Polarization Fizeau interferometer based on birefringent thin film

A polarization Fizeau interferometer based on birefringent thin film is presented. The interferometer adopts a birefringent thin film to obtain orthogonally polarized and strictly common-path reference and test beams. Advantages include ease of implementation on large-aperture interferometer, measuring test optics from long distance, and achieving high fringe visibility. The phase shift is obtained by combining a quarterwave plate and an analyzer. The concepts illustrated are verified experimentally.     

Effect of a fullerene C60 addition on the strength properties of nanocrystalline copper and aluminum under shock-wave loading

The Hugoniot elastic limit and the spall strength of aluminum and copper samples pressed from a mixture of a metallic powder and 2–5 wt % C₆₀ fullerene powder are measured under a shock loading pressure up to 6 GPa and a strain rate of 10⁵ s^?1 by recording and analyzing full wave profiles using a VISAR laser interferometer. It is shown that a 5% C₆₀ fullerene addition to an initial aluminum sample leads to an increase in its Hugoniot elastic limit by an order of magnitude. Mixture copper samples with 2% fullerene also exhibit a multiple increase in the elastic limit as compared to commercial-grade copper. The elastic limits calculated from the wave profiles are 0.82–1.56 GPa for aluminum samples and 1.35–3.46 GPa for copper samples depending on the sample porosity. The spall strength of both aluminum and copper samples with fullerene additions decreases approximately threefold because of the effect of high-hardness fullerene particles, which serve as tensile stress concentrators in a material under dynamic fracture.     

Heterodyne Interferometers Using Orthogonally Polarized and Two-Frequency Shifted Light Sources with Super-high Extinction Ratio

This paper describes heterodyne interferometers using orthogonally polarized and two-frequency shifted light sources of two types with super-high extinction ratio to reduce non-linearity of the interferometer due to polarization cross-talk. The acousto-optic modulators are used to shift light frequency. In the first interferometer the light source with Glan-Thomson prisms of very high extinction ratio (50 dB) is used to make the polarization cross-talk very small. In the second interferometer the light source of two-frequency shifted beams with small crossing angle (2.5 rnrad-10 mrad) is used to completely exclude non-linearity of the interferometer due to polarization cross-talk. By measuring the thickness of vacuum evaporation film, it was demonstrated that the interferometers are useful to measure thickness of a thin film in nanometer order.     

ELECTRON SPIN RESONANCE CHARACTERISTICS OF NITROGEN-DOPED FULLERENE

The nitrogen-doped fullerene has been obtained by arc discharge between two high-purity graphite rods in the atmosphere of N₂ and He, The electron spin resonance(ESR) characteristics of N-doped fullerene have been investigated. The results show that the ESR spectra of N-doped fallerene axe composed of two parts, a paramagnetic signal of N-center and a paramagnetic signal of C-center, For comparing with N-doped fullerene, we have also studied ESR spectra of C₆₀ powder, C₆₀ sublimed film and H-doped C₆₀ film. For C₆₀ powder and H-doped C₆₀ film, their in situ ESR. measurements are carried out at various temperatures, and reasonable explanations are proposed.     

A reflection interferometer with a noninverted response function based on a phase grating

It is shown that the inclusion of a simple phase grating in the optical scheme of a resonator provides the possibility of performing spectral investigations in reflected light with characteristics of a Fabry-Perot interferometer. The response function of the interferometer is examined, and experimental results are presented.     

Reflection interferometer based on the Troitsky thin film for frequency selection in fiber lasers

A two-mirror multiple-beam interferometer with a noninverted response function in reflection is used for the frequency selection and tuning in fiber lasers. The simplest version of the interferometer is based on a thin metal (Troitsky) film. Such a reflection interferometer corresponds to an external (with respect to a fiber) two-mirror cavity that consists of a spherical highly reflective (99.8%) mirror and a plane mirror represented by the thin metal film deposited on the fiber end face. Tuning to the selected frequency is performed due to a variation in the distance between the mirrors.     

Encapsulation of small fullerenes into nitrogenated holey nanotubes: a density functional theory study

Encapsulation of fullerene into nanotubes based on a C₂N sheet, known as nitrogenated holey graphene, was investigated using density functional theory. The structural and electronic properties of these carbon hybrid materials, consisting of nitrogenated holey nanotubes and a small C₂₀ fullerene, were studied. The formation energies showed that encapsulation of the fullerene into the nitrogenated holey nanotube is an exothermic process. To characterise the electronic properties, the electronic band structure and density of states of armchair and zigzag nitrogenated holey nanotubes were calculated. Filling these nanotubes with the C₂₀ fullerene resulted in a p-type semiconducting character. The energy band gap of the nitrogenated holey nanotubes decreased with fullerene encapsulation. The results are indicative of the possibility of band gap engineering by encapsulation of small fullerenes into nitrogenated holey nanotubes.     

