From eyeglasses to telescopes to cameras, the lens is an essential optical device used in much of today’s technology. After two years of work, scientists at the Australian National University have succeeded in developing the world’s thinnest lens, which is thousands of times thinner than a human hair, according to a Friday press release.
Yuerui Lu, a professor at ANU and the lead investigator of the study, said the lens arrays would be used to mimic the compound eyes of insects and advance 3-D imaging, flexible optical displays and electronic devices. The thinness of the lens is made possible by a molybdenum disulphide crystal, a flexible material that is increasingly used in computer displays and electronic devices. Lu and his team researched and utilized the many unexpected qualities of the molybdenum disulphide crystals to make their lens.
One of these qualities was the crystal’s long optical path length, which measures the distance traveled by the light that passes through the object.
“We were surprised to find that even though the physical thickness of this material is around 0.7 nanometers, its optical path lengths could be up to around 38 nanometers,” Lu said.
Theodore Moustakas, a Boston University College of Engineering professor and the associate head of the Division of Materials Science, highlighted the characteristics of good materials for lenses such as these.
“What is important is that the light that propagates through the material can undergo two types of scattering,” he said. “One is called inelastic scattering in which the light uses some energy as it propagates, and the other type is elastic, in which the light propagates through the material and it does not lose energy.”
The usefulness of molybdenum disulphide is its high refractive index, a quantity that measures the strength of the material’s effect on light, Moustakas said.
“It happens that [molybdenum disulphide] has this particular elastic property,” he said. “Even though the material is only 0.7 nanometers thick, because of its refractive index of 5.5, the light is bouncing 5.5 times from the front to back surfaces of the material, making the light travel a total of 38 nanometers instead of 0.7.”
With consumer electronics such as phones, tablets and computers getting thinner and more compact, an ultra-thin lens becomes an imperative component. At only 6.3 nanometers in thickness, this new lens surpasses its ultra-thin predecessor that measured 50 nanometers.
According to the press release, Lu’s team created the lens by peeling off a 6.3-nanometer-thick crystal from a larger piece using a piece of tape — a process made possible due to the material’s lack of covalent bonds. The researchers then used a focused ion beam to shear off atoms until they created a lens with a 10-micron radius.
The ability to manipulate light flow at an atomic level is a groundbreaking feat that will open the door for the unprecedented miniaturization of optical components, Lu said. He described the advantages of being able to do so with this lens.
“Lots of researchers are trying to fabricate ultra-thin and flat lenses,” he said. “If it is ultra thin and flat, then we can bend those lenses so they can be integrated into some flexible optical systems with advanced functionalities.”
Moustakas said he believes this new lens will have a significant impact in the making of miniature and specialty cameras.
“Right now, to make a miniature camera that has certain dimensions and that is able to accommodate all of the optical components, it is usually made from thicker materials,” Moustakas said. “As a result, the camera itself has a certain physical size.”
With this ultra-thin lens now available, Moustakas said he foresees miniature cameras greatly advancing with the utilization of these much smaller materials.
Though Lu said the price to mass produce these lenses and make them more mainstream is currently unknown, he does not believe it will be too expensive.
He added, “We are pushing in this direction so we can hopefully produce lots of lenses in a cheaper way.”
