共查询到20条相似文献,搜索用时 31 毫秒
1.
We mix the emission of a femtosecond Ti:sapphire laser with the emission of a continuous wave infrared laser in a beta-barium borate crystal. Green light with a center wavelength of 527 nm and a spectral width of 2.5 nm resulting from sum frequency generation is detected. An intensity study verifies that a nonlinear χ(2) process is at the origin of the green light generation. The experimentally obtained conversion efficiency of 7 × 10−10 is in good agreement to simple theoretical considerations. 相似文献
2.
Anatase phase TiO2 films have been grown on fused silica substrate by pulsed laser deposition technique at substrate temperature of 750 °C under the oxygen pressure of 5 Pa. From the transmission spectra, the optical band gap and linear refractive index of the TiO2 films were determined. The third-order optical nonlinearities of the films were measured by Z-scan method using a femtosecond laser (50 fs) at the wavelength of 800 nm. The real and imaginary parts of third-order nonlinear susceptibility χ(3) were determined to be −7.1 × 10−11esu and −4.42 × 10−12esu, respectively. The figure of merit, T, defined by T=βλ/n2, was calculated to be 0.8, which meets the requirement of all-optical switching devices. The results show that the anatase TiO2 films have great potential applications for nonlinear optical devices. 相似文献
3.
Weitian Wang Yanmin Wang Zhenhong Dai Yuming Sun Yuanping Sun 《Applied Surface Science》2007,253(10):4673-4676
Periodic Au nanoparticle arrays were fabricated on silica substrates using nanosphere lithography. The identical single-layer masks were prepared by self-assembly of polystyrene nanospheres with radius R = 350 nm. The structural characterization of nanosphere masks and periodic particle arrays was investigated by atomic force microscopy. The nonlinear optical properties of the Au nanoparticle arrays were determined using a single beam z-scan method at a wavelength of 532 nm with laser duration of 55 ps. The results show that periodic Au nanoparticle arrays exhibit a fast third-order nonlinear optical response with the nonlinear refractive index and nonlinear absorption coefficient being n2 = 6.09 × 10−6 cm2/kW and β = −1.87 × 10−6 m/W, respectively. 相似文献
4.
Tingyin Ning Hong Shen Heng Lu Zhihui Sun Lingzhu Cao Dongyi Guan Dongxiang Zhang Guozhen Yang 《Applied Surface Science》2008,254(7):1900-1903
The triangular-shaped Au/ZnO nanoparticle arrays were fabricated on fused quartz substrate using nanosphere lithography. The structural characterization of the Au/ZnO nanoparticle arrays was investigated by atomic force microscopy. The absorption peak due to the surface plasmon resonance of Au particles at the wavelength of about 570 nm was observed. The nonlinear optical properties of the nanoparticle arrays were measured using the z-scan method at a wavelength of 532 nm with pulse duration of 10 ns. The real and imaginary part of third-order nonlinear optical susceptibility, Re χ(3) and Im χ(3), were determined to be 1.15 × 10−6 and −5.36 × 10−7 esu, respectively. The results show that the Au/ZnO nanoparticle arrays have great potential for future optical devices. 相似文献
5.
This paper presents an analytical and numerical investigation of an intense circularly polarized wave propagating along the static magnetic field parallel to oscillating magnetic field in magnetoactive plasma. In the relativistic regime such a magnetic field is created by pulse itself. The authors have studied different regimes of propagation with relativistic electron mass effect for magnetized plasma. An appropriate expression for dielectric tensor in relativistic magnetoactive plasma has been evaluated under paraxial theory. Two modes of propagation as extraordinary and ordinary exist; because of the relativistic effect, ultra-strong magnetic fields are generated which significantly influence the propagation of laser beam in plasma. The nature of propagation is characterized through the critical-divider curves in the normalized beam width with power plane For given values of normalized density (ωp/ω) and magnetic field (ωc/ω) the regions are namely steady divergence (SD), oscillatory divergence (OD) and self-focusing (SF). Numerical computations are performed for typical parameters of relativistic laser-plasma interaction: magnetic field B = 10-100 MG; intensity I = 1016 to 1020 W/cm2; laser frequency ω = 1.1 × 1015 s−1; cyclotron frequency ωc = 1.7 × 1013 s−1; electron density ne = 2.18 × 1020 cm−3. From the calculations, we confirm that a circularly polarized wave can propagate in different regimes for both the modes, and explicitly indicating enhancement in wave propagation, beam focusing/self-guiding and penetration of E-mode in presence of magnetic field. 相似文献
6.
