Study of terahertz emission from nickel (Ni) films of different thicknesses using ultrafast laser pulses

Abstract

The nickel (Ni) films of three different thicknesses, 65 nm, 135 nm and 1018 nm, were deposited by the RF magnetron sputtering technique. These films were subjected to femtosecond laser pulses of ~140 fs duration at 80 MHz repetition rate for generation of terahertz (THz) radiation. The obtained electromagnetic radiation was detected using photoconductive antennas by a sampling technique. The THz generation mechanism of Ni films is attributed to the ultrafast demagnetization process and its time depends on the Gilbert damping factor. The ascertained values of the Gilbert damping parameter of Ni films using ferromagnetic resonance (FMR) measurements lies between 0.011 and 0.0069. We have observed that the amplitude of emitted THz radiation from Ni films is proportional to Gilbert damping factor of films. The amplitude of emitted THz radiation from 65 nm Ni film is 1.19 and 1.66 times higher than 135 and 1018 nm films.