Global dynamics of a Holling Type-III two prey–one predator discrete model with optimal harvest strategy

Nonlinear Dynamics - This paper deals with a discrete-time two prey–one predator system with Holling Type-III functional response, along with inter-specific competition between the prey and...     

Anomalous behaviour in a Bragg reflection waveguide

A novel asymmetric Bragg reflection waveguide (BRW) showing anomalous dispersion characteristic is presented. The abnormal behaviour of increase of modal effective index with wavelength is primarily caused by the changes taking place in the imaginary part of the Bloch wavevector, in the periodic stratified cladding. The phase velocity and the group velocity dispersion characteristics for the waveguide have also been analyzed. Such an anomalous behaviour can find applications in the design of integrated optical devices.     

Broadening of the phase-matching bandwidth in quasi-phase-matched second-harmonic generation using GaN-based Bragg reflection waveguide

We present an analysis of a high index core symmetric Bragg reflection waveguide (BRW) design based on a GaN/AlxGa1-xN system for efficient quasi-phase-matched second-harmonic generation for broadband applications. By choosing the fundamental frequency to be a BRW mode and suitably tailoring the overall dispersion characteristics, the strong dispersion of the second-harmonic mode is partially canceled, leading to phase matching between the fundamental and second-harmonic over a broad range of wavelengths. The crucial interplay between the dispersive behavior of the fundamental and second-harmonic wave manifests as a broad acceptance bandwidth of approximately 33 nm accompanied with appreciable conversion efficiency (22.8%/W) for a 10 mm long waveguide. The impact of tailoring the dispersion characteristics on the conversion efficiency is also discussed.     

SHG in Bragg reflection waveguides for enhanced bandwidth applications

A novel scheme for second harmonic generation in asymmetric Bragg reflection waveguides is presented for enhancing the bandwidth of non-linear interaction. The strong dispersion exhibited by the Bragg reflection waveguide is exploited for countering the rapidly falling efficiency as one moves away from the phase-matching wavelength. The role of the periodic cladding on the efficiency and bandwidth of second harmonic generation in a lithium niobate based Bragg reflection waveguide is analyzed. Such an idea could be used in other parametric processes for enhancing the bandwidth and for easing fabrication tolerances.