Integrated Photonic Spectroscopy: Applying the Digital Fourier-Transform Spectrometer

Abstract

The digital Fourier-Transform (dFT) spectrometer is a promising on-chip spectrometer architecture that offers exponential scaling for resolution with a compact device footprint. A package of scripted modules employs object-oriented programming to automate creating the mask layout and streamline the dFT design process. Moving towards longer infrared wavelengths with broadband devices expand the sensing capabilities by accessing stronger chemical absorption signatures associated with the fingerprint regime. The second generation of dFT devices realizes two high-resolution, 1024-channel spectrometers. The first device operates around 1550 nm and fully utilizes foundry standard components and processes. The second device achieves half-octave operation between 1620 - 1750 nm with the use of custom broadband adiabatic couplers. The next set of designs push beyond the telecom range, combining two dFT devices on a single chip for 1.2 - 2.4 µm operation. Ultrabroadband single-mode waveguides and custom adiabatic couplers were designed for each device on this chip. All four of the discussed designs use the SOI material platform and are compatible standard foundry processes.