Wafer Processing Yields High Q Microcavities

Microcavities require atomically smooth surfaces to obtain ultrahigh Q factors, but until recently such surfaces have been demonstrated only in structures such as droplets or microspheres. Researchers at California Institute of Technology in Pasadena have found a way to obtain ultrahigh Q using wafer-scale processing.

As described in the Feb. 27 issue of Nature, they first created support pillars using photolithography, pattern transfer into the silicon dioxide and selective dry etching of the exposed silicon. They then heated the silicon dioxide to reflow it and forced the molten disc into a toroid-shaped microcavity with an atomically smooth surface and a Q of greater than 100 million.