  Terahertz (THz) radiation, spanning from 0.3 to 3x10^12 Hz, fills the crucial
gap between the microwave and infrared spectral range. THz technology has found
applications in various fields, from imaging and sensing to telecommunication
and biosensing. However, the full potential of these applications is often
hindered by the need for precise control and manipulation of the frequency and
polarization state, which typically requires external THz modulators. Here, we
demonstrate a hybrid THz source that overcomes this limitation. Our device
consists of two THz emitters integrated into one single device, enabling pulse
shaping and chirality control of the emitted radiation without additional
external components. The two sources are a spintronic emitter and a
semiconductor photoconductive antenna (PCA). Using a combination of
dual-wavelength excitation, allowing for control of the relative time delay
between the two laser excitation pulses, and tuning external parameters for
each emitter (i.e., biasing voltage for the PCA and magnetic field for the
spintronic THz emitter) enables precise control of the mixing of the two
signals and results in frequency, polarization, and chirality control of the
overall THz radiation. This on-chip hybrid emitter provides an essential
platform for engineered THz radiation with wide-ranging potential applications.
