共查询到20条相似文献,搜索用时 515 毫秒
1.
S. O. Konorov D. A. Sidorov-Biryukov I. Bugar D. ChorvatJr. D. Chorvat A. M. Zheltikov 《JETP Letters》2003,78(4):246-249
Phase and polarization control of photochromism in the solid phase is experimentally demonstrated. Photochromism initiated by a two-photon absorption of femtosecond laser pulses in a three-dimensional solid-phase polymer sample of spiropyran is controlled by varying the polarization state and the chirp of laser pulses. 相似文献
2.
Three-dimensional reversible laser micromachining of polymer materials based on two-photon photochromism is demonstrated.
Unamplified 60-fs, 0.5-nJ pulses of 790-nm Ti:sapphire laser radiation are used to induce a refractive-index change in a polymethyl
methacrylate (PMMA) sample doped with spiropyran molecules through a two-photon absorption process. Waveguides are written
in the bulk of spiropyran-doped PMMA samples by scanning these samples with respect to a tightly focused Ti:sapphire laser
beam. Laser-induced fluorescence is used for on-line monitoring of the laser-micromachining process. The structures written
in photochromic samples can be erased and reconfigured due to the reversibility of the photochromic effect.
Received: 23 April 2003 / Published online: 6 June 2003
RID="*"
ID="*"Corresponding author. Fax: +7-095/939-51-74, E-mail: zheltikov@top.phys.msu.su 相似文献
3.
A. Athanassiou M. Varda E. Mele M.I. Lygeraki D. Pisignano M. Farsari C. Fotakis R. Cingolani S.H. Anastasiadis 《Applied Physics A: Materials Science & Processing》2006,83(3):351-356
The wetting characteristics of surfaces of polymers doped with photochromic spiropyran molecules can be tuned when irradiated
with laser beams of properly chosen photon energy. In particular, UV laser pulses at 308 nm are responsible for the enhancement
of the hydrophilicity of the surfaces, since the embedded non-polar spiropyran molecules convert to their polar merocyanine
isomers upon UV absorption. The process is reversed upon irradiation with green laser pulses at 532 nm. When the photochromic-polymeric
surfaces are micropatterned using soft lithography or photo-polymerisation techniques, they can change their wettability towards
a more hydrophobic or more hydrophilic behaviour depending on the dimensions of the patterned features and on the hydrophilicity-hydrophobicity
of the flat surface. Furthermore, the light-induced wettability variations on these structured surfaces are greatly enhanced
compared to the flat surfaces. This significant increase to the wettability changes is attributed to the combination of the
photochromic interconversions upon laser irradiation together with the photoinduced reversible volume changes of the patterned
features.
PACS 61.82.Pv; 68.08.Bc; 81.16.Nd; 82.35.-x; 42.60.-v; 68.47.Mn 相似文献
4.
M. L. H. ter Heerdt S. A. Basun G. F. Imbusch W. M. Yen 《Journal of luminescence》2002,100(1-4):115-124
We have employed two-photon excitation to study the higher energy levels of Gd3+ ions in CaAl12O19 and we compare the results with those obtained using conventional UV excitation techniques. Under two-photon excitation, the luminescence intensity exhibits an unusual temporal behavior, a very long build-up followed by a decrease by orders of magnitude, ascribed to a recombination-assisted luminescence excitation mechanism assuming photo-ionization of Gd3+ ions and trapping of free electrons on deep traps.
We also find that the two-photon excitation spectra contain an additional broadening contribution which can be attributed to homogeneous broadening of excitation levels caused by excited state absorption into the conduction band. We believe that this may be a general phenomenon whenever participating photons produce ionization of impurity ions from metastable excited states. The phenomenon can manifest itself also in two-photon ionization spectral hole burning and in up-conversion processes (in the latter case, the homogeneous broadening can be caused by an intra-ion excited-state absorption). 相似文献
5.
