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

A resonator array-based spectrometer for visible/near-infrared (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.