Planar periodic structures fabricated in Er/Yb-codoped phosphate glass using multi-beam ultraviolet laser holography

Abstract

The inscription of a two-dimensional periodic lattice in the Schott IOG1 phosphate glass, by employing a laser assisted selective chemical etching method, is presented here. A two step patterning approach is employed, wherein damage is induced into the glass volume by exposure to intense laser radiation and subsequently, a chemical development in an alkali solution, selectively etches the exposed areas. A simple four beam interferometric setup is used for defining the two-dimensional periodic pattern on the sample surface. The exposures were performed by using the output of a high coherence 213nm, 150ps Nd:YAG laser; while the chemical developing was carried out in aqueous KOH solution. The periodic structures inscribed have periodicities of the order of 500nm and depth greater than 200nm. These Bragg reflectors are characterized by means of diffraction efficiency, and surface topology by employing atomic force and scanning electron microscopy. Issues related with the interferometric and wet etching processes are also presented and discussed.