We present emission up to 3 THz from a phase-matched terahertz-optical photonic circuit, featuring a co-planar metallic cavity traversed by an optical rib waveguide and a dipolar antenna for efficient out-coupling of terahertz waves.

We discuss recent progress in miniaturizing terahertz devices, facilitated by integrated photonic circuits. We show these provide ways to engineer dispersion, achieve field enhancement and realise complex functionalities on a single chip.

Terahertz science and technology is possibly now at an inflection point where integrated photonic circuits become increasingly viable sources and detectors of such high-frequency radiation. Generation in both second order [1] and third order [2,3,4] nonlinear waveguides and architectures thereof has exploited either optical rectification or microcomb generation with subsequent optical-to-terahertz conversion at a uni-travelling carrier photodiode. These initial demonstrations showcase a possible route towards miniaturized terahertz chips that are seamlessly integrated with photonics.