An Invisible Acoustic Sensor Based on Parity-Time Symmetry
Sensing an incoming signal is typically associated with absorbing a portion of its energy, inherently perturbing the measurement and creating reflections and shadows. Here, in contrast, Prof. Andrea Alù and students Romain Fleury and Dimitrios Sounas demonstrate a non-invasive, shadow-free, invisible sensor for airborne sound waves at audible frequencies, which fully absorbs the impinging signal, without at the same time perturbing its own measurement or creating a shadow.
