Diffractive Structure Research Articles

Realization of Photoresponsive Diffractive Beam Splitters

We report on the realization of a light beam splitting effect based on a light sensitive diffractive structure. The periodic structure is realized in soft composite materials doped with an high performance light sensitive Liquid Crystal. The capability of the structure as tunable beam splitter, is monitored by combining its zero and first diffracted orders in a MC-Zehnder geometry interferometer. The fringe visibility of the interference pattern can be finely controlled by means of an external pump source. Low driving power and short response time are the main features of this light controlled beam splitter.

Gribov-Regge Pomeron and hadron structure phenomenology at high energy

Pomeron was introduced as a key object which provides the non-vanishing high energy asymptotic of the total cross sections of strong interactions. The universality of this object was observed first in the studies of the elastic cross sections t -slope shrinkage. Besides the one Pomeron exchange,the unitarity generates more complicated multi-Pomeron contributions which, in particular, describe the diffractive dip structure of the differential 2 → 2 cross sections at a larger t . Somewhat unexpected universal features of Bose-Einstein correlations reported in the studies of inelastic events at CERN hadron colliders (ISR, Spp̄S) are naturally explained within the Pomeron approach. Large Hadron Collider (LHC) opens the possibility to investigate such phenomena in more details and with a high precision.

Inclusive and exclusive diffractive production of dilepton pairs in proton-proton collisions at high energies

We calculate for the first time cross sections for single and central diffractive as well as exclusive diffractive production of dilepton pairs in proton-proton collisions. Several differential distributions are shown. The inclusive diffractive processes are calculated using diffractive parton distributions extracted from the analysis of diffractive structure function and dijet production at HERA. We find that the inclusive single-diffractive Drell-Yan process is by about 2 orders of magnitude smaller than ordinary Drell-Yan process. The central-diffractive processes are smaller by one order of magnitude compared to single-diffractive ones. We consider also exclusive production of dilepton pairs. The exclusive photon-pomeron (pomeron-photon) process constitutes a background to the QED photon-photon process proposed to be used for controlling luminosity at LHC. Both processes are compared then in several differential distributions. We find a region of the phase space where the photon-pomeron or pomeron-photon contributions can be larger than the photon-photon one.

Portable Surface Plasmon Resonance Biosensor for Detection of Nucleic Acids

We present a portable surface plasmon resonance (SPR) sensor based on spectroscopy of surface plasmons on a special diffractive structure. The sensor combines a microfluidic cartridge incorporating the special diffractive structure functionalized with DNA probes and a compact SPR reader. We apply the sensor to detection of nucleic acids employing two most common immobilization methods: (a) biotinylated probes immobilized using the biotin-streptavidin chemistry and (b) thiolated probes attached directly to the surface of the SPR sensor. It is demonstrated that both these immobilization methods allow detecting short nucleic acids at levels below 100 pM.

Multilayer metal/metal-oxide diffractive structure for photonic temperature sensing

We designed and fabricated multilayer metal/metal-oxide surface relief diffractive grating structures by growing alternating Pt and SnO(x) layers. Optical interrogation at 633 nm reveals the temperature dependence of their reflection and transmission diffractive effects. This function is explored here in the context of a remote, spatially localized, photonic temperature sensing operation, achieving sensitivity of 10% per °C for the zeroth-order in the transmission mode. The experimental demonstration is found to be in good agreement with the results of rigorous coupled wave analysis of the composite metal/metal-oxide element.

Magneto-optical resonances in periodic dielectric structures magnetized in plane

We studied the magneto-optical properties of a magnetized diffractive structure composed of a binary diffraction grating and a homogeneous layer. The structure is magnetized in-plane and the magnetization vector is perpendicular to the grating slits. By the electromagnetic modeling, the structure is shown to produce magneto-optical effects in the form of the resonant change of transmittance and reflectance in response to changing magnetization. The said resonant effects are found to occur both for TE- and TM-polarization of the incident wave. The dispersion curves for the structure eigenmodes have been derived by calculating the complex poles of the scattering matrix. Analysis of the dispersion curves shows that frequencies of the magneto-optical resonances coincide with those of the structure eigenmodes. We studied in which way the dispersion curves vary when the structure material is being magnetized. We propose a classification of magneto-optical resonances based on their relation with the symmetry of eigenmodes excited in the structure.

Factorization breaking in single-diffractive dijet production at the Tevatron

We perform a NLO QCD analysis of single-diffractive dijet production in proton-antiproton collisions. By comparing the ratio of single- and non-diffractive cross sections to data from the Tevatron, the rapidity-gap survival probability is determined as a function of the momentum fraction of the parton in the antiproton. Assuming Regge factorization, this probability can be interpreted as a suppression factor for the diffractive structure function measured in deep-inelastic scattering at HERA. In contrast to the observations for photoproduction, the suppression factor in proton-antiproton collisions depends on the momentum fraction of the parton in the Pomeron even at NLO.

