Photonic crystal fibers

While the field of photonic crystals has been focused on optical components, there has been a group of researchers exploring the idea of using photonic band-gaps to provide confinement in optical fibers. Although the precursors of this technology can be found in the mid to late 1970s (Kaiser and Astle, 1974; Yeh et al., 1978), this earlier work did not recognize the full potential of air-clad or Bragg fibers. However, the idea of a photonic crystal fiber (PCF) (Birks et al., 1995) was revived soon after the introduction of the generalized concept of photonic band gaps (Yablonovitch, 1987; John, 1987) in the late 1980s. Unlike the original all silica-based Bragg fiber, the proposed PCF generated a band gap with a silica cladding containing a periodic lattice of air holes. Although it was several years before a true photonic band-gap.fiber (PBGF) was demonstrated (Knight et al., 1998; Cregan et al.´s, 1999), the original PCFs displayed some very unusual properties (Birks et al., 1997) that generated sufficient interest to distract the research from its original goal. In this paper, we examine the relationship between the early PCFs and the more recent PBGFs