We present a dynamic metasurface driven by polarization-twisting beams to demonstrate the rotational Doppler effect. Polarization-twisting pulses, composed of left and right circularly polarized pulses with shifted center frequencies, generate a rapidly rotating linearly polarized field. We employed nanocylinders made of amorphous silicon as the building blocks of the metasurface. The rotating field alters the permittivity of the nanocylinders due to the nonlinear Kerr effect, thereby enabling the metasurface to function effectively as a fast-rotating waveplate. When a probe beam passes through this metasurface, both its frequency and spin state are altered due to the rotational Doppler effect. This phenomenon could be potentially used for developing magnetic field-free optical isolators.
High speed optical imaging is a critical tool for the observation of transient, nonrepeatable phenomena. In this talk, we discuss our recent progress on a spatiotemporally encoded ultrafast imaging system. Our approach involves recording of ultrafast events encoded using nano – scribed spatiotemporal masks on a slow camera. The captured data is then reconstructed into a sequence of ultrafast frames via a U – net based deep learning model. We will present both simulation and experimental results.
Transverse spin angular momentum (t-SAM) is a spin with a vector perpendicular to the light propagation direction, naturally appearing in tightly confined electromagnetic waves. For the first time, we successfully generated t-SAM in a spatial point of maximum intensity of focused light using an asymmetric metasurface. The designed metasurface provides complete phase and polarization control and allows for the manipulation of both electric and magnetic transverse spin distribution. The results were obtained through both theoretical and experimental methods, demonstrating the metasurface's ability to generate a strong transverse spin in a focal point ensuring non-zero net spin in the focal plane. This discovery has potential applications in optomechanics, quantum optics, nanometrology, and directional scattering.
Merging the cutting-edge metaphotonics and the compressive sensing technology, we demonstrate a compact single-shot imaging system enabled by a space-time encoding metasurface - an artificially engineered synthetic surface consisting of nanometer-sized elements that can locally manipulate the time delays of incoming light at the femtosecond scale - for capturing the dynamic properties of ultrafast phenomena and uncovering the unknown or hidden laws that govern such dynamics.
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