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One piece of single-mode silica fibre is used to study of temperature characteristics of stimulated Raman scattering (SRS), additional peaks (double-humped) are observed at both sides of pump light and 1st-order Stokes light in the experiment. The frequency shift of the double-humped is calculated by stimulated Four–Photon mixing (SFPM) phase matching theory, the result is consistent with the frequency shift of this experiment. Simultaneously, the experimental conditions accord with the theoretical calculation of effective coherence length. We indicate that the double-humped phenomenon is caused by SFPM. The intensity of double-humped is first increased, then decreased and finally disappeared as the temperature increases. This phenomenon has been explained theoretically.

A new structure of highly birefringent honeycomb photonic bandgap fibres (PBGFs), including an elliptical air hole in its solid core, is proposed and analysed by using full vectorial plane wave expansion method. From the numerical results it is confirmed that the proposed PBGF has birefringence of the order of 10−3. Moreover, there are two single-polarization single-mode ranges at varying normalized wavelength, in one of which only the slow-axis mode exists, and in the other only the fast-axis mode exists, which has not been achieved in index-guiding photonic crystal fibres so far.

Effects of draw parameters, such as drawing temperature and feed speed, on the capillaries and the geometry of the final photonic crystal fibre (PCF) are investigated. Inert gas pressurization is introduced in the preform during the fibre drawing process to finely control the geometry of the PCF so that good uniform in transversal and longitudinal of the final PCF can be realized. Due to the introduction of a special method, the drawing temperature is increased over 1900°C and the strength of the PCF is enhanced.

A new type of THz waveguides, which employs a solid polyethylene rod as the core and polyethylene tubes in a periodic array of square lattice as the cladding, is proposed. Optical properties of this new THz waveguide, especially in dispersion, confinement loss and single mode property, are investigated in detail with the plane wave expansion method and the beam propagation method. Numerical results demonstrate that the new THz waveguide can reach not only low dispersion but also low confinement loss at single mode propagation. Therefore, the square lattice structure is a better candidate as THz waveguides than the triangular ones.

Deformation of some air holes often occurs during the fabrication process of photonic crystal fibres (PCFs). Effects of the location and size of deformation holes on the properties of actual triangular lattice PCFs are investigated in detail. Numerical results demonstrate that the properties of PCFs, especially birefringence, are sensitive to the location and size of deformation holes. These would be very helpful to improve the fabrication technique of the PCF and also offers an efficient way to design high birefringence PCF.

We propose a new type of high flexible single-polarization single-mode (SPSM) photonic crystal fibre (PCF). Numerical analysis indicates that the SPSM PCF proposed guides only one polarization mode over a wavelength band broader than the conventional SPSM fibres. The position and the bandwidth of the single polarization mode region depend flexibly on the structure parameters such as the hole diameters d1 and d2 and the hole pitch Λ of the SPSM PCFs. A 200-nm SPSM region can be obtained for the SPSM PCF with Λ = 2.55 μm, d1/Λ = 0.3 and d2/Λ = 0.833 and the modal birefringence at the wavelength 1.31 μm can reach 1.8×10−3.

Nanocrystalline porous TiO2 films were prepared on conducting glass supports (ITO) by processed commercial TiO2 nanometre powder (P25). Three methods of physical dispersing for TiO2 powder, i.e. grinding, magnetic stirring, sonicleaning, were used to disperse TiO2 nanometre powder. Surface morphologies of TiO2 films were observed by optic-microscope and SEM. It is found that the surface morphologies of TiO2 films are determined not only by the dispersing methods but also by the percentage of TiO2 powder in the dispersing system. Different film morphologies can be obtained under the same preparation condition but with different dispersing methods. A lot of cracks exist on the film surface for which the TiO2 slurry is dispersed by grinding. Magnetic stirring leads to some white points and micro-holes on the film surface. Only a few of micro-holes can be observed on the film surface, in which the TiO2 slurry is dispersed by sonicleaning. Different surface morphologies can also be found with different thicknesses of TiO2 films. Different film thicknesses are due to different percentages of TiO2 powder in the slurry. The related mechanism leading to different features of the surface morphologies for the TiO2 films is discussed.

An ultra broadband single-polarization single-mode (SPSM) photonic crystal fibre (PCF) is proposed and analysed by using the plane-wave expansion method and the beam propagation method. Numerical results demonstrate that the SPSM wavelength region nearly at 580 nm in width from 1.46 μm to 2.04 μm is obtained in this PCF. The start wavelength of the SPSM region is close to the hole pitch, and the width of the SPSM region increases with the increasing hole pitch. Effects of dopant concentration on SPSM properties are investigated. The confinement loss decreases and the width of SPSM region widens slightly with the increasing dopant concentration. These results offer a new possibility of fabricating active doped SPSM PCFs with high performance that is crucial for improving the performance of linearly polarized fibre lasers.

Giant magneto-impedance effects have been observed in as-deposited amorphous FeCuNbSiB/Cu/FeCuNbSiB and FeCuNbSiB/SiO2/Ag/SiO2/FeCuNbSiB multilayered films. The films were deposited onto Si substrates by radio frequency sputtering. In FeCuNbSiB/Cu/FeCuNbSiB films, maximum giant magneto-impedance ratios as large as 32% and 11% were obtained at 13 MHz in the longitudinal and transverse fields, respectively. In FeCuNbSiB/SiO2/Ag/SiO2/ FeCuNbSiB films, the maximum giant magneto-impedance ratios were 47% and 57% at the same frequency for the two cases, which are much larger than those obtained in the annealed single layer films.

