Using variations in luminescence wavelength rather than luminescence intensity overcomes the problem of interference from variations in calcite porosity. See preliminary results in Baker et al. We use microscope imaging for analysis of most annual banding, as the 2-D image allows for data enhancement and filtering. We have stopped using laser technology, although useful for very compact calcite samples where one can get a perfect polish and negligible scattering of the laser light occurs, it is otherwise problematic. Scattering of the laser beam on the calcite surface means that for a majority of samples, the signal obtained is just a function of calcite porosity.
Lasers also have a fixed excitation wavelength.
So we now use luminescence spectrophotometers, which can be used to analyse the intensity of luminescence of water samples, and the wavelength variations of both water samples, and by using a fibre-optic extension, solid calcite. As the technique is non-destructive, we usually slice a sample in two along the axis of growth, and then polish one half. Thick-sections are also acceptable.