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Three-dimensional optical circuits buried deep within a microchip are the
logical next step for microchip makers. The challenge is to connect deeply
buried layers of components, and keep them cool. The University of Nebraska’s
answer (WO 01/15819) is to burrow through a chip with ultra-short laser pulses.
A titanium sapphire laser emits a thousand pulses of infrared light per second,
with each pulse only lasting 150 femtoseconds. The pulses burn a channel just 10
nanometres wide. By turning the chip and laser, the researchers are able to
build a 3D pattern of paths which can carry light signals or coolant gas.