共查询到20条相似文献,搜索用时 78 毫秒
1.
Mingfu Zhang Hengzhi Chen Bin Yang Wenwu Cao 《Applied Physics A: Materials Science & Processing》2009,97(4):741-744
Layered-perovskite ferroelectric Bi2.85La0.15TiNbO9 (LBTN) optical waveguiding thin films were grown on fused silica substrates by pulsed laser deposition (PLD). X-ray diffraction
(XRD) revealed that the film is highly (00l) textured. We observed sharp and distinct transverse electric (TE) and transverse magnetic (TM) multimodes and measured the
refractive indices of LBTN thin films at 632.8 nm. The ordinary and extraordinary refractive indices were calculated to be
n
TE=2.358 and n
TM=2.464, respectively. The film homogeneity and the film-substrate interface were analyzed using an improved version of the
inverse Wentzel–Kramer–Brillouin (iWKB) method. The refractive index of the film remains constant at n
0 within the waveguiding layer. The average transmittance of the film is 70% in the wavelength range of 400–1400 nm and the
optical waveguiding properties were evaluated by the optical prism coupling method. Our results showed that the LBTN films
are very good electro-optical active material. 相似文献
2.
Alexander Horn Ilja Mingareev Alexander Werth Martin Kachel Udo Brenk 《Applied Physics A: Materials Science & Processing》2008,93(1):171-175
Using ultrafast laser radiation glass substrates are welded with glass and silicon plates. The pump beam is focused by a microscope
objective with large NA=0.4 (beam diameter 4 μm) into the glass. After partial absorption of the optical energy, the glass
is heated and melted. Procedures for high-quality welding of glass–glass and glass–silicon substrates with high-repetition
ultra-fast laser radiation have been derived at the repetition rate 700 kHz. The dependencies of the dimension and geometry
of the welding seam on scan velocity, repetition rate and pulse energy have been investigated defining a process window. Adding
a noninterferometric technique for quantitative phase detection with the welding setup, the interaction zone of the welding
seam for the welding partners glass–glass is detected. A change in refractive index is induced by heating and compression
of the glass and has been detected by phase detection up to 2 μs after irradiation with 100 fs time resolution. 相似文献
3.
Single tracks and pairs of tracks are written in the volume of Pr-doped LiYF4-crystals using tightly focused femtosecond laser radiation (λ=1045 nm, τ
p=400–500 fs, f=0.1–1 MHz). Waveguiding between the tracks is demonstrated and optimized by varying the distance between the tracks and the
laser writing conditions. The stress-induced guiding mechanism is explained based on TEM, interference microscopy, near-field
and far-field measurements. It is shown that the single-crystalline material is getting poly-crystalline under femtosecond
laser irradiation. By measuring the lifetime of the 3P1→3H5 transition and the emission spectrum at excitation with λ=444 nm, no influence on these properties of the guided light is observed. This possibly enables the realization of a channel
waveguide laser in the visible spectral range. 相似文献
4.
A. Eremin E. Gurentsov E. Popova K. Priemchenko 《Applied physics. B, Lasers and optics》2011,104(2):285-295
The evidence of the change of the complex refractive index function E(m) of carbon and iron nanoparticles as a function of their size was found from two-color time-resolved laser-induced incandescence
(TiRe-LII) measurements. Growing carbon particles were observed from acetylene pyrolysis behind a shock wave and iron particles
were synthesized by pulse Kr–F excimer laser photo-dissociation of Fe(CO)5. The magnitudes of refractive index function were found through the fitting of two independently measured values of particle
heat up temperature, determined by two-color pyrometry and from the known energy of the laser pulse and the E(m) variation. Small carbon particles of about 1–14 nm in diameter had a low value of E(m)∼0.05–0.07, which tends to increase up to a value of 0.2–0.25 during particle growth up to 20 nm. Similar behavior for iron
particles resulted in E(m) rise from ∼0.1 for particles 1–3 nm in diameter up to ∼0.2 for particles >12 nm in diameter. 相似文献
5.
