Ultrahigh Optical Nonlinearity Observed in an MXene
Professor Kim Myung-ki’s group published the results in Advanced Materials

▲ (From left) Dr. Park Chang-hoon (first author), Park Nu-ri (first author), Professor Kim Myung-ki (corresponding author), and Professor Koo Chong-min (corresponding author, Sungkyunkwan University)

A collaborative research team led by Professor Kim Myung-ki from the KU-KIST Graduate School of Converging Science and Technology and Professor Koo Chong-min from the School of Advanced Materials Science & Engineering at Sungkyunkwan University successfully observed the highest reported level of nonlinear responses within a communication wavelength range from the plasmons of an MXene, which is an emerging type of 2D metallic material.

The results were published online in Advanced Materials (IF=29.4), one of the top journals in the field, on March 26.
- Title of article : Ultrahigh nonlinear responses from MXene plasmons in the short-wave infrared range
- Article URL : https://onlinelibrary.wiley.com/doi/10.1002/adma.202309189

MXenes, a group of artificially synthesized 2D materials, have recently drawn significant attention due to their unique physical and chemical properties. These materials exhibit excellent conductivity, mechanical strength, and flexibility, in conjunction with excellent catalytic activity due to their wide surface area. In particular, because their chemical composition and structure can be easily controlled, the chemical and physical properties of MXenes can be finely tuned. Due to these characteristics, MXenes demonstrate great potential as next-generation materials for use in energy storage, sensors, electronic devices, environmental engineering, and biomedical technology.

The physicochemical uniqueness of MXenes has been expected to produce excellent nonlinear optical properties when interacting with electromagnetic waves in the high-frequency bandwidth. Because these properties are core requirements for the development of next-generation communication devices that rely on high-speed data transmission and efficient signal processing, such as those based on artificial intelligence (AI) and machine learning (ML), novel 2D materials such as MXenes are drawing much attention as a means to resolve these issues. However, ultrathin MXenes have a low interaction with external light due to their physical properties, making it difficult to directly observe any uniquely high optical nonlinearity.

The research team employed an MXene-based plasmon nano-antenna to strongly confine short-wave infrared (SWIR) light in a 5 nm-thick ultrathin MXene sample. By doing so, they successfully observed the ultrahigh optical nonlinearity of MXene directly. This was possible because the researchers implemented the world’s first acoustic MXene plasmons capable of maximizing the plasmon effect of an MXene. The 5 nm-thick MXene had a nonlinear absorption coefficient of 1.37 × 10-2 m W-1 at a wavelength of 1.56 µm, which is in the communication frequency bandwidth. This value was more than 1,000 times higher than the highest value recorded for other 2D materials.

Professor Kim Myung-ki from the KU-KIST Graduate School of Converging Science and Technology said of this achievement, “Through this study, we confirmed the potential of MXene as a next-generation core optical material that can overcome the performance limitation of optical communication devices. Innovative novel materials such as MXenes will become the core elements of advanced next-generation communication technologies that require a high speed, a high capacity, and a high efficiency.” Professor Kim also said, “We look forward to seeing MXenes play a critical role in not only optical communication but also other areas of optics, including optical sensors, solar cells, and light obscuration.”

<Figure 1>

(Left) Schematic of ultrahigh optical nonlinear signal generation using MXene plasmons. 

(Right) Transmission electron microscopy image of the prepared MXene.

<Figure 2>

(Left) Results of a simulation showing high light confinement within the MXene at a communication wavelength using the MXene plasmon nano-antenna. (Right) Transmission electron microscopy image of the fabricated MXene plasmon nano-antenna.

<Figure 3>

(Left) Comparison of the nonlinear absorption coefficient in the SWIR region between the MXene and other 2D materials. (Right) Nonlinear characteristics of the MXene at a communication wavelength measured using Z-scan measurements.