Monolayer transition metal dichalcogenide lens for high resolution imaging

August 13, 2020

Lenses are one of the most commonly used optical components in daily life, including eyeglasses, microscopic objectives, magnifying glass, and camera lenses. Conventional lenses are based on the principle of light refraction, using different materials, spherical surfaces and spatial positions to achieve the control of light. The fabrication of conventional lenses including the processes of material selection, cutting, rough grinding, fine grinding, polishing, and testing. In order to minimize the aberrations including the chromatic aberration, spherical aberration and astigmatisms, it is necessary to stack multiple layers of lenses to form compound lenses, leading to the complexity and cumbersomeness of current camera equipment.

Therefore, tremendous effort has been devoted into the development of ultrathin flat lenses. Unlike conventional lenses, flat lenses use nanostructures to modulate light. By controlling the optical properties and the spatial position of each nano-element, advanced functions, such as achromatic and aberration-free focusing, high spatial resolution and special focal intensity distributions can be achieved. However, when the material thickness is reduced to the subwavelength scale, the insufficient phase or amplitude modulation based on the intrinsic refractive index and absorption of the materials results in poor lens performance.

In a new paper published in Light Science & Application, a team of scientists, led by Prof. Baohua Jia at Centre for Translational Atomaterials, Swinburne University of Technology, Australia, Prof. Qiaoliang Bao formerly at Monash University, Prof. Chengwei Qiu at National University of Singapore and co-workers have developed an innovative method to fabricate high performance lenses in monolayer two dimensional transitional metal dichalcogenide (TMDC) material by using a femtosecond laser to pattern nanoparticles. The lens has a sub-wavelength resolution and a focusing efficiency of 31%, laying the foundation for ultimately thin optical devices for use in nano-optics and on-chip photonic applications.

Although lenses made from multilayer TMDCs have been demonstrated before, when their thickness is reduced to the sub-nanometer scale, their insufficient phase or amplitude modulation results in focusing efficiencies of less than 1%. The international team discovered that it is possible to generate nanoparticles by using a femtosecond laser beam to interact with the monolayer TMDC material, which is significantly different from the process produced by a continuous wave laser. When the laser pulse is so short that the entire material remains cold after laser process, the nanoparticles can firmly attach to the substrate. The nanoparticles show very strong scattering to modulate the amplitude of light. Therefore, the lens made from the nanoparticles can provide subwavelength resolution and high efficiency, which allows the team to demonstrate diffraction-limited imaging by using the lenses.

Monolayer is the thinnest form of a material, which is the ultimate physical thickness limit. By using the monolayer for the lens fabrication, the process demonstrated in this study consumed the least material meeting the theoretical limitation. More importantly, the femtosecond laser fabrication technique is a one-step simple process, without the requirements of high vacuum or special environment, thus it provides the simplest way to fabricate an ultrathin flat lens. As a result, the lens can be easily integrated into any photonic or microfluidic devices for broad applications.

"We have used the thinnest material in the world to fabricate a flat lens, and prove that the good performance of the ultrathin lens can lead to high resolution imaging. It shows enormous potential in different applications, such as eyeglasses, microscopy lenses, telescopes and camera lenses. It is foreseeable that by using this technique, the weight and size of camera lenses can be significantly reduced in the near future." Said Dr Han Lin, the first author from the Centre for Translational Atomaterials, Swinburne University of Technology.

"We are excited to see unique outcome from femtosecond laser processing 2D materials. It opens up new possibility to fabrication photonic devices using scalable method." Added by Prof. Baohua Jia, Director of Centre for Translational Atomaterials.

"We can integrate the monolayer 2D material lens onto desired devices by simply attaching the material then using a femtosecond laser to perform fabrication. The entire process is simple, and the method is flexible and low cost. Thus, we also see the great application potential of the method." Commented by Prof. Qiaoliang Bao formerly at Monash University.

"We design our lens in such a way that image can be found at different focal planes, with different magnifications. This mechanism can be readily used to develop an optical zoom lens that is required in all cellphone cameras. Currently, lenses with different focal lengths are used to achieve different zoom function. However, our lenses can achieve different zoom rates simply with one design." Prof. Chengwei Qiu from National University of Singapore forecasts.

Light Publishing Center, Changchun Institute of Optics, Fine Mechanics And Physics, Chinese Academy

Related Nanoparticles Articles from Brightsurf:

An ionic forcefield for nanoparticles
Nanoparticles are promising drug delivery tools but they struggle to get past the immune system's first line of defense: proteins in the blood serum that tag potential invaders.

Phytoplankton disturbed by nanoparticles
Products derived from nanotechnology are efficient and highly sought-after, yet their effects on the environment are still poorly understood.

How to get more cancer-fighting nanoparticles to where they are needed
University of Toronto Engineering researchers have discovered a dose threshold that greatly increases the delivery of cancer-fighting drugs into a tumour.

Nanoparticles: Acidic alert
Researchers of Ludwig-Maximilians-Universitaet (LMU) in Munich have synthesized nanoparticles that can be induced by a change in pH to release a deadly dose of ionized iron within cells.

3D reconstructions of individual nanoparticles
Want to find out how to design and build materials atom by atom?

Directing nanoparticles straight to tumors
Modern anticancer therapies aim to attack tumor cells while sparing healthy tissue.

Sweet nanoparticles trick kidney
Researchers engineer tiny particles with sugar molecules to prevent side effect in cancer therapy.

A megalibrary of nanoparticles
Using straightforward chemistry and a mix-and-match, modular strategy, researchers have developed a simple approach that could produce over 65,000 different types of complex nanoparticles.

Dialing up the heat on nanoparticles
Rapid progress in the field of metallic nanotechnology is sparking a science revolution that is likely to impact all areas of society, according to professor of physics Ventsislav Valev and his team at the University of Bath in the UK.

Illuminating the world of nanoparticles
Scientists at the Okinawa Institute of Science and Technology Graduate University (OIST) have developed a light-based device that can act as a biosensor, detecting biological substances in materials; for example, harmful pathogens in food samples.

Read More: Nanoparticles News and Nanoparticles Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to