Imec Extends Silicon Photonics Portfolio

This week, at the 45th European Conference on Optical
Communication (ECOC), imec, a world-leading research and innovation hub in
nanoelectronics and digital technologies, together with IDLab and the Photonics
Research Group, both imec research labs at Ghent University, are presenting key
milestone results in silicon photonics (SiPho) technology development. The
demonstrated building blocks help pave the way for 400Gb/s and beyond optical
links as well as for co-packaged optics in next-generation datacenter switches
- key enablers for data transmission in future data centers. Highlights include
a TSV-assisted, high-density (Tbps/mm2) CMOS-SiPho transceiver prototype, a
low-power 106Gb/s PAM-4 SiPho transmitter, a high-speed Ge/Si avalanche
photodetector, and ultra-broadband low-loss single-mode fiber couplers.

The exponential growth of the Internet and its associated
applications has pushed datacenters to deploy optical interconnects with
continuously increasing performance, and ever smaller power consumption and
footprint. In the next few years, data center optical links will be upgraded to
400Gb/s capacity, by aggregating four 100Gb/s PAM-4 lanes per link. As a
consequence, the aggregate bandwidth to be handled by a single datacenter
switch will increase to 51.2Tb/s, requiring ultra-high-density SiPho
transceiver technology, tightly integrated and co-packaged with the switch CMOS
chip.

To help industry meeting these challenging scaling
requirements, imec and its research labs at Ghent University are developing the
key technology building blocks, by leveraging imec's Si Photonics Platforms on
200mm and 300mm wafers, in combination with high-speed electronics.

Joris Van Campenhout, Program Director Optical I/O at imec
commented: “Our R&D programs have delivered substantial improvements at
various levels of Si Photonics technology, both at the level of process
integration, individual component development as well as at the sub-assembly
level. We are thrilled to share our progress with industry and academia at the
ECOC conference. We look forward to continue helping the communications industry
in Europe and beyond to address the key challenges in developing
next-generation optical interconnect technology.”

One of the highlights that imec presents at ECOC is the
first through-silicon-via (TSV) assisted hybrid FinFET CMOS/Si-photonics
transceiver technology. Operating at a data rate of 40Gb/s non-return-to-zero
(NRZ, single lane), this prototype combines ultra-low power consumption with
impressive (1Tbps/mm2) bandwidth density, paving the way to ultra-dense
co-packaged optics in future datacenter switches.

Imec and Ghent University are also presenting a 106Gb/s
transmitter that uses PAM-4 as a modulation format. This 4-level modulation
format has recently been adopted by industry as the modulation format of choice
for 53GBd single-lane transmission over 500m. Compared to other PAM-4
transmitters, imec's solution does not use any equalization or digital signal
processing and integrates two parallel GeSi electro-absorption modulators. This
results in an extremely compact and low-power (1.5pJ/b) transmitter able to
transmit data over 1km single-mode fiber at 106Gb/s.

Also, imec demonstrates improved edge coupler designs, based
on a hybrid Si/SiN photonic platform. Innovations to the layer stack resulted
in better than -1.5dB/fiber coupling efficiency to industry-standard single
mode fibers for operation in the O- and C-band. On the receive side, a
high-speed Ge/Si avalanche photodetector is presented with a multiplication
gain of 8 and 32GHz bandwidth. These avalanche photodetectors show great potential
for improving receiver sensitivities and optical link margins at data rates of
40Gb/s and beyond.