Authored By Hui Chen
In Lasers & Fiber applications, often optical engineers need to simulate a beam with Gaussian intensity profile. OpticStudio offers three methods to model Gaussian beam propagation.
The first is the ray-based approach. By turning on the Gaussian Apodization settings in System Explorer, the beam will have a higher ray density at center and lower ray density towards edge. This creates a Gaussian intensity distribution and will have an impact on many ray-based analysis results, including RMS spot radius, Wavefront error, etc.
The second tool is Paraxial Gaussian Beam analysis. This tool computes the propagation and transformation of a rotationally symmetric Gaussian beam using two paraxial rays in a meridional plane. It computes ideal and mixed mode M-squared Gaussian beam data, such as beam size, beam divergence, and waist locations, surface by surface as a given input beam propagates through the lens system.
And the third method is the wave-based Physical Optics Propagation (POP) analysis. Physical Optics Propagation models optical systems by propagating coherent wavefronts. The beam is represented by an array of discretely sampled points, storing both the amplitude and phase of the electric field. The entire array is then propagated through the free space between optical surfaces. At each optical surface, a transfer function is computed which transfers the beam from one side of the optical surface to the other. Because the beam is described by its complex-valued electric field in the array, Physical Optics Propagation allows very detailed study of arbitrary coherent optical beams, including Gaussian or higher order multi-mode laser beams of any form (beams are user definable), or diffraction effects far from focus. The physical optics model is generally more accurate at predicting the detailed amplitude and phase structure of the beam away from focus than conventional ray tracing, but it’s also more computationally intensive and generally slower than running geometric ray-based analyses.
If you are interested in diving into this topic more, we have a series of four KBAs describing how to use these tools to model Gaussian beam propagation at: