enhanced vibrational circular dichroism (VCD) of the chiral drug solution to develop efficient chiroptical sensing techniques.

We theoretically model third-harmonic generation in near-zero heterogeneous nanostructures arising from collision-driven nonlinear electron dynamics. We explore the potential of harmonic generation process on a sodium-aluminum bilayer for the development of integrated XUV sources.

The capability of anisotropic media to exert an optical torque on electromagnetic fields is crucial for polarization control. Here we investigate twisted layered stacks of uniaxial anisotropic media to engineer chiral mirrors for the manipulation of circularly polarized light by adjusting the layer number, thicknesses, and orientation. To this aim, we undertake a comprehensive theoretical analysis devising a multilayered twisted anisotropic photonic crystal enabling highly efficient circular polarization manipulation functionalities, i.e., showing concurring close-to-unitary helicity-preserving reflectance of one circular polarization and transmittance of the opposite one. Owing to the angular-momentum manipulation concept enabled by our proposed devices, we envisage that such chiral mirrors are promising candidates for an alternative class of integrated circular polarizers, holding great potential for applications in quantum technologies, polarization-sensitive optical detectors, and electro-optical information processing.

The enhancement of the inherently weak optical activity of solvated molecules by superchiral fields, crucial for detecting their chirality, is a research frontier of photonics and the basis of novel chiroptical detection schemes. Here, we show that an effective medium consisting of randomly dispersed metal-based nanoparticles embedded within an optically active solvated drug (aqueous reparixin) can enhance vibrational optical rotation and circular dichroism thanks to superchirality produced by slow light in near-zero index conditions. We evaluate from first principles the effective bianisotropic response of the bulk chiral effective medium, showing that, by adjusting the nanoparticles filling fraction, vibrational optical activity is greatly enhanced by a factor ≃ 10^2-10^3 at the near-zero index resonance. Our results are relevant for the development of innovative devices capable of detecting the chirality of low-volume samples, with applications in quantum chemistry and nanomedicine.

Polarization control is achievable through the optical torque exerted by anisotropic media. We engineer miniaturized uniaxial anisotropic stacks as chiral mirrors reflecting over 99% of one circular polarization and less than 1% of the opposite.

Materials with a vanishing dielectric constant provide an ideal platform for achieving plasmon-enhanced light-matter interactions and are widely employed in various cutting-edge nonlinear photonics applications. In this study, we present the first experimental demonstration of extreme ultraviolet (XUV) plasmon-enhanced self-driven spectral modification using a submicrometric foil of aluminium. This is achieved through the excitation of widely tunable Ferrell-Berreman epsilon-near-zero resonances with extremely low absorption. Our angle-dependent measurements of spectral modulation enhancement, supported by theoretical analysis, reveal efficient spectral modification at peak intensities as low as 380 GW/cm2, which we attribute to ultrafast heating and saturation effects. These findings mark a breakthrough in the enhancement of typically weak nonlinearities in the XUV regime through nonlinear plasmonics, potentially paving the way for unprecedented tools for the manipulation and control of XUV radiation.

We investigate miniaturized and integrable stacks of uniaxial anisotropic layered media to engineer chiral mirrors for manipulating circularly polarized light thanks to the optical torque exerted by the medium polarization on an electromagnetic field.

We explore the potential applications of localized surface plasmon resonances (LSPRs) to investigate mid-infrared chiroptical response of Al-doped ZnO (AZO)-based nanostructures embedding layers of chiral pharmaceutical drug solutions to develop novel chiroptical sensing techniques.

We investigate plasmon-enhanced optical rotation and circular dichroism in a near-zero-index metamaterial composed of metallic nanospheres randomly dispersed in a chiral drug solution.

We investigate the mid-infrared chiroptical response of plasmonic nanostructures based on Al-doped ZnO and layers of an aqueous solution of Ladarixin, a chiral pharmaceutical currently under clinical trial for the treatment of type 1 diabetes. We explore the possibilities offered by localised surface plasmon resonances (LSPRs) for the enhancement of vibrational circular dichroism (VCD) of the considered chiral drug solution. Focusing on diverse plasmonic nanoshell geometries, we find that LSPRs provide an amplification factor of VCD differential absorption cross-section ranging from [Formula: see text] to [Formula: see text] thanks to near-field intensity enhancement produced by LSPRs. Our results indicate that nanoshell LSPRs are promising for probing molecular chirality at the nanoscale.

We investigate resonant third-harmonic generation in near-zero index thin films driven out-of-equilibrium by intense optical excitation. Adopting the Landau weak coupling formalism to incorporate electron-electron and electron-phonon scattering processes, we derive a novel set of hydrodynamic equations accounting for collision-driven nonlinear dynamics in sodium. By perturbatively solving hydrodynamic equations, we model third-harmonic generation by a thin sodium film, finding that such a nonlinear process is resonant at the near-zero index resonance of the third-harmonic signal. Thanks to the reduced absorption of sodium, we observe that third-harmonic resonance can be tuned by the impinging pump radiation angle, efficiently modulating the third-harmonic generation process. Furthermore, owing to the metallic sodium response at the pump optical wavelength, we find that the third-harmonic conversion efficiency is maximised at a peculiar thin film thickness where evanescent back-reflection provides increased field intensity within the thin film. Our results are relevant for the development of future ultraviolet light sources, with potential impact for innovative integrated spectroscopy schemes.