Source: http://proxy.osapublishing.org/oe/abstract.cfm?uri=oe-26-13-17264
Timestamp: 2019-04-22 17:03:59+00:00

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—A novel photonic crystal fiber (PCF) design that yields very high birefringence is proposed and analyzed. Its significantly enhanced birefringence is achieved by filling selected air holes in the cladding with an epsilon-near-zero (ENZ) material. Extensive simulation results of this asymmetric material distribution in the lower THz range demonstrate that the reported PCF has a birefringence above 0.1 and a loss below 0.01 cm−1 over a wide band of frequencies. Moreover, it exhibits near zero dispersion at 0.75 THz for both the X- and Y-polarization modes and a birefringence equal to 0.28. This THz PCF is then scaled successfully to optical frequencies. While the high birefringence is maintained, this optical PCF has a very high loss in its Y-polarization mode and, consequently, yields single-polarization single-mode (SPSM) propagation, exhibiting near zero dispersion at the optical telecom wavelength of 1.55 μm. The ideal ENZ materials used for these conceptual models are replaced with realistic ones for both the THz and optical PCF designs. With the currently available ENZ materials, the realistic PCFs still have a high birefringence, but with higher losses compared to the idealized results. Future developments of ENZ materials that achieve lower loss properties will mitigate this issue in any frequency band of high interest.
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Fig. 1 Cross sectional view of the complementary PCFs. (a) Type 1. (b) Type 2.
Fig. 2 Comparisons of the performance characteristics of the Type 1 and Type 2 PCFs. (a) Birefringence. (b) CL. (c) EML. (d) TL. (e) Dispersion.
Fig. 3 Simulated PCF performance characteristics for different lattice constants and for both the X- and Y-polarized modes as functions of the source frequency. (a) Birefringence and TL values. (b) Dispersion values.
Fig. 4 Simulated performance characteristics of the geometrically and material asymmetric PCF as functions of the source frequency for different d2 and for both the X- and Y-polarized modes. (a) Birefringence and TL values. (b) Dispersion values.
Fig. 5 Optimized PCF. (a) Optimal configuration. Distributions of the magnitude of the electric field intensity distribution for the (b) X- and (c) Y-polarized modes. The white arrows designate the polarization direction. Blue represents low values; red represents high values.
Fig. 6 Simulated performance characteristics of the optimized PCF as functions of the source frequency. (a) Birefringence and TL values. (b) Dispersion values.
Fig. 7 Simulated optical PCF performance characteristics for both the X- and Y-polarized modes as functions of the source frequency. (a) Birefringence and TL values. (b) Dispersion values.
Fig. 8 The real and imaginary parts of the relative permittivity of 99.5% pure KCl as functions of the source frequency.
Fig. 9 Simulated properties of the THz PCF designed with KCl and Topas for different lattice periods Λ. (a) Birefringence. (b) TL. (c) Dispersion.
Fig. 10 The relative permittivity of AZO and the birefringence values of the optical PCF designed with AZO in the C band.

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