A novel plasmonic lens based on a metal–insulator–metal bus waveguide coupled to a ring resonator is proposed and numerically investigated. The inner edge of the ring resonator was perforated with nanogrooves so that light emitted by these nanogrooves was sharply focused at the center of the ring. The structure relies on interference and resonance theory. The principle of the lens can be extended to a device 1 × N demultiplexer as well as a 1 × N power splitter. These functionalities were validated through finite element method simulations. Results show that the lens had a sharp focus, without any smearing, and a full width at half maximum (FWHM) intensity of around 240 nm. For the 1 × N demultiplexer, the selectivity was high with an FWHM bandwidth of less than 20 nm and crosstalk of less than − 10 dB, whereas the 1 × N power splitter had a narrow bandwidth and was able to split power into N equal parts with negligible imbalance. The proposed focusing structure is compact, and the simulation results show that the structure performs the various functionalities with high efficiency. Due to this, these structures will be of utmost utility in future all-optical signal processing systems.
A 1 × 2 plasmonic demultiplexer with a rectangular metal-insulator-metal (MIM) waveguide comprising one input port and two output ports has been proposed. The proposed demultiplexer is based on the principle of interference of surface plasmon polariton waves. By placing the output port at the designed position along the rectangular MIM waveguide, the desired wavelength can be extracted from the mixture of the wavelengths. Results were simulated using finite element method (FEM) technique and plot of field and its intensity were obtained for both the wavelengths. The results agree with the proposed theory. Power transmission of more than 80% at the desired port with a suppression of more than 90% at the undesired port is obtained for both the wavelengths. A low crosstalk of less than −11.06 dB with a low insertion loss of less than 14.32 dB are measured. It is shown that the wavelength selectivity of the plasmonic demultiplexer is further dependent on the width of the MIM waveguide as well as the materials chosen. The design can be further extended to a 1×N demultiplexer by appropriate selection of position of the output ports.
An ultra-compact plasmonic unidirectional wavelength multiplexer/demultiplexer based on slot cavities is proposed and numerically simulated. The structure consists of slot cavities which are etched on either sides of a metal–insulator–metal (MIM) bus waveguide. The cavities capture surface plasmon polariton (SPP) waves at their resonant wavelengths and unidirectionally couples them to the drop waveguide etched parallel to the bus. The structure basically relies on resonance and interference of SPP waves and its functioning is validated through finite element method (FEM) simulations. The simulation results show that the proposed structure functions as expected with a full width at half maximum (FWHM) bandwidth of less than 50 nm, extinction ratio (ER) more than 10 dB, and crosstalk (CT) of less than − 10 dB for the designed wavelengths. The proposed structure holds lot of potential to enhance the miniaturization of ultra-compact integrated photonic circuits for optical signal processing and other related applications.
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