Electro-Absorptive Quantum Dot Antenna Resolves Terahertz Lightwaves via Biased Stark Effect

Semiconductor quantum dots offer highly flexible optoelectronic properties, rendering them attractive for a growing number of applications, including single-photon emitters, fluorescence microscopy, and display technology. Here, we report the realization of an electro-absorptive terahertz (THz) antenna based on colloidal semiconductor nanocrystals for the phase-resolved detection of infrared lightwaves. Introducing AC-biasing to symmetric nanocrystals, we break the symmetric response of the quantum-confined Stark effect (QCSE) to the direction of the THz field and obtain a polarity-sensitive observable. In particular, we analyze the nonlinear scaling of the QCSE and demonstrate that differential detection via bias-modulation yields a signal that linearly depends on the THz field strength. This THz antenna employs solution-processed quantum dots and enables an all-optical readout via absorption or emission, offering highly flexible implementations of THz sensing in the time domain.