Diffractive Structure Functions from the H1 and ZEUS Experiments at HERA

The cross section of inclusive diffractive process ep -> eXp was measured within a wide kinematic range in the H1 and ZEUS experiments at HERA. Results obtained by different experiments and methods are compatible within measurement uncertainties. The measurements were subjected to DGLAP next-to-leading order QCD global fits and the diffractive parton distribution functions (DPDFs) of the proton were determined with noticeably reduced uncertainties due to very high precision of the data. The gluon density precision was much improved in fits which also included data on dijet production in diffractive DIS. Predictions based on the determined DPDFs are in agreement with the measured inclusive cross-section of diffractive dijet photoproduction and charm production in diffractive DIS at HERA. The longitudinal diffractive structure function $F^D_L$ was measured directly for the first time.

Gluon number fluctuations in diffractive deep inelastic scattering

We studied the effect of the gluon number fluctuations (Pomeron loops) on the diffractive deep inelastic scattering in the fixed coupling case. We used a parameter-free method to describe the experimental data and found that the description of the diffractive structure function is improved with \( \chi^{2}_{}\)/d.o.f. = 1.031 once the fluctuations in the gluon number are included. This improvement indicates that the gluon number fluctuations would be relevant in the HERA data.

Holographic grating based high sensitivity device for refractive index measurements

In this communication, we show how a short-pitch diffractive structure can be used as a low-cost high sensitivity device for refractive index measurements with sensitivity of 10(-2). The device consists of a photo-resist diffraction grating put in optical contact with a hollow prism used as a container for a test material. Its main advantage is the possibility to monitor the composition of solids, fluids and gases in real time. Knowledge of optical parameters of a system with high accuracy can be vital when working in the biological/medical field.

Quantitative SLM-based differential interference contrast imaging

We describe the implementation of quantitative Differential Interference Contrast (DIC) Microscopy using a spatial light modulator (SLM) as a flexible Fourier filter in the optical path. The experimental arrangement allows for the all-electronic acquisition of multiple phase shifted DIC-images at video rates which are analyzed to yield the optical path length variation of the sample. The resolution of the technique is analyzed by retrieving the phase profiles of polystyrene spheres in immersion oil, and the method is then applied for quantitative imaging of biological samples. By reprogramming the diffractive structure displayed at the SLM it is possible to record the whole set of phase shifted DIC images simultaneously in different areas of the same camera chip. This allows for quantitative snap-shot imaging of a sample, which has applications for the investigation of dynamic processes.

Natural quasy-periodic binary structure with focusing property in near field diffraction pattern

A naturally-inspired phase-only diffractive optical element with a circular symmetry given by a quasi-periodic structure of the phyllotaxis type is presented in this paper. It is generated starting with the characteristic parametric equations which are optimal for the golden angle interval. For some ideal geometrical parameters, the diffracted intensity distribution in near-field has a central closed ring with almost zero intensity inside. Its radius and intensity values depend on the geometry or non-binary phase distribution superposed onto the phyllotaxis geometry. Along propagation axis, the transverse diffraction patterns from the binary-phase diffractive structure exhibit a self-focusing behavior and a rotational motion.

Diffractive deep inelastic scattering in an AdS/CFT inspired model: A phenomenological study

The analytical treatment of the nonperturbative QCD dynamics is one of main open questions of the strong interactions. Currently, it is only possible to get some qualitative information about this regime considering other QCD-like theories, as for example the N=4 super Yang-Mills (SYM), where one can perform calculations in the nonperturbative limit of large 't Hooft coupling using the Anti-de Sitter space/Conformal field theory (AdS/CFT). Recently, the high energy scattering amplitude was calculated in the AdS/CFT approach, applied to deep inelastic scattering (DIS) and confronted with the $F_2$ HERA data. In this work we extend the nonperturbative AdS/CFT inspired model for diffractive processes and compare its predictions with a perturbative approach based on the Balitsky - Kovchegov (BK) equation. We demonstrate that the AdS/CFT inspired model is not able to describe the current $F_2^{D(3)}$ HERA data and predicts a similar behavior to that from BK equation in the range $10^{-7} \lesssim x_{IP} \lesssim 10^{-4}$. At smaller values of $x_{IP}$ the diffractive structure function is predicted to be energy independent.

