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Semiconductor Photonic Nanocavities on Paper Substrates
Professor Yong-Hoon Cho of the Department of Physics and his team at KAIST have developed a semiconductor photonic nanocavity laser that can operate on a paper substrate.
The researchers hope that this novel method, which involves transferring nano-sized photonic crystal particles onto a paper substrate with high absorptiveness, will enable the diagnoses of various diseases by using high-tech semiconductor sensors at low cost.
The results of this research were published in the November 17th, 2016, issue of Advanced Materials.
Photonic crystals, which utilize light as a medium to provide high bandwidths, can transfer large amounts of information. Compared with their electronic counterparts, photonic crystals also consume less energy to operate.
Normally, semiconductor photonic particles require substrates, which play only a passive role in the assembly and endurance of individual, functional photonic components. These substrates, however, are bulky and environmentally hazardous as they are made up of non-biodegradable materials.
The research team overcame these two shortcomings by replacing a semiconductor substrate with standard paper. The substrate’s mass was reduced considerably, and because paper is made from trees, it degrades. Paper can be easily and cheaply acquired from our surroundings, which drastically reduces the unit cost of semiconductors.
In addition, paper possesses superior mechanical characteristics. It is flexible and can be repeatedly folded and unfolded without being torn. These are traits that have long been sought by researchers for existing flexible substrates.
The research team used a micro-sized stamp to detach photonic crystal nanobeam cavities selectively from their original substrate and transfer them onto a new paper substrate. Using this technique, the team removed nanophotonic crystals that had been patterned (using a process of selectively etching circuits onto a substrate) onto a semiconductor substrate with a high degree of integration, and realigned them as desired on a paper substrate.
The nanophotonic crystals that the team combined with paper in this research were 0.5 micrometers in width, 6 micrometers in length, and 0.3 micrometers in height—about one-hundredth of the width of a single hair (0.1 millimeter).
The team also transferred their photonic crystals onto paper with a fluid channel, which proved that it could be used as a refractive index sensor. As can be seen in current commercial pregnancy diagnosis kits, paper has high absorptiveness. Since photonic crystal particles have high sensitivity, they are highly suitable for applications such as sensors.
Professor Cho stated that “by using paper substrates, this technology can greatly contribute to the rising field of producing environmentally-friendly photonic particles” and “by combining inexpensive paper and high-performance photonic crystal sensors, we can obtain low prices as well as designing appropriate technologies with high performance.”
Dr. Sejeong Kim of the Department of Physics participated in this study as the first author, and Professor Kwanwoo Shin of Sogang University and Professor Yong-Hee Lee of KAIST also took part in this research. The research was supported by the National Research Foundation’s Mid-Career Researcher Program, and the Climate Change Research Hub of KAIST.
Figure 1. Illustration of photonic crystal lasers on paper substrates
Figure 2. Photonic crystal resonator laser and refractive index sensor operating on paper substrates
2017.03.01 View 7750 -
Quantum Dot Film Can Withstand High Temperatures and Humidity
The joint KAIST research team of Professor Byeong-Soo Bae of the Department of Materials Science and Engineering and Professor Doh Chang Lee of the Department of Chemical and Biomolecular Engineering was able to fabricate a siloxane-encapsulated quantum dot film, which exhibits stable emission intensity over one month even at high temperatures and humidity.
The results of this study were published in the Journal of the American Chemical Society (JACS) on November 29, 2016. The research article is entitled “Quantum Dot/Siloxane Composite Film Exceptionally Stable against Oxidation under Heat and Moisture.” (DOI: 10.1021/jacs.6b10681)
Quantum dots (QDs), light-emitting diodes (LEDs) for next-generation displays, are tiny particles or nanocrystals of semiconducting materials. Their emission wavelength can easily be adjusted by changing their sizes, which are just a few nanometers. A wide spectrum of their colors can also achieve ultra-high definition displays.
Due to these characteristics, QDs are coated on a film as a polymer resin in dispersed form, or they are spread on an LED light source. They are thus considered to be crucial for next generation displays.
Despite their exceptional optical properties, however, QDs are easily oxidized in a high temperature and high humidity environment, and, as a result, this greatly deteriorates their luminescence quality (quantum efficiency). Therefore, they are encapsulated in an extra thin layer to block oxygen and moisture.
