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1.
J.?Villarroel M.?Carrascosa A.?García-Caba?es O.?Caballero-Calero M.?Crespillo J.?Olivares 《Applied physics. B, Lasers and optics》2009,95(3):429-433
The photorefractive behaviour of a novel type of optical waveguides fabricated in LiNbO3 by swift heavy ion irradiation is investigated. First, the electro-optic coefficient r
33 of these guides that is crucial in the photorefractive effect is measured. Second, two complementary aspects of the photorefractive
response are studied: (i) recording and light-induced and dark erasure of holographic gratings; (ii) optical beam degradation
in single-beam configuration. The main photorefractive parameters, recording and erasing time constants, maximum refractive-index
change and optical damage thresholds are determined. 相似文献
2.
ShiLing Li 《中国科学G辑(英文版)》2008,51(10):1479-1488
The formation of optical planar waveguides in LiNbO3 and stoichiometric LiNbO3 crystals by proton exchange was reported. The prism-coupling method was used to characterize the dark-line spectroscopy at
the wavelength of 633 and 1539 nm, respectively. The mode optical near-field outputs from proton-exchanged LiNbO3 and SLN waveguides at 633 nm were presented. The mode field from stoichiometric LiNbO3 (SLN) waveguide is lighter and more uniform than that from LiNbO3 waveguide, which means the quality of the waveguide in SLN crystal is better than that of the LiNbO3 waveguide. For proton-exchanged LiNbO3 waveguides, the evolution of the refractive index profile with annealing was presented. The disorder profiles of Nb atoms
in proton-exchanged LiNbO3 waveguides were obtained by Rutherford backscattering/channeling technique. It is shown that the longer the exchange time,
the larger the displacement of Nb atoms.
Supported by the National Natural Science Foundation of China (Grant No. 10475052) and the Scientific Research Start-up Financing
of Qufu Normal University 相似文献
3.
Thin films made by PLD from Er:ZBLAN and Nd:Gd3Ga5O12 are micro machined to form optical wave guiding structures using Ti:sapphire and Yb:glass fiber laser radiation. For the
manufacturing of the ridge waveguides grooves are structured by ablation using femtosecond laser radiation. The fluence, the
scanning velocity, the repetition rate, and the orientation of the polarization with respect to the scanning direction are
varied. The resulting structures are characterized using optical microscopy and scanning electron microscopy. Damping and
absorption coefficients of the waveguides are determined by observing the light scattered from the waveguides due to droplets
in the thin films and the surface roughness of the structured edges. To discriminate between damping due to droplets and the
structured edges, damping measurements in the non-structured films and the structured waveguides are performed. Ridge waveguides
with non-resonant damping losses smaller than 3 dB/cm are achieved. Due to the high repetition rate of the Yb:glass fiber
laser, the manufacturing time for one waveguide has been decreased by a factor of more than 100 compared to earlier results
achieved with the Ti:sapphire laser. 相似文献
4.
S. Chandramohan R. Sathyamoorthy P. Sudhagar D. Kanjilal D. Kabiraj K. Asokan V. Ganesan T. Shripathi U. P. Deshpande 《Applied Physics A: Materials Science & Processing》2009,94(3):703-714
The effect of high electronic energy deposition on the structure, surface topography, optical properties, and electronic structure
of cadmium sulfide (CdS) thin films have been investigated by irradiating the films with 100 MeV Ag+7 ions at different ion fluences in the range of 1012–1013 ions/cm2. The CdS films were deposited on glass substrate by thermal evaporation, and the films studied in the present work are polycrystalline
with crystallites preferentially oriented along (002)-H direction. It is shown that swift heavy ion (SHI) irradiation leads
to grain agglomeration and hence an increase in the grain size at low ion fluences. The observed lattice compaction was related
to irradiation induced polygonization. The optical band gap energy decreased after irradiation, possibly due to the combined
effect of change in the grain size and in the creation of intermediate energy levels. Enhanced nonradiative recombination
via additional deep levels, introduced by SHI irradiation was noticed from photoluminescence (PL) analysis. A shift in the
core levels associated with the change in Fermi level position was realized from XPS analysis. The chemistry of CdS film surface
was studied which showed profound chemisorption of oxygen on the surface of CdS. 相似文献
5.
