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Register a new userTransmission properties in waveguides: An optical streamline analysis
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A novel approach to study transmission through waveguides in terms of optical streamlines is presented. This theoretical framework combines the computational performance of beam propagation methods with the possibility to monitor the passage of light through the guiding medium by means of these sampler paths. In this way, not only the optical flow along the waveguide can be followed in detail, but also a fair estimate of the transmitted light (intensity) can be accounted for by counting streamline arrivals with starting points statistically distributed according to the input pulse. Furthermore, this approach allows to elucidate the mechanism leading to energy losses, namely a vortical dynamics, which can be advantageously exploited in optimal waveguide design.
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We introduce a weakly coupled photonic crystal waveguide as a promising and realistic model for all-optical amplification. A symmetric pillar type coupled photonic crystal waveguide consisting of dielectric rods periodically distributed in a free space is proposed as all-optical amplifier. Using the unique features of the photonic crystals to control and guide the light, we have properly chosen the frequency at which only one mode (odd mode) becomes the propagating mode in the coupled photonic crystal waveguide, whereas another mode (even mode) is completely reflected from the guiding structure. Under this condition, the all-optical amplification is fully realized. The amplification coefficient for the continuous signal and the Gaussian pulse is calculated.
All-optical amplification of the light pulse in a weakly coupled two nonlinear photonic crystal waveguides (PCWs) is proposed. We consider pillar-type PCWs, which consist of the periodically distributed circular rods made from a Kerr-type dielectric material. Dispersion diagrams of the symmetric and antisymmetric modes are calculated. The operating frequency is properly chosen to be located at the edge of the dispersion diagram of the modes. In the linear case no propagation modes are excited at this frequency, however, in case of nonlinear medium when the amplitude of the injected signal is above some threshold value, the solitons are formed and they are propagating inside the coupled nonlinear PCWs. Near field distributions of the light pulse propagation inside the coupled nonlinear PCWs and the output powers of the registered signals are studied in a detail. The amplification coefficient is calculated at the various amplitudes of the launched signal. The results vividly demonstrate the effectiveness of the weakly coupled nonlinear PCWs as all-optical digital amplifier.
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Proposed all optical amplification scenario is based on the properties of light propagation in two coupled subwavelength metallic slab waveguides where for particular choice of waveguide parameters two propagating (symmetric) and non-propagating (antisymmetric) eigenmodes coexist. For such a setup incident beams realize boundary conditions for forming a stationary state as a superposition of mentioned eigenmodes. It is shown both analytically and numerically that amplification rate in this completely linear mechanism diverges for small signal values.
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