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In this study, we have scrutinized the frequency gap generation by changing the geometrical parameters of a one-dimensional phononic crystal. For this purpose, we have calculated the transmission coefficient of an incident acoustic wave by using the transfer matrix method. We have retained and fixed the total length of the system and changed the system internal geometry not to increase the system length too much. Another reason was to adjust the phononic band gaps and get the desired transmission properties by finding the optimum internal geometry without increasing or decreasing the total length of phononic crystals. In addition, we also propose few structures with the opportunity of applications in acoustical devices such as sonic reflectors. Our results can also be of high interest to design acoustic filters in the case that transmission of certain frequencies is necessary.

Multiferroics offer an elegant means to implement voltage-control and on the fly reconfigurability in microscopic, nanoscaled systems based on ferromagnetic materials. These properties are particularly interesting for the field of magnonics, where spin waves are used to perform advanced logical or analogue functions. Recently, the emergence of nano-magnonics {\color{black} is expected to} eventually lead to the large-scale integration of magnonic devices. However, a compact voltage-controlled, on demand reconfigurable magnonic system has yet to be shown. Here, we introduce the combination of multiferroics with ferromagnets in a fully epitaxial heterostructure to achieve such voltage-controlled and reconfigurable magnonic systems. Imprinting a remnant electrical polarization in thin multiferroic $\mathrm{BiFeO_3}$ with a periodicity of $500\,\mathrm{nm}$ yields a modulation of the effective magnetic field in the micron-scale, ferromagnetic $\mathrm{La_{2/3}Sr_{1/3}MnO_3}$ magnonic waveguide. We evidence the magneto-electrical coupling by characterizing the spin wave propagation spectrum in this artificial, voltage induced, magnonic crystal and demonstrate the occurrence of a robust magnonic bandgap with $>20 \,\mathrm{dB}$ rejection.

Integrated microwave photonics offers new paradigms for processing signals. Microwave photonics advances, including broadband tunable microwave photonic filters, multifunction processors, and high-resolution photonic sensing systems that provide new capabilities for high-performance signal processing, are presented.

Atomic-resolution low-dose imaging for beam-sensitive materials is one of the most challenging topics in electron microscopy research. In this study, we theoretically developed a new scanning transmission electron microscopy (STEM) imaging technique by maximizing the signal-to-noise ratio of an obtainable image under the weak phase object approximation (WPOA), which we will call optimum bright-field (OBF) imaging. OBF images are obtained by processing multiple images acquired by segmented/pixelated detectors through complex frequency filtering. This method has been confirmed through a systematic image simulation to be highly dose-efficient. Furthermore, we experimentally demonstrate the high dose efficiency of the OBF technique by visualizing the atomic structure in a lithium-ion battery material using a high-speed segmented detector. Furthermore, it was shown that OBF imaging is usable for real-time imaging, which makes low-dose observations of beam-sensitive materials much easier to achieve.

There are a number of characteristics that make metamaterial has wide applications and has been researched at present, such as negative phase, negative index of refraction, super resolution, and reverse of Doppler's effects. This paper investigates a hexagonal metamaterial structure with a split and a double concentric rings so-called split ring resonator hexagonal (SRR-H) for frequency filtering application. SRR-H is designed structurally and operated computationally for frequency range of 1 to 120 GHz. The simulation results showed that SRR-H size will affect the resonant frequency significantly. The resonant frequency tends to shift the lower frequency when the size of the structure is enlarged. The properties of the structure SRR-H, such as permeability, permittivity and the refractive index have a similarity because it is dominated by the properties of permeability. Metamaterial SRR-H successfully responded to double negative and agreed with Lorentz's model.

We report on the applicability of glasses and glass ceramics in the field of high frequency electronics. The main argument for applying such materials in high frequency electronics is their excellent homogeneity, which allows to make designs with kHz accuracy in the range of GHz frequencies. The range of dielectric properties which are covered by glasses and glass ceramics is outlined. Further on a number of examples are discussed were either glasses or glass ceramics are used with antenna functionalities or for high frequency filter applications.

