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Zn1-xMgxO films have been deposited on Al2O3(0001) substrates at different oxygen pressures by using pulsed laser deposition method. The influence of oxygen pressure on the crystal quality and optical properties of the films is studied with X-ray diffraction (XRD), transmittance spectra, and photoluminescence (PL). It is found that the crystal quality of the films lowers with increasing of oxygen pressure from 10-4Pa to 10 Pa. At the pressure of 10-4 Pa, the epitaxial relationship between the film and sapphire substrate is determined to be ZnMgO (0001)// Al2O3(0001),ZnMgO 1010]//Al2O3 1120]. In the oxygen rich environment, however, another epitaxial relationship, ZnMgO (0001)//Al2O3(0001) and ZnMgO 1010]//Al2O3 1010], is also present in the films, which is suggested to be responsible for the decline of the crystal quality. Compared with pure ZnO films, the UV peak of Zn1-xMgxO alloys shows red-shift from 3.374 to 3.332 eV with increasing oxygen working pressure increasing from 10-4 Pa up to 10 Pa. The difference in red-shifts can be attributed to the decrease of Mg content in the films resulting from the variation of oxygen pressure. A broad UV PL spectrum was observed at 10 K in the films deposited under different pressures and can be decomposed into two recombination processes of excitons, corresponding to the bound and the localized exciton luminescence, respectively. The binding energy of bound excitons in the ZnMgO films is larger than that in pure ZnO and has an increasing trend with increasing oxygen pressure.

ZnO/MgO multi-quantum wells with modulation structure are grown on oxidated Al2O3 （0001） substrates using radio-frequency reactive magnetron sputtering method. X-ray reflectivity and X-ray diffraction measurement，electronic probe，atom force microscopy，transmission spectrum and PL spectrum are used to characterize the samples. The XRD scan and phi-scan results show the films are highly （001） textured and have epitaxial relationship with the substrates. The width of quantum well is determined to be between 838 nm and 2178 nm by XRR and EPMA. The AFM results show that the RMS roughness of the MQWs increases from 64 nm to 212 nm with the decrease of period of modulation. Low temperature PL spectrum shows the peak can be assigned to the radiative recombination of bound excitons，and the activation energy is estimated to be about 30 meV. The emission due to spatially separated carriers caused by quantum-confined Stark effect is also found in the spectrum of sample with smaller well width.

The vertical-cavity surface-emitting laser（VCSEL） has proved to be a low cost light source with attractive properties such as surface emission, circular and low divergence output beam, and simple integration in two-dimensional array. Many new applications such as in spectroscopy, optical storage, short distance fiber optic interconnects, and in longer distance communication, are continuously arising. Many of these applications require stable and single-mode high output power. Several methods that affect the transverse guiding and/or introduce mode selective loss or gain have been developed. In this study, a method for improving the single mode output power by using metal surface plasmons nanostructure is proposed. Theoretical calculation shows that the outpout power is improved about 50% compared to the result of standard VCSELs.

Surface plasmons（SPs） generated in nano metallic gratings on medium layer can greatly enhance the transmission field through the metallic gratings. The enhancement effect is achieved from λ=500 nm to near-infrared domain. The enhancement rate is about 110% at the wavelength of about 610 nm and about 180% at λ=700 nm and 740 nm where most kinds of thin film solar cells have a high spectral response. These structures should provide a promising way to increase the coupling efficiency of thin film solar cells and optical detectors of different wavelength response.

We presented a comparison of magnetic properties of ［Cot/Fe3t］5 (t=2, 3, 4, 5nm) multilayers prepared by DC magnetron sputtering on glass and Si substrates. For the multilayers with the same t but prepared on different substrates, it was found that the saturated magnetization differed little, but the coercivity differed greatly. Moreover, the difference in coercivity mechanism was analyzed theoretically to explain this difference.

Transmission of electromagnetic wave in a heavily doped n-type GaAs film is studied theoretically. From the calculations, an extraordinary transmission of p-polarized waves through the film with subwavelength grooves on both surfaces at mid-infrared frequencies is found. This extraordinary transmission is attributed to the coupling of the surface-plasmon polariton modes and waveguide modes. By selecting a set of groove parameters, the transmission is optimized to a maximum. Furthermore, the transmission can be tuned by dopant concentrations. As the dopant concentration increases, the peak position shifts to higher frequency but the peak value decreases.

Based on the theory of third-order nonlinear Kerr effect in optical fiber, we experimentally demonstrate the generation of photon pairs by exploiting spontaneous four-wave mixing. The photon pairs are produced by pumping a fiber Sagnac loop and a piece of straight fiber with a pulsed laser, respectively. By comparing the experimental results, we analyze how to optimize the experimental parameters to obtain entangled photon pairs with high purity. Our results are useful for developing the all-fiber source of photon pairs and single photon source, which are well suited for quantum communication.

