title: Bandwidth enhancement of electro-optic field sensing using photonic down-mixing with harmonic sidebands.
abstract: We demonstrate that harmonic sidebands of an electro-optic modulator's driving frequency can be used as the local oscillator in a photonic down-mixing process in order to significantly enhance the bandwidth of near-field, electro-optic, microwave measurements. The creation of second- and third-order-harmonic modulation sidebands on a laser-diode output are described, with heterodyne down-conversion of microwave signals taking place within an electro-optic sensor crystal. The measurement bandwidth of an electro-optic microwave probe can thus be enhanced by as much as a factor of three with respect to the use of conventional, fundamental-harmonic sidebands. Carrier-sideband analysis from the measured optical spectrum indicates that millimeter-wave-frequency local-oscillator sidebands can be created using a Ku-band electro-optic modulator and that the electro-optic-signal-modulation depth can be enhanced by suppressing the light-beam carrier component. Transverse near-field distributions from high frequency patch antennas are extracted using both second- and third-order-harmonic sidebands.
authors.affiliation: Department of Electrical Engineering and Computer Science, Center for Ultrafast Optical Science, University of Michigan, Ann Arbor, Michigan 48109-2099, USA. dongjl@umich.edu
authors.forename: Dong-Joon
authors.initials: DJ
authors.lastname: Lee
authors.forename: John F
authors.initials: JF
authors.lastname: Whitaker
mesh_terms: D003198:Computer Simulation; D017076:Computer-Aided Design; D004574:Electromagnetic Fields; D004581:Electronics / Q000295:instrumentation*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D008872:Microwaves; D008962:Models, Theoretical; D055095:Optics and Photonics / Q000295:instrumentation*; D009991:Oscillometry / Q000295:instrumentation*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014159:Transducers