External-Magnetic-Field-Free Spintronic Terahertz High-Field Emitters with One-dimensional Photonic Crystal Structure

Intense terahertz (THz) radiation in free space offers multifaceted capabilities for accelerating electrons, understanding mesoscale architecture in (bio)materials, elementary excitation, etc. However, the lack of high-beam-quality, high-stability, low-cost, and easy-to-implement high-field THz sources impedes the proliferation of strong-field THz applications. Recently popularized spintronic THz emitters (STEs), with their versatility, such as ultra-broadband, cost-effectiveness, large-size, and ease-for-integration, have become one of the most promising alternatives for the next generation of intense THz sources [1], [2]. Nevertheless, the typical W| Co<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">20</inf>Fe<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">60</inf>B<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">20</inf>| Pt necessitates an external magnetic field to saturate magnetization for stable operation, limiting its scalability for achieving a higher THz field with uniform distribution over larger sample areas.