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  4. Optical damage thresholds of single-mode fiber-tip spintronic terahertz emitters
 
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June 24, 2024
Journal Article
Title

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

Abstract
Spintronic terahertz emitters (STEs) are gapless, ultrabroadband terahertz sources that can be driven within a wide pump-wavelength and repetition-rate range. While STEs driven by strong pump lasers operating at kilohertz repetition rates excel in generating high electric field strengths for terahertz spectroscopy or ellipsometry, newly advancing technologies such as ultrafast modulation of terahertz polarization, scanning tunneling microscopy, laser terahertz emission nanoscopy, and fully fiber-coupled integrated systems demand an STE pumping at megahertz repetition rates. In all these applications the available terahertz power is ultimately limited by the STE’s optical damage threshold. However, to date, only very few publications have targeted this crucial topic and investigations beyond the kilohertz repetition-rate regime are missing. Here, we present a complete study of our single-mode fiber-tip STEs’ optical damage thresholds covering the kilohertz, megahertz, and gigahertz repetition-rate regimes as well as continuous-wave irradiation. As a very important finding, we introduce the necessity of classifying the optical damage threshold into two regimes: a low-repetition-rate regime characterized by a nearly constant fluence threshold, and a high-repetition-rate regime characterized by an antiproportional fluence dependence ("average-power threshold"). For our single-mode fiber-tip STEs, the transition between these regimes occurs around 4 MHz. Moreover, we present a cohesive theory of the damaging thermodynamical processes at play and identify temperature-driven inter-layer diffusion as the primary cause of the STE failure. These findings are substantiated by atomic force microscopy, infrared scattering-type scanning near-field optical microscopy, and scanning transmission electron microscopy measurements. This new level of understanding offers a clear optimization lever and provides valuable support for future advancements in the promising field of spintronic terahertz emission.
Author(s)
Paries, Felix
Fraunhofer-Institut für Techno- und Wirtschaftsmathematik ITWM  
Selz, Felix
Fraunhofer-Institut für Techno- und Wirtschaftsmathematik ITWM  
Santos, Christiane  
Universidade Federal Rural do Semi-Árido
Lampin, Jean-Francois
Koleják, Pierre  
VSB - Technical University of Ostrava, Institute of Electronics, Microelectronics and Nanotechnology
Lezier, Geoffrey  
Troadec, David  
IEMN - CNRS
Tiercelin, Nicolas  
Université de Lille
Vanwolleghem, Mathias  
Addda, Ahmed
Kampfrath, Tobias  
Freie Universität Berlin
Seifert, Tom
Freymann, Georg von  
Fraunhofer-Institut für Techno- und Wirtschaftsmathematik ITWM  
Molter, Daniel  
Fraunhofer-Institut für Techno- und Wirtschaftsmathematik ITWM  
Journal
Optics Express  
Open Access
DOI
10.1364/OE.525747
Language
English
Fraunhofer-Institut für Techno- und Wirtschaftsmathematik ITWM  
Keyword(s)
  • Spintronic terahertz emitters (STEs)

  • pump-wavelength and repetition-rate range

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