Browsing by Author "Kuo, Chung-Chiu"

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Resonance-enhanced dipolar interaction between terahertz photons and confined acoustic phonons in nanocrystals
(2008-03-03)
Liu, Tzu-Ming
;
Lu, Ja-Yu
;
Chen, Hung-Ping
;
Kuo, Chung-Chiu
;
Yang, Meng-Ju
Taking advantage of the specific core-shell charge separation structure in the CdSe/CdTe core-shell type-II nanocrystals, we experimentally observed and verified the existence of the resonance-enhanced dipolar interaction between terahertz photons and their corresponding confined acoustic phonons. From the measured terahertz transmission spectra, we found that the photon frequency of the terahertz resonant absorption is inversely proportional to the diameter D of the nanocrystals and agrees with that of dipolar active l=1, n=0 confined acoustic modes. The corresponding absorption cross section shows a D(4) dependence, supporting a charged simple-harmonic-oscillator model. These facts verify the occurrence of dipolar interaction between terahertz photons and confined terahertz acoustic phonons. (c) 2008 American Institute of Physics.
Resonant-Enhanced Dipolar Interaction between THz-Photons and Confined Acoustic Phonons in Nanocrystals
(2008)
Liu, Tzu-Ming
;
Lu, Ja-Yu
;
Chen, Hung-Ping
;
Kuo, Chung-Chiu
;
Lai, Chih-Wei
We proved the existence of resonant-enhanced dipolar interaction between THz-photons and confined acoustic phonons in nanocrystals. By a specific core-shell charge separation, the dipolar (l=1) confined acoustic modes was activated to absorb THz waves. (C) 2007 Optical Society of America
Resonant-enhanced dipolar interaction between THz-photons and confined acoustic phonons in nanostructures
(2008-01-01)
Liu, Tzu-Ming
;
Lu, Ja-Yu
;
Kuo, Chung-Chiu
;
Yang, Meng-Ju
;
Lai, Chih-Wei
By using a frequency-controlled narrow band THz source, a Fourier Transform Infrared (FTIR) spectroscopy system, and a frequency-controlled terahertz (THz) emitter, for the first time, we studied the THz photon absorption related to the THz confined acoustic vibrations in semiconductor nanocrystals. Through a specific charge separation in the CdSe/CdTe type-II nanocrystals and a piezoelectric coupling in the wurtzite CdSe nanocrystals, the THz photons can be resonantly coupled with (l=1) dipolar modes and the (l=0) breathing modes, respectively. Our results provide new mechanisms for low dimensional systems to convert a THz photon into a phonon of the same frequency.
Terahertz scanning imaging with a subwavelength plastic fiber
(2008-02-25)
Lu, Ja-Yu
;
Chiu, Chui-Min
;
Kuo, Chung-Chiu
;
Lai, Chih-Hsien
;
Chang, Hung-Chung
The feasibility to perform terahertz imaging utilizing a terahertz subwavelength plastic fiber is investigated. Dour study shows that, With a low (<1%) fractional power inside the fiber score, the bending loss of the terahertz subwavelength fiber is acceptable to enable large area scanning without seriously sacrificing the signal-to-noise ratio of the acquired image. With a transmission geometry, this feasibility is demonstrated by direct two-dimensional scanning of the terahertz subwavelength fiber output end to image different biological samples and concealed substances. (C) 2008 American Institute of Physics.
THz interferometric imaging using subwavelength plastic fiber based THz endoscopes
(2008-02-18)
Lu, Ja-Yu
;
Kuo, Chung-Chiu
;
Chiu, Chui-Min
;
Chen, Hung-Wen
;
Hwang, Yuh-Jing
We demonstrate a new reflective imaging technique using continuous-wave THz fiber-endoscopy, in which the sample is placed behind the output of a THz subwavelength plastic fiber and the Fabry Perot interference is formed therein. 3D THz reflective images with a reasonable SNR as well as high lateral and subwavelength axial resolutions are acquired by moving the sample along the axial (z) direction and by 2D scanning the output end of the subwavelength plastic fiber without any focusing medium. By analyzing the axial-position dependent THz signals backward collected by the subwavelength plastic fiber, the THz reflection amplitudes and phases on the sample surface can be successfully reconstructed. (C) 2008 Optical Society of America.
THz interferometric imaging using subwavelength plastic fiber based THz endoscopes
(2008-01-01)
Lu, Ja-Yu
;
Kuo, Chung-Chiu
;
Chiu, Chui-Min
;
Chen, Hung-Wen
;
Pan, Ci-Ling
We demonstrate a continuous-wave THz fiber-endoscopy by utilizing low-loss THz subwavelength plastic fibers. The reconstructed 3D images not only reflect the depth variation of the object surface, but also reveal the molecular distribution of samples. (C) 2008 Optical Society of America