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When Greater Extinction Is a Good Thing

Earlier this year we got some comment from French research consortium Leti on the photonics research they were doing and where they saw it going.

More recently, they’ve announced that their HELIOS project was able to achieve the first-ever 40 Gb/s optical modulator having  an extinction ratio (more or less like the noise margin, the power difference between a logic 0 and a logic 1 – why optical needs a different vocabulary, I don’t know…) of 10 db.

This was done on a CMOS-friendly process for straightforward integration with other circuits.

I asked what was done differently to achieve this, and they were somewhat coy, noting a “well-mastered design.” More specifically, “To insure a precise doping profile [, which] is mandatory for silicon depletion modulators, the patented self-alignment technique gave a well defined junction. Then optimization of the doping and fabrication of thick electrodes helped to achieve this [result] as well as optimized design for the RF electrodes.” They’re promising higher RF speeds in the future.

I also asked whether this was a proof-of-concept project, or whether the result was transferrable to commercial use. They said they used standard processing techniques, getting good yields on 200-mm wafers, so that, whenever the market is ready, this can be moved into production.

More info on their release

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