Two compact structures for perpendicular coupling of optical signals between dielectric and photonic crystal waveguides

Two structures are analyzed with numerical modeling as candidates for perpendicular coupling of optical signals from a dielectric waveguide to a photonic bandgap (PBG) waveguide. The first consists of a perfectly electric conducting (PEC) grating and PBG mirror to couple power out of the dielectric waveguide, along with a circular-like lens to couple that power into the PBG waveguide. The second consists of a slanted inline fiber Bragg grating to couple power out of the dielectric waveguide, and a graded-index (GRIN) lens to couple that power into the PBG waveguide. Power transfer efficiencies of 50% and 71%, respectively, are reported. Such structures would be useful in WDM applications, and/or where circuit real estate restrictions demand coupling perpendicular to the dielectric guide over small distances.