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Multiple pulses and harmonic mode locking from passive mode-locked Ytterbium doped fiber in anomalous dispersion region
(2015-01-01)
Lin, Ja-Hon
;
Lee, Hung-Yi
;
Hsieh, Wen-Feng
;
光電工程學系
;
光電工程研究所
In this work, we investigate the passive mode-locked Ytterbium-doped fiber laser based on the nonlinear polarization rotation technique. With the grating pairs inside laser cavity for the GVD compensation, the total cavity dispersion is operated within anomalous dispersion region. As the laser operates at fundamental mode locking, it generates 35 MHz repetition rate mode-locked pulse with 3.3 ps pulsewidth and the optical spectrum reveals obvious Kelly side. After adjusting the waveplate or increase the pump power, the 2nd HML to 6th harmonic mode locking (HML) is demonstrated in this laser. Besides, we also generated the bound states of multiple solitons whose separation of each pulse is about several tens of picosecond. The number of solitons and the separation between sequential pulses could be controlled so that it could be used in optical communication.
Frequency measurement of the 6P(3/2) -> 7S(1/2) transition of thallium
(2013-12-30)
Shie, Nang-Chian
;
Chang, Chun-Yu
;
Hsieh, Wen-Feng
;
Liu, Yi-Wei
;
Shy, Jow-Tsong
The saturated absorption spectrum of the 6P(3/2) -> 7S(1/2) transition of Tl-203 and Tl-205 in a hollow cathode lamp has been observed with a frequency-doubled 1070 nm Nd : GdVO4 laser. The third-derivative spectrum of the hyperfine components are obtained using the wavelength modulation spectroscopy and used to stabilize the laser frequency. The analysis of the error signal shows that the frequency stability reaches 30 kHz at 1 s averaging time. Such a frequency-stabilized light source at 535 nm can be used for laser cooling of thallium and for investigating the parity non-conservation effect in thallium. The absolute frequencies of hyperfine components are measured with an accuracy of 30 MHz using a precision wavelengthmeter. Including the pressure shift correction, the center of gravity of the transition frequency is determined to an accuracy of 22 MHz for both isotopes. Meanwhile, the isotope shift derived is in good agreement with earlier measurement.
Effect of atomic position on the spontaneous emission of a three-level atom in a coherent photonic-band-gap reservoir
(2009-01-01)
Cheng, Szu-
;
Wu, Jing-Nuo
;
Yang, Tzong-Jer
;
Hsieh, Wen-Feng
;
光電工程學系
The effect of atomic position on the spontaneous emission and optical spectra of a three-level atom embedded in a photonic crystal was studied by considering the coherent two-band photonic-band-gap (PBG) reservoir. With the definite phase difference between the fields of the air band and dielectric band in this coherent PBG reservoir, we found that this coherent property grows stronger and results in the spectrum shift and the appearance of dark lines and kinks as the width of band gap gets smaller; and the variation of the atomic position leads to large shift of spectral peak. The averaged spectra of the system with an ensemble of atoms embedded in the dielectric region are blueshifted while those of atoms in the air region are redshifted. The spectra peaks can even shift more than 75% of the half width at half maximum. The feasible experimental systems composed of an ensemble of molecules (quantum dots or fluorescence dye) in photonic crystals are discussed.
Nonequilibrium and nonlinear defect states in microcavity-polariton condensates
(2016-05-18)
Chen, Ting-Wei
;
Jheng, Shih-Da
;
Hsieh, Wen-Feng
;
Cheng, Szu-Cheng
;
物理研究所
The nonequilibrium and nonlinear defect modes (NNDMs), localized by a defect in a nonequilibrium microcavity-polariton condensate (MPC), are studied. There are three analytic solutions of NNDMs in a point defect: the bright NNDM, a bound state with two dark solitons for an attractive potential, and a gray soliton bound by a defect for a repulsive potential. We find that the stable NNDMs in a nonequilibrium MPC are the bright NNDM and gray soliton bound by a defect. The bright NNDM, which has the hyperbolic cotangent form, is a bright localized state existing in a uniform MPC. The bright NNDM is a unique state occurring in a nonequilibrium MPC that has pump-dissipation and repulsive-nonlinearity characters. No such state can exist in an equilibrium system with repulsive nonlinearity.
The effect of thermal annealing on the optical and electrical properties of ZnO epitaxial films grown on n-GaAs (001)
(2015-01-01)
Liu, Wei-Rein
;
Lin, Bi-Hsuan
;
Lin, Chi-Yuan
;
Yang, Song
;
Kuo, Chin-Chia
Wurtzite ZnO epitaxial layers grown on n-type GaAs (001) by pulsed laser deposition (PLD) exhibited n-type conductivity. Post-growth annealing leads the conversion of carrier type from electron to hole, as revealed by Hall effect measurements, although only moderate structural improvement was observed. The carrier type conversion is attributed to thermally activated arsenic diffusion from the substrate, confirmed by secondary ion mass spectrometry and photoluminescence. The surface electrical properties of both the as-deposited n-type and annealed p-type ZnO epitaxial layers were thoroughly characterized by Kelvin force microscopy (KFM) and electrostatic force microscopy (EFM). The results indicated the existence of a high density of surface states close to the ZnO midgap with a density of a few 10(14) cm(-2) eV(-1). The Fermi levels (E-F) of n- and p-type ZnO epitaxial layers were found to be 1.06 eV below the conduction-band minimum (CBM) and 1.612-1.769 eV above the valence-band maximum (VBM), respectively. The small EF difference between the n- and p-type ZnO epitaxial layers implies Fermi level pinning at the surface of both n-and p-type ZnO epitaxial layers.
