Single-drive high-speed lumped depletion-type modulators toward 10  fJ/bit energy consumption

Abstract

Reduction of modulator energy consumption to 10 fJ∕bit is essential for the sustainable development of communication systems. Lumped modulators might be a viable solution if instructed by a complete theory system. Here, we present a complete analytical electro-optic response theory, energy consumption analysis, and eye diagrams on absolute scales for lumped modulators. Consequently the speed limitation is understood and alleviated by single-drive configuration, and comprehensive knowledge into the energy dependence on structural parameters significantly reduces energy consumption. The results show that silicon modulation energy as low as 80.8 and 21.5 fJ∕bit can be achieved at 28 Gbd under 50 and 10 Ω impedance drivers, respectively. A 50 Gbd modulation is also shown to be possible. The analytical models can be extended to lumped modulators on other material platforms and offer a promising solution to the current challenges of modulation energy reduction.

A model for electro-optic response of slow-light silicon photonic modulators with lumped electrodes

“…As can be seen, |S21| is composed of two electrical and optical terms that impose restrictions on the EO bandwidth. While it is well-known that the electrical term shrinks the EO bandwidth (TRF-Circuit) because of its RC constant, the modulation speed can be also limited by the dynamic interaction time if the light is significantly slowed down [5,6]. Indeed, when it takes a long time for the light to pass through the waveguide, the optical term in Eq.…”

Modeling and trade-off analysis of a capacitive silicon Mach-Zehnder modulator for telecom applications

“…where N e is the electron and N h is the hole concentration. The effective index is found using the overlap integral [4]:…”

“…The EO bandwidth is calculated from the method described in [4] using the RF transmission coefficient (accounting the impedance mismatch) and the system transfer function. Figure 7 shows the RLC equivalent circuit model for the configuration proposed in this paper, where…”

“…magnitude higher than depletion modulators [3], decreasing the modulator length required. In this way, the modulator behaves as a lumped element which simplify its design [4].…”

Efficiency-Speed Tradeoff in Slow-Light Silicon Photonic Modulators

“…Conventional SiP modulators (such as MRMs and MZMs) are characterized by an efficiency-speed tradeoff: modulation efficiency is enhanced either by increasing p-n junction capacitance or photon lifetime at the cost of compromised EO bandwidth. In the case of SL-MZMs, because of their short phase shifter, they are typically implemented with lumped electrodes and their speed is restricted not only by the RC time constant but also by the interaction time between the optical signal and the uniform voltage along electrodes ( [22], [23]). This interaction time is increased by the low optical group velocity.…”