Terahertz optoacoustic detection of aqueous salt solutions.

Terahertz radiation has been used to detect aqueous salt solutions; however, strong absorption of water in terahertz regime limits the application of traditional terahertz techniques. Here, we present a novel method in analyzing aqueous salt solutions via terahertz optoacoustics. Terahertz optoacoustic signals can be manipulated by temperature control, which allows the dampening of water background and providing more information of solute. We demonstrate that dynamic and continuous terahertz optoacoustic detections of salt solutions with different solutes, concentrations, temperatures, and terahertz spectral frequencies shows the significant potential of this method in distinguishing different salt solutions and quantitatively analyzing salt concentrations. Terahertz optoacoustics may be a powerful tool for quantitative and label-free detection of aqueous salt solutions to further study the complicated aqueous solutions in terahertz regime.