Intrinsic nonlinear geometric phase in SHG from zincblende crystal symmetry media.

We demonstrate that AlGaAs thin films and metasurfaces generate a distinct intrinsic nonlinear geometric phase in their second harmonic signals, differing significantly from previous studies on nonlinear dielectric, plasmonic, or hybrid metasurfaces. Unlike conventional observations, our study reveals that the second harmonic phase remains unaffected by the linear optical response at both pump and harmonic wavelengths, introducing a novel realm of achievable phase functions yet to be explored. Furthermore, we explore the interplay between this intrinsic nonlinear geometric phase and the geometric phase induced by rotations of nanoresonators within metasurface arrangements.

Advances in nonlinear metasurfaces for imaging, quantum, and sensing applications.

Metasurfaces, composed of artificial meta-atoms of subwavelength size, can support strong light-matter interaction based on multipolar resonances and plasmonics, hence offering the great capability of empowering nonlinear generation. Recently, owing to their ability to manipulate the amplitude and phase of the nonlinear emission in the subwavelength scale, metasurfaces have been recognized as ultra-compact, flat optical components for a vast range of applications, including nonlinear imaging, quantum light sources, and ultrasensitive sensing. This review focuses on the recent progress on nonlinear metasurfaces for those applications.

Enhancing second harmonic generation by Q-boosting lossless cavities beyond the time bandwidth limit.

Nanostructures proved to be versatile platforms to control the electromagnetic field at subwavelength scale. Indeed, high-quality-factors nanocavities have been used to boost and control nonlinear frequency generation by increasing the light-matter interaction. However, nonlinear processes are triggered by high-intensities, which are provided by ultrashort laser pulses with large bandwidth, which cannot be fully exploited in such devices.

Fabrication of 1 × integrated power splitters with arbitrary power ratio for single and multimode photonics.

Compact power splitters are essential components in integrated optics. While 1 × 2 power splitters with uniform splitting are widely used, a 1 × splitter with arbitrary number of ports and arbitrary splitting ratio is yet to be demonstrated. In this work we address this problem.

Increased metabolic demand reveals morpho-functional impacts caused by settleable atmospheric particulate matter on fish gills.

Exposure to environmentally relevant levels of settleable atmospheric particulate matter (SePM) limits the aerobic performance of inactive healthy adult fish. We evaluated the gill morpho-functional impacts (gill structure and ionic balance) caused by SePM exposure (96 h) in Nile tilapia when fish is impelled to maximal aerobic swimming effort. In control fish, swimming reduced epithelial filament thickness (EFT, 25 %), increased the distance between lamellae (DL, 21 %), and reduced the plasma Na (5 %).