Broadband light source based on highly nonlinear non-circular core photonic crystal fiber for medical applications

We present a highly nonlinear non-circular core photonic crystal fiber (HNL-NCPCF) with all normal group velocity dispersion (GVD) to design a supercontinuum (SC) light source for optical coherence tomography (OCT) system. Nonlinear coefficient γγ is increased as large as 66 W−1 km−1 at 1.31μm by reducing the effective mode area and core is made non-circular to increase birefringence by putting the square lattice of air-holes inside the silica host. About 85 nm 10 dB spectral bandwidths for 2.5 ps input optical pulse and 140 nm 10 dB spectral bandwidths for 1.0 ps input optical pulse have been observed using the same fiber length of 200 m and input optical power of 15 W. Coherent lengths of the generated supercontinuum light sources are found 8.91μm for 2.5 ps input optical pulse and 5.41μm for 1.0 ps input optical pulse. Therefore, the highest longitudinal resolution for dental OCT at 1.31μm is found about 3.28μm for tooth enamel.