Terahertz waves emission by a laser pulse propagating in a gas-filled hollow-core capillary fibre

The theory of terahertz waves emission from a gas-filled hollow-core capillary fibre when a laser pulse propagates through it has been developed. The spectral, angular and energy characteristics of the terahertz pulse were studied as a function of the laser radiation duration and the parameters of the plasma column formed during optical ionisation of gas in the hollow core of a fibre. It is shown that the emission spectrum contains a broad line near a frequency comparable to the reciprocal duration of the laser pulse. The energy emitted by a laser pulse per unit path length was calculated and optimal conditions were found under which the energy has a maximum value. The spatiotemporal structure of the terahertz pulse was investigated and it was shown that the emission of terahertz waves occurs according to the Cherenkov mechanism. Estimates show the possibility of generating high-energy THz radiation pulses with high conversion rate.