V. V. Bukin S. V. Garnov V. V. Strelkov T. V. Shirokikh D. K. Sychev 《Laser Physics》2009,19(6):1300-1302
The formation and evolution of femtosecond laser plasma produced in microvolumes of gases at different pressures upon their multiply ionization by high intensity pulses of fundamental and second harmonics of a Ti:sapphire laser is studied. The interferometric technique for precise ultrafast optical diagnostics of such plasma was applied. The numerical technique of interferogram processing and reconstruction of instant spatial distribution of refractive index and free electron density in laser-induced plasma applied for this proposes is described. The spatiotemporal distribution of the refractive index and free electron density were studied with a spatial resolution of ~1 μ m and a temporal resolution of ~70 fs. 相似文献
6.
S. Naderizadeh S. M. Elahi M. R. Abolhassani F. Kanjouri N. Rahimi J. Jalilian 《The European Physical Journal B - Condensed Matter and Complex Systems》2012,85(5):144
The electronic and optical properties of the nonstoicheiometric Heusler alloys
Fe3−x
Mn
x
Si with
(x = 0,0.75,1,1.25,2)
have been studied by the first principles study in the framework of the density functional
theory (DFT). Optical properties including the dielectric function, refractive index,
energy-loss spectra, absorption spectra, optical conductivity and reflectivity were also
calculated. Results show that the electronic structure of
Fe3−x
Mn
x
Si alloys have
half-metallic property for (x = 0.75,1,1.25). The real part of
dielectric function has two main peaks in high energies. From absorption spectra it can be
seen that absorption curves in low energy are broadened with respect to higher energies.
The refractive index has a nonlinear dispersion in the energy range of 45–55 eV. The
energy of plasmon peaks obtained from electron energy loss function (ELF) are about 25 eV. 相似文献
7.
Y. Li Y. Song J. Yang K. Yang X. Zhang Y. Wang 《Applied physics. B, Lasers and optics》2008,92(2):253-257
A unique phase object (PO) with both positive and negative phase retardation is used in the nonlinear-imaging technique with
a phase object (NIT-PO) to measure the nonlinear refractive index of materials. Using positive–negative PO, one can increase
the sensitivity of the NIT-PO compared with the conventional uniform PO. The improvement of sensitivity is especially significant
at negative nonlinear shift regions, and can reach an order of magnitude near the nonlinear phase shift ΔϕNL=-π. The sensitivity increase of the NIT-PO with positive–negative PO is from 1.7 to 3.0 times greater when compared with
the Z-scan technique within ΔϕNL≤|π|. An empirical expression is obtained which allows for direct calculation of the Kerr coefficient from measured the nonlinear
image. CS2 is used to demonstrate the measurement using a positive–negative PO.
PACS 42.65.-k; 42.30.Kq 相似文献
8.
M. Bryushinin V. Golubev Y. Kumzerov D. Kurdyukov I. Sokolov 《Applied physics. B, Lasers and optics》2009,95(3):489-495
We report an experimental investigation of the non-steady-state photoelectromotive force in nanostructured GaN within porous
glass and polypyrrole within chrysotile asbestos. The samples are illuminated by an oscillating interference pattern created
by two coherent light beams and the alternating current is detected as a response of the material. Dependences of the signal
amplitude versus temporal and spatial frequencies, light intensity, and temperature are studied for two wavelengths λ=442 and 532 nm. The conductivity of the GaN composite is measured: σ=(1.1–1.6)×10−10 Ω−1 cm−1 (λ=442 nm, I
0=0.045–0.19 W/cm2, T=293 K) and σ=(3.5–4.6)×10−10 Ω−1 cm−1 (λ=532 nm, I
0=2.3 W/cm2, T=249–388 K). The diffusion length of photocarriers in polypyrrole nanowires is also estimated: L
D=0.18 μm. 相似文献
9.
