Ultrafast spintronic THz emitters and their optical damage limit

Optical damage threshold of the ultrafast spintronic THz emitters has been studied. For a given metallic spintronic heterostructure, the THz generation efficiency is related to the wavelength-dependent optical absorption. The mean value of the optical damage limit of most of the above THz emitters is found to be $\sim 60$ GW/cm2 at 800 nm exaction with 100 fs pulse at 1 kHz repetition rate. Nearly four-fold enhanced optical damage limit is observed for 1550 nm excitation as compared to the 800 nm excitation, though, the THz characteristics remain the same for both.