Tunable Wide-Angle Tunneling in Graphene-Assisted Frustrated Total Internal Reflection

• Published in: Scientific reports 2016-01, Vol.6 (1), p.19975-19975, Article 19975
• Main Authors: Tran, Thang Q., Lee, Sangjun, Heo, Hyungjun, Kim, Sangin
• Format: Article
• Language: English
• Subjects: 639/624/1075/401; 639/925/918/1054; Graphite; Humanities and Social Sciences; multidisciplinary; Science
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/srep19975

Electrically tunable permittivity of graphene provides an excellent tool in photonic device design. Many previous works on graphene-based photonic devices relied on variable absorption in graphene, which is naturally small in the optical region and resonant structures to enhance it. Here we proposed a novel scheme to control evanescent coupling strength by inserting two graphene layers to a frustrated total internal reflection (FTIR) configuration. The resulting structure behaves in a drastically different way from the original FTIR: optical transmission though the structure can be electrically controlled from ~10 −5 to ~1 with little dependency on angle of incidence. This unique feature stems from the fact that the permittivity of doped graphene can be close to zero at a certain photon energy. The electrical controllability of evanescent coupling strength can enable novel design of optical devices. As a proof-of-concept, we designed a waveguide-type optical modulator of a novel operation principle: transmission modulation depends on the electrically controlled existence of a guided-mode of the waveguide, not the variation of the ohmic loss of graphene, resulting in a low insertion loss and a small device footprint.