Yoel Arieli

Design of a diffractive optical element for wide spectral bandwidth.

A new method for eliminating the chromatic aberration of a diffractive optical element (DOE) for wideband wavelengths is presented. The wideband-wavelength diffractive optical element (WBDOE) consists of two aligned DOEs. The use of different dispersive materials for the two DOEs eliminates chromatic aberration. The design and simulation of a WBDOE for the visible spectrum are presented.

Design of diffractive optical elements for multiple wavelengths

A method for producing diffractive optical elements (DOEs) for multiple wavelengths without chromatic aberration is described. These DOEs can be designed for any distinct wavelength. The DOEs are produced from two different optical materials, taking advantage of their different refractive indices and dispersions.

Endothelin and Its Suspected Role in the Pathogenesis and Possible Treatment of Glaucoma

Purpose: To review the role of endothelin in intraocular pressure control, its effect on the trabecular meshwork (TM) and the outflow facility, effect on ocular blood flow and vascular regulation and the potential role of endothelin-1 (ET-1) antagonism in the therapeutic paradigm of glaucoma. Methods: A thorough review of the medical literature and a meta-analysis on the level of ET-1 in OAG patients in an attempt to demonstrate the evolving importance of endothelin in glaucoma. Results: ET-1 has been identified in the plasma in concentrations that are markedly increased in a number of systemic as well as ocular pathologies such as glaucoma where underlying vascular dysfunction and pathology play a role. It has been shown that ET-1 induces human TM cell contraction in culture and that it can affect the outflow facility. Evidence indicates that systemic ET-1 regulatory mechanisms and vascular responses to it are also altered in glaucoma. Recently, several endothelin antagonists have been shown to have a potential role in glaucoma therapy. In our meta-analysis, only patients with normal tension glaucoma (NTG) (as opposed to patients with high tension glaucoma (HTG)) had significantly higher plasma ET-1 levels compared to non-glaucomatous control. High tension glaucomaHTG patients had significant higher levels of ET-1 in the aqueous humor. Conclusions: The potential role of ET-1 antagonism in the therapeutic paradigm of glaucoma is an exciting possible new approach in the treatment of OAG patients. In NTG, ET-1 may have both a local and systemic component of vascular dysregulation, while whereas in HTG, the role of ET-1 may be dominantly localized to ocular tissue.

Impaired ocular blood flow regulation in patients with open‐angle glaucoma and diabetes

Background:  To elucidate the potential impact of diabetes mellitus on primary open‐angle glaucoma pathology through vascular deficiency.

Effect of intraocular pressure on the hemodynamics of the central retinal artery: A mathematical model

Retinal hemodynamics plays a crucial role in the pathophysiology of several ocular diseases. There are clear evidences that the hemodynamics of the central retinal artery (CRA) is strongly affected by the level of intraocular pressure (IOP), which is the pressure inside the eye globe. However, the mechanisms through which this occurs are still elusive. The main goal of this paper is to develop a mathematical model that combines the mechanical action of IOP and the blood flow in the CRA to elucidate the mechanisms through which IOP elevation affects the CRA hemodynamics. Our model suggests that the development of radial compressive regions in the lamina cribrosa (a collagen structure in the optic nerve pierced by the CRA approximately in its center) might be responsible for the clinically-observed blood velocity reduction in the CRA following IOP elevation. The predictions of the mathematical model are in very good agreement with experimental and clinical data. Our model also identifies radius and thickness of the lamina cribrosa as major factors affecting the IOP-CRA relationship, suggesting that anatomical differences among individuals might lead to different hemodynamic responses to IOP elevation.

Integrated diffractive and refractive elements for spectrum shaping

Diffractive elements can be designed for spectrum shaping in the Fourier or Fresnel plane by iterative methods. It is necessary to use a Fourier lens and the wavelength for which the diffractive elements were designed to get the required spectrum shaping at the Fourier plane. Using a different wavelength will cause chromatic aberration. We deal with the combination of refractive and diffractive elements and two or more different diffractive elements on the same element to get appropriate beam shaping of light sources with a multiple spectral output. Simulations are preformed that transform the profile of a He-Ne laser with a Nd:YAG laser source, and shape the trapezoidal beam profile of an excimer laser into a Gaussian beam is also considered.

Wave-front control and aberration correction with a diffractive optical element.

A method that permits aberration correction and wave-front reshaping with a diffractive optical element (DOE) is described. Two aligned DOEs made of two different dispersive materials are used. The different dispersions of the two materials in addition to freedom in choosing their thicknesses enables the chromatic aberration and the wave fronts to be manipulated. Design and simulation of such DOEs are described.

Geometrical-transformation approach to optical two-dimensional beam shaping.

The use of geometrical transformations in the design of an optical beam shaper (OBS) is described. Elements based on this approach can transform light distributions into almost any arbitrary distribution. An example OBS is analyzed numerically.

Spatial phase-shift interferometry--a wavefront analysis technique for three-dimensional topometry.

We describe a new wavefront analysis method, in which certain wavefront manipulations are applied to a spatially defined area in a certain plane along the optical axis. These manipulations replace the reference-beam phase shifting of existing methods, making this method a spatial phase-shift interferometry method. We demonstrate the systems dependence on a defined spatial Airy number, which is the ratio of the characteristic dimension of the manipulated area and the Airy disk diameter of the optical system. We analytically obtain the resulting intensity data of the optical setup and develop various methods to accurately reconstruct the inspected wavefront out of the data. These reconstructions largely involve global techniques, in which the entire wavefronts pattern affects the reconstruction of the wavefront in any given position. The methods noise sensitivity is analyzed, and actual reconstruction results are presented.

XPM-induced polarization-state fluctuations in WDM systems and their mitigation

In this paper, we show numerically and experimentally the degradation caused by cross phase modulation (XPM) in systems that use PMD compensators, as well as demonstrate a modulation scheme for mitigating this problem. We use a simple and effective model to evaluate this problem. We show the quantity of XPM-induced polarization-state fluctuations and induced system penalty for different conditions. In order to overcome this problem, we propose and demonstrate a novel intra-bit polarization modulation (IPDM) format.