Fibre-end micro-lens system for endoscopic erbium-laser surgery applications

A sapphire micro-lens system in combination with a zirconium-fluoride (ZrF₄) fibre has been designed and constructed as a surgical tool for focusing Er:YAG-laser radiation. It both refocuses the laser radiation transmitted through a 350 µm core fibre to a spot diameter of 570 µm at a working distance of 7.6 mm, and protects the distal fibre end from damage. An accurate and uncomplicated visualization of the focus position of the erbium-laser beam is realized by coupling a HeNe aiming laser into the cladding of the fibre. In vitro cutting experiments reveal the high cutting precision with minimal thermal damage of the surrounding tissue and the high damage resistance of the system. It may render the use of the erbium laser possible in a wide range of endoscopic applications.