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(a) The general diamond structure. (b) The diamondlike structure. (c) The beam geometry for diamondlike structure. (d) Constant-intensity surfaces in the interference pattern generated using the laser beam geometry shown in (c). The shaded areas correspond to regions where the intensity exceeded the threshold value.
(a) Band structures for the inverse diamondlike structure. The structure has been optimized to show a maximum band gap between the second and third bands. Parameters used for calculation: , . (b) Ratio of gap width (between second and third bands) to midgap frequency for diamondlike structures with different and different refractive contrasts. Positive ratio, above the hatched region, corresponds to a complete photonic band gap.
SEM images of photonic crystals fabricated by holographic lithography. (a), (b) The fabricated crystals exhibit a high degree of order over areas of few , inheriting the diamondlike structure of the interference pattern. (c)–(h) are the SEM close-up of the three special samples and the corresponding plots by simulation. (c) Close-up of the sample with top surface on (114) crystal plane. (d) Simulation of the diamondlike structure’s (114) crystal plane. (e) Close-up of the sample whose top surface is (110) crystal plane. (f) Simulation of the diamondlike structure’s (110) crystal plane. (g) Close-up of the fabricated crystal with a large sample tilt. The top surface is the (111) crystal plane; because the film has been fractured along the cleavage planes, the other surface is the crystal plane. (h) Simulation of (g).
(a) Transmittance (dashed line) and reflectance (solid line) of the fabricated crystal shown in Fig. 3(e), which is measured along the  direction . Photonic band gap at around is clearly visible as a pronounced reflection peak and transmission dip. (b) The corresponding band-structure calculation. The gray shaded area corresponds to the direction measured.
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