  We present a technique to optically induce a defect site in helical lattice
wave-field where the combined wave-field continues to maintain its
nondiffracting (ND) nature. This is done by coherently superposing a helical
lattice wave-field and a Bessel beam by method of phase engineering. The
results are confirmed by numerical simulations and experimentally as well by
generating the ND defect beam by displaying the numerically calculated phase
pattern on a phase-only spatial light modulator. This technique is wavelength
independent, completely scalable, and can easily be used to generate or
transfer these structures in any photosensitive medium.

Optics