QD displays in the current market have a film inserted to separate them from LEDs, which create heat. The high unit cost of this protective layer, however, increases the overall cost of displays, lowering their price competitiveness in the market.
For a solution, the research team applied the sol-gel condensation reaction of silane precursors with QDs. This technology uses the reactions of chemical substances to synthesize ceramics or glass at a low temperature.
The team applied QDs in a heat resistant siloxane polymer by employing this technology. The siloxane resin acted as a cup holding the QDs and also blocked heat and moisture. Thus, their performance can be maintained without an extra protective film.
QDs are evenly dispersed into the resin from a chemical process to fabricate a QD embedded film and retained the high quality luminescence not only at a high temperature of 85°C and in a high humidity of 85%, but also in a high acid and high base environment. Remarkably though, the luminescence actually increased in the high humidity environment.
If this technology is used, the overall price of displays will decrease by producing a stable QD film without an extra protective barrier. In the future, the QD film can be directly applied to a blue LED light source. As a result, it will be possible to develop a QD display that can reduce the amount of QDs needed and improve its performance.
Professor Bae said, “We have proposed a way to make quantum dots overcome their limitations and have wide applications as they are being developed for next-generation displays. Our technology will make significant contributions to the display industry in the country.”
He also added, “In the future, we plan to cooperate with companies both in and out of the country to improve the performance of quantum dots and concentrate on their commercialization.”
The research team is currently applying for related patents both in and out of the country. The team is also plan ning to transfer the patents to Sol Ip Technology Inc., a company founded at KAIST, to start the commercialization.
Picture 1:
Siloxane-encapsulated quantum dot (QD) films showing performance stability in boiling water
Picture 2 and 3:
So-gel condensation reaction in silane precursors between Methacryloxypropyltrimethoxysilane (MPTS) and diphenylsilanediol (DPSD). The inset shows photographs of a QD-oligosiloxane resin under room light (left) and a UV lamp (λ = 365 nm) (right).
Free radical addition reactions among carbon double bonds of methacryl functional groups and oleic acids. The inset shows photographs of a QD-silox film under room light (left) and a UV lamp (λ = 365 nm) (right).
2017.02.24 View 10577 -
Prof. Woo Chang Kim Is Appointed as Managing Editor of Quantitative Finance
Professor Woo Chang Kim of the Industrial and Systems Engineering Department has been elected as the Managing Editor of Quantitative Finance.
Founded in 2001, Quantitative Finance has been an internationally-acclaimed peer-reviewed journal in the field of financial engineering, along with Mathematical Finance.
This is the first time for a Korean researcher to be named for the editorial board, which consists of eminent scholars from around the world, including four Nobel laureates.
Professor Kim’s expertise lies in financial optimization, portfolio management, and asset liability management. In recent years, he has focused his research on robo-advisors in the area of FinTech, and for this contribution, he was appointed as managing editor.
Professor Kim also served as an editor, deputy editor, and a member of the editorial boards for various journals, including the Journal of Portfolio Management and Optimization and Engineering. Currently, he serves as a member of the Korean National Pension Fund’s Electoral Commission, an adviser to Samsung Asset Management Co., Ltd., and the director of the KAIST Asset Management for Future Technology Research Center that was opened in October 2016.
2017.02.23 View 8475 -
Dr. Sung-Chul Shin Selected 16th President of KAIST
(President Sung-Chul Shin)
The KAIST Board of Trustees elected Professor Sung-Chul Shin of the Department of Physics the 16th president of KAIST on February 21. Professor Shin succeeds President Sung-Mo Kang whose four-year term will end on February 23. He is the first KAIST alumnus to serve as its president.
The Board of Trustees announced, “We believe that Professor Shin’s scientific achievement, outstanding leadership, and clear vision will serve KAIST faculty, students, and staff very well. He will be the best person to help KAIST leap forward in the four years ahead.”
The newly-elected president said, “I am humbled and honored to have been elected to lead such a prestigious institute of Korea. Aiming to be one of the top ten global universities, KAIST will continue to innovate its systems.” Previously, Dr. Shin led the Daegu Gyeongbuk Institute of Science and Technology (DGIST) for six years as president since 2011.