Hajime Okada Hidetsugu Yoshida Hisanori Fujita Masahiro Nakatsuka 《Optics Communications》2006,266(1):274-279
A liquid-cooled ceramic Nd:YAG split-disk laser amplifier has been designed for a high-average-power laser system. The maximum average output power of 17.1 W (1.71 J at 10 Hz) and the beam size of far-field pattern with 1.5 times diffraction limit was obtained. The combination of liquid cooling for disk laser material and wavefront compensation with a phase conjugation mirror was demonstrated. The wavefront degradation by liquid cooling was observed and measured with Michelson interferometer and far-field patterns. 相似文献
7.
Junko Morikawa Akihiro OrieYuta Hikima Toshimasa HashimotoSaulius Juodkazis 《Applied Surface Science》2011,257(12):5439-5442
Changes of thermal diffusivity inside femtosecond laser-structured volumes as small as few percent were reliably determined (with standard deviation less than 1%) with miniaturized sensors. An increase of thermal diffusivity of a crystalline high-density polyethylene (HDPE) inflation films by 10-20% from the measured (1.16 ± 0.01) × 10−7 m2 s−1 value in regions not structured by femtosecond laser pulses is considerably larger than that of non-crystalline polymers, 0-3%. The origin of the change of thermal diffusivity are interplay between the laser induced disordering, voids’ formation, compaction, and changes in molecular orientation. It is shown that laser structuring can be used to modify thermal and optical properties. The birefringence and infrared spectroscopy with thermal imaging of CH2 vibrations are confirming inter-relation between structural, optical, and thermal properties of the laser-structured crystalline HDPE inflation films. Birefringence modulation as high as Δn ∼ ± 1 × 10−3 is achieved with grating structures. 相似文献
8.
Raman spectra of bismuth ferrite (BiFeO3) over the frequency range of 100-1500 cm−1 have been systematically investigated with different excitation wavelengths. The intensities of the two-phonon modes are enhanced obviously under the excitation of 532 nm wavelength. This is attributed to the resonant behavior when incident laser energy closes to the intrinsic bandgap of BiFeO3. The Raman spectra of BiFeO3 excited at 532 nm were measured over the temperature range from 77 to 678 K. Besides the abnormal changes of the peak position and the linewidth of the A1 mode at 139 cm−1, the prominent frequency shift, the line broadening and the decrease of the intensity for the two-phonon mode at 1250 cm−1 were observed as the temperature increased to Néel temperature (TN). All these results indicate the existence of strong spin-phonon coupling in BiFeO3. 相似文献
9.
