Spin angular momentum (SAM) and orbital angular momentum (OAM) have opened up new avenues in optical communication and imaging processing. However, detection of these states concurrently requires complicated optical setups. Here, we propose a 12-channel detection for SAM and OAM modes with a dielectric ultracompact metasurface. The phase profile is constructed with both propagation phase and geometric phase. Adopting spin photonic Hall effect and off-axis focusing scheme, light beams carrying different vortices are demultiplexed into several vortex beams with distinct topological charges, and each can be recognized with different focused spots on a transverse plane with unique azimuthal coordinate. The proposed design efficiently demultiplexes the incident with different SAM and OAM modes through a single layer metasurface. We envision this work will pave the way for high-capacity optical communication applications and integrated optical systems.
We develop a disposable sub-millimeter fiberoptic Raman needle probe for real-time in vivo tissue and biofluids Raman measurements. High-quality tissue Raman spectra in fingerprint and high-wavenumber regions can be collected within sub-second from different tissue types and biofluids using the needle Raman probe fabricated together with the structured background subtraction algorithm developed. We further validate the depth-resolved deep tissue Raman spectra measurement capability of the fiberoptic needle Raman probe by advancing the needle Raman probe into a mice brain model. We demonstrate that the sub-millimeter fiberoptic Raman probe developed can achieve real-time time collection of deep tissue and biofluids FP/HW Raman spectra with high signal to noise ratios, suggesting the potential of dual functioning of Raman optical biopsy and fine-needle aspiration biopsy for in vivo deep tissue and biofluids characterization in the human body.
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