Time-domain terahertz optoacoustics: manipulable water sensing and dampening

• Published in: Advanced photonics Vol. 3; no. 2; p. 026003
• Main Authors: Li, Jiao, Yao, Yixin, Jiang, Liwen, Li, Shuai, Yi, Zhihao, Chen, Xieyu, Tian, Zhen, Zhang, Weili
• Format: Journal Article
• Language: English
• Published: Bellingham Society of Photo-Optical Instrumentation Engineers 01.03.2021; S P I E - International Society for
• Subjects: Absorption; Aqueous solutions; Biomolecules; Dynamic structural analysis; Energy; Heat; Lasers; Molecular interactions; Parameter sensitivity; Proteins; Radiation; Sensors; Silicon wafers; Spectroscopy; Spectrum analysis; Terahertz frequencies; Thickness; Time domain analysis; terahertz pulse; label-free; water; time-domain detection; terahertz optoacoustics
• ISSN: 2577-5421; 2577-5421
• DOI: 10.1117/1.AP.3.2.026003

Radiation at terahertz frequencies can be used to analyze the structural dynamics of water and biomolecules, but applying the technique to aqueous solutions and tissues remains challenging since terahertz radiation is strongly absorbed by water. While this absorption enables certain analyses, such as the structure of water and its interactions with biological solutes, it limits the thickness of samples that can be analyzed, and it drowns out weaker signals from biomolecules of interest. We present a method for analyzing water-rich samples via time-domain terahertz optoacoustics over a 104-fold thickness ranging from microns to centimeters. We demonstrate that adjusting the temperature to alter the terahertz optoacoustic (THz-OA) signal of water improves the sensitivity with which it can be analyzed and, conversely, can reduce or even “silence” its signal. Temperature-manipulated THz-OA signals of aqueous solutions allow detection of solutes such as ions with an order of magnitude greater sensitivity than terahertz time-domain spectroscopy, and potentially provide more characteristic parameters related to both terahertz absorption and ultrasonic propagation. Terahertz optoacoustics may be a powerful tool for spectroscopy and potential imaging of aqueous solutions and tissues to explore molecular interactions and biochemical processes.