Here, a novel harmonic suppression performance criterion, namely suppression factor (SF), is suggested for the wide-frequency power filtering equipment. Performances of single-tuned passive filter, combination of passive filters tuned to various frequencies, shunt active power filter (APF), and a shunt hybrid active power filter (HAPF) topologies have been evaluated considering their SF values over a defined frequency range. Moreover, effect of the control method for the active filtering equipment on SF values is also analysed by comparing both theoretical and the experimental results. The frequency range of harmonics to be suppressed is chosen using the field measurements of Induction melting furnace (IMF) load, one of the most problematic loads in terms of interharmonics, and a field implemented HAPF system is used for the experimental verifications.

The coupling evolutions of stimulated Raman scattering (SRS) and Raman rescattering (re-SRS) are investigated under the parameter conditions of relevance to the gas-filled hohlraum experiments at the National Ignition Facility by using the nonenveloped fluid code FLAME. It is found that re-SRS works as a frequency filter of the backscattered light of SRS in the gas region. The low frequency modes of scattered light originated from a higher density region would stimulate re-SRS and be heavily depleted by re-SRS near the region of their quarter critical density. The energy in daughter waves of re-SRS is deposited in the gas plasmas. The large amplitude of the daughter Langmuir wave of re-SRS would stimulate cascade Langmuir decay instabilities and induce obvious low frequency density modulations, which can further result in the inflation of high frequency modes of scattered light of SRS at densities lower than the growth region of re-SRS.

Crack depth is one of the important factors determining material strength. Hence, the accurate measurement of crack depth is essential to ensure the reliability of aged structures and manufactured products. If cracks are open, crack depth can be measured by ultrasonics because ultrasound is strongly scattered by the crack tip (Fig. 10.1a) [1]. However, if cracks are closed because of compression residual stress [2, 3] and/or oxide debris generated between the crack faces [4], ultrasonic testing can result in the underestimation (Fig. 10.1b) or nondetection (Fig. 10.1c) of cracks since ultrasound penetrates through closed cracks. Subharmonic phased array for crack evaluation (SPACE) is a novel imaging method for measuring closed-crack depths [5, 6]. SPACE uses the subharmonics generated by short-burst waves and a phased array algorithm with frequency filtering. It enables the precise measurement of closed-crack depths. This chapter starts from fundamental aspects of subharmonic generation at closed cracks. It then describes the principle of SPACE and its application to several types of closed crack.

A widely tunable single-passband microwave photonic filter (MPF) based on a distributed-feedback semiconductor optical amplifier (DFB-SOA) is proposed and experimentally demonstrated in this paper. The fundamental principle is to recover the suppressed optical carrier from a passband optical filter by the wavelength-selective amplification via a DFB-SOA. A microwave signal is then generated by beating the recovered optical carrier with the phase-modulated lower sideband, and thus, an MPF is achieved with the shape of the passband optical filter that is mapped from the optical domain to the electrical domain. By tuning the central wavelength of the passband optical filter, a single-passband MPF with a frequency tuning range from 5 to 35 GHz is obtained. The 3-dB bandwidth and the out-of-band suppression ratio are measured to be 4 GHz and 20 dB, respectively. In addition, the tunability of the MPF that is dependent on the driven current of the DFB-SOA is also experimentally investigated.

Off-axis digital holographic system is built to get hologram. Aiming at complicated structure of bladder tissues, we present hybrid reconstruction algorithm to retrieve high-precision phase distribution, supplying information for tumor diagnose.

