Full Vectorial Finite Difference Beam Research Articles

Highly uniform and polarization-independent Y-branch with mode filter based on deeply etched silica-on-silicon waveguide

A slight misalignment between an optical fiber and a Y-branch would excite high-order modes and subsequently induce a snaking behavior of the input light, which would dramatically deteriorate the device performance. Here, a highly uniform and polarization-independent Y-branch based on deeply etched silica-on-silicon (SoS) waveguide is proposed, optimized, fabricated, and characterized, in which a mode filter with the quadratic-spline boundary is inserted to suppress the high-order modes. The proposed Y-branch is optimized by using three-dimensional full-vectorial finite difference beam propagation method. The experimental results show that the proposed Y-branch is with an ultra-low nonlinearity over a broad bandwidth from 1250 nm to 1620 nm, a low polarization dependent loss of less than 0.2 dB, and an ultra-low relative power difference of less than 0.04.

Passive polarization rotator based on silica photonic crystal fiber for 1.31-μm and 1.55-μm bands via adjusting the fiber length

A new polarization rotator based on the silica photonic crystal fiber is proposed. The proposed polarization rotator photonic crystal fiber (PR-PCF) possesses a triangle jigsaw-shape core region. The full-vector finite-element method is used to analyze the phenomenon of polarization conversion between the quasi-TE and quasi-TM modes. Numerical simulations show that the wavelengths of 1.31 μm and 1.55 μm are converted with a nearly 100% polarization conversion ratio with their matched coupling length and has a relatively strong realistic fabrication tolerance −100 nm on the y axis and 50 nm on the x axis. The full vectorial finite difference beam propagation method is used to confirm the performance of the proposed PR-PCF.

Polarization converters in highly birefringent microfibers

A novel type of polarization converters (PCs) based on highly birefringent (Hi-Bi) microfibers is presented. Analytical formulation based on the Jones Matrix method and a numerical code based on the Full Vectorial Finite Difference Beam Propagation Method are developed to analyze the polarization evolutions in such PCs. Two different design configurations, namely the "one-side" and "two-side" perturbation configurations, are studied by use of the two methods, and the results obtained agree well with each others. The PCs can be flexibly designed to have different operating wavelengths, spectral bandwidths, and devices lengths. A particular PC based on an elliptical microfiber demonstrates a bandwidth of ∼ 600 nm around 1550 nm with a device length of ∼ 150 μm.

Analysis of polarisation conversion in cascaded bent photonic crystal fibre

A rigorous analysis of polarisation conversion in a novel design of cascaded bent silica photonic crystal fibre is proposed using full vectorial finite difference method as well as full vectorial finite difference beam propagation method. The influence of different structural geometrical parameters on the polarisation rotator performance is investigated. The numerical results reveal that by a careful adjustment of the structural geometrical parameters and bending radius, nearly a 100% polarisation conversion ratio with nine sections only and low bending losses can be achieved.

Novel Design of Ultra-Compact Triangular Lattice Silica Photonic Crystal Polarization Converter

A novel design of ultra-compact polarization rotator (PR) based on triangular lattice silica photonic crystal fiber is proposed and analyzed. The suggested design has a central air hole which can be shifted in x and y directions to achieve complete polarization rotation. The influence of the different structure geometrical parameters and operating wavelength on the PR performance is investigated. The simulation results are obtained using full vectorial finite difference method as well as full vectorial finite difference beam propagation method. The numerical results reveal that the reported PR can provide nearly 100% polarization conversion ratio with a device length of 206 μm. It is also expected that over the 1.5-1.6 μ m wavelength range, polarization conversion would be more than 99%.

Design Consideration of Polarization Converter Based on Silica Photonic Crystal Fiber

In this paper, the performance of a novel design of passive polarization rotator (PR) based on silica photonic crystal fiber is studied and analyzed using the full vectorial finite difference method along with the full vectorial finite difference beam propagation method. The proposed design has a rectangular core region with a slanted sidewall. The influence of the different structure geometrical parameters and operating wavelengths on the PR performance is investigated. At a wavelength of 1.55 μm, nearly 100% polarization conversion ratio is obtained, with a device length of 2839 μm. In addition, it is expected that over the 1.5 to 1.6-μm wavelength range, polarization conversion would be more than 99%.

