Changmin Lee

We demonstrate high-speed data transmission with a commercial high power GaN laser diode at 450 nm. 2.6 GHz bandwidth was achieved at an injection current of 500 mA using a high-speed visible light communication setup. Record high 4 Gbps free-space data transmission rate was achieved at room temperature.

We demonstrate data transmission of unfiltered white light generated by direct modulation of a blue gallium nitride (GaN) laser diode (LD) exciting YAG:Ce phosphors. 1.1 GHz of modulation bandwidth was measured without a limitation from the slow 3.8 MHz phosphor response. A high data transmission rate of 2 Gbit/s was achieved without an optical blue-filter using a non-return-to-zero on-off keying (NRZ-OOK) modulation scheme. The measured bit error rate (BER) of 3.50 × 10(-3) was less than the fo

Data communication based on white light generated using a near-ultraviolet (NUV) laser diode (LD) pumping red-, green-, and blue-emitting (RGB) phosphors was demonstrated for the first time. A III-nitride laser diode (LD) on a semipolar (2021¯) substrate emitting at 410 nm was used for the transmitter. The measured modulation bandwidth of the LD was 1 GHz, which was limited by the avalanche photodetector. The emission from the NUV LD and the RGB phosphor combination measured a color rendering in

We report the first demonstration of III–nitride vertical-cavity surface-emitting lasers (VCSELs) with tunnel junction (TJ) intracavity contacts grown completely by metal–organic chemical vapor deposition (MOCVD). For the TJs, n++-GaN was grown on in-situ activated p++-GaN after buffered HF surface treatment. The electrical properties and epitaxial morphologies of the TJs were first investigated on TJ LED test samples. A VCSEL with a TJ intracavity contact showed a lasing wavelength of 408 nm, a

Wedemonstrate a high-speed light fidelity (LiFi) communication system deploying ultra-high brightness laser-based white light illumination sources in a surface mount device (SMD) packaging platform. The LiFi transmitter SMD source provides 450 lumens of white light output with a brightness of 1000 cd/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> in a dual wavelength configuration comprising blue and infrared (IR) emitting laser diodes w

The dynamic characteristics of III-nitride multi-quantum well laser diodes (LDs) emitting at 410 nm were investigated. LDs were grown on semipolar (202¯1¯) bulk GaN substrates and fabricated into devices with cavity lengths ranging from 900 nm to 1800 nm. A 3-dB bandwidth of 5 GHz and 5 Gbit/s direct modulation with on-off keying were demonstrated, which were limited by the bandwidth of the photodetector used for the measurements. The differential gain of the LDs was determined to be 2.5 ± 0.5 ×

In this paper, we design a THz CMOS on-chip patch antenna with defected ground structure (DGS) and utilize it to implement a broadband and high gain on-chip antenna array. It is verified from the simulation that the DGS not only can increase the gain and bandwidth of the antenna element, but also can increase the isolation between the antenna elements in the on-chip array. Therefore, it allows the design of the compact 1 × 2 and 2 × 2 on-chip antenna array with high gain and broad bandwidth. The

We demonstrate high-speed LiFi data communication of over 20 Gbit/s using visible light from a laser-based white light emitting surface mount device (SMD) product platform that offers 10-100X the brightness of conventional LED sources. Equipped with high power blue laser diodes that offer over 3.5 GHz of 3 dB bandwidth, the laser-based white light SMD modules exhibited a signal-to-noise ratio (SNR) above 15 dB up to 1 GHz. The high SNR was combined with high order quadrature amplitude modulation

We report the high-speed performance of semipolar GaN ridge laser diodes at 410 nm and the dynamic characteristics including differential gain, damping, and the intrinsic maximum bandwidth. To the best of our knowledge, the achieved modulation bandwidth of 6.8 GHz is the highest reported value in the blue-violet spectrum. The calculated differential gain of ~3 x 10^-16 cm², which is a critical factor in high-speed modulation, proved theoretical predictions of higher gain in

Gallium Nitride (GaN) based light emitting diodes (LEDs) has been considered as a next generation lighting source due to its high efficiency, long lifetime, and high brightness. In addition to the lighting purpose, visible light communication (VLC) on LEDs has been studied since it is easily available in the existing light infrastructure. Exponentially increasing wireless data traffic in radio frequency (RF) also motivated the need for VLC. However, the modulation bandwidth of LEDs with a long c

This paper presents a wideband active detector to scan the mobile WiMAX(㎽iMAX) service area when a ㎽iMAX+cellular DBDM terminal is out of the ㎽iMAX coverage. The device, which consists of a wideband LNA and an envelope detector to minimize the power consumption for the scanning of signal existence, is designed to detect 10㎒ of ㎽iMAX signal at 2.35㎓ with the gain of 10~11㏈. Measurement result shows 30~60㎽ of power consumption over the input power of - 50 ㏈m~ 0 ㏈m, which is significantly lower pow

III-nitride light emitting diodes (LEDs) have been used for many applications covering the spectrum of ultraviolet (UV) to visible light (VL). Despite of significant improvements on solid-state lighting, LEDs still suffer significant efficiency loss at high carrier density, commonly referred as "efficiency droop" [1]. However, compared to LEDs, laser diodes (LDs) have higher power per chip and the absence of efficiency droop above lasing threshold. In addition to the advantage of solid-state lig

기존 논의에서 김영랑 시의 요체는 ‘마음’의 표상에 있다고 지적되거니와 이는 조사론(措辭論)와 의미론와 구조론의 차원에서 두루 타당하게 인정되는 일반적인 사실이다. 기본 구도에 있어서나 주제 내용에 있어서나 미적 의식에 있어서나 마음에 대한 관심은 시작의 기본 동력을 이룬다. 그런데 그의 시에서 마음은 대부분 문맥에 함축된 의미소가 아니라 문면에 기록된 어휘소로 존재한다. 본고의 취지는 김영랑 시에 언급된 ‘마음’의 내포를 명확히 규정하고, 그것이 전체로서의 작품 세계에서 어떤 의의를 지니는지를 추론하는 데 있다. 논증의 결과를 요약컨대, 그의 시에 기재된 ‘마음’이란 어사의 내포는 작품 세계를 구성하는 세 국면이라 할 기본 구도와 주제 내용과 미적 의식의 차원에서 모두 이원적으로 분할되는 것으로 판단되는바 이들은 전부 여섯 가지로 정리된다. ㆍ기본 구도: 신체적 감각－사변적 정신 ㆍ주제 내용: 감각적 본능－이념적 의지 ㆍ미적 의식: 심미적 감성－주관적 의식 이 같은 내포 구분은

Purpose: The purpose of this study is to suggest a treatment strategy for stage IV gastric cancer by investigating the behavioral difference between initially and recurrent metastatic disease. Methods: We reviewed the medical records of the patients who underwent chemotherapy alone for metastatic gastric cancer between January 2006 and September 2013. Patients were divided into those who underwent chemotherapy for metastatic disease since initial diagnosis (IM group) and for metastatic recurrenc

이장희 시를 낭만성과 환상성의 관점에서 검토했다. 논의를 종합컨대, 양자는 전작의 동적 체계를 구성하는 핵심적인 의미 요인으로 판단된다. 이장희 시의 기본 구도는 ‘사회와 분열된 개인의 낭만적 정념과 환상적 동경’이라 기술할 수 있다. 실제 작품에서 낭만성은 과거 지향과 신성 추구로 발현되고, 환상성은 욕망 표출과 언어 유희로 구현된다.