Design, Operation and BER Test of Multi-Gb/s Radiation-Hard Drivers in 65 nm Technology for Silicon Photonics Optical Modulators

The paper presents the design and the performance characterization, through system-level bit error rate (BER) tests, of a driver for silicon photonics Mach-Zehnder modulator (MZM) devices. Fabricated in TSMC 65 nm technology, the driver exploits a differential topology and a multi-stage current-mode logic architecture. It is designed to withstand radiation levels in compliance with the requirements for the on-detector systems in future particle physics experiments. The driver has been tested up to 800 Mrad showing about 30% degradation in voltage ratings. The BER test made on the stand-alone driver shows a capability of handling 5 Gb/s bit-rates with a quasi-error free BER of 10. Electro-optical system-level BER tests carried out with an MZM wire-bonded to the designed driver showed an unexpected degradation in speed performances, which has been mainly attributed to packaging issues. Optimization and re-design activities, still working with 65 nm technology, are currently on-going to meet a data rate of 10 Gb/s for the same radiation hardness.