Phys.org July 17, 2023
Researchers in China developed an optical waveguide scheme to generate a sub-nanometer-confined optical field in a nano slit waveguiding mode in a coupled nanowire pair (CNP). They showed that, when a conventional waveguide mode with a proper polarization was evanescently coupled into a properly designed CNP with a central nano slit, it could be channeled into a high-purity nano slit mode within a waveguiding length <10 μm. The CNP could be either freestanding or on-chip by using a tapered fiber or planar waveguide for input-coupling, with a coupling efficiency up to 95%. Within the slit region, the output diffraction-limited nano slit mode offered an extremely confined optical field (∼0.3 nm × 3.3 nm) with a peak-to-background ratio higher than 25 dB and could be operated within a 200-nm bandwidth. According to the researchers the waveguiding scheme was simple and straightforward in structural design flexible and versatile in operation. It may offer an efficient and flexible platform for exploring light–matter interactions beyond the nanometer scale and developing optical technologies ranging from superresolution nanoscopy and atom/molecule manipulation to ultra-sensitivity detection… read more. Open Access TECHNICAL ARTICLE
