Bessel beams are beam of laser light that are non-refracting and shaped liked the figure shown. The interesting characteristics about them are couple:
- 1.They do not diffract. Most light beams diffract and therefore do not make very good targets.
- 2.Their energy is spread over a larger area and therefore make great beams to work with cells
- 3.If the central beam is blocked then it gets recreated
- 4.They are like an interference pattern and so the beam distribution along the edge is theoretically infinite
They are created within a laser cavity wherein the interference of the light beams creates the Bessel beams. They are used in biology for various reasons:
- 1.As optical tweezers since the energy distribution is gradual and does no burn the cell
- 2.For microinjection, since it can be tuned to cause a gentle hole formation in the cell wall to inject the macromolecule of interest.
Bessel plane microscopy is now revolutionizing 3D imaging. Eric Betzig at Janelia Farm is utilizing a crossed Bessel beam microscope to look at cells in three dimensions. They have utilized super-resolution structured illumination microscopy for high speed, high resolution and low phototoxicity imaging.
Their fluorescent setup involves the use of 2 microscope objectives mounted at right angles to each other focused on an identical spot. One objective generates the scanning Bessel beam and the other objective measures the resulting fluorescence. Since the beam illuminates only a small area that is being interrogated, the phototoxicity is very limited. They have boosted the resolution to nearly 2-3 fold and their images are so good that is impossible to determine the normally weak, Z-dimension of the image from the X-Y-dimension.