Femtosecond laser 3D direct writing in glasses After extensive research on the interaction between femtosecond laser pulses and glass conducted by a Euro-Australian network, transparent material processing using ultrafast lasers may find new opportunities in industry. Digital Economy Industrial Technologies Fundamental Research © yuriz, Thinkstock Glass is a transparent material with properties that no other materials have. It has fascinating capabilities such as reflecting, transmitting and absorbing light. The interaction of ultra-short pulses of light less than a few hundred femtosecond (10-15 second) is such that the refractive index changes locally up to a few that are 10-2. By scanning the glass using a translation stage, refractive index changes can be used to form paths through which light can be guided in 3D from one place to another. With EU funds, the E-FLAG (Exchanges around femtosecond laser applications in glasses) network was set up to promote international 'brain circulation' between Australia and Europe regarding this promising direct writing technology. Researchers focused on characterising femtosecond laser-induced structural changes in silica-based glass achieved with far greater efficiency and flexibility than lithography and dry etching. In addition, E-FLAG aimed to create prototypes of 3D integrated optical devices, such as 3D waveguides, Bragg gratings and 2D space-variant birefringent optics with potential applications in the field of optical communications. The E-FLAG team accomplished significant breakthroughs. These included nanogratings' formation and ultrafast silica oxide decomposition in various glasses including pure silica but also TiO2-SiO2 glass, borosilicate and GeO2. Chiral optical properties and asymmetric light transmission were also observed in silica glass. Until its completion at the end of 2014, E-FLAG advanced the state of the art of femtosecond laser micro-patterning. Femtosecond laser glass processing is evolving at a fast pace, and the project results promise possibilities beyond the field of micro-machining. It is a technology that creates new markets for the laser industry in optical communications, laser as well as biomedical applications. Keywords Femtosecond laser, glass, E-FLAG, optical devices, optical communications