Passive Polarization Converters Based on Photonic Crystal Fiber With L-Shaped Core Region

In this paper, novel designs of single and multiple sectioned passive polarization rotators (PRs) based on silica photonic crystal fiber (PCF) are studied and analyzed. The suggested PCF PRs have an L-shaped core region which offers nearly 100% polarization conversion ratio. The simulation results are obtained using the full vectorial finite difference method along with the full vectorial finite difference beam propagation method. The influence of the different waveguide parameters and operating wavelength on the PRs performances are investigated in order to obtain optimum PR designs. The single and multiple sectioned PCF PRs offer nearly 100% polarization conversion ratio with device lengths of 1743 μ m and 1265 μ m, respectively.

Integrated-optic polarization rotator with obliquely deposited columnar thin film

A new integrated-optic polarization rotator with anisotropic cladding formed by oblique angle deposition is presented. Optical anisotropy with tilt principal axes in the obliquely deposited columnar thin film induces hybrid polarization modes in the waveguide and thus produces polarization rotation. The dependence of device characteristics on columnar film parameters, such as column angle, film thickness, extraordinary index, and optical anisotropy, is investigated by 3D full-vectorial finite difference beam propagation method. The polarization rotator with Ta2O5 columnar thin film has polarization conversion efficiency as high as 99% and extinction ratio of 25dB.

Coupling Characteristics of Dual Liquid Crystal Core Soft Glass Photonic Crystal Fiber

In this paper, the coupling characteristics of a novel design of soft glass photonic crystal fiber with dual nematic liquid crystal core (SGLC-PCF) are introduced and analyzed. The index contrast between the core and cladding region ensures the index guiding through the reported coupler. The analysis is carried out using the full vectorial finite difference method along with the full vectorial finite difference beam propagation method. The numerical results reveal that the SGLC-PCF coupler can be used as a polarization splitter of length 6232 μm with low crosstalk better than -20 dB with great bandwidths of 250 nm and 60 nm for the quasi transverse electric and quasi transverse magnetic, modes, respectively. In addition, the proposed splitter has a tolerance of ±3% in its length which makes the design less sensitive to the perturbation introduced during the fabrication process.

Design of passive polarization rotator based on silica photonic crystal fiber

We propose and analyze a novel (to the best of our knowledge) design of a polarization rotator (PR) based on silica photonic crystal fiber. The proposed design has a rectangular core region with a slanted sidewall. The simulation results are obtained using the full vectorial finite difference method as well as the full vectorial finite difference beam propagation method. The numerical results reveal that the suggested PR can provide a nearly 100% polarization conversion ratio with a device length of 3102 μm.

Coupling characteristics of a soft glass nematic liquid crystal photonic crystal fibre coupler

This study presents the coupling characteristics of a novel soft glass photonic crystal fibre (PCF) coupler infiltrated with a nematic liquid crystal (NLC–PCF). The soft glass provides optical properties that cannot be obtained by silica such as high refractive index, high rare earth solubility and mid-infrared transmission. In addition, the nematic liquid crystal (NLC) offers high tunability with the temperature and external electric field, and increases the birefringence between the two fundamental polarised modes in the proposed coupler. Therefore the NLC–PCF coupler has stronger polarisation dependence than the low birefringence conventional silica PCF coupler. The effects of the coupler geometrical parameters, rotation angle of the director of the NLC and temperature on the coupler performance are investigated. The analysis is carried out using the full vectorial finite difference method and the beam propagation study is performed by the full vectorial finite difference beam propagation method. The numerical results reveal that the polarisation dependence of NLC–PCF coupler is approximately 2.5 times that of the conventional silica PCF coupler with shorter coupling length. In addition, the NLC–PCF coupler has strong potential to offer practical design for short polarisation splitter as well as multiplexer–demultiplexer.

Multiplexer–Demultiplexer based on nematic liquid crystal photonic crystal fiber coupler

A novel design of Multiplexer–Demultiplexer (MUX–DEMUX) based on index guiding soft glass nematic liquid crystal (NLC) based photonic crystal fiber coupler is proposed and analyzed. The simulation results are obtained using the full vectorial finite difference method as well as the full vectorial finite difference beam propagation method. The numerical results reveal that the proposed MUX–DEMUX of length 3.265 mm can provide low crosstalk better than −20dB with great bandwidths of 40 and 24 nm around the wavelengths of 1.3 and 1.55 μm, respectively. In addition, the reported MUX–DEMUX has a tolerance of ±3% in its length which makes the design more robust to the perturbation introduced during the fabrication process.