Refractive Bessel lattice in azobenzene liquid crystal

ABSTRACT

A refractive Bessel lattice with micrometric periodicity is induced optically in a photosensitive azobenzene liquid crystal cell of 3 µm thickness by a green 532 nm, 30 mW Bessel beam and with simultaneous illumination by a red 632.8 nm, 15 mW Gaussian beam. The uninterrupted action of both beams plays a key role in the complete mechanism of the refractive lattice formation. The lattice formation is investigated in real-time by the measurement of forward diffracted ring powers from both the red Gaussian and the green Bessel beams. The diffraction efficiency is investigated depending on the green Bessel beam intensity and on the mutual relation between the green beam polarization and the rubbing direction of the cell. A maximum diffraction efficiency of 1.1% is obtained which corresponds to a refractive index change of 6 × 10⁻³. Simulations are performed and a physical model to explain the experimental results is discussed.

KEYWORDS:

• Refractive lattice
• azobenzene liquid crystals
• Bessel beam
• diffraction
• diffusion
• photoisomerization

Acknowledgements

The authors would like to thank L. Tadevosyan for technical support in part of the experimental measurements.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

Varsenik Nersesyan is a joint Ph.D. student between the Institute for Physical Research of National Academy of Sciences of Armenia and Ghent University, Belgium and appreciates the scholarship through the Ghent University. This research is performed under financial support of the International Science and Technology Center Grant, Project A - 2130, awarded to the Photonics Department of the Institute for Physical Research.