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Excitation Wavelength Dependence of Terahertz Radiation from InAs: UV versus IR
Hoonill Jeong,Jihoon Jeong,G. Hugh Song,조영달 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.56 No.1
Terahertz (THz) radiation measurements from p-doped InAs (carrier density:~7 × 1017 cm−3)surfaces were carried out encompassing both IR (770–830 nm) and UV (360–385 nm) excitations by employing two synchronized femtosecond lasers. Each laser was independently tunable, and the jitter was controlled below the pulse width (~150 fs). One laser was used for THz generation,and the other for detection via a photoconductive antenna. For the IR-pulse excitation, two frequency components were observed, between which the higher-side peak disappeared as we tuned the excitation wavelength toward the UV range.
Terahertz Emission from Nanophononic Heterostructures: the Nexus Between Scale and Origin
Hoonill Jeong,Jihoon Jeong,조영달,Eunsoon Oh,Dai-Sik Kim,Christopher J. Stanton 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.56 No.1
Newly found mechanisms of terahertz (THz) radiation via acoustic standing waves and piezoelectric fields in GaN-based strained heterostructures are discussed in terms of the relevant layer thickness. Two sample structures, with quantum well widths smaller (S1) or larger (S2) than the quasi-two-dimensional exciton Bohr radius, were investigated with increasing excitation energy. For comparative purposes, the differential reflectivity spectra (DRS) were also measured, and the signal strengths were proportional to the phase-space filling effect of quantum well carriers. The signal trace versus excitation energy in THz radiation compared to the DRS reveals that the radiation is closely related with the AlGaN/GaN interface (S1) and quantum wells (S2).
플라스틱 광섬유 표면 입사 현상을 이용한 아크플래시 검출 광센서
정훈일 ( Hoonil Jeong ),김명진 ( Myoung Jin Kim ),김영호 ( Young Ho Kim ),김영웅 ( Youngwoong Kim ),노병섭 ( Byung Sup Rho ) 한국센서학회 2016 센서학회지 Vol.25 No.3
In this work, a loop sensor for Arc-Flash detections has been developed in order to trip a circuit breaker within 2.5 ms after an Arc-Flash event. For an efficient capturing of the flash light, plastic optical fibers, where light attenuations are larger than those in silicabased ones, with different diameters and surface conditions were utilized. The performance was comparatively analyzed with those of a point sensor and a commercialized product. The point sensor module was designed for hemisphere-like capturings of Arc-Flashes larger than 3 kA at 2 meters from the sensor. On the other hand, the loop sensor allowed 360-degree-detections around the fiber axis and the measurement range was dependent on the length of the fiber connected to the sensor module. The trip-level-dependent brightness measurement results showed that the fabricated point sensor and loop sensor satisfied a brightness condition, 10~40 klux, and the responses of the system to Arc-Flashes were completed within 2.5 ms.