Research On Surface Plasma Light Modulator

With the continuous development of communication systems,problems such as limited bandwidth and speed of electronic devices and large noise interference have gradually emerged.The photonic device has a larger communication bandwidth,faster processing speed and better anti-interference performance,but due to the existence of the diffraction limit,the volume of the traditional photonic device is relatively large and cannot be integrated in the chip.Surface plasmons can strongly confine the electromagnetic field to the metal surface,breaking the diffraction limit,so it has important applications in the field of nanophotonics.In this thesis,a new type of surface plasmon light modulator is designed on a single metal film based on surface plasmons,and the input and output are coupled through a multi-core fiber.The modulator mainly includes coupling module,polarization rotation module and modulation module,which can realize the mutual conversion between light wave and surface plasmon,polarization rotation,signal modulation and other functions,and the volume of the device is reduced by more than two orders of magnitude compared with the traditional light modulator,so it is an ideal device in modern communication system.The specific work is as follows:1.The related theories,transmission characteristics and typical waveguide structures of surface plasmons are analyzed.The first-order and second-order waveguide modes in the MIM waveguide are analyzed,and the effects of different waveguide modes on SPP excitation of metal nanogrooves and asymmetric metal nanogrooves are investigated.The directional excitation of SPP was realized by constructing an asymmetric nanocrystal by the mutual transformation between the first and second order waveguide modes.2.In the coupling module of the modulator,an asymmetric slot grating and a combined grating coupler are designed.Both gratings are designed to be vertically coupled and elliptically focused.The 1-d B coupling bandwidth of the asymmetric metal nano-groove vertical metal grating is up to 110nm in the three-dimensional model,and the coupling efficiency is up to-2.1d B when the incident wavelength is 1535nm.The combined grating is designed by using single metal nanogrooves and asymmetric metal nanogrooves,which can achieve vertical unidirectional coupling with higher coupling efficiency.The 1-d B coupling bandwidth can reach 90nm,and the maximum coupling efficiency can reach-1.8d B at the incident wavelength of 1545nm.Both gratings adopt elliptical focusing form,and the transverse size of the whole coupling module is controlled within the range of 12?m.3.The polarization rotation module and modulation module of the modulator are designed.The polarization rotation module based on the tip structure is designed to convert the surface plasmon propagated on metal surface to the horizontal alignment polarization of the MIM waveguide gap plasmon mode,and its principle is analyzed.The modulation module realizes the signal modulation,and the modulated signal is output to the optical fiber mode through the polarization rotation module and the vertical metal grating coupler.The loss of surface plasmon light modulator is 15.1d B.The length of the modulation module is only 10?m.When the modulation arm is filled with JRD1 material with an electro-optic coefficient of 343pm/V,the"push-pull"mode is adopted,and the half-wave voltage is 5V.The size of the whole device is limited in the range of 44×10?m~2,which is beneficial to integrate the device into the chip and lay a foundation for the light interconnection on the chip.