Create Photonic Reprogrammable circuits without Lithography
Photonics is now a vital part of international high-speed communications. Photonics for general processing is less common but still a subject of research. The possibility of creating circuits based solely on light is tantalizing. Unlike the majority of photonic circuits, which are made using patterns etched onto a semiconductor mask by lithography. A recent paper in Nature Photonics (Press release, ResearchGate), by [Tianwei Wa] and his colleagues at the University of Pennsylvania, focuses on this topic.
It is puzzling that, despite lofty claims that this was ‘the first’ time that an FPGA-like photonic device had been created, this was far from the truth, as e.g. A 2017 paper published by [Kaichen Do] and co-workers (full PDF article) in Advanced Materials. The researchers heated sections of vanadium oxide (VO2) using a laser. At 68 degrees Celsius, the material changes from an insulating phase to a metal phase. This method allows for the creation of a variety of photonic devices with mm-sized features.
The photonic system described by [Wu] and colleagues appears to be different. It uses a 2D method, using a slab InGaAsP onto which the laser pattern can be projected. Whether it is more versatile than other approaches remains to be seen, with the use of fully photonic processors in our computers still a long while off, never mind photonics-accelerated machine learning applications.
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