Grating-assisted InGaAsP/InP vertical codirectional coupler filter

Abstract

We report a novel wavelength selective coupler based upon grating-assisted forward coupling between two, nonidentical, vertically stacked InGaAsP/InP waveguides. Using a 14.4 μm period to provide phase matching between the asynchronous waveguides, we achieve a filter bandwidth (full width at half maximum) of 65 Å and coupling efficiency of ∼65% with a device length of only 1.0 mm.

Frequency response and tunability of grating-assisted directional couplers

“…Repeating the same calculation for the case of a singlewaveguide DBR structure results in a similar expression for the fractional center wavelength shift, except that ne, of the only waveguide of such a device appears instead of [6].) the effective refractive index difference of the two coupled waveguides in the present case.…”

“…The common mechanism utilized for that purpose employs the wavelength selectivity of backward coupling which is provided by an etched grating, namely, a distributed Bragg reflector (DBR). A related, recently demonstrated device [5]- [6] makes use of grating-assisted wavelength-selective coupling between two fonvardpropagating channel modes of a directional coupler made of two parallel waveguides. In that case, the waveguides are nonsynchronized, i.e., each one supports an optical mode with a different phase velocity.…”

Design of grating-assisted waveguide couplers with weighted coupling

“…Two of the more common configurations are a pair of parallel channel waveguides imbedded into a planar substrate (see Fig. 2), and a pair of vertically stacked planar waveguides [6]. The vertically stacked configuration is particularly well-suited for monolithically integrated optoelectronic devices, fabricated using epitaxially grown semiconductor materials.…”

“…where (6) As indicated by ( 5 ) and (6), contradirectional coupling offers much greater wavelength selectivity than is achievable with codirectional operation. Contradirectional coupling, however, requires submicron period gratings, which may be difficult to fabricate.…”

“…Contradirectional coupling, however, requires submicron period gratings, which may be difficult to fabricate. Recently, Alfemess et al [6] [12] have used the method to design parabolic CWF's. The fabrication of tapered corrugated waveguide filters suffers from practical difficulties.…”