Surface plasmon modulated nano-aperture vertical-cavity surface-emitting lasers were fabricated from common 850nm VCSELs. When the diameter of the aperture was 200nm, and the period of grating was 400nm, the maximum far-field output power reached 0.3mW at a driving current of 15mA. The fabrication process was described and the beaming properties were studied via experimentally and theoretically.

We investigate the surface plasmon polaritons and its coupling with other electromagnetic modes by observing the absorption spectrum on a system of dielectric spherical shells periodically mounted in a metal substrate. We found that there exist two resonance frequencies in the system corresponding to surface plasmon polaritons mode and cavity mode. At these frequencies, we can find related peaks in absorbance. Since the surface plasmon polaritons cannot couple with the incident plane wave directly and both couplings of the cavity mode with the incident wave and the surface plasmon polaritons are also weak, so the strength of absorption peaks are generally very limited. However, we can adjust some parameters in the system to make the surface plasmon polaritons and the cavity mode with almost the same frequency. In this case, the coupling can be dramatically enhanced, and we can observe very strong peaks in absorbance. The relationships of resonance absorption with some physical and geometrical parameters are discussed in detail.

The frequency and temperature dependence of the hysteresis loops in Pb［(Zr0 52Ti048)095(Mn1/3Nb2/3)005］O3 (PM nN_PZT) ceramics have been investigated. It has been demonstrated that the polar ization_field hysteresis curves show “pinched" shapes instead of the normal squ are_like P_E loops when tested at room temperature or higher frequency. While at 200℃ or lower frequency, normal square_like loops are observed. In the meantim e, important ferroelectric features such as coercive field, polarization and int ernal bias field are strongly frequency or temperature dependent. High increase of the remnant polarization (Pr) reveals that there may be defect dipo les that induce the unsaturated hysteresis loop. The close relations between the P_E loops and the applied frequencies or temperatures indicate that there exist s a typical relaxation time associated with reorientation of the defect dipoles.

The structural and magnetic properties of Pt1-xCux/Co multilayers have been investigated. Increasing the concentration of Cu in the Pt spacer layers results in monotonic decrease of the anisotropy and remanence, in a range of x from 0.04—0.30 except in a special range of 0.10—0.15. The reduction of these parameters is related to the growth of random anisotropy because a random distribution of Cu atoms in the Pt spacer layers causes a local distortion of crystal symmetry of Pt. In the special range, an order CuPt phase may appear. In such a case cobalt atoms are affected by a symmetric crystal field like that produced by Pt. These may be the possible explanation of the measured parameters after the doping of Cu in the Pt spacerlayers.

Spontaneous shrinking of the second type of dumbbell domains (IID) subjected to both static bias field (Hb) and in-plane field (Hip) were investigated experimentally.It was found that this phenomenon depends on the amplitude,as well as the direction of Hip.In terms of a series of photographs,it was shown that the spontaneous shrinking of those IIDs perpendicular to Hip occurs earlier,and the spontaneous shrinking of those IIDs parallel to Hip occurs later.In addition,it was confirmed that IIDs lose a part of vertical Bloch lines (VBLs) in their walls in the process of spontaneous shrinking.

The influence of temprature T on the critical in-plane magnetic field range forthe break-down of vertical Bloch line(VBL)chains within the stripe Bloch domainwalls with ordinary hardness in magnetic bubble films of LPE garnet is studiedexperimentally,We find that there exist two characteristic tempratures,and with the former slightly lower than the latter and both higher than room tempratureTr,such that at any T∈[T,] there is a T-dependent critical range,of in-plane magnetic field H_ip: all VBLs keep stable when H_iPVBLs disappear gradnally as H_ip increases when H_iP￣(1) (T)H_iPH_iP￣(2) (T),no VBL remains when H_iPH_iP ￣(2)(T), The lower and upper limits as well as thewidth of the critical in-plane field range all decrease as T increascs,and the for-mer two reach zero at and respectively.The ratio incr-eases with temperature elevating, slowly at lower T including T:where this ratiois about and rapidly near.Some theoretical arguements are presented.

The erasing process of stripe domains in (111)-oriented garnet bubble films was investigated experimentally in the presence of both an in-plane field Hin and a static bias field Hb. As Hb was kept constant and Hin was raised, the stripe domain erasing field Hs* and the bubble domain erasing field Hk* were measured as functions of the azimuthal angle β of the in-plane field. Taking the cubic magnetocrystalline anisotropy into account, we established a theory of stability of stripe domains subjected to both an inplane field and a static bias filed. The main features of the experimental results can be explained qualitatively by this theory. The angle at which both white and black domains are erased at the same time was obtained as βn=1/3(2nπ±arc cos│3/(21/2)(MsHb)/K1│)(n=0,±1,±2,…) which is in reasonable agreement with the experiments.

The dependence of the magnetic torque of single crystal GGG (Gd3Ga5O12) substrates on their geometry and some related physical parameters were studied. A method was proposed to deduce the substrate contribution in determining the uniaxial anisotropy constant Ku and magnetocrystalline one K1. Both Ku and K1 can be acquired from the magnetic torque curves by employing the two-variable regression and using computer. As example, the measured curves of Ku and K1 as a function of temperature were presented.

