By manipulating the surface-plasmon-polariton (SPP) excitation properties of two nanogrooves, we demonstrate unidirectional launching of SPPs using a groove-doublet structure both numerically and experimentally, with the groove separation being downscaled to 1/4 and even 1/8 of the wavelength. Thus, the total lateral dimension of the SPP launcher is only about 1/3 and 1/6 of the wavelength, which is truly subwavelength. The measured extinction ratio at incident wavelength of 800 nm reaches as high as 130 and 18. Such subwavelength SPP unidirectional launchers may have important applications in highly integrated plasmonic circuits. (C) 2014 AIP Publishing LLC.
Surface-plasmon-polariton (SPP) launchers, which can couple the free space light to the SPPs on the metal surface, are among the key elements for the plasmonic devices and nano-photonic systems. Downscaling the SPP launchers below the diffraction limit and directly delivering the SPPs to the desired subwavelength plasmonic waveguides are of importance for high-integration plasmonic circuits. By designing a submicron double-slit structure with different slit widths, an ultra-broadband (>330 nm) unidirectional SPP launcher is realized theoretically and experimentally based on the different phase delays of SPPs propagating along the metal surface and the near-field interfering effect. More importantly, the broadband and unidirectional properties of the SPP launcher are still maintained when the slit length is reduced to a subwavelength scale. This can make the launcher occupy only a very small area of
Surface plasmon polariton, a kind of surface electromagnetic wave propagating along the interface between metals and dielectrics, provides an excellent platform for the realization of integrated photonic devices due to its unique properties of confining light into subwavelength scales. Our recent research progresses of nanoscale integrated photonic devices based on surface plasmon polaritons, including all-optical switches, all-optical logic discriminator, and all-optical routers, are introduced in detail.
A submicron asymmetric dielectric-coated metal slit with a Fabry-Perot (FP) nano-resonator is experimentally fabricated to realize an ultra-small on-chip polarization splitter. In the hybrid plasmonic structure, both of the transverse-electric (TE) and transverse-magnetic (TM) modes can be efficiently generated on the front metal surface. Based on the quite different resonant conditions and the different field confinements of the two orthogonal polarization modes in the FP resonator, the TM and TE modes are generated to propagate in the opposite directions along the metal surface. In this device, there are no coupling waveguide regions, and the excitation and the splitting of the TE and TM modes are integrated into the same asymmetric nano-slit. This considerably shrinks the device dimension to only about 850 nm (about one wavelength). In such a submicron asymmetric slit, the measured extinction ratios for the two opposite directions can reach up to (eta(L)/eta(R))(TM) approximate to 1:14 and (eta(L)/eta(R))(TE) approximate to 11:1 at lambda = 820 nm. This on-chip submicron polarization splitter is of importance in highly integrated photonic circuits. (C) 2014 AIP Publishing LLC.
Two Fano resonances are theoretically predicted in a single defect nanocavity, consisting of a rectangular cavity with a small stub defect, side-coupled with a plasmonic waveguide. These two Fano resonances are found to originate from two different mechanisms. One is caused by the excitation of a high-order resonant mode in the rectangular cavity owing to the structural breaking, and the other is attributed to the inherent resonant mode in the small stub defect. The narrow high-order mode and inherent mode couple with the broad low-order resonant mode in the rectangular cavity, giving rise to two Fano resonances. Because of the different origins, these two Fano resonances exhibit quite different responses to the variations of the structural dimensions. This has important applications in highly sensitive and multiparameter sensing in the complicated environments. (C) 2013 Optical Society of America