Design and characteristic analysis of square air hole structure photonic crystal fiber

Fiber technology has attracted a considerable amount of attention in scientific research and industry. However, the inflexibility of design of traditional fiber leads to an existing developmental limitation. Photonic crystal fiber (PCF) is a new class of optical fiber based on the properties of photonic crystals and conventional fibers. Due to the highly structured cross arrangement and different background material refractive index, a variety of peculiar properties can be achieved by changing the size and arrangement of air holes and filling some materials into air holes, which makes PCF interesting for a wide range of applications. Recently, PCF has been a hot topic in optical communication and optical electronics. 
    Prof. Zhang Xuedian et al. (University of Shanghai for Science and Technology) proposes a PCF structure design with smaller sized elliptical holes in the core and square air holes in the cladding. With a full vectorial finite element method and anisotropic perfectly matched layers as the external boundaries, the impact of different core ellipticity and core filling materials on the birefringence, dispersion and nonlinearity of the photonic crystal fiber is investigated in the wavelength range of 0.6 μm ~2.0 μm. The results show that the birefringence increases with the ellipticity. No obvious effect of ellipticity on dispersion is found. Whereas, the near zero dispersion flat characteristics are achieved with the increase of wavelength. The nonlinear coefficients increase with the ellipticity below the wavelength of 1.33 μm, whereas the contrary changes are achieved above the wavelength of 1.33 μm. Besides, four oxide glasses with different indexes, including TT(20Tl2O.80TeO2)、TS(20Tl2O.80Sb2O3)、PG(80PbO.20Ga2O3) and As2S3, are filled in the elliptical core and important properties such as dispersion, birefringence and nonlinearity are analyzed. The results show that dispersion, birefringence and nonlinearity increase with the indexes of filling materials and the important property values are all above the ones of the conventional fibers. All these advantages make PCF a good candidate generation in supercontinuum and optical communication.

Elliptical core, square air hole cladding PCF structure

About Team
Prof. Zhang’s group is affiliated to Songlin Zhuang’s Academician team. Research in Prof. Zhang’s laboratory has been focusing on optical fiber sensing area. They have published some research articles in the scientific journals including Optics Letters, Optics Communications, Optical Materials, etc. In fiber sensing area, Prof. Zhang’s group fulfilled 973 project, Ministry of Science and Technology project and many other projects entrusted by enterprises. On the other hand, the group also applied for or possessed a number of patents in the field of optical fiber sensing, and conducted research and development work based on optical fiber technology for practical applications. 

Zhang X D, Yuan M M, Chang M, et al. Characteristics in square air hole structure photonic crystal fiber[J]. Opto-Electronic Engineering, 2018, 45(5): 170633