Bin Yang Hengzhi Chen Mingfu Zhang Feiyan Wang Kokwai Cheah Wenwu Cao 《Applied Physics A: Materials Science & Processing》2009,96(4):1017-1021
Bi3TiNbO9 (BTN) thin films with layered perovskite structure were fabricated on fused silica by pulsed laser deposition. The XRD pattern
revealed that the films are single-phase perovskite and highly (00l) textured. Their fundamental optical constants, such as band gap, linear refractive index, and linear absorption coefficient,
were obtained by optical transmittance measurements. The dispersion relation of the refractive index vs. wavelength follows
the single electronic oscillator model. The nonlinear optical absorption of the films was investigated by single beam Z-scan
method at a wavelength of 800 nm with laser duration of 80 fs. We obtained the nonlinear absorption coefficient β=1.44×10−7 m/W. The results show that the BTN thin films are promising for applications in absorbing-type optical devices. 相似文献
10.
Spectral lines of Yb lasing in 1.03–1.05 μm region structured by 50–200 μm spots were found at focusing a pulsed LiF:F2+ color center laser of 0.5–5.0 GW/cm2 intensity on highly doped Yb:YAG or Yb:glass plates in a resonator. Small spots at the spectrograph located ≈ 1 m apart from
the resonator indicated a “sub-diffraction” directivity of Yb generation, 1–2 orders better than the diffraction limit 10−3–10−2 rad determined by the pumped volume dimensions. Observed features of Yb emission are explained assuming off-axis oscillations
in Yb laser on phase-synchronized photons due to a strong spatial-angular selection of radiation in the resonator. Propagation
of near diffraction free beams at angles to the axis built at the spectrograph slit for every 10–15 ns pulse of Yb generation
a magnified “image” of a structure of generating channels in the active medium. This image projection brought a corresponding
structure of spots in Yb spectra. It was found that channels may be formed due to a high-frequency spatial modulation (micrometers
scale) of the refractive index profile in samples caused by the oscillating amplitude of thermoelastic stresses in the pumped
medium. Obtained data demonstrate a possibility to study (with high spatial and temporal resolution) non-equilibrium stales
of materials in small volumes using laser radiation emerging from these objects. This study results evidence for the novel
concept of the spatial distribution of electromagnetic field of a photon: not in the form of a “travelling” wave but in the
form of a wave with maxima and nodes located at fixed positions along the photon propagation direction. 相似文献
11.
G. Barros I. Guedes L. Misoguti S. C. Zilio C.-K. Loong J. Wang X. Hu H. Zhang 《Applied physics. B, Lasers and optics》2009,94(2):221-225
The Z-scan technique is employed to obtain the nonlinear refractive index (n
2) of the Ca4REO(BO3)3 (RECOB, where RE = Gd and La) single crystals using 30 fs laser pulses centered at 780 nm for the two orthogonal orientations
determined by the optical axes (X and Z) relative to the direction of propagation of the laser beam (k//Y// crystallographic b-axis). The large values of n
2 indicate that both GdCOB and LaCOB are potential hosts for Yb:RECOB lasers operating in the Kerr-lens mode locking (KLM)
regime. 相似文献
12.
NABEEL A BAKR A M FUNDE V S WAMAN M M KAMBLE R R HAWALDAR D P AMALNERKAR S W GOSAVI S R JADKAR 《Pramana》2011,76(3):519-531
Three demonstration samples of intrinsic hydrogenated amorphous silicon (a-Si:H) films were deposited using hot wire–chemical
vapour deposition (HW–CVD) technique. The optical parameters and the thickness were determined from the extremes of the interference
fringes of transmission spectrum in the range of 400–2500 nm using the envelope method. The calculated values of the refractive
index (n) were fitted using the two-term Cauchy dispersion relation and the static refractive index values (n
0) obtained were 2.799, 2.629 and 3.043 which were in the range of the reported values. The calculated thicknesses for all
samples were cross-checked with Taly-Step profilometer and found to be almost equal. Detailed analysis was carried out to
obtain the optical band gap (E
g) using Tauc’s method and the estimated values were 1.99, 2.01 and 1.75 eV. The optical band gap values were correlated with
the hydrogen content (C
H) in the samples calculated from Fourier transform infrared (FTIR) analysis. An attempt was made to apply Wemple–DiDomenico
single-effective oscillator model to the a-Si:H samples to calculate the optical parameters. The optical band gap obtained
by Tauc’s method and the static refractive index calculated from Cauchy fitting are in good agreement with those obtained
by the single-effective oscillator model. The real and the imaginary parts of dielectric constant (ε
r, ε
i), and the optical conductivity (σ) were also calculated. 相似文献
13.
