Fully packaged on-chip ring resonator spectrometer.

On-chip optical spectrometers are key components in miniaturized optical sensing for mobile platforms, the internet of things, and chip-based diagnostics. However, current on-chip spectrometers still require a large footprint with off-chip unpackaged detectors or a large number of dispersive elements to increase the resolution power. Here, we demonstrate a randomly selected radius ring resonator spectrometer that is fully packaged with a working bandwidth of at least 120 nm and an optical resolution of 0.2 nm. By generating a calibration matrix, resonance shifts due to fabrication variations are no longer essential in the performance. The spectrometer starting wavelength, wavelength span, and scanning interval are software-defined by choosing the appropriate calibration matrix. With compressed sensing algorithms, we are able to reconstruct up to 1200 spectral channels with only 36 spatial channels. The fully packaged and especially the optoelectronic integration configuration further reduce the overall size of the whole system and enhance the measurement repeatability and stability.