摘要
We propose to generate a sub-nanometer-confined optical field in a nanoslit waveguiding mode in a coupled nanowire pair(CNP).We show that,when a conventional waveguide mode with a proper polarization is evanescently coupled into a properly designed CNP with a central nanoslit,it can be efficiently channeled into a high-purity nanoslit mode within a waveguiding length<10μm.The CNP can 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 nanoslit mode offers an extremely confined optical field(∼0.3 nm×3.3 nm)with a peak-to-background ratio higher than 25 dB and can be operated within a 200-nm bandwidth.The group velocity dispersion of the nanoslit mode for ultrafast pulsed operation is also briefly investigated.Compared with the previous lasing configuration,the waveguiding scheme demonstrated here is not only simple and straightforward in structural design but is also much flexible and versatile in operation.Therefore,the waveguiding scheme we show here 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.
基金
This work was sup-ported by the National Key Research and Development Program of China(2018YFB2200404)
the New Cornerstone Science Foundation,the National Natural Science Foundation of China(92150302 and 62175213)
the Natural Science Foundation of Zhejiang Province(LR21F050002)
the Fundamental Research Funds for the Central Universities.
