Abstract
Many optical approaches have been used to examine the composition and structure of gemstones, both recently and throughout history. The nonlinear optical behavior of different gemstones has not been investigated, and the higher order terms to the refractive index represent an unused tool for qualifying and examining a stone. We have used a multiphoton microscope to examine the nonlinear optical properties of 36 different gemstones and demonstrate that it is a useful tool for imaging them three-dimensionally up to the millimeter scale below the sample surface. The polarization dependence of second harmonic generation signals was used to examine the crystal orientations inside the minerals.
Highlights
The science of examining and qualifying gemstones has used optics for centuries
We demonstrate the utility of the multiphoton microscope (MPM) in the study of gems and minerals
The microscope was configured to image with Second Harmonic Generation (SHG) and Third harmonic Generation (THG)
Summary
The science of examining and qualifying gemstones has used optics for centuries. In a lecture delivered at the Imperial Institute of Great Britain in 1895, Sir Henry Meirs, a mineralogist, discussed the clear advantages of the use of optics for the analysis of gemstones compared to existing traditional methods [1]. Non-contact and nondestructive measuring methods are vital with such valuable samples. Sir Meirs argued for using conventional and polarized light microscopy, and measuring refractive index and absorption as more accurate, less destructive methods. Modern versions of many of his proposed methods are still commonly used by geologists today as ready tools for qualifying and identifying stones [2, 3]
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