Enhancement of Terahertz Radiation from Saccharide Solutions Induced by Femtosecond Laser Pulses

Liquid is a promising candidate for terahertz radiation induced by femtosecond laser pulses, since it has advantages of higher molecular density, lower ionization potential and better self-healing properties compared with gases. In this work, an enhancement of terahertz radiation from saccharide solutions induced by femtosecond laser pulses is demonstrated, and the characteristics of terahertz radiation from saccharide solutions of different types and concentrations are investigated. It shows that terahertz radiant power from a glucose solution is 2 times higher than that from liquid water under the same excitation conditions. Among all the saccharide solutions studied, polysaccharides radiate the most powerful terahertz pulses and monosaccharides show the weakest radiation. The optimal solution concentrations of polysaccharide and disaccharide for terahertz radiation are 5% and 30%, respectively. As for monosaccharide solutions, when the concentration of the solution increases in the range of 0–30%, the power of terahertz radiation increases. In addition, quantum chemical calculations are carried out in this study to help explain the mechanisms for terahertz radiation from saccharide solutions. It is demonstrated that the power of terahertz radiation from saccharide solutions is roughly positively correlated with molecular qualities, densities, and viscosities of saccharide solutions, while negatively correlated with the band gap.