We show that waveguides with a dielectric core and a lossy metamaterial cladding (metamaterial-dielectric guides) can support hybrid ordinary-surface modes previously only known for metal-dielectric waveguides. These hybrid modes are potentially useful for frequency filtering applications as sharp changes in field attenuation occur at tailorable frequencies. Our results also show that the surface modes of a metamaterial-dielectric waveguide with comparable electric and magnetic losses can be less lossy than the surface modes of an analogous metal-dielectric waveguide with electric losses alone. Through a characterization of both slab and cylindrical metamaterial-dielectric guides, we find that the surface modes of the cylindrical guides show promise as candidates for all-optical control of low-intensity pulses., Comment: 15 pages, 11 figures. Accepted by Photonics and Nanostructures - Fundamentals and Applications. This version: Title is extended. Section 3 (Modes) and 4 (Characterization) are revised. The abstract, discussion and summary are also revised accordingly

Two dimensional periodic arrays of patch elements can be used as frequency selective surfaces (FSS) owing to the frequency filtering properties of these structures. Arrays of square loops are of interest as frequency selective surfaces for dichroic reflector antennas. This paper describes a new way for modelling and analysis such FSS using the 3D Transmission Line Matrix method and compares the transmission characteristics predicted by the TLM method with those obtained experimentally.

The transmission properties of a two-period structure consisting of dielectric layers and air layers are studied by numeric methods. On the condition of total reflection from dielectric to air layer, the coupling of the evanescent waves in air layers and propagation waves in dielectric layers forms some special transmission bands. Given proper structure parameters, one incident direction only allows one transmission frequency; on the other hand, one transmission frequency only allows one incident direction. This structure can simultaneously achieve frequency filtering and direction filtering.

The transmission properties of a periodic structure consisting of alternating metal layers and air layers are studied by numeric methods. The metal layers are the epsilon-negative (ENG) materials. The interaction of the evanescent waves in metal layers and propagation waves in air layers forms some special transmission bands. Given proper structure parameters, one transmission frequency only allows one incident direction in the low frequency range. This structure can simultaneously achieve frequency filtering and direction filtering.

A new type of comb frequency filter based on one-dimensional photonic crystals (1DPC) containing two kinds of single-negative-refractive media is presented. The filter is a multichannel one with the number of channels being dependent on the number of 1DPC periods. The position of each channel and its Q value can be adjusted varying the thickness of the material layers.

We study theoretically, by means of layer-multiple scattering techniques, the propagation of elastic waves through finite slabs of phononic crystals consisting of metallic spheres in polyester matrix, embedded in air. We focus on the study of modes localized on the surfaces of the structure, investigating the physical parameters which influence and determine their appearance. Our results reveal the existence of absolute phononic frequency gaps in these finite structures, and point out the possibility, under an appropriate choice of the parameters, of tunable regions of frequency free of propagating and/or surface-localized modes. This could be very useful in the design of devices related to frequency filtering, waveguiding, etc.

A new type of filter based on one-dimensional photonic crystals is presented. A photonic crystal consists of a periodic repetition of air layers and epsilon-negative (ENG) material layers. This type of filter has high-Q values without defects. The Q values and the filtering frequency can be precisely adjusted by modulating the thicknesses of the ENG material layers and the air layers, respectively. A method of deciding the position of the transmission band for the photonic crystals is presented. The effect of absorption of ENG materials on the filter is also considered.

The effect of tempering on the magnetic Barkhausen noise (MBN) signal profile was studied in case-carburised EN36 steel using a range of magnetic excitation frequencies and a number of frequency ranges for analysis of the MBN signal. The MBN level generally increases with tempering due to coarsening of the microstructure. With higher values of excitation frequency, f EX , the MBN profile exhibits a single peak, but with low values of f EX , double peaks are observed. The MBN peak obtained with higher f EX was found to correlate well with hardness changes in a region, down to 100 μm below the surface. The analysis of the MBN signal produced with low f EX , in narrow frequency ranges selected by software frequency filtering, showed variations in the extent of changes in the relative height of the two MBN peaks in the profile. After taking into account the skin depth-frequency relation for the MBN signal, variations in the values of the two MBN peaks in different analysing frequency ranges were found to correlate well with hardness variations at different depths down to 425 μm below the surface. An empirical relationship has been established between the hardness-depth profile and the MBN measurements.

