Fingerprints as Forked Diffraction Gratings
Laser light can behave much like water in a stream in that it experiences turbulence caused by objects that block its path. While vortices in water and vortices in light both involve a fluid rotation around an axis, optical vortices propagate through space rather than through time (you will see another full rotation as you look further along the length of the laser beam rather than simply watching for longer) and optical vortices in experimentation are generated by diffraction gratings as well as blockages (like the rocks in a stream). Forked diffraction gratings harness the diffractive property of light by forcing it through many sequential slits, each about the width of the wavelength of light being used. A fork in those lines is simply a bend or an end where there is inconsistency in the pattern of the lines designed specifically for the type of vortex one wishes to produce. When looking at our own fingers, it is easy to see that the complex and unique lines on a thumb exhibit many of these same properties: they have parallel lines and forks. I wished to find evidence that these properties are enough to generate optical vortices of their own when projected as a hologram along the propagation of a laser beam. However, concurrent research suggested that the evidence I found of vortices may have been the result of blockages instead of the properties of a fingerprint. Upon further investigation, I found that my methods applied to random shapes had similar results. While my prediction for the reason behind vortex generation was incorrect, the applications remain the same: someday we may be able to improve the methods of biometrics using light diffraction.