Browsing by Author "Pan, C. -L."

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13 Gbit/s WDM-OFDM PON using RSOA-based colourless ONU with seeding light source in local exchange
(2011-10-27)
Chow, C. W.
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Yeh, C. H.
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Wu, Y. F.
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Chen, H. Y.
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Lin, Y. H.
Optical-carrier-distribution using reflective-semiconductor-optical-amplifier (RSOA)-based colorless optical-networking-unit (ONU) is a promising candidate for the wavelength-division-multiplexed passive-optical-network (WDM-PON). However, commercial available RSOA has a typical modulation-bandwidth of similar to 1 GHz, which is not enough for the future bandwidth demand. Here we demonstrate a WDM-PON using 1 GHz bandwidth RSOA-based ONU, which can be operated up to 13 Gbit/s. Experimental results show that 20 km singlemode-fibre transmission of the 13 Gbit/s orthogonal-frequency-division-multiplexed (OFDM) signal can be achieved with bit-error rate lower than the forward error correction threshold.
A scalable and continuous-upgradable optical wireless and wired convergent access network
(2014-06-02)
Sung, J. Y.
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Cheng, K. T.
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Chow, C. W.
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Yeh, C. H.
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Pan, C. -L.
In this work, a scalable and continuous upgradable convergent optical access network is proposed. By using a multi-wavelength coherent comb source and a programmable waveshaper at the central office (CO), optical millimeter-wave (mm-wave) signals of different frequencies (from baseband to > 100 GHz) can be generated. Hence, it provides a scalable and continuous upgradable solution for end-user who needs 60 GHz wireless services now and > 100 GHz wireless services in the future. During the upgrade, user only needs to upgrade their optical networking unit (ONU). A programmable waveshaper is used to select the suitable optical tones with wavelength separation equals to the desired mm-wave frequency; while the CO remains intact. The centralized characteristics of the proposed system can easily add any new service and end-user. The centralized control of the wavelength makes the system more stable. Wired data rate of 17.45 Gb/s and w-band wireless data rate up to 3.36 Gb/s were demonstrated after transmission over 40 km of single-mode fiber (SMF). (C) 2014 Optical Society of America
Application of Super-Fine Ink-Jet Printer to Fabrication of Terahertz Planer Metamaterials
(2009)
Kawabata, T.
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Takano, K.
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Hsieh, C. -F.
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Akiyama, K.
;
Miyamaru, F.
A super-fine ink-jet (SIJ) printing technology has been applied to the fabrication of terahertz metamaterials. The SIJ printing process is very simple and flexible, although the accuracy of the metallic line is comparable to the photolithography process. We fabricate basic terahertz metamaterials printed on high resistivity Si substrates: metal wire-grid structures and split-ring resonator arrays. The terahertz responses of the printed samples agree with those expected from the structures. The SIJ printing has a potential to accelerate the developments of the terahertz metamaterial researches.
Attosecond pulse synthesis and arbitrary waveform generation with cascaded harmonics of an injection-seeded high-power Q-switched Nd:YAG laser
(2012-03-01)
Chen, W. -J.
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Wang, H. -Z.
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Lin, R. -Y.
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Lee, C. -K.
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Pan, C. -L.
We propose a new scheme of attosecond pulse generation by starting from a narrow-band transform-limited high-power solid-state laser and phase lock the fundamental and its first four cascaded harmonics generated by the second-order nonlinear optical processes. The relative phase among the optical fields of the harmonics can be maintained a constant at least for thousands of nanosecond pulses. The worst-case relative phase fluctuation is 0.04p rad. It is shown that sub-single-cycle (similar to 0.37 cycle) sub-femtosecond (360 attosecond) pulses with carrier-envelope phase (CEP) control can be generated in this manner. The peak intensity of each pulse exceeds 1014 W/cm2 when it is focused to a spot size of 20 mu m. We also demonstrate synthesis of square and saw-tooth waveforms. ((c) 2012 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) ((c) 2011 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA)
Dependence of terahertz radiation on gap sizes of biased multi-energy arsenic-ion-implanted and semi-insulating GaAs antennas
(2009-06-01)
Liu, T. -A.
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Chou, R. -H.
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Pan, C. -L.
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光電工程學系
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Department of Photonics
We investigate the characteristics of terahertz radiation pulses using biased multi-energy arsenic-ion-implanted and semi-insulating GaAs photoconductive antennas with different gap sizes in terahertz time-domain spectroscopy. At a specific fluence excitation, with increasing antenna gap size, the absolute values of the (peak) normalized terahertz waveform minimum (valley), as well as the bandwidth, reveal an increasing trend for multi-energy arsenic-ion-implanted GaAs antennas and a decreasing trend for semi-insulating GaAs antennas. We find that the largest reachable bias fields applied to arsenic-ion-implanted GaAs antennas are higher than those applied to semi-insulating GaAs antennas. On the basis of pump fluence dependences of peak terahertz amplitude, we deduce that multi-energy arsenic-ion-implanted GaAs antennas have the ability to acquire higher THz power at even higher pump fluence in comparison with semi-insulating GaAs antennas.
