From Refraction to Diffraction

1.1 Refraction and Diffraction Phenomena

In order to predict the behavior of light as it is affected when it propagates through digital optics, we have to consider the various phenomena that can take place (refraction, reflection, diffraction and diffusion). Thus, we have to introduce the dual nature of light, which can be understood and studied as a corpuscle and/or an electromagnetic wave [1].

The corpuscular nature of light, materialized by the photon, is the basis of ray tracing and the classical optical design of lenses and mirrors. The wave nature of light, considered as an electromagnetic wave, is the basis of physical optics used to model diffractive optics and other micro- or nano-optical elements, such as integrated waveguides, and photonic crystals (see Chapters 310).

In the simple knife-edge example presented in Figure 1.1, the corpuscular nature of light (through ray tracing) accounts for the geometrical optics, whereas the wave nature of light (physical optics) accounts not only for the light present in the optical path, but also for the light appearing inside the geometrical shadow (the Gibbs phenomenon). According to geometrical optics, no light should appear in the geometrical shadow. However, physical optics can predict accurately where light will appear within the geometrical shadow region, and how much light will fall in particular locations.

In this case, the laws of reflection and refraction are inadequate to describe the ...

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