Embedding a nondiffracting defect site in helical lattice wave-field by optical phase engineering.

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.