Mode Management And Application In Plasmonic Waveguide

Integrated optics is one of the rapidly developing research directions in recent years,with integrating various kinds of functional modules into one optical chip as the ultimate goal,thereby making information processing to have the characteristics of adaption to environment simultaneously high power density and low energy consumption.Due to the restriction of optics diffraction limit in conventional dielectrical integration,integrated chip encounters challenge miniaturization and integration.While plasmonic waveguides can break through diffraction limit which provides a new approach to improve the optics integration level.The attention has been focused on plasmonic waveguide device design and hope has been placed on device function and on-chip interaction.The dissertation is constructed as follows:1.We report a direct observation of guided-mode interference in polymer-loaded plasmonic waveguides by the technique of leakage radiation microscopy(LRM).Spatial beating patterns of the interferences were clearly characterized with respect to different structural parameters,and the interference properties were analyzed in detail.Besides,the capability of LRM for characterizing the multiple modes was also discussed extensively.Our finding not only offers an efficient technique in analyzing the guided modes and their interference,but also provides a definite guideline in evaluating the validity of LRM and deepens further studies on the dielectric-loaded hybrid waveguide system.2.A mode division multiplexer(MDM)based on in-plane diffractions is experimentally demonstrated in a polymer loaded plasmonic planar waveguide.Three guided modes(TMi,TEi,and TM2)were well demultiplexed by a focusing design with a focal length of about 40 μm,which are clearly distinguished by the polarization control.The experimental results well reproduced the theoretical design and calculation.Moreover,the demultiplexed focal spots directly reflect the different modes,by which a mode diagram of the dielectric-loaded planar waveguide was vividly mapped out by varying the polymer layer thickness.In this regard,the proposed device may not only serve as a MDM for the integrated optics but can also provide a new strategy in analyzing the guided modes.3.Recent realization of non-trivial topological phases in photonic systems has provided unprecedented opportunities in steering light flow in novel manners.Based on the Su-Schriffer-Heeger(SSH)model,a topologically protected optical mode was successfully demonstrated in a plasmonic waveguide array with a kinked interface that exhibits a robust nonspreading feature.However,under the same excitation condition,another anti-kinked structure seemingly cannot support such a topological interface mode that appears to be inconsistent with the SSH model.Theoretical calculations are carried out based on the coupled mode theory,in which the mode properties,excitation conditions,and the robustness are studied in detail.It is revealed that under the exact eigen-state excitations,both kinked and anti-kinked structures do support such robust topological interface modes,however,for a realistic single-waveguide input only the kinked structure does.It is concluded that the symmetry of interface eigen modes plays a crucial role,and the odd eigen mode in kinked structure offers capacity to excite the nonspreading interface mode in the realistic excitation of one-waveguide input.Our finding deepens the understanding of mode excitation and propagation in coupled waveguide system,and would open a new avenue in optical simulations and photonic designs.4.Surface plasmon polariton(SPP)has shown its merits in strong field enhancement and high confinement even beyond the diffraction limit.Whereas the intriguing applications of SPPs have been demonstrated in the classical regime,their quantum properties are keenly explored in expectation of applications.Pioneering experiments have presented the preservation of the quantum properties of excited SPPs.Recently experiments have verified the bosonic nature of SPPs via on-chip non-classical interference.These investigations point to the prospectus of quantum plasmonic technologies that harness quantum effects of SPPs.Here,we report the implementation of the first plasmonic controlled-NOT(CNOT)gate.By utilizing a single polarization-dependent beam-splitter fabricated on a dielectric-loaded SPP waveguide,we realize a polarization encoding CNOT gate within several micrometers,with an estimated fidelity of 63.7%≤ Fprocess≤80.3%.Our results demonstrate the good quantum functionality by manipulating plasmonic qubits and pave a new way for future quantum information technology and quantum plasmonic science.