Coherent Propagation

InteferometerIn addition to non-sequential raytracing FRED uses a sophisticated Gaussian beam decomposition algorithm to propagate coherent optical fields through the system geometry.

This proven, powerful technique makes it possible to model beam propagation through interferometers, holographic systems, lasers systems, etc with both accuracy and generality.

These are simulations that most of the other optical engineering software packages can not do.

In FRED, the implementation of this algorithm is largely hidden from the user. The user specifies the type of optical field (plane wave, diverging/converging wave, astigmatic laser diode, user-defined, etc) to be propagated and FRED creates and traces the secondary rays in the background. At the conclusion of the raytrace, FRED uses the ray information to recreate each Gaussian beam, and then sums the coherent field at the observation plane; the result is an irradiance, power density, or scalar field distribution at the user-specified spatial resolution.

The following short video shows the modeling of coherence effects in a birefringent ruby laser rod.


The capability to model coherent fields through macroscopic structures makes possible the design of applications that require accurate modeling in both the macroscopic and microscopic regimes. An example of which is the design of a digital camera system using a CMOS detector where design of the lens system requires non-sequential raytracing techniques - as provided by FRED - yet how the light is focused onto the CMOS detector needs to be modeled using a Maxwell solver such as FDTD (Finite Difference Time Domain).

Interoperability between the two different software packages require the exchange of the complex electric field distribution. This is only possible with a ray tracing software that uses the Gaussian beam decomposition algorithm.