Semiconductor IQ modulator

A semiconductor IQ modulator including at least two or more Mach-Zehnder (MZ) modulators configured with differential transmission lines coupled by two signal lines for transmitting radio frequency (RF) modulation signals comprising differential signals, wherein

• each differential transmission line has an SS line configuration, the SS line configuration consists of a straight lead-out line, a phase modulation unit, and a termination resistor,
• each phase modulation unit includes the differential transmission line having a differential capacitively loaded traveling-wave electrode (CL-TWE) structure as a phase modulation electrode,
• the phase modulation electrodes of each phase modulation unit between adjacent channels are spaced apart by at least 400 μm or more, a distance between main signal lines of the differential CL-TWE structures is 60 μm or less,
• a plurality of DC phase adjustment electrodes for adjusting an operating point of each of the at least two or more MZ modulators and a PAD for the plurality of DC phase adjustment electrodes are provided between each phase modulation unit on an I channel side and each phase modulation unit on a Q channel side,
• a DC phase adjustment electrode of the plurality of DC phase adjustment electrodes is spaced apart from the phase modulation electrode of each phase modulation unit by at least 80 μm or more, and near-end and far-end crosstalk characteristics of a differential signal between adjacent channels are −30 dB or less in a required frequency bandwidth.