Laser Sensor for Unattended, and Precise Determination of Calcium and Strontium in Seawater

The use of unattended floats, platforms, and drones addresses the immense challenge of cost-effectively characterizing the chemistry of the oceans. The proposed program strengthens this capability by demonstrating the feasibility of Laser Fluorescence Enhanced Flame Spectrophotometry (LFEFS) for the simultaneous and high precision measurement of calcium and strontium. These are key elements of the human food chain at risk due to ocean acidification. LFEFS offers ICP-AES-comparable precision with greater chemical selectivity and immunity to interference with compact and light weight design. The LFEFS innovation is enabled by the incorporation of the recently developed IPSSL (Intracavity Plasma Solid State Laser) platform. IPSSL is an atomic resonant wavelength laser with an embedded atomic standard. The resulting wavelength stability (ranging from 0.1 to 1 picometers) virtually eliminates wavelength drift and simplifies instrument design. High precision and signal-to-noise are promoted by (1) optical power levels sufficient to saturate the resonant transition eliminating quenching of exited atoms, and (2) operation based on ground state rather than excited state transitions. The beam can be electronically modulated for noise reduction, and no spectrometer is required. Experimental IR&D results using IPSSL-Rb are supportive of proposal contentions. A successful program will result in products for immediate commercialization.