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We present optical frequency combs with a spectral emission of 48 cm−1 and an output power of 420 mW based on a single-core quantum cascade laser at λ ∼ 8.7 μm. A flat top spectrum sustains up to 130 comb modes delivering ∼ 3.2 mW of optical power per mode, making it a valuable tool for dual comb spectroscopy. The homogeneous gain medium, relying on a slightly diagonal bound-to-continuum structure, promises to provide a broad and stable gain for comb operating. Remarkably, the dispersion of this device is measured within 300 fs2/mm to ensure stable comb operation over 90% of the total current range. The comb is observed with a narrow beatnote linewidth around 2 kHz and has weak dependence on the applied current for stable comb operation.

We present a high-pressure study of van der Waals ferromagnetic metal Fe3GeTe2 through electrical transport and Raman scattering measurements in diamond anvil cells at pressures up to 22.4GPa. Upon compression, the ferromagnetic transition temperature T c manifested by a kink in resistance curve decreases monotonically and becomes undiscernable around P c = 10GPa, indicative of suppression of the itinerant ferromagnetism. Meanwhile, by fitting the low temperature resistance to the Fermi liquid behavior of R = R 0 + AT 2, we found that R 0 shows a cusp-like anomaly and the coefficient A diverges around P c. These transport anomalies imply a tricritical point as commonly observed in itinerant ferromagnets under pressure. Unexpectedly, the Raman-active E 2g and A 1g modes soften remarkably after an initial weak hardening and the peak widths of both modes broaden evidently on approaching P c, followed by complete disappearance of both modes above this critical pressure. A possible underlying mechanism for such anomalous lattice softening near P c is discussed.

An approach considering both pairing and anti-pairing correlations in superdeformed (SD) states is proposed. Calculated results show that not only the general changing feature but also the turnover of dynamical moment of inertia with rotational frequency of the first SD band of 192Hg, 194Hg, and 152Dy are well described in the approach. It indicates that there exist competition, even change-over between the anti-pairing and pairing effects in the SD states in A ~ 190 and 150 ranges.

Effect of oxygen addition on diamond film deposition at higher pressure was studied. It was found that addition of oxygen suppressed diamond nucleation, and the effect of suppression increased with increasing pressure, and at certain pressure level diamond deposition was completely prohibited. Etching effect due to oxygen addition dominated at the very early stage (nucleation stage), therefore it is still possible to take the advantage of oxygen addition on quality improvement of diamond films by introducing oxygen after the nucleation stage.

By using the transfer matrix method, we present a general model for evaluating the ultrasonic scattering cross-section from a cylindrical multilayered medium. A numerical computation is given for an SCS-6/Ti fiber. This model can be conveniently used to estimate the ultrasonic scattering from a cylinder consisting of any number of layers.

The growth of GaAs epilayers on silicon substrates with a thin amorphous silicon (a-Si) buffer layer by metalorganic chemical vapor deposition is investigated in detail. Combining with the two-step growth method, the growth conditions of the a-Si buffer layer are optimized for growth of high-quality GaAs/Si epilayers. The a-Si buffer layer exhibits the best effect with thickness of 1.8 nm and growth temperature of 620°C. It is found that the introduction of this a-Si layer on Si substrates effectively reduces the dislocation density in GaAs/Si films. As compared with the dislocation density of 5 × 107 cm−2 in the GaAs/Si sample without the a-Si layer, a density of 3 × 105 cm−2 is achieved in the sample with the a-Si layer, and the defect reduction mechanism is discussed in detail.

The effect of Cu doping in Pt spacer layers on the magneto-optical properties of sputtered Pt/Co multilayers has been investigated. It was found that the polar Kerr rotation θk, ellipticity k, refractive index n and absorptive index k show an oscillation behavior as a function of the Cu content x, reflective index R keeps almost constant with the decreasing wavelength λ, three θk peaks appear at x = 0.03, 0.12, 0.25, respectively. Values of conductivity tensor σ1xx, σ2xx, σ1xy, and σ2xy in the PtCu layers have been derived from experimental θk, k, n, and k values at wavelength 770 nm. The oscillation of the polar Kerr rotation θk may be resulted from spin polarized quantum size effects in the PtCu layers.

The folding dynamics of a model of polypeptides is studied by Monte Carlo simulations. The effect of contacting probability between monomers is discussed. A specific temperature T* corresponding to the fastest folding process is found. At the temperature T*, the folding process appears more conservative than at other temperatures. In addition a cooperative characteristic, the length dependence of T*, is also illustrated. These show some instructive insights into the generic features of protein folding in nature.

