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Intel demos multi-wavelength laser array integrated on silicon wafer

Next stop – on-chip optical interconnects?

Intel is claiming a significant advancement in its photonics research with an eight-wavelength laser array that is integrated on a silicon wafer, marking another step on the road to on-chip optical interconnects.

This development from Intel Labs will enable the production of an optical source with the required performance for future high-volume applications, the chip giant claimed. These include co-packaged optics, where the optical components are combined in the same chip package as other components such as network switch silicon, and optical interconnects between processors.

According to Intel Labs, its demonstration laser array was built using the company's "300-millimetre silicon photonics manufacturing process," which is already used to make optical transceivers, paving the way for high-volume manufacturing in future. The eight-wavelength array uses distributed feedback (DFB) laser diodes, which apparently refers to the use of a periodically structured element or diffraction grating inside the laser to generate a single frequency output.

Intel claims that the array achieves output power and wavelength spacing uniformity that exceed typical industry specifications.

"Most importantly, this can be done using existing manufacturing and process controls in Intel's fabs, thereby ensuring a clear path to volume production of the next-generation co-packaged optics and optical compute interconnect at scale," Intel Labs senior principal engineer Haisheng Rong said in a statement.

According to the chip giant, integrating silicon circuitry and optics side by side on the same package holds the promise of future I/O interfaces with improved energy efficiency and longer reach.

However, while co-packaged optical solutions using dense wavelength division multiplexing (DWDM) technology have shown promise for increased bandwidth in a compact footprint, it has proven difficult to produce DWDM light sources with uniform wavelength spacing and power until now, Intel claims.

But Ayar Labs, another player in the photonics field, recently warned that one of the drawbacks of co-packaged optics is that if the optics fail, the entire chip becomes useless.

For the demonstration array, Intel used advanced lithography to define the waveguide gratings in silicon prior to the III-V wafer bonding process. This resulted in better wavelength uniformity compared to conventional semiconductor lasers, and the array also maintains its channel spacing in different ambient temperatures.

Intel said that technology from the eight-wavelength integrated laser array is being implemented by Intel's Silicon Photonics Products Division into a future optical compute interconnect chiplet product. This is expected to offer a power-efficient, multi-terabit-per-second interconnect between compute resources such as CPUs, GPUs and memory.

Earlier this month, Synopsys and Juniper Networks disclosed that they had jointly established a separate company, OpenLight, to accelerate the development of high-performance photonic integrated circuits. It expects reference designs for 400G and 800G transceivers with integrated lasers to be available this summer. ®

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