Abstract: A method for measuring a physical property of a polymer sample includes measuring a portion of a Raman spectrum of the polymer sample, determining a value of a preselected spectral feature from the portion of the Raman spectrum, and comparing the determined value to reference values. The value of the preselected spectral feature depends functionally on the physical property. The reference values relate the preselected spectral feature to the physical property. A probe includes a housing; first, second, and third optical systems attached to the housing; and a first optical filter located along a first direction. The first optical system is to collimate an illumination beam along the first direction. The first optical filter is to produce substantially monochromatic light and is insertable into the probe without substantially affecting an alignment between the probe and the sample.