Studying Archaeological Samples Using Archaeophotonics

Three spectroscopic techniques—Raman spectroscopy, laser-induced breakdown spectroscopy (LIBS), and laser-induced fluorescence (LIF)—are poised to transform the archaeology industry for decades to come, according to a review article published in Applied Spectroscopy Review (1). This review article highlights how the three abovementioned spectroscopic techniques have helped propel the field of archaeophotonics forward, which is changing the way archaeologists study ancient artifacts.

Archaeophotonics is a mash-up between archaeometry and photonics. Archaeometry is the study of archaeological artifacts by using chemical and physical procedures (2). Photonics allows for the study of the chemical composition of objects (2). Photonics is applied in archaeometry primarily through spectroscopic techniques like Raman spectroscopy, laser-induced fluorescence (LIF), and laser-induced breakdown spectroscopy (LIBS), enabling rapid, on-site chemical analysis of various objects (2). Additionally, photonics is increasingly used for imaging in archaeology, such as laser scan surveys that reveal surface irregularities and significant features invisible to the naked eye, particularly when surface contact is undesirable (2).

Archaeologists in the process of excavations in a closed area. Generated with AI. | Image Credit: © Nicolas Swimmer - stock.adobe.com

In this review article, which was organized by researchers from the Manipal Academy of Higher Education in Manipal, the scientists explorethe cutting-edge field of archaeophotonics and explained how light-based analytical techniques are benefitting archaeological studies. Their review article focuses on Raman, LIBS, and LIF.

For LIBS, this technique offers elemental analysis of samples (1). By focusing a high-powered laser on a tiny area of the artifact, LIBS generates a plasma, and the light emitted from this plasma is analyzed to determine the elemental composition (1). This method is particularly valuable for studying the metallic composition of ancient coins or the elemental makeup of meteorites (1). A benefit of using LIBS in archaeological analysis is that it is precise and nondestructive. Considering that archaeological studies require careful handling of artifacts and samples, it is important that the analytical techniques use do not ruin the sample. LIBS helps in this regard.

Meanwhile, to learn more about the structural information of archaeological samples, Raman spectroscopy comes in handy. This technique excels in identifying pigments, ceramics, and biofacts, revealing the molecular composition and, consequently, the technological processes used by ancient civilizations (1). The ability of Raman spectroscopy to detect even minor differences in molecular structures offers a detailed view of the artifacts’ provenance and the materials used in their creation (1).

And finally, the authors discussed the third technique, LIF, and its impact on archaeological studies. By exciting molecules within the sample with a laser, LIF detects the emitted fluorescence, which can be used to identify various substances (1). This technique is particularly useful in studying organic materials and pigments, providing insights into the degradation processes and preservation states of archaeological finds (1).

The authors noted in their study that these three spectroscopic techniques used in archaeophotonics complement each other well (1). An example cited in the paper is that when combined with the molecular information from Raman spectroscopy and the fluorescence data from LIF, the elemental data obtained from LIBS can provide a comprehensive picture of the artifact’s composition and history (1).

The significance of multimodal spectroscopic techniques in archaeophotonics is poised to help the field grow and evolve. The review suggests that future studies may focus on developing portable and more cost-effective versions of these spectroscopic tools, making them more accessible for fieldwork and in-situ analyses (1). This will be beneficial for archaeologists, who often do their excavation work in remote locations.

By combining LIBS, Raman spectroscopy, and LIF, researchers are now better equipped to delve into the past, uncovering the secrets held within ancient artifacts (1). This approach not only enriches our understanding of history, but it also paves the way for new discoveries in the realm of archaeology.

References

(1) Harikrishnan, S.; George, S. D.; Chidangil, S.; et al. Archaeophotonics: Applications of Laser Spectroscopic Techniques for the Analysis of Archaeological Samples. Appl. Spectrosc. Rev. 2024, 59 (2), 187–223. DOI: 10.1080/05704928.2023.2189946

(2) Artigas, D.; Cormack, I. G.; Loza-Alvarez, P. Archaeophotonics: Lasers Unveil the Past. Optics & Photonics 2007, 18 (7), 22–25. https://www.optica-opn.org/home/articles/volume_18/issue_7/features/archaeophotonics_lasers_unveil_the_past/