Raman Tools
Laser power density and risk of sample damage
The same laser power focused into a micron-sized spot yields enormous power density — and can burn a sensitive sample before you manage to collect a spectrum. Calculate the power density [W/cm²] from the power and spot diameter (or from the objective and wavelength) and check which risk region you are in.
Beam on the sample
Don’t know the spot size? Provide the objective and laser — we will calculate it from the diffraction limit:
Formulas and assumptions
Spot (diffraction, Airy diameter): d ≈ 1.22 · λ / NA
Area: A = π · (d/2)²
Power density: PD = P / A
The model assumes a diffraction-limited spot and uniform power distribution over its area — a real Gaussian beam has higher peak intensity at the center, so treat the result as an averaged (lower) value. Damage thresholds are strongly material-dependent: a dark, absorbing, or organic material will be damaged at a density at which a hard mineral remains unaffected.
The risk regions below are rough guidelines, not safety standards. Always start with low power and increase it while observing the spectrum.
Have a sample you don’t want to guess about?
We conduct feasibility studies even on the most challenging samples — on your material, at your site. Leave your contact, and we will review your case and tell you directly whether Spectrally can measure it.
