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technology  PICs


Increasing the versatility of photonic integrated circuits


Photonic integrated circuits enable the construction of compact, highly functional components, but operation tends to be restricted to telecom wavelengths. We are now addressing this shortcoming by developing devices that operate further into the infrared, say imec’s Dries Van Thourhout and Gunther Roelkens.


I


f you want to combine several functions on a single chip, you can build an integrated circuit (IC). In its electronic form this device is now incredibly mature, but the same cannot be said for its photonic counterpart. That’s partly because more than 95 percent of electronic ICs are made in silicon, while a vast and varied array of materials are employed for fabricating optical PICs, including III- Vs, polymers, glass and LiNbO3


. This diversity in materials has diminished the advantages that come 56 www.compoundsemiconductor.net March 2013


with scaling, and accounts for this class of ICs’ relatively low degree of integration and suboptimal performance.


These weaknesses have been known for many years, and since the 1990s several research groups have tried to address this by turning to silicon as a substrate for making these optical circuits. Its attributes include optically transparency in the telecommunications window (1300 nm and 1500 nm),


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