Free carrier dynamics of InN nanorods investigated by time-resolved terahertz spectroscopy
(2009-01-15)
Ahn, H.
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Chuang, C. -H.
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Ku, Y. -P.
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Pan, C. -L.
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光電工程學系
Ultrafast time-resolved terahertz spectroscopy is employed to investigate the carrier dynamics of indium nitride (InN) nanorod arrays and an epitaxial film. Transient differential transmission of terahertz wave shows that hot carrier cooling and defect-related nonradiative recombination are the common carrier relaxation processes for InN film and nanorods. However, the electrons confined in the narrow structure of nanorods are significantly affected by the carrier diffusion process near the surface, which causes the abnormally long relaxation time for nanorods.
Grain-size-related transient terahertz mobility of femtosecond-laser-annealed polycrystalline silicon
(2009-09-01)
Wang, Y. -C.
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Ahn, H.
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Chuang, C. -H.
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Ku, Y. -P.
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Pan, C. -L.
We investigated carrier-relaxation dynamics of femtosecond laser annealed (FLA) polycrystalline silicon (poly-Si). The correlation between morphology and electrical properties of poly-Si after femtosecond laser annealing is elucidated by optical-pump-terahertz-probe and terahertz time-domain spectroscopies. The transient conductivities of FLA-processed poly-Si with large (similar to 500 nm) and small (similar to 50 nm) grain sizes were both well fitted by the Drude model in the terahertz regime from 0.4 to 2 THz. The transient mobilities of these materials were determined to be 175 +/- 19.4 and 94.5 +/- 20.2 cm(2)/V s, respectively. After annealing, reduction of deep-state density rather than tail-state density in large-grain poly-Si is responsible for its higher mobility.
Intense terahertz emission from a-plane InN surface
(2008-03-10)
Ahn, H.
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Ku, Y. -P.
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Chuang, C. -H.
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Pan, C. -L.
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Lin, H. -W.
We report a significant enhancement in terahertz emission from the indium nitride (InN) films grown along the a axis (a-plane InN), relative to the InN films grown along the c axis. The primary radiation mechanism of the a-plane InN film is found to be due to the acceleration of photoexcited carriers under the polarization-induced in-plane electric field perpendicular to the a axis, which effectively enhances the geometrical coupling of the radiation out of semiconductor. In addition, azimuthal angle dependence measurement shows that the p-polarized terahertz output consists of a large angularly independent component and a weak component with a distinctive fourfold rotation symmetry. (c) 2008 American Institute of Physics.
Recent advances in millimeter-wave photonic wireless links for very high data rate communication
(2011)
Pan, C. -L.
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Chow, C. W.
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Yeh, C. H.
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Huang, C. B.
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Shi, J. W.
To provide integrated and high quality broadband services, higher carrier frequencies are required in wireless communications. Currently, there is a great deal of interests in wireless communications at sub-terahertz or terahertz frequencies, i.e., the millimeter-wave (MMW) or sub-millimeter-wave (sub-MMW). In this work, we will discuss our recent advances in millimeter-wave photonic wireless links for high data rate (10 - 20 Gb/s) communications. The concept of fiber-to-the-antenna (FTTA) system using radio-over-fiber (ROF) technologies will be given in the introduction. Then a design and the structure of the high speed MMW photonic transmitter, namely near-ballistic uni-traveling-carrier photodiode (NBUTC-PD), will be discussed in section 2. In section 3, the operation principle of photonic mm-wave waveform generator (PMWG), which is used to produce the optical pulse train for the photonic transmitter at the antenna-site will be illustrated. We then demonstrate the use of the NBUTC-PD and the PMWG for the downstream and upstream high data rate communications in the W-band.
Recent advances in millimeter-wave photonic wireless links for very high data rate communication
(2012)
Pan, C. -L.
;
Chow, C. W.
;
Yeh, C. H.
;
Huang, C. B.
;
Shi, J. W.
To provide integrated and high quality broadband services, higher carrier frequencies are required in wireless communications. Currently, there is a great deal of interests in wireless communications at sub-terahertz or terahertz frequencies, i.e., the millimeter-wave (MMW) or sub-millimeter-wave (sub-MMW). In this work, we will discuss our recent advances in millimeter-wave photonic wireless links for high data rate (10 20 Gb/s) communications. The concept of fiber-to-the-antenna (FTTA) system using radio-over-fiber (ROF) technologies will be given in the introduction. Then a design and the structure of the high speed MMW photonic transmitter, namely near-ballistic uni-traveling-carrier photodiode (NBUTC-PD), will be discussed in section 2. In section 3, the operation principle of photonic mm-wave waveform generator (PMWG), which is used to produce the optical pulse train for the photonic transmitter at the antenna-site will be illustrated. We then demonstrate the use of the NBUTC-PD and the PMWG for the downstream and upstream high data rate communications in the W-band.
Square-core single-mode-fiber (SC-SMF) with high bending tolerance for data center networks
(2015-08-15)
Chow, C. W.
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Huang, S. P.
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Yeh, C. H.
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Sung, J. Y.
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Liu, P. F.
