Conventional imaging apparatus, composed of lenses and camera, are limited to recording light intensity. Nevertheless, the phase of light has the potential to transmit more information than its intensity. Unfortunately, the acquisition of phase information generally demands the incorporation of sophisticated and unwieldy optical elements. Here, we propose a single-shot complex amplitude imaging meta-optics system capable of capturing both amplitude and phase information of the light field. By leveraging the versatility and adaptability of metasurface, a compact imaging configuration, comprising of just one single-layer metalens and one off-the-shelf polarization camera, can uniquely determine phase and amplitude from the shearing interference patterns in the four polarization channels based on polarization phase-shifting method. We experimentally demonstrate a variety of applications including surface topography measurement, metasurface phase characterization and quantitative phase microscopy with high accuracy. The results showcase promising and potential advancements in miniaturized complex amplitude imaging systems and portable applications .
Conventional wavefront sensors suffer from the fundamental limitation of the space-bandwidth product, and have a trade-off between their spatial sampling interval and dynamic range. Here, we leverage nonlocal thin film optical filters with optimized angle- and polarization-dependent response to circumvent the fundamental limitation, and realized a robust single-shot wavefront sensing system with a small spatial sampling interval of 6.9 μm and a large angular dynamic range of 15°. The system only requires inserting two multilayer dielectric filters, fabricated using a mature thin film deposition technique, into a conventional 4-f imaging apparatus. The polarization-sensitive nonlocal filters are used to map the 2D phase gradients of the incident light field to the intensity variation of the x- and y-polarized light, respectively, thus enabling single-shot 2D wavefront reconstruction from images taken by a polarization camera. Such a system may be used for a variety of applications, including high-resolution image aberration correction, surface metrology, and quantitative phase imaging.
Optical metasurfaces are endowed with unparallel flexibility to manipulate the light field with a subwavelength spatial resolution. Coupling metasurfaces to materials with strong optical nonlinearity may allow ultrafast spatiotemporal light field modulation. However, most metasurfaces demonstrated thus far are linear devices. Here, we experimentally demonstrate simultaneous spatiotemporal laser mode control using a single-layer plasmonic metasurface strongly coupled to an epsilon-near-zero (ENZ) material within a fiber laser cavity. While the geometric phase of the metasurface is utilized to convert the laser’s transverse mode from a Gaussian beam to a vortex beam carrying orbital angular momentum, the giant nonlinear saturable absorption of the ENZ material enables pulsed laser generation via the Q-switching process. The direct integration of a spatiotemporal metasurface in a laser cavity may pave the way for the development of miniaturized laser sources with tailored spatial and temporal profiles, which can be useful for numerous applications, such as superresolution imaging, high-density optical storage, and three-dimensional laser lithography.
High-harmonic generation (HHG) has been used to generate extreme ultra-violet (EUV) light sources to probe fast electron dynamics in the attosecond time scale. While traditionally observed in rare-gas atoms, HHG has also recently been reported in solids, with reduced threshold pump field and the additional advantage of producing stable EUV waveforms in a compact setup. Unfortunately, above-band-gap absorption restricts the HHG process to a very thin layer of the solid-state material (typically tens of nanometers in thickness), significantly limiting the generation efficiency. Here, we use a material operating in its epsilon-near-zero (ENZ) region, where the real part of its permittivity vanishes, to greatly boost the efficiency of the HHG process at the microscopic level. In experiments, we report high-harmonic emission up to the 9th order directly from a low-loss, solid-state ENZ medium: indium-doped cadmium oxide, with an excitation intensity at the GW cm-2 level. Furthermore, the observed HHG signal exhibits a pronounced spectral red-shift as well as linewidth broadening, resulting from the photo-induced electron heating and the consequent time-dependent resonant frequency of the ENZ film. Our results provide a novel nanophotonic platform for strong field physics, reveal new degrees of freedom for spectral and temporal control of HHG, and open up possibilities of compact solid-state attosecond light sources
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