ABSTRACT
In 1987, the pioneering works by Yablonovitch1 and John2 suggested that a threedimensional (3D) photonic band-gap (PBG), which is analogous to an electronic band-gap in semiconductor materials, can be realized in articial periodic dielectric structures, namely, photonic crystals.3 The PBG was predicted to enable 3D connement of light in a wavelength-sized volume without accompanying substantial loss, which is difcult to achieve in other media. As tight light connement can enhance various light-matter interactions and can also realize very efcient nanophotonic devices/circuits, there have been extensive studies during the last two decades.4 Although the 3D PBG was indeed realized in several structures, the expected strong light connement has not been achieved yet.5 This is mainly because 3D PBG can exist only in a very limited class of photonic crystals (most of them are categorized into “diamond” structures6,7), which are rather complex structures and thus difcult to fabricate with sufcient accuracy by available methods.
