239 / 2024-08-19 17:01:18

Directional Manipulation of Surface Plasmon Polaritons

surface plasmon polaritons, phase change material, unidirection propagation

In nanophotonics, the manipulation of light on the nanoscale has become a pivotal topic due to its significant applications in optical communication, spectroscopy, and biosensing. Directional scattering is essential for biomedical sensing, displays, high-resolution imaging, and on-chip spectroscopy. Surface plasmon polariton (SPP) is an electromagnetic excitation existing on the interface between a metal and a dielectric medium. Due to the advantage of strong field localization, SPP can overcome the diffraction limits of dielectric photonics, which shows potential in developing nanoscale color routing solutions. Plasmonic nanorouters have predominantly been utilized for the visible and near-infrared spectra. However, the current research in telecommunication bands for the advantages of easy integration still needs to be improved. In this work, an innovative ultracompact asymmetric nanoplasmonic router is designed explicitly for communication bands. This router is capable of directing O- and C-band to distinct spatial locations that can switch the direction of the surface plasmon polaritons(SPPs) excitation based on the exciting wavelength. By carefully adjusting nanogroove geometry, the initial phase and amplitude of SPPs can be modified to alter the SPP propagation direction. We experimentally demonstrate the opposite propagation of SPPs at 1310 nm and 1550 nm wavelengths with the extinction ratios of 26 and -14 dB. In particular, the efficient area for completing the color routing is a mere 1.4 um x 4 um, defined as the width of the entire grooves and the diameter of the light spot. The device can be regarded as a compact coarse wavelength divider which can be used in ultra-large capacity communication system. In addition to changing the propagation direction with different incident wavelength. The propagate direction can also be altered by introducing new material such as the phase change material (PCM, GST). The GST material has advantages such as fast response time, low power and non-volatility and can be inserted our the asymmetric slits. In this work, the bidirectional transmission SPPs can become unidirectional SPP by changing the crystal phase of the GST with a response time of ns level. The device with the PCM can be further to develop the compact optical switch device for communicaiton bands.