Recently the finding of an indication for a decrease of the proton-to-electron mass ratio μ = mp/me by 0.002% in the past 12 billion years was reported in the form of a Letter [E. Reinhold, R. Buning, U. Hollenstein, P. Petitjean, A. Ivanchik, W. Ubachs, Phys. Rev. Lett. 96 (2006) 151101]. Here we will further detail the methods that led to that result and put it in perspective. Laser spectroscopy on molecular hydrogen, using a narrow-band and tunable extreme ultraviolet laser system at the Laser Centre Vrije Universiteit Amsterdam, results in transition wavelengths of spectral lines in the Lyman and Werner band systems at an accuracy of (4-11) × 10−8, depending on the wavelength region. This corresponds to an absolute accuracy of 0.000004-0.000010 nm. A database of 233 accurately calibrated H2 lines is presented here for future reference and comparison with astronomical observations. Recent observations of the same spectroscopic features in cold hydrogen clouds at redshifts z = 2.5947325 and z = 3.0248970 in the line of sight of two quasar light sources (Q 0405−443 and Q 0347−383) resulted in 76 reliably determined transition wavelengths of H2 lines at accuracies in the range 2 × 10−7 to 1 × 10−6. Those observations were performed with the Ultraviolet and Visible Echelle Spectrograph at the Very Large Telescope of the European Southern Observatory at Paranal, Chile. A third ingredient in the analysis is the calculation of an improved set of sensitivity coefficients Ki, a parameter associated with each spectral line, representing the dependence of the transition wavelength on a possible variation of the proton-to-electron mass ratio μ. The new model for calculation of the Ki sensitivity coefficients is based on a Dunham representation of ground state and excited state level energies, derived from the most accurate data available in literature for the ground electronic state and the presently determined level energies in the and C1Πu states. Moreover, the model includes adiabatic corrections to electronic energies as well as local perturbation effects between B and C levels. The full analysis and a tabulation of the resulting Ki coefficients is given in this paper. A statistical analysis of the data yields an indication for a variation of the proton-to-electron mass ratio of Δμ/μ = (2.45 ± 0.59) × 10−5 for a weighted fit and Δμ/μ = (1.99 ± 0.58) × 10−5 for an unweighted fit. This result, indicating the decrease of μ, has a statistical significance of 3.5σ. Mass-variations as discussed relate to inertial or kinematic masses, rather than gravitational masses. Separate treatment of the data gives a similar positive result for each of the quasars Q 0405−443 and Q 0347−383. The statistical analysis is further documented and possible systematic shifts underlying the data, with the possibility of mimicking a non-zero Δμ/μ value, are discussed. The observed decrease in μ corresponds to a rate of change of d lnμ/dt = −2 × 10−15 per year, if a linear variation with time is assumed. Experiments for detecting a possible variation of μ in the modern epoch via ultra-precision experiments on H2 quadrupole transitions are proposed. 相似文献
10.
Single-frequency diode lasers have been frequency stabilized to 1.5 kHz Allan deviation over 0.05-50 s integration times, with laser frequency drift reduced to less than 1.4 kHz/min, using the frequency reference provided by an ultranarrow inhomogeneously broadened Er3+:4I15/2→4I13/2 optical absorption transition at a vacuum wavelength of 1530.40 nm in a low-strain LiYF4 crystal. The 130 MHz full-width at half-maximum (FWHM) inhomogeneous line width of this reference transition is the narrowest reported for a solid at 1.5 μm. Strain-induced inhomogeneous broadening was reduced by using the single isotope 7Li and by the very similar radii of Er3+ and the Y3+ ions for which it substitutes. To show the practicability of cryogen-free cooling, this laser stability was obtained with the reference crystal at 5 K; moreover, this performance did not require vibrational isolation of either the laser or crystal frequency reference. Stabilization is feasible up to T=25 K where the Er3+ absorption thermally broadens to ∼500 MHz. This stabilized laser system provides a tool for interferometry, high-resolution spectroscopy, real-time optical signal processing based on spatial spectral holography and accumulated photon echoes, secondary frequency standards, and other applications such as quantum information science requiring narrow-band light sources or coherent detection. 相似文献
11.
We have developed a method of stabilizing multiple lasers based on double saturation spectroscopy. Compared with other laser-stabilization methods based on conventional saturation spectroscopy, ours provides numerous reference spectra constructed with several velocity groups of atoms. Two independent laser sources can be simultaneously stabilized by using combined optical-pumping processes associated with a single Rb reference. We analyzed the stability of the feedback loop taking the correlation effect of the saturation spectra into consideration. We experimentally demonstrated two stabilized laser sources with a frequency difference of 6,109 MHz in the 87Rb D2 line. The results were in good agreement with theory within errors in measurement. 相似文献
12.
We report on the femtosecond laser micromachining of photo-induced embedded diffraction grating in flexible Poly (Dimethly Siloxane) (PDMS) plates using a high-intensity femtosecond (130 fs) Ti: sapphire laser (λp = 800 nm). The refractive index modifications with diameters ranging from 2 μm to 5 μm were photo-induced after the irradiation with peak intensities of more than 1 × 1011 W/cm2. The graded refractive index profile was fabricated to be a symmetric around from the center of the point at which femtosecond laser was focused. The maximum refractive index change (Δn) was estimated to be 2 × 10−3. By the X-Y-Z scanning of sample, the embedded diffraction grating in PDMS plate was fabricated successfully using a femtosecond laser. 相似文献
13.