Tuning the functionalities of a mesocrystal via structural coupling
(2015-07-14)
Liu, Heng-Jui
;
Liu, Yun-Ya
;
Tsai, Chih-Ya
;
Liao, Sheng-Chieh
;
Chen, Ying-Jiun
In the past decades, mesocrystal, a kind of nanocrystals with specific crystallographic orientation, has drawn a lot of attention due to its intriguing functionalities. While the research community keeps searching for new mesocrystal systems, it is equally crucial to develop new approaches to tune the properties of mesocrystals. In this work, a self-organized two-dimensional mesocrystal composed of highly oriented CoFe2O4 (CFO) nano-crystals with assistance of different perovskite matrices is studied as a model system. We have demonstrated that the strain state and corresponding magnetic properties of the CFO mesocrystal can be modulated by changing the surrounding perovskite matrix through their intimate structural coupling. Interestingly, this controllability is more strongly correlated to the competition of bonding strength between the matrices and the CFO mesocrystals rather than the lattice mismatch. When embedded in a matrix with a higher melting point or stiffness, the CFO mesocrystal experiences higher out-of-plane compressive strain and shows a stronger magnetic anisotropy as well as cation site-exchange. Our study suggests a new pathway to tailor the functionalities of mesocrystals.
Spontaneous emission from a two-level atom in anisotropic one-band photonic crystals: A fractional calculus approach
(2010-02-01)
Wu, Jing-Nuo
;
Huang, Chih-Hsien
;
Cheng, Szu-Cheng
;
Hsieh, Wen-Feng
;
光電工程學系
Spontaneous emission ( SE) from a two-level atom in an anisotropic photonic crystal ( PC) is investigated by the fractional calculus. Physical phenomena of the SE are studied analytically by solving the fractional kinetic equations of the SE. There is a dynamical discrepancy between the SE of anisotropic and isotropic PCs. We find that, contrary to the SE phenomenon of the isotropic PC, the SE near the band edge of an anisotropic PC shows no photon-atom bound state. It is consistent with the experimental results of Barth, Schuster, Gruber, and Cichos [Phys. Rev. Lett. 96, 243902 ( 2006)] that the anisotropic property of the system enhances the SE. We also study effects of dispersion curvatures on the changes of the photonic density of states and the appearance of the diffusion fields in the SE.
High-power passively continuous-wave and Q-switching mode-locked Nd:LuVO4 laser by few-layer graphene-oxide films
(2016-12-01)
Chen, Hou-Ren
;
Tsai, Chih-Ya
;
Cheng, Hsin-Ming
;
Lin, Kuei-Huei
;
Chen, Chyong-Hua
Using a series of different concentration polymer-free graphene oxide (GO) films as saturable absorbers (SAs), we demonstrate high-power passively continuous-wave modelocking (CW-ML) and Q-switching mode-locking (QS-ML) for a Nd: LuVO4 laser at 1 mu m. CW-ML pulses of 6.62 ps with maximum output power of 3.89 W have been achieved to give the highest pulse peak power of 4.85 kW and pulse energy of 32.14 nJ under 15-W pumping by using SAs of 84.4% transmittance. Using SAs with a lower transmittance having a larger modulation depth of 75.9% and 63.4%, we obtain both the CW-ML pulses of 4.85-ps and QSML pulses with 2.73 W and 1.92 W output powers, respectively. (C) 2016 Optical Society of America
High-quality and Large-size Topological Insulator Bi2Te3-Gold Saturable Absorber Mirror for Mode-Locking Fiber Laser
(2016-12-05)
Chen, Hou-Ren
;
Tsai, Chih-Ya
;
Cheng, Hsin-Ming
;
Lin, Kuei-Huei
;
Yen, Po-Hsiu
A novel high-quality, large-size, reflection-type topological insulator Bi2Te3-Gold (BG) film-based nonlinear optical modulator has been successfully fabricated as a two-dimensional saturable absorber mirror (SAM) by pulsed laser deposition (PLD). This BG-SAM possesses saturation fluence of 108.3 mu J/cm(2), modulation depth (Delta R) of 6.5%, non-saturable loss of 38.4%, high damage threshold above 1.354 mJ/cm(2) and excellent uniformity providing for the generation of passive mode-locked (ML) pulses for erbium-doped fiber lasers (EDFLs) on a large sample area. Under 124 mW 976 nm pumping, We obtained 452-fs continuous-wave ML pulses with pulse energy of 91 pJ and full width at halfmaximum (FWHM) of 6.72-nm from this EDFL. The results clearly evidence that the PLD is an efficient method for fabricating BG-SAM that is suitable for a compact ultrafast ML fiber laser system.
Stable gray soliton pinned by a defect in a microcavity-polariton condensate
(2015-09-21)
Chen, Ting-Wei
;
Hsieh, Wen-Feng
;
Cheng, Szu-Cheng
;
光電工程學系
;
光電工程研究所
We study the spatially localized dark state, called dark soliton, in a one-dimensional system of the non-resonantly pumped microcavity-polariton condensate (MPC). From the recent work by Xue and Matuszewski [Phys. Rev. Lett. 112, 216401 (2014)], we know that the dark soliton in the pure MPC system is unstable. But we find that a dark soliton pinned by a defect in the impure MPC becomes a gray soliton and can be stabilized by the presence of a defect. Moreover, the stable regime of the gray soliton is given in terms of the defect strength and pump parameter. (C) 2015 Optical Society of America

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