Raman Spectroscopy Setup Not Functioning as Intended

[Bogthornder]

TL;DR Summary

I am attempting to reuse components of an old Raman spectrometer, and cannot obtain any signals.

I am attempting to revive an old Raman spectrometer that had a few components stop working. I was left with a functioning probe head, laser system, and some optical components. Currently, I have purchased a new CCD spectrometer and a few optical components to replace those that were specific to the old CCD. Now that I have the entire set-up assembled, I am not able to obtain any sort of spectra, or any signal at all. The only signal I can obtain is noise, and even when using calibration lights there is no signal obtained. More specifications about the system are below:

Laser: Adjustable with a maximum power of 400 mW, 785nm wavelength.

Probehead: Constructed by Kaiser Optical (now defunct)
Spectrometer: ThorLabs CCD175
Laser Filter: Thorlabs FELH0800 Edgepass Filter (Cut on wavelength is 800nm)

Components are arranged in the following fashion:

Laser > Fiber optic > Probe head > Sample > Probe head > Fiber optic > Free space coupling mount > Laser Filter > Fiber optic > CCD

I have attempted to vary the exposure times, change the laser power, and use software for spectral analysis to retrieve any information, but it appears that the set-up is not actually producing any usable signals. The sample I am using to test the set-up is a polystyrene standard. Some additional steps I’ve taken in troubleshooting:

• Removing the filter from the path to ensure that the path functions as expected. When the filter was removed, light can be detected by the CCD however it is only the laser light and there appears to be no Raman signal despite the probe head’s internal filtering.
• When a white light is shone into the probe head without the filter, light can be detected including light above the 800nm cut on. However when the filter is added this light disappears. Using this light source with the filter along, there is infrared light being transmitted through the filter that can be seen with a camera.

Does anyone have any suggestions for parameters that can be tested to determine where the system is failing to work? I am happy to provide any additional information that could be useful in the diagnostics.

 

[sbrothy]

TL;DR Summary: I am attempting to reuse components of an old Raman spectrometer, and cannot obtain any signals.

I am attempting to revive an old Raman spectrometer that had a few components stop working. I was left with a functioning probe head, laser system, and some optical components. Currently, I have purchased a new CCD spectrometer and a few optical components to replace those that were specific to the old CCD. Now that I have the entire set-up assembled, I am not able to obtain any sort of spectra, or any signal at all. The only signal I can obtain is noise, and even when using calibration lights there is no signal obtained. More specifications about the system are below:

Laser: Adjustable with a maximum power of 400 mW, 785nm wavelength.

Probehead: Constructed by Kaiser Optical (now defunct)
Spectrometer: ThorLabs CCD175
Laser Filter: Thorlabs FELH0800 Edgepass Filter (Cut on wavelength is 800nm)

Components are arranged in the following fashion:

Laser > Fiber optic > Probe head > Sample > Probe head > Fiber optic > Free space coupling mount > Laser Filter > Fiber optic > CCD

I have attempted to vary the exposure times, change the laser power, and use software for spectral analysis to retrieve any information, but it appears that the set-up is not actually producing any usable signals. The sample I am using to test the set-up is a polystyrene standard. Some additional steps I’ve taken in troubleshooting:

• Removing the filter from the path to ensure that the path functions as expected. When the filter was removed, light can be detected by the CCD however it is only the laser light and there appears to be no Raman signal despite the probe head’s internal filtering.
• When a white light is shone into the probe head without the filter, light can be detected including light above the 800nm cut on. However when the filter is added this light disappears. Using this light source with the filter along, there is infrared light being transmitted through the filter that can be seen with a camera.

Does anyone have any suggestions for parameters that can be tested to determine where the system is failing to work? I am happy to provide any additional information that could be useful in the diagnostics.

I'm probably not of much help but I'm curious as to whether you have drawings or diagrams of this setup of yours that you'd be willing to share?

 

[Bogthornder]

I'm probably not of much help but I'm curious as to whether you have drawings or diagrams of this setup of yours that you'd be willing to share?

Of course! I don't know why I didn't think to attach it before.

I don't have a lot of information concerning the probe head. I know it is a Kaiser Optical Systems Inc. Mk. II, but the documentation I have doesn't seem to contain any optical diagrams that I can find, but I thought I might attach an image of the internals in case anyone other than me can see something obvious.

 

[sbrothy]

Yeah, as I suspected it's beyond me. The reason I'm interested at all is because I wanted to realize a Raman mass spec using 3D printed parts. I started a thread along those lines here:

Apropos Raspberry PI DIY Mass Spec using Raman Scattering

Well, if nothing else I got your thread bumped.