Fast heterodyne optical phase-lock loop using double quantum well laser diodes

The first experimental demonstration is reported of a heterodyne optical phase-lock loop (OPLL) using semiconductor lasers without external cavities or other linewidth narrowing methods. For a total loop propagation delay of 3 ns and a loop filter bandwidth of 700 MHz, a phase error variance of 1.02 rad² was achieved in 500 MHz measurement bandwidth.