Yu. I. Golovin A. A. Dmitrievskii A. V. Shuklinov P. A. Kosyrev A. R. Lovtsov 《Russian Physics Journal》2012,54(8):914-917
Raman spectroscopy is used to investigate the morphology of silicon phase composition in the indenter imprint with spatial
resolution of ~200 nm. Suppression of the efficiency of Si-XII, Si-III, and a-Si phase formation induced by beta-particle
irradiation from a 90Sr + 90Y source (fluence F = 3.6⋅1010 cm–2) is revealed. 相似文献
14.
A. É. Bugrov S. Yu. Gus’kov V. B. Rozanov I. N. Burdonskii V. V. Gavrilov A. Yu. Gol’tsov E. V. Zhuzhukalo N. G. Koval’skii V. N. Kondrashov M. I. Pergament V. M. Petryakov S. D. Tsoi 《Journal of Experimental and Theoretical Physics》1999,88(3):441-448
We have experimentally investigated the interaction of high-power neodymium laser pulses in the intensity range 1013–1014 W/cm2 with flat low-density (0.5–10 mg/cm3) agar-agar targets under conditions of interest for problems of inertial nuclear fusion. Optical and x-ray methods with high
temporal and spatial resolution were used to examine the dependence of absorption and scattering of the incident beam on the
initial mean density and thickness of the irradiated samples. We show that when a porous target is irradiated, a bulk absorption
layer of high-temperature plasma is produced inside the target whose dimensions are determined by the initial density of the
material. The time dependence and spectral composition of the harmonics 2ω
0 and 3ω
0/2 observed in the plasma-scattered radiation are measured. A theoretical model is developed that describes the interaction
of high-power laser pulses with a porous medium. Predictions of the model, based on the hypothesis of two stages of homogenization
of the target material—a fast stage (0.1–0.3 ns) and a slow stage (1–3 ns), are in good agreement with the experimental data.
Zh. éksp. Teor. Fiz. 115, 805–818 (March 1999) 相似文献
15.
T. Calmano J. Siebenmorgen O. Hellmig K. Petermann G. Huber 《Applied physics. B, Lasers and optics》2010,100(1):131-135
Tracks of modified material were written with femtosecond-laser pulses in neodymium-doped YAG crystals. Due to a stress-induced
change of the refractive index, waveguiding beside the tracks and between two adjacent tracks with a distance of approximately
25 μm was observed. Loss measurements resulted in guiding losses of about 1.6 dB/cm for the double track waveguide. Spectroscopic
investigations of the 4
F
3/2→4
F
11/2 transmission lines of the neodymium ions, which are close to the modified region, revealed a small stress-induced red shift
of the lines. Laser oscillation of single-track waveguides and double-track waveguides was demonstrated with Ti:Sapphire laser
pumping at a wavelength of 808 nm. Best laser performance with about 1.3 W output power at 2.25 W launched pump power was
achieved using a double-track waveguide with a separation of 27 μm at an outcoupling transmission of 95%. 相似文献
16.
Saulius Juodkazis Vygantas Mizeikis Markas Sūdžius Hiroaki Misawa Kenji Kitamura Shunji Takekawa Eugene G. Gamaly Wieslaw Z. Krolikowski Andrei V. Rode 《Applied Physics A: Materials Science & Processing》2008,93(1):129-133
We study experimentally the formation of refractive index voxels (volume elements) in photorefractive LiNbO3 and LiTaO3 crystals illuminated with high irradiance femtosecond laser pulses. We used 150 fs pulses at 800 nm wavelength (energy 6–50 nJ)
tightly focused inside the crystals in a single shot regime. This resulted in a formation of a micrometer size region of elevated
refractive index, which may be used as memory bits in information storage/retrieval application. The maximum refractive index
change of 5×10−4 was recorded in undoped LiNbO3 at an average light intensity of ∼TW/cm2 that is close to the breakdown threshold. A simple setup for photorefractive recording and in situ monitoring of the refractive
index changes has been proposed.
