Polarized light, circular light, and also scarabs, have sometimes being mentioned and debated in Alchemy. Dennis H. Goldstein, Optics and Photonics researcher, investigated further on A. A. Michelson observating, in 1911, that scarabs could send back annular polarized light from a falling unpolarized beam.
“Beetles of the scarab family have been found to reflect circularly polarized light from incident unpolarized light. There are many known animals that use polarized light in some form and several that actually create it, but there are few examples of the creation of circularly polarized light in nature”. This is the abstract from Dennis H. Goldstein conference paper presented at the 50th annual meeting of SPIE, Optics and Photonics, San Diego, California, 1-4 August 2005.
Alchemists haven’t the slightest idea about what happening inside their vessels. They are only aware of Secret Fire and hardly know how to extract it. Scarce knowledge has always been alchemist’s companion. In fact I chose to name “Alchemy & Nature” this new category on the natural occurring events that might be involved in our researches, and I did not dare to take “Alchemy and Science”.
Dennis H. Goldstein: REFLECTION PROPERTIES OF SCARABAEIDAE
“The creation of polarized light is common in nature, but the generation of circularly polarized light from unpolarized light is quite rare. A. A. Michelson noted in 1911 that reflected light from the scarab beetle Plusiotis resplendens, a beetle that appears 2-9 to have been fashioned out of brass or gold, is circularly polarized. Later authors have discussed this effect as well and it has been found that only scarabs possess the ability to generate circularly polarized light. Fig. 1a shows Plusiotis resplendens in the absence of polarizing optics, and Fig. 1b shows the animal with a circular polarizer in front of the camera. The effect for this creature is more subtle than other scarabs; it is difficult to discern the difference between these two images. A more impressive example is Plusiotis gloriosa, shown in Fig. 2. I have examined several of these scarabs for this study and have measured the spectral reflectance and Mueller matrix for the visible region in order to quantify this effect. “
“I have presented reflectance spectra and Mueller matrices for two scarab beetles. This is the first explicit instance of this data in the literature known to me. Michelson (1911) describes the fact that the hand of the circular polarization reverses from the blue 25 end of the spectrum to the red, and Gaubert (1924)agrees with this. In a much later paper (1969), Neville and Caveney disagree with this. The current results validate the results of Michelson and Gaubert with regard to this hand reversal, and in fact, it appears that there are two reversals in the visible wavelength region”.
All Polarimetric and Reflectometric Parameters with Diagrams and References were available, together with the whole document, at http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=ADA437788 , but the link seems to be expired now;
Pete Vukusic provided a later improvement on the subject published by AAAS in SCIENCE, VOL 325, 24 JULY 2009.
Pete Vukusic: EVOLUTIONARY PHOTONICS WITH A TWIST.
“The iridescent appearance of the hard forewings of scarab beetles can be caused by complex helical nanostructures.
Left handed circularly polarized reflection means that from the perspective of the observer, the electric field vector of the light reflected from the scarab beetle describes a left handed corkscrew, or helix, along its direction of propagation. Circularly polarized reflection from specific beetles was first observed nearly a century ago. Plusiotis gloriosa’s tendency to do this is thus not an isolated example, but the attribute is nonetheless rare. It requires a distinct azimuthally twisted, or helical, character in the nanostructure that forms the first few micrometers of its elytra. In these scarab beetles, the spatial pitch of this helix creates the intrinsic periodicity that, to human vision, produces bright iridescent color. An example of this is shown in Plusiotis alphabarrerai . What appears to human eyes as green iridescence from certain scarab beetles, such as shown here, mostly constitutes circularly polarized color…..
……Synthetic systems that exhibit strongly circularly polarized color reflections include certain layered mesophases, specifically those associated with cholesteric liquid crystals (also known as chiral nematic liquid crystals).
Their circularly polarized optical properties arise because their constituent molecules lack inversion symmetry. This produces intermolecular forces that favor a specific small azimuthal twist through the whole system…..
….In Plusiotis gloriosa (image 2) and several other Rutelinae, however, the structural complexity goes beyond mere helically ordered layering. The elytral surfaces of these beetles consist of arrangements of mostly hexagonal micrometer scale multicolored cells….
….The beetle helical ultrastructure is arguably too complex and too costly to produce without the benefit of a suitable optical selection advantage, such as effective signaling. The strong circularly polarized reflection observed in the beetles may, for example, play a role in intraspecific communication. This is especially the case for another scarab, Plusiotis resplendens (image 1). It exhibits strong broad band reflection of both left and right handed circularly polarized light due to the presence of two chirped helical layered regions separated by a half wave plate….
….Despite some initial behavioral studies, it remains unknown whether the circularly polarized reflection from these special beetles provides a channel of communication. However, Chiou et al. recently showed that such communication is possible for a marine crustacean: the stomatopod Odontodactylus sp. Not only does this species signal brightly using circularly polarized colored light reflected from two posterior abdominal appendages, but it also responds behaviorally to circularly polarized stimuli. Its method for doing so is elegant. Chiou et al. revealed that incident circularly polarized light is converted to linearly polarized light when it is transmitted through a quarter wave plate in specific cells of the eyes’ mid band region.”
In 2009 a research by Mohan Srinivasarao focused the material source of the circular polarize light in the scarab shell.
TITLE: A structure much like a liquid crystal allows the shell of a scarab beetle to circularly polarize light.
Mohan Srinivasarao of the Georgia Institute of Technology and colleagues have used microscopy techniques to show that the iridescent green scarab beetle (Plusiotis gloriosa), has a shell that contains a helical structure, rather like a “cholesteric” liquid crystal.
“This study is important because it highlights how animals produce very complex nanostructures by self-assembly, the resulting structures are optically active and produce brilliant metallic green structures, and the optical activity results in reflected light being circularly polarized.
There are many examples of insect shells, fish scales, bird feathers and other objects in the animal kingdom that have unusual optical properties. Sometimes researchers find the properties surpass those in manmade materials, in which case they can try to copy the animal’s design. In 2007, researchers discovered that a tropical beetle’s oddly bright white shell was the result of an “aperiodic” shell structure, and said it could lead to a new type of super-white, synthetic material.
Using reflected-light microscopy, Srinivasarao’s group could see how the shell of Plusiotis gloriosa changes colour at different angles, producing the iridescent colours visible to the human eye. However, using laser-scanning confocal microscopy for higher magnifications, the group could discern a helical structure. This structure resembled a cholesteric liquid crystal, which circularly polarizes light as a result of defects that twist its ordered layers of molecules with respect to one another.
Srinivasarao thinks the scarab beetle’s shell could, like other animals, be mimicked for manmade applications. One could envision making very shiny metallic colours by taking a cholesteric fluid and varying the conditions at which the surface defects appear”.
Article taken from physicsworld.com.