How to further improve the performance?

[SimianZhu]

Hi everyone,

Glas to be here and thanks admin for let me in, I heard about the OPENRAMAN project few years ago but until recent I finally recieved some funding from my university that allows me to build my own setup for my SERS study.
To make it even better, I live in China, which means I can get much cheaper components from Chinese vendors, so I upgared the laser to the CNI MGL-III-532-50mW Laser, and the grating also be upgrated to 2400/mm, still have ~$400 budgets left, so I would like to know how to further improve the performances of it?
Considering I need to use it for SERS study, my target is to improve the spectral resolution of the spectrometer, so my plan is to change the camera with a better CMOS, considering Sony IMX178 or IMX183, the IMX178 has the same sensor size as the IMX265 in FLIR BFLY-PGE-31S4M-C, but with higher resolution and smaller pixel size, while the IMX178 has bigger 1' sensor size and even higher resolution, but I'm a bit worried about the size differences, is that mean I need to change the lens as well for fully utilising the frame of the sensor? And if I do so do I need to change the base plate design as well...(that's already beyond my expertise...), or is there anything critical that I missed, please let me know in the comments.
Thanks for reading, I will update regularly about my work once I start to build.

[Luc]

Hi,

Yes -- I had to enable account verification due to the amazingly high number of spam we were receiving despite the various captcha...

About resolution, it's a complex topic because you have to take into account:

• The limitation of the experiment itself. Peaks have a natural width and it's not possible to increase resolution above that limit. This can be observed in all molecules and good examples are i-PrOH and nitromethane which have a very sharp peak near 1000 cm-1 but all other peaks are broader.
• The limitation of the laser. High resolution in Raman requires a laser with a very high spectral purity. the MGL-III I have from CNI is about 0.15 nm larger which is limits resolution to 5 cm-1 in the absence of other limitations.
• Optical quality of the slit image. Resolution is also bound by the size of the slit's image. Decreasing the slit size is possible until you reach the PSF of the optical system (the system is then "well balanced"). Having tight PSF on large angular range is difficult to achieve and requires expensive optics.

The current system results from a tradeoff on all these points (and others). I choose an optics that was giving a PSF size about the size of the laser limitation and selected the slit that balanced this system. The overall can theoretically measures down to 8 cm-1 although all measurements were closer to 12 cm-1 -- maybe a limitation from the experiments themselves. It's a bit of an iterative process as well as I tried multiple configurations before settling to the current OpenRAMAN version.