Maximizing fabrication and thermal tolerances of all-silicon fir wavelength filters

Abstract — We propose a method to make silicon optical finite impulse response filters tolerant to fabrication (waveguide geometry) and ambient thermal variations. We experimen-tally demonstrate a Mach–Zehnder interferometer filter with fabrication and thermal tolerance, both separately and together. The fabrication-tolerant device measurements show a 20-fold improved tolerance to systematic waveguide linewidth variations with a wavelength shift of <60 pm/nm linewidth change. The fabrication- and thermal-tolerant device is possible using orthog-onal polarizations in the two arms. The fabricated device shows a shift of less than ±65 pm/nm and a thermal drift smaller than ±15 pm/K over a wavelength range of 40 nm. Simulations show that this concept can be extended to multichannel filters. Index Terms — Silicon photonics, wavelength filtering devices, fabrication tolerances, athermal. I