A technology is described for a Photonic Integrated Circuit (PIC) radio frequency (RF) oscillator. The PIC RF oscillator can comprise an optical gain media coupled to a first mirror and configured to be coupled to the PIC. The PIC can comprise a first optical cavity located within the PIC, a tunable mirror to form a first optical path between the first mirror in the gain media and the first tunable mirror, and a frequency tunable intra-cavity dual tone resonator positioned within the first optical cavity to constrain the first optical cavity having a common optical path to produce tow primary laser tones with a tunable frequency spacing. A photo detector is optically coupled to the PIC and configured to mix the two primary laser tones to form an RF output signal with a frequency selected by the tunable frequency spacing of the two primary tones.