The efficiency of terahertz radiation generated by two chirped femtosecond laser pulses at different pulse durations

A high optical-to-terahertz (THz) energy conversion efficiency is essential for the production of high-power ultra-broadband THz waves. In this work, we study the efficiency of THz radiation produced by two chirped femtosecond laser pulses in an air plasma. The primary objective is to compare the role of a chirped pulse with that of a non-chirped pulse in the conversion efficiency of the generated THz radiation and to examine the effect of increasing the initial duration of the pulse. Therefore, using the photocurrent model, we numerically evaluate the energy conversion efficiency of the generated THz radiation as a function of the input intensity for selected chirped and non-chirped pulse profiles with varying initial pulse durations. The obtained numerical results demonstrate the advantage of chirped over non-chirped pulses in enhancing the efficiency of the generated THz radiation within the 1013–1015 W/cm2 input intensity range. Moreover, with increasing pulse duration, the efficiency of the chirped pulse increases, reaching a conversion rate of 10−4.