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(Color online) (a) Band diagram of the TM modes of a PC slab for and . The light line is the red line. (b) SEM picture of a PC slab. (c) Photograph of the bottom of a PC slab.
The femtosecond laser beam is expanded and sent through a photomask. The image of the photomask is projected onto the sample with a lens. A pellicle beam splitter sends the PC surface reflection into a webcam. An imaging laser illuminates the air holes. Paraboloidal mirrors collect the emitted THz radiation from the PC and refocus it into a ZnTe crystal. The imaging laser and the EO probe beam pass through small holes drilled into the paraboloidal mirrors.
(Color online) (a) Spectra of an unprocessed wafer tilted at Brewster’s angle (upper trace log scale), the spectrum from sample I under uniform laser excitation (lower trace), and the spectra from samples I and II under the pattern laser excitation shown in (b) and (c), respectively.
Horizontal (a) and vertical (b) components of the emitted electric field with the triangular pattern of laser spots shown in Fig. 2. The unit cell diagrams indicate the positions of the laser pattern for horizontal (c) and vertical (d) polarizations, relative to the PC’s air holes. The colored spots in (c) and (d) correspond to the positions at which the data of the same color were taken in (a) and (b). (e) and (f) show FDTD-calculated fields of the degenerate dipole modes (color chart: red, positive; blue, negative).
(a) Integrated spectral power of the peak at as a function of the position of the stripe laser pattern for sample I. (b) Calculated spectral power from the dipole mode as a function of position. [(c) and (d)] component of the dipole mode showing the position of the laser stripe at the absolute maximum (c) and local maximum (d) of the integrated power in part (a). (e) electric field at the absolute maximum (purple) and local maximum (green) of the integrated power in part (a).
(Color online) (a) Tangential fields of the vertical dipole mode in a plane above the PC slab with their apodized Fourier transforms. (b) field of the vertical dipole mode in the PC slab. (c) Tangential fields and Fourier transforms of a quadrupole mode in a plane above the PC slab. (d) field of the quadrupole mode in the PC slab.
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