The hexadecapole deformation parameter beta(4) Of the rare-earth and actinide nuclei is investigated in the framework of the sdg interacing boson model. An explicit relation between the geometric hexadecapole deformation parameter beta(4) and the intrinsic deformation parameters epsilon(4), epsilon(2) are obtained. The deformation parameters beta(4) of the rare-earths and actinides are determined without any free parameter. The calculated results agree with experimental data well. It also shows that the SU(5) limit of the sdg interacting bosom model can describe the beta(4) systematics as well as the SU(3) limit.

By using p-type polymer poly(2,5-Didodecyloxy-1,4-Phenylenylenevinylene) (PDDOPV) and n-type inorganic material ZnO:Zn, the electronluminescent (EL) emission from bilayer device based on polymer/inorganic heterojunction was successfully demonstrated. In comparison with single layer polymer device, with dc voltage of 10V, the brightness and luminous efficiency of bilayer device were enhanced 14 and 26 times, respectively. The EL spectrum of bilayer device is not identical to the characteristic emission spectrum of either PDDOPV or ZnO:Zn, and shifts continuously towards to short wavelength direction as the applied voltage increases.

Two series of Pt/Co multilayer films were sputtered under different deposition conditions. The magnetic and magneto-optical properties are found to vary depending on Pt bufferlayer and the number of modulation period. Fine material parameters of Pt/Co multilayers for magneto-optical recording are obtained.

Coherence resonance in a discrete excitable neuronal model with noises and time delays is investigated. The effects of the time delays on coherence resonance are revealed in two cases: Gaussian white and Gaussian color noises, respectively. The coefficient of variation of interspike intervals is calculated by numerical simulation. The results show that the coherence resonance is enhanced with the time delay increasing in the weak noises intensity cases, while there is no effect in the large noise intensity. Moreover, the coherence resonance can be held back by the self-correlation time, when the system is driven by a color noise.

The merit of a modern atomic clock is measured by its phase stability. A clock's absolute time-keeping uncertainty typically worsens over its operating time τ as Δτ ∝ √τ, with an Allan deviation of σy(τ) = Δτ/τ ∝ τ−1/2. Here we analyze a new class of self-referencing clocks, whose phase is locked to itself after a certain time delay. We show that the Allan deviation of such clocks decreases as 1/τ over a long and controllable operating time. This class of clocks can maintain synchronization over a prolonged period with only a fixed, almost non-increasing, absolute uncertainty, forming an ideal time-piece.

A new model is presented for Fano resonance in resonant grating structure based on the temporal coupled mode theory. By using this model, the reflection spectrum can be reproduced with the information of eigenmode of the structure, which can be numerically calculated by the finite element method. Therefore, the eigenmode plays a key role in determining the profile of the line shape of the Fano resonance in the resonant grating structure. When the space of two grating modulations is decreased, the line shape experiences a significant change. Such a drastic change can be attributed to the increase of quality factor of the eigenmodes. Thus, our model not only provides a simple and intuitive understanding on the mechanism of Fano resonance, but it also offers a convenient way to engineer the line shape of the Fano resonance. The proposed model can be used in many applications, such as biosensors, optical filters, and optical switchers.

We investigate the interacting new holographic dark energy (HDE) with viscosity. Specifically we not only study the dynamical evolutions of the new HDE with viscosity and the influences of viscosity as well as the coupling constant on the equation of state for the new HDE, but also establish the correspondence between the new HDE with viscosity and variable generalized Chaplygin gas (VGCG) models in the flat Friedmann—Robertson—Walker universe. Furthermore, we also reconstruct the potential and the dynamics of VGCG as the scalar field. By analysis we show that for the new holographic Chaplygin gas model, if the related parameters to the potential satisfy some constraints, the accelerated expansion can be achieved. These research results can reduce to the ones without viscosity.

Anatase TiO2 films are deposited on glass substrates at different oxygen partial pressures of 0.8–1.6 Pa. Room temperature N ion implantation is conducted in the films at ion fluences up to 5 × 1017 ions/cm2. UV-visible absorption and photoluminescence (PL) are investigated. With the increase of N ion fluences, the band gap of TiO2 decreases and the absorbance increases. X-ray photoelectron spectroscopy (XPS) confirms the formation of O-Ti-N nitride after implantation, resulting in the red shift of the band gap. The PL intensity of the deposited films increases with the increasing oxygen partial pressure and decreases remarkably due to the irradiation defects induced by ion implantation.

A compact temperature sensor based on a symmetrical metal-cladding optical waveguide using free-space coupling is proposed and demonstrated theoretically and experimentally. The symmetrical Au-cladding optical waveguide is based on a thin LiNbO3 slab sandwiched between two metal films, which serve as the coupling layer and reflecting panel, respectively. The sensitivity of this sensor of 9.08 × 10−2 deg/°C, 6.6 × 10−2 deg/°C and 4.8 × 10−2 deg/°C corresponding to 3238-order, 3237-order and 3236-order modes, respectively, are obtained. Higher resolution is predicted with a larger linear expansion coefficient material and a higher resolution θ/2θ goniometer.

