We investigate terahertz emission from two-color femtosecond-laser-induced microplasmas. Under the strongest focusing conditions, microplasmas are shown to act as point sources for broadband terahertz-to-far-infrared radiation, where the emission bandwidth is determined by the gas pressure. Semi-analytical modeling allows us to identify scaling laws with respect to the plasma dimensions. We find that the optical-to-THz conversion efficiency depends crucially on the focusing conditions. We use this insight to demonstrate by means of Maxwell-consistent three-dimensional simulations that, for only $10\mu \mathrm{J}$ laser pulse energy a conversion efficiency well above ${10}^{-4}$ can be achieved.

• Received 31 March 2017

DOI:https://doi.org/10.1103/PhysRevA.96.053814