S. M. Kostritskii 《Applied physics. B, Lasers and optics》2009,95(3):421-428
Original results on investigation of the photorefractive effect in straight channels and integrated-optical circuits such
as a directional coupler, Y-splitter and Mach–Zehnder interferometer, exploiting titanium-indiffused and proton-exchanged
LiNbO3 waveguides, are presented. It has been found that the photorefractive damage is non-negligible for IR radiation with wavelengths
near 1.5 μm in all circuits studied. The new methods for accurate evaluation of small extents of photorefractive effect are
proposed. 相似文献
6.
Tingyin Ning Cong Chen Yueliang Zhou Heng Lu Dongxiang Zhang Hai Ming Guozhen Yang 《Applied Physics A: Materials Science & Processing》2009,94(3):567-570
CaCu3Ti4O12 (CCTO) thin films were successfully prepared on LaAlO3 substrates by pulsed laser deposition technique. We measured the nonlinear optical susceptibility of the thin films using
Z-scan method at a wavelength of 532 nm with pulse durations of 25 ps and 7 ns. The large values of the third-order nonlinear
optical susceptibility, χ
(3), of the CCTO film were obtained to be 2.79×10−8 esu and 3.30×10−6 esu in picosecond and nanosecond time regimes, respectively, which are among the best results of some representative nonlinear
optical materials. The origin of optical nonlinearity of CCTO films was discussed. The results indicate that the CCTO films
on LaAlO3 substrates are promising candidate materials for applications in nonlinear optical devices. 相似文献
7.
Semiconductor nanoparticle and conducting polymer composite is an interesting class of materials for optoelectronic and photovoltaic device application. We have synthesized a composite of nanocrystalline PbS and conducting polymer MEH-PPV by chemical synthesis and studied the effect of swift heavy ion (SHI) irradiation on the composite material. The irradiation of the composite materials in thin film form is carried out with 120 MeV Si+9 ion beam at fluences from 5×1010 to 1013 ions/cm2. Fluence dependent optical and structural properties have been observed in optical absorption, PL and TEM studies. Reduction of nanoparticle size has been observed after irradiation. 相似文献
8.
A continuous wave (CW), extra-cavity singly resonant optical parametric oscillator (SRO) has been demonstrated. The SRO is
based on 5% magnesium-oxide doped periodically-poled lithium niobate (MgO:PPLN) pumped by a CW Nd:YVO4/YVO4 ring laser centered at 1064.4 nm. The nonlinear crystal temperature is kept at 120.0 ± 0.1°C and a domain period of 30 μm
is used in this experiment. When the pump power is 11 W, an output power of 2.0 W at the idler wavelength of 3.479 μm has
been obtained from the OPO. The optical-optical conversion efficiency is about 18.2%, and the slope efficiency is about 20.8%. 相似文献
9.
S. D. Liu J. F. Yang J. L. He B. T. Zhang X. Q. Yang F. Q. Liu H. W. Yang J. L. Xu H. T. Huang 《Laser Physics》2011,21(2):327-330
This paper reported a broadband tuning intracavity optical parametric oscillator (IOPO), based on the multiple grating periodical
poled lithium niobate (PPLN) pumped by a acoustic-optical (AO) Q-switched Nd:YVO4 laser. The widely tunable OPO output signal wavelength range from 1390 to 1605 nm, which was obtained by changing PPLN poling
period from 27.8 to 31.6 μm at a certain temperature of 46°C, while the continuous tuning range was measured from 1475 to
1592 nm with the PPLN poling period of 30 μm by varying the temperature of nonlinear crystal PPLN from 50 to 120°C. The maximum
output power of 0.92 W at 1534 nm with the minimum pulse width of 5.17 ns was generated under the incident pump power of 9.6
W at 808 nm. The corresponding peak power and single pulse energy were calculated to be 5.94 kW and 30.7 μJ, respectively.
