Awakening The Echo Of The Atomic Layer To Discover A New And Brighter Light... A High Efficiency Light Conversion Mechanism

DGIST joint research team, the tungsten selenide (WSe2) efficient light conversion mechanism, double resonance sum-frequency generation method "found in the expected development of various optical techniques, such as quantum computing, and optical communication, nonlinear optical microscopy analysis

Researchers in Korea have discovered a light wavelength conversion mechanism capable of generating brighter and more diverse lights with high efficiency. It is expected that various optical technologies such as quantum computing and nonlinear optical microscopy, including the optical communication field, will take a leap forward.

DGIST is a research team of Professor Jae-Dong Lee of the Department of New Materials Science and Dr. Hyun-Min Kim of the Department of Bio-Convergence Research. It was revealed on the 8th (Wed) that it was first discovered.

Human civilization has developed through efforts to deal with light. Various light generation and conversion technologies are being used from modern industrial science and technology to future high-tech fields such as optical communication, optical medicine, and optical energy.

Light energy has various frequencies that vibrate, and light research using the frequency of semiconductor materials using the principle of light is ongoing in various angles. The semiconductor is a material capable of controlling the electrical conductivity, and the intervening band 1) and the conducting band 2) in which electrons exist are interposed between energy prohibition zones in which electrons cannot exist . When a light pulse, which is a light of a specific frequency, enters the energy band, resonance occurs in which the vibration width of energy rapidly increases. At this time, electrons move actively through the energy ban, generating new current or light. Research is being conducted to improve the color conversion efficiency of light by adjusting the resonance of the energy band, but it is generally difficult due to low efficiency.

The DGIST research team focused on the characteristics of tungsten selenide (WSe2), a two-dimensional material that is in the spotlight as a next-generation semiconductor material, responding to visible light, and has high light absorption and multiple resonance frequencies. The team confirmed that two more powerful resonances occurred simultaneously by adjusting the two light pulses incident on tungsten selenide to the same output. Through this, it was confirmed that the light pulse of the maximized high power was emitted along with the color conversion. This achievement has the potential to be used in various optical technologies because the wavelength of light can be easily amplified more than 20 times using two resonances compared to the conventional method using single resonance.

Professor Jae-dong Lee of DGIST, a new material science major, said, "We have found out that it is easy to amplify light output and convert color of light with high efficiency in two-dimensional materials." Dr. Hyun-Min Kim of the Bio-Convergence Research Department said, “This achievement will be a cornerstone for new research such as the development of high-dimensional optical transformation technology and optical communication platform because it can be applied to more diverse materials.”

Dr. Young-Jae Kim of the DGIST Institute for New Materials Science participated as the first author, and was published in the online edition of the international journal'Nano Letters' on the 18th of May.

The two-dimensional single-layer hexagonal double-lattice semiconductor material iselenium tungsten (WSe2) has a semiconductor band structure, and there are four high light-absorption resonances between A and B and conduction bands. We can choose to have one of the two incident optical pulses in the single-layer WSe2, A resonance (740 nm), and the two incident optical pulses to produce D resonance (432 nm) with sum frequency generation, so that it can be chosen to produce the strongest resonance. This study proposes an optical sum frequency generation mechanism.

The dual resonance sum frequency generation in this study has a resonance intensity that is 20 times higher than the conventional method (second harmonic generation) when the two incident optical pulses have the same output (1.4*10^(10) W/m^2). It was confirmed that it could appear. Furthermore, it was confirmed that the double resonance sum frequency generation in WSe2 shows an output of about 10 times higher than the tungsten disulfide (WS2) under the same conditions. DOI 10.1021/acs.nanolett.0c01363