Professor Shin joined the KAIST faculty in 1989. He graduated from Seoul National University and then earned his MS degree in condensed matter physics at KAIST in 1977. After earning his Ph.D. in material physics at Northwestern University in 1984, he worked at Eastman Kodak Research Labs as a senior research scientist for five years.
Before heading to DGIST, President Shin held key administrative positions at KAIST from the early 1990s including dean of planning, dean of the international office, and vice-dean of student affairs. During President Robert Laughlin’s tenure, the first foreign president at KAIST, he served as vice-president for two years from 2004. He also served on the Presidential Advisory Council on Science and Technology of the Korean government as vice chairperson from 2015 to 2016.
A renowned scholar in the field of nanoscience, President Shin’s research focuses on the artificial synthesis and characterization of nonmagnetic materials, magnetic anisotropy, and magneto-optical phenomena. He leads the Laboratory for Nanospinics of Spintronic Materials at KAIST and has published in 290 journals while holding 37 patents.
A fellow in the American Physical Society (APS) since 2008, he was the president of the Korean Physical Society from 2011 to 2012. He has been on the editorial board of J. Magnetism and Magnetic Materials from 2009 and was the first Korean recipient of the Asian Union of Magnetics Societies (AUMS) Award, which recognizes outstanding scientists in the field of magnetics.
President Shin envisions making KAIST’s research and education more competitive through continuing innovation. His innovation efforts will extend to the five key areas of education, research, technology commercialization, globalization, and future planning.
Among his priorities, he emphasizes multidisciplinary studies and leadership training for students. He plans to focus on undeclared major courses for undergraduates to help them expand their experience and exposure to diverse disciplines. This approach will help create well-rounded engineers, scientists, and entrepreneurs by enabling them to develop skills while leveraging a strong connection to the arts, humanities, and social sciences.
To better respond to Industry 4.0, which calls for convergence studies and collaborative work, he proposed establishing a ‘Convergence Innovation System’ by strategically selecting 10 flagship convergence research groups. In order to accelerate the technology commercialization and ecosystem of start-ups, he will strengthen entrepreneurship education, making it a prerequisite requirement for students. President Shin said he will spare no effort to incubate and spin-off ventures in which KAIST technology is being transferred. For globalization efforts, he plans to increase the ratio of foreign faculty from 9 percent to 15 percent, while doubling the current foreign student enrollment ratio of 5 percent. For future strategic innovation, he will implement a long-term innovation strategic plan dubbed ‘Vision 2031.’
2017.02.22 View 11771 -
Controlling Turtle Motion with Human Thought
KAIST researchers have developed a technology that can remotely control an animal’s movement with human thought.
In the 2009 blockbuster “Avatar,” a human remotely controls the body of an alien. It does so by injecting human intelligence into a remotely located, biological body. Although still in the realm of science fiction, researchers are nevertheless developing so-called ‘brain-computer interfaces’ (BCIs) following recent advances in electronics and computing. These technologies can ‘read’ and use human thought to control machines, for example, humanoid robots.
New research has demonstrated the possibility of combining a BCI with a device that transmits information from a computer to a brain, or known as a ‘computer-to-brain interface’ (CBI). The combination of these devices could be used to establish a functional link between the brains of different species. Now, researchers from the Korea Advanced Institute of Science and Technology (KAIST) have developed a human-turtle interaction system in which a signal originating from a human brain can affect where a turtle moves.
Unlike previous research that has tried to control animal movement by applying invasive methods, most notably in insects, Professors Phill-Seung Lee of the Mechanical Engineering Department and Sungho Jo of the Computing School propose a conceptual system that can guide an animal’s moving path by controlling its instinctive escape behavior. They chose a turtle because of its cognitive abilities as well as its ability to distinguish different wavelengths of light. Specifically, turtles can recognize a white light source as an open space and so move toward it. They also show specific avoidance behavior to things that might obstruct their view. Turtles also move toward and away from obstacles in their environment in a predictable manner. It was this instinctive, predictable behavior that the researchers induced using the BCI.