本文报道气相CS_2紫外双色激光单共振离化的功率密度关系和对高激发态(1~Ⅱg),共振离化特性的研究结果,实验指出通过中间共振态(1~Ⅱ_g)的双光子共振激发三光子离化具有比通过中间共振态((?)A_2)的单光子共振激发三光子离子为高的总离化率,在10~7W/cm~2的功率密度下,观察到饱和效应.实验显示了双色激光单共振离化功率密度关系的研究提供了一种新的光谱学分析方法.这对研究分子高激发态的结构是很重要的. 相似文献
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Ramos-Garcia R. Delgado-Macuil R. Iturbe-Castillo D. De Los Santos E. González Soriano Corral F. 《Optical and Quantum Electronics》2003,35(6):641-650
We report on the photoinduced anisotropy in the holographic recording in spiropyran doped polymers as a result of the photoizomerization of spiropyran into merocyanine. Photoizomerization is achieved with UV polarized light ( = 355 nm) from the third harmonic of Q-switched Nd:YAG laser. After UV illumination a strong and broad polarization-dependent absorption peak centered 600 nm appears. Absorption holograms were recorded with low power He–Ne lasers with 2.2% output diffraction efficiency for polarization parallel to the polarization of the UV laser. The extremely long lifetime of the merocyanine states (12 days in the dark) and their high resolution makes this material promising as an optical memory element. 相似文献
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本文推导出半导体双光子光电导开关的自相关函数,给出对照比与激光强度的关系.实验测出GaAs在1.06 μm Nd:YAG激光超窄脉冲作用下的双光子自相关函数. 相似文献
10.
Joseph R. Lakowicz Ignacy Gryczynski Józef Kuśba Eva Danielsen 《Journal of fluorescence》1992,2(4):247-258
We measured the fluorescence intensity and anisotropy decays of 1,6-diphenyl-1,3,5-hexatriene (DPH)-labeled membranes resulting from simultaneous two-photon excitation of fluorescence. Comparison of these two-photon data with the more usual one-photon measurements revealed that DPH displayed identical intensity decays, anisotropy decays, and order parameters for one- and two-photon excitation. While the anisotropy data are numerically distinct, they can be compared by use of the factor 10/7, which accounts for the two-photon versus one-photon photoselection. The increased time 0 anisotropy of DPH can result in increased resolution of complex anisotropy decays. Global analysis of the one- and two-photon data reveals consistency with a single apparent angle between the absorption and the emission oscillators. The global anisotropy analysis also suggests that, except for the photoselection factor, the anisotropy decays are the same for one-and two-photon excitation. This ideal behavior of DPH as a two-photon absorber, and its high two-photon cross section, makes DPH a potential probe for confocal two-photon microscopy and other systems where it is advantageous to use long-wavelength (680- to 760-nm) excitation. 相似文献
11.
An analysis of the results of previous studies of stimulated scattering of UV pulses in liquids has shown that they disagree with the theory of stimulated scattering. To resolve the inconsistency, stimulated scattering of XeCl excimer laser radiation (λ = 308 nm) with pulse duration τ ≈ 8 ns in liquid hexane is investigated experimentally. A theoretical analysis of the results obtained revealed a new nonlinear optical phenomenon: stimulated thermal scattering induced by the heating due to two-photon absorption, called two-photon stimulated thermal scattering (two-photon STS-2). The stimulated backscatter spectrum contains a previously unknown line corresponding to two-photon STS-2 and a newly discovered SBS line in the UV region. The line is observed in experiment on liquid hexane and is characterized by the frequency shift ΩB = 0.33 cm?1 relative to the pump wavelength λ = 308 nm, in complete agreement with the theory of stimulated Brillouin scattering (SBS). The spectral line called the SBS line in previous studies has a frequency shift much smaller than that predicted by the SBS theory and must be interpreted as an unshifted two-photon STS-2 line. When two-photon STS-2 is used to obtain a phase-conjugate wave, the phase-conjugation fidelity is lower than that achieved by using SBS because of thermal self-action and slow decay of the thermal grating. 相似文献
12.
根据光波耦合方程及亮-暗孤子对解,对稳态情况下多束互不相干的光束在有外加电场的双光子非光伏光折变晶体中的传播进行分析,给出产生亮-暗双光子光折变屏蔽光伏孤子族需满足的条件。证明有外加电场双光子非光伏光折变晶体中存在非相干耦合亮-暗混合屏蔽孤子族,孤子族由偏振态和波长都相同的多束互不相干的光形成。当外加电场方向和晶体光轴方向相同时,双光子光折变晶体可支持亮孤子族总峰值光强稍大于暗孤子族总峰值光强的的非相干耦合亮-暗混合孤子族,当外加电场方向与晶体光轴方向相反时,双光子光折变晶体可支持亮孤子族总峰值光强稍小于暗孤子族总峰值光强的非相干耦合亮-暗混合孤子族。 相似文献
13.
