Open Resonator Modes in Electron Cavity

Cavity resonators provide a cornerstone of wave confinement and manipulation. In particular, the photonic Fabry-Perot resonator has proven itself to be of both practical and fundamental importance. A distinguishing aspect of the Fabry-Perot resonator is its openness; its resonance occurs chiefly in the longitudinal direction, i.e. the cavity axis, whereas confinement in the transverse direction is provided solely by the curvature of the cavity mirrors. Although such cavity resonators can be generalized to all kinds of waves, few implementations have been demonstrated for material waves, and their resonance modes have yet to be understood. Here, we present the Fabry-Perot resonator for two-dimensional electronic waves, realized in a GaAs/AlGaAs heterostructure device. The electron cavity formed robust longitudinal modes despite being highly open to the background reservoir, and the transverse modes were separable by introducing an asymmetric perturbation to the cavity. In the asymmetric configuration, magnetoconductance measurements suggested the coexistence of modes centered and lopsided in the transverse direction, an observation supported by numerical simulation. Having identified the feasibility of an electronic resonator using highly open cavities, we further discuss its potential applications and a few subtleties arising in matter wave optics.