The first results of a theoretical and experimental study are presented showing that a significant enhancement of the efficiency of gratings used as wavelength selectors for cw tunable lasers may be achieved with adequate dielectric coatings. It is found that, in some cases, the energy absorbed by the grating surface can be reduced by a factor >2. The output power of a cw Rh640 dye laser was practically multiplied by the same factor. It seems that holographic gratings are more adaptable than are ruled gratings to this utilization.

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The Raman spectrum of a microsubstance, smeared on a fiber coming from the Shroud of Turin, was compared with numerous spectra published for old or modern pigment dyes, whole bloods, dried bloods, red blood cells, albumin, very ancient blood stains, and various "degradation" products of heme. Within the wavenumber measure accuracy, it is shown that all Raman lines detected above background could correspond to vibration frequencies found in biliverdin-derived compounds except a weak line that we tentatively attributed to amide I. Biliverdin is known as an oxidative ring cleavage product of the heme of blood. Energy dispersive spectroscopy (EDS) analysis of the sample confirms an elemental composition fully compatible with this hypothesis. Therefore, it is very likely that this microsubstance contains products of heme including heme/biliverdin-derived compounds and protein traces (amide I). Nevertheless, other measures will be necessary to confirm it. This method of identification, adding EDS to Raman spectrometry can be applied to nondestructive testing (NDT) of many other microsamples.