Variable Collimated Hollow Laser 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”).

Variable Collimated Hollow Laser 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.

Variable Collimated Hollow Laser 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). The setup consists of indigenously developed metal axicon mirrors and few commercially available optical components, as shown below in Figure-2.

The invented Variable Collimated Hollow Laser 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:

• 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.
• Hollow beams and Bessel beams are also used in laser welding of materials.
• Hollow/Bessel beams are also used as tweezers for trapping of particles and biological cells.
• Large diameter hollow beams can be used in laser scanning applications.

INFRASTRUCTURE

• Mechanical workshop for fabrication of axicon mirrors and the mechanical hardware for the setup. Alternatively, this can also be done by outsourcing the same within the country.
• The axicon mirrors need to be surface finished with diamond turning machine. This can also be done by outsourcing within the country.
• Some optics like polarizing beam splitter (PBS) and quarter-waveplates are required, which are easily commercially available.

SPACE

• 12ft x 12ft space is sufficient.

MANPOWER

• One person skilled in optics can assemble and test the device in 2-3 days, if components are ready.

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

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).