Design of a Polarization Splitter for Ultra-broadband Dual-Core Photonic Crystal Fiber

A novel ultra-broadband polarization splitter based on dual-core photonic crystal fiber (DC-PCF) is designed. The full-vector finite element method (FEM) and coupled-mode theory are employed to investigate the characteristics of the polarization splitter. According to the numerical results, graphene-filled layer can not only broaden the working bandwidth but also reduce the size of polarization splitter. Furthermore, the fluorine-doped region and the germanium-doped region could broaden the bandwidth. Apart from that, the 4.78-mm-long polarization splitter can achieve an extinction ratio of -98.6 dB at the wavelength of 1550 nm. When extinction ratio is less than -20 dB, the range of the wavelength is 1027-1723 nm with a bandwidth of 696 nm. Overall, the polarization splitter can be applied to all-optical network communication system in the infrared and near-infrared wavelength range.

Polarization Splitter-Rotator Based on Multimode Waveguide Grating

We demonstrate a polarization splitter rotator (PSR) based on multimode waveguide grating (MWG) on a silicon-on-insulator (SOI) platform. Bloch mode hybridization in mini-stopband is exploited to achieve high polarization conversion efficiency. The fabricated device yields a high extinction ratio of > 53 dB and > 31 dB, low crosstalk of < −26.4 dB and < −40 dB for the injected TE0 and TM0 mode, with average insertion loss of 1.2 dB and 1.5 dB in the wavelength regime 1552 nm–1562 nm. Such a device shows great design flexibility and an easy fabrication process, serving as a good candidate in integrated polarization diversity circuits, especially for applications requiring spectra manipulation. Additionally, the polarization conversion approach provides opportunities to develop novel polarization management devices.

Reduction in Crosstalk Using Uniform Germanium Strips for Dense Integration of Photonic Waveguides

The requirement of low crosstalk between the neighboring waveguides should be considered essentially, in order to achieve the compact photonic integrated circuit (PIC), which includes photonic waveguides. Literature shows that the lower crosstalk can be realized by using the silicon-on-insulator (SOI) based waveguide, having an appropriate separation between them. The current work is focused on reducing the waveguide separation to further improve the photonic integration over the PICs. This has been achieved by inserting the germanium strips between the photonic waveguides. The investigations of the impact of variations in heights and widths of germanium strip have demonstrated that the crosstalk can be reduced by a significant amount, which provides noteworthy improvement in coupling length. The maximum coupling lengths of 81578 µm, 67099 µm, and 66810 µm have been achieved at their respective end-to-end separations of 300 nm, 250 nm, and 200 nm, and their corresponding minimum crosstalk values have been noted as -29.40 dB, -27.71 dB, and − 27.70 dB. Moreover, the analysis to realize the coupling length for Ge-strip, have been compared with the Si-, and SiN-strips. The approach presented in the current work can be utilized for the design of many compact photonic applications, such as polarization splitter, integrated photonic switches, etc.