Time-Gated Optical Oceanographic Sensors (TGOOS)

There is a need for more capable and affordable means to measure optical properties and biological constituents of marine and freshwater environments. These measures are crucial for estimating the abundance of organisms such as those producing harmful algal blooms (HABs). Affordable and effective methods to extend the measurement range and improve sensitivity of traditional optical instruments will enable scientists to greatly improve HAB prediction. The proposed research and development effort combines new Time-of-Flight (TOF) optical detectors with pulsed light sources, to produce new highsensitivity, low-noise optical sensing capabilities that can measure time-synchronized photons within an asynchronous ambient light field that includes scattered light (noise). Fluorescence produced by phytoplankton at a distance from the sensor will be determined by the time-of-flight and spatial distribution of the received photons from source-to-plankton-to-detector. The TOF sensors will use on-chip capture and accumulation of the desired signal and ambient light “snapshots”. On-chip nano-second scale time-gated accumulation will improve signal-to-noise as compared to conventional instruments, which use photodiodes and off-chip processing. Further, the proposed approach adds the capability to select measurement distance from the sensor. The project will investigate several types of TOF optical detectors and evaluate then for use as chlorophyll fluorometer sensors.