从实验上证实Hg0.695Cd0.305Te 光电二极管空间电荷区中存在双光子吸收的Franz-Keldysh效应.利用一个皮秒Nd:YAG激光器抽运的光学参量产生器和差频产生器作为激发光源,测量了入射波长为λ0=7.92μm的脉冲激光所激发的光响应随入射光强的变化关系.脉冲光响应峰值强度随入射光强的增大呈现二次幂函数增强趋势.采用等效RC电路模型将脉冲光伏信号峰值与入射光强相关联,得到空间电荷区中强电场下单光束
关键词:
Franz-Keldysh效应
碲镉汞
双光子吸收
脉冲光伏信号 相似文献
14.
Three-dimensional microfabrication by two-photon-initiated polymerization with a low-cost microlaser 总被引:3,自引:0,他引:3
Fabrication of submicrometer structures by two-photon-initiated polymerization is performed with an inexpensive and low-power microlaser. This is made possible by the design of photoinitiators with strong two-photon absorption cross sections. We analyze the influence of both material properties and irradiation conditions on the two-photon polymerization rate and show that resins based on our highly sensitive two-photon photoinitiator can be solidified with microlaser excitation, whereas commercial UV photoresins require ultrashort and intense laser pulses. 相似文献
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A numerical analysis of the saturation effects of emitted light intensity in two-photon pumping random lasers is presented
by adding the saturation item to modify the gain in the diffusive equation. Numerical results show that the emitted intensity
reaches its saturation value in a short time interval with sufficient pumping. From the analysis of normalized emitted intensity
and saturation intensity, one can obtain a method to control steady output intensity of two-photon pumping random lasing by
adjusting some parameters of the random media 相似文献
17.
利用三维荧光-紫外光谱表征了荧光猝灭剂的赋存状态,当样品体系中存在Fe(Ⅲ)的情况下,胡敏酸会发生荧光猝灭现象,而其紫外光谱基本不受影响。考察了胡敏酸荧光强度I值(Ex/Em=300 nm/510nm)和紫外吸光度A值(UV300)的变化,I/A比值越小,说明水样中猝灭剂Fe(Ⅲ)浓度越高。当胡敏酸为10,15和20 mg·L~(-1)时,根据Stern-Volmer公式I/I_0=1-f_c×K_c×[c]/(1+K_c×[c])以及拟合函数I/A=f×[k/(CFe~(3+)+c)+b],拟合得到荧光猝灭常数K_c=1.08~1.15,比例系数f_c=1.10~1.14之间,胡敏酸荧光强度值与吸光度比值(I/A)及铁离子浓度(C_(Fe~(3+))相关曲线系数f=0.83~1.19,k=587.19~612.19,c=0.87~0.92,b=-87.09~-46.36,拟合曲线相关性R~2均为0.99。Stern-Volmer公式描述了Fe(Ⅲ)对胡敏酸荧光的猝灭作用,但实际样品测定时难以获得无猝灭剂时的荧光强度I_0。基于荧光强度I_0与紫外吸光度A之间的内在联系,两者比值I/A与Fe(Ⅲ)浓度c的拟合函数亦可以反映Fe(Ⅲ)对胡敏酸荧光的影响。利用拟合公式预测城市污水厂及纳污河流样品的树脂分离富集液中铁离子浓度,与电感耦合等离子体发射光谱仪实际测量值相比,铁离子浓度较高的情况下(铁离子浓度大于0.4 mg·L~(-1)时)预测结果较好,可以判断猝灭剂的存在及相应浓度。 相似文献
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The lineshape of two-photon absorption in a standing-wave field during elastic collisions is studied. It has been found that the transit broadening of the two-photon resonance on vibrational-rotational molecular transitions is sharply decreased because of an increase in the time of interaction of particles with the electromagnetic field due to elastic collisions. The effect considered allows one to obtain supernarrow optical resonances of two-photon absorption in a low-pressure gas with high intensity. 相似文献
20.
When the two-photon absorption of a high intensity pump beam takes place in a semiconductor optical amplifier there is an associated fast phase change of a weak probe signal. A scheme to realize fast all-optical XOR logic function using two-photon absorption induced phase change has been analyzed. Rate equations for semiconductor optical amplifiers, for input data signals with high intensity, configured in the form of a Mach–Zehnder interferometer has been solved. The input intensities are high enough so that the two-photon induced phase change is larger than the regular gain induced phase change. The model shows that both XOR operation and pseudo-random binary sequence generation at 250 Gb/s with good signal to noise ratio is feasible. 相似文献