The entire human-turtle setup is as follows: A head-mounted display (HMD) is combined with a BCI to immerse the human user in the turtle’s environment. The human operator wears the BCI-HMD system, while the turtle has a 'cyborg system'—consisting of a camera, Wi-Fi transceiver, computer control module, and battery—all mounted on the turtle’s upper shell. Also included on the turtle’s shell is a black semi-cylinder with a slit, which forms the ‘stimulation device.’ This can be turned ±36 degrees via the BCI.
The entire process works like this: the human operator receives images from the camera mounted on the turtle. These real-time video images allow the human operator to decide where the turtle should move. The human provides thought commands that are recognized by the wearable BCI system as electroencephalography (EEG) signals. The BCI can distinguish between three mental states: left, right, and idle. The left and right commands activate the turtle’s stimulation device via Wi-Fi, turning it so that it obstructs the turtle’s view. This invokes its natural instinct to move toward light and change its direction. Finally, the human acquires updated visual feedback from the camera mounted on the shell and in this way continues to remotely navigate the turtle’s trajectory.
The research demonstrates that the animal guiding scheme via BCI can be used in a variety of environments with turtles moving indoors and outdoors on many different surfaces, like gravel and grass, and tackling a range of obstacles, such as shallow water and trees. This technology could be developed to integrate positioning systems and improved augmented and virtual reality techniques, enabling various applications, including devices for military reconnaissance and surveillance.
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Reference: “Remote Navigation of Turtle by Controlling Instinct Behavior via Human Brain-computer Interface,” Journal of Bionic Engineering, July 2016 (DOI: 10.1016/S1672-6529(16)60322-0)
Depiction of Cyborg System
A human controller influences the turtle’s escape behavior by sending left and right signals via Wi-Fi to a control system on the back of the turtle.
2017.02.21 View 15382 -
Professor Shin Honored Posthumously for Iridescent Microparticles
(The Late Professor Joong-Hoon Shin (left) and Professor Shin-Hyun Kim)
A research team co-led by Professor Shin-Hyun Kim from the Department of Chemical and Biomolecular Engineering and Professor Jong-Ryul Jeong from the Department of Materials Science and Engineering at Chungnam National University developed iridescent microparticles with a structural color gradient. The research team posthumously dedicated their research to a renowned professor in the field of nanophotonics, the late Professor Joong-Hoon Shin of the Graduate School of Nanoscience and Technology at KAIST. He passed away suddenly in a car accident last September.
The iridescent microparticles, which allow on-demand control over structural color, will be key components for next-generation reflection-mode displays with clear color realization even in direct sunlight.
Materials such as opals, Morpho butterfly wings, and peacock feathers all display beautiful colors without pigment, using regularly-spaced nanostructures. Regularly-spaced nanostructures render color, by selectively reflecting the light of a particular wave through light interference. As such, materials that possess periodic modulation of refractive index at subwavelength scale are referred to as photonic crystals.
In general, photonic crystals are only able to display a single color, so limitations exist when attempting to apply them to reflection-mode displays which call for multiple structural colors. The research team addressed the issue using inspiration from snowflakes stacking in the winter. When snow falls on the surface of a round-shaped structure, the thickness of the snow stacking differs depending on the orientation. Based on this observation, the research team created photonic microparticles with a structural color gradient by depositing two different materials on spherical microparticles.
When some material is deposited on the surface of a sphere, the material on the top is thickest and becomes thinner on the sides. The team alternately deposited titania and silica on the spherical microparticles to form periodic modulation of the refractive index. The thickness of the alternating photonic layers is reduced along the angle from the top, which yields a structural color gradient.
Consequently, the microparticles reflect long-wavelength red light from the top of the sphere and short-wavelength blue light from the side of the sphere. Any color of the visible spectrum can be selected in between the top and side depending on the orientation of the microparticles.
The research team used an external magnetic field as a way to control the orientation of the photonic microparticles and the structural colors. As magnetic iron layer was deposited underneath the alternating photonic layer, it was possible to freely control the orientation of the microparticles using a magnet, thereby allowing control of the color seen by the users.
