10.1021/acsphotonics.8b00313.s001 Chenghao Wan Chenghao Wan Erik H. Horak Erik H. Horak Jonathan King Jonathan King Jad Salman Jad Salman Zhen Zhang Zhen Zhang You Zhou You Zhou Patrick Roney Patrick Roney Bradley Gundlach Bradley Gundlach Shriram Ramanathan Shriram Ramanathan Randall H. Goldsmith Randall H. Goldsmith Mikhail A. Kats Mikhail A. Kats Limiting Optical Diodes Enabled by the Phase Transition of Vanadium Dioxide American Chemical Society 2018 Optical Diodes Enabled VO 2 phase transition vanadium dioxide index orders incident-direction-dependent absorption VO 2 layer free-space wavelength proof-of-concept device nonlinear device Vanadium Dioxide diode broadband operation incident intensity field enhancement Phase Transition light incident phase-transition material VO 2 film 2018-06-20 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/Limiting_Optical_Diodes_Enabled_by_the_Phase_Transition_of_Vanadium_Dioxide/6685553 A limiting optical diode is an asymmetric nonlinear device that is bidirectionally transparent at low power but becomes opaque when illuminated by sufficiently intense light incident from a particular direction. We explore the use of a phase-transition material, vanadium dioxide (VO<sub>2</sub>), as an active element of limiting optical diodes. The VO<sub>2</sub> phase transition can be triggered by optical absorption, resulting in a change in refractive index orders of magnitude larger than what can be achieved with conventional nonlinearities. As a result, a limiting optical diode based on incident-direction-dependent absorption in a VO<sub>2</sub> layer can be very thin, and can function at low powers without field enhancement, resulting in broadband operation. We demonstrate a simple thin-film limiting optical diode comprising a transparent substrate, a VO<sub>2</sub> film, and a semitransparent metallic layer. For sufficiently high incident intensity, our proof-of-concept device realizes broadband asymmetric transmission across the near-infrared, and is approximately ten times thinner than the free-space wavelength.