M. Sūdžius leaves from: the Institute of Materials Science and Applied Research of Vilnius University, Lithuania. 相似文献
17.
Real-time measurement of glucose concentration and average refractive index using a laser interferometer 总被引:4,自引:0,他引:4
This study presents a non-destructive, highly precise optical metrology system for measuring the average refractive index of a liquid solution such that its glucose concentration can be derived. The metrology system is employed to measure the average refractive indices of samples with known glucose concentrations ranging from 0 to 200 g/l. By applying a regressional analysis technique to the experimental results, an analytical expression is derived to describe the relationship between the refractive index and the glucose concentration. An excellent agreement is observed between the experimentally determined values of the glucose concentration and the analytically derived results. For an assumed laser interferometer resolution of 1 nm, the measurement resolution of the proposed metrology system is found to be at least F=0.05 g/l, which is significantly better than that of F=2 g/l obtained using the polarimetric glucose sensor presented by Lo and Yu [A polarimetric glucose sensor using a liquid-crystal polarization modulator driven by a sinusoidal signal. Opt Commun, 2006; 259: 40–8]. 相似文献
18.
The temperature dependence of the principal values of the refractive index in Sr1−x
CaxTiO3 (x=0.014) has been measured in the 17–275 K range under various conditions of sample illumination with 1.96 eV photons. The
spontaneous photorefractive contribution δn
ph to the temperature-induced variation of the refractive index of Sr1−x
CaxTiO3, which appears after illumination of the sample in the ferrophase (transition temperature T
c=32 K) and persists in the paraphase under heating up to 150 K, has been separated. The photoinduced polarization has been
estimated.
Fiz. Tverd. Tela (St. Petersburg) 39, 711–713 (April 1997) 相似文献
19.
Optical nonlinearities in aggregates of nanoparticles formed in silver hydrosols (SHs) are studied under pico- and nanosecond
pulsed laser excitation. The dependence of the nonlinear refractive index n
2 on the degree of hydrosol aggregation is studied experimentally at the wavelength λ=1.064 μm. It is found that n
2 changes sign when the degree of hydrosol aggregation is increased. Various physical effects occurring in resonant domains
of the aggregates are analyzed using a simple physical model of two bound silver nanoparticles. The theory takes into account
thermal, elastic, electrostatic, and light-induced effects. Experimental results are discussed in the context of this theory. 相似文献
20.
K. G. Shaynurova S. A. Bakhramov A. M. Kokhkharov U. K. Makhmanov E. A. Zakhidov 《Journal of Applied Spectroscopy》2012,78(6):802-810
Features of light pulse propagation and nonlinear optical transformation of the spectrum generated by titanium-sapphire laser
pulses (τ0.5 = 27 fs, λ0 = 790 nm) have been studied experimentally in a 50-cm cylindrical hollow waveguide (microcapillary with 280-μm diameter core)
filled with gaseous molecular nitrogen and helium. Stable guided propagation of light pulses with an intensity of ~1.5⋅1014 W/cm2 in the fundamental EH11 mode of the gas-filled capillary has been demonstrated. Exact focusing of the laser light made it possible to obtain rather
high relative (≥95%) and absolute (~60%) energy transmission efficiencies for the pulses at gas pressures equal to or lower
than 760 Torr. A method to determine the nonlinear phase shift of the pulses has been proposed. Values of the nonlinear refractive
index n2 ≈ 4.5⋅10–23 cm2/(W⋅Torr) (N2) and n2 ≈ 2.8⋅10–23 cm2/(W⋅Torr) (He) have been found. A short-wavelength shift in addition to the Kerr nonlinearity has been shown to be contributed
by the generated electron plasma at high pulse intensities (≥1014 W/cm2). 相似文献