Purcell effect for cyclotron resonance in a two-dimensional electron system

We have investigated cyclotron resonance (CR) in a disk-shaped two-dimensional electron system (2DES) with different environments. We find that the metallic reflector at the back side of the semiconductor substrate leads to significant oscillations in the CR radiative decay rate with frequency. We prove that the discovered effect stems from the modulation of the electric field and photonic density of states at the location of the 2DES. Thus, we observe the Purcell effect for the cyclotron magnetoplasma mode. Our experimental results open a disruptive approach toward boosting the terahertz emission in solid-state devices.