## Category Archives: diffraction

### Paraxiality

The previous post on the Gaussian beam noted that this beam is a solution to the paraxial wave equation and thus only accurate for small divergence angles. The limit given in [1] was $w_0 \gt 2\lambda/\pi$ or $\theta \lt 0.5\mathrm{rad}$ or $\approx 29^\circ$. The Gaussian beam model is of course not exact up to that […]

### Scalar Diffraction – Fourier

In an earlier post we had a look at various diffraction formalisms that either originated in the Huygens-Fresnel principle or led to essentially the same results. The principle modeled a field distribution in a aperture (or on a surface) as a source of infinitely many spherical waves whose amplitudes and phases were prescribed by the […]

### Scalar Diffraction – Imagery

In this post on the principles of scalar diffraction there were quite a number of integral expressions for diffraction of light, starting from the Huygens-Fresnel principle and applying various degrees of approximation. Integral formulations are usually very abstract and not very illustrative. However, with today’s available computer power we can turn these integrals into…

### Scalar Diffraction – Huygens, Fresnel, Fraunhofer

One can work years in fiber optic communications and not really have to care about diffraction, but when working with free-space light propagation and/or illuminated surfaces it’s better to know the difference between your Fresnel and your Fraunhofer diffraction, and what the heck the Huygens-Fresnel principle is all about.