International audience; We review our recent progress on the realisation of pulse shaping in passively-mode-locked fibre lasers by inclusion of an amplitude and/or phase spectral filter into the laser cavity. We numerically show that depending on the amplitude transfer function of the in-cavity filter, various regimes of advanced waveform generation can be achieved, including ones featuring parabolic-, flat-top-and triangular-profiled pulses. An application of this approach using a flat-top spectral filter is shown to achieve the direct generation of high-quality sinc-shaped optical Nyquist pulses with a widely tunable bandwidth from the laser oscillator. We also present the operation of an ultrafast fibre laser in which conventional soliton, dispersion-managed soliton (stretched-pulse) and dissipative soliton mode-locking regimes can be selectively and reliably targeted by adaptively changing the dispersion profile and bandwidth programmed on an in-cavity programmable filter. The results demonstrate the strong potential of an in-cavity spectral pulse shaper for achieving a high degree of control over the dynamics and output of mode-locked fibre lasers.

Absorbing material has excellent attenuation ability to EM wave in high frequency. LC filter filled with absorbing material can realize high insert loss, above 80 dB, between 10 kHz and 110 GHz. This text first introduce the principle of absorbing wave of absorbing material, and then discussed eight compounded absorbing material's attenuation ability to high frequency EM energy. At last is the conclusion.

A variety of magnetic resonance (MR) techniques have proved useful to quantify perfusion using endogenous water as a blood flow tracer. Assuming that water is a freely diffusable tracer, the model used for these techniques predicts that the quantitation of perfusion is based on three parameters, all of which can depend on blood flow. These are the longitudinal tissue relaxation time, the transit time from point of labeling to tissue, and the difference in tissue MR signal between an appropriate control and the labeled state. To measure these three parameters in parallel, a dynamic arterial spin labeling (DASL) technique is introduced based on the analysis of the tissue response to a periodic time varying degree of arterial spin labeling, called here the labeling function (LF). The LF frequency can be modulated to overdetermine parameters necessary to define the system. MR schemes are proposed to measure the tissue response to different LF frequencies efficiently. Sprague-Dawley rats were studied by DASL, using various frequencies for the LF and various arterial pCO2 levels. During data processing, the periodic behavior of the tissue response to the LF allowed for frequency filtering of periodic changes in signal intensity unrelated to perfusion and arterial spin labeling. Measures of transit time, tissue longitudinal relaxation time, and perfusion agreed well over a range of LF frequencies and with previous results. DASL shows potential for more accurately quantifying perfusion as well as measuring transit times associated with arterial spin labeling techniques.

At present, polymer-dispersed liquid crystals (PDLC) are widely used as operating elements of optical devices such as microlenses and the elements, whose principle of operation is based on light scattering [1]. PDLC light scattering features depend on a shape and size of liquid crystal (LC) drops as well as on the director orientation inside of drops.

A novel optical signal processing scheme based on cascaded co-directional couplers is proposed and numerically demonstrated. The proposed approach can overcome important limitations of grating-assisted coupler structures.

In this paper, we present our recent results in microwave photonic filters based on multi-longitudinal-mode fiber lasers. Theoretical analysis and experiments were carried out, and the experimental results show excellent agreement with the numerical simulations.

We developed a teleoperated-robot-based high-resolution OCT needle imaging under MRI guidance. In addition, we developed a low-cost CGD probe that can be integrated within surgical tools to provide real-time audio feedbacks of blood flow.

We present a programmable multitap microwave photonic filter with an arbitrary phase response operating over a broad bandwidth. Complex coefficient taps are achieved by optical line-by-line pulse shaping on a 10 GHz flat optical frequency comb using a novel interferometric scheme. Through high-speed real-time measurements, we demonstrate programmable chirp control of a waveform via phase filtering. This achievement enables us to compress broadband microwave signals to their corresponding bandwidth-limited pulse duration. This project was supported in part by the Naval Post- graduate School under grant N00244-09-1-0068 under the National Security Science and Engineering Faculty Fellowship program. Any opinions, findings, and conclu- sions or recommendations expressed in this publication are those of the authors and do not necessarily reflect the views of the sponsors. Victor Torres-Company gratefully acknowledges funding from a Marie Curie International Outgoing Fellowship (PIOF-2009-234996).

