We propose and experimentally demonstrate a novel technique for optical generation of modulated millimeter-wave (mm-wave) by using a gain switched laser (GSL) that is externally injected with a modulated light source. The GSL generates a stream of optical pulses, and these pulses exhibit a small shift in the time domain when the GSL is injected with an on-off keyed (OOK) optical data signal. This time shift can produce a phase modulated mm-wave signal at 60 GHz by suitable optical filtering of the GSL laser output. The system performance was analyzed for data streams at 1.25 Gb/s by using bit-error-rate (BER) measurements for back-to-back (BTB) and 3-km fiber transmission. © 2011 IEEE.