KAIST doctoral candidate Seung Yeol Lee of the Department of Chemical and Biomolecular Engineering is the first author of this research, with support from the Midcareer Researcher Program of the National Research Foundation and funded by the Ministry of Science, ICT, and Future Planning (MSIP). This research was published in the online edition of Advanced Materials on February 6, 2017.
Figure1: Sets of an OM image of photonic Janus microspheres and an SEM image showing a cross-section of the photonic layers.
Figure 2: A series of schematics and OM images showing the color change depending on the orientation angle of the photonic Janus microsphere.
2017.02.17 View 8968 -
KAIST Celebrates the 2017 Commencement
KAIST hosted its 2017 Commencement, awarding diplomas to 2,767 members of the Class of 2017 during a ceremony on February 17. President Sung-Mo Kang, Minister Yang-hee Choi of Science, ICT, and Future Planning, and Chairman of the KAIST Board of Trustees Jang-Moo Lee joined the ceremony along with the graduates and their family and friends at the Ryu Keun Chul Sports Complex.
The graduating class included 638 Ph.D. degrees, 1,335 Master’s degrees, and 794 Bachelor’s degrees being conferred. Among them, Young-Ki Song from the Department of Electric Engineering was honored to win the Minister’s Award, the highest award bestowed to an undergraduate. The KAIST Presidential Award went to Min-Jae Park of the Department of Mathematical Sciences and the KAIST Board of Trustee Chairman’s Award was presented to Jae-Hyung Cho from the Department of Mechanical Engineering.
Including this year’s graduating class, KAIST has turned out more than 59,000 highly educated science and technology talents including 11,731 Ph.D.s since its foundation in 1971. This year, 24-year-old Seo-Hee Oh earned her Ph.D. in chemistry as the youngest Ph.D. of the year after completing her Master’s and Ph.D. combined course in three years.
President Sung-Mo Kang praised the creativity of this graduating class and their excellent ability in his charge, saying, “As future leaders of our society, you are expected to develop a sense of compassion and outstanding professionalism to contribute to the advancement of not only Korea but also the whole world.’
For full text of President Kang’s charge to the graduates, please click.
2017.02.17 View 9404 -
An Improved Carbon Nanotube Semiconductor
Professor Yang-Kyu Choi and his research team of the School of Electrical Engineering at KAIST collaborated with Professor Sung-Jin Choi of Kookmin University to develop a large-scale carbon nanotube semiconductor by using a 3-D fin-gate structure with carbon nanotubes on its top.
Dong Il Lee, a postdoctoral researcher at KAIST’s Electrical Engineering School, participated in this study as the first author. It was published in ACS Nano on November 10, 2016, and was entitled “Three-Dimensional Fin-Structured Semiconducting Carbon Nanotube Network Transistor.”
A semiconductor made with carbon nanotubes operates faster than a silicon semiconductor and requires less energy, yielding higher performance.
Most electronic equipment and devices, however, use silicon semiconductors because it is difficult to fabricate highly purified and densely packed semiconductors with carbon nanotubes (CNTs).
To date, the performance of CNTs was limited due to their low density. Their purity was also low, so it was impossible to make products that had a constant yield on a large-surface wafer or substrate. These characteristics made the mass production of semiconducting CNTs difficult.
To solve these difficulties, the research team used a 3-D fin-gate to vapor-deposit carbon nanotubes on its top. They developed a semiconductor that had a high current density with a width less than 50 nm.
The three-dimensional fin structure was able to vapor-deposit 600 carbon nanotubes per micrometer. This structure could have 20 times more nanotubes than the two dimensional structure, which could only vapor-deposit thirty in the same 1 micrometer width.
In addition, the research team used semi-conductive carbon nanotubes having a purity rating higher than 99.9% from a previous study to obtain a high yield semiconductor.
The semiconductor from the research group has a high current density even with a width less than 50 μm. The new semiconductor is expected to be five times faster than a silicon-based semiconductor and will require five times less electricity during operation.
Furthermore, the new semiconductor can be made by or will be compatible with the equipment for producing silicon-based semiconductors, so there will be no additional costs.
Researcher Lee said, “As a next generation semiconductor, the carbon nanotube semiconductor will have better performance, and its effectiveness will be higher.” He also added, “Hopefully, the new semiconductor will replace the silicon-based semiconductors in ten years.”
