Wide range center wavelength trimming of vertically coupled microring resonator filter by direct UV irradiation to SiN ring core

We developed a precise and wide range ultraviolet (UV) trimming of the center wavelength of vertically coupled microring resonator, by using the direct UV irradiation to the SiN ring core. We discovered that the UV-induced refractive index change of SiN was -1.3/spl times/10/sup -2/ and there was no aging of refractive index after the UV irradiation. Utilizing this phenomenon, -12.1 nm of center wavelength shift was demonstrated without the aging effect for 1200 h.