Research On The Sub-wavelength Metal Grating And Surface Plasmon Polaritons Frequency-selection Optical Devices

Surface plasmon polaritons sub-wavelength devices,trapping the energy of SPPs at metal surface,provids a promising solution for utilizing an nano optical device without the diffraction limit and make the designing of optical devices in the sub-wavelength scale become ture.By rational design of sub-wavelength surface plasmon polaritons optical device,phase modulating and wavelength selection is realized.Sub-wavelength metal gratings can be applied in surface plasmon polaritons frequency separator,energy coupler,optical switch,light phase modulator,sub-wavelength metal-insulator-metal waveguide.The main work in this thesis revolve sub-wavelength metal gratings and surface plasmon polaritons wavelength selection devices,the following work is systematically carried out:1.A plasmonic metal grating wavelength splitter is proposed.Based on the periodical waveguide theories,the negative real part of the propagation constant of surface plasmon polaritons(SPPs)(Re[?]<0)in metal grating is derived in a wavelength range.The transmission prohibition at the negative Re[?]is utilized to realize the wavelength splitting by the metal grating with different grating periods and fill factors on the left and right half.The metal grating plasmonic splitter is simulated by the finite difference time domain simulation method.The plasmonic wavelength splitter is fabricated by electron beam lithography and the ion beam etching process.The SPPs excited by an incident wavelength of 532 and 650 nm are experimentally split and observed under an optical microscope using a chargecoupled device camera.2.A plasmonic wavelength splitter based on a sub-wavelength metal-insulator-metal(MIM)periodic rectangle wrinkle waveguide with a graded grating coupler is proposed.The surface plasmon polaritons(SPPs),excited in the metal grating with wavelength selection,are deflected by the graded difference according to the aplanatic parametric principle.The wave vector of the deflected SPPs meets the phasematching condition and couples into the periodic rectangle wrinkle waveguide with a plasmonic bandgap.The SPPs excited by incident 650 and 832 nm were successfully split and guided to opposite directions of the MIM waveguide with extinction ratios of 27.5 dB and 32.7 dB,respectively3.A plasmonic filter based on the integration of the metal-insulator-metal(MIM)waveguide with nano-cavities is proposed.The frequency-selected transmission enhancement of the filter and the interference of the SPP cavity mode and the SPP waveguide mode is investigated by the rigorous coupled wave approach.Finite difference time domain simulation is utilized to optimize the geometrical parameters of the plasmonic filter.By electron beam lithography(EBL)and iron beam etches(IBE)process,the MIM waveguide filter with nano-cavities was fabricated on a Si02 substrate.The transmission of the filter was enhanced at 650nm.