This study received support from the Center for Integrated Smart Sensors funded by the Ministry of Science, ICT & Future Planning of Korea as the Global Frontier Project, and from the CMOS (Complementary Metal-Oxide-Semiconductor) THz Technology Convergence Center of the Pioneer Research Center Program sponsored by the National Research Foundation of Korea.
Picture 1: 3D Diagram of the Carbon Nanotube Electronic Device and Its Scanning Electron Microscope (SEM) Image
Picture 2: 3D Transistor Device on an 8-inch Base and the SEM Image of Its Cross Section
2017.02.16 View 11269 -
New Building Endowed in Bio and Brain Engineering Department
An endowment from the former Chairman of Mirae Industries, Moon Soul Chung, was used to establish the Yang Bun Soon Building in the Bio and Brain Engineering Department at KAIST. The opening ceremony for the building took place on February 8 and was attended by President Sung-Mo Kang, KAIST administrators, faculty, and students.
The Yang Bun Soon Building, named after the wife of Chairman Chung, is a new addition to the Bio and Brain Engineering Department complex. The five-story building was erected next to the 11-story Chung Moon Soul Building, which was completed in 2003 using a portion of his first endowment to KAIST. Chairman Chung donated approximately 30 billion KRW for funding a convergence research for IT and BT in 2001.
The new building was completed with financing from Chung’s second endowment of 21.5 billion KRW in support of the fields of brain and cognitive sciences in 2014. The building will accommodate both lab facilities and lecture halls.
At the ceremony, President Kang thanked the Chungs for their continuing generosity to KAIST. He commended Chung for showing how entrepreneurs can fulfill their social responsibility by supporting Korea’s future through donations and support.
(Photo caption: Chung Moon Soul Building (left) and Yang Bun Soon Building(right))
2017.02.09 View 6212 -
Dr.M Drives Smart Healthcare Industry in Partnership with Hancom
President Sung-Mo Kang signed an agreement on January 25 with Hancom Group Chairman Sang Chul Kim to establish a smart healthcare complex in Gapyeong, Kyonggido. With the Gapyeong complex launch, KAIST will come to commercialize Dr. M system along with other Dr.M consortium members as a new growth engine to drive the smart health industry.
Dr. M is a smart healthcare platform developed by the Health Science Research Institute at KAIST in 2014. Dr. M is capable of analyzing and predicting diseases, as well as prescribing, by incorporating ICT and medical technologies. Dr. M applies diverse technologies such as healthcare sensors, wearable devices, low-power communications technology, and cloud and big data collection platforms.
Hancom Group, a leading computer software company in Korea, has participated in the project since 2015 for advancing the smart healthcare market by developing mobile healthcare software program. Hancom joined the Dr.M consortium launched last November.
(President Kang (left) poses with Hancom Chairman Kim after signing.)
2017.02.03 View 6928 -
A New Approach to 3D Holographic Displays Greatly Improves the Image Quality
With the addition of holographic diffusers or frosted glasses to wavefront modulators, KAIST researchers offer a simple and practical solution to significantly enhance the performance of 3D dynamic holographic displays by 2,600 times.
The potential applications of three-dimensional (3D) digital holograms are enormous. In addition to arts and entertainment, various fields including biomedical imaging, scientific visualization, engineering design, and displays could benefit from this technology. For example, creating full-sized organs for 3D analysis by doctors could be helpful, but it remained a challenge owing to the limitation of hologram-generation techniques.
A research team led by Professor YongKeun Park of the Physics Department at KAIST has come up with a solution and developed a 3D holographic display that performs more than 2,600 times better than existing 3D holographic displays. This study is expected to improve the limited size and viewing angle of 3D images, which were a major problem of the current holographic displays. The study was published online in Nature Photonics on January 23, 2017.
3D holograms, which often appear in science fiction films, are a familiar technology to the public, but holograms in movies are created with computer graphic effects. Methods for creating true 3D holograms are still being studied in the laboratory. For example, due to the difficulty of generating real 3D images, recent virtual reality (VR) and augmented reality (AR) devices project two different two-dimensional (2D) images onto a viewer to induce optical illusions.
