Photonics and Optoelectronics (P&O) Volume 3, 2014 www.jpo‐journal.org doi: 10.14355/jpo.2014.03.006 51 Near Zero Ultra‐flat Dispersion PCF: Properties and Generation of Broadband Supercontinuum Partha Sona Maji 1 , Partha Roy Chaudhuri *2 Department of Physics & Meteorology, Indian Institute of Technology Kharagpur‐721 302 Kharagpur‐721 302, INDIA 1 parthamaji@phy.iitkgp.ernet.in; * 2 roycp@phy.iitkgp.ernet.in Received 4 November 2013; Revised 29 November 2013; Accepted 18 December 2013; Published April 2014 © 2014 Science and Engineering Publishing Company Abstract We present a new design study of ultra‐flat near zero dispersion PCF with selectively liquid infiltration with all uniform air‐holes in the cladding towards achieving broadband supercontinuum generation (SCG). With rigorous series study of the optimization process we could achieve near zero ultra‐flat dispersion as small as 0±0.41 ps/nm/km for broad wavelength range. The optimized near zero ultra‐flat dispersion PCF has been targeted for smooth and flat broadband spectrum supercontinuum generation (SCG) for near Infrared (IR) applications. Broadband SC generations corresponding to three different designs of ultra‐flat dispersion fiber have been carried out by using picoseconds pulse laser around the first zero dispersion wavelengths (ZDW). The numerical results show that FWHM of around 400 nm with less than a meter long fiber can be achieved with these fibers that cover most of the communication wavelength bands. The proposed design study will be applicable for applications in the field of tomography, Dense Wavelength Division Multiplexing (DWDM) system and spectroscopy applications etc. Keywords Microstructured Optical Fiber; Photonic Crystal Fiber; Ultra‐flat Dispersion; Supercontinuum Generation Introduction Photonic crystal fiber (PCFs) [Broeng et al, 1999; Russel et al, 2006], which enjoys some excellent properties like wide band single mode operation, great controllability over dispersion properties and higher nonlinearity, has been the target for various nonlinear applications like supercontinuum generation (SCG) [Dudley et al, 2006;], four‐wave mixing [Barh et al, 2013;] and parametric amplification [Chaudhari et al, 2012;] etc. The two key aspects for quality SC generation have been spectral width and flatness over broadband wavelength [Dudley et al, 2006;]. However, obtaining a relatively flat spectrum remains to be a challenge. To generate a flat broadened SC, high nonlinearity and flat chromatic dispersion are essential. This requirement can be met by optimizing the design of the fiber and the pumping condition. PCF can meet the demand for ultra‐flat dispersion in the communication wavelength by its unique novel properties of dispersion tailoring and higher nonlinearity. However, the dispersion slope of such PCFs cannot be tailored for wide wavelength range with air‐holes of the same diameter. Various complicated designs such as different core geometries [Hansen et al, 2003; Saitoh et al, 2006; Florous et al, 2006;] and multiple air‐hole diameter in different rings [Saitoh et al, 2006; Florous et al, 2006; Saitoh et al, 2004; Saitoh et al, 2003; Poletti et al, 2005; Wu et al, 2005;] have been studied to achieve ultra‐flattened dispersion values over wider wavelength bandwidths. However, the technology of realizing complicated structures or PCF having air‐holes of different diameters in microstructured cladding remains truly challenging. An alternative route of achieving similar performance is shown to be practicable by filling the air holes with liquid crystals [Zhang et al, 2005; Alkeskjold et al, 2006;] or by various liquids such as polymers [Eggleton et al, 2001;], water [Martelli et al, 2005;] and ethanol [Yiou et al, 2005;]. Tunable PCG effect and long‐period fiber grating has been successfully realized with liquid‐filled PCFs [Yu et al, 2009;]. In this work, we have successfully designed three ultra‐flat near zero dispersion PCF with dispersion value as small as 0±0.41 ps/nm/km with all equal air‐ hole diameters throughout the cladding that can be realized by standard fiber drawing technology. The air‐hole diameter found to be in the range of 0.52 μm to 0.64 μm which can be fabricated easily as PCF with similar air‐hole diameter has already been successfully realized [Reeves et al, 2002;]. The numerical studies