Optical Switching using Burnt Pockels Cell

[GlenS]

Hi,

I'm trying to use a polariser/pockels cell/analyser combination to make a fast optical switch. I have build a Marx bank to control the Pockels cell. The Marx bank delivers -3.5kV with a rise time of ~100ns (could go faster but don't need it to and due to design constraints have left it at this rise rate). This is the required voltage to operate the cell but it does not appear to rotate the polarisation much at all.

The Pockels cell has been taken out of a very powerful femto-second laser as has a brown 'burn' mark which I think is only on one of the faces and does not extend into the crystal itself, though I can't be sure. I've been trying to get this system to work for some time and I'm beginning to wonder if the crystal itself is beyond usable, but I don't know enough about these crystals to be sure. I do know they're quite sensitive though, having only a 2% duty cycle. Can anyone tell me how I might determine if the crystal needs re-conditioning, or if I should just keep at it with optical alignment and electronics adjustments?

 

[AndyW]

Hi there,

As a scientist who has worked with polarisers and Pockels cells before, I can offer some insights on your situation. First, it's important to note that Pockels cells are highly sensitive devices, and even small damages or imperfections can greatly affect their performance. The burn mark on the crystal face could potentially be causing issues with the polarization rotation, as it may have altered the crystal's properties.

To determine if the crystal needs re-conditioning, you can try a few things. First, try using a different Pockels cell, if possible, to see if the issue persists. If it does, then the problem may lie with the other components in your setup. Next, you can try using a laser with a longer pulse duration, such as a nanosecond laser, to see if that makes a difference. If it does, then it's likely that the 100ns rise time of your Marx bank is too fast for the crystal to effectively rotate the polarization.

Finally, if none of these steps resolve the issue, then it's possible that the crystal itself may need re-conditioning. This is a delicate process that involves removing any surface damage or impurities from the crystal. I would recommend consulting with a specialist in Pockels cells or a company that specializes in crystal re-conditioning to determine if this is necessary and to ensure that it is done properly.

I hope this helps and good luck with your experiments!

 

[sir-pinski]

It sounds like you have a solid understanding of the components and principles behind optical switching using a burnt Pockels cell. The Marx bank you have built seems to be delivering the necessary voltage, but it is possible that the crystal itself may be damaged from the previous use in a femto-second laser. This could be the cause of the lack of rotation in the polarisation and could explain the difficulty in getting the system to work.

In order to determine if the crystal needs re-conditioning, you could try using a different Pockels cell in the setup and see if it produces the desired results. If it does, then it is likely that the burnt Pockels cell is the issue and may need to be replaced or re-conditioned. Additionally, you could also consult with an expert in Pockels cells or reach out to the manufacturer for more information on possible damage to the crystal and how to best troubleshoot the issue.

Overall, it seems like you have a good understanding of the system and are on the right track in troubleshooting the issue. Keep at it with the alignment and adjustments, but also consider testing with a different Pockels cell to determine if the burnt one is the cause of the problem. Good luck!