Abstract

The optical generation of millimetre-wave and microwave signals is a subject receiving much interest and may have applications in future radio distribution systems. Several optical generation techniques have already been investigated [1],[2],[3]. The generation of signals between 30 and 70GHz has been demonstrated using a DFB laser where the usual mode degeneracy was lifted and two modes were supported [1]. Modulation techniques have been used to produce narrow pulses with high harmonic content [2]. The generation of such beat signals has also been achieved over a range of frequencies up to -1THz using two single-moded edge emitting lasers [3]. Vertical-cavity surface-emitting lasers (VCSELs) arc attractive sources for such work due to their potentially lower cost compared with edge emitting devices. They are able to lase in a single longitudinal mode and their lasing wavelengths are readily tuneable by current and/or temperature. Since it is easy to integrate two devices on a single chip, a compact millimetre-wave source could be developed where current tuning of the beat frequency could be utilised. The generation of beat notes up to 20GHz wilh 3dB linewidths of 109MHz has already been achieved using a VCSEL array [4].

© 1996 IEEE