Research technique of metamaterials with the controlled effective negative refractive index and their characteristics

A design of the two-beam hybrid microwave interferometer for measuring refractive indices of metamaterials is described. It is based on the branching of radiation using a waveguide directional coupler. Radiations of the interferometer waveguide arms are summed and the phase disbalance of the interferometer arms is counted on the waveguide measuring line. The frequency dispersion of the negative refractive indices of the metamaterial samples with a variable distance between its constituent plates is experimentally investigated. A possibility of controlling the refractive index of a metamaterial is demonstrated.     

高灵敏度集成光偏振干涉仪特性及生化传感应用研究

利用射频溅射技术在平面单模玻璃波导表面局部淀积一层Ta₂O₅梯度薄膜, 形成复合光波导芯片, 结合棱镜耦合法制备了一种集成光偏振干涉传感器. 基于四层平板波导模型理论分析了复合光波导表面折射率灵敏度S_RI与Ta₂O₅梯度薄膜等效厚度T_eq的关系, 结合实验测定的S_RI得出了本工作中所使用Ta₂O₅梯度薄膜的T_eq ≈ 33.021 nm, 进一步得出芯片吸附层厚度灵敏度S_ab≈ (2.412× 2π) nm^-1. 利用该复合波导偏振干涉仪结合Lorentz-Lorenz有效介质理论测得了市售食用白醋中醋酸的浓度, 并以市售牛栏山二锅头酒为例进行了白酒掺水和掺甲醇的测试, 结果表明, 白酒掺水或甲醇前后的折射率改变量与掺杂量成准线性变化关系; 原位实时监测了丁酰胆碱酯酶的动态吸附过程及细胞色素c/聚苯乙烯磺酸钠的分子自组装过程, 并利用测得的位相差变化结合芯片吸附层厚度灵敏度S_ab 获得了蛋白质表面覆盖度.     

System for measuring optical admittance of a thin film stack

A new method based on the polarization interferometer structure has been applied to measure the optical admittance, the refractive index and thickness of a thin film. The structure is a vibration insensitive optical system. There is one Twyman-Green interferometer part to induce a phase difference and one Fizeau interferometer part to induce the interference in the system. The intensities coming from four different polarizers were measured at the same time to prevent mechanical vibration influence. Using the polarization interferometer, the optical admittance, the refractive index and thickness of a single layer of Ta₂O₅ thin film has been measured. The measurement results were compared with the results obtained by ellipsometer. The results meet reasonable values in both refractive index and thickness.     

Photoinduced electron transfer involving radical ions in multicomponent solutions

A phenomenological study of a specific radical ion mechanism of formation of metastable products is presented. Energy level diagrams of fullerene C₆₀, tetramethylbenzidine, perylene, and radical ion pairs in toluene and benzonitrile are constructed. The possibility for obtaining fast optical switching and limiting in solutions of C₆₀ fullerene, tetramethylbenzidine, and perylene in toluene is analyzed.     

光纤马赫-曾德尔干涉法测量极化聚合物的电光系数

报道了用光纤马赫曾德尔干涉法测量极化聚合物电光系数的方法和原理。该方法不仅可以测量聚合物薄膜的电光系数而且可以测量聚合物波导的电光系数,并且该方法可以同时测量聚合物的电光系数张量元r13和r33。该方法最突出的优点是不必在聚合物薄膜的表面制备第二个电极,因此尤其适合于在电光聚合物试制阶段测试聚合物的电光系数。干涉仪的输出被反馈到参考臂中控制相位偏置点的压电陶瓷,从而实现对干涉仪相位偏置点的闭环控制,因此降低了对环境稳定性的要求并且提高了测量精度。实际测试了极化聚合物薄膜PMMA-DR1的电光系数张量,其测量值r13=8.3 pm/V,r33=25.7 pm/V。     

Matter-wave interferometer for large molecules

We demonstrate a near-field Talbot-Lau interferometer for C70 fullerene molecules. Such interferometers are particularly suitable for larger masses. Using three free-standing gold gratings of 1 microm period and a transversally incoherent but velocity-selected molecular beam, we achieve an interference fringe visibility of 40% with high count rate. Both the high visibility and its velocity dependence are in good agreement with a quantum simulation that takes into account the van der Waals interaction of the molecules with the gratings and are in striking contrast to a classical moiré model.     