The morphological evolution of a-GaN deposited by metalorganic chemical vapor deposition (MOCVD) on r-sapphire is studied. The influences of V/III ratio and growth temperature on surface morphology are investigated. V-pits and stripes are observed on the surface of a-GaN grown at 1050°C and 1100°C, respectively. The overall orientation and geometry of V-pits are uniform and independent on the V/III molar ratio in the samples grown at 1050°C, while in the samples grown at 1100°C, the areas of stripes decrease with the adding of V/III ratio. We deduce the origin of V-pits and stripes by annealing the buffer layers at different temperatures. Because of the existence of inclined (101) facets, V-pits are formed at 1050°C. The (101) plane is an N terminated surface, which is metastable at higher temperature, so stripes instead of V-pits are observed at 1100°C. Raman spectra suggest that the growth temperature of the first layer in the two-step process greatly affects the strain of the films. Hence, to improve the growth temperature of the first layer in the two-step method may be an effective way to obtain high quality a-GaN film on r-sapphire.

Semi-polar ZnO (1011) epitaxial films are demonstrated using a methanol oxidant by metalorganic chemical vapor deposition on Si (111) substrates at 500°C. X-ray scanning indicates that there are six kinds of in-plane domain growths, with the ZnO [1012] parallel to the Si (112) direction families. The crystallographic orientation of ZnO is supposed to be caused by surface passivation. The methanol, as a polar molecule, may be adsorbed on the Si (111) surface to form a passivation layer, which inhibits the (0001) ZnO plane deposition on the substrate surface, and as a result the ZnO (1011) plane becomes preferred. The optical properties, examined by a room-temperature photoluminescence spectrum, exhibit a strong near-band-edge emission peak at 379 nm, indicating that the (1011) ZnO film has good crystal quality. These results are significant for research into and for the applications of semi-polar ZnO films.

The phenomenon of vibrational resonance (VR) in an overdamped system with a sextic double-well potential under the excitation of two different periodic signals is investigated. The approximate analytical expression of the resonance amplitude Q at the low-frequency ω is obtained. The VR is observed, and the values of B (the amplitude of the high-frequency signal) and Ω (the frequency of the high-frequency signal) at which VR occurs are determined. Moreover, the relationship between B and Ω is revealed. The theoretical predictions are found to be in good agreement with the numerical results.

We propose a scheme to implement quantum information transfer between Cooper-pair boxes (CPBs) in a circuit quantum electrodynamic (QED) system with Landau—Zener tunneling. The system consists of two CPB qubits and a one-dimensional transmission line resonator (TLR). By analytically solving the eigenequation and numerically calculating the transition probability, the results show the quantum state transfer from one qubit to another via a fast adiabatic passage. The coupling mechanism is robust against decoherence effects.

Dipolar and quadrupolar resonance wavelengths of SiO2/Au nanoshell surface plasmons are designed at 560 nm to enhance the light trapping in thin film solar cells. In order to quantitatively describe the light trapping effect, the forward-scattering efficiency (FSE) and the light trapping efficiency (LTE) are proposed by considering the light scattering direction of SiO2/Au nanoshells. Based on the Mie theory, the FSE and the LTE are calculated for SiO2/Au nanoshells of different dimensions, and the contributions of the dipolar and quadrupolar modes to the light trapping effect are analyzed in detail. When the surface coverage of nanoshells is 5%, the LTEs are 21.7% and 46.9% for SiO2/Au nanoshells with sizes of (31 nm, 69 nm) and (53 nm, 141 nm), respectively. The results indicate that the SiO2/Au nanoshell whose quadrupolar mode peak is designed to the strongest solar energy flux density of the solar spectrum facilitates the further enhancement of light harvesting in thin film solar cells.

We prepare an etched gate tunable quantum dot in single-layer graphene and present transport measurement in this system. We extract the information of the ground states and excited states of the graphene quantum dot, as denoted by the presence of characteristic Coulomb blockade diamond diagrams. The results demonstrate that the quantum dot in single-layer graphene bodes well for future quantum transport study and quantum computing applications.

Aiming at the problem of luminance uniformity for injection electroluminescent display panels, we present a new scan method for display panels according to successive scans theory. First, on the basis of the number of pixels requiring light emitting in one frame period, we adjust the scan time for each row. Secondly, for ensuring image transmission synchronization, the frame period must to be a constant. We adopt a 64 × 32 LED display panel as an example to expound the new scan method and we obtain the good result that the reduce amplitude of luminance non-uniformity is 31.34% and the increase amplitude of the average luminance value is 7.8258%.