Tuning Bessel beam propagation properties with liquid media

• Main Authors: Gabor, Donna H, Guerrero, Raphael A
• Format: text
• Published: Archīum Ateneo 2019
• Subjects: Bessel beams; Beam propagation method; Interfaces; Water; Refractive index; Glasses; Liquids; Refraction; Wave propagation; Ray tracing; Optics; Physics
• Online Access: https://archium.ateneo.edu/physics-faculty-pubs/15; https://www.spiedigitallibrary.org/conference-proceedings-of-spie/11107/1110707/Tuning-Bessel-beam-propagation-properties-with-liquid-media/10.1117/12.2528680.short
• Institution: Ateneo De Manila University

Techniques for optical trapping and micromanipulation, as well as precision drilling, have resulted from the ability to generate different types of Bessel beams. A standard method for producing Bessel intensity profiles involves an annular slit and focusing lens. The fixed geometry of this optical system only allows the generation of a particular Bessel beam with specific propagation properties. To increase the flexibility of a conventional annulus-lens configuration, we introduce a fluid-based method for modifying the core diameter and propagation properties of zero-order Bessel beams. In our optical set-up, Bessel beams are created with a HeNe laser operating at 543 nm with an output power of 4 mW. An annular slit is placed at the front focal plane of a lens with f = 25 cm. A transparent, custom-built container composed of three fluid chambers, each 5 cm in length, is placed after the lens. Our experiments make use of two fluids: water (n = 1.33) and vegetable oil (n = 1.43). Without using any fluids, at a propagation distance of 50 cm from the lens, our set-up produces a Bessel beam with core diameter = 0.231 mm. When the beam passes through a sequence of oilair-water, the core diameter at the same distance increases to 0.241 mm. We also observe an extended maximum propagation distance for a beam that travels through this combination of media. Modification of Bessel beam propagation properties is consistent with a change in effective focal length brought about by refraction through the liquid components.