A compact 100 GHz femtojoule silicon-organic hybrid modulator based on a novel Mach–Zehnder interferometer design

In this paper, a high-speed, low-power and compact silicon-organic hybrid (SOH) modulator operating at the telecom wavelength is presented. The modulator is based on the mature and widespread silicon-on-insulator technology with a device layer of 220 nm. The proposed design utilizes a slot waveguide in a loop-terminated Mach–Zehnder interferometer (LT-MZI) configuration. The LT-MZI is twice as compact as the conventional MZI. Accordingly, the LT-MZI modulator exhibits a reduction in capacitance by a factor of two, which subsequently enhances the modulator speed and power consumption by a factor of two. An electro-optic polymer is used as it exhibits fast and strong electro-optic effects. Finite element and finite difference simulations show that for a driving voltage of only 0.5 V our modulator arms' length is as low as 167 µm resulting in a V_π × L product of only 0.084 V mm, 10.41 fF capacitance and up to 100 GHz speed with corresponding energy consumption of only 6.755 fJ bit⁻¹. Results based on 3D finite difference time domain simulation show that our modulator can work over a large optical bandwidth of 60 nm with an extinction ratio (ER) greater than 23 dB and insertion loss (IL) less than 1.7 dB, reaching ER = 40 dB and IL = 1.15 dB at λ = 1.55 µm. (paper)