GaP nanocrystals were synthesized by both the organic solvent reflux and high temperature high pressure benzene thermal synthesis methods. The effect of organic solvent on the optical absorption properties of GaP nanocrystals were studied. The results show that crystal grains of the sample synthesized by the latter method have better quality and uniformity. The solvents which consist of polar molecules and form strong chemical bonds with Ga atoms cause obvious redshift of the absorption spectra of GaP nanocrystals. The absorption spectra redshift much more if the solvent molecules have ? electrons which involved in the formation of complex bond between Ga atoms and solvent molecules.

Structural properties and thermodynamic properties of amorphous SiO2(a-SiO2) and amorphous SiO2 with an oxygen defect center (a-SiO2-ODC) are investigated by using interatomic pair potentials. Amorphous configurations of SiO2 glass are constructed by quenching using the molecular-dynamics method and subsequent relaxation using the first-principles method. The numerical result demonstrates that the calculated short-range structural parameters coincide well with the previous experimental and theoretical results reported. The thermodynamic properties including specific heat, Debye temperature, vibrational entropy, and so on are analyzed by calculating the phonon density. Furthermore, mechanical properties of both structures are obtained.

FexGe1?x/Ge amorphous heterojunction diodes with p-FexGe1?x ferromagnetic semiconductor layers are grown on single-crystal Ge substrates of p-type, n-type and intrinsic semiconductors, respectively. The I?V curves of p-Fe0.4Ge0.6/p-Ge diodes only show slight changes with temperature or with magnetic field. For the p-Fe0.4Ge0.6/n-Ge diode, good rectification is maintained at room temperature. More interestingly, the I?V curve of the p-Fe0.4Ge0.6/i-Ge diode can be tuned by the magnetic field, indicating a large positive magnetoresistance. The resistances of the junctions decrease with the increasing temperature, suggesting a typical semiconductor transport behavior. The origin of the positive magnetoresistance is discussed based on the effect of the electric and magnetic field on the energy band structures of the interface.

We theoretically and experimentally study the relationship between Fermi resonance and solvent effects and investigate the Fermi resonance of p-benzoquinone and cyclopentanone in different solvents and the Fermi resonance of CS2 in C6H6 at different concentrations. Also, we investigate the Fermi resonance of C6H6 and CCl4 in their solution at different pressures. It is found that solvent effects can be utilized to search Fermi resonance parameters such as coupling coefficient and spectral intensity ratio, etc., on the other hand, the mechanism of solvent effects can be revealed according to Fermi resonance at high pressure.

We introduce a defect site in the periodic structure of a photonic bandgap fiber, to confine and guide the second order mode by photonic bandgap effects. Based on a high air-filling fraction photonic crystal cladding structure, a simplified model with an equivalent air cladding was proposed to explore and analyze the properties of this second order guided mode.

We used a terahertz time-domain spectroscope (THz-TDS) to detect the reversible conformational changes of PsbO protein induced by N-bromosuccinimide and Guanidine Hydrochloride. The veracity and sensitivity are confirmed by the fluorescence emission spectra. The results demonstrate that THz-TDS has both advantages and disadvantages in monitoring the denaturation process of proteins, which is important in applying THz-TDS technique to studying biomolecules.

The properties of meso-tetraphenylporphine (TPP) aggregates formed in acidic aqueous-organic solutions are investigated by UV-vis spectroscopy. According to the absorption spectra, the Q band absorption of the aggregated TPP shows red shift and intensity enhancement, and a model that includes the participation of water molecules in a porphyrin aggregation complex is proposed, then a qualitative explanation based on Gouterman's excition coupling theory is presented. Calculations including eigenenergies, eigenstates and the transition dipole strength of the coupled states are carried out.

High-pressure Raman studies at room temperature are performed on CCl4 up to 13 GPa. The Raman bands of the internal modes (v2, v4 and v1) show entirely positive pressure dependence. The slopes dω/dP of the internal modes exhibit two sudden changes at 0.73 GPa and 7.13 GPa, respectively. A new lower frequency mode (225 cm−1) appears at 3.03 GPa, and the splitting of v2, v3 and v4 occurs at about 7.13 GPa. Moreover, Raman spectra of Fermi resonance show that the relative position of the v1 + v4 combination and the v3 fundamental firstly interchanges corresponding to that at ambient pressure, then the v1 + v4 combination disappears in the gradual process of compression. It is indicated that the pressure-induced phase transition from CCl4 II to CCl4 III occurs at 0.73 GPa, and CCl4 III undergoes a transition to CCl4 IV below 3.03 GPa. Further CCl4 IV transforms in a new high-pressure phase at about 7.13 GPa, and the symmetry of the new high-pressure phase is lower than that of CCl4 IV. All the transitions are reversible during decompression.

A low-loss criterion for bend transitions in optical fibers is proposed. An optical fiber can be tightly bent with low loss to be adiabatic for the fundamental mode, provided that an approximate upper bound on the rate of change of bend curvature for a given bend curvature is satisfied. Two typical adiabatic bend transition paths, the optimum profile and linear profile, are analyzed and studied numerically. A realizable adiabatic transition with an Archimedean spiral profile is introduced for low bend loss in tightly bent optical fibers. Design of the transitions is based on modeling of the propagation and coupling characteristics of the core and cladding modes, which clearly illustrate the physical processes involved.

Longitudinal and transverse magneto-impedance effects have been observed in amorphous FeCuNbSiB films made by radio frequency sputtering. Large magneto-impedance values have been obtained at lower frequencies. The field dependence and frequency dependence of the magneto-impedance are studied. The field dependence of effective permeability μe is also discussed.