Huiying Zhong

Tilt operator for electromagnetic fields and its application to propagation through plane interfaces

This article introduces an efficient tilt operator for harmonic fields. In optical modeling and design, a field tilting operation is often needed, e.g., the propagation of a harmonic field between non-parallel planes, since most of the existing propagation operators only deal with the case of propagation between parallel planes. Such operator enables the modeling of various optical components, like the case of prisms and tolerancing with tilted components. The tilt operator is a rigorous method to calculate vectorial harmonic fields on tilted planes. The theory applies a non-equidistant sampling in the k-space of the field before rotation in order to obtain an equidistant sampling of the rotated field. Different interpolation techniques are employed for the non-equidistant sampling in the k-space of the initial field and their performances are evaluated. Besides the tilt operator, the propagation method of harmonic fields through planar interface is proposed as well. The application of both methods makes it possible to model a sequence of tilted optical interfaces, e.g., prisms. At the end of this article, a dispersive prisms example is presented. All simulations are done with the optics software VirtualLabTM.1

Parabasal thin-element approximation approach for the analysis of microstructured interfaces and freeform surfaces

The thin-element approximation (TEA) approach is an efficient algorithm to analyze microstructured interfaces, e.g., diffractive optical elements or scattering surfaces. However, the classical approach is valid only under the condition of paraxial illumination. We hereby develop an extended algorithm to include parabasal illumination, which is characterized by low divergence with arbitrary propagation direction. The extended approach is named as the parabasal TEA approach. In this paper, we present the algorithm of the parabasal TEA approach and compare the results with that of a rigorous calculation in order to demonstrate its validity. We also discuss the role of the parabasal TEA approach in a more general concept for modeling light propagating through freeform surfaces.

Parabasal thin element approximation for the analysis of the diffractive optical elements

The thin element approximation is an efficient algorithm to analyze diffractive optical elements (DOEs), whose feature size is large enough compared with the working wavelength. However, the thin element approximation is only valid under the condition of normal illumination. We hereby extend an algorithm, which is called the parabasal thin element approximation, to include the non-perpendicular illumination. More specifically, the thin element approximation is valid for paraxial incident beam, while the parabasal thin element approximation is valid for parabasal beam. In this article, we present the algorithm of the parabasal thin element approximation and compare the result with that of rigorous method. All the simulations are based on field tracing and done with the optical software VirtualLab™.

Comparison of modelling techniques for multimode fibers and its application to VCSEL source coupling

Ray tracing and split-step method are the most efficient techniques to model multi-mode fiber. In this work, we also propose a geometrical optics based approach, which is beyond ray tracing. This approach, which is mathematically based on Runge-Kutta methods, handles not only ray information but light field information, e.g. amplitude and polarization. Then we discuss and compare the different techniques by the example of coupling of a VCSEL source into a multi-mode fiber.

Approximate solution of Maxwell’s equations by geometrical optics

Ray optics has constituted the fundament of optical modeling and design for more than 2000 years. In recent decades, the introduction of ray tracing software has brought a powerful optical design technology to everybody dealing with optics and photonics. However, with the development and availability of advanced light sources, the capability to produce micro and nano structures, the need for high NA systems, and a boost in the variety of applications and related demands on optical functions, the limitations of ray optics become obvious more often. Optical modeling based on physical optics is required and is the logical next step in the development of optical design. This requires a generalization of ray tracing and its connection with diffractive modeling techniques.

Shaping and homogenization of LED white light using aperiodic scattering cell arrays (Conference Presentation)

Shaping of LED white light is of increasing interest for several industrial applications. There are several known design concepts available. However these concepts suffer from high uniformity errors, low efficiencies, chromatic aberrations and/or high tolerance sensitivity. To overcome these limitations we present a novel design concept which is based on the design of aperiodic scattering cell arrays. In a first design step, a unit scattering cell is designed. Afterwards this cell is periodically replicated. Finally the periodicity of the array is broken using parametric optimization. Obtained design results are compared with experimental data.

Modelling and design of modified Wollaston prisms and the application in differential interference contrast microscopy

Wollaston prisms and the modified Wollaston prisms, which are interesting for various applications like optical metrology, topography of surfaces and biological imaging, has been theoretically studied and also been practically applied. The previous studies are mostly based on ray tracing analysis and, as a result, the information that can be obtained are somehow restricted. In this paper, we propose a geometric field tracing technique for the simulation of light propagation through Wollaston prisms. In geometric field tracing we seek for the solutions to Maxwells equations under the geometrical optics approximation, so that all the properties of light as electromagnetic field are retained. Using the proposed simulation technique, we present the simulation of a differential interference contrast (DIC) microscopy, in which the modified Wollaston prism is used as the key component.

A smooth field decomposition applied to modelling of scattering phenomena

In this work the authors investigate the potential of a smooth field decomposition method to improve simulation efficiency in modelling scattering situations. Two examples of particular simulation set-ups are presented and analysed.