Show smallest waist and its position in "Beam Data"

[gregor-anich-uibk]

Hi,

first of all thanks a lot for providing this really cool tool for free and even open source.

A nice feature would be if in the "Beam Data" table one could see the position and size of the smallest waist for the different segments of the beam. I need to mode-match a beam to a cavity, so I modeled the cavity to get the waist on the mirrors, and now I propagate the beam backwards out of the cavity to see the required shape of the beam I have to send in. Since I need to come in on the curved mirror, it acts as a lens and the position and size of the waist for the incoming beam is not equal to the eigenmode of the cavity. It would be cool if I could see the required position and size of the input beam waist in the "Beam Data" table.

Another feature I would find useful is checkboxes in the "Schema" table to quickly disable elements without having to delete them.

Greetings from Austria, Gregor

[Chunosov]

Hello Gregor, thanks for your kind recall!

I agree with checkboxes, they are even were in the old version 1 of the app, but then I decided to drop them when moved to the version 2, because I personally was not using them at all. They can be returned.

Could you please elaborate a bit more on the first feature. If we take the simplest case of two mirror cavity with the waist at (almost) one of the mirrors. What do you expect should be shown in the Beam Data?

[gregor-anich-uibk]

Hi, with the cavity that you show the input mirror will act as a lens, so the beam needed to hit the Eigenmode of the cavity will have a different waist and waist position than the Eigenmode inside the cavity. It would be convenient to see these parameters directly (of course they can be derived from the other parameters given in the "Beam Data"). The attached screenshot of the "Gaussian Beam" software illustrates what I mean ("Waist" and "Waist position" columns). The (smallest) waist and waist position are changed by each element and it would be cool to see them for each section of the beam directly in the "Beam Data" table.

Edit: It would also be nice to have a "Notes" textedit to store some notes with the project 8-)

[Chunosov]

Hello Gregor

Agree about notes, I had the same idea some time ago, then it felt out of scope for some reasons. Glad it was the right idea :) added it to the list.

I'm trying to understand the problem and how it can be solved generically. I checked the "Gaussian Beam" tool, all seems clear there. It calculates how a Gaussian beam traverses several optical elements. The column "Waist position" shows where the waist would be if we didn't have the next element. E.g. in my picture below d1 is a distance on the imaginary ruler to where L1 would focus the beam if we didn't have L2. And having L2 the focus will be at the distance d2.

rezonator calculates mostly the same for SP systems. You setup an input beam, and it calculates the beam shape during traversing of all elements.

The exception is it doesn't show these "intermediate" waist sizes/position like d1 in my example above. It is what you need be shown in the "Beam Data"?

But it is for SP systems. Because for resonators (SW and RR systems) I don't see how this could be calculated unambiguously and what this gives. Let's we have a cavity consisting of two mirrors and with an eigenmode waist somewhere inside (the red beam on the fig a below). Then we say, "I want a green beam which will match the red one inside the cavity, but I know the beam will be different outside of the cavity because one of the mirrors plays as a lens for that beam". Then we calculate a waist size of the green beam as if we didn't have M1 (see the fig b below) and a position of the waist (relative to what? we don't have an imaginary absolute ruler there).

So my concerns are

• if I understand right that you try to match a pump beam to resonator mode?
• what gives the knowledge of waist of the green beam in the absence of M1 if we don't know what a system has produced this beam? (in the "Gaussian beam" tool we always know the position and size of the input beam)
• what if we have more complex system (e.g. some M0 before M1), should we try to match the green beam to the red one in each section M0-M1, M1-M2 independently?
• that beam which should match the eigenmode probably will have even a different wavelength?

So my point is not about this is something impossible to do, but rather I doubt that the "Beam Data" is a good place for these values. Because they would be "a data of another beam" then :) And to decide what is the right place, we have to try to define the task properly. Maybe it already have some different solution, and maybe it worth another function, other than "Beam data".

-- Nikolay

[orion-project]

Close due to lack of activity. Please reopen or make another one when some clarifications available.