Plasmonic approaches have emerged as a promising path to deal with highest data rates on smallest footprints while being energy efficient. Since the first demonstration of ferroelectric modulator in OFC 2017, ETHz and IBM have defined the state-of-the-art with numerous publications, and the ferroelectric technology is currently further exploited by LUMIPHASE. Starting from IBM’s initial demonstration, LUMIPHASE developed a fabrication process achieving for the first time homogeneous deposition of single-crystalline BTO layers on 200 mm substrates. In addition, non-volatile phase shifters have been realized on silicon photonics. No other technology today has achieved such functionality. Phase-change materials is the only material system where non-volatile switching on silicon photonics has been previously reported. However, the effect is based on changes of the imaginary part of the refractive index rather the real part, which causes absorption changes. Apart from the fabrication advancement related to BTO films, IBM developed, for the first time, a CMOS compatible method to fabricate ferroelectric hafnium oxide layers using flash annealing. With this method we significantly reduce the thermal budget needed to stabilize the orthorhombic crystalline phase in hafnium zirconium dioxide.
MICRAM and UdS have worked on a power MUX (PMUX) architecture, where the final MUX selector stage directly drives the load. As the ultrashort modulator can be considered as a lumped capacitance, no far end 50-Ω termination is required. So far the fastest Si-based (P)MUXs reach 140 Gb/s. One is designed by UdS having the highest output voltage swing of 1.2V at 50 Ohm. The other is designed by R. Clarke et al. showing about 0.3V output voltage swing. Recently the fastest MUX in InP DHBT technology reached 212 Gb/s at 0.24V. At 140 Gb/s this MUX shows 0.35V output voltage swing. Within plaCMOS MICRAM and UdS developed a BiCMOS PMUX operating at 200 Gb/s and showed a full link including a 1:4 DEMUX. This is the fastest circuit demonstrated for NRZ coding.
Ge detectors for communication are now offered on a variety of PIC platforms, however, typically with bandwidth in the range 30-50GHz. The state-of-the-art of waveguide integrated Ge-PDs in terms of responsivity and OE bandwidth is still set by IHP, with 0.9A/W and 60GHz, respectively. Supported by plaCMOS, IHP could significantly improve state-of-the-art of waveguide integrated Ge photodiodes, demonstrating devices up to 265 GHz. In view of the plasmonic modulator results in plaCMOS, a unique technological setting of realizing photonics for modulators and detectors with similar size (a few 10µm in length) on a fast BiCMOS platform is now becoming a possibility. Although integration was not fully demonstrated, integrated >200GHz TRx devices will become available in the next 1-2years
