Study Of Wideband Slow Light Based On Photonic Crystal And Surface Plasmon Polariton

Broadband and integration are considered to be inevitable trend for thedevelopment of optical communication devices and subsystem. Meanwhile,optical packet switching is a necessary requirement for the development ofoptical network, holding a lot of basic functions including demultiplex/multiplex, switching, routing and amplification. In addition to these functions,optical bufferring is also regarded as another important function for core nodefacilities, integrated optical add-drop multiplexer and optical cross connecter.Currently, the achievement of optical buffer is mainly based on slow lighteffect that can be realized by a lot of technologies includingelectromagnetically induced transparency (EIT), stimulated Brillouinscattering (SBS), photonic crystal waveguide (PhCW) and surface plasmonwaveguide (SPPW). In these techniques, the EIT and SBS are not suitable forlarge-scale integration of broadband photonic devices at room temperature.Thus, this dissertation will focus on the research of slow light effect based onhighly integrated PhCW and SPPW featuring broadband, low dispersion and low loss.Main research achievements are as follows:1. Low dispersion photonic crystal slow light waveguideIn the first topic, two broadband and low dispersion photonic crystal slowlight waveguides with flat photonic bands are proposed originally based onthe anti-crossing mechanism of photonic bands by optimizing the structureparameters.1) The air-ring photonic crystal waveguide is proposed to achieve the slowlight with group velocity of 0.0178c and ultralow second-order dispersionwithin bandwidth of 2.9THz. Liquid crystal-modulated photonic crystalwaveguide can be designed to hold low second-order and third-orderdispersions. Numerical results show that Gaussian pulse with initial widthof 0.4ps can preserve its waveform in 480um-long waveguide withgroup velocity of 0.0239c.2) Photonic crystal slow light waveguide with high coupling efficiency.How to enhance the coupling efficiency becomes the most importantissue that should be solved for the photonic crystal slow light waveguide.In this dissertation, numerical results indicate the coupling layer can beexplored to enhance the coupling efficiency more than 80% between theinput stripe waveguide and photonic crystal slow light waveguide within bandwidth of 1.08THz corresponding to group velocity of 0.0166c.2. Slow light enhancement of optical bistabilitySlow light effect can be used to enhance light-matter interaction, presentingmany opportunities for exploring new functionalities in nanophotonicintegrated circuits. In this dissertation, the limitation induced bywaveguide-cavity coupled system is studied firstly and two schemes areproposed to break this limitation.1) The first scheme is by designing photonic-crystal cavity with asymmetrymode to achieve low-threshold optical bistability. Results indicate that thethreshold of optical bistability decreases greatly as the resonant frequencyof the cavity moves to the band edge of the waveguide mode.2) The second scheme proposes the cancellation of scattering mode in cavityto achieve the slow light enhancement of optical bistability .3. Slow light effect in coupled structure based on surface plasmonicpolaritionFor slow light waveguide, there is another key problem that must beconsidered: the loss in slow light devices. Thus, this topic is all-opticalanalogue to coherent interference phenomena in atomic systems includingFano interference and EIT.1) The optical analogue to Fano effect is studied in an optical system consisting of a metal cavity and silicon grating. Numerical results showthat the coherent interference can gives sharp and asymmetric Fanolineshape corresponding to group velocity of 0.005c and transmittance of80%.2) Another coherent interference phenomenon is also studied in coherentlycoupled structure. Numerical results show that the introduction of thesecond-order EIT effect can substantially reduce the group velocity into0.002c with transmittance of 80%.