Negatively and positively refractive behaviors are achieved in a two-dimensional photonic crystal of pillar type for TE and TM polarizations, respectively, at the same frequency. The photonic crystal is formed by a triangular lattice of silicon pillars of finite height on a silicon substrate. A polarization beam splitter based on such a photonic-crystal slab is demonstrated. Measurements at near infrared wavelengths indicate that two beams of different polarizations can be split with an extinction ratio of over 10 dB in a wide wavelength range.
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