Broadband, High Resolution, Sensitive Spectrometer Using an Integrated Optical Phased Array in Silicon Nitride and Fourier Imaging

Abstract

We present a novel hybrid configuration of a spectrometer consisting of an integrated Si3N4 optical phased array and a free-space Fourier-space imaging system. It combines broadband and high resolution performance in a small on-chip footprint. We achieve 0.5 nm resolution in a spectral range from 750 nm to 850 nm using an on-chip footprint of 0.56 × 0.22 mm2. As a proof of concept, we retrieve the optical spectrum of a single frequency titanium sapphire laser. Using an image sensor cooled down to −20 ∘C, the low detection limit is validated by measuring the optical spectrum of the Raman background generated by a laser pump propagating in a Si3N4 waveguide.