Coated Spintronic Emitters for Improved THz Time-domain Spectroscopy

Abstract

Spintronic metal thin films excited by femtosecond laser pulses have proven to be excellent sources of broadband THz radiation, making these emitters increasingly popular for THz spectroscopy. Unfortunately, a significant proportion of the incident excitation laser is transmitted through the spintronic emitters, which can inadvertently photoexcite samples or cause damage to elements of the spectrometer. Here, we demonstrate a high-reflectivity coating made from alternating layers of SiO2 and Ta2 O5 that effectively blocks the incident excitation pulse and enhances the peak THz electric field by roughly 35%. We further improve the emitter performance with an anti-reflective coating. We find spintronic emitters with both coatings exhibit over 40% improvement in peak THz electric field compared to an uncoated emitter and transmit less than 0.1% of the excitation laser pulse. Show more