The M
2-factor was measured to be 2.01 at the signal power of 0.4 W. 相似文献
10.
It is known that deep ultraviolet (UV) radiation induces a refractive index increase in the surface layer of polymethylmethacrylate (PMMA) samples. This effect can be used for the fabrication of integrated optical waveguides. PMMA is of considerable interest for bio and chemical sensing applications because it is biocompatible and can be micromachined by several methods, e.g. structuring by photolithography, ablation and hot embossing. In the presented work direct UV irradiation of a common PMMA substrate by a krypton fluoride excimer laser beam through a contact mask has been used to write integrated optical Mach-Zehnder interferometers (MZI). MZI are used as sensitive bio and chemical sensors. The aim was to determine contact mask design and laser irradiation parameters for fabricating single-mode MZI for the infrared region from 1.30 μm to 1.62 μm. Straight and curved waveguides have been generated and characterized to determine the optical losses. The generation of channel waveguide structures has been optimized by a two step irradiation process to minimize the lithographic writing time and optical loss. By flood exposure to UV laser radiation in the first step the optical absorption of PMMA can be increased in the irradiated region. The required refractive index profile is then achieved with a second lithographic irradiation. The spectral behaviour of an unbalanced, integrated optical MZI fabricated by this excimer laser based contact mask method is shown for the first time. Further the optical intensity at the output port of a MZI has been measured while the optical path length difference was tuned by creating a temperature difference between the two arms of the MZI. 相似文献
11.
C. Michail A. Toutountzis S. David N. Kalyvas I. Valais I. Kandarakis G. S. Panayiotakis 《Applied physics. B, Lasers and optics》2009,95(1):131-139
The aim of the present study was to measure the imaging transfer characteristics and the luminescence efficiency (XLE) of
a Lu2SiO5:Ce (LSO:Ce) powder scintillator for use in X-ray mammography detectors. An LSO:Ce powder scintillating screen, with a coating
thickness of 25 mg/cm2, was prepared in our laboratory. The imaging performance of the screen was assessed by experimental determination of the
modulation transfer function (MTF) and the detective quantum efficiency (DQE) as well as single index image quality parameters
such as noise equivalent pass band (Ne) and informational efficiency (n
I). A theoretical model, describing radiation and light transfer, was fitted to experimental MTF values in order to estimate
optical properties of the scintillator. Screen irradiation was performed under exposure conditions employed in mammographic
applications (27 kVp, 63 mAs). MTF was determined by the square wave response function (SWRF) method. Results showed that
LSO:Ce exhibits high MTF and DQE values, which are comparable to those of the commercially used Gd2O2S:Tb. Considering our image quality parameters and luminescence efficiency results as well as the fast response of the LSO:Ce
scintillator screen (40 ns), this material can be considered for use in X-ray mammographic detectors. 相似文献
12.
Dinesh Pathak R. K. Bedi Davinder Kaur 《Applied Physics A: Materials Science & Processing》2009,95(3):843-847
AgInSe2 films were prepared by a thermal evaporation technique onto Si(100) substrates at a pressure of 10−5 mbar. Structural and optical properties of films deposited at 300 and 473 K have been investigated. The film composition
was studied by energy dispersive analysis through X-rays. X-ray diffraction patterns indicate that AgInSe2 films have chalcopyrite structure with strong preferred orientation in the (112) direction. Average vertical crystallite
size of 25 nm was observed. The optical energy gaps of 1.20 and 1.90 eV were obtained due to the fundamental absorption edge
and a transition originating from crystal field splitting, respectively. Field emission scanning electron microscopy shows
loosely packed grains of spherical symmetry with some facets. 相似文献
13.
