If clockwise polarized light passes through the fiber without twisting the phase, the output is counterclockwise polarized light and the phase is clockwise twisted. By adding these elements to the laser pointer, the polarization twist (rotation) is controlled in the twisting direction of the orbital angular momentum, and the output is also controllable. “We like to call it a spiral laser, because the polarization and orbital angular momentum of the beam both play a role in the generation of light, and it rotates or twists in a complicated way,” Forbes said.
What is important is that the same laser can produce any combination of these orbital angular momentum beams and various polarized beams. The research team also discovered that the light output is produced by an arbitrary vector vortex beam, which is called a high-order Poincaré sphere beam.
For example, in addition to the special case of the orbital angular momentum beam, the same laser will also produce radial and angular polarization, and the polarization (electric field direction) will change in space. For example, radially polarized light always points away from the center of the circle, which is very useful when cutting metal.
This kind of beam is often called a “vector” beam because the polarization changes across the beam. When the polarization mode remains constant throughout the beam, it is called a “scalar” beam. In the paper, the researchers have shown that both beams can be created by the same laser.
It must be understood that the vector vortex laser beam has proven to be very useful in the processing of metals and other materials, for example, in the automotive industry. But until now we can’t generate all these beams in the same green laser pointer, and the ongoing experiments are also part of his own Ph.D. research, and he is also the main author of the paper.
The concept of laser is likely to attract interest from academia and industry. Vector and scalar vortex beams with high-order Poincaré sphere phases have many applications, such as microscope imaging, laser processing, and can be used for free space and optical fiber communications. Usually, it is necessary to decide in advance which beam is the most desired, and then design a laser. Now, it becomes possible to use a single laser to meet the needs of different laser beams.