Simple method for mitigation of polarization crosstalk in planar lightwave circuit directional couplers

Polarization crosstalk in planar lightwave circuit directional couplers can cause significant polarization-dependencies in interferometers that use them. We show a simple way to mitigate the polarization crosstalk without incurring a performance penalty or requiring extra fabrication steps. We demonstrate it on a 23-ps Mach-Zehnder delay interferometer.