Fibre optical sources and systems for optical coherence tomography

• Main Author: Trifanov, Irina
• Published: University of Kent 2011
• Subjects: 616.07545
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.593914

Optical Coherence Tomography (OCT) is a powerful imaging technology in biomedical research and medicine. It enables in situ. 3D visualization of tissue structure and pathology, without the need. to excise the tissue and resolution approaching that of histology. OCT has had the most clinical impact in ophthalmology, where it provides structural and quantit ative informat ion that cannot be obtained by any other modality. The objective of the work presented in this thesis was the development of new imaging methods and optical devices to progress the OCT technology in t erms of its versatility, as well as to improve on parameters such as resolution, wavelength availability, integration effort and reliability. One of the most desired features in high resolution imaging is the display of simultaneously generated confocal images. The implementation of a confocal channel at the core of an OCT with quasi-simultaneous display of both images is demonstrated by synchronous optical switching of the power in the reference arm of the interferometer with the scanner determining the line in the final raster. The 1.0-1.1 11m region of the optical spectrum emerged as an attractive option compared to the standard 700-900 nm region, due to increased penetration beyond the retina, into the choroid, and reduced scat tering. Therefore, in this thesis, two novel optical sources based on fiber optic technology at 1 micrometer have been researched, assembled and tested: (a) a broadband ASE source based on combination of Yb-doped and Nd-doped silica fibers . The source emits at a cent ral wavelength of 1060 nm with a full-width-halfmaximum exceeding 70 nrn and 20 m\V output power; and (b) a swept fiber laser source emitting at 1065 nm central wavelength, with :::::l 50 nm tuning range and 40 m Woutput average power. A simple solution to linearize the sweeping in wavenumber (optical frequency), as required for image rendering, is demonstrated. The two prototype sources have been packaged and their performances validated in fully func tional OCT systems.