On-chip silicon nitride optical phased array as a broadband near-infrared spectrometer

We demonstrate a novel spectrometer based on a hybrid guided wave and free-space optical system, consisting of a silicon nitride optical phased array (OPA), free-space grating couplers, and Fourier-space imaging to an image sensor. Each wavelength dispersed by the photonic integrated circuit corresponds to a unique position in the Fourier plane. We demonstrate the reconstruction of a spectrum in the near-infrared from the position and the intensity in this plane. From preliminary measurements on a small-sized OPA (0.1 mm(2)), we report a spectral range of 100 nm and a resolution of around 0.5 nm.