M. Dybiec S. Ostapenko J.L. Casas Espinola K.J. Malloy 《Applied Surface Science》2006,252(15):5542-5545
The photoluminescence spectra of InAs quantum dots (QDs) embedded into four types of InxGa1−xAs/GaAs (x = 0.10, 0.15, 0.20 and 0.25) multi quantum well MBE structures have been investigated at 300 K in dependence on the QD position on the wafer. PL mapping was performed with 325 nm HeCd laser (35 mW) focused down to 200 μm (110 W/cm2) as the excitation source. The structures with x = 0.15 In/Ga composition in the InxGa1−xAs capping layer exhibited the maximum photoluminescence intensity. Strong inhomogeneity of the PL intensity is observed by mapping samples with the In/Ga composition of x ≥ 0.20-0.25. The reduction of the PL intensity is accompanied by a gradual “blue” shift of the luminescence maximum at 300 K as follows from the quantum dot PL mapping. The mechanism of this effect has been analyzed. PL peak shifts versus capping layer composition are discussed as well. 相似文献
14.
Cyril Drag 《Optics Communications》2007,275(1):190-195
A two-colour laser technique is developed for photodetachment microscopy, by means of microwave modulation of a CW single-mode dye laser. A phase modulation regime is achieved through an electro-optical LiNbO3 crystal excited at the frequency 1.95 GHz. The two first sidebands created are selected by rejection of the other orders through a plane Fabry-Perot interferometer. With the resulting two-colour radiation, the photodetachment microscopy technique is applied to a beam of 32S− ions. It is shown that the superposition of the two resulting interference patterns can be used as a ‘spectral vernier’ to remove the uncertainty on the electric field and absolute energy scale. Without any initial assumption on the value F of the electric field in the laser-ion interaction region, a measure of F and of the electron affinity eA of Sulfur can be obtained. Putting 16 recordings of two-colour photodetachment interferograms together, with the only condition that F be the same for all experiments, one gets eA(32S) = 16752.978(11) cm−1, which is quite compatible, even though not as accurate, with the most recently recommended value eA(32S) = 16752.9760(42) cm−1. A proposal is made for going from an incoherent to a coherent two-colour photodetachment scheme, which would make photodetachment interferograms sensitive to a new degree of freedom. 相似文献
15.
Jean-Michel Lamarre Franck Billard Michel Lequime Ludvik Martinu 《Optics Communications》2008,281(2):331-340
Nanocomposite films consisting of gold nanospheres or gold nanorods embedded in a silica matrix have been prepared using a hybrid deposition technique consisting of plasma-enhanced chemical vapor deposition of SiO2 and co-sputtering of gold, followed by annealing at 900 °C. Subsequent irradiation with 30 MeV heavy ions (Cu5+) was used to form gold nanorods. Linear and nonlinear optical properties of this material are closely related with the surface plasmon resonance in the visible. The nonlinear absorption coefficient (α2@532 nm) for the films containing gold nanospheres was measured by Z-scan and P-scan techniques, and it was found to be isotropic and equal to −4.8 × 10−2 cm/W. On the contrary, gold nanorods films exhibited two distinct surface plasmon resonance absorption bands giving rise to a strong anisotropic behavior, namely a polarization-dependent linear absorption and saturable absorption. Z-scan and P-scan measurements using various light polarization directions yielded nonlinear absorption coefficient (α2@532 nm) values varying from −0.9 × 10−2 cm/W up to −3.0 × 10−2 cm/W. Linearity of the P-scan method in the context of nanocomposite saturable absorption is also discussed. 相似文献
16.