Multiphoton excitation-induced photoacoustic microscopy (MEPAM) can be used to investigate the interior of dense objects precisely and directly because the multiphoton excitation occurs only at the focal point. This method makes it possible to avoid the strong signal from the surface of dense objects. However, in the case of tissue imaging, one-photon photoacoustic signals affect the image constructed from MEPAM signals, owing to the smaller cross section of multiphoton absorption compared with that of one-photon absorption. Thus, in order to apply MEPAM for precise investigation in living tissues, it is important to enhance (or extract) only the photoacoustic signals induced by multiphoton excitation. In this study, we examined the use of frequency-selective detection (frequency filtering) in multiphotonphotoacoustic imaging by evaluating the depth discrimination and penetration. Because MEPAM signals are generated in a very small region, they include higher frequency components compared with one-photon photoacoustic signals. We measured the images at the cross sections of blood-vessel phantoms visualized by MEPAM using the high-frequency components. We found that the images visualized using only high-frequency components showed better contrast compared with those visualized using all frequency components. We conclude that the combination of frequency filtering and MEPAM demonstrates great potential for precise observation of cross sections of blood vessels in living tissues.

A Fourier frequency filtering approach is applied to thin film design in situations well exceeding the theoretical limits of the conventional Fourier transform method. Previous work is generalized to oblique incidence. Examples of a high-reflectance filter and a broadband, wide-angle antireflection coating are given.

Fourier techniques and direct optimization are applied to the synthesis of complex rugate filters. A hybrid approach is presented. The design strategies are illustrated numerically for different spectral shapes.

Fabry-Perot cavity filtering of broadband optical frequency combs is studied experimentally and theoretically. Effects of dispersion, mirror coatings, and carrier envelope offset frequency are analyzed while highlighting applications to waveform generation and spectroscopic references.

Acoustic emission (AE) spectroscopy without frequency filtering (∼broadband AE) and moderate time integration is shown to be sensitive enough to allow the investigation of subtle nano-structural changes in ferroelectric BaTiO3 and ferroelastic Pb3(PO4)2. AE signals during weak phase transitions are compatible with avalanche statistics as observed previously in large-strain systems. While the data are too sparse to determine avalanche exponents, they are well suited to determine other thermodynamic parameters such as transition temperatures and critical stresses.

In this paper, absorbing ability of eight kinds of fill-in absorbing material is measured through coaxial waveguide in the frequency band from 0.5 GHz to 40 GHz. The test data show that in this frequency band, the average value of insert loss of coaxial waveguide, which is filled with eight kinds of absorbing material respectively, is greater than 80 dB. If they are employed in EMI filter, maybe the filter's highest operating frequency can reach 40 GHz or even higher.

An intracavity wavelength filter formed by a nematic liquid crystal cell is used to tune the wavelength of a fibre laser. The tuning range of the device is 17 nm and the tuning rate is 8 nm/V.

Novel photonic crystals for the microwave regime are under study: lattices from infinitely long spirals and lattices from canonical chiral particles. Many interesting dispersion properties are revealed, which make such structures prospective for technical applications: rejector and band frequency filtering including the high-selectivity filtering, polarization filtering and transformation, etc. Dispersion characteristics can be easily adjusted mechanically tuning the spiral step.

A narrowband microwave filter built around crystal-like inhomogeneities is suggested. The calculated and experimental characteristics of the filter are reported, and the field distribution in its structure is analyzed.

