A simple optical to mm-wave conversion device is reported. It is based upon a GaInAs/AlInAs superlattice designed to produce mm-wave generation through the miniband negative conductance. It is driven by a light signal modulated near the oscillator fundamental frequency in order to obtain optical injection locking. The present paper stresses different material and non-linear transport properties necessary to optimise such devices at optical communications wavelengths. (C) 1998 Published by Elsevier Science B.V. All rights reserved.