Abstract:
Etaphase is a fabless design company commercializing a next-generation “Semiconductor of Light” that provides large, complete, and isotropic band gaps for light, heat, sound, and other forms of wave energy. As the physical properties of these structures are controllable by design, they form a new class of “designer dielectric” or metamaterial. For a beachhead application in silicon photonics, Etaphase is designing, fabricating, and testing next-generation passive and active silicon photonic components of critical importance to continued scaling of cloud computing business models: the compact, energy-efficient, and very high data rate wavelength-division-multiplexed (WDM) photonic integrated circuits (PICs) that currently connect servers in datacenters and that are moving closer and closer to the microprocessors inside these servers. The structures are designed for fabrication using all the same layout and fabrication tools that are used to make computer chips. Passive components fabricated include waveguides, resonant filters, splitters, and combiners. Electrical energies lower than fJ/bit have been predicted for resonant optical modulator designs targeting the use of on-off-keying (OOK) to electrically impose data on an optical signal. These “attojoule class” modulators each designed to work at a separate optical wavelength, can be tightly integrated together to achieve a very high density of wavelengths on each chip, fabricated via the massively parallel fabrication techniques provided by semiconductor foundries (several of which are focusing now on silicon photonics), and tested using wafer-scale testing protocols originally developed in the semiconductor industry. The $3B optical interconnect market includes a rapidly-growing family of high-density optical transceivers priced for datacenter applications operating at rates of 400 Gb/s and beyond. HUDS-based PBG PICs promise to provide lower cost, more compact, and more energy-efficient solutions for how best to solve the bandwidth bottlenecks which are increasingly facing the high-performance computing and warehouse scale data center markets.
The structures can be designed and fabricated in wide-ranging size scales and materials to engineer the flow not just of light, but also of heat, sound, and other waves having frequencies from the rf to visible and perhaps even shorter wavelengths. At microwave frequencies, the structures can be made either with commercial 3d printers, or with 2d lithographic techniques.
Etaphase’s plan to commercialize HUDS-enabled PBG PICs disrupts the current trend toward silicon photonics microring resonators because HUDS-enabled PBG resonant structures are ~10x smaller in diameter than micro-ring resonators. The smaller volume of the HUDS-enabled PBG PICs relative to microring resonators has been shown to enable lower energy per bit modulation. The smaller size of PBG PICs is expected to reduce the costs of their temperature stabilization, particularly when combined with the increased design flexibility afforded by HUDS relative to microring resonators.
These advantages of HUDS-enabled PBG PICs, along with the improved fabrication tolerance, layout flexibility, and isotropy of HUDS, will provide a compelling case to one or more of the candidate strategic partners with whom we’ve initiated early discussions in the optical component, sub-system, transceiver, electronic-driver, networking-equipment, and warehouse-scale-computing markets.