Browsing by Author "Li, Yu-Tai"

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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
Bandwidth enhancement phenomenon of a high-speed GaAs-AlGaAs based unitraveling carrier photodiode with an optimally designed absorption layer at an 830 nm wavelength
(2006-07-31)
Shi, Jin-Wei
;
Li, Yu-Tai
;
Pan, Ci-Ling
;
Lin, M. L.
;
Wu, Y. S.
In this letter, the authors introduce a GaAs/AlGaAs based unitraveling carrier photodiode (UTC-PD) for a wavelength of around 830 nm. There is significant bias- and output-current-dependent bandwidth enhancement phenomena observed with this device. According to their microwave and optical-to-electrical measurement results, such distinct phenomena can occur under a much lower current density (0.3 mA/mu m(2) vs 0.05 mA/mu m(2)) than previously reported for InP-InGaAs UTC-PDs. This can be attributed to the self-induced field in the absorption region, made possible due to the optimized p-type doping profile. (c) 2006 American Institute of Physics.
Characterization and Comparison of GaAs/AlGaAs Uni-Traveling Carrier and Separated-Transport-Recombination Photodiode Based High-Power Sub-THz Photonic Transmitters
(2010-01-01)
Li, Yu-Tai
;
Shi, Jin-Wei
;
Huang, C. -Y.
;
Chen, Nan-Wei
;
Chen, Shu-Han
We describe in detail the characterization of two high-power photonic transmitters based on two different kinds of high-power photodiodes, one a GaAs/AlGaAs based uni-traveling-carrier photodiode (UTC-PD) and the other a separated-transport-recombination photodiode (STR-PD). The diodes operate under optical pulse excitation at the 800 nm wavelength. Both PDs have the same total depletion layer thickness (same theoretical RC-limited bandwidth) and are m integrated with the same broadband micro-machined circular disk monopole antennas to radiate strong sub-THz pulses. However the STR-PD based transmitter exhibits very different dynamic and static performance from that of the UTC-PD based transmitter due to the existence of a low-temperature-grown GaAs (LTG-GaAs) based recombination center inside the active region, and the much thinner thickness of effective depletion layer. Under optical pulse excitation (similar to 480 pJ/pulse), the STR-PD based transmitter exhibits a much lower maximum averaged output photocurrent (1.2 mA versus 0.3 mA) than that of the UTC-PD transmitter, although the radiated electrical pulse-width and maximum peak-power, which are measured by the same THz time-domain spectroscopic (TDS) system, of both devices are comparable. These results indicate that although the recombination center in the STR-PD degrades its DC responsivity, it effectively improves the high-speed and output power performance of the device and eliminates the DC component of the photocurrent, which should minimize device-heating problem during high-power operation. The radiated waveforms of both devices under intense optical pulse illumination also exhibit excellent linearity and strong bias dependent magnitude. This suggests their suitability for application as photonic emitters and possibly as a data modulator in sub-THz impulse-radio communication systems.
Characterization of a Sub-THz Photonic Transmitter Based on a Sep arated-Tran sp o rt-Recombin ation Photodiode
(2007)
Shi, J. -W.
;
Li, Yu-Tai
;
Pan, Ci-Ling
;
Chiu, C. -H.
;
Liu, W. -S.
By incorporating low-temperature-grown GaAs based separated-transport-recombination photodiode with micromachined antenna, such photonic-transmitter can radiate strong sub-THz waves at designed frequency (similar to 500GHz) without using Si-lens. Problems of device saturation under high bias voltage were also eliminated. (C) 2005 Optical Society of America
Characterization of sub-THz photonic-transmitters based on CaAs-AlGaAs uni-traveling-carrier photodiodes and substrate-removed broadband antennas for impulse-radio communication
(2008-07-01)
Li, Yu-Tai
;
Shi, J. -W.
;
Huang, Cheng-Yu
;
Chen, Nan-Wei
;
Chen, Shu-Han
A novel photonic transmitter for wireless terahertz (THz) impulse-radio (IR) communication is realized by monolithic integration of a GaAs-AlGaAs-based uni-traveling-carrier (UTC) photodiode with a substrate-removed broadband antenna. The device can radiate strong sub-THz pulses (20-mW peak-power) with a narrow pulsewidth (< 2 ps) and wide bandwidth (100 similar to 250 GHz). The maximum average power emitted by our device, under the same THz time-domain spectroscopic setup, is around ten times higher than that of the low-temperature-grown GaAs-based photoconductive antenna, while with a much lower dc bias (9 versus 35 V). The bias-dependent peak output powers of our devices suggest their suitability for application as a data modulator/emitter for photonic THz IR communication.
Distinct Dynamic Behaviors of High-Power Photonic-Transmitters Based on Uni-Traveling Carrier and Separated-Transport-Recombination Photodiodes
(2009)
Li, Yu-Tai
;
Yang, Chan-Shan
;
Pan, Ci-Ling
;
Shi, J. -W.
;
Huang, C. -Y.
We demonstrate two high-performance photonic-transmitters based on uni-traveling-carrier-photodiode (UTC-PD) and separated-transport-recombination-photodiode (STR-PD). Thanks to recombination center, STR-PD exhibits comparable maximum-peak-power and electrical pulse-width with much smaller photocurrents and less serious device-heating to those of UTC-PD.
