PhD project by Oyewole Benjamin Efunbajo

Name: Oyewole Benjamin Efunbajo
Project Title: High pulse energy supercontinuum for combined flourescence and MSOT
Biophotonic Imaging
Supervisor: Peter E. Andersen

Project Description:
The main objective of this project is to develop all-fiber, high pulse energy supercontinuum (SC) sources for multispectral photoacoustic (PA), fluorescence imaging, and optical coherence tomography (OCT). The SC source will be based on using pulse repetition rate tunable ytterbium-doped fiber amplifiers to pump photonic crystal fibers (PCFs). One main challenge is that PCFs with very small cores are required to generate a wide supercontinuum but the pulse energy that a PCF can deliver is limited by the area of its core. Thus, a special focus is put into refining new technologies developed at NKT Photonics to increase the energy of supercontinuum pulses to a level that enables optoacoustic imaging and fluorescence imaging.

SC is a spectrally broadened light source, formed from interaction of nonlinear processes, when an intense laser beam propagates in a nonlinear medium. Recently, the use of PCFs as nonlinear media, has proven to be an efficient method of SC generation. Supercontinua can be versatile sources for many imaging modalities due to being broadband, offering a wide selection of wavelength ranges that can be spectrally filtered to desired parameters.

High energy pulsed supercontinuum lasers make excellent sources for multispectral imaging, because, they can be spectrally filtered to provide a source which can then be tuned over the entire generated spectrum allowing probing of the response of tissue over the whole spectral range. Due to the intrinsic thermal diffusivity and propagation speed of sound in tissues, tunable light sources having long pulses with widths of few nanoseconds and in the repetition rate range of hertz to kilohertz range are generally desired for PA imaging in particular. However, for imaging modalities, such as OCT, lower pulse energy sources in the megahertz regime are required, thus the need for a tunable source. Data obtained from probing can be used to derive functional information from cells deep in tissue which in turn can lead to new diagnostic techniques.


Peter Eskil Andersen
Gruppeleder, Seniorforsker
DTU Sundhedsteknologi
22 45 45 57