Finbar T. Sheehy

Wave-coupled LiNbO/sub 3/ electrooptic modulator for microwave and millimeter-wave modulation

A new technique of phase velocity matching in electrooptic modulators was demonstrated. The results show that the phase velocity mismatch due to material dispersion in traveling-wave LiNbO/sub 3/ optical waveguide modulators can be greatly reduced by breaking the modulation transmission line into short segments and connecting each segment to its own surface dipole antenna. The array of antennas is then illuminated by the modulation signal from below at the proper angle to produce a delay from antenna to antenna that matches the optical waveguides delay. A phase modulator 25 mm in length with five antennas and five transmission line segments was operated from 4.6 to 13 GHz with a maximum phase modulation sensitivity of over 100 degrees /W/sup 1/2/.<<ETX>>

60 GHz and 94 GHz antenna-coupled LiNbO/sub 3/ electrooptic modulators

Antenna-coupled LiBbO/sub 3/ electrooptic modulators can overcome the material dispersion which would otherwise prevent sensitive high-frequency operation. The authors previously demonstrated the concept with a phase modulator at X-band. They have extended this demonstration to a narrowband 60-GHz phase modulator and broadband amplitude modulator designs at 60 and 94 GHz, respectively.<<ETX>>

Velocity-matched electro-optic modulator

Partitioning the transmission line on a LiNbO3 traveling wave modulator into short sections and feeding each section from an antenna integrated to the modulator surface can overcome the frequency limitation from material dispersion. A phase modulator at 5-13 GHz with a peak sensitivity better than 100 deg/(Watt) sq rt is demonstrated using an unoptimized microwave feed system. The technique should be scalable to high millimeter-wave frequencies.

Antenna-coupled millimeter-wave electro-optic modulators for 20 to 100 GHz

Coupling the signal to the electrodes of an integrated electro-optical modulator with an array of antennas is used to velocity-match the modulation and optical waves, greatly extending-the length-to-modulation frequency product of the modulator. In addition, antenna coupling eliminates the parasitic elements associated with coax connectors, matching transformers and bond wires. This paper summarizes the results obtained to date with this technique at 20 to 100 GHz, with phase modulators, Mach-Zehnder modulators, and delta-beta directional coupler modulators.

Wave-coupled W-band LiNbO/sub 3/ Mach-Zehnder modulator

Summary form only given. Mach-Zehnder amplitude modulators have been designed for W-band operation (94 GHz), at a 1.3- mu m optical wavelength. These modulators use bow-tie antennas, which are relatively insensitive to DC bias connections made to the ends of the antenna elements. The bow-ties should also give a greater bandwidth than the dipole antennas.<<ETX>>

Antenna-coupled millimeter-wave LiNbO/sub 3/ electro-optic modulator

The phase-velocity mismatch due to material dispersion in traveling-wave LiNbO_3 optical waveguide modulators may be greatly reduced by breaking the modulation transmission line into short segments and connecting each segment to its own surface antenna. The array of antennas is then illuminated by the modulation signal at an angle which produces a delay from antenna to antenna to match the optical waveguides delay.

Novel Millimeter-wave Electro-optic Modulator

A waveguide LiNbO_3 electro-optic modulator has been demonstrated with a novel wave-coupling technique which greatly reduces phase-velocity mismatch. An 8-12 GHz version produces 48° phase modulation with 126 mW of drive power. A 60 GHz version is being built.