A Dual-Stage Photonic Integrated Circuit Spectrometer

Spectrometers are key laboratory tools for many applications, from molecular identification and quantification to laser diagnostics. Addressing these applications in field-deployable scenarios requires significant size, weight, and power (SWaP) reduction from typical bulk-optic techniques. Photonic integrated circuits (PICs) are an attractive alternative to bulk-optic spectrometers because they are extremely low SWaP, are readily mass- produced, and can be ruggedized for field deployment. However, typical PIC-based spectrometers are unable to simultaneously deliver the resolution and bandwidth required for key applications such as Raman spectroscopy. Within the molecular “fingerprinting” region using a 780-nm pump wavelength, a Raman spectrometer must respond between 810–890 nm with sub-nanometer resolution. To address this application, I will present a photonic integrated circuit spectrometer that cascades an arrayed-waveguide grating with a series of coupled- resonator optical waveguide filters to achieve a spectral resolution of 0.35 nm over a bandwidth from 805–930 nm. Our team’s cascaded dual-stage spectrometer design permits simultaneous wide bandwidth and high resolution performance in a package that represents multiple orders of magnitude reduction in SWaP compared to free-space spectrometers. In this talk, I will discuss the simulation, design, and testing of our integrated circuit spectrometer as well as potential applications of our team’s technology.