Fig. 2: Design and characterization of the Si-SLM chip.
From: Exploring 400 Gbps/λ and beyond with AI-accelerated silicon photonic slow-light technology
a Optical micrograph of the Si-SLM chip. An 8-channel Si-SLM array was fabricated on a 200-mm silicon-on-insulator (SOI) wafer, and the actual modulation area occupies only 4 mm × 0.5 mm, with the pitch of 500 μm between neighboring devices. b Device morphology of the fabricated Si-SLM. The modulator is under a Mach-Zehnder interferometer (MZI) structure, with the compact modulation arm of only 249 μm. A dual-drive architecture of GSGSG-type radio frequency (RF) electrodes is adopted, which enables the modulator to operate under the push-pull driving mode to enlarge the phase change. The scanning electron microscope (SEM) image of the fabricated slow-light waveguide is shown as the inset below. The waveguides are fabricated under a standard silicon photonic process and all feature sizes are suitable for the commercial silicon photonic foundry. c Measured electro-optic (EO) response under different bias voltages. The S21 response demonstrates that the modulator has an EO bandwidth of 90 GHz under the bias voltage of 3 V. The S11 response is maintained below –10 dB, indicating that the reflection of the modulator is weak. d Modulation efficiency under different wavelengths. An averaged enhanced modulation efficiency of 0.82 V⋅cm is obtained due to the introduction of slow-light structure. e Linearity of the Si-SLM. The measured third-order intermodulation spurious free dynamic range (IMD3 SFDR) is 91.82 dB ⋅ Hz2/3, mainly due to the nonlinear limitation of the plasma dispersion effect in silicon materials. f Crosstalk of parallel Si-SLMs. The measured crosstalk is around 30 dB at 60 GHz and 20 dB at 90 GHz. Due to the ultra-short RF links, the crosstalk of the Si-SLM array is at a low level and the impact on parallel signal transmission is small. g Passbands of the 8-channel Si-SLM array. The modulator possesses a flat passband of 7 nm around 1550 nm, and the passbands are basically consistent between different devices. For wavelength-division-multiplexed (WDM) system, the specific wavelengths of 8-channels are from 1548 nm to 1555 nm, with the spacing of 1 nm.
