  Anisotropy in electronic structures may ignite intriguing anisotropic optical
responses, as has been well demonstrated in various systems including
superconductors, semiconductors, and even topological Weyl semimetals.
Meanwhile, it is well established in metal optics that the metal reflectance
declines from one to zero when the photon frequency is above the plasma
frequency {\omega}p , behaving as a plasma mirror. However, the exploration of
anisotropic plasma mirrors and corresponding applications remains elusive,
especially at room temperature. Here, we discover a pronounced anisotropic
plasma reflectance edge in the type-II Weyl semimetal WP2, with an anisotropy
ratio of {\omega}p up to 1.5. Such anisotropic plasma mirror behavior and its
robustness against temperature promise optical device applications over a wide
temperature range. For example, the high sensitivity of polarization-resolved
plasma reflectance edge renders WP2 an inherent polarization detector. We
further achieve a room-temperature WP2-based optical switch, effectively
controlled by simply tuning the light polarization. These findings extend the
frontiers of metal optics as a discipline and promise the design of
multifunctional devices combining both topological and optical features.
