Spectral shift in terahertz emission by ultrafast laser-induced demagnetization

Abstract

We demonstrate a spectral shift in the peak frequency of terahertz (THz) emission by ultrafast laser-induced demagnetization in the Fe20Ni80 (Py) film. Experimentally, red spectral shifts of the THz emission are achieved by increasing the laser fluence or decreasing the Curie temperature of the Py film. Based on the microscopic three-temperature model, it is found that such redshifts are attributed by the slowing down of laser induced demagnetization processes in the Py film. The results not only enrich our understanding of THz emission introduced by ultrafast laser-induced demagnetization but also provide a practical way to detect the timescale of laser-induced ultrafast demagnetization dynamics.