By using electro-optic sampling technique, the electric field distribution on a resonant electrode for optical modulation was measured with a resolution in the micrometer range, while the range of measurement area was a few millimeters. The electric field on the asymmetric resonant electrode is enhanced by series and parallel resonance at the electrode. The resonance frequency was shifted by the presence of the electro-optic crystal, which was placed on the electrode for use in the sampling technique. We also showed that the measured electric field distribution at the edges of the electrode was different from the results numerically obtained by an equivalent circuit model.

LiNbO3 optical modulators for band-operation with a resonant modulating electrode are investigated in this paper. We propose an asymmetric resonant structure consisting of two arms of modulating electrodes, where one arm is open-ended and the other arm is short-ended. The voltage standingwave was enhanced by the resonance of the electrodes, so that effective optical modulation was achieved, while the length of the modulating electrode was much shorter than the conventional travelingwave-type electrodes. The optical response at 6.2 GHz of a resonant modulator designed by maximizing the normalized induced phase was 4.94 of the response at dc with a non-resonant modulator.

A novel optical modulation scheme is proposed for synthesizing a pair of dual-mode optical BPSK signals with an orthogonal phase relationship via a LiNbO3 Mach-Zehnder modulator (MZM) with dual RF signal inputs and a carrier suppression feature, which enables the generation of a crosstalk-free QPSK signal at the photodetection stage. With this method, one can compensate the drawback, that is bandwidth broadening, in our previously proposed method where a dual-mode optical QPSK signal is generated on the basis of narrow-angle modulated QPSK signal injection into a double-sideband suppressed carrier MZM device. We have carried out experiments for 60 GHz performance demonstration of this QPSK signal generation mechanism, and the results indicate the effectiveness of the present scheme.

We propose a simple and novel technique for mapping vector spatial fields using electro-optic (EO) sampling. Our technique utilizes a sandwich-like EO crystal in which a dielectric mirror is inserted into the EO crystal. Three-dimensional field measurements at several given heights above a two-dimensional RF resonant structure were successfully demonstrated. Field scanning at any height is possible if the sandwich-like EO crystal is appropriately constructed.