Diffractive optical elements for the formation of "light bottle" intensity distributions

Nonlinear generation of an optical bottle beam in domain-engineered ferroelectric crystals

Nonlinear wavefront shaping in periodically poled ferroelectric crystals has received great attention because it offers a convenient way to generate a structured light beam at new frequencies. In contrast to structurally uniform beams like Laguerre-Gaussian or Hermite-Gaussian modes, here we demonstrate the possibility to generate a spatially varied optical bottle beam via a frequency doubling process in a domain-engineered Sr0.61Ba0.39Nb2O6 (SBN) crystal. The nonlinear holography method was employed to design the modulation pattern of the second-order nonlinear coefficient χ(2), and the femtosecond laser poling was used to imprint the χ(2) pattern into the SBN crystal via ferroelectric domain inversion. The second harmonic bottle beam with zero intensity in its center that is surrounded in all three dimensions by light was observed with the incidence of a fundamental Gaussian beam. These results are useful for nonlinear generation and control of structured light at new frequencies, which has important applications in nonlinear photonics and quantum optics.

Quasi-achromatic Fresnel zone lens with ring focus

The phase of a standard Fresnel zone lens (FZL) is periodically modulated in the radial direction using the phase of a binary fraxicon. The resulting element (rf-FZL) focuses light into a ring. The ring is found to be quasi-achromatic, in that the diameter is wavelength independent but its location is not. The binary rf-FZL is fabricated using electron beam direct writing. Experimental results confirm the generation of a wavelength-independent ring pattern at the focus of the rf-FZL. An efficiency of 24% was obtained. The variation in radius of ring pattern was reduced from 61 μm to less than 10 nm for a corresponding wavelength variation from 532 to 633 nm.

Creation of vectorial bottle-hollow beam using radially or azimuthally polarized light

We propose a single-beam generation scheme to obtain a bottle-hollow (BH) beam using a binary phase mask and a focusing lens. The resulting BH beam is shown to possess an open bottle-shaped null intensity region, which has two hollow tube-shaped null intensity regions located on two opposite sides of this bottle. It is found that this scheme works identically under incident illumination with radial or azimuthal polarization. Another advantage of this scheme is that the same binary mask can be employed as a focusing lens with different choices of numerical aperture (NA). Furthermore, we observe that the length of the BH beam is inversely proportional to NA2 while the diameters of both the bottle and hollow regions are inversely proportional to NA; thereby leading to an adjustable BH beam. This BH beam may find attractive applications in noninvasive manipulation of microscopic particles over large distances.