Terahertz phase modulation enabled by magnon and crystal-field driven dielectric dynamics relevant for next-generation secure communication

The increasing demand for high-volume data transfer has directed attention to the terahertz (THz) spectrum, owing to its capacity for a higher rate of data transfer and highly directional signal transmission. A key requirement for THz communication technologies is precise and dynamic control over the amplitude and phase of THz radiation. In this context, the presence of multiple quasiparticle excitations in the THz spectral range, together with versatile control knobs in emergent quantum materials, could offer promising technological opportunities. Engineering these excitations and their mutual interactions can induce dynamically tunable dielectric properties, enabling control of the phase of THz radiation. Here, we report the dielectric modulation of a complex magnet, HoCrO3, controlled by intrinsic crystal-field and spin excitations in the THz energy range of 0.5–8 meV, using magneto-THz spectroscopy. This modulation is synchronized with the temperature-induced frequency shift in these excitations, potentially affecting the response of THz phase—a feature relevant for communication devices. This approach to THz phase modulation using intrinsic material excitations is key to phase-based encryption and decryption, depicted by the proof-of-concept proposition, highlighting their potential in next-generation secure communication.