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921.
A novel dual-frequency paired polarization phase shifting ellipsometer (DPPSE) is proposed and experimentally demonstrated. It combines the features of the phase shifting interferometer and common-path polarized heterodyne interferometric ellipsometer where the ellipsometric parameters (EP) of a specimen are measured accurately. The experimental results verify that DPPSE is capable of determining the full dynamic range of EP. In addition, the properties of dual-frequency paired linearly polarized laser beam in DPPSE perform in common phase noise rejection mode. It is insensitive to environmental disturbance and laser frequency noise. The capability of DPPSE to perform higher accuracy EP measurement than conventional ellipsometer is verified according to error analysis. 相似文献
922.
Jeffrey Chou Kyoungsik Yu David Horsley Brian Yoxall Sagi Mathai Michael R. T. Tan Shih-Yuan Wang Ming C. Wu 《Applied Physics A: Materials Science & Processing》2009,95(4):973-982
We present a free-space optical interconnect system capable of dynamic closed-loop optical alignment using a microlens scanner
with a proportional integral and derivative controller. Electrostatic microlens scanners based on combdrive actuators are
designed and characterized with vertical cavity surface emitting lasers (VCSELs) for adaptive optical beam tracking in the
midst of mechanical vibration noise. The microlens scanners are fabricated on silicon-on-insulator wafers with a bulk micromachining
process using deep reactive ion etching. We demonstrate dynamic optical beam positioning with a 700 Hz bandwidth and a maximum
noise reduction of approximately 40 dB. Eye diagrams with a 1 Gb/s modulation rate are presented to demonstrate the improved
optical link in the presence of mechanical noise. 相似文献
923.
Jyh-Liang Wang Yi-Sheng Lai Bi-Shiou Chiou Chen-Chia Chou Trent Gwo-Yann Lee Huai-Yuan Tseng Chueh-Kuei Jan Huang-Chung Cheng 《Applied Physics A: Materials Science & Processing》2008,90(1):129-134
Pulsed laser deposition (PLD) of (Pb,Sr)TiO3 (PSrT) film on Pt/SiO2/Si at low substrate temperatures (Ts), ranging from 300–450 °C, has been investigated. As Ts increases, the films reveal coarsening clusters, improved crystallization of the perovskite phase, distinct capacitance–electric
field (C–E) hysteretic loops and a larger dielectric constant. The 350 °C-deposited film shows strong (100) preferred orientation
and optimum dielectric properties with the dielectric constant of ∼620. The current density increases as the measurement temperature
and the electric field increase. Moreover, PSrT films exhibit a strong negative temperature coefficient of resistance (NTCR)
behavior at temperatures ranging from 100 to 390 °C.
PACS 81.15.Fg; 77.22.Ch; 68.60.Dv 相似文献
924.
Recently, p-terphenyls containing alkoxylated backbones with or without CN groups on either the central phenyl ring or peripheral rings were synthesized and their photo-luminescent properties were studied. Herein, semi-empirical AM1 and density functional theory (DFT) B3LYP calculations with the 6-31G* basis set have been performed to optimize structure for the ground state and the semi-empirical ZINDO calculations have been used to determine the maximum absorption (λabsmax) and emission wavelengths (λemi) for 19 p-terphenyls. The steric effect is assigned to be responsible for the calculated λabsmax and λemi shifts and the CN group at the central phenyl with ortho-substitution and at peripheral phenyl rings with para-substitution can also significantly influence these spectra. According to experimental results, the p-terphenyls with CN groups may have a lower energy of LUMO, and thus, we investigated the influence of the substitution position and the number of CN groups on the p-terphenyl moiety. The calculated optical and electronic properties provide important information on the behavior of the corresponding Organic light-emitting diode device (OLED). The suggested theoretical calculation protocol can be employed to predict electro-luminescent characteristics of other materials, and further, to design novel materials for OLED. 相似文献
925.
Here we report the observation of Fermi surface (FS) pockets via the Shubnikov-de Haas effect in NaxCoO2 for x=0.71 and 0.84, respectively. Our observations indicate that the FS expected for each compound intersects their corresponding Brillouin zones, as defined by the previously reported superlattice structures, leading to small reconstructed FS pockets, but only if a precise number of holes per unit cell is localized. For 0.71< or = x < 0.75 the coexistence of itinerant carriers and localized S=1/2 spins on a paramagnetic triangular superlattice leads at low temperatures to the observation of a deviation from standard Fermi-liquid behavior in the electrical transport and heat capacity properties, suggesting the formation of some kind of quantum spin-liquid ground state. 相似文献
926.
A two-dimensional phase-detection system for a surface-plasmon-resonance sensor is presented. The sensor utilizes polarization interferometry to detect phase differences between the s and p polarizations. We successfully detected a spatial phase-difference variation, resulting from the biomolecular interactions, of less than 1 x 1 mm(2). The phase stability demonstrated in the experimental results was approximately 0.09 degrees, and the corresponding change in the refractive index detection limit was approximately 4.3 x 10(-6). The common-optical-path configuration of the proposed method allowed us to reduce disturbances from ambient conditions. Furthermore, this method is capable of real-time array detection. 相似文献
927.
Spectral phase ripple associated with novel dispersive devices can distort broadband optical signals. We present a digital postprocessing algorithm to correct for this distortion by exploiting the static deterministic nature of the ripple. This algorithm is demonstrated with empirical data for several systems employing chirped fiber Bragg gratings (CFBGs). We employ this technique in a photonic time-stretch system incorporating CFBGs, improving the signal fidelity by 9 dB. Simulations and experiments show that this algorithm, which can be reduced to a simple interpolation and matrix multiplication, also mitigates additive noise. We see that the act of distortion correction yields signal fidelity superior to that of an ideal dispersive element. 相似文献
928.
Chung-Pin Chou 《Journal of Physics and Chemistry of Solids》2008,69(12):2944-2948
We use a variational approach with strictly strong-correlated constraint to gain insight into low-energy states of t-t′-t″-J model in the electron-doped regime. Compared with the recent results on the electron-doped cuprates obtained by angle-resolved photoemission spectroscopy (ARPES), we show that based on the long-range ordered antiferromagnetic metallic state prohibiting vacant sites, our results lead to qualitatively similar trends in ARPES spectra and Fermi surface topology. Additionally, the results about the evolution of the energy gap and spectral weight as a function of doping will be discussed. 相似文献
929.
Chou AS Wester W Baumbaugh A Gustafson HR Irizarry-Valle Y Mazur PO Steffen JH Tomlin R Yang X Yoo J 《Physical review letters》2008,100(8):080402
We report the first results of the GammeV experiment, a search for milli-eV mass particles with axionlike couplings to two photons. The search is performed using a "light shining through a wall" technique where incident photons oscillate into new weakly interacting particles that are able to pass through the wall and subsequently regenerate back into detectable photons. The oscillation baseline of the apparatus is variable, thus allowing probes of different values of particle mass. We find no excess of events above background and are able to constrain the two-photon couplings of possible new scalar (pseudoscalar) particles to be less than 3.1x10;(-7) GeV-1 (3.5x10;(-7) GeV-1) in the limit of massless particles. 相似文献
930.
The CoO2 layers in NaxCoO2 may be viewed as a spin S=1/2 triangular-lattice doped with charge carriers. The underlying physics of the cobaltates is very similar to that of the high T_(c) cuprates. We will present unequivocal 59Co NMR evidence that below T_(CO) approximately 51 K, the insulating ground state of the itinerant antiferromagnet Na0.5CoO2 (T_(N) approximately 86 K) is induced by charge ordering. 相似文献