Enhancing Terahertz Magneto-Optical Effects in Wafer-Scale RIG Single Crystal Thick Films with Anti-Reflective Coatings for Improved Transmittance

Abstract

Wafer-scale RIG single crystal thick films were fabricated on 3-inch GGG substrates using liquid phase epitaxy. The terahertz transmittance of the RIG crystals improved after removing the GGG substrate by polishing. The time-domain spectra at THz frequencies indicate the existence of a magneto-optical effect in RIG samples. The results indicate that the RIG samples exhibit a high refractive index of approximately 4.50 within the 0.1-1.0 terahertz frequency range, a transmittance of around 40%, and an absorption rate of only 10-50 cm-1. The Faraday rotation angles of the thick single-crystal films of the RIG samples were measured using a THz-TDS system. The RIG has a thickness of approximately 330 um. The Faraday rotation angles of RIG crystals at Terahertz frequencies can reach up to 16° when an external magnetic field of 0.18 T is applied. The Verdet constants of the RIG sample were calculated to be approximately 120°/mm/T. To improve the transmittance of the RIG sample, epoxy resin and TPX were used as anti-reflective films. The transmittance of the RIG sample increased by approximately 5% for the 80 um thick epoxy and about 10% for the 320 um thick TPX. Therefore, this RIG single crystal thick film can achieve a low loss, high transmittance, and a strong magneto-optical effect in the terahertz region with the cooperation of a reflection-reducing film. It is expected to have wide applications in terahertz magnetic polarization conversion, non-reciprocal phase shifters, and isolators.