Bandpass filters based on phase-shifted photonic crystal waveguide gratings

Abstract

In this paper, a bandpass transmission filter realized in phase-shifted waveguide gratings based on photonic crystals (PCs) is proposed. Phase-shift regions each composed of one period of photonic crystal (PC) waveguide are incorporated into PC waveguide gratings. The magnitudes of the phase-shifts are modified by involving small changes in the size of the border rods in the phase-shift regions. Using standard coupled-mode theory and finite-difference time-domain (FDTD) method, we show that by properly choosing the magnitudes of phase-shifts and the lengths of waveguide gratings, a flat-top and sharp roll-off response with a narrow bandwidth is theoretically and numerically achieved by the designed filter. A further analysis shows that the center frequency of the transmission band can be changed by altering the magnitude of the phase-shift and the response performance exhibits relaxed sensitivity to the phase-shift variation. As a specific application, we theoretically demonstrate a third-order Chebyshev bandpass filter based on compound phase-shifted PC waveguide gratings. The filter performance is suitable for dense wavelength-division-multiplexed (DWDM) optical communication systems with a channel spacing of 100-GHz.

Temporal coupled mode analysis of one-dimensional magneto-photonic crystals with cavity structures

“…In general, a lightwave is elliptically polarized and its electric filed vector traces an ellipse in the plane perpendicular to the propagation direction. For an elliptically polarized wave propagating along the z-axis [ (8) in which, 0 s and  are common amplitude and phase factors for both x and y components. The orientation angle is defined as the angle of the major axis of the polarization ellipse measured from the x-axis.…”

“…Introducing a defect into a PC would let the propagation of the photons with a specific wavelength in the PBG thorough an optical resonance. Various optical components, such as filters, couplers, switches, multi/demultiplexers, power splitters, logic gates, etc., can be realized utilizing the properties of PCs [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. In order to achieve more peculiarities from PCs, 2 different kinds of materials have been inserted into them.…”

Equivalent Circuit Model for Designing Coupled Resonators Photonic Crystal Filters

“…A third-order filter [8,9] and an N-coupled-resonators filter [10] have been designed for improving the filtering performance. Presently, an approach based on the time domain coupled-mode theory (CMT) [11] was adopted for analyzing and designing many types of filters [12][13][14][15] including the coupledresonators PC filters [9]. Based on the CMT method, the coupling between two resonators can be treated as if the resonators interact through a waveguide with a phase shift.…”

A Compact Double Phase-Shifted Photonic Crystal Filter

“…The PCF consist of an array of air/dielectric filled holes running along its length and it has many unique properties which are not realizable in traditional optical fibers such as endless single mode operation, high birefringence and low nonlinearity, low dispersion etc. [5]- [1]. The parameters that affect the dispersion of the PCF include its profile shape, number of air holes, distance between two adjacent air holes and diameter of the air holes [1].…”

“…By introducing a series of 1D periodic sections separated by phase-shift regions and by properly choosing their locations and magnitudes, a nearly rectangular shape of the band pass transmission spectrum [12] can be obtained, however, at the cost of an increased device length.so, a band pass transmission filter based on 2D photonic crystals including multiple phaseshifted waveguide gratings was presented [5]. By means of an appropriate choice of the magnitude of the phase-shifts and the lengths of the waveguide gratings a nearly flat-top is achieve.…”