High-repetition-rate optical frequency combs can act as broadband photonic mixers and downconvert a microwave signal to an intermediate frequency (IF) band so that it becomes accessible with high-speed electronics. In this Letter, we show that with line-by-line pulse shaping and dispersive propagation, the photonic mixer can simultaneously perform programmable multitap complex-coefficient-filtering within the IF band. This solution opens new possibilities for microwave signal processing by combining the flexibility of optoelectronic frequency comb technology with high-speed analog-to-digital converters. This project was supported in part by the Naval Post- graduate School under grant N00244-09-1-0068 under the National Security Science and Engineering Faculty Fellowship program and grant ECCS-1102110 from the National Science Foundation. Any opinion, findings, and conclusions or recommendations expressed in this publication are those of the authors and do not necessa- rily reflect the views of the sponsors. Victor Torres- Company gratefully acknowledges funding from a Marie Curie Fellowship (PIOF-2009-234996).

A new, very simple AR coating synthesis method is further developed and compared to a recent `quasi-optimal' technique. A remarkable resemblance is found in the results. The reason for this similarity is given and the performance of both approaches is discussed.

An image-processing algorithm for analysis of migration of vascular endothelial cells in culture is presented. The algorithm correctly detected the cellular regions on either side of an artificial 'wound' made by dragging a sterile pipette tip across the monolayer of cells (scratch wound assay). Frequency filtering and mathematical morphology were used to approximate the boundaries of cellular regions. This allowed measurement of the distance between the regions, and therefore the migration rates, regardless of the orientation of the wound and even in cases where the cells were sparse and not tightly packed.

A method and system are provided for frequency filtering compressional wavenergy. An elastic cylinder is filled with a fluid that is selected based on a fluid density ρ i and a dilatational wave phase velocity c i thereof. When the elastic cylinder so-filled is subjected to a compressional wave propagating in a fluid environment, a first radial resonance frequency of the elastic cylinder is controlled by the fluid density ρ i and the dilatational wave phase velocity c i . Further tuning of the first radial resonance frequency can be achieved by adjusting the radial wall thickness of the elastic cylinder.

Spun-on contour coating properties are characterized for two absorptive undercoats, AUCs, and a contrast-enhanced layer, CEM-388. A low-pass frequency filter contour modeling procedure is used to simulate the coating contours on a real silicon-on-sapphire epi-island layout. The computed thickness variations are used to estimate the variation in optical densities of these spun-on films on the topography. The variations in optical densities arc discussed in terms of the expected dimensional deviations introduced into the patterned resist layer. At the same spun-on thickness, one absorptive undercoat offers improvement in dimensional control when compared to the other. Changes in the thickness of the CEM-388 layer may also introduce significant dimensional deviations in the underlying positive resist layer. In, both cases the more conformal spun-on contour coating properties produce improved resist imaging.

A new technique for suppressing unwanted resonances in thickness-shear-mode quartz crystals having spherically-bevelled edges has been developed. The technique is based on the fact that the strain associated with inharmonic overtones of vibration extends closer to the perimeter of the crystal along certain axes than along others, while the fundamental thickness-shear mode may, with correct geometry, have negligible amplitude near the crystal perimeter. In view of this it has been found possible, by placing small amounts of an adhesive such as an epoxy resin at certain points on the edge of the crystal, to damp the inharmonic modes selectively without greatly influencing the main response. The new technique permits relatively large variations in electrode diameter to be made without having to alter the crystal geometry to maintain suppression of the unwanted resonances. This facility greatly reduces the problem of crystal-filter design by extending the range of crystal inductances which are available. The paper describes the basic theory underlying the technique, called `selective damping?, and illustrates its application to obtain single-response crystals in the frequency range 2?8 Mc/s.

Frequency-domain analysis offers several advantages when considering surface profile measurements. Vibration of the sample during the measurement is often clearly defined in the profile frequency spectrum and its effect on the measured data can be reduced by an appropriate filter. The finish of surfaces with periodic height variations (such as diffraction gratings) can be measured if the periodic structure is first removed. This paper examines the application of frequency filtering techniques to these problems.