  We demonstrate robust, high-speed random number generation using interference
of the steady-state emission of guaranteed random phases, obtained through
gain-switching a semiconductor laser diode. Steady-state emission tolerates
large temporal pulse misalignments and therefore significantly improves the
interference quality. Using an 8-bit digitizer followed by a finite-impulse
response unbiasing algorithm, we achieve random number generation rates of 8
and 20 Gb/s, for laser repetition rates of 1 and 2.5 GHz, respectively, with a
+/-20% tolerance in the interferometer differential delay. We also report a
generation rate of 80 Gb/s using partially phase-correlated short pulses. In
relation to the field of quantum key distribution, our results confirm the
gain-switched laser diode as a suitable light source, capable of providing
phase-randomized coherent pulses at a clock rate of up to 2.5 GHz.
