Skip to main content

Frontiers of Integrated Silicon Nanophotonics in Telecommunications

Final Report Summary - FISNT (Frontiers of Integrated Silicon Nanophotonics in Telecommunications)

The ERC funded project “Frontiers of Integrated Silicon Nanophotonics in Telecommunications” has focused on some of the key challenges for reducing the manufacturing cost, operational expenditures, and thus also the availability of optical transceivers. Interconnects are estimated to make up for about a quarter of today’s data center energy intake, so that reducing their power consumption is a key challenge for a sustainable IT infrastructure.

Silicon photonics is a promising technology for low cost, high-speed optical transceivers. It allows the fabrication of optical devices and subsystems on Silicon chips, with the same fabrication technology and infrastructure also used for CMOS electronics manufacturing. The technology is scalable to very high data rates and channel counts and may thus gain in importance as the amount of data processed in data centers further increases. While manufacturing of the chips themselves can be extremely cost effective, attaching the glass fibers and the laser providing the light makes up for a much higher portion of the production cost, so that it is essential to reduce the optical assembly cost in order to fully leverage the potential of the technology.

One outcome of the project are novel chip-to-laser and chip-to-fiber interfaces that allow relaxing the precision with which fibers and lasers need to be mounted onto the chips by a factor 3, putting the required assembly precision in reach of fully automated, high-throughput pick-and-place assembly stations that require minimal human intervention and are mass-manufacturing compatible.

A common approach to reduce the power consumption of electro-optic modulators, the devices that transduce electrical signals into optical signals, is to use resonant modulators – devices that use optical storage elements to boost optical intensities in regions where the light interacts with the electrical domain in order to improve the efficiency of the transducing mechanism. Unfortunately, resonant enhancement also comes with some severe limitations: The mechanism only works for a narrow range of targeted wavelengths, so that other building blocks such as lasers, optical filters or multiplexers need to be precisely designed and fabricated to fit to the exact same wavelength range. Since manufacturing variations and environmental conditions such as temperature swings both contribute to voiding this matching, practical utilization of these devices is difficult and has so far not found its way into industrial practice. We have developed a modified resonantly enhanced device topology that maintains a 20X power consumption enhancement compared to conventional non-resonant devices (so-called travelling wave modulators) while at the same time maintaining proper operation at a targeted wavelength even in presence of substantial environmental changes or manufacturing imprecisions (modulation is maintained in a larger than 50C temperature range).

Both key innovations rely on novel integrated photonic devices manipulating light at the chip-scale in photonic integrated circuits.