Femtosecond fiber laser direct writing of optical waveguide in glasses

There is a great deal of interests and efforts in the area of femtosecond (fs) laser direct writing of transparent materials, which shows promise to be a powerful and flexible technique for rapid fabrication of photonic micro-device, such as gratings, waveguides and optical amplifiers. Waveguide properties depend critically on the sample material properties and writing laser characteristics. In this paper, we present results on the micro-fabrication of waveguide and photonic micro-devices using fs fiber laser direct writing technique. Single line writing of different types of glasses with respect to the focused laser beam at different pulse energies and writing speeds has been investigated at first. Then the waveguide properties were characterized in terms of their shapes and transmission. It was found that specific consideration of the pulse energy, repetition rate and writing speed should be taken into account in order to fabricate low loss positive index guiding waveguide devices in a specific type of glass. Furthermore, a coupler-like guiding structure in glasses has also been demonstrated. The modified regions in both waveguides were checked by scan electron microscope (SEM) to reveal possible cracks and non-refractive structural defects. This technique can be used to produce micro photonic devices and applied to fabricate a single glass chip 3D photonic devices.