Browsing by Author "Cheng, Y. J."

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Broad Angular and Spectral Anti-Reflection Employing GaN Nano-Pillar Structures
(2008)
Chiu, C. H.
;
Yu, Peichen
;
Chen, C. C.
;
Kuo, H. C.
;
Lu, T. C.
Angular and spectral reflectivities of GaN nano-pillar structures are investigated for heights of 350nm, 550nm and 720 nm. Calculations based on rigorous coupled-wave analysis show excellent agreement with the measured reflectivities for s- and p-polarizations. (c) 2008 Optical Society of America
Broadband and omnidirectional antireflection employing disordered GaN nanopillars
(2008-06-09)
Chiu, C. H.
;
Yu, Peichen
;
Kuo, H. C.
;
Chen, C. C.
;
Lu, T. C.
Disordered GaN nanopillars of three different heights: 300, 550, and 720 nm are fabricated, and demonstrate broad angular and spectral anti-reflective characteristics, up to an incident angle of 60 degrees and for the wavelength range lambda=300-1800nm. An algorithm based on a rigorous coupled-wave analysis (RCWA) method is developed to investigate the correlations between the reflective characteristics and the structural properties of the nanopillars. The broadband and omnidirectional antireflection arises mainly from the refractive-index gradient provided by nanopillars. Calculations show excellent agreement with the measured reflectivities for both s- and p-polarizations. (c) 2008 Optical Society of America.
Fabrication of aligned single wall carbon nanotube absorbers for high power passive mode-locked Nd:GdVO(4) laser
(2012-01-01)
Cheng, S. Y.
;
Wang, Y. G.
;
Yu, P.
;
Cheng, Y. J.
;
Tang, J.
Using the vertical evaporation technique we fabricated saturable absorbers by transferring the water-soluble single wall carbon nanotubes (SWCNT) onto a hydrophilic quartz substrate. The fast recovery times of the absorber were measured to be 136 and 790 fs. The modulation depth of the absorber was about 2%. Passive mode-locked Nd:GdVO(4) laser using such an absorber was demonstrated. The continuous wave mode-locked pulses with the pulse duration of 12.4 ps and the repetition of 120 MHz were achieved. The maximum average output power of the mode-locked laser is 2.4 W at the pump power of 13 W. Such kind of absorber has potential to be put into practical use for high power solid-state laser mode locking.
Fabrication of aligned single wall carbon nanotube absorbers for high power passive mode-locked Nd:GdVO4 laser
(2012-01-01)
Cheng, S. Y.
;
Wang, Y. G.
;
Yu, P.
;
Cheng, Y. J.
;
Tang, J.
Using the vertical evaporation technique we fabricated saturable absorbers by transferring the water-soluble single wall carbon nanotubes (SWCNT) onto a hydrophilic quartz substrate. The fast recovery times of the absorber were measured to be 136 and 790 fs. The modulation depth of the absorber was about 2%. Passive mode-locked Nd:GdVO4 laser using such an absorber was demonstrated. The continuous wave mode-locked pulses with the pulse duration of 12.4 ps and the repetition of 120 MHz were achieved. The maximum average output power of the mode-locked laser is 2.4 W at the pump power of 13 W. Such kind of absorber has potential to be put into practical use for high power solid-state laser mode locking.
High efficiency light emitting diode with anisotropically etched GaN-sapphire interface
(2009-07-27)
Lo, M. H.
;
Tu, P. M.
;
Wang, C. H.
;
Hung, C. W.
;
Hsu, S. C.
We report the fabrication and study of high efficiency ultraviolet light emitting diodes with inverted micropyramid structures at GaN-sapphire interface. The micropyramid structures were created by anisotropic chemical wet etching. The pyramid structures have significantly enhanced the light output efficiency and at the same time also improved the crystal quality by partially relieving the strain and reducing the dislocation defects in GaN. The electroluminescent output power at normal direction was enhanced by 120% at 20 mA injection current and the output power integrated over all directions was enhanced by 85% compared to a reference sample.
Performance analysis of free space optical communication traffic integrated with passive optical network
(2018-10-18)
Yeh, C. H.
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Chow, C. W.
;
Gu, C. S.
;
Guo, B. S.
;
Cheng, Y. J.
In this Letter, a hybrid 10 Gbit/s on-off keying free space optics and passive optical network (FSO-PON) system is proposed and demonstrated. The experimental received sensitivities are -18 and -20 dBm at the back to back (BtB) and after 25 km fibre transmission, respectively, with 5 m free space traffic link. In the proposed analysis, FSO-PON system can support 32 and 16; and 8 and 4 remote optical wireless units for free space communication at BtB and after 25 km fibre link, respectively, when the free space transmission lengths are 150 and 300 m.
Study on GaN micro-rod growth by nature patterned sapphire substrate
(2009)
Hsu, S. C.
;
Tu, P. M.
;
Chen, I. R.
;
Cheng, Y. J.
;
光電工程學系
In this study, we Investigated the kinetics and etched morphology on sapphire substrate by mixing acid solutions We developed different etching conditions to produce various etching morphology patterns on sapphire surface Then, GaN micro-rod embedded with quantum wells (QWs) were grown on the patterned sapphire surface The cathode luminescence (CL) images of these QW embedded micro-rods have shown great crystal quality.