Ultrabroadband polarization splitter based on a modified three-core photonic crystal fiber

Abstract

An ultrabroadband polarization splitter based on a modified three-core photonic crystal fiber is proposed. Two fluorine-doped cores and a central microstructured modulation core are introduced to achieve an excellent performance and an ultrawide bandwidth. Numerical simulation demonstrates that the splitter has a bandwidth as wide as 300 nm, with an extinction ratio (ER) as low as -20 dB. At the wavelength of 1.55 μm, the ER reaches -30 dB. All the air holes in our design are circular holes and are arranged in a triangular lattice that is easy to fabricate with the method of stack and draw. A suitable mode field area and a Gaussian-like mode field distribution lead to a low splicing loss that is as low as 0.04 dB when splicing with standard single-mode fibers as the lead-in and lead-out ports.

Design of Short-Length Polarization Beam Splitter Based on Highly Birefringent Dual-Core Photonic Crystal Fiber

“…However, the larger separation may bring the convenience of connecting with other external devices. In addition, the wavelength bandwidth of high extinction ratio may be further enlarged by introducing depressed-index fluorine-doped cores [25,26,36] or embedding a defected air hole into the core in our opinion. Till now, PCFs with different structures have been fabricated by stack-and-draw technique, performs drilling method, die-cast process, and sol-gel casting method, etc.…”

“…So far, various theoretical models on analysis of PCFs have been developed, such as effective index approach, plane wave method, BPM, multi-pole method, and FEM [34]. Compared with other methods, the full vector FEM with curvilinear hybrid edge/nodal elements is capable of accurately dealing with the curved boundaries of air holes in PCFs [35], and it has been widely used in the study of PCF properties, including modal birefringence, chromatic dispersion, confinement loss, as well as the coupling property [25][26][27][28][29][30]. In the simulation, we firstly use the full-vector FEM to accurately investigate its basic characteristics and optimize the value of CLR, and then employ semi-vector BPM to analyze the propagation behaviour and extinction ratio for the optimum structure.…”

“…Besides, in order to select the desired coupling mode by the index-match method, the geometrical constructions are always very complicated to the current fabrication technique. The second type of PBSs is based on symmetric identical twin-core PCFs, relying on the high birefringence to produce a large difference of coupling lengths between x-and y-polarized modes [24][25][26][27][28][29][30]. Zhang and Yang [14] firstly reported the symmetric dual-core PCF-based PBS, and showed that the splitting ratio better than −11 dB and a bandwidth of 40 nm could be achieved in a 1.7 mm length.…”

“…Florous et al [24] proposed a 15.4 mm-long symmetric PCF beam splitter with uniform elliptically-shaped air holes. Lu et al [25,26] realized an ultra-broadband PBS by introducing two fluorine-doped cores with the device length of more than 80 mm. Recently, Jiang et al [27] designed an circular-elliptic hybrid air-hole PBS with the ultra-short length of 119.1 µm, in which the high extinction ratio of 118.7 dB at λ = 1.55 µm and broad bandwidth of 249 nm could be achieved.…”

Design of short polarization splitter based on dual-core photonic crystal fiber with ultra-high extinction ratio

“…In 2003, Zhang and Yang proposed a polarization splitter based on dual-core PCFs for the first time, whose ER at the wavelength of 1.55 mm can reach À 11 dB with a length of 1.715 mm [12]. In 2013, Lu et al proposed a ultra-broadband polarization splitter based on a three-core PCF, the splitter had a bandwidth as wide as 300 nm with an ER better than À 20 dB, and the ER can reach À 30 dB at the wavelength of 1.55 mm with a length of 84.7 mm [13]. In 2014, Sheng et al proposed a compact polarization splitter based on dual-elliptical-core PCF, the splitter had the length of 775 mm and up to 50 dB ER at the wavelength of 1.55 mm,and the bandwidth could be 32 nm with the ER over 20 dB [14].…”