Optical heterodyne techniques can be used to generate millimeter-wave signals. Optical FM sideband injection locking can be used to acheive an extremely narrow spectral width millimeter-wave signal. The phase and amplitude of the millimeter-wave signal can be controlled using electro-optic waveguide components. MICROWAVE AND MiLlIMETER-WAVE SIGNAL GENERATIONAn optical heterodyne technique can be used to generate electrical microwave signals from DC up to millimeter-wave frequencies. Two single-frequency laser diodes of the same wavelength are temperature and current tuned to lase at slightly different frequencies f and f2. Thetwo optical signals are combined and mixed at a high speed detector producing an electrical beat signal at a frequency of Li! Ii -f2. The spectral width of the generated signal is determined by the linewidths of the two free-running lasers, typically several tens of megahertz.In order to obtain a narrow spectral width signal, an optical FM sideband injection locking technique can beThe arrangement is illustrated in Figure (1). R/: i iput' &,8ye Lasers Elec/ro-optic sin(f /,) ph8se modul8/or E1 Figure (1) Using a very low phase noise microwave signal synthesizer, the master laser is FM-modulated by modulating the drive current to the master laser at a microwave frequency, producing several orders of FM sidebands in the optical frequency spectrum.2 The optical output of the master laser is injected into the two slave lasers, which are tuned by controlling both the drive currents and temperature to lock on to different FM sidebands of 250 Alas/er Zaser '0 117 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/23/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx

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Phased-locked semiconductor laser arrays have been a subject of great interest in recent years.(1-2) These laser arrays are very promising candidates as efficient high power monochromatic optical sources. The relative phases of the lasing elements of the array are locked to each other due to the effect of optical coupling between adjacent laser stripes, creating a stable far field radiation pattern. However, most of the phased array lasers reported previously showed double-lobe far-field patterns, which are undesirable for many applications.

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