Development of ultra-thin lens 10000 times thinner than previous lenses

[Photo provided = Ministry of Science and ICT] Schematic diagram of nanocomposite-based nanoprinting process and the silicon nanocomposite meta-lens manufactured through this (left in the photo) electron micrograph of the meta-lens (right) 4 mm meta-lens combined to a 1-inch lens tube

The domestic researchers succeeded in developing an ultra-thin lens that is 10000 times thinner than the present refractive lens opening a way to
dramatically reduce the size of the camera used in smartphones.

The Ministry of Science and ICT (Minister Ki-young Choi hereinafter MSIT) announced that Postech (Pohang University of Science and Technology president Moo-Hwan Kim) Department of Mechanical Engineering / Chemical Engineering Professor Jun-Seok Nohs research team developed mass production technology and the ultra-thin infrared lens maintaining the performance of the existing refractive lens but lowering the thickness to 10000 times thinner (100 times thinner than hair) with the cooperation of Heon Lee professor of Korea university Department of Materials Science and Engineering and Seung-hoon Hans master team of Imaging Device Lab Samsung Electronics Advanced Institute of Technology.

It is announced that this was recognized that it can be a research achievement that overcomes the limitations of large and heavy conventional optical devices* and contributes to the commercialization of metamaterials**. Therefore it was launched online on January 1st 2021 in ACS Nano (IF=14.588).

* Optical device : A device that can control various characteristics such as amplitude phase and frequency of light.

** Metamaterial : A new material formed of artificial atoms that mimic the atoms existing in nature.

Lenses that collect light are essential for the latest electronic devices and optical devices such as smartphones and DSLR cameras however conventional refractive lenses are large and heavy and there was limitation in that the performance decreases as the volume decreases.

The camera which is used in the smartphone uses a composite lens consisting of 8 to 9 refractive lenses. Since reducing the thickness of the composite lens is difficult there is a problem so-called katuktui which is camera coming out from the surface of smartphone.

Moreover in the case of refractive lenses used in DSLR cameras the demand for thinner and lighter lenses is very high as the minimum 500g goes over than 4kg if it is highperformance products.

In order to develop a lens with high performance and small volume the researchers studied metamaterial-based lenses. Metamaterials is a field where a lot of research is being conducted around the world because it can freely control the various light characteristics Sonic refraction and ultra-high refraction that conventional materials cannot provide. Since new optical devices such as ultra-thin flat lenses high-resolution holograms and invisibility cloaks can be implemented.

Nevertheless since electron beam lithography* which was previously used for manufacturing metamaterials has a slow process speed and is very expensive the cost of the metamaterials produced by this should be high therefore the existing metamaterial research could not escape the laboratory level.

* Electron beam lithography : Nano-processing technology that can process nanometer-level patterns by focusing an electron beam through a strong voltage.

In order to overcome these limitations The researchers succeed in developing a new nano-molding material based on nanocomposites that can be freely molded with optical properties suitable for metamaterial realization and a one-step printing technology that can be molded in a single process.

The nano molding material was produced by mixing nanoparticles with photosensitive resin. In this case the optical properties of the nano-molding material can be extensively controlled depending on the type and density of the nanoparticles which it can replace the existing material that has been mainly used for making meta-materials and the unit price of the material becomes much cheaper than the previous and becomes economically feasible.

* Photosensitivity : A substance that normally exists in a liquid state but solidify into a hard plastic when exposed to light.
In addition the one-step printing technology of the new nano-molding material can produce meta-materials at a speed of more than 100 times faster than that of previous electron beam lithography. Since metamaterials can be implemented on curved substrates and flexible substrates that are difficult to be compatible with existing process technologies it is possible to apply them to wearable devices that are receiving a lot of interest in recent years so the potential of the future development highly expected.

On the other hand the researchers developed an ultra-thin metalens with a thickness of 1 micrometer which is more than 100 times thinner than the thickness of a hair based on silicon nanocomposites and printing technology. Through this verified the practical applicability of the research outcome by combining an actual optical system to succeed in imaging.

Prof. Jun-Seok Noh explained the impact of this study by saying “Since the ultra-thin metal lens implemented in this study is 10000 times thinner than the existing infrared refractive lens with the same optical properties it will be able to solve various problems caused by large and heavy refractive lenses. It is expected to be applicable to various fields such as infrared endoscope CCTV and night vision.

[Photo provided = Ministry of Science and ICT] Photo of comparing thickness of conventional lens and meta lens

[Photo provided = Ministry of Science and ICT] Camera module manufactured by silicon nanocomposite metalens and infrared imaging result through i

[Photo provided =Ministry of Science and ICT] Jun-seok Noh Professor of Postech

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