Laser manufacturing distal-end-optical-systems for endoscopic optical-biopsy diagnostics

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Oesophageal cancer has the fastest rate of increase of any cancer in the developed world and a poor prognosis with low survival after five years. Early identification of changes in oesophageal tissue leads to improved prognosis, but current techniques rely on traditional endoscopy and biopsy, which are invasive and exhibit poor sampling, and are only capable of identify issues that have already manifested through changes in the cellular structure. Recent developments in photonic-based technologies mean that it is now feasible to develop a medical diagnostic that is capable of identifying pre-cancerous (Barrett's syndrome), cancerous and non-cancerous tissues, by analysing the spectral properties of laser light inelastically scattered from tissue (Raman spectroscopy). By performing Raman spectroscopy at the end of a thin and flexible fibre-optic, that is used to precisely guide light into and out from the region of interest, it will be possible to test in-vivo whether oesophageal tissue is malignant or normal. This technique may also be able to pick up abnormalities that would not be picked up during histopathology, crucial information that could enable early diagnosis and mean that unnecessary invasive surgical procedures could be avoided. Such a technology would also find applications in the endoscopic treatment of Barrett's oesophagus and oesophageal cancer, enabling the clinician to assess the margins of the relevant tissue regions before and during resection.There is, however, a significant manufacturing issue that stands in the way of fully developing these new and exciting photonic-based clinical tools; in order to control the properties of the light leaving and entering the distal (in-vivo) end of the fibre-optic, it is necessary to use a distal-end-optical-system (DOS) of some form. This DOS can be as simple as a single lens, or a more complicated construction, requiring mirrors, spectral filters and lenses, as is the case in the optical-biopsy Raman-based instrument. Currently, manufacturing such DOS devices requires discrete micro-optic components to be aligned and bonded together. These techniques are labour intensive, time-consuming and expensive. In short, current DOS fabrication techniques are non-optimal and are not suitable to commercial manufacturing; a new and more flexible manufacturing technique is required.During this STFC-CLASP project, we will develop new DOS manufacturing processes using ultrafast laser based techniques. These processes use focused ultrashort laser pulses, each only a few hundred femtoseconds long, to locally and precisely modify the structure of a substrate material in three-dimensions. The laser-induced modification manifests itself in a variety of ways, examples of which include changes to the chemical etch-rate and/or refractive index of the modified material. Using these manifestations, it is possible to directly write optical components, such as diffraction gratings, into the substrate material, and by using a post-irradiation chemical-etch step we can sculpt precision micro-optics. The fact that "ultrafast laser inscription" enables micro-optic components, such as lenses, mirrors and optical waveguides to be combined onto a single substrate, using a single manufacturing process, makes it the ideal route to commercially manufacture precision DOS technologies.