Fig. 1: Modulation operating principle.
From: Fast amplitude modulation up to 1.5 GHz of mid-IR free-space beams at room-temperature
a Sketch of the modulator geometry: the active region is embedded in a metal–metal structure. By applying on it an external bias, the amplitude of the reflected beam is modulated. b Close-up of a single 1D ribbon of the device. p is the patch side, D the period. Two Schottky contacts permit the effective application of an external bias to the hetero- structure. The electric-field distribution (z-component) of the TM03 mode is also sketched. TM0i refers to the mode with i nodal lines in the y-direction. c Intuitive view of the modulator operating principle in an ideal configuration: with no applied bias the system is designed to be in strong coupling. Two polaritonic branches are visible in the reflectance spectrum, for a specific value of the patch side p. By applying a specific bias we can deplete an arbitrary number of quantum wells and bring the system in the weak-coupling regime: the bare cavity TM03 mode is visible on the reflectance spectrum. d Conduction band profile obtained by solving the Schrodinger–Poisson equation (NextNano++24) at room-temperature with increasing external bias. No bias (solid blue line), 1.84 V (orange solid line) and 5.52 V (green solid line).
