Yoshinori NAMIHIRA, Md. Anwar HOSSAIN, Taito KOGA, Md. Ashraful ISLAM¹, S. M. Abdur RAZZAK², Shubi F. KAIJAGE, Yuki HIRAKO, and Hiroki HIGA

Graduate School of Engineering and Science, University of the Ryukyus, Senbaru 1, Nishihara, Okinawa 903-0213, Japan ¹Sub Divisional Engineer, Public Works Department, PWD, Bangladesh Govt. Service, Bangladesh ²Department of Electrical and Electronic Engineering, Rajshahi University of Engineering and Technology, Rajshahi-6204, Bangladesh

(Received November 14, 2011; Accepted January 12, 2012)

In this paper, we propose a highly nonlinear dispersion flattened hexagonal photonic crystal fiber (HNDF-HPCF) with nonlinear coefficients as large as 57.5 W^-1 km^-1 at 1.31 μm wavelength for dental optical coherence tomography (OCT) applications. This HNDF-HPCF offers not only large nonlinear coefficient but also very flat dispersion slope and very low confinement losses. Using these characteristics of our proposed PCF, it is shown through simulations by using finite difference method with an anisotropic perfectly matched boundary layer that this PCF offers the efficient supercontinuum (SC) generation for dental OCT applications at 1.31 μm wavelength using a picosecond pulse easily produced by commercially available less expensive laser sources. Coherent length of light source using SC is found 10 μm and the spatial resolutions in the depth direction for dental applications of OCT are found about 6.1 μm for enamel and 6.5 μm for dentin.

Key words: photonic crystal fiber (PCF), chromatic dispersion (D), effective area (A_eff), optical coherence tomography (OCT), finite difference method (FDM), supercontinuum (SC), effective index (n_eff)