Derivation and application of a Green function propagator suitable for nonparaxial propagation over a two-dimensional domain.

The goal of optical simulation is to determine the performance characteristics of an optical system from a knowledge of its physical construction and how it affects light sent through it. To produce meaningful results efficiently, two simulation approaches are available for passing light through a system, geometrical raytracing and wave optics. Within the wave optics realm, there are many techniques for determining the optical fields within a system, both numerical and analytical. A few of the numerical techniques are finite-difference, finite-element, and FFT-based; analytical techniques include modal expansions, coupled wave theory, series expansions, and Green function propagators. A propagator is a function that gives the light fields at any specified location if they are known at a source location; this is possible because the light fields, electric and magnetic, satisfy a differential equation, in the case of time harmonic fields, the Helmholtz equation. The propagator is a transfer function for the fields and often takes the form of an integral, in which case, the integrand is a product of the transfer function with the source field distribution, and the integration is performed over the source field coordinates. The integrand transfer function, also known as a Green function or propagation kernel, is a solution of the Helmholtz equation. An approximation is often used in finding a solution to the Helmholtz equation, called the paraxial approximation, in which the second derivative in the propagation direction is dropped. If no approximation is made, and all second derivatives are kept, the solution is nonparaxial. In the present paper, a Green function for the propagator of the Helmholtz equation over two-dimensional domains is derived, differing in functional form from previous work on two-dimensional propagation. An angular spectrum integral is evaluated and the resulting Green function, the propagator kernel, is a nonparaxial analytic solution of the Helmholtz equation. The propagator could be applied directly to the electric and magnetic field components; instead, it is applied to the Hertz vector components. The Hertz vector is a potential function, similar to the vector potential, defined such that the electric and magnetic fields are found by taking derivatives of it. An advantage of the Hertz vector is that only it needs be propagated, versus two, electric and magnetic, vectors. In this paper, the derived propagator is applied to Hertz vector components defined by Legendre polynomial expansions, and derivatives are taken of the propagated Hertz vector components to calculate the associated electric and magnetic fields. The Green function propagator and all field quantities produced by its application are closed form analytic expressions.

Study of a reflection grating used in Littrow mount.

The near and far fields of a finite conductivity metallic grating with symmetrical triangular facets, used in Littrow mount, are studied. A new Green's function approach, based on the Hertz vector, is introduced and used to propagate throughout a two-dimensional domain. The field quantity of primary interest is Poynting's vector; however, the stored power is also calculated. In assessing the fields generated by the propagator, a quasi-periodic dependence of output characteristics on the grating depth to period ratio, discussed in the literature, is also found in the present study. With a plane wave incident on the grating, geometrical relationships between the incident wave vector and the grating surfaces have interesting consequences.

Developing a facility strategy.

Successful planning for capital investment relies upon the ability of the management team to establish a cogent and comprehensive direction for facility development. The selection of an appropriate strategy integrates multiple issues: mission, service needs of the community, the external environment, the organization's ethos, current physical resources, operational systems, and vision. This paper will identify and discuss key components and data integral to formulating a facility strategy that outlines the basic direction for developing a facility master plan. The process itself will be presented as a working methodology that can be applied to the organization's resources and vision to generate a coherent facility strategy.

The impact of aging infrastructure and site on facility planning.

Infrastructure analysis should be a basic component of the facility master plan and specific information concerning the site and facility must be collected, evaluated, and analyzed at each phase of development of the master plan. The interpretation of such information can significantly impact the visibility of design solutions, department locations, construction phasing, and costs. This paper identifies the information to be collected, its potential impact on the master plan, and the facility manager's role during the planning process.