Ultra high-speed segmented traveling-wave electroabsorption modulators

Analysis of Segmented Traveling-Wave Optical Modulators

“…If we use a transmission line built on top of InP to load this capacitance ( 0.9 pF cm), it will require an 5-mm-long electrode, and the optical waveguide will be too long and too lossy. On the other hand, if we build a transmission line with faster microwave phase velocity, for example, a microstrip line with low-dielectric material [19], the loading capacitance can be improved by a factor of two, and the electrode length can be halved.…”

“…Practically, achievable high impedance is 80 . To match impedance using this practical microstrip line, one has to either lower the target impedance to 33 or use a meandered microstrip line to match with a of 50 [19]. The latter approach is equivalent to making the microwave travel slower so that the value is higher.…”

“…However, for analog applications, wider bandwidth and higher modulation efficiency may be required. In this case, the traveling-wave electrode can be used to improve the performance [3]- [6], [19]. The microwave transmission lines for most of the previously demonstrated traveling-wave EAMs (TWEAM) were built directly on top of the optical waveguides, and they generally had a low microwave impedance (20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30), slow microwave velocity, and large microwave loss.…”

“…With the segmented traveling-wave design for EAMs [19], it is possible to achieve better performance. In the exemplary designs, we assume the total active modulation length is 300 m. It is divided into six segments and loaded to a microstrip transmission line same as the one in the last section.…”

“…In addition, previous research mainly focused on bulk GaAs MZMs. This paper applies the segmented traveling-wave design also for the quantum-well-based InP MZMs and EAMs and analyzes the use of meandered transmission line [19] in these devices. The previously published experimental result of a GaAs MZM will be used to verify this modeling approach.…”