Ansys Zemax - Polarization Basics

Ansys Zemax - Polarization Basics Hello everyone, my name is Charles Taylor, Zemax application engineer for Ozen Engineering.

Today I'm going to show a video about polarization in Zemax, various polarization states, how Zemax accepts polarization, where it comes from, and how it's used in the application.

So Zemax is up, I've got an optical system here, nothing too crazy about it, just an entrance pupil diameter of 10, and then we're pushing 50 millimeters past the stop. So there's really no optical components in here.

I'm doing this on purpose to illustrate the states of polarization first, and then how we look at polarization, how we can analyze it in Zemax. In the System Explorer is how we set for sequential mode, by the way. This is for sequential mode.

Non-sequential mode, you have to control it by the source. You put the source in and then you control it in the same form. It actually accepts the Jones matrix form as well.

So if we expand the polarization tab in the system explorer, you'll see if usually this polarizes checked, or this unpolarizes checked, but we want to uncheck that.

and you'll see JX, JY, X phase, Y phase and these are the inputs to control our polarization for our system for the starting point and so the default is up and what does it mean, where does it come from, and how do we control it and understand it.

Okay, so this is the overall form of a Jones vector, a Jones matrix, and there's a reason that Zemax uses this. It's because it's very convenient when talking about polarization. So I'll pull up the blog post that this video is sort of summarizing. There's two parts to it, but it's at ozeninc.com.

So first the polarization is basically tracking the electric field orientation or the direction of the vector and how this vector is oscillating.

So if we're assuming that our plane wave is traveling along the z-axis and we look down the z-axis this way towards the zero zero point, then we're going to be looking at a plane and that vector is going to move, it's going to be constrained to a certain type of movement that is given by the A-hat down here.

So this is the equation of the plane wave traveling along the z-axis. This A-hat is the polarization vector or the Jones vector if we relate it to it correctly. So we can expand this.

In general this is complex but we're going to look at the real component of the x and real component of the y and then the phase difference in the complex exponent here.

and so the we ought to relate this to the equation a hat so if we look J X is the real component in the X J Y is the real component in the Y and then X phase and Y phase is the phi and so this this fee is the phase difference and typically it's X phase minus Y phase okay so So we can learn a lot from choosing very specific things for these inputs So first I show this table which is useful This table is from Professor Tom Milster at the University of Arizona But it's very useful.

And it shows that when phi is zero, we have this zero or pi, we have a linear state. When the phase is between 0 and 90, we have an elliptical. Then when phase is pi over 2 or minus pi over 2, we have a circular. From pi over 2 to pi, we have an elliptical again.

This topic makes polarization much more simple and straightforward to understand. So the next thing I'd like to show you is how this looks in a vector notation and you can do this mathematically. So you can calculate your polarization state mathematically using these vectors.

So linear and x is 1, 0. We're tracking the Jx and the Jy and the phase. Remember the phase for linear is zero, so you plug zero in for phi, the exponent, exponential j to the phi is just one.

And so linear, and you can see that here in the 45 degree case, and then the right hand circular and the left hand circular case, it's one minus j and one j.

j equals the exponential of the imaginary times π over 2 and so for left-handed circular we have positive π over 2 which is going to be j and then for right-hand circular we're going to have negative π over 2 for the phase difference which is going to give us right-hand circular.

This is very convenient because you can put a matrix of an optical element and you can work this out by hand so you have an idea of what your polarization state should be after it passes through.

It's always good practice as an engineer when using Zemax to question whether the result in your simulation is accurate or not. If we run this macro, we'll be able to get an output in Jones matrix form.

So if we run the macro, by the way you go to programming, edit, run, and once you have this downloaded or created, you can find it here. If you execute the Jones Calc, it will perform a raytrace and provide you the details.

We already knew that the phase difference is 80. This is going to work if you change the state so we have to edit first and so the ray that going to be traced is defined here and then the rays that This is a good example because this happens sometimes and you wonder why your polarization state doesn't match and it's because you have the wrong definition of your polarization input.

So our polarization inputs match now and so this macro should calculate the correct polarization state.

We already know the phase difference is 80, but sometimes when this is a complicated difference, especially after a few optical components, we want to know the exact phase on each component and not just the overall phase.

Okay, so we have to save this and then we execute, we run, and now we'll get our polarization state phase X in this case. Let's check our text. Okay, so our field, we're looking at the minus 0.5 minus 0.5 field, or not field, but pupil coordinate.

So minus 0.5, we need to go to minus 0.5 minus 0. 5. There it is. It took me a minute to find it. Okay. So in this case the phase difference, so what do we have here? We have Ex, we have Ey, we have intensity and phase degree. So what is this? So Px and Py are the normal pupil coordinates.

Ex is the electric field, the magnitude of the EY is the magnitude of the electric field and the Y intensity and then the phase degree.

This is the difference in phase and so we have a phase difference and but we don't have the actual components of phase like what is the phase of the X and what is the phase of the Y and that's where this macro will help us.

So we can match it here, our macro says AX is .707, that's correct, AY is .707, phase X is 47 degrees and phase Y is negative 32. And without this calculation we wouldn't have known the actual phase of each component, we would have just known the difference, which is 80 degrees.

and then now we also have calculation of the major axis length because it is elliptical and the minor axis length and then the angle between the major and the x-axis is 45 degrees also you can see it here as the orientation.

So you can use the text to see your polarization state in Jones form or you can use a macro. There's also one more way that you can do a very similar thing. So the macro is just doing a polarization raytrace. So you can also come to polarization and click this polarization raytrace.

It's pretty much the same thing except the macro is pulling out very specific items from this polarization raytrace. So this has a lot of information on it. And so what we're pulling out of here is some of the stuff down here. Okay, that's all I have.

Hopefully that's a good overview of input and output of polarization. Please contact us at https://ozeninc.com/contact for more information. Thanks for watching!