Browsing by Author "Kuo, Ming-Yen"

Now showing 1 - 6 of 6

Large Area of Ultraviolet GaN-Based Photonic Quasicrystal Laser
(2012-04-01)
Chen, Cheng-Chang
;
Chiu, Ching-Hsueh
;
Tu, Po-Min
;
Kuo, Ming-Yen
;
Shih, M. H.
In this study, large-area GaN-based photonic quasicrystal (PQC) nanopillars were fabricated on an n-GaN substrate using the nanoimprint lithography (NIL) technique. Under optical pumping condition, a high lasing action from the GaN photonic quasicrystals was observed. The lasing wavelength is at 366nm with a low threshold power density of 0.009 kW/cm(2). To confirm the band-edge lasing mode, the finite-element method (FEM) was used to perform the simulation for the 12-fold symmetry photonic quasicrystal lattices. (C) 2012 The Japan Society of Applied Physics
Large-area ultraviolet GaN-based photonic quasicrystal laser with high-efficiency green color emission of semipolar {10-11} In0.3Ga0.7N/GaN multiple quantum wells
(2013-01-07)
Chen, Cheng-Chang
;
Chiu, Ching-Hsueh
;
Chang, Shih-Pang
;
Shih, M. H.
;
Kuo, Ming-Yen
In this study, a multi-color emission was observed from the large-area GaN-based photonic quasicrystal (PQC) nanopillar laser. The GaN PQC nanostructure was fabricated on an n-GaN layer by using nanoimprint lithographic technology. The regrown InGaN/GaN multiple quantum wells (MQWs) formed a nanopyramid structure on top of the PQC nanopillars. A lasing action was observed at ultraviolet wavelengths with a low threshold power density of 24 mJ/cm(2), and a green color emission from InGaN/GaN MQWs was also achieved simultaneously. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4775373]
Lasing in metal-coated GaN nanostripe at room temperature
(2011-03-28)
Wang, Yow-Gwo
;
Chen, Cheng-Chang
;
Chiu, Ching-Hsueh
;
Kuo, Ming-Yen
;
Shih, M. H.
This study demonstrated a metal-coated GaN nanostripe laser operable at room temperature. The ultraviolet lasing mode was observed at a wavelength of approximately 370 nm with a low threshold power density of 0.042 kW/cm(2). The lasing mode of the metal-coated nanostripe was characterized using finite-element method simulation. The results showed the significance of metal coatings in this nanocavity structure for lasing at room temperature. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3572023]
Room temperature lasing with high group index in metal-coated GaN nanoring
(2011-12-19)
Wang, Yow-Gwo
;
Chang, Shu-Wei
;
Chen, Cheng-Chang
;
Chiu, Ching-Hsueh
;
Kuo, Ming-Yen
The room temperature lasing action from a metal-coated GaN nanoring cavity was observed by optical pumping. The GaN nanoring is 7 mu m in diameter and 400 nm in width. The quality factor of the cavity is approximately 860 with a threshold power density of 37.5 mJ/cm(2). Such a device performance was attributed to the combination of metal-coated nanocavity with whispering-gallery modes. Moreover, the group index extracted from the experiment was 5.99 and was verified with calculations and analyses of the lasing modes as well as their characteristics. The study showed a promising way to further improve the performance of metal-coated nanolasers. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3671648]
The Influence of the Thermal Effect on CdSe/ZnS Quantum Dots in Light-Emitting Diodes
(2012-07-15)
Chen, Kuo-Ju
;
Chen, Hsin-Chu
;
Shih, Min-Hsiung
;
Wang, Chao-Hsun
;
Kuo, Ming-Yen
This study investigates the effect of temperature on CdSe/ZnS quantum dots (QDs) in GaN-based light-emitting diodes (LEDs) using the phosphor conversion efficiency (PCE) and LED junction temperature. In our simulation, the blue chip and CdSe/ZnS QDs temperature are similar because of their minimal thickness. Furthermore, to verify the effect of temperature on CdSe/ZnS QDs, we use continuous wave and pulsed current sources to measure the relationship between the temperature and relative PCE. Higher junction temperatures are observed with greater CdSe/ZnS QD volume in LEDs. This is attributed to the thermal conduction and nonradiative energy between CdSe/ZnS QDs and blue chip. Therefore, if thermal management is improved, CdSe/ZnS QDs are expected to be used as color converting material in LEDs.
Wavelength Fine-tuning Flexible Photonic Crystal Rods Laser
(2012-01-01)
Lai, Kun-Ting
;
Kuo, Ming-Yen
;
Hsu, Kung-Shu
;
Lin, Chun-Ting
;
Shih, Min-Hsiung
In this study, a flexible photonic crystal laser was demonstrated with InGaAsP nano rods on a polydimethylsiloxane (PDMS) substrate. The InGaAsP nano-rods content 4 quantum wells which are designed for 1.55 mu m communication wavelength. The lasing action was observed around 1550nm which is a band-edge emission at high-symmetry Gamma-point of photonic crystals. One of advantages of the flexible laser is the fine-tuning of optical properties by manipulating its geometry. In this work, we observed the lasing wavelength can be controlled by increasing photonic crystal lattice extension. The lasing wavelength was linearly red-shift up to 6 nm as the lattice extension percentage increased to 2.2%. The wavelength tuning rate is approximately 2.69 nm for 1 % lattice extension. Those geometric fine-tuning properties indicate the flexible photonic crystal laser can be applied as a compact tunable light source in photonic crystal integrated circuits or biomedical sensors.