Christian Stock, Gregory Berg, Matthea Thielking, Jonas Jurkevičius, Sebastian Karpf
Two-Photon microscopy (TPM) is an intravital imaging technique with deep tissue penetration, high three-dimensional resolution and low photobleaching. However, imaging speeds have traditionally been limited because images are generated by point scanning. Recently, Spectro-Temporal Laser Imaging by Diffractive Excitation (SLIDE) introduced a high-speed laser-scanning approach for two-photon microscopy, harnessing a swept-source laser in combination with a diffraction grating for inertia-free point scanning with line-rates at Megahertz (MHz) frequencies and frame-rates in the kilohertz range. Notably, the pixel-rate reached up to Gigapixels/s, which scales with ultra-short second harmonic generation signals. However, this nanosecond pixel dwell time is too short for fluorescence decays. Here, we present an adaptive approach to high-speed multiphoton imaging where the pixel-rate of the SLIDE microscope can be adapted to the fluorescence lifetime of the sample. This is achieved by interleaved sampling, allowing for larger temporal intervals in the time domain while preserving spatial sampling density. We demonstrate adaptive frame-rate SLIDE microscopy by flexible, active pulse modulation on an electro-optic modulator (EOM) and discuss how this can be extended to future smart SLIDE systems where the pixel dwell time can be optimally set for each sample.
Ranjeet Dwivedi, Charles Pourny, Anthony Albanese, Agraj Yadav, Régis Orobtchouk, Gaya Benane, Rajath Sawant, Martina Tomelleri, Yoann Brulé, Arnaud Rogemont, Aurélien Coillet, Benoit Charbonnier, Pierre Noé, Benoit Cluzel, Fabio Pavanello
This paper reviews recent advances in the field of photonic devices integrating phase-change materials (PCMs). In particular, certain PCMs showcase interesting properties such as non-volatile behaviour and ultra-low optical losses that can be leveraged in computing architectures. For example, they can operate as complex-valued weights enabling ultra-low power consumption matrix-vector multiplications. Here, we first review the optical properties of multiple PCM compounds as interesting candidates for photonic computing. Then, we discuss about GeSe-based electrically activated photonic devices that exploit such properties in novel device concepts. Specifically, we present a hybrid-mode interferometer and an asymmetric heater geometry along the propagation direction for electrical PCM actuation. These approaches lead to a higher number of encoded states as well as ultra-low optical insertion losses compared to previous implementations, while retaining a compact footprint and practical driving conditions. Finally, we present experimental results for optically actuated Ge 2 Sb 2 Te 5 (GST225) based waveguides in terms of encoding capabilities and reliability for all-optical reconfigurability and processing.
J. Sumaya-Martínez, M. A. Ortiz-Ferreyro, O. Rojas-Hernandez
Double-slit diffraction remains a foundational problem in wave optics, but most closed-form treatments assume single-wave illumination. In many modern optical systems, multi-wave coherent illumination is used to tailor the spatial spectrum of the field and engineer structured diffraction patterns. We present an analytical and numerical study of double-slit diffraction under coherent illumination by three plane waves: one normally incident and two symmetrically tilted at angles ± θ. By imposing an edge-zero condition on the incident field at the slit boundaries, we derive compact closed-form Fresnel expressions in terms of standard Fresnel integrals. The formalism is extended to an arbitrary number of coherent beams and further generalized to include scalar partial coherence, transverse coherence decay, and Gaussian-beam illumination. Numerical Fresnel propagation is used to validate the analytical formulas. The analytical and numerical results show excellent agreement over the parameter ranges studied. The model enables direct control of the transmitted angular spectrum through the choice of incidence angles and phases. Partial coherence reduces fringe visibility while preserving the overall envelope, and Gaussian illumination suppresses sidelobes while slightly broadening the main lobe. The framework also provides a practical route to engineer apodized and quasi-robust diffraction profiles. Multi-wave coherent illumination provides a simple and flexible mechanism for diffraction-pattern engineering in double-slit systems. The results are relevant to structured illumination, apodization, beam shaping, interference lithography, and coherent multiplexing, and they offer a feasible basis for experimental validation in laboratory optical setups.
Noroviruses are a leading cause of acute gastroenteritis worldwide, and their rapid and reliable detection remains a significant challenge for current diagnostic technologies. In this work, we present a plasmonic metasurface platform based on Y-shaped nanocavity arrays designed for label-free viral detection using surface-enhanced Raman spectroscopy (SERS). The nanostructured metasurface was fabricated using electron-beam lithography and engineered to support plasmonic resonances near the 785 nm excitation wavelength, enabling strong electromagnetic field localization and Raman signal enhancement. SERS measurements were performed on human norovirus (HNoV) and murine norovirus (MNV), producing distinct vibrational fingerprints associated with viral capsid biomolecules. Despite the structural similarity between both viruses, multivariate statistical analysis based on principal component analysis (PCA) enabled clear discrimination between their spectral signatures, with the first two principal components explaining more than 98% of the total variance captured. These results demonstrate that plasmonic metasurfaces combined with SERS fingerprinting and statistical analysis provide a powerful strategy for the label-free identification of closely related viral pathogens. The proposed platform highlights the potential of nanophotonic biosensors for rapid pathogen detection in biomedical diagnostics and environmental monitoring.
