Self-phase modulation and spectral broadening in millimeter long self-written polymer waveguide integrated with single mode fibers

Polymer waveguide bridges up to 1.2 mm in length were optically written between two single-mode optical fibres. Optical Nonlinearity of polymer waveguide was measured by coupling a high power ultra-short pulsed laser. Before waveguide fabrication fiber ends were treated by adhesion promoter which covalently bond to both the silica fibre and the photopolymer, also photopolymerization was conducted from both fibres. The new techniques improve both the mechanical properties and optical transmission of polymer bridges. The optical insertion loss was 1.1 dB for the longest waveguides. A considerably 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 bridges. The spectral broadening in polymer waveguide was much broader than that of 1.5 m plain fibre. The ultrafast nonlinearity of the polymer waveguides was determined to be of the order of 103 times the nonlinearity of silica.