All-optical control of terahertz pulses is essential
for the development
of optoelectronic devices for next-generation quantum technologies.
Despite substantial research in THz generation methods, polarization
control remains difficult. Here, we demonstrate that by exploiting
band structure topology, both helicity-dependent and helicity-independent
THz emission can be generated from nanowires of the topological Dirac
semimetal Cd3As2. We show that narrowband THz
pulses can be generated at oblique incidence by driving the system
with optical (1.55 eV) pulses with circular polarization. Varying
the incident angle also provides control of the peak emission frequency,
with peak frequencies spanning 0.21–1.40 THz as the angle is
tuned from 15 to 45°. We therefore present Cd3As2nanowires as a promising novel material platform for controllable
terahertz emission.