A model of electron transfer by tunneling between trapped electron and hole centers in crystals with hydrogen bonds under
the conditions of thermostimulated mobility of one carrier type in the recombination process has been developed. The proposed
model describes all features in the kinetics of induced optical density relaxation observed in nonlinear optical crystals
of KH2PO4 (KDP) and NH4H2PO4 (ADP) on a wide temporal scale (10−8–10 s) under pulsed irradiation. The results of model calculations have been compared with experimental data on the photoinduced
transient optical absorption (TOA) in KDP and ADP crystals in the visible and UV ranges. The nature of the radiation-induced
defects, which account for the TOA, and the dependence of the TOA decay kinetics on the temperature, excitation power, and
other experimental conditions have been considered. 相似文献
14.
J. Hazarika 《辐射效应与固体损伤》2016,171(11-12):978-998
Polypyrrole (PPy) nanofibers have been synthesized by interfacial polymerization method and irradiated with 160?MeV Ni12+ ions under vacuum with fluences in the range of 1010–1012?ions/cm2. High-resolution transmission electron microscopy results show that upon swift heavy ion (SHI) irradiation the PPy nanofibers become denser. The crystallinity of PPy nanofibers increases upon SHI irradiation, while their d-spacing decreases. Upon SHI irradiation, the polaron absorption band gets red-shifted indicating reduction in the optical band gap energy of the irradiated PPy nanofibers. The indirect optical band gap energy is decreased as compared to corresponding direct optical band gap energy. The number of carbon atoms per conjugation length (N) and carbon atoms per cluster (M) of the SHI-irradiated PPy nanofibers increase with increasing the irradiation fluence. Fourier transform infrared spectra reveal the enhancement in intensity of some characteristic vibration bands upon SHI irradiation. The thermal stability of the PPy nanofibers is enhanced on SHI irradiation. The charge carriers in both pristine and irradiated PPy nanofibers follow the correlated barrier hopping mechanism. Scaling of ac conductivity reveals that the conduction mechanism is independent of the SHI irradiation fluence. 相似文献
15.
Run-Ping Jia Chun-fa Ou-Yang Yong-Sheng Li Jun-He Yang Wang Xia 《Journal of nanoparticle research》2008,10(1):215-219
For the first time, a newly luminescent nanomaterial, monoclinic wolframite-type HgWO4 nanorods (diameter: ∼200 nm; length: ~2000 nm) are prepared by hydrothermal method together with ultrasonic technique. Fluorescent
(FL) and UV–Vis results both show that for HgWO4, ultrasonic irradiation procedure will change its optical behaviors greatly. When the crystals become into nanorods, the
fluorescent emitting peaks (365 and 495 nm) shift to central region, and finally form a wider one at 435 nm. Similar results
of UV–visible absorption peaks are observed for these two products. FTIR spectra further characterize their structure. All
above unique optical performances might result from both small sizes caused by ultrasonic irradiation procedure and involvement
of incompact d10 electrons. Moreover, possible synthesis mechanisms of HgWO4 nanorods are also investigated. 相似文献
16.
X. D. Zhang M. L. Guo C. L. Liu L. A. Zhang W. Y. Zhang Y. Q. Ding Q. Wu X. Feng 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,62(4):417-421
A first-principles study has been performed to evaluate the electronic and
optical properties of wurtzite Zn1-xMgxO. Substitutional doping is
considered with Mg concentrations of x = 0, 0.0625, 0.125, 0.1875 and 0.25,
respectively. Mg incorporation can induce band gap widening due to the
decrease of Zn 4s states. The imaginary part of the dielectric function shows
that the optical transition from band edge emission decreases slightly with
increasing Mg contents. The optical band gap also increases from 3.2 to 3.7
eV with increasing Mg contents from 0.0625 to 0.25. The calculated results
suggest that relatively high Mg concentration is necessary for effective
band gap engineering of wurtzite Zn1-xMgxO. 相似文献
17.
