Browsing by Author "Liu, Tze-An"

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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
Analysis of terahertz pulses from large-aperture biased semi-insulating and arsenic-ion-implanted GaAs antennas
(2008-09-01)
Chou, Rone-Hwa
;
Liu, Tze-An
;
Pan, Ci-Ling
;
光電工程學系
;
Department of Photonics
We investigate the characteristics of terahertz radiation pulses generated using biased semi-insulating and arsenic-ion-implanted GaAs photoconductive antennas with 1.5 cm aperture size under various pump fluences and bias fields. Compared with semi-insulating GaAs antenna, our arsenic-ion-implanted GaAs antenna exhibits larger bandwidth and better emission efficiency. Our simulation verifies that the superior characteristics for the latter can be partly attributed to larger optical absorption in the ion-implanted layer. For both types of antennas, we observe that the radiated peak terahertz amplitude displays an anomalous dependence on pump fluence, which deviates from the prediction given by the scaling rule. Analyzing the theoretical and simulation results, we infer that this behavior arises from band filling and two-photon absorption effects. At specific pump fluence, we find that the dependence of peak terahertz amplitude on bias field is distinct from the usual linear relationship predicted by the scaling rule. (c) 2008 American Institute of Physics.
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.
Compact 84 GHz passive mode-locked fiber laser using dual-fiber coupled fused-quartz microresonator
(2017-10-01)
Liu, Tze-An
;
Hsu, Yung
;
Chow, Chi-Wai
;
Chuang, Yi-Chen
;
Ting, Wei-Jo
We propose and demonstrate a compact and portable-size 84-GHz passive mode-locked fiber laser, in which a dual-fiber coupled fused-quartz microresonator is employed as the intracavity optical comb filter as well as the optical nonlinear material for optical frequency comb generation. About eight coherent optical tones can be generated in the proposed fiber laser. The 20-dB bandwidth is larger than 588 GHz. The full-width halfmaximum pulse-width of the proposed laser is 2.5 ps. We also demonstrate the feasibility of using the proposed passive mode-locked fiber laser to carry a 5-Gbit/s on-off-keying signal and transmit over 20-km standard single mode fiber. A 7% forward error correction requirement can be achieved, showing the proposed fiber laser can be a potential candidate for fiber-wireless applications. (C) 2017 Society of Photo-Optical Instrumentation Engineers (SPIE)
Improved broadband and quasi-omnidirectional anti-reflection properties with biomimetic silicon nanostructures
(2007-12-01)
Huang, Yi-Fan
;
Chattopadhyay, Surojit
;
Jen, Yi-Jun
;
Peng, Cheng-Yu
;
Liu, Tze-An
Nature routinely produces nanostructured surfaces with useful properties, such as the self-cleaning lotus leaf, the colour of the butterfly wing, the photoreceptor in brittlestar and the anti-reflection observed in the moth eye. Scientists and engineers have been able to mimic some of these natural structures in the laboratory and in real-world applications. Here, we report a simple aperiodic array of silicon nanotips on a 6-inch wafer with a sub-wavelength structure that can suppress the reflection of light at a range of wavelengths from the ultraviolet, through the visible part of the spectrum, to the terahertz region. Reflection is suppressed for a wide range of angles of incidence and for both s- and p-polarized light. The antireflection properties of the silicon result from changes in the refractive index caused by variations in the height of the silicon nanotips, and can be simulated with models that have been used to explain the low reflection from moth eyes. The improved anti-reflection properties of the surfaces could have applications in renewable energy and electro-optical devices for the military.
Laser induced breakdown spectroscopy of pure aluminum with high temporal resolution
(2013-09-09)
Li, Yu-Tai
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Liu, Tze-An
;
Chen, Chen-Wei
;
Lee, Yu-Hsien
;
Yabushita, Atsushi
We report on a Laser Induced Breakdown Spectroscopy (LIBS) system with a very high temporal resolution, using femtosecond and picosecond pulse laser excitation of pure aluminum (Al). By using a 140 fs Ti:Sapphire laser in an ultrafast optical Kerr gate (OKG), we demonstrate LIBS sampling with a sub-ps time resolution (0.8 +/- 0.08 ps) in a 14 ns window. The width of the gating window in this system was as narrow as 0.8 ps, owing to the inclusion of a carbon disulfide (CS2) cell, which has a fast response and a large nonlinear coefficient. Furthermore, when using a 100 ps pulsed Nd:YAG laser and a fast photomultiplier tube (PMT) we demonstrate a LIBS system with a nanosecond time resolution (2.20 +/- 0.08 ns) in a microsecond window. With this sort of temporal resolution, a non-continuous decay in the Al signal could be observed. After 50 ns decay of the first peak, the second peak at 230 ns is started to perform. Experimental results with such short temporal windows in LIBS, in both nanosecond and microsecond ranges, are important for fast temporal evolution measurements and observations of early continuum emission in materials. (C) 2013 Optical Society of America
Simultaneously Transfer Microwave and Optical Frequency Through Fiber Using Mode-Locked Fiber Laser
(2009-01-01)
Kang, Chun-Wei
;
Liu, Tze-An
;
Shu, Ren-Huei
;
Pan, Ci-Ling
;
Peng, Jin-Long
Microwave and optical frequency references are simultaneously transferred through fiber using a frequency-stabilized mode-locked Er-fiber laser comb. The instability for transferred microwave and optical frequencies are 2.0x10(-3) and 7.5x10(-1)5@1 s, respectively, for 3 km transmission. (C) 2009 Optical Society of America