Results with calcite (whose rhomboid crystals have parallel
plate geometry) are challenging. For certain directions the
emerging E (extraordinary) and O (ordinary) beams are parallel
to each other, as textbooks say. For others they are not. These
observations, made on several crystals whose sizes are of the
order of an inch, is tentative. With a student, and a colleague,
I plan to continue working on the phenomenon. An Internet
partner with access to a goniometer would be welcome.
Suppose the preliminary findings are confirmed. Is there a
trivial way of explaining them? My hypothesis (conflicting
with everything I read) is that energy does "propagate" (no
flame intended) along the normals to Huygens wavelets, even
when the wavelets are ellipsoids of revolution. In other words,
the E beam is bending inside the crystal and the Pointing
vector is always perpendicular to expanding wave surfaces.
Any comments?
Gary Karshner wrote:
Fowles' "Introduction to Modern Optics," I find especially
clear on you problem of double refraction. Born and Wolf
also does a good job on the subject.