Linear, Circular and Elliptical Polarization Animation in a Single Shot

[jethomas5]

Try two kinds of motion. In one of them, the E field rotates around an axis which is tilted compare to the direction of motion. So it sweeps out an elliptical pattern which sometimes rushes ahead and sometimes falls back. Your elliptical wave looks like this to me.

In the other, add a circular polarized wave to a linear wave. The result is like the circular wave but expanded in one direction that's normal to the direction of travel. A different ellipse.

Is elliptical light like one of these?

[meyavuz]

@jethomas5

Hi... For the first case, if the E field rotates in a tilted plane to the direction of propagation, then it does not satisfy the plane wave condition so it is not possible. So, my simulation above is not like that, rather at any spatial point the electric field in the above animation is always perpendicular to the direction of propagation. If you look at my other videos on polarization you can explicitly see the two components (Ex and Ey) making the elliptical wave.

[meyavuz]

@jethomas5 Regarding the second approach (summation of linear and circular polarization), this time it is valid elliptical polarization and my simulation is actually similar to this.

Elliptically polarized light is similar to the second option of yours.

Thanks

[jethomas5]

@meyavuz

I agree that's how it ought to be. That isn't how your simulation looks to me. When I imagine the third dimension, it looks like your picture involves a constant angular rotation and a tilted ellipse with the center at one focus. When I remind myself that the blue ellipse is flat against the grid then I can see it your way, but it's easy to see the blue ellipse tilted too. I don't know how to set up the perspective so that looks right. No criticism that you didn't either.

[meyavuz]

@jethomas5

Yes, it might seem like that but I can assure that electric field components are completely orthogonal. Actually, if you see my previous simulation

( youtube.com/watch?v=KZz25bmTWX­o ), there I just showed the Ex and Ey component separately, whereas here I show the total field (x^ Ex + y^ Ey).

While recording, I tried other angles for different perspective but this came to be best one for me. If you want I can send the original Matlab code. Let me know. Thanks

[jethomas5]

@meyavuz

I suspect it might be easier to see if it's vertical instead of diagonal. Have the y axis be the longest one and the x axis the shortest. But you've actually done the work while I'm only guessing.

I'm pretty sure it would be easier to see if it gradually changed from linear to circular and back, and then the perspective started to shift also. But that's a whole lot of work.

[meyavuz]

@jethomas5

Thanks for the idea of gradually changing from linear back to circular and shifting perspective also. I plan to implement it in the upcoming weeks and I will send you a message once I upload it. Thanks again for the idea.

[wa6tkq]

The "point" I refer to is not a spatial point but a point on the moving wave. Suppose you take a short ribbon and twist several turns in it and hold it horizontally in the forward direction and walk in that forward direction. The ribbon does not rotate as it travels. If you stare at a fixed point in space when the ribbon passes thru it the ribbon rotates with time. Circ Pol causes time rotation but not space rotation. There is no way an E vector can be spun at the carrier rate as it propagates.

[meyavuz]

@wa6tkq Thanks for the comment again. Here, the space is fixed, i.e. this is not a section of moving wave for increasing spatial points. every point in the z-direction is a single point in space and I plot the time-domain progression of the wave as it passes through the same spatial points. Hence, as you mentioned, this is rotation in time at a constant spatial point. I have mentioned this in the description of the animation. Regards,

[wa6tkq]

The circular animations are incorrect. The red radial vectors should not rotate as they move in the Z direction. Your other video which shows the circular polarization vector as two orthogonal components (red and blue) is correct. At any point in the wave the red and blue component remains constant in amplitude as that point propagates in the Z direction. Since the two components remain constant in amplitude the angle of the resultant radial vector remains fixed and does not rotate.

[meyavuz]

@wa6tkq

Thanks for your comment but you are wrong. First of all, in your comment you mention that "... that point propagates in the Z direction". This is completely wrong: a spatial point does not propagate, it is always constant in space. Here I tried to plot the total Electric field vector at a set of constant spatial points. At any given point, the amplitude of the Electric field vector is always same and constant but due to phase difference between the X and Y components,

[meyavuz]

@wa6tkq

we see that rotation. If it does not rotate then it is linear polarization. For circular or in general elliptical polarization, rotation is inevitable. Please, see the following third party animations as well:

youtube.com/watch?v=kLvkAGAUMX­w

youtube.com/watch?v=J4FEKWuXp1­U

Regards,

[ratitaanita]

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[crazylovergrl]

What is the definition of light polarization? Is it the change in plane of the oscillation or the general shape?

[meyavuz]

@crazylovergrl

Simply put, polarization is the orientation of the electric field component of a plane wave as it travels in time. Regarding the video above, you can consider the blue lines as the polarization of the wave. In the linear polarization, E field oscillates along a linear line whereas for the circular polarization electric field rotates along a circular path. I hope this is clear. Thanks