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In this study we demonstrate a high-performance polarization rotator (PR) based on flat-shaped photonic crystal fiber. The flat surfaces of the fiber are plated on gold films as electrodes, and the core of the structure is filled with liquid crystal. The polarization rotation characteristics of the flat-shaped fiber can be effectively adjusted by applying external voltage. The optical properties are analyzed using the finite element method (FEM). The results show that the magnitude of the modulation voltage is closely related to the thickness of the flat fiber. When the fiber thickness is 20 μm, only 100 V is required to achieve the highest PR performance. In the wavelength of the 1.55 μm band (~200 nm bandwidth), the conversion length of the PR is only 3.99 μm, the conversion efficiency is close to 100%, and the minimum crosstalk value is −26.2 dB. The presented PR, with its excellent performance, might enable promising applications in the communication system and the photonic integrated circuits. [ABSTRACT FROM AUTHOR]

Beam splitters are vital components in several optical systems. It is highly desirable, and compact beam splitters with ultra-broadband performances, high efficiencies, and large split angles are still being sought. In this paper, we demonstrate and numerically investigate an ultra-broadband and highly efficient optical beam splitter based on a quasi-continuous metasurface. The proposed design is constructed of quasi-continuous triangle-shaped gallium phosphide nanoantennas on a silica substrate. The simple structure can achieve a conversion efficiency and an anomalous transmission intensity above 90% and 0.8 covering the wavelength range of 1537–1826 nm, respectively. The maximum beam split angle in the operating bandwidth reaches 131.84° at the wavelength of 1826 nm. Particularly, the operating bandwidth is still as high as 125 nm with the anomalous transmission intensity above 0.92 and the conversion efficiency exceeding 99%. Moreover, the results show that the performance of the metasurface-based optical beam splitter can be further enhanced by optimizing structural parameters. We also demonstrate the adjustability of the beam splitter by adding refractive index (RI) materials on the surface of the device. The results show that the incident plane wave can be divided into three beams with intensity adjustability. The presented metasurface is very promising in the fields of multiplexers, interferometers, and optical communications, owing to its advantages of ultra-broadband, highly efficient, and large split angle simultaneously. [ABSTRACT FROM AUTHOR]

We propose and numerically investigate a multi-parameter integrated sensor based on a selectively filled D-shaped photonic crystal fiber (PCF). The simple structure can be used to comprehensively detect refractive index, magnetic field, temperature, and voltage. According to the surface plasmon resonance and directional coupling effect, the PCF is coated with a gold nano-film to detect the refractive index of the external environment. In addition, magnetic fluid (water-based Fe3O4), toluene, and nematic liquid crystal (NLC E7) are selectively filled into different cladding air holes of the D-shaped PCF to realize the different sensing of the magnetic field, temperature, and voltage. The measurement of refractive index, magnetic field, temperature, and voltage are independent of each other, so these four parameters can be measured simultaneously. The sensing characteristics of the proposed structure are investigated systematically by the finite element method. The results show that the sensitivities of refractive index, magnetic field, temperature, and voltage are 4600 nm/RIU, 1.375 nm/Oe, 15.143 nm/°C, and 0.971 nm/V, respectively. The presented design based on materials selectively filled with D-shaped PCF might enable promising application in multi-parameter optical sensing. [ABSTRACT FROM AUTHOR]