Ultra-Wideband RF-Photonics Technology for Microwave Spectrometry

We describe an RF-photonic system architecture to measure microwave spectrum over a wide bandwidth with high resolution. The approach relies on the up-conversion of the electronic signal to the optical domain using a high-speed electro-optic modulator (EOM), and an arrayed-waveguide (AWG) grating for spectral analysis. The modulator is implemented in lithium niobate whereas the AWG takes the form of a photonic integrated circuit fabricated in a silicon-on-insulator material platform. We present experimental results showing high-frequency response, in excess of 200 GHz, for the modulator, and broadband response of the AWG with the free spectral range of 81 GHz. The system is suitable for the measurement of atmospheric radiation between the oxygen and water vapor absorption lines for the monitoring of the planetary boundary layer (PBL) to aid in weather prediction and the modeling of climate dynamics.