New device widens light beams by 400 times

Wider light beams could boost the speed and sensitivity of medical imaging and diagnostic procedures.


Scientists at the National Institute of Science and Technology (NIST) have developed an efficient converter that enlarges the diameter of a light beam by 400 times.

At first, the light goes along an optical waveguide — a thin, transparent channel whose optical properties limit the diameter across of the beam to a couple of hundred nanometers, less than one-thousandth the normal width of a human hair.

Since the waveguide channel is so thin, a portion of the voyaging light broadens outward past the edges of the waveguide. Exploiting this broadening, the group put a rectangular slab made out of indistinguishable material from the waveguide a modest, definitely estimated separation from the waveguide. The light can bounce over the modest hole between the two segments and step by step spill into the slab.

The slab manages the limited width of the light in the vertical dimension, however, it gives no such limitations to the parallel, or sideways, measurement. As the gap between the waveguide and the slab is continuously changed, the light in the section frames an unequivocally coordinated bar multiple times more extensive than the around 300 nm measurement of the beam.

During the second stage of expansion, which enlarges the vertical dimension of the light, the beam traveling through the slab encounters a diffraction grating. This optical device has periodic rulings or lines, each of which scatters light. The team designed the depth and spacing of the rulings to vary so that the light waves combine, forming a single wide beam directed at nearly a right angle to the chip’s surface.

Importantly, the light remains collimated, or precisely parallel, throughout the two-stage expansion process, so that it stays on target and does not spread out. The area of the collimated beam is now large enough to travel the long distance needed to probe the optical properties of large diffuse groupings of atoms.

Scientists used the two-stage converter to successfully analyze the properties of some 100 million gaseous rubidium atoms as they jumped from one energy level to another. That is an imperative confirmation of-idea since devices dependent on cooperations among light and nuclear gasses can gauge quantities such as time, for example, time, length and magnetic fields and have applications in navigation, communications, and drug.

John Kitching of NIST in Boulder, Colorado said, “Atoms move very quickly, and if the beam monitoring them is too small, they move in and out of the beam so fast that it becomes difficult to measure them. With large laser beams, the atoms stay in the beam for longer and allow for more precise measurement of the atomic properties. Such measurements could lead to improved wavelength and time standards.”

The study is published in the journal Light: Science & Applications.

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