Ming-Yang Chen

Microstructured-core photonic-crystal fiber for ultra-sensitive refractive index sensing

We propose a novel photonic crystal fiber refractive index sensor which is based on the selectively resonant coupling between a conventional solid core and a microstructured core. The introduced microstructured core is realized by filling the air-holes in the core with low index analyte. We show that a detection limit (DL) of 2.02×10⁻⁶ refractive index unit (RIU) and a sensitivity of 8500 nm/RIU can be achieved for analyte with refractive index of 1.33.

Polarization and leakage properties of large-mode-area microstructured-core optical fibers.

A novel kind of highly birefringent large-mode-area optical fiber is proposed in this paper. Birefringence in the fiber is realized by the introduction of an anisotropic microstructured core. The microstuctured core is composed of down-doped silica rods embedded in the background of up-doped silica. Numerical investigations demonstrate that high birefringence on the order of 2x10(-4) and hexagonal profile mode fields with mode areas larger than 300 mum(2) can be achieved in the proposed fiber. The influence of doping levels on the properties of birefringence, confinement losses, and mode-areas of the fiber is also investigated. Based on the design, we also propose a novel kind of single-polarization single-mode optical fiber with a mode area of 725 mum(2) and an operating wavelength range as large as 340 nm.

Design of broadband polarization splitter based on partial coupling in square-lattice photonic-crystal fiber

We propose a design for a novel broadband polarization splitter based on an asymmetric dual-core square-lattice photonic-crystal fiber. The fiber is designed such that index-matched coupling between the two cores can be achieved for one polarization state, while only a part of the energy could be coupled for the other polarization state. Numerical results demonstrate that a device length of 5.9 mm shows extinction ratios as low as -20 dB with bandwidths as great as 101 nm.

Improved design of polarization-maintaining photonic crystal fibers

We propose the realization of single-polarization operation in highly birefringent photonic crystal fibers. The suppression of one of the polarization states is realized by introducing index-matched cladding defect waveguides. The leakage loss of the index-matched polarization state can be enhanced by nearly 4 orders of magnitude. In particular, polarization-dependent loss larger than 2.97 dB/m with transmission loss lower than 0.03 dB/m in a wavelength region ranging from 1.54 to 1.566 μm can be realized in one such fiber.

Highly birefringent rectangular lattice photonic crystal fibres

The dispersive and birefringent properties of rectangular lattice photonic crystal fibres with circular air-holes are investigated. The fibres have twofold rotational symmetry and present the split of the fundamental cladding mode and the lifted degeneracy of the two polarization states, which lead to large birefringence and special behaviour of group-velocity walk-off. The properties are closely tied to the underlying radiation states of the rectangular lattice. In addition, the technique of fabricating the proposed fibres with the stack-and-draw procedure is presented.

Bend Insensitive Design of Large-Mode-Area Microstructured Optical Fibers

Numerical investigation on the design of a novel kind of large-mode-area optical fiber is presented. Low bending loss propagation in the fiber is achieved by the introduction of low-index rods with small period and large normalized diameter in one segment of the cladding. Single-mode operation is realized by the introduction of low-index rods with large period and small normalized diameter in another segment of the cladding. When a conventional large-mode-area optical fiber is bent, it will generally experience large bend distortion and the mode area will reduce accordingly. To avoid that, a bend-resistant design by introducing a microstructure into the solid core of the proposed fiber is proposed. In particular, the mode area of one such fiber is always larger than 2000 μ m2 when the bending radius is larger than 30 cm at the wavelength of 1.064 μm.

Design of Asymmetric Large-mode Area Optical Fiber With Low-bending Loss

We propose the design of a simple large-mode area microstructured optical fiber with low bending loss and large loss difference between the fundamental mode and the high-order modes. Single-mode operation in the fiber is realized by the introduction of small diameter holes, whereas the bending loss of the fiber is realized by the introduction of three large holes in the two-ring hole microstructured optical fiber. We also introduce low-index rods into the core of the fiber, which can effectively compensate the reduction of mode area induced by bending the fiber.

Analysis of photonic bandgaps in modified honeycomb structures

By introducing an additional air hole into the center of each unit cell of the conventional honeycomb lattice, a new kind of structure that can support air guidance of light with low-order bandgaps is proposed. Numerical investigation indicates that, due to the generation of the lower order bandgaps, larger air-guiding photonic bandgaps (PBGs) than those of triangular structures can be achieved in the new structures. Furthermore, the proposed structures also provide additional freedom in tailoring PBGs.

Polarization properties of elliptical-hole rectangular lattice photonic crystal fibres

We explore the polarization properties of elliptical-hole rectangular lattice photonic crystal fibres. Analysis of the cladding fundamental space-filling modes indicates that the anisotropic properties of the cladding are closely tied to the underlying radiation states of the pure lattices, which are determined by the ellipticity of the elliptical hole, the width and height ratio of the rectangular lattice and the air-filling fraction. Furthermore, optimization of the fibre core by inserting a centre hole is also presented. The achievement of high birefringence and a broad single-mode region in the fibres is demonstrated numerically.

Design and Analysis of a Low-Loss Suspended Core Terahertz Fiber and Its Application to Polarization Splitter

We propose the design of a low-loss suspended core terahertz fiber with rectangular-shaped dielectric strips in the fiber cross section. The finite element method is used to analyze the characteristics of the suspended core terahertz fiber. Terahertz wave in a frequency range from 0.74 ~ 0.95 THz is efficiently confined in the suspended core region with a total loss lower than 0.086 dB/cm ( ~ 0.02 cm-1). Meanwhile, any contact on the surface of this fiber will not disturb the field and induce additional losses. A 3.36-cm-long terahertz polarization splitter derived from this fiber with a transmission loss less than 0.89 dB, is also numerically demonstrated. A bandwidth of 0.032 THz at the center frequency of 1 THz with an extinction ratio better than -20 dB is obtained.