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Spectral Selection
Researcher: Robyn Felix
Supervisor: George Dobre
Project Funding: DTA
Project Outline
Robyn is concentrating on using a combination of Czerny-Turner-type and prism-type spectrometer platforms to achieve spectral selection while keeping the overall power level constant and ensuring spectral stability.Spectral selection of narrower windows from a broadband output is important for OCT measurements on platforms with fibre systems. Spectroscopic OCT incorporates measurements of the wavelength dependent response with conventional OCT techniques. Tissues absorb differing quantities of light at certain wavelengths; by studying the amount of absorption at different wavelengths it is possible to define the composition of structures within the sample.
The axial resolution an OCT system is key to its design, defining the minimum distance between two points in depth for them to be distinguishable. However, other factors must be considered; the shape of the spectrum can also have a significantly effect on the achievable axial resolution. Spectral resolution also depends on the FWHM of the input light beam. However, for greatest spectral resolution (i.e. information specific to a particular wavelength) the narrowest possible range of wavelengths is required. This presents a challenge, that of finding a reasonable compromise between spectral and axial resolution.
Using a grating or prism-spectrometer architecture light from the 450 nm - 1700 nm broadband can be split into multiple Gaussian signals with different central wavelengths and comparatively narrower FWHMs. This helps achieve a high spectral resolution and fit around limitations imposed by the optical components used. Some of the study carried out so far involves the analysis of spectra at different wavelengths and the changes undergone in the process of propagation through the interferometric OCT platform. Spectral shaping of the resulting output into profiles close to a Gaussian shape are also being investigated.
