Fresnel zone

About: Fresnel zone is a research topic. Over the lifetime, 2337 publications have been published within this topic receiving 37650 citations.

Nanoscale imaging using a compact laser plasma EUV source

Abstract: High resolution imaging methods and techniques are currently under development. One of them is an extreme ultraviolet (EUV) microscopy, based on Fresnel zone plates. In this paper a compact, high-repetition, laser-plasma EUV source, emitting quasi-monochromatic radiation at 13.8nm wavelength was used in a desktop EUV transmission microscopy with a spatial (half-pitch) resolution of 50nm. EUV microscopy images of objects with various thicknesses and the spatial resolution measurements using the knife-edge test are presented.

Aperture-modulated Diffusers (AMDs)

Abstract: In this chapter we discuss the design of optical diffusers for the generation of flat-top intensity distributions, as required for 248 nm or 193 nm excimerlaser applications [4,5]. We investigate the generation of far-field distributions with various shapes, uniform intensity and high efficiency.

Millimeter wave band radio signal reflecting plate and radio communication system

Abstract: PURPOSE:To improve the efficiency of the reflecting plate by forming a reflecting plane for odd number order Fresnel zones only on the reflecting plate and a non-reflecting plane for even number order Fresnel zones only on the reflecting plate. CONSTITUTION:Only odd number order Fresnel zones F1, F3,... on a reflecting plate 1 are formed as reflecting faces and even number order Fresnel zones F2, F4,... on the reflecting plate 1 are formed as non-reflecting faces. Since a reflecting wave on the even number order Fresnel zones F2, F4,... has a phase difference of lambda/2 with respect to the reflecting wave on the odd number order Fresnel zones F1, F3,... on the reflecting plate 1, the reflecting waves are cancelled together at a reception point. However, the even number order Fresnel zones F2, F4,... are formed as non-reflecting faces, then the reflecting wave having a phase difference of lambda/2 is lost and cancellation action is lost, and reception power is increased. Thus, the efficiency of the reflecting plate is improved.

Computer simulation of physical phenomena in waveguide acousto-optical devices for photonic systems

Abstract: The several dozen versions of waveguide acousto-optical devices (WAOD) are used as components of photonic system. The quality of the WAOD essentially determines the limiting parameters of photonic system. The characteristics of WAOD are defined by the Bragg cell and the lens system. A particular emphasis was laid upon computer analysis of frequency and dynamic characteristics of Bragg cell with different types of interdigital electro-acoustic transducer. The temperature and radiation effects upon the interference phenomena in the Bragg cell were investigated. The planar lens system with high numerical aperture should be used for a high resolution and dynamic range (DR). To increase the numerical aperture the optical system included several planar refractive lenses have to be used. We have been design the optical systems included planar refractive lenses and modified topology Fresnel lens. Therefore the elements of Fresnel lens can be of different thickness and to several Fresnel zones. The surface of the eye's pupil should be aplanatic lens design. In the case of WAOD the DR for two resoluted signals is defined by a laser optical beam aperture function, its frequency spectrum, optical losses, displacement and geometry of a CCD detector array. In the case the computer simulation is shown that the DR depend on autocorrelation length for Rayleigh and Mie scattering, scattering on scratches. The scratches give local maximums in scattering function.

Laser light converging and irradiating device

Abstract: PROBLEM TO BE SOLVED: To obtain a spatial intensity distribution of laser light which has been converged weakly at its center part and intensely at its peripheral part by arranging a specific composite Fresnel zone plate right before or behind a condenser lens. SOLUTION: The composite Fresnel zone plate 1 has a unit cell obtained by providing a Fresnel zone plate, which is optically different in pitch, concentrically in a Fresnel zone plate together. Then this unit cell and a complementary unit cell which is opposite in phase difference of 0 and π radian from the unit cell are arranged in quantities at random on the same plate so that they are in half-and-half proportion. The obtained composite Fresnel zone plate 1 is arranged right before or behind the condenser lens. For example, the laser light L outputted from a large-output laser after passing through the composite Fresnel zone plate 1 is converged by the condenser lens 2. An object 3 is placed almost at a distance of the focal length (f) of the condenser lens 2.