Replicative fabrication of diffractive structure from self-assembled particles onto a glass substrate using corona-charging treatment

We have succeeded in the first fabrication of a diffractive structure replicated onto a glass substrate using a template of self-assembled polystyrene particles via corona-charging treatment. A hexagonal close-packed structure of selfassembled particles was used as the template in the structural replication. As a result, a sixfold symmetric diffraction pattern was generated from the glass substrate, on/in which the diffractive structure was replicatively fabricated. The dependence of the diffraction efficiency on processing time of corona-charging treatment was examined. It was found that the diffraction efficiency increased with treatment time up to 2 h. The observed first-order diffraction efficiency was 2.4 × 10−3%. In contrast, the diffraction efficiency decreased after 2 h treatment under our current experimental conditions. This trend of diffraction efficiency was discussed on the basis of structural changes of the polystyrene template.

Unitarized model of inclusive and diffractive DIS withQ2evolution

We discuss the interplay of low-x physics and QCD scaling violations by extending the unified approach describing inclusive structure functions and diffractive production in $\gamma* p$ interactions proposed in previous papers, to large values of Q2. We describe the procedure of extracting, from the non-perturbative model, initial conditions for the QCD evolution that respect unitarity. Assuming Regge factorization of the diffractive structure function, a similar procedure is proposed for the calculation of hard diffraction. The results are in good agreement with experimental data on the proton structure function $F_2$ and the most recent data on the reduced diffractive cross section, $x_P \sigma_r^{\D(3)}$. Predictions for both $F_2$ and $F_L$ are presented in a wide kinematical range and compared to calculations within high-energy QCD.

English

A practical method to mass-produce gratings with limited lateral dimension is to emboss master grating into a Sol-gel waveguide film. Sol-gel titanium dioxide (TiO2) thin film has been deposited on glass substrate using titanium precursors at low temperature environment. As-deposited films were amorphous. The morphology of the deposited film was analyzed by using high resolution SEM (HRSEM).The contact angle of water droplet on the film surface (hydrophilic properties) was measured by contact angle analysis. From the results; the formation of nano diffractive structure TiO 2 film obtained at low load and temperature environment was suggested for high quality structure.

Survival probability for diffractive dijet production inpp¯collisions from next-to-leading order calculations

We perform next-to-leading order calculations of the single-diffractive and nondiffractive cross sections for dijet production in proton-antiproton collisions at the Tevatron. By comparing their ratio to the data published by the CDF collaboration for two different center-of-mass energies, we deduce the rapidity-gap survival probability as a function of the momentum fraction of the parton in the antiproton. Assuming Regge factorization, this probability can be interpreted as a suppression factor for the diffractive structure function measured in deep-inelastic scattering at HERA. In contrast to the observations for photoproduction, the suppression factor in proton-antiproton collisions depends on the momentum fraction of the parton in the Pomeron even at next-to-leading order.

Theoretical and Experimental Analysis of Long-Period Fiber Gratings Made Directly Into Er-Doped Active Fibers

We present a rigorous theoretical and experimental analysis of signal propagation along a long-period fiber grating (LPFG) made in an Erbium-doped amplifying fiber (EDF). First, numerous effects that influence amplifying process in Erbium-doped fibers were considered. These are clustering of Er ions and subsequent upconversion and change of fiber refractive index due to the optical pumping. Subsequently, LPFG-assisted interaction between the amplified fiber core mode and a cladding mode is described combining rate equations that describe propagation through the EDF and coupled-mode equations that describe propagation through the LPFG. While this implementation is relatively straightforward for the signal and pump, it requires particular attention when dealing with spontaneous emission and amplified spontaneous emission (ASE) that are incoherent (described purely by amplitude), but have to diffract on the LPFG (that is amplitude and phase sensitive). This issue is carefully addressed here. As a result, we were able to rigorously describe the propagation of pump, signal, and ASE through the LPFG-amplifying diffractive structure considering effects such as pump depletion, shift of the coupling wavelength due to the pump power, and ASE formation along the structure. Forward pumping (pump copropagating with the signal) and backward pumping (pump counterpropagating to the signal) were both considered. The theoretical analysis was fully verified by carried-out experiments.

Dipole model analysis of the newest diffractive deep inelastic scattering data

We analyse the newest diffractive deep inelastic scattering data from the DESY collider HERA with the help of dipole models. We find good agreement with the data on the diffractive structure functions provided the diffractive open charm contribution is taken into account. However, the region of large diffractive mass (small values of a parameter beta) needs some refinement with the help of an additional gluon radiation.

Diffractive grating structure for coherent light source production

A diffractive structure of cavities is designed to produce resonances at very high frequencies. This type of cavity structure may be useful for producing controllable coherent synchrotron radiation by microbunching the particle beam.