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981.
We propose and demonstrate a simple technique for determining the M/# parameter of a holographic recording material. In this method, divergent object and reference beams are used to produce a spatially varying index modulation. One can analyze the resultant diffraction pattern to find M/# by using only a single grating; existing techniques require many gratings. 相似文献
982.
Tandon SN Gopinath JT Shen HM Petrich GS Kolodziejski LA Kärtner FX Ippen EP 《Optics letters》2004,29(21):2551-2553
Broadband saturable Bragg reflectors (SBRs) are designed and fabricated by monolithic integration of semiconductor saturable absorbers with broadband Bragg mirrors. The wet oxidation of AlAs creates low-index AlxOy layers for broadband, high-index-contrast AlGaAs/AlxOy or InGaAlP/AlxOy mirrors. SBR mirror designs indicate greater than 99% reflectivity over bandwidths of 294, 466, and 563 nm for center wavelengths of 800, 1300, and 1550 nm, respectively. Highly strained and unstrained absorbers are stably integrated with the oxidized mirrors. Large-scale lateral oxidation techniques permit the fabrication of SBRs with diameters of 500 microm. Large-area, broadband SBRs are used to self-start and mode lock a variety of laser systems at wavelengths from 800 to 1550 nm. 相似文献
983.
An antimony--germanium- (Sb--Ge-) codoped fiber specially designed for the fabrication of fiber Bragg gratings (FBGs) with high temperature sustainability has been developed. The photosensitivity and the high-temperature sustainability of FBGs that have been written into this fiber were tested. The results obtained showed that the FBG written into this fiber has a very high temperature sustainability of 900 degrees C. A decay mechanism that involves cation hopping is presented to explain the observed high temperature sustainability of the grating written into this fiber. 相似文献
984.
Grazing incidence x-ray diffraction study of Fe epitaxial ultrathin films (1.5-13 nm) on GaAs (001) reveals an anisotropy of both domain shape and strain, with [110] and [1-10] as the principal directions. It is shown that the observed thickness-dependent strain anisotropy, together with a uniaxial interface term, can provide an unambiguous explanation to the usual in-plane magnetic anisotropy and its thickness dependence observed in this magnetic thin-film system. 相似文献
985.
Electrical poling induces polar ordering of molecules in a grating that has been holographically inscribed on a thin film of polymer with azobenzene side chains. The resulting chi2 grating, seen by second-harmonic-generation (SHG) near-field scanning optical microscopy, can have a periodic structure that is significantly different from the topographical image. The far-field linear and SHG diffration patterns correlate well with the grating structures. Poling of the thin-film grating, which presumably has photodriven nonuniform material properties within each period, leads to the more complex structure of the chi2 grating. 相似文献
986.
Shahriar MS Tripathi R Kleinschmit M Donoghue J Weathers W Huq M Shen JT 《Optics letters》2003,28(7):525-527
We describe a superparallel holographic optical correlator that performs two-dimensional spatial and angular multiplexing simultaneously. The key step in this architecture is the use of a holographic multiplexer to split a query image into many copies before it applies them to the holographic database. A holographic demultiplexer, in conjunction with an aperture, is used to identify the location and the angle of the brightest correlation peak. This architecture uses only O(square root of N) detector elements to search through N unsorted images in a single query. We demonstrate the basic features of this architecture, using three spatial locations with eight angle-multiplexed images in each location. 相似文献
987.
Farnan GA Fu CL Gai Z Krcmar M Baddorf AP Zhang Z Shen J 《Physical review letters》2003,91(22):226106
We report a surprising observation that the growth of the [Fe(1 ML)/Co(1 ML)](n) superlattice of L1(0) structure on Cu(100) is stable only up to six atomic layers (n=3), which cannot be rationalized by stress arguments. Instead, first-principles calculations reveal a transition from the L1(0) to the B2 structure due to the effect of dimensionality on the stability of the electronic structure of the superlattice. Whereas the majority-spin electrons are energetically insensitive to the layer thickness, the minority-spin electrons induce the transition at n=3. 相似文献
988.
The entropy of Einstein—Maxwell-dilaton—axion black holes is calculated by using the improved brick-wall model. Taking into account of the statistical physics, we propose not to consider the superradiant modes. The result shows that the nonsuperradiant modes do contribute exactly the area-law entropy for extreme black hole. Moreover, our cut-off which does not require an angular cut-off is independent of angle . As for the extreme black hole, we found that its entropy is zero. 相似文献
989.
J.P. Zou Y.F. Mei J.K. Shen J.H. Wu X.L. Wu X.M. Bao 《Applied Physics A: Materials Science & Processing》2003,77(6):855-858
A SiO2 nanoscale island array was fabricated on a Si substrate by using anodic porous alumina as a mask. Transmission electron microscopy observation and the atomic force microscopy pattern show that the arrangement of SiO2 islands has a quasi-hexagonal symmetry. Ge ions with a dose of 1×1017 cm-2 were subsequently implanted into the SiO2 island array to form Ge-related light-emitting centers. The photoluminescence (PL) spectra of as-implanted and annealed samples show three PL bands at 370, 400 and 415 nm. Their intensities reach maximums in the sample with an annealing temperature of 700 °C. Spectral analysis suggests that the 370 and 415 nm PL bands arise from Ge-Ge and Ge-Si defect centers, while the 400 nm PL is related to GeO color centers in the SiO2 islands. The existence of these PL bands indicates the formation of a Si-based nanoscale light source array. PACS 78.55.Mb; 42.72.Bj; 68.65.+g 相似文献
990.
M. Zhou Y.K. Zhang L. Cai J.Z. Zhou Z.H. Shen X.R. Zhang S.Y. Zhang 《Applied Physics A: Materials Science & Processing》2003,76(7):1113-1116
In this communication, we report a numerical model that predicts the mechanical deformations associated with the pulsed laser
irradiation of a film surface, based on thermal diffusion theory. The model is consequently advanced to produce a method for
evaluating film adhesion strength. The epicenter surface displacements within the irradiated fields have been measured using
a heterodyne interferometer. The comparison of the experimental data and the displacements calculated by the model shows good
agreement. By investigating the propagating acoustic modes under non-destructive and destructive modes, we reveal that, with
or without interface delamination, the phase structure of the longitudinal waves will be altered due to the change of reflection
mode at the interface. Applying shock dynamics theory, we evaluate the adhesion strength of the TiN/stainless interface. We
also indicate the strain rate can be up to 105∼106 s-1 during film interface delamination.
Received: 5 April 2002 / Accepted: 24 June 2002 / Published online: 26 February 2003
RID="*"
ID="*"Corresponding author. Fax: +86-511/879-1919, E-mail: mzhou@ujs.edu.cn 相似文献