Highly-uniform resonator-based visible spectrometer on a Si3N4 platform with robust and accurate post-fabrication trimming

A resonator array-based spectrometer for visible/nearinfrared (NIR) wavelengths is fabricated on a low-loss silicon nitride (Si3N4) material platform. Ideally, a spectrometer should uniformly sample the input spectrum. However, resonator-based spectrometers, in which each spectral sample corresponds to resonance wavelength of one of the resonators in the array, suffer from wavelength sampling non-uniformity caused by the high sensitivity of the resonant wavelengths of different resonators to the dimensional variations caused by fabrication imperfections. Using an alignment-insensitive post-fabrication trimming technique, we reduce the standard deviation (STD) of resonance wavelength of a 60-channel integrated photonic spectrometer in Si3N4 to a record-low value of 5 pm in the visible wavelength range. This approach can be used to realize wideband and uniform visible spectrometers that are desirable for applications such as optical signal processing and biological sensing. (C) 2018 Optical Society of America