Ultra-compact graphene plasmonic filter integrated in a waveguide

Graphene plasmons have become promising candidates for deep-subwavelength nanoscale optical devices due to their strong field confinement and low damping. Among these nanoscale optical devices, band-pass filter for wavelength selection and noise filtering are key devices in an integrated optical circuit. However, plasmonic filters are still oversized because large resonant cavities are needed to perform frequency selection. Here, an ultra-compact filter integrated in a graphene plasmonic waveguide was designed, where a rectangular resonant cavity is inside a graphene nanoribbon waveguide. The properties of the filter were studied using the finite-difference time-domain method and demonstrated using the analytical model. The results demonstrate the band-pass filter has a high quality factor（20.36） and electrically tunable frequency response. The working frequency of the filter could also be tuned by modifying the cavity size. Our work provides a feasible structure for a graphene plasmonic nano-filter for future use in integrated optical circuits.

Subwavelength filter and sensor design based on end-coupled composited ring-groove resonator

A plasmonic filter and sensor is designed based on an end-coupled ring-groove composited resonator(RGCR).According to the magnetic field distributions of the resonance modes,a horizontal or vertical groove is added to the perfect ring resonator,and the transmission peaks for the 1st and the 2nd modes can be linearly changed by the length of the groove.In this case,the proposed structure can act as an on-chip optical filter with flexible wavelength manipulation.When the groove is rotated with an angle of?/4,Fano resonance arises due to the mode interference.Dual asymmetric sharp transmission peaks are achieved around the wavelength of the former 2nd resonance mode.High figure of merit and high sensitivity are obtained for the structure,and it is believed that the device can find widely applications in the biochemistry sensing area.The corresponding spectra and the propagation characteristics are numerically investigated by using the finite-difference time-domain method.

Angle robust transmitted plasmonic colors with different surroundings utilizing localized surface plasmon resonance

Color filters in different surroundings inherently suffer from angular sensitivity,which hinders their practical applications.Here,we present an angle-insensitive plasmonic filter that can produce different color responses to different surrounding environments.The color filters are based on a two-dimensional periodically and randomly distributed silver nanodisk array on a silica substrate.The proposed plasmonic color filters not only produce bright colors by altering the diameter of the Ag nanodisk,but also achieve continuous color palettes by changing the surrounding environment.Due to the weak coupling between the metallic nanodisks,the plasmonic color filters can enable good incident angle-insensitive properties(up to 30°).The strategy presented here could exhibit robust and promising applicability in anti-counterfeiting and imaging technologies.