Hi Nikodem,

I work at Fianium. The band you can detect at 590nm is caused by noise from the RF driver. The intensity of this band is very low but was a feature of that generation of driver. This has subsequently been removed in newer RF drivers. Please contact me, either at [email protected] or the website and we can discuss this further.

Paul

Hi Paul, thank you for your answer!

I had contacted Adam Devine and Erica Bricchi, as they were helping us with our Fianium setup some time ago, but they have not answered my e-mails yet.

The intensity of this band is high enough to be visible by naked eye, not to mention our equipment.

I can contact you but I would prefer to use an personal e-mail, I avoid using generic e-mails as support@, sales@ etc, as using this usually takes longer than contacting responsible people directly. On the other hand I do not see why we can not continue our discussion here, maybe it will be useful for someone else.

If this is a noisy RF driver is there any way of improving it's work? Or only sending it to you to have it reworked?

In this region of the spectrum the eye is quite sensitive so I believe you would be able to see the output even if the intensity is low. Did you measure the intensity of the band with your equipment?

As this leakage was present in each driver from this generation the only way to remove the band is to replace the driver with a newer model.

Yes, the eye is quite sensitive, that's correct but still - this is quite much, on the order of few tens of microwatts on out sample. One can easily see this on emission spectrum of the investigated sample (we use backscatter architecture of an experiment).

Do you have any suggestions how to proceed with this problem? I have contacted Fianium, as mentioned earlier, but maybe there is something that could be done 'at home'?

Nikodem,

Paul provided you a solution, which is to replace the driver. Perhaps you missed that part of his email. This is a best and ultimate solution to your problem, eliminate the noise. Thanks for sharing. We all learn along the way.

Jannick Rolland

Hi Nikodem,

Depending on the wavelength you could use high or low pass filters; a sharp cut-off would be best to reduce any range the in the working region. The range of the AOTF is not large enough that the filters will be difficult to find either.

Has this always been a problem?

Hi all,

The ultimate solution is to replace the driver unit with the latest generation which has the noise removed. Sean's suggestion of using high/low pass filters to remove the parasitic band is the best solution without having to change the drivers.

My email address is [email protected] if you have any other questions.

Hi Sean,

This was normally present in all the old driver units; we spoke to the supplier who told us that the driver runs at 100 MHz and leakage from the CPU into the RF channel caused the corresponding wavelength to be present at all times. Normally the intensity of the leakage is too low (~nW) to be detected by equipment but can sometimes be seen by the eye. We were told previously that it was not possible to remove this but we found it was removed in the new generation when we tested it (the manufacturer never even mentioned it to us).

Hi all,

Sean, using optical filters - be it bandpass or short/highpass - is a great solution looking at the spectrum, as with them one can just forget about an AOTF even, but exchanging filters distorts the alignment of the setup quite badly, and this is a thing that you really hate in a confocal microscope (obviously). This is the main reason why we really want to use the AOTF despite its drawbacks (when compared to a set of fine, narrow bandpass filters).

Paul, I'll write you an e-mail to make it official. I have consulted my supervisor about this and fixing the RF driver in order to get rid of the noise/yellow leak.

Is it possible to filter out the noise between the driver and AOTF? I imagine I could make an RF filter and place it there.

Thank you both for help.