A slow-wave resonant electrode design for optical modulators

Abstract

A slow-wave resonant electrode structure is proposed for the phase velocity matching between the RF wave and optical signal in III-V optical modulators. The resonant structure should result in reduced RF drive requirements for the modulator. For a planar structure, the proposed velocity-matched electrode configuration employs a coplanar waveguide (CPW) design, which consists of the usual center conductor segmented into a series of Z-shaped cascaded resonators. A similar electrode design may be used for III-V semiconductor ridge guides. With this design, the effective quality factor, Q, of the resonant structure will result in a decrease of the drive voltage. Thus, the power requirement can be reduced by a factor of Q/sup 2/ for a bandwidth of 10%. In addition, the bandwidth design can be improved by using Chebyshev design for coupled-line filters. Experimental results are discussed. The results indicate that, for the GaAs-AlGaAs optical waveguide, the optical phase velocity is 2.65/3.61 times smaller than RF phase velocity. With the proposed electrode design the RF phase velocity can be reduced by simply adjusting the resonator spacing. >