| Surface plasmon polaritons (SPPs), which are formed by the interaction between free-electon and light, is a kind of electromagnetic wave propagating at the metal-insulator interfaces. Due to outstanding properties of SPPs such as their ability to highly confine optical waves below the diffraction limit, the size of devices based on plasmomic waveguides is subwavelength scale, which make it possible to design photonic devices at nanoscale and satisfy the need of the miniaturization and high density integration of the photonic circuit.In this thesis, we studied photonics devices of filter, waveguide crossing and all-optical logic gates based on plasmonics waveguides. The highlights of this thesis are as follows:1. A simple plasmonic filter with symmetrical tooth-shaped waveguides is proposed and investigated. It is found that the structure with a single symmetrical tooth-shaped waveguide couple can realize a tunable band-stop filter of which the stop-band is not flat. Attributed to cascaded symmetrical tooth-shaped waveguide couples, the structure can achieve a flat band-stop response with no intensity variation over the transmission spectrum. And the central wavelength of the stopband linearly increases with the simultaneous increasing of depths of waveguides. Moreover, the bandgap width of the filter can be controlled by adjusting the different length between tooth-shaped waveguides.2. We investigate the characteristics of the resonant modes in the side-coupled rectangular-ring resonator (SRR). The results show that we can manipulated the resonant wavelength of the TMa mode and TMs mode by adjusting the parameters of the ring resonator. Attributed to the splitting effect,a multi-channel band-stop filter can be achieved by a side-coupled rectangular-ring resonator. In sensing application, the proposed structure can work as a highly sensitive plasmonic nanosensor with the sensitivity of 1000 nm/RIU and the figure of merit (FOM) of 67.3. We proposed a design for MMI-based crossing for metal-insulator-metal waveguide. The crossing waveguides consist of two 1 × 1 mirror-imaged MMI structures, where the input and output single-mode waveguides are located asymmetrically at the lateral left or right sides of the MMI structures. By forming the mirror-images of the input optical field at the MMI output plane, a crossing with high throughput (-1.9 dB) and low crosstalk (-38 dB) is achieved when the work vavelength is ?=1550nm. The proposed MMI-based crossing has a broad band of -435 nm for the throughput larger than -3 dB and crosstalk less than -20dB. And the MMI-based crossing tolerates a width variation of 275 nm < Wm <295 nm for the crosstalk < -20 dB and the throughput > -3dB. These results can be useful for future integrated optical circuits.4. We studied all-optical logic gates based on MMI effect in Si-based hybid plasmonic waveguides (SHPWs). Firstly, Nano-scale Multifunctional logic gates for on-off-keyed (OOK) formats based on SHPWs are designed by utilizing the multimode interference (MMI) effect. The proposed device is based on a 3×3 MMI coupler. By setting different input signals and selecting suitable threshold value, OR, AND and XOR gates are achieved simultaneously or individually in a single device. The functional size of the device is only 1000nm×3200nm, which is much smaller than traditional Si-based all-optical logic gates. This may provide a way for ultrahigh speed signal processing and future nanophotonic integrated circuits. Secondly,we propose ultra compact all-optical logic gates based on multimode silicon hybrid plasmonic waveguides for binary-phase-shift-keyed signals.A three-dimensional finite-difference time-domain method is used for design and analysis of the logic gates. The results show that XOR, XNOR and NOT gates can be realized using a 2×2 MMI coupler with the size of 900 nm ×1120 nm. By cascading three 2×2 MMI coupler, NAND, and OR can be realized. These results can be useful for future integrated optical computing... |
PDF Full Text Request