Freestanding self-written polymer waveguides were fabricated between two single mode fibres by using free radical photopolymerization technique. Photo curing enables modification of the initial liquid monomer at the illuminated part of the photopolymerizable system to form a permanent solid polymer waveguide between the cores of the fibres. Three compound acrylate based monomer (PETA) and Norland optical adhesives (NOA) were used to fabricate polymer bridges. The two systems are cured by visible and UV respectively. The optical, mechanical and nonlinearity properties of freestanding self-written polymer waveguides were investigated. Polymer waveguides up to 600 µm long between two fibres were fabricated by unidirectional illumination. The optical power required for photopolymerization is sufficiently low that it is possible to use incoherent light source instead of laser, which also allows investigation of the optical transmission over a wide range of wavelengths from visible to NIR. Optical characterization showed that PETA waveguides have better optical transmission and insertion loss of about 1.2 dB was measured for the bridges up to 600 µm long at 1550nm. Some limitations prevented us to extend waveguide’s length beyond 600 µm, the bridges also showed poor adhesion quality particularly at the polymer/fibre interfaces which needed an action. In order to improve mechanical properties of polymer waveguides also to overcome bonding failure between fibre and polymer, the fibres were treated with adhesion promoter. The treatment together with bidirectional curing from both fibres improved mechanical and optical properties of the polymer waveguides. The insertion loss was reduced to 0.6 dB associated with bi-directionally cured 600 µm long waveguide.Nonlinear response of polymer waveguides was measured by coupling a high power ultra short pulse laser. Using bidirectional curing and inserting fibre ends into capillaries millimeter long waveguides with minimum loss of 1.1dB were fabricated. A long interaction length of polymer waveguide allows spectral broadening and self-phase modulation features to occur in response to the high power laser propagation through the polymer bridge. The spectral broadening in polymer waveguide was much broader than that of 1.5m plain fibre. The comparison of the results associated with maximum phase shift occurs in polymer with plain fibre revealed that the nonlinear coefficient of polymer material is about 1000 times larger than that of silica fibre.
|Date of Award||21 Sept 2017|
|Supervisor||William Wadsworth (Supervisor)|
- Self-written polymer waveguide
- Optical fibre