Changhyun Kim

Metalens is one of the most prominent applications among metasurfaces since it gives possibilities to replace the conventional lenses for compactness and multi-functionalities. Recently, many studies have been demonstrated to overcome the aberrations of the metalenses for high performance practical applications. Previous studies have used the methods that control the dispersion of meta-atoms for correcting chromatic aberrations and use doublet platform for correcting monochromatic aberrations. D

-hybridized, was achieved at high temperatures (>900°C) and a controlled growth rate. We verified that the charge carriers within the Zachariasen carbon monolayer are strongly localized to display Anderson insulating behavior and a large negative magnetoresistance. This new 2D glass also exhibited a unique ability as an atom-thick interface layer, allowing the deposition of an atomically flat dielectric film. It can be adopted in conventional semiconductor and display processing or used in the f

Advances in imaging technologies have led to a high demand for ultracompact, high-resolution image sensors. However, color filter-based image sensors, now miniaturized to deep submicron pixel sizes, face challenges such as low signal-to-noise ratio due to fewer photons per pixel and inherent efficiency limitations from color filter arrays. Here, we demonstrate a freeform metasurface color router that achieves ultracompact pixel sizes while overcoming the efficiency limitations of conventional ar

Metasurface color filters (MCFs) have attracted considerable attention thanks to their compactness and functionality as a candidate of an optical element in a miniaturized image sensor. However, conventional dielectric and plasmonic MCFs that have focused on color purity and efficiency cannot avoid reflection in principle, which degrades image quality by optical flare. Here, we introduce absorptive-type MCFs through truncated-cone hyperbolic metamaterial absorbers. By applying a particle swarm o

The electrical properties of thermally grown and atomic-layer-deposition (ALD) oxides, followed by nitridation treatment, on 4H-SiC substrate were compared. The nitridation treatment was performed with post oxidation annealing in NO atmosphere (NO POA). The best electrical characteristics of the thermally grown and ALD oxides were observed at 120 and 180 min NO POA, respectively. The NO POA treated ALD oxide showed extremely low interface trap density (Dit), less than 1011 eV−1 cm−1. A metal-oxi

Sarcopenia, defined as loss of skeletal muscle mass and function with age, is an important health issue in aging society. We tried to investigate the relationship between blood pressure variability and skeletal muscle mass in nation-wide large population cohort. This cross-sectional study was based on data acquired in the Korea National Health and Nutrition Examination Survey (KNHANES), conducted from 2009 to 2011 by the Korean Centers for Disease Control and Prevention. We included 14,481 parti

Thin-film lithium niobate (TFLN) has emerged as a promising platform for integrated photonics due to its exceptional material properties. The application of freeform topology optimization to TFLN devices enables the realization of compact designs with complex functionalities and high efficiency. However, the stringent fabrication constraints of TFLN present significant challenges for optimization, particularly in nonlinear photonic devices. In this work, we propose an inverse design methodology

As an increased demand in high resolution display, the pixel size in the image sensor is reduced to increase the resolution. Although there have been recent studies on metasurface color routers to overcome the limitation of the conventional image sensor, there are still limitations in that the designed devices do not show the advantages of router or are difficult to fabricate. In this study, the fabricable metasurface that distribute three visible wavelengths to each targeted color sensor is pro

최근 M2M/IoT에 대한 관심이 높아지면서 디바이스의 위치와 자세 등을 인식할 수 있는 동작 인식 센서의 필요성이 대두되고 있다. 본 논문에서는 소형의 디바이스에 적합하도록 저잡음, 저전력, 초소형 6축 관성센서 IC를구현하였다. 본 논문에서 구현된 IC는 3축의 압전형 자이로 센서와 3축의 압저항형 가속도 센서를 사용하며, 3축의 자이로스코프 감지 회로, 자이로스코프 센서 구동 회로, 3축의 가속도 감지 회로, 16bit sigma-delta ADC, 디지털 필터와 제어 회로로 구성되어 있다. 본 IC은 TSMC 0.18µm mixed signal CMOS공정으로 개발되었으며,STM사의 6축 관성 센서인 LSM330의 소비전류 6.1mA보다는 약 27% 낮은 4.5mA의 소비 전류로 동작한다.

Most of existing research on cooperative diversity systems have assumed that the destination node and the relay node have perfect channel state information. However, it is difficult to obtain all the channel state information in the systems, especially in a multi-relay node environment. To greatly reduce the cost required for those channel estimations, a differential modulation technique can be applied to multi-node cooperative communications. However, the performance of this system can be sever

We demonstrate a multiwavelength achromatic meta-lens for red, green, and blue light based on multi-focal phase profile. The anisotropic rectangular nano-structure with silicon nitride is utilized for the meta-lens based on Pancharatnam-Berry phase technique. The proposed meta-lens has the focal length of 200 μ m at the maximum intensity and the numerical aperture of 0.67.

BACKGROUND: Influenza vaccination effectively prevents influenza-related illness and hospitalization. However, vaccination rates among Korean children and adolescents remain suboptimal. Given the strong influence of parents on their children's vaccination decisions, this study investigated the relationship between parental influenza vaccination status and their children's vaccine uptake. METHODS: We analyzed 10,674 child-parent pairs from the Korea National Health and Nutrition Examination Surve

Single-shot high dynamic range (HDR) imaging with advanced image quality for more generalized high dynamic range scenes is achieved from end-to-end optimization of a metasurface-based off-axis imaging system and a deep neural network.