Thermally stabilized channel waveguides with Bragg gratings were fabricated by the space-selective precipitation technique of crystalline Ge nanoparticles using KrF excimer laser irradiation. The periodic structures consisting of Ge nanoparticles were formed in Ge-B-SiO2 thin glass films after exposure to an interference pattern of the laser followed by annealing at 600 °C. The channel waveguides with the periodic structures were fabricated by the cladding of the patterned Cr layers on the films. The diffraction peak for the TE-like mode of 11.8 dB depth was observed clearly at a wavelength of 1526.4 nm, indicating that the periodic structure also served as the optical band-pass filter in optical communication wavelength. The spectral shape, diffraction efficiency, and diffraction wavelength remained unchanged even after annealing at 400 °C. Furthermore, a low temperature dependence of the diffraction wavelength - as low as 8.1 pm/°C - was achieved. The diffraction efficiency was further enhanced after subsequent annealing at 600 °C. The space-selective precipitation technique is expected to be useful for the fabrication of highly reliable optical filters or durable sensing devices operating at high temperature. 相似文献
18.
B. Xu X. Li J. Sun L. Yi 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,66(4):483-487
Using first-principles calculations based on density-functional theory in
its local-density approximation, we investigated the Electronic structure,
ferroelectricity and optical properties of CaBi2Ta2O9 (CBT)
for the first time. It is found that CBT compound has an indirect band gap
of 3.114 eV and the O 2s and 2p states are strongly hybridized with the 6s
states of Bi which belong to the (Bi2O2)2+ planes. The quite
strong Ta–O and Bi–O hybridization is the primary source for
ferroelectricity. Our results imply that the interaction between Bi and O is
highly covalent. The anisotropy occurs mainly above 4 eV in the optical
properties. The different optical properties have been discussed. 相似文献
19.
Abdoljavad Novinrooz Masoomeh Sharbatdaran Hassan Noorkojouri 《Central European Journal of Physics》2005,3(3):456-466
Thin layers of tungsten trioxide have been prepared from an aqueous solution of peroxotungstic acid (PTA) using the sol-gel
method. Compositional, structural and optical characteristics of WO3 coated on indium tin oxide (ITO) conductive glass substrates were studied using X-ray diffractometery (XRD), cyclic voltammetery
(CV), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). Monoclinic and triclinic crystalline
structures for thin film and powdered WO3 were confirmed by XRD analysis. SEM micrograph of annealed samples revealed micro cracks due to a decrease in density and
a contraction of layers. EDX analysis showed that 1∶2 ratio of oxygen and tungsten atoms in the prepared films is obtained
at heat treatment temperatures higher than 200 °C. Furthermore, the annealed samples showed very good electrochromic behavior
in cyclic voltammetery studies. Refractive index “n” and extinction coefficient “k” values were found to be reduced by increasing
the wavelength and decreasing the temperature. 相似文献
20.
Olga Kokkinaki Savas Georgiou 《Applied Physics A: Materials Science & Processing》2008,92(4):1013-1017
Matrix-Assisted-Pulsed-Laser-Evaporation (MAPLE) has emerged as a very promising technique for the deposition of polymers
and biopolymers in intact and functional form. However, our understanding of the mechanism of the procedure is still limited.
Here, we examine laser-induced (248 nm) desorption from condensed CHCl3 solid, which has been employed as a potential matrix in MAPLE. We find that the absorption of the condensed halocarbon increases
significantly with successive laser pulses, as a result of the formation and accumulation of strongly absorbing products.
This results in a significant increase of the ejection efficiency in the irradiation with successive laser pulses. Thus, in
studies employing multi-pulse irradiation protocols, the attained laser-induced temperatures are considerably higher than
what is estimated on the basis of the absorption coefficient of CHCl3. Thus, contrary to previous suggestions, ablation of CHCl3 frozen solid at 248 nm may be due to explosive boiling. A number of additional implications are also discussed. 相似文献