Square-core optical fiber has been proposed recently for high optical power delivery in industrial processing tools with core size larger than 400 x 400 mu m(2). In this work, we first study the possibility of significantly reducing the core side to single-mode condition (i.e. 9 x 9 mu m(2)) at optical communication wavelength. In the proposed square-core single-mode-fiber (SC-SMF), high bandwidth-distance product and low bending loss are achieved. We also discuss the fabrication of the SC-SMF. After this, the bending losses of the SC-SMF and standard single mode fiber (SSMF) are analyzed and compared. Finally, 10 Gb/s signal transmission using conventional on-off keying (OOK) and orthogonal frequency division multiplexing (OFDM) passing through 200 m, 500 m and 1 km SC-SMFs are performed. Negligible power penalty is observed. We believe that this can be another choice of high bending tolerance fiber which is simple to manufacture. (C) 2015 Elsevier B.V. All rights reserved.
Terahertz emission and spectroscopy on InN epilayer and nanostructure
(2009)
Ahn, H.
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Pan, C. -L.
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Gwo, S.
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光電工程學系
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Department of Photonics
We report a comprehensive study on THz emission and spectroscopy of indium nitride (InN) films and its nanorod arrays grown by plasma-assisted molecular beam epitaxy technique. For the enhancement of THz emission from InN, we demonstrated two method; firstly using nanorod arrays, which have large surface area for optical absorption and THz emission, and secondly using nonpolar InN film, of which the electric field is along the sample surface. We propose that a "screened" photo-Dember effect due to narrow surface electron accumulation layer of InN is responsible for the nanorod-size-dependent enhancement from InN nanorods. The primary THz radiation mechanism of nonpolar InN is found to be due to the acceleration of photoexcited carriers under the polarization-induced in-plane electric field. THz time-domain spectroscopy has been used to investigate THz conductivity and dielectric response of InN nanorod arrays and epitaxial film. The complex THz conductivity of InN film is well fitted by the Drude model, while the negative imaginary conductivity of the InN nanorods can be described by using a non-Drude model, which includes a preferential backward scattering due to defects in InN nanorods, or a Coulombic restoring force from charged defects.
Terahertz spectroscopic study of vertically-aligned InN nanorods (vol 91, 163105, 2007)
(2009-05-04)
Ahn, H.
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Ku, Y. -P.
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Wang, Y. -C.
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Chuang, C. -H.
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Gwo, S.
Using dual-mode self-locked semiconductor laser for optical millimeter-wave application
(2011-03-01)
Yeh, C. -H.
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Chow, C. -W.
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Liu, Y. -F.
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Pan, C. -L.
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光電工程學系
In this study, an optical millimeter-wave (mm-wave) generator is proposed and experimentally demonstrated by using a self-injected Fabry-Perot laser diode (FP-LD), having mode spacing of 1.11 nm, for dual-mode beating in 140 GHz band (terahertz band). The created dual-wavelength also can be also modulated at 1.25, 2.5, and 10 Gb/s with on-off keying (OOK) modulation format by external optical modulator, respectively, in 20 km fiber transmission. Moreover, the dual-mode laser can be selected in difference wave-lengths by tuning the optical filter inside cavity for the future WDM applications.
Utilizing erbium fiber ring scheme and Fabry-Perot laser diode for stable and wavelength-tunable laser in single-longitudinal-mode output
(2011-02-01)
Yeh, C. -H.
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Chow, C. -W.
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Pan, C. -L.
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光電工程學系
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Department of Photonics
In this investigation, we propose and demonstrate a stable and wavelength-tunable erbium-doped fiber (EDF) ring laser scheme with external-injected Fabry-Perot laser diode (FP-LD) technology, in single-longitudinal-mode (SLM) output behavior. Here, the output power and side-mode suppression ratio (SMSR) of the proposed laser scheme can be obtained between -3.9 and 1.3 dBm and 30.1 and 50.5 dB in the operating wavelengths of 1523.65 and 1561.50 nm with 1.12 nm tuning step, respectively, according to the output mode-spacing of FP-LD used. Besides, the lasing stabilities of output power and wavelength are also investigated and discussed.
Vertically-Aligned Indium Nitride Nanorod Arrays as Bright Terahertz Emitter
(2008)
Ahn, H.
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Pan, C. -L.
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光電工程學系
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Department of Photonics
The physical properties of vertically-aligned Indium Nitride (InN) nanorod arrays grown on Si(111) substrates by plasma-assisted molecular-beam epitaxy in terahertz (THz) spectral range has been elucidated by terahertz time-domain spectroscopy (THz-TDS) and their application as the efficient THz emitter has been investigated. The key parameters that determine the free carrier dynamics of the InN nanorods are extracted by applying a modified Drude model, which includes the scattering effect of electrons along the boundary of nanorods, while those of InN film are obtained by the Drude model. Due to the large surface areas provided by the sidewalls of nanorods, more than ten times of THz intensity enhancement compared to InN film is obtained for photoexcited InN nanorod array through the photo-Dember effect. However, the power enhancement is selectively depending on the size of the nanorods with respect to the thickness of surface accumulation layer.