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Photonic band structure (TM-like mode) for the square PhCs with an effective refractive index and radius of the air hole of . A plane-wave expansion method was used. The black box represents the operating frequency range for Band 1 and the gray box that for Band 3.
EFCs for Bands 1 (a) and 3 (b). (a) As the incident frequency is changed from to , which correspond to 1250 and 1320 nm for , respectively, the propagation direction changes from −15° to 0° with respect to the incident direction. (b) In the frequency range of , corresponding to the wavelength range of 1500–1135 nm with , the shape of the EFCs is approximately square. It is clearly indicated that when the incident angle is varied from −10° or −5° to 5°, the angle difference for propagation directions in the PhC is enlarged to 90° (from -45° to +45°).
Field distribution for mode at different incident angles and wavelengths with an effective refractive index and radius of the air hole of . A Gaussian beam with a width of 2 μm is launched 2 μm away from the input interface. (a) Angular amplifier with 0° and −15° as the incident angles and . The results from these two graphs are consistent with those in Fig. 2(b), where the separation angle is enlarged six times by the angular amplifier. (b) Combined device with superprism and angular amplifier . When the wavelength of incident light varies from 1250 to 1320 nm, the light propagation directions in the superprism change from −15° to 0°, and then this separation angle is enlarged to 90° by the angular amplifier.
SEM (top view) of the beam splitter consisting of superprism and angular amplifier with input and output waveguides. The input waveguide is normal to the crystal edge, which is rotated 24° away from direction and cut flat. The output waveguides are extended into the crystal area to cancel the refraction effect between the uniform materials and PhC area.
Vidicon micrographs for the output spots at different wavelengths. This result shows that the input light is mainly deflected into the ±45° output waveguides, depending on wavelength.
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