To create a 3D hologram that can be viewed without special equipment such as 3D glasses, the wavefront of light must be controlled using wavefront modulators such as spatial light modulators (SLMs) and deformable mirrors (DMs). A wavefront modulator is an optical manipulation device that can control the direction of light propagation.
However, the biggest limitation to using these modulators as 3D displays is the number of pixels. The large number of pixels that are packed into high-resolution displays developed in recent years are suitable for a 2D image, and the amount of information contained in those pixels cannot produce a 3D image. For this reason, a 3D image that can be made with existing wavefront modulator technology is 1 cm in size with a narrow viewing angle of 3 degrees, which is far from practicable.
As an alternative, KAIST researchers used a DM and added two successive holographic diffusers to scatter light. By scattering light in many directions, this allows for a wider viewing angle and larger image, but results in volume speckle fields, which are caused by the interference of multiple scattered light. Random volume speckle fields cannot be used to display 3D images.
To fix the problem, the researchers employed a wavefront-shaping technique to control the fields. As a result, they succeeded in producing an enhanced 3D holographic image with a viewing angle of 35 degrees in a volume of 2 cm in length, width, and height. This yielded a performance that was about 2,600 times stronger than the original image definition generated when they used a DM without a diffuser.
Professor Park said, “Scattering light has previously been believed to interfere with the recognition of objects, but we have demonstrated that current 3D displays can be improved significantly with an increased viewing angle and image size by properly controlling the scattered light.”
Hyeonseung Yu, who is the lead author of this research article and a doctoral candidate in the Department of Physics, KAIST, noted that this technology signals a good start to develop a practical model for dynamic 3D hologram displays that can be enjoyed without the need for special eyeglasses. “This approach can also be applied to AR and VR technology to enhance the image resolution and viewing angles,” added Yu.
The research paper is entitled “Ultrahigh-definition Dynamic 3D Holographic Display by Active Control of Volume Speckle Fields.”
Figure 1. Concept of Scattering Display
The size and viewing angle of 3D images can be simultaneously increased when a scattering medium (diffuser) is introduced. By controlling the wavefront impinging on the scattering medium, the desired 3D hologram is generated.
Figure 2. Experimental Setup
The optical set-up consists of a deformable mirror and the scattering medium with two successive holographic diffusers. A high-numerical-aperture imaging unit mounted on a three-axis motorized translational system is utilized for wavefront optimization and imaging.
Figure 3. 3D Images Projected
This picture shows 3D images in a volume of 2 cm × 2 cm × 2 cm with a viewing angle of 35 degrees using one of the wavefront modulators, a digital micromirror device (DMD).
Figure 4. Artist’s Rendition of the Proposed Concept
A dynamic 3D hologram of a face is displayed.
2017.02.01 View 13881 -
KAIST Intensive Science Camp for Middle-High School Students
The KAIST Global Institute of Talented Education (Director: Dong-Soo Kwon) invited around 90 middle and high school students for an advanced science intensive camp from January 22 to 24.
This camp targeted middle and high school students in community centers or child-care institutions. It aims to increase students’ interest in science and engineering, and assist them with their career paths through programs such as special lectures on science, advanced science projects, and career mentoring.
Participating students were divided into groups of seven or eight with a KAIST student as a mentor to conduct advanced science projects such as VR controller production and robot arm programming. The camp included exploring future career options and science and engineering college admission counselling.
Jiyoung Ryu, Research Professor for the KAIST Global Institute of Talented Education, said, “KAIST started the science and engineering career experience program in 2016 with the Ministry of Education and Korea Research Institute for Vocational Education and Training (KRIVET). So far, 6000 middle and high school students from around the country have participated. The camp is more meaningful since it educates students in social responsibility, in addition to the fields of science and engineering, both of which are missions and goals that KAIST strives for.” She continued to say, “We plan to continue to expand the program in the future.”
The KAIST Global Institute of Talented Education is actively conducting research and projects on national education for talented youth such as policy research concerning gifted education, science and engineering career education, advanced science camps, training for gifted education teachers, and cyber gifted education programs.
2017.02.01 View 8591