Embedding defect sites into hexagonal nondiffracting wave fields
  We present a highly purposive technique to optically induce periodic photonic lattices enriched with a negative defect site by using a properly designed nondiffracting beam. As the interference of two or more nondiffracting beams with adequate mutual spatial frequency relations in turn reproduces a nondiffracting beam, we adeptly superpose a hexagonal and a Bessel beam to create the nondiffracting defect beam of demand. The presented wavelength-independent technique is of utmost universality in terms of structural scalability and does not make any specific requirements to the photosensitive medium. In addition, the technique is easily transferable to all pattern-forming holographic methods in general and its application is highly appropriate e.g. in the fields of particle as well as atom trapping. 
Andreas Kelberer, Martin Boguslawski, Patrick Rose, Cornelia Denz
physics.optics