Integrated scanning spectrometer with a tunable micro-ring resonator and an arrayed waveguide grating

Integrated spectrometers with both wide optical bandwidths and high spectral resolutions are required in applications such as spectral domain optical coherence tomography (SD-OCT). Here we propose a compact integrated scanning spectrometer by using a tunable micro-ring resonator (MRR) integrated with a single arrayed waveguide grating for operation in the 1265–1335-nm range. The spectral resolution of the spectrometer is determined by the quality factor of the MRR, and the optical bandwidth is defined by the free spectral range of the arrayed waveguide grating. The spectrometer is integrated with on-chip germanium photodetectors, which enable direct electrical readout. A 70-nm optical bandwidth and a 0.2-nm channel spacing enabled by scanning the MRR across one free spectral range are demonstrated, which offer a total of 350 wavelength channels with 31-kHz wavelength scanning speed. The integrated spectrometer is applied to measure different spectra and the interference signals from an SD-OCT system, which shows its great potential for future applications in sensing and imaging systems.