Fig. 5.5, (a) Measured optical retardation for nanogratings in different glasses dependent on the pulse duration (pulse energy of 400 nJ). (b)/(c) SEM images of nanogratings in ULE (pulse energy 200 nJ, pulse duration 120 fs) and Borofloat (pulse energy 400 nJ, pulse duration 400 fs); from []. The samples were gold coated before inspection in the SEM to prevent charge accumulation