Active and efficient control of nonlinear optical processes is essential for integrated photonics, with applications in signal processing, ultrafast switching, and quantum light manipulation. While nanophotonic structures are powerful for enhancing nonlinearities, achieving wide-range electrical tunability has remained a challenge. Plasmonic tunnel junctions offer a unique path to bridge this gap because they combine extreme optical field confinement with direct electrical control in a single nanoscale device. Here, we report the first, to our knowledge, demonstration of electrically tunable second-harmonic generation (SHG) in plasmonic tunnel junctions. Using ultra-stable epitaxial heterostructures, we achieve reproducible modulation of SHG with depths up to ∼500% and magnitudes above 1.3V −1 . We identify two mechanisms, electric-field-induced SHG (EFISH) and ion migration, that can either compete or cooperate depending on junction thickness and bias, enabling both broad tunability and ferroelectric-like hysteretic switching. These findings establish plasmonic tunnel junctions as a platform for electrically controlled nonlinear optics, with potential for nanoscale light sources, reconfigurable modulators, and neuromorphic photonic devices.

Detecting biomolecules at ultralow concentrations remains a fundamental challenge in optical biosensing, primarily due to weak light–matter interactions governing signal generation. To address this limitation, we introduce a nonlinear optical sensing platform that leverages second-harmonic generation (SHG) within two-dimensional materials, amplified through quantum-engineered energy transfer. Our approach integrates DNA-programmable nanostructures with monolayer MoS 2 to form disordered metasurfaces that significantly enhance nonlinear optical responses. By precisely positioning individual CdTe/ZnS quantum dots (QDs) at defined distances from the MoS 2 surface using DNA origami scaffolds, we establish highly efficient Förster resonance energy transfer (FRET) pathways, boosting SHG signals by 124.70 fold. Furthermore, the platform incorporates a clustered regularly interspaced short palindromic repeats (CRISPRs) system as a switch: target recognition induces conformational changes that modulate SHG intensity with 93.60% specificity. This integrated material-biology design achieves unprecedented detection limits of 168 zM for microRNAs (miRNAs), representing an improvement of over six orders of magnitude compared to conventional optical biosensors, while retaining single-base discrimination capability. Validation with clinical lung cancer patient samples demonstrated superior diagnostic performance relative to reverse transcription quantitative polymerase chain reaction (RT-qPCR), exhibiting significantly enhanced signal-to-noise ratios in complex biological matrices. Our work establishes a new paradigm in nonlinear optical sensing by demonstrating how engineered quantum interactions can overcome intrinsic limitations of optical detection. This co-design framework, synergizing materials, nanophotonics, and biology, paves the way for next-generation optical diagnostic platforms.

In many laser scan engines, mechanical inertia imposes a tradeoff between mirror diameter (mass) and scan speed (cycle time) and/or scan angle amplitude. Ultimately, this limits the field-of-view and/or scan speed in multiphoton and confocal imaging, laser-based manufacturing, and other applications. To push parameters past this inertia limit, we present a non-inertial (stationary) add-on unit that doubles the scan angle amplitude while preserving both the beam size and cycle time, thus doubling the étendue (optical invariant) and overall system throughput. We demonstrate its use in two-photon calcium imaging of neural activity in living mice. We also adapt the approach to present a phase-doubling unit that doubles the maximum range of phase modulators. Finally, we describe further variants, including generalizing the approach to Nx scan angle multiplication (N=2,3,4,…) with diffraction-limited performance across a wide scan angle range and over a broad wavelength bandwidth. These non-inertial scan angle multipliers (called Nisam2x, 3x,…) fundamentally break the inertia-imposed tether between scan speed and scan angle amplitude, enabling expanded capabilities of a range of technologies, including imaging, adaptive optics, sensing, marking, and manufacturing.

Laboratory-scale gaseous plasma events offer a rich environment for the study of ionization, energy transfer, and non-equilibrium dynamics, whose understanding plays a critical role in wakefield accelerators, inertial confinement fusion, and plasma ignition devices. Probing these dynamics, however, has been historically difficult due to their weak absorption of visible light and inherently challenging spatial and temporal scales. Recent advances in computational imaging have opened the door for advanced forms of plasma diagnostics with techniques such as single-shot ptychography (SSP); however, fidelity challenges and reduced resolution have limited the application of SSP to non-repeatable plasma dynamics. Here we introduce a near-field implementation of SSP that delivers enhanced fidelity and resolution, as well as improved robustness to noise compared to far-field methods, verified through systematic experimental and numerical comparisons. Using this method, we demonstrate ptychographic imaging of non-repeatable plasma dynamics through the analysis of a full temporal trace of an electrostatic discharge event. These results establish near-field SSP as a powerful plasma diagnostic tool, opening the pathway toward 3D, hyperspectral, and single-shot ultrafast motion-picture ptychographic imaging of complex plasma systems.

High-sensitivity photodetectors with a high signal-to-noise ratio are essential for numerous infrared applications. While avalanche photodiodes (APDs) offer high internal gain, their performance is limited by high dark current in the narrow-bandgap materials used for infrared absorption. This results in operation at cryogenic temperatures, which in turn increases system complexity and additional cost. The dark current can be reduced by decreasing the absorption layer thickness, but this also lowers the quantum efficiency. Here, we report separate absorption, charge, and multiplication (SACM) Al x In 1−x As y Sb 1−y APDs with thin absorber thicknesses, ranging from 50 to 400 nm. These devices exhibit low dark current at room temperature. A 2D metal grating structure, consisting of a periodic array of parallel Au pillars, on top of these devices, can compensate for the decrease in external quantum efficiency (EQE) in thin absorbers. This is due to lateral coupling into the absorber waveguide modes and plasmon-enhanced transmission. Non-vertical sidewalls of the Au pillars will limit the input coupling efficiency. This can be significantly mitigated by filling the gap between the metal pillars with a material having an optimized refractive index. This was successfully demonstrated using BK-7 index-matching liquid (n∼1.5). Due to the metal grating configuration, the photoresponse is polarization-dependent. By combining index matching and optimizing the input polarization, we have achieved EQE of 8.2%, 16%, 30.6%, and 35% for 50, 100, 200, and 400 nm, respectively.

Fourier ptychographic microscopy (FPM) is a computational imaging technique that achieves high-resolution complex amplitude reconstruction across a large field of view. However, conventional FPM is fundamentally limited to regions near the optical axis due to violations of the shift-invariance assumption in off-axis areas, resulting in challenging edge-of-field-of-view reconstructions. We propose neural pupil engineering FPM, termed NePE-FPM, a physical model that dynamically shifts the pupil function position during reconstruction instead of fixing the pupil function in the center of the pupil plane. NePE-FPM engineers the pupil function using an implicit neural representation with multi-resolution hash encoding, enabling continuous, smooth shifting of the pupil function without introducing additional physical parameters. By optimizing a feature-domain loss function, NePE-FPM adaptively filters Fourier-space information from low-resolution measurements, achieving accurate off-axis reconstruction without modeling off-axis propagation. Experimental results demonstrate isotropic resolution of 1149 lp/mm across an 11mm2 FOV using a 4×/0.1NA objective. The NePE-FPM bridges the gap between theoretical FPM capabilities and practical whole-slide imaging demands.