How to model harmonic generation

  • 12 February 2020
  • 3 replies

I am just starting to learn Zemax. Now I am trying to simulate my laser, which can generate Green light by external second harmonic generation. My simulation result for the fundemental beam is very close to the measurement data. To simulate the harmonic beam, I assume that a) harmonics beam and fundemetal beam have same M2 and divergence, b) harmonic beam waist location is at nonlinear crystal center. However the simulation result (beam size and divergence at far field) for harmonic beam does not match real harmonic beam (measured by laser beam profiler) at all. Can anyone help me? how can I model harmonic generation in Zemax

3 replies

Userlevel 6
Badge +2
OpticStudio does not currently model the optical effects of non-linear crystals.

However Lumerical for example can correctly model this and interfaces with OpticStudio. The links below are webinars on using Lumerical with OpticStudio.

Zemax and Lumerical: Part 1 - from nano-scale to macro-scale optics and back - webinar

Zemax and Lumerical: Part 2 - from nano-scale to macro-scale optics and back - webinar

These particular webinars focus on beam files and complex fibers, but their help files detail modeling non-linear crystals as well.


Hi, I’m new to zemax. Could you explain your response Sandrine Auriol? I have a KTP crystal and I don’t know how to do the simulation. Many thanks.

Userlevel 7
Badge +3

Harmonic generation is a two-photon process. Two photons do in at wavelength lambda and one emerges with wavelength 2*lambda. The two photons must be phase matched to conserve momentum.

Ray tracing models light as individual particles (not really photons) and there is no interaction between rays. So sadly, ray tracing cannot model non-linear, or multi-photon, effects.

Lumerical’s codes work with electric fields directly, so you can model a medium that has a non-linear relationship with field intensity.

  • Mark