Figure 1

DIC images of waveguide end-faces written at 1,000Â mm/min feed rate and energies of (a) 60Â nJ, (b) 70Â nJ, (c) 90Â nJ, (d) 130Â nJ and in the bottom row with an energy of 90Â nJ at feed rates of (e) 4,000Â mm/min, (f) 500Â mm/min, (g) 200Â mm/min and (h) 100Â mm/min, respectively. The writing laser was incident from the top of the images.