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Non-degenerate two-photon absorption (NTA) offers an attractive route for wide-field mid-infrared imaging by mapping long wavelength information into the spectral detection windows of mature near-infrared detector technologies. However, existing NTA implementations rely almost exclusively on complex, large-footprint femtosecond laser systems, severely limiting practicality and scalability. Here, we demonstrate an NTA imaging platform that replaces the ultrafast laser with a compact nanosecond mid-IR source coupled to a high-definition indium gallium arsenide camera. Operating in the nanosecond regime removes stringent temporal-overlap requirements, dramatically simplifying system architecture while preserving high detection sensitivity. Using this approach, we achieve chemically selective, wide-field imaging deep into the mid-IR molecular fingerprint region and demonstrate, for the first time, video-rate NTA imaging in this spectrally rich regime. By combining relaxed alignment constraints, compact excitation, and high-speed fingerprint-region imaging, this work establishes nanosecond NTA as a practical and scalable foundation for next-generation mid-IR chemical imaging. 

Silicon’s indirect band gap severely suppresses radiative recombination, limiting its use as an efficient light-emitting material. Although nanoscale confinement of carriers, dielectric resonators, or plasmonic structures can partially mitigate this limitation, these approaches typically require complex fabrication. Here, we report a fundamentally different and scalable mechanism that enables efficient light emission directly from bulk silicon. By decorating a silicon wafer with ultrasmall (<2 nm) gold or copper particles, we observe intense luminescence spanning the visible and near-infrared. Remarkably, the emission is indistinguishable for Au and Cu decorations in both spectral and temporal domains, demonstrating that the confinement extent, not the material composition, governs the effect. We attribute the emission to spatially confined photonic states with broadened momentum distributions, enabling phonon-independent optical transitions otherwise forbidden in silicon. This mechanism yields quantum efficiencies comparable to those of direct-band-gap semiconductors and produces ∼a 10^5-fold enhancement in the integrated emission intensity, establishing a practical route toward silicon light-emitting devices. 

Nanophotonic structures have shown promising routes to controlling and enhancing nonlinear optical processes at the nanoscale. However, most nonlinear nanostructures require a handling substrate, reducing their application scope. Due to the underwhelming heat dissipation, it has been a challenge to evaluate the nonlinear optical properties of free-standing nanostructures. Here, we overcome this challenge by performing shot-controlled fifth harmonic generation (FHG) measurements on a SiC meta-membrane – a free-standing transmission metasurface with pronounced optical resonances in the mid-infrared (λres≈ 4,000 nm). Back focal plane imaging of the FHG diffraction orders and rigorous finite-difference time-domain simulations reveal at least two orders of magnitude enhancement of the FHG from the meta-membrane, compared to the unstructured SiC film of the same thickness. Single-shot measurements of the meta-membrane with varying resonance positions reveal an unusual spectral behavior that we explain with Kerr-driven intensity-dependent resonance dynamics. This work paves the way for novel substrate-less nanophotonic architectures. 

Charge and energy transport within living systems are fundamental processes that enable the autonomous function of excitable cells and tissues. To date, localized control of these transport processes has been enabled by genetic modification approaches to render light sensitivity to cells. Here, we present peptidic nanoassemblies as constituents of a cardiac biomaterial platform that leverages complementary sequence interactions to direct photoinduced energy transport at the cellular interface. Photophysical characterizations and conductivity measurements confirm the occurrence of energy/charge transfer and photocurrent generation upon optical excitation in both dry and electrolytic environments. Comparing an electrostatic sequence pair against a sequence-matched donor–acceptor coassembly, we demonstrate that the sequence design with charge complementarity shows more prominent photocurrent behavior. With the flanking bioadhesive units, the primary and stem cell–derived cardiomyocytes interfaced with covalently stabilized films of the optoelectronic nanostructures exhibited material-stimulated genotypic, structural, or functional cardiac features. Collectively, our findings introduce an optoelectronic cardiac biomaterial where coassembled peptide nanostructures are molecularly designed to induce light sensitivity in excitable cells without gene modification, influencing in vitro cardiac contractile behavior and expression of cardiac markers. 

Abstract Inorganic freestanding helices are rare and sought‐after for their unusual physical states endowed by chirality. To this end, III–VI–VII solids have emerged as a distinct class of ternary 1D van der Waals (vdW) crystals which bear atomically precise helical motifs. However, the physical understanding of the intrinsic and size‐dependent properties of these materials is limited by the lack of synthetic strategies to directly access freestanding nanocrystals in high volumes. Using GaSI as a representative phase, a bottom‐up strategy is presented to grow high yields of ultrathin nanostructures based on this helical materials class. With this strategy, it is possible to grow single crystals of 1D nanowires with thicknesses in the 10–100 nm range at high temperature conditions, as well as quasi‐2D nanoribbons at lower temperatures. The bandgap of the nanowires is established in the UV region and demonstrates the persistence of nonlinear optical behavior as evidence of the persistence of the noncentrosymmetric crystal structure of GaSI at the nanoscale. Inspired by these results, the effect of the helical nature of GaSI on the electronic structure of hypothetical single chains is probed from first principles and shows the pronounced handedness‐dependent and helicity‐imposed spin polarization at the single helix regime.