Browsing by Author "Chi, Jim-Yong"

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Anisotropy of light extraction from GaN two-dimensional photonic crystals
(2008-05-12)
Lai, Chun-Feng
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Chi, Jim-Yong
;
Kuo, Hao-Chung
;
Chao, Chia-Hsin
;
Hsueh, Han-Tsung
Angular distribution of light diffracted out of the plane of two-dimensional photonic crystals ( PhC) has been studied in the azimuthal direction with a specially designed waveguide structure. The optical images of the light extraction patterns from the guided photoluminescence light are obtained with laser excitation in the center of the annual structure made on GaN multilayer. For increasing lattice constant, symmetric patterns with varying number of petals according to the symmetry of the PhC are observed. The appearance and disappearance of the petals can be explained using the Ewald construction in the reciprocal space. The dependence of light extraction on the lattice constant and orientation, and incident angle are investigated. (C) 2008 Optical Society of America.
Far-Field and Near-Field Distribution of GaN-Based Photonic Crystal LEDs With Guided Mode Extraction
(2009-07-01)
Lai, Chun-Feng
;
Chi, Jim-Yong
;
Kuo, Hao-Chung
;
Yen, Hsi-Hsuan
;
Lee, Chia-En
The near-field and far-field distribution of GaN LEDs with square photonic crystal (PhC) lattice are experimentally investigated. The optical images of the near-field pattern are obtained from the guided electroluminescent light generated at the center of a special annular structure. For increasing lattice constant, symmetric patterns with varying number of petals according to the symmetry of the PhC are observed. The far-field distribution is studied with GaN-based film-transferred PhC LEDs with the thickness about 1500 nm. Angular-resolved measurements under electrical injection revealed guided modes extraction behavior and polarization based on the Bragg's diffraction with the PhC lattice. Good agreement with the two-dimension free photon band structure is obtained.
Far-field of GaN film-transferred green light-emitting diodes with two-dimensional photonic crystals
(2009-05-25)
Lai, Chun-Feng
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Chi, Jim-Yong
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Kuo, Hao-Chung
;
Yen, Hsi-Hsuan
;
Lee, Chia-En
Far-field distributions of GaN-based photonic crystal (PhC) film-transferred light-emitting diodes (FT-LEDs) were investigated. The thickness of the device is about 840 nm. The emission wavelength is around 520 nm. The PhC region is a square lattice with a/lambda around 0.5. Angular-resolved measurements in the Gamma-X and Gamma-M directions were made in the polarized-resolved manner. Guided mode extraction behavior in agreement with the two-dimensional free-photon band calculation was observed. In addition, the pseudo-TM behavior for the non-collinearly coupled modes was observed. The azimuthal-mapping of the angular-resolved spectra revealed the evolution of the collinearly and the non-collinearly coupled modes. Furthermore, the light enhancement of similar to 2.7x and the collimation angle about 102.3 degrees were achieved. (c) 2009 Optical Society of America
GaN-based film-transferred light-emitting diodes with photonic crystal
(2009)
Lai, Chun-Feng
;
Chi, Jim-Yong
;
Chao, Chia-Hsin
;
Lee, Chia-En
;
Kuo, Hao-Chung
Experimental investigation of A-type and B-type guided modes was performed in GaN-based film-transferred photonic crystal light-emitting diodes. Good agreement with the band structure calculated in the limit of two-dimensional free photon was obtained. (C)2009 Optical Society of America
Polarized light emission from photonic crystal light-emitting diodes
(2008-06-16)
Lai, Chun-Feng
;
Chi, Jim-Yong
;
Yen, Hsi-Hsuan
;
Kuo, Hao-Chung
;
Chao, Chia-Hsin
We have experimentally studied polarization characteristics of the two-dimensional photonic crystal (PhC) light-emitting diodes (LEDs) using an annular structure with square lattice and observed a strong polarization dependence of the lattice constant and orientation of the PhC. The extracted light from the GaN PhC LEDs has P/S ratios of 5.5 (similar to 85% polarization light) for light propagating in the Gamma X direction and 2.1 (similar to 68% polarization light) for the Gamma M direction, respectively. Based on the couple mode theory, the dependence of polarization behaviors on different lattice constant and orientation was found to be in good agreement with theoretical discussion.