Electrically Controlled Liquid Crystal Phase Grating for Terahertz Waves
(2009-05-01)
Lin, Chia-Jen
;
Lin, Chuan-Hsien
;
Li, Yu-Tai
;
Pan, Ru-Pin
;
Pan, Ci-Ling
This work demonstrates the feasibility of electrically controlled liquid-crystal-based phase grating for manipulating the terahertz (THz) waves. This device can be utilized as a THz beam splitter and the beam splitting ratio of the zeroth- to the first-order diffractions can be tuned from 10 : 1 to 1: 1.
Investigation of Degradation of Single-Cell PV Module by Pressure Cooker Test and Damp Heat Test
(2016-01-01)
Tung, Chao-Ming
;
Li, Yu-Tai
;
Yang, Wei-Lun
;
Wu, Hung-Sen
;
Yu, Peichen
Accelerated methods for evaluating thermo humidity resistance of single-cell PV module are demonstrated with standard damp heat test (DH) and non-standard pressure cooker test (PCT). We investigated the failure mechanism of PCT. Our result shows testing under PCT more than 121 degrees C has fast degradation compared to other condition.
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.
Laser induced breakdown spectroscopy of pure aluminum with high temporal resolution
(2013-09-09)
Li, Yu-Tai
;
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
Manipulating terahertz wave by a magnetically tunable liquid crystal phase grating
(2008-03-03)
Lin, Chia-Jen
;
Li, Yu-Tai
;
Hsieh, Cho-Fan
;
Pan, Ru-Pin
;
Pan, Ci-Ling
This investigation demonstrates the feasibility of a magnetically tunable liquid crystal phase grating for the terahertz wave. The phase grating can be used as a beam splitter. The ratio of the zeroth and first-order diffracted THz-beams (0.3 THz) polarized in a direction perpendicular to that of the grooves of the grating can be tuned from 4:1 to 1:2. When the THz wave is polarized in any other direction, this device can be operated as a polarizing beam splitter.
Photonic Impulse-Radio Wireless 2.5Gbit/sec Data Transmission at W-Band Using Near-Ballistic Uni-Traveling-Carrier Photodiode (NBUTC-PD) Based Photonic Transmitter
(2009)
Kuo, F. -M.
;
Li, Yu-Tai
;
Shi, J-W
;
Wang, Shao-Ning
;
Chen, Nan-Wei
By using novel near-ballistic uni-traveling-carrier photodiodes (NBUTC-PDs) based W-band photonic transmitter and a mode-locked laser with a 10GHz repetition rate, 2.5Gbit/sec impulse-radio wireless data transmission at 100GHz with 3.3m maximum transmission distance have been demonstrated.
Photonic Impulse-Radio Wireless Link at W-Band Using a Near-Ballistic Uni-Traveling-Carrier Photodiode-Based Photonic Transmitter-Mixer
(2010-01-15)
Kuo, F. -M.
;
Li, Yu-Tai
;
Shi, J. -W.
;
Wang, Shao-Ning
;
Chen, Nan-Wei
A W-band photonic transmitter-mixer, constructed by integrating a planar quasi-yagi radiator for feeding the WR-10 waveguide-based horn antenna and a near-ballistic uni-travelingcarrier photodiode, is used with a mode-locked fiber laser to obtain 2.5-Gb/s impulse-radio (IR) wireless data transmission at around a center frequency of 100 GHz. The bias-modulation technique provides less jitter and a longer maximum transmission distance compared with the technique of modulating the optical pulse train using an electrooptics modulator. Using the bias-modulation technique, we achieve a 2.5-Gb/s IR wireless data transmission.
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.
Some Characteristics of a Liquid-Crystal Phase Grating for THz Waves
(2009)
Lin, Chia-Jen
;
Lin, Chuan-Hsien
;
Hsieh, Cho-Fan
;
Pan, Ru-Pin
;
Li, Yu-Tai
We propose and demonstrate an electrically controlled liquid crystal phase grating for the terahertz wave. The performance of the device was characterized by a terahertz time-domain spectrometer. The experimental results were in a good agreement with the prediction by classic diffraction theory.
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
Sub-THz Photonic-Transmitters Based on GaAs/AlGaAs Uni-Traveling Carrier Photodiode and Micromachined Circular Disk Monopole Antenna for Ultra-wideband Communication
(2008)
Li, Yu-Tai
;
Pan, Ci-Ling
;
Shi, J. -W.
;
Huang, Cheng-Yu
;
Chen, Nan-Wei
By incorporating GaAs/AlGaAs based uni-traveling-carrier photodiodes with broadband micromachined monopole antennas, the demonstrated photonic-transmitter can radiate strong sub-THz pulses (20mW peak-power) with a wide bandwidth (100 similar to 250GHz), which was measured by another photonic-receiver for ultra-wideband communication. (c) 2008 Optical Society of America
Sub-THz photonic-transmitters based on separated-transport-recombination photodiodes and a micromachined slot antenna
(2007-05-01)
Li, Yu-Tai
;
Shi, J.-W.
;
Pan, Ci-Ling
;
Chiu, C.-H.
;
Liu, W.-S.
We demonstrate a novel photonic transmitter, which is composed of a low-temperature-grown GaAs (LTG-GaAs)-based separated-transport-recombination photodiode and a micromachined slot antenna. Under femtosecond optical pulse illumination, this device radiates strong electrical pulses (4.5-mW peak power) without the use of a Si-lens. It can be observed in the Fourier transform infrared spectrometer spectrum of radiated pulses that a significant resonance, with a peak power of approximately 300 mu W, occurs at 500 GHz, which corresponds to the designed resonant frequency of the slot antenna. The saturation problem related to the output terahertz power that occurs with the traditional LTG-GaAs-based photonic-transmitters when operated under high external applied electrical fields (> 50 kV/cm) has been eliminated by the use of our device.