Subharmonic Temporal Response and Spontaneous Breaking of Discrete Time Symmetry in Plasmonic Distributed Feedback Laser

Abstract

Distributed feedback (DFB) lasers exploiting plasmonic structures as cavities are basic elements for various applications from sensorics to optoelectronics. Herein, the time response of a plasmonic DFB laser in the small‐signal modulation regime is studied. It is shown that the temporal period of the plasmonic DFB laser response can be equal to an integral multiple of the period of the pumping modulation, i.e., the temporal response can be subharmonic. This behavior of systems with time‐dependent parameters is a manifestation of spontaneous breaking of the discrete time symmetry. The appearance of subharmonic frequencies in the plasmonic DFB laser response is a consequence of synchronization of the beat frequency of the modes of plasmonic structures. Synchronization occurs when this beat frequency is nearly equal to the modulation frequency divided by an integer. It is shown that the ratio of the response period to the pump modulation period is determined by the size of the pumped region in the active medium, and the modulation frequency for the plasmonic DFB laser in the small‐signal modulation regime can reach several terahertz. These facts pave the way for the creation of tunable optoelectronic devices with a controlled temporal response.