Abstract
A novel electro-optic silicon-based modulator with a bandwidth of 78GHz, a drive voltage amplitude of 1V and a length of only 80 microm is proposed. Such record data allow 100Gbit/s transmission and can be achieved by exploiting a combination of several physical effects. First, we rely on the fast and strong nonlinearities of polymers infiltrated into silicon, rather than on the slower free-carrier effect in silicon. Second, we use a Mach-Zehnder interferometer with slotted slow-light waveguides for minimizing the modulator length, but nonetheless providing a long interaction time for modulation field and optical mode. Third, with this short modulator length we avoid bandwidth limitations by RC time constants. The slow-light waveguides are based on a photonic crystal. A polymer-filled narrow slot in the waveguide center forms the interaction region, where both the optical mode and the microwave modulation field are strongly confined to. The waveguides are designed to have a low optical group velocity and negligible dispersion over a 1THz bandwidth. With an adiabatic taper we significantly enhance the coupling to the slow light mode. The feasibility of broadband slow-light transmission and efficient taper coupling has been previously demonstrated by us with calculations and microwave model experiments, where fabrication-induced disorder of the photonic crystal was taken into account.
Highlights
Fast Mach-Zehnder silicon modulators with low operating voltage fabricated in CMOS technology have the potential to considerably cut costs for high-speed optical transceivers
Modulation at 165 GHz has been shown in a polymer ring resonator [2], for a signal bandwidth of a few GHz only
Poled polymers can have electro-optic coefficients ranging from moderate r 33 = 10 pm/ V [3] to extremely high values of r33 = 170 pm/ V [4], [5], enabling operation with low drive voltage
Summary
Fast Mach-Zehnder silicon modulators with low operating voltage fabricated in CMOS technology have the potential to considerably cut costs for high-speed optical transceivers. In this paper we propose an ultra-compact silicon-based Mach-Zehnder amplitude modulator with a 78 GHz modulation bandwidth and a drive voltage of 1 V, which allows data transmission at 100 Gbit/s. This is achieved by infiltrating an electro-optic polymer into a slotted photonic crystal waveguide, thereby making use of the fast electro-optic effects of polymers, the strong field confinement in slotted waveguides and the slow light interaction enhancements provided by the photonic crystal waveguide, where group velocity and dispersion may be controlled [12], [13].
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