Polarization-independent wavelength filter based on dual asymmetric long-period gratings in channel waveguides

Abstract

Channel waveguides with asymmetric long period gratings exhibiting coupling from the fundamental (symmetric) core mode to the first-order (antisymmetric) cladding mode were analyzed. Using this geometry, we show that it is possible to realize polarization-dependent and polarization-independent operations at desired wavelengths. We have chosen the device parameters to demonstrate its operation in the CþL band. Sensitivity of the coupling behavior to random variation in various parameters such as core and cladding dimensions, grating period, etc., has been analyzed. The proposed structure should be interesting from the point of view of realizing waveguide devices such as filters, polarizers, etc., based on waveguide gratings.

Polarization-based refractive index sensor using dual asymmetric long-period gratings in ridge waveguides

“…We also observe that the cladding mode extends deeper into the ambient whereas the core mode remains predominantly confined. It may be pointed out that the authors have previously discussed a similar scheme [21] to realize polarization-based filters. The scheme proposed in this paper switches to a ridge structure from a channel structure mentioned in the reference.…”

“…All the coupling coefficient integrals depend on the amplitude of the index modulation and the field overlap between core and the cladding modes in the grating region. Since Δn is not a symmetric function of x, the coupling coefficient from the symmetric core mode to antisymmetric cladding mode is nonzero and thus leads to existence of coupling between symmetric and antisymmetric modes [21].…”

“…To study the phase-matching behavior for the geometry, we consider an LPWG with strength (peak index modulation) Δn 5 × 10 −3 in one of the claddings. As mentioned before, the structure becomes asymmetric, thus there exists finite coupling coefficient between symmetric core mode and antisymmetric cladding mode as well [21]. Figure 3 shows the phase-matching curves for different cladding thicknesses when core mode couples into the second cladding mode (corresponding to m 3).…”

Two-port connecting-layer-based sandwiched grating by a polarization-independent design

“…Polarization-independent gratings are performed as the critical optical periodic devices, which can be applied in the energy harvesting, nonlinear optics 1 , solar cells 2 , writing fiber Bragg applications 3 , liquid crystal-polymer composite 4 , filters 5 – 10 . In the reported studies, two-port polarization-independent gratings are investigated, where characteristics of high efficiency and broad bandwidth were exhibited.…”