The phase conjugation geometry of degenerate four wave mixing (DFWM) technique has been employed to study the third-order optical nonlinear susceptibility (χ3) and second-order hyperpolarizability of multi-wall carbon nanotubes (MWCNTs). MWCNTs were grown by thermal chemical vapor deposition method and, subsequently functionalized with carboxylic acid group to improve their solubility in an organic solvent, ethylene glycol. The average hyperpolarizability for each carbon atom has been found to be 4.74 × 10−46 m5/V2 for the pump pulse of 8 ns at 532 nm. Decreasing the pulse width of the pump laser decreases the average value of hyperpolarizability. The absorption spectra show a monotonous increase from IR through visible and give an opportunity to estimate the imaginary part of the χ3 by the open aperture Z-scan technique. 相似文献
17.
Multilayer films containing anionic iron phthalocyanine tetrasulfonate (FePcTsNa4) and cationic poly(diallydimethyl ammonium chloride) were prepared using electrostatic self-assembled layer-by-layer technique. The growth of the film was monitored by ultraviolet-visible absorption spectroscopy, and the morphology of the film was characterized by atomic force microscopy. Polarized visible spectra showed that macrocycles of FePcTsNa4 in the film presented a flat orientation relative to the plane of the solid substrates. The third-order nonlinear optical properties of the film were studied by using Z-scan technique with laser duration of 21 ps at the wavelength of 532 nm. The FePcTsNa4/PDDA film exhibited strong self-focusing effect with n2 value of 4.13 × 10−15 m2/W, which is 4 orders larger than that of FePcTsNa4 aqueous solution. 相似文献
18.
This paper reports on the absorption, visible and near-infrared luminescence properties of Nd3+, Er3+, Er3+/2Yb3+, and Tm3+ doped oxyfluoride aluminosilicate glasses. From the measured absorption spectra, Judd-Ofelt (J-O) intensity parameters (Ω2, Ω4 and Ω6) have been calculated for all the studied ions. Decay lifetime curves were measured for the visible emissions of Er3+ (558 nm, green), and Tm3+ (650 and 795 nm), respectively. The near infrared emission spectrum of Nd3+ doped glass has shown full width at half maximum (FWHM) around 45 nm (for the 4F3/2→4I9/2 transition), 45 nm (for the 4F3/2→4I11/2 transition), and 60 nm (for the 4F3/2→4I13/2 transition), respectively, with 800 nm laser diode (LD) excitation. For Er3+, and Er3+/2Yb3+ co-doped glasses, the characteristic near infrared emission bands were spectrally centered at 1532 and 1544 nm, respectively, with 980 nm laser diode excitation, exhibiting full width at half maximum around 50 and 90 nm for the erbium 4I13/2→4I15/2 transition. The measured maximum decay times of 4I13/2→4I15/2 transition (at wavelength 1532 and 1544 nm) are about 5.280 and 5.719 ms for 1Er3+ and 1Er3+/2Yb3+ (mol%) co-doped glasses, respectively. The maximum stimulated emission cross sections for 4I13/2→4I15/2 transition of Er3+ and Er3+/Yb3+ are 10.81×10−21 and 5.723×10-21 cm2. These glasses with better thermal stability, bright visible emissions and broad near-infrared emissions should have potential applications in broadly tunable laser sources, interesting optical luminescent materials and broadband optical amplification at low-loss telecommunication windows. 相似文献
19.
This paper introduces a dual-path heterodyne Mach-Zehnder interferometer adopted for wavelength shift determinations. In this interferometer, two parallel incident beams are separated into two interference pairs which are then recombined to generate two interference signals. A parallel plate is placed on the path of one wave of an interference pair, so the phase difference of the interference signals is a function of the plate and beam wavelength, and the interferometer is thus able to determine the wavelength shift of the incident beam. A setup constructed to realize the proposed interferometer is described, it shows that the interferometer has a resolution up to 1.1 × 10−10 (λ2/nm), and the experimental results of applying this setup not only agree the validity of the interferometer but also indicate that the interferometer has a stability of 6.5 × 10−10 (λ2/nm). 相似文献
20.
V.B. Tiwari S. Singh S.R. Mishra H.S. Rawat S.C. Mehendale 《Optics Communications》2006,263(2):249-255