Optothermal Raman infers conductivity from three measured ingredients: absorbed laser power, the temperature read from a Raman peak shift, and geometry. Each carries uncertainty, and the conversion amplifies them — historically dominated by absorbed power, since the absorbance of a suspended atomic layer is itself hard to measure, with temperature-rise determination second. The thermometry dial here is the COMBINED relative uncertainty of the measured temperature rise — coefficient calibration, peak-position estimation and heating-model contributions already folded in. Dial both and watch the conductivity error bar they justify.
Model: first-order propagation u(k)/k = √(u(P)²+u(ΔT)²) for k ∝ P/ΔT, where u(ΔT) is the combined relative uncertainty of the temperature rise (coefficient calibration, peak-position readout and heating-model terms combined in quadrature upstream) — a SIMPLIFIED teaching form; full budgets add geometry, contact, model-form and covariances per the GUM. Schematic teaching tool, not an instrument.