Optical damage thresholds of single-mode fiber-tip spintronic terahertz emitters

• DOI: 10.1364/oe.525747
• Publication Date: 2024-05-06T13:00:10Z
• Authors: Felix Paries; Felix Selz; Cristiane N. Santos; Jean-François Lampin; Pierre Koleják; Geoffrey Lezier; David Troadec; Nicolas Tiercelin; Mathias Vanwolleghem; Ahmed Addda; Tobias Kampfrath; Tom S. Seifert; Georg von Freymann; Daniel Molter
• Keywords: 0103 physical sciences; 01 natural sciences

Spintronic terahertz emitters (STEs) are gapless, ultrabroadband sources that can be driven within a wide pump-wavelength and repetition-rate range. While STEs by strong pump lasers operating at kilohertz repetition rates excel in generating high electric field strengths for spectroscopy or ellipsometry, newly advancing technologies such as ultrafast modulation of polarization, scanning tunneling microscopy, laser emission nanoscopy, fully fiber-coupled integrated systems demand an STE pumping megahertz rates. In all these applications the available power is ultimately limited STE’s optical damage threshold. However, to date, only very few publications have targeted this crucial topic investigations beyond regime missing. Here, we present complete study our single-mode fiber-tip STEs’ thresholds covering kilohertz, megahertz, gigahertz regimes well continuous-wave irradiation. As important finding, introduce necessity classifying threshold into two regimes: low-repetition-rate characterized nearly constant fluence threshold, high-repetition-rate antiproportional dependence ("average-power threshold"). For STEs, transition between occurs around 4 MHz. Moreover, cohesive theory damaging thermodynamical processes play identify temperature-driven inter-layer diffusion primary cause failure. These findings substantiated atomic force infrared scattering-type near-field transmission electron microscopy measurements. This new level understanding offers clear optimization lever provides valuable support future advancements promising spintronic emission.