Browsing by Author "Lu, Ja-Yu"

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A terahertz plastic wire based evanescent field sensor for high sensitivity liquid detection
(2010)
You, Borwen
;
Lu, Ja-Yu
;
Pan, Ci-Ling
;
Liu, Tze-An
;
Peng, Jin-Long
A highly sensitive detection method based on the evanescent wave of a terahertz subwavelength plastic wire was demonstrated for liquid sensing. A 20ppm melamine alcohol solution is successfully identified with refractive-index sensitivity of 0.01. (C)2010 Optical Society of America
A terahertz plastic wire based evanescent field sensor for high sensitivity liquid detection
(2009-11-09)
You, Borwen
;
Liu, Tze-An
;
Peng, Jin-Long
;
Pan, Ci-Ling
;
Lu, Ja-Yu
A highly sensitive detection method based on the evanescent wave of a terahertz subwavelength plastic wire was demonstrated for liquid sensing. Terahertz power spreading outside the wire core makes the waveguide dispersion sensitive to the cladding index variation, resulting in a considerable deviation of waveguide dispersion. Two liquids with transparent appearances, water and alcohol, are easily distinguished based on the waveguide dispersion, which is consistent with theoretical predictions. A melamine alcohol solution with various concentrations is identified successfully, and the detection limit is up to 20ppm, i.e. equivalent to the index variation on the order of 0.01. (C) 2009 Optical Society of America
Air-core microstructure fiber for terahertz radiation waveguiding
(2007)
Lu, Ja-Yu
;
Yu, Chin-Ping
;
Chang, Hung-Chung
;
Chen, Hung-Wen
;
Li, Yu-Tai
We demonstrate a simple and low-loss THz microstructure fiber for broadband THz waveguiding, which is constructed by using the highly flexible and readily available materials. Substantially low attenuation constant less than 0.01 cm(-1) has been achieved. (c) 2006 Optical Society of America
Characterization of Subwavelength Plastic Fiber Utilizing Terahertz Time-Domain Spectroscopy
(2009-01-01)
You, Borwen
;
Liu, Tze-An
;
Peng, Jin-Long
;
Pan, Ci-Ling
;
Lu, Ja-Yu
We present the first characterization of a simple subwavelength-diameter plastic wire by using wideband terahertz time-domain spectroscopy. The propagation characteristics including waveguide dispersion, group velocity, and attenuation constant of various plastic wires with different diameters and refractive indices are studied. The experimental results show the subwavelength plastic wire has extremely low waveguide dispersion and low attenuation constant (<0.01cm(-1)) at its THz transmission band due to much reduced fractional power delivered inside the lossy core, which is consistent with the theoretical calculations. With the large evanescent-fields, the subwavelength plastic wire has capability to integrate with micro-fluid channel for sensitive bio-sensing applications.
Investigation on spectral loss characteristics of subwavelength terahertz fibers
(2007-05-01)
Chen, Hung-Wen
;
Li, Yu-Tai
;
Pan, Ci-Ling
;
Kuo, Jeng-Liang
;
Lu, Ja-Yu
By measuring the spectral loss characteristics of subwavelength-diameter terahertz fibers, our study supports the recent theory proposed by M. Sumetsky [Opt. Lett. 31, 870 (2006)] that diameter-variation-induced radiation is a dominant loss mechanism for subwavelength fibers in the low- (<1%) core-fraction-power regime. This physical mechanism limits the lowest guidable frequency in a subwavelength fiber. (c) 2007 Optical Society of America.
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.
Spectral Loss Characteristics of Subwavelength THz Fibers
(2007)
Chen, Hung-Wen
;
Lu, Ja-Yu
;
Chen, Li-Jin
;
Li, Yu-Tai
;
Pan, Ci-Ling
From the spectral loss characteristics of subwavelength-diameter THz fibers, our study supports the recent theory proposed by M. Sumetsky that diameter-variation-induced-radiation is a dominant loss mechanism for subwavelength fibers which limits the lowest guidable frequency. (C) 2007 Optical Society of America
Terahertz air-core microstructure fiber
(2008-02-11)
Lu, Ja-Yu
;
Yu, Chin-Ping
;
Chang, Hung-Chung
;
Chen, Hung-Wen
;
Li, Yu-Tai
A low-loss terahertz air-core microstructure fiber is demonstrated for terahertz waveguiding. Substantially low attenuation constant less than 0.01 cm(-1) has been achieved and the guiding wavelength is found to be tunable by linear scaling the fiber size. The experimental results well agree with the simulation based on the finite-difference frequency-domain method, which interprets the guiding mechanism as the antiresonant reflecting waveguiding. The simulated modal pattern shows that most terahertz field is concentrated inside the central hollow air core and is guided without outside interference, which has high potential for guiding intense terahertz waves with minimized loss. (C) American Institute of Physics.
Terahertz gas sensing utilizing multilayer-stacked micro-porous polymer structure
(2013-01-01)
Ho, Cheng-Han
;
You, Borwen
;
Chan, Ming-Che
;
Lu, Ja-Yu
;
光電學院
A simple multilayer micro-porous structure has been successfully demonstrated for identifying different types and concentrations of vapor molecules. The measured minimum concentration is achieved 9 ppm, corresponding to molecular density variation of 0.16 nano-mole/mm(3).
Terahertz scanning imaging with a subwavelength plastic fiber
(2008-02-25)
Lu, Ja-Yu
;
Chiu, Chui-Min
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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 Fiber Directional Coupler
(2007)
Chen, Hung-Wen
;
Lu, Ja-Yu
;
Chen, Li-Jin
;
Chiang, Po-Jui
;
Chang, Hung-Chun
We demonstrated a THz subwavelength fiber coupler for future millimeter wave applications. Unlike traditional optical fiber couplers, its coupling ratio is independent of the length of the coupling region because of the anti-symmetric mode cutoff. (C) 2007 Optical Society of America
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