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The phase‐contrast method of visualizing transparent objects is applied to ultrasonic imaging. In this method a thin polyethylene phase plate is placed at the back focal plane of an acoustic object lens which causes velocity variations in the object to be converted to proportional amplitude variations at the image plane. Examples of the application of this method to image acoustically transparent (i.e., nonabsorbing) structures, using a recently developed system to visualize ultrasonic waves, are presented.

An ultrasonic transducer with an electrode pattern in the shape of a Fresnel zone plate (FZP) is useful in acoustic imaging. However a major problem in focusing with an FZP is that the final image will have a large zero-order component and this will restrict the dynamic range of the system. One way to solve this problem is to use a Fresnel phase plate pattern (FPP).

A new method for the wavelength dependence of the index of refraction has been recently proposed. It is based upon an accurate determination of the positions of dark bands which appear in the source spectrum observed in the focal plane of a spectroscope while a phase plate is partly inserted in its field. After the method has been reminded, experimental results obtained with known glasses and liquid crystals are reported proving the efficiency and the reliability of the method. In addition of those experimental data, a discussion is devoted to the versality of this new method also the accuracy of the results is considered.

Talbot bands, looking like a channelled spectrum, are produced when a phase plate is partly inserted in the field of a spectroscope. The position and the spacing of the bands in the spectrum of the source directly depends on the optical thickness and therefore the refractive index of the phase plate. In the case of a transmission grating spectroscope, the bands appear only in spectral orders on the same side as the phase plate. The bands can be observed also in case of a two stepped plate, their position being related to the difference of the two refractive indices of the plate, they appear in spectrum orders on the side where the higher index half plate have been inserted in. Using this early known phenomenon in conjunction with modern technology, we propose a method based upon an accurate determination of the positions of these dark bands for computing the dispersion curve of any transparent liquid or solid material, the curve being built up from only one experiment whereas several are required usually. In this paper, after the method have been described, experimental results obtained with known glasses are reported proving the efficiency and the reliability of the technique. Also this method is extended to birefringent materials, it is shown that the extraordinary and ordinary dispersion curve can be obtained simultaneously. Experimental results on liquid crystals materials are reported Proposition d'une nouvelle methode pour obtenir la courbe de dispersion de materiaux transparents. Methode basee sur une determination precise de la position des bandes dans le spectre, associee a une manipulation numerique des donnees conduisant a l'obtention de la courbe de dispersion et ce en une seule experience

The past decade has witnessed a quantum revolution in the field of computation, communication and materials investigation. A similar revolution is also occurring for free-electron based techniques, where the classical treatment of a free electron as a point particle is being surpassed toward a deeper exploitation of its quantum nature. Adopting familiar concepts from quantum optics, several groups have demonstrated temporal and spatial shaping of a free-electron wave function, developing theoretical descriptions of light-modulated states, as well as predicting and confirming fascinating phenomena as attosecond self-compression and orbital angular momentum transfer from light to electrons. In this review, we revisit the milestones of this development and the several methods adopted for imprinting a time-varying phase modulation on an electron wave function using properly synthesized ultrafast light fields, making the electron an exquisitely selective probe of out-of-equilibrium phenomena in individual atomic/nanoscale systems. We discuss both longitudinal and transverse phase manipulation of free-electrons, where coherent quantized exchanges of energy, linear momentum and orbital angular momentum mediating the electron-light coupling are key in determining their spatio-temporal redistribution. Spatio-temporal phase shaping of matter waves provides new routes toward image-resolution enhancement, selective probing, dynamic control of materials, new quantum information methods, and exploration of electronic motions and nuclear phenomena. Emerging as a new field, electron wave function shaping allows adopting familiar quantum optics concepts in composite-particle experiments and paves the way for atomic, ionic and nuclear wave function engineering with perspective applications in atomic interferometry and direct control of nuclear processes.

A new all-fibre device for controlling the state of polarisation (SOP) in a single-mode fibre is proposed. It consists of two fibre elements called rotatable fibre crank (RFC) elements, each of which is equivalent to a rotatable phase plate. It features a very low insertion loss when used in a fibre circuit, because it can be spliced with input and output fibres, and that the control is endless as in a rotatable phase plate. The effectiveness of the SOP control using this device is verified experimentally.

A spiral phase plate is applied to the optical scanning holography system to improve the depth resolution of the reconstruction, the simulation results show that the depth interval can be resolved at a 0.4 mm with only a single hologram.

A pair of diffractive optical elements (DOEs), together forming a specially designed Moire pattern, can create an effective spiral phase plate with a helical charge that depends upon the mutual rotation angle.

Experimental focal plane intensity distributions are presented for a 10‐zone acoustic zone plate operating at approximately 10 MHz. The results are related to the spatial frequency response of the transducer. Some initial imaging experiments with this transducer are described along with preliminary results for an acoustic phase plate.

Unwin has used a metallized non-conducting thread in the back focal plane of the objective lens that stops out a portion of the unscattered beam, takes on a localized positive charge and thus produces an additional phase shift to give a different transfer function of the lens. Under the particular conditions Unwin used, the phase contrast image was shifted to bright phase contrast for optimum focus.We have investigated the characteristics of this type of electrostatic phase plate, both analytically and experimentally, as functions of the magnitude of charge and defocus. Phase plates have been constructed by using Wollaston wire to mount 0.25μ diameter platinum wires across apertures ranging from 50 to 200μ diameter and vapor depositing SiO and gold on the mounted wires to give them the desired charging characteristics. The net charge was varied by adjusting only the bias on the Wehnelt shield of the gun, and hence the beam currents and effective size of the source.

In this work, a simulation experimental scheme of phase adjustments for a phase-adjusted focusing laser accelerator is discussed, and a method of specific design for the phase plate is given. We have produced the phase plate, and carried out the experiment of phase adjustment. The experimental results are consistent with the theoretical design.

General formulas governing the modification of the longitudinal Kerr magneto-optic effect by dielectric layers deposited on the ferromagnetic surface are simplified by two assumptions justified on experimental evidence. From the resulting formulas it is shown that the change in Kerr rotation σ can be evaluated by means of a simple vector diagram. It follows that the increases in σ due to the dielectric layer are almost unlimited, and that the effect of the dielectric layer in this case can be regarded as an antireflection effect. The improvements of signal-to-noise ratio associated with the Kerr effect are, however, strictly limited, and the function of the dielectric is then partly that of a phase plate. Results much better than have been obtained with single layers of zinc sulfide are not likely to be achieved.