Phase modulation by polarization recording in bacteriorhodopsin: application to phase-shifting interferometry

A novel phase-control method with application to phase-shifting interferometry is presented. The linear polarization state of an external (green) light beam is recorded on a bacteriorhodopsin film, and this polarization state is read by a circular polarized (red) laser beam. By reading the bacteriorhodopsin film, the original (red) wave reverses its circularity and becomes phase shifted by an amount that is dependent on the polarization of the external (green) beam. This method of phase control can be applied in a two-beam interferometer in which the test and reference waves are orthogonally polarized, which allows one to obtain phase modulation without moving parts inside the interferometer.     

High-resolution dynamic measurement using electronic speckle pattern interferometry based on multi-camera technology

The speckle interferometer based on multi-camera technologies using two cameras is applied to a dynamic measurement. The new speckle interferometer is constructed by a prism array and two cameras. A phenomenon, which a bearing-ball collides against a thin polymer film, is investigated by the proposed interferometer. Then, it is shown that the local maximum deformation of the thin film by the collision is about 1.0 μm. Such a deformation process can precisely be analyzed by this method without any troubles of optical dislocations. In the results, it is confirmed that a large deformation process can be analyzed by accumulating measured results of small deformation in every small continuous analysis. Furthermore, it is estimated that the measurement precision of this method is about 5 nm as experimental results.     

Ultimate sensitivity of a reflection interferometer with a noninverted instrumental function

Properties of a multiple-beam interferometer with a transmission-like pattern of the fringes in reflected light are considered. A specific feature of this interferometer (a transmission-like reflection interferometer, or TRI) is an asymmetric one-sided mirror with a multilayer dielectric coating and a thin absorbing film. Characteristics of the mirrors and the interferometer as a whole are calculated as functions of the number of dielectric layers. In the calculations, the losses inside the dielectric coating, which are assumed to be concentrated in the vicinity of the layer boundaries, are taken into account. It is shown that a TRI, in terms of its sensitivity, does not differ substantially from conventional multiple-beam interferometers for the same level of technology of the dielectric coatings. The TRI version under consideration demonstrates mode self-filtration, due to which it reflects only the fraction of the incident light corresponding to the resonance of the interferometer. This allows one, in principle, to eliminate special mode cleaners and to significantly simplify the entire optical arrangement.     

Systematic error elimination by correction of variable interferometer aberrations

The possibility of reducing the variable systematic error in interferometry measurements via a higher degree of compensation of residual aberrations of the interferometer is shown theoretically and verified experimentally. It is proven that, in the case when interferometer aberrations are variable, one reference hologram is insufficient to correct aberrations. However, using several reference holograms on which the aberrations are recorded, it is possible to reconstruct interference patterns in which the influence of residual aberrations on the behavior of bands is reduced to a definite minimal level.     

Michelson interferometer with multichannel interferogram recording

A schematic diagram of a Michelson interferometer with a diffraction grating for which the length of one arm is a function of the transverse coordinate of the light beam is proposed. The possibility of recording the interferograms without mechanical displacement of optical elements of the interferometer is demonstrated.     

Detection of ultrafast phenomena by use of a modified Sagnac interferometer

We describe a time-division interferometer based on the Sagnac geometry for monitoring ultrafast changes in the real and the imaginary components of the refractive index as well as phase changes that are due to surface displacement. Particular advantages of this interferometer are its simple common-path design and operation at normal incidence with a microscope objective for both pumping and probing. Operation is demonstrated by detection of temperature changes and coherent phonon generation in a gold film.     

Ultrafast processes of photoinduced charge and energy transfer in nanostructural fullerene-metal films

The primary stages of photoinduced processes in tin-doped C₆₀ fullerene films have been studied using a femtosecond pump-probe technique with 150-fs laser excitation pulses (λ = 400 nm) and differential transmission and reflection probing in the 1100–1700 nm range. The relaxation dynamics strongly depends both on the metal-to-fullerene ratio in the film and on the mutual distribution (packing) of components in the nanocomposite material. The observed response signal dynamics is related to features in the charge carrier generation, energy transfer between fullerene molecules, and charge transport between metal and fullerene.