OpenRAMAN Suitability for Graphene

[mysticarc]

Hello Luc and Board,

I'm looking to build either the starter or performance edition of the OpenRaman project. We want to take spectra of graphene samples and was wondering as to the suitability of OpenRaman for this.

The graphene samples we will take is a mixture of few-layer and multi-layer graphene.

Obviously high SNR and a deeply cooled CCD are going to be the things of priority.

If it is suitable, would the starter edition be enough or would we need the performance edition?

As a side-question, would it be feasible to pull a vacuum (two-stage pump) so that the CCD can be further cooled down without a threat of condensation?

Thank You

[Luc]

Hi,

I have no direct experience with graphene but this is a question that pops up relatively often.

I wouldn't use the starter edition but one of the method below:

• https://www.open-raman.org/cni-mgl-iii- ... er-review/
• https://www.open-raman.org/fiber-coupled-laser-update/

About the CCD question: the current camera is not compatible with intense TEC cooling because it is not sealed and you will get condensation when going below a critical temperature (typ 10°C depending on your local humidity levels). I would recommend against CCD as they are a thing of the past, back-thinned CMOS having replaced them in all applications.

There are a few TEC cooled CMOS cameras but I don't have direct experience with them (yet). That being said, it's on my short list! There are a few options there but I was personally looking at Morovian cameras (brand).

[mysticarc]

Hi Luc,

I actually already have a fiber laser with a 0.1 nm linewidth, but it outputs to free-space. I think the performance edition baseplate would still be suitable, but please correct me if I am wrong.

For the CCD vs CMOS, I was talking to a professor that builds out these Raman spectrometers and he recommended against the CMOS because of high noise with longer integration times. Can you chime in on this?

[Luc]

You can definitely used the fiber-coupled add-on then

About the CCD/CMOS, that used to be true ~20 years ago but today CMOS have outperformed CCD even in long integration time. It is very difficult to have number for thermal constants which makes datasheet comparison difficult, but we can have a look at market trends on suppliers like Hamamatsu which is a known supply chain for spectrometers. In their spectrometer detector line, they have 65 CCD sensors vs 80 CMOS one. My feeling is that they still sell a lot of CCD because a lot of existing hardware is using them but the shift is towards CMOS. It would be interresting to test equivalent cameras (one in CCD, the other in CMOS) on my camera test bench (https://www.thepulsar.be/article/diy-ca ... nch-setup/) to have reliable figures.

[mysticarc]

Thanks for the detailed response! How do you feel about using the Hamamatsu S11639? That is the one I can readily buy with the driver board.

[Luc]

I would not necessarily recommend this sensor for two main reason:

• the pixel size which is incompatible with the current spectrometer; this would require changing the imaging lens and hence a complete re-study of the pupil effects
• single line sensors are a pain to align. I did it in the past and I switched to 2D sensor whenever possible because it makes alignment so easier

[mysticarc]

Understood. Do you have any recommendations for a cooled CMOS camera that will not break the bank ? Morovian cameras look quite expensive.

[Luc]

The morovian are actually relatively cheap cameras ; but they are not "true" cooled cameras as they are not made to work for extended period of time (they aren't fully sealed).

My plan was to TEC cool a regular camera just above dew point. But I have been quite busy this year and it's unlikely that I will resume that plan before 2026.

[mysticarc]

This seems to have all of the features that we need (-40 C delta), sealed, and has a dew remover built-in, for a decent price: https://player-one-astronomy.com/produc ... ra-imx585/ . Any thoughts?

Also, I want to use this for solid graphene powder. Normally in builds, there is a microscope objective aimed at the sample but I do not see it in your case. Where exactly would the sample go? In your other pages I see a cuvette holder but I don't see it in the diagram of the performance edition.

And also, why would there be no need for an expensive 100x infinity microscope objective in your setup?

Thank You!

EDIT: I saw this post: https://www.open-raman.org/build/cuvett ... d-cuvette/

It was posted 3 years ago and I see two points:

"Warning: we currently only recommend the solid cuvette for the Starter Edition. We are still validating the solid cuvette with the Performance Edition." --> Was this already validated for the performance edition?

"Warning: A user just pointed-out that the lens is not included on the drawing. It is however listed in the BOM and you can see it beneath the CP14 cage where it’s supposed to be. I will fix the drawing when I get my SolidWorks license in November." --> Do you have the updated drawing? I am not sure what lens it is referring to, and also where exactly is the position?