The criterion of classification for three kinds of hard domains with lots of VBLS in their walls in garnet bubble materials is proposed. Their formation and static characteristics are described in detail and their typical pictures are shown. Considering the formation conditions of hard domains, it is reasonable to deduce that the increase of the number of VBLs in their walls leads to substantial change of their static characteristics.

The temperature dependence of VBL group formation in stripe domain walls of epitaxial garnet bubble films was investigated by means of the method of single-pulse bias field. A critical temperature T02 was found, which relats to the parameters of bubble films. When T >T02, hard bubbles no longer form. It was also found that, when T02, there are two different stages for VBL group formation. Their demarcation temperature is T01. The experimental curves in the first stage have been qualitatively interpreted. And the difference of soft domain segment movements, which lead ro their hardening, in the two stages has been revealed by means of the method of double exposure photography.

The erasing process of stripe domains in eight (111)-oriented garnet bubble films was observed in the presence of an in-plane field. The stripe domain erasing field H*s and the domain erasing field H*_k were measured as functions of the azimuthal angle βof the in-plane field. Taking the cubic magnetocrystalline anisotropy into account, a theory of stability of stripe domains subjected to an in-plane field was developed. The main features of the experimental results can be expained qualitatively by this theory. Two theoretical relationships between H*s and βas well as K_1 were found. They are applicable to the cases that the direction of in-plane field is near and not fairly near the 〈110〉 crystallographic axes respectively, and are found to be roughly consistent with the experimental results. In particular, along the 〈110〉axes an analytical expression was obtained: H_(k〈110〉)~* =H_(s〈110〉)~*=H_k{1+ K_1/2k_u-[al/h(4pM_s/H_k)~2]~(2/3)}, which is in good agreement with the experiments.

The formation of hard bubbles by single-pulse bias field in epitaxial garnet films was investigated in some detail. It was verified by experiments and calculations that, in general, VBL in hard bubble walls are not generated by the way that one Bloch line pair is produced per pulse. The dependence of the hardening of soft domain segments on their movements was revealed by means of the method of double exposure photography. Two kinds of favorite movements for hard bubble formation were discovered and the physical meaning of the" demarcation field for soft and hard bubble formation" H[b] was elucidated.

The influence of in-plane fields on the formation of hard bubbles in epitaxial garnet films by using single-pulse bias field was investigated in some detail. A critical in-plane field H0in which is related to the parameters of bubble films, was discovered. When Hin>H0in, formation of hard bubbles no longer occurs. Three physical processes, i.e. the increase, quick decrease and slow decrease of the demarcation field for soft and hard bubble formation H[b] with in-plane fields can be qualitatively interpreted in terms of the effect of in-plane field on stripe domains, as well as the formation of multifingered domains.

Hard bubbles and hard wall segments will transform into normal ones, if an in-plane field is larger than a threshold value Hin. We measured the Hin values for some as-grown magnetic bubble materials. As d.c, magnetic bias field perpendiculer to the film increases, Hin decreases. It has been shown that the transformation from hard bubbles and hard wall segments into normal ones is a relaxation proccess which may last for a few seconds or more. The above results were explained qualitatively in terms of the concept of field-nucleated Bloch points suggested by Slonczewski and Maloze-moff.

The influence of temperature on ordinary hard bubbles and their corresponding hard stripe domains in epitaxial garnet bubble films was investigated experimentally, A critical temperature T0, which is related to the parameters of bubble films, was found. When the testing temperature T0, the VBL chains in hard domain walls are not changed after temperature increasing and then decreasing. When T>T0, however, the VBL chains disappear, so that all of hard domains become soft. When VBLs in walls are compressed, the harder the domain, the lower its softening temperature. During softening, the way of VBL disappearance is a sudden break down of the whole chain.

The formation of hard bubbles (including dumbbell domains) in epitaxial garnet films by using a series of pulse bias fields was investigated in some detail. It was found that the effect of a series of pulses is not simply the adding up of that of a single pulse (the physical process of hardening of soft domain segments), but has its own regularity, there exist two other physical processes, i.e. further hardening and softening of hard domain segments. The experimental results can be reasonably interpreted in terms of the above-mentioned three processes.

The correlations between the Raman band intensities, concentrations, refractive indices and the absorption frequency of benzene were studied by measuring the integrated intensities of the Raman band 992 cm -1 of benzene in 8 solutions of different concentrations and the refractive indices of the solutions. It is shown that the intensity deviation is proportional to the difference between the refractive index of the solution and that of pure benzene. The band intensities of different solutions depend linearly on their refractive indices, that is, the intensity does not depend on the nature of the solvent, but on its refractive index. The relationship between the band intensities and the resonance frequency factors of benzene in the solutions is also linear. The experimental results are discussed from the point of view of perturbation of the medium on the electronic absorption band.