ORC Seminar Series

Speaker: Weijia Yang

Date: Wednesday 29th October 2008

Time: 2pm

Venue: Building 46, Lecture Theatre B

Abstract:

Material processing with femtosecond lasers has recently attracted considerable interest due to a wide range of applications including laser surgery, integrated optics, optical data storage, 3D micro- and nano-structuring. Depending on the focusing position of the laser beam, surface patterning or bulk modification could be realized in transparent materials using focused femtosecond laser irradiation. In this talk, I will mainly discuss the later case where the laser beam is focused inside the bulk transparent material. Depending on the exposure parameters and material property, three qualitatively different kinds of structural changes can be induced inside transparent materials: an isotropic refractive index change that is mainly used for the waveguide inscription; a form birefringence with negative index change enabling the realization of retardation plates; and a void suitable for the application of data storage. Here, waveguide writing in high index bismuth borate glass, form birefringence induced in bulk fused silica by self-assembled sub-wavelength structures and voids created in glasses will be discussed. Moreover, both nonreciprocal photosensitivity that manifests itself as a dependence of the material modification on the light propagation direction in a non-centrosymmetric crystal and a quill writing effect revealing a strong dependence of the material modification in glass on the orientation of the writing direction relative to the direction of pulse front tilt will be revealed.