Technology for Transfer
Hollow Beam Generator

Laser Weld Rig

Figure-1: Block diagram of the Hollow Beam Generator. The insets at the left and right sides show the images of the input beam and output hollow beam respectively.

Hollow Beam Generator is a device which has been developed to generate a collimated hollow laser beam of variable diameter from an input laser beam of Gaussian/uniform spatial profile (Figure-1). An Indian patent has been granted to this invention (Patent Number 269505, Grant Date 26-Oct-2015, Title: “An Apparatus for Generation of Collimated Hollow Laser Beam”). The setup consists of indigenously developed metal axicon mirrors and few commercially available optical components, as shown below in Figure-2.

Laser Weld Rig
Figure 2: Schematic diagram of the apparatus developed for generation of a collimated hollow beam of variable diameter. AX1: convex axicon mirror (1), AX2: concave axicon mirror (2), γ : axicon mirror base angle, d: separation between axicon mirrors, PBS: polarizing beam splitter (6), λ/4: quarter wave-plate (5), LB: input laser beam (3), HB: hollow beam (4).

The Hollow Beam Generator can be used for a range of laser wavelength and power of the input beam. Hollow laser beams and their derivative Bessel beams (obtained by focusing a hollow beam) find applications in a variety of areas including basic R&D sciences and industries. Some of these are listed as following:
  1. Hollow beams are used for Laser Trepanning (i.e. drilling holes) in materials with precision and accuracy of micron size. The focused hollow beams (i.e. Bessel beams) with increased depth of focus are used for drilling holes in the range of sub-mm to few micron size without movement of the material piece.
  2. Hollow beams and Bessel beams are also used in laser welding of materials.
  3. Hollow/Bessel beams are also used as tweezers for trapping of particles and biological cells.
  4. Large diameter hollow beams can be used in laser scanning applications.

The technology of this device is available for transfer. Parties with expertise in lasers and laser based instrumentation, and interested in setting up facilities for production of this device, can send their enquiries to:

Dr. Sendhil Raja S.
Head, Technology Transfer Cell
Raja Ramanna Centre for Advanced Technology
Indore - 452 013 M.P.
Email:sendhil (at)