It has been decades for laser pointer to control spin to produce light, but the orbital angular momentum produced in lasers is not so simple. The optical orbital angular momentum is created by twisting the phase of light into a spiral shape, forming a spiral shape.
Because the closer to the center of the beam, the distortion of the mode becomes tighter and tighter until the light disappears. Such a beam is usually called a ring beam or a vortex beam. The problem is that usually the laser cannot distinguish whether the light is rotating in a clockwise direction or the light is rotating in a counterclockwise direction, so the laser is just a combination of uncontrolled ways.
In addition, the beam produced by a single laser combining spin and orbital components is a mixture of two momentums, which has not been proven before. Our novelty is the realization that by using custom geometric phase polarization optics to draw the orbital angular momentum, the laser can distinguish between clockwise and counterclockwise light,” Forbes said.
Control is achieved by simply rotating a single optical element in the green laser pointer, without any other adjustments required. Such beams have been used in optical communications and optical particle capture and measurement, and they can now be created with a single laser as required.
The geometric phase of light is a very abstract concept that first appeared in quantum theory, but researchers here have used it to create specific types of distorted light. The custom light, called q-plate, adjusts the deflection of the orbital angular momentum according to the polarization torsion characteristics, and maps from one to the other.