||Photonic crystal fiber based biosensors
||Carlsen, Anneline (Fibers & Nonlinear Optics, COM, Technical University of Denmark, DTU, DK-2800 Kgs. Lyngby, Denmark)
||Jensen, Jesper Bo Damm (Fibers & Nonlinear Optics, COM•DTU Department of Communications, Optics & Materials, Technical University of Denmark, DTU, DK-2800 Kgs. Lyngby, Denmark)
||Technical University of Denmark, DTU, DK-2800 Kgs. Lyngby, Denmark
||During my master project I have investigated some possible designs for using photonic crystal fibers (PCF) as biosensors during practical experiments and theoretical simulations. I have considered both labeled and non-labled biomolecules. A labeled biomolecule is a biomolecule attached to a florescent molecule. During this project I have filled fibers with aqueous solutions, using capillary forces, that contain labeled biomolocules, and measured the filled length, if possible. I have also examined light guiding properties in the fibers. However, the major subject of this thesis is the detection of labeled and non-labeled biomolecules which have been investigated using experiments and simulations.
Labeled biomolecules can be detected from their absorption spectra by recording the transmission spectrum and measure the absorption depths. Alternatively, the fluorescence spectra can be used. I have simulated the fraction of light propagating in the holes of four different types of PCF's containing either air or liquid finding that the fraction of light propagating in the holes is higher for liquid filled fibers and very dependent on the type of fiber. Additionally, the method has been tested experimentally for three different PCFs. The results are discussed with reference to the simulations. The main advantage of this method is the small sample volume needed for detection. Two differently labeld DNA (Deoxyribo Nucleid Acid) molecules can be detected simultaneously. The absolute concentrations of the biomolecules can not be detected, but at least for a particular hollow-core PCF guiding in the cladding, the relation between the concentrations can be determined qualitatively. The specific hollow-core PCF is useful for this type of biosensor. Non-labeled biomolecules have to change the optical properties of the fiber in order to be detected. I considered binding biomolecules to the inside walls of the holes in a coated PCF. This introduces a change in the effective refractive index which can be measured using a Bragg grating or a Lon Period Grating. This was investigated with computer simulations. The result of my simulations is that in a HNL firber (specific type of PCF with large relative radius) both a Bragg grating and a Long Period Grating introduce a shift in resonance wavelength that can be detected.
Creation date: 2006-06-22
Update date: 2007-02-24