RESUMO
Polarization measurement is crucial for many optical applications in science and technology. Geometric metasurfaces have been used to develop polarization-sensitive holograms, providing a new opportunity for polarization measurement. We propose and experimentally demonstrate a hologram method to measure the polarization state of light. A reflective-type metasurface hologram is used to generate holographic images of graphene pattern. The ellipticity and helicity of the incident light are measured based on the intensities of the neighboring light spots, corresponding to two opposite circular polarization states. Benefiting from the advantages of reflective geometric metasurfaces, this device can operate in broadband.
RESUMO
Optical labels are needed for probing specific target molecules in complex biological systems. As a newly emerging category of tags for molecular imaging in live cells, the Raman label attracts much attention because of the rich information obtained from targeted and untargeted molecules by detecting molecular vibrations. Here, we list three types of Raman probes based on different mechanisms: Surface Enhanced Raman Scattering (SERS) probes, bioorthogonal Raman probes, and Resonance Raman (RR) probes. We review how these Raman probes work for detecting and imaging proteins, nucleic acids, lipids, and other biomolecules in vitro, within cells, or in vivo. We also summarize recent noteworthy studies, expound on the construction of every type of Raman probe and operating principle, sum up in tables typically targeting molecules for specific binding, and provide merits, drawbacks, and future prospects for the three Raman probes.
