Feasibility of simulating second-order cascading nonlinear effects in lwe

[889562]

Hi, there

While reading the references provided in your crystal library, I came across a discussion on second-order cascading due to phase-mismatched second-harmonic (SH) generation. Since lwe is capable of simulating SHG, I was wondering whether it's also possible to simulate this kind of second-order cascading nonlinear effect (e.g., leading to self-focusing or self-defocusing) using lwe.

I’m currently trying to set up such a simulation, but I’m still not sure whether the process is fully supported or how to best approach it. Could you kindly let me know if this is feasible in lwe? If so, I’d love to continue exploring it.

Thank you for developing such a powerful tool and for taking the time to consider my question!

Best regards

[NickKarpowicz]

Hi there, this effect will be there - it's simply what has to happen when SHG isn't perfectly phase-matched - the light is returned to the original pulses with a phase shift - try it out, and you'll see it happen :) Best wishes, Nick

[889562]

Hi there,

I’m getting more and more interested in your LWE tool — it’s really fascinating! I’ve started simulating part of an experiment from a paper, and so far things seem to be working well. In this simulation, I’m using φ = 30°, not φ = 90°. The experiment used a BBO crystal with φ = 90°. Should I simply set phi = 90 in the interface? https://opg.optica.org/ol/abstract.cfm?uri=ol-43-2-235

I’m still a bit unclear on how to properly set the beam waist in LWE. The tutorial mentions: Beamwaist: The Gaussian waist $w_0$. This is not necessarily the size of the beam at the start of the simulation, but the size the focus will have when the beam reaches it via linear propagation.

Could you kindly clarify how I can determine the actual beam size at the beginning of the simulation? If I set z offset = 0, does that mean the beam waist I specify is applied right at the start of the simulation domain?

Thanks a lot!

[NickKarpowicz]

The equation there is the right one to use - you set the value of $w_0$ (that's the beam waist specified on the interface), the Rayleigh length $z_0$ is determined by that value and the wavelength. z is the "z offset" in the interface. The way to think of it is, by the frequency and beam waist, you determine the mode, and the z-offset (and x-offset) help you position this mode in space. Does that make sense?