Development of a new laser-surgery tool using high-brightness laser arrays and specially designed beam-shaping optics

The development of new medical tools for minimal-invasive surgery is essential for the reduction of pain, side-effects and hospitalisation costs. The benefits of using optical methods in some procedures are now well recognised. In this context semiconductor optical sources offer the advantages of high efficiency, compactness, low cost, long lifetime, low power consumption and high reliability. The optical source presented in this paper comprises a phase-locked, high-power laser diode array and beam shaping optics designed to optimise the coupling to small-diameter optical fibres. The high-power, index-guided laser array used in this work has been developed to achieve high-brightness by adopting a specially designed optical cavity based on the parabolic taper for each individual element in the array. With this design the individual elements are phase-coherent and the fundamental mode of the array is dominant, thus achieving quasi-diffraction-limited operation without the use of external lenses. Compared to other high-brightness laser arrays, the parabolic bow-tie laser array used here offers the advantages of simple device fabrication, reduced costs and compactness. In this work, specially designed lenses are used to circularise the beam and, therefore, to focus the beam to a small spot-size to improve coupling to single mode fibres. Details of the device characteristics, with emphasis on beam quality and phase front, and of the design of anamorphic optics for beam shaping and focusing will be presented in the context of the integration of the high-brightness laser array with the specially design optics to achieve optical power delivery exclusively where necessary via small-diameter optical fibres.