Optical trap Raman - oil refractive index matching

[donroy81]

I have a Optical trap that collects Raman. With Glass cover-slips we use a 1.51 refractice index oil (DF cargille). The trap works but glass has high auto-fluorescence at our excitation wavelength(785 nm9), the weak Raman can't be detected. So we use synthetic fused silica cover-slips with a refractive index of 1.48. The trap is weaker (no numbers yet, but I have been doing this for a while). Should an immersion oil with a lower refractive index ( like 1.48 for cargille FF) work better? That would be a mismatch with the glass from the objective. Any clues?

 

[Valerie Park]

I would suggest trying to use an oil with a refractive index closer to the glass of the objective. Since the excitation wavelength is 785 nm, you could look for an oil with a refractive index that is close to 1.51. This would minimize the mismatch between the glass of the objective and the oil, and should help reduce auto-fluorescence. Additionally, some companies make special oils specifically designed for Raman applications, which may also help reduce auto-fluorescence.