A single pulse laser beam of linear polarization is irradiated to a glass region such that the condensing point is located inside of the glass region, thereby to form, at the condensing point, a periodic structure region in which high refractive-index zones and low refractive-index zones are repeatedly...http://www.google.co.uk/patents/US7310463?utm_source=gb-gplus-sharePatent US7310463 - Optical structural body, its manufacturing method and optical element
