Electronic devices with low phase noise frequency generation

Clocking circuitry comprising:

• a first laser configured to generate a first optical local oscillator (LO) signal;
• a second laser configured to generate a second optical LO signal;
• a phase-locked loop (PLL) path coupled around the second laser and configured to lock a phase of the second optical LO signal to a phase of the first optical LO signal;
• and
• a self-injection locking loop path coupled around the second laser and configured to self-injection lock the second laser.

A method of operating wireless circuitry to transmit wireless signals, the method comprising:

• emitting, at a first laser, a first optical local oscillator (LO) signal at a first frequency;
• emitting, at a second laser, a second optical LO signal at a second frequency that is different from the first frequency;
• producing, at a first photodiode illuminated by the first optical LO signal and the second optical LO signal, an antenna current on an antenna resonating element, the antenna current having a third frequency given by a difference between the first frequency and the second frequency;
• generating, at a second photodiode, a beat signal based on the first optical LO signal and the second optical LO signal, the beat signal having the third frequency;
• generating, at a mixer, a self-injection locking signal based on the beat signal and the first optical LO signal;
• and
• self-injection locking the second laser based on the self-injection locking signal.