Browsing by Author "Wei, Ming-Dar"

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Generation of supercontinuum bottle beam using an axicon
(2007-03-19)
Lin, Ja-Hon
;
Wei, Ming-Dar
;
Liang, Hui-Hung
;
Lin, Kuei-Huei
;
Hsieh, Wen-Feng
A supercontinuum bottle beam was successfully produced by focusing a supercontinuum laser beam after passing through an axicon. The supercontinuum radiation was generated from a microstructured fiber pumped by a self-kerr-lensmode-locked femtosecond Ti: sapphire laser. The cross-section intensity distributions of the generated bottle were recorded by a beam profiler. Using the line filters to select different central wavelengths, the different colors of bottle beams show slightly different bottle ranges and diameters due to the dispersion of axicon and focusing lens. The results consist with the theoretical prediction using the Fresnel-Kirchhoff's formula in considering an incident Gaussian beam. (c) 2007 Optical Society of America.
High peak power output of a diode-pumped Q-switched and mode locked Nd : LuVO4 with Cr : YAG saturable absorber
(2007)
Lin, Ja-Hon
;
Wei, Ming-Dar
;
Hsu, Hsin-Han
;
Hsieh, Wen-Feng
;
光電工程學系
The Q-switched mode-locked (QML) pulses is demonstrated in a Nd:LuVO4 laser to generate peak power exceeding 400 kW. By the Cr:YAG with initial transmittance T-0=40%, the Q-switching envelope about 30 ns and 6.9 kHz repetition rate is produced and the pulsewidth of CW-ML pulses is about 56 ps.
Phase diagram of microcavity polariton condensates with a harmonic potential trap
(2014-01-01)
Chen, Ting-Wei
;
Wei, Ming-Dar
;
Cheng, Szu-Cheng
;
Hsieh, Wen-Feng
;
光電工程學系
We theoretically explore the phase transition in inhomogeneous exciton-polariton condensates with variable pumping conditions. Through Bogoliubov excitations to the radial-symmetric solutions of complex Gross-Pitaevskii equation, we determine not only the bifurcation of stable and unstable modes by the sign of fluid compressibility but also two distinct stable modes which are characterized by the elementary excitations and the stability of singly quantized vortex. One state is the quasi-condensate BKT phase with Goldstone flat dispersion; the other state is the localized-BEG phase which exhibits linear-type dispersion and has an excitation energy gap at zero momentum. (C) 2013 Elsevier Ltd. All rights reserved.
Stable Q-switched mode-locked Nd3+:LuVO4 laser by Cr4+:YAG crystal
(2008-10-13)
Lin, Ja-Hon
;
Chen, Hou-Ren
;
Hsu, Hsin-Han
;
Wei, Ming-Dar
;
Lin, Kuei-Huei
In use of saturable Cr4+:YAG crystals, we have demonstrated the stable Q-switched and mode-locked (QML) operation of the Nd:LuVO4 laser. The operation range of QML in use of the Cr4+:YAG is larger than that use of SESAM and NLM. The obtained shape of Q-switched envelope, repetition rate and pulse energy are demonstrated to depend on the initial transmittance of the Cr4+:YAG and reflectivity of the output coupler. Using R = 60% and T-0 = 40%, the highest pulse energy of 77 mu J of each Q-switched envelope, and the highest peak power about 200 kW of Q-switched mode-locked pulses can be obtained at 15 W pump power. It demonstrate the superior characteristic of the Nd:LuVO4 crystal. (C) 2008 Optical Society of America