Locally conserved quantities of the electromagnetic field in lossless chiral media are derived from Noether's theorem, including helicity, chirality, momentum, and angular momentum, as well as the separate spin and orbital components of this last quantity. We discuss sources and sinks of each in the presence of current densities within the material, and in some cases, as also generated by inhomogeneity of the medium. A previously obtained result connecting sources of helicity and energy within chiral materials is explored, revealing that association between the two quantities is not restricted to chiral media alone. Rather, it is analogous to the connection between the momentum, and the spin and orbital components of the total angular momentum. The analysis reveals a new quantity, appearing as the "orbital" counterpart of the helicity density in classical electromagnetism.
The electric and magnetic fields of a plane electromagnetic wave are orthogonal to each other and the direction of propagation. This suggests that the maximum number of waves with the same frequency that can be superposed without any interference is three. This can be done by choosing three waves travelling in mutually orthogonal directions and choosing all three polarisations orthogonal to each other.
If one is content with only the mean square of the electric field being homogeneous without requiring that the mean square of the magnetic field also be homogeneous, larger superpositions are allowed. For many practical purposes, such superpositions can still be considered noninterfering, as it is the electric field that interacts most with matter, including fluorescent dyes, CCDs and the light-sensitive pigments in the human eye. The inhomogeneity in the magnetic field is relatively difficult to detect.
The helicity density, a quantity that indicates the handedness of the light, is in general inhomogeneous for our noninterfering superpositions. It will vary in space in a pattern that is quite often, although not necessarily, periodic and resembles the intensity variations in optical lattices. There is enough freedom left in our superpositions to allow for a large variety of helicity
We present details on how the newly introduced technique of chiral rotational spectroscopy can be used to extract orientated information from otherwise freely rotating molecules in the gas phase. In this technique circularly polarized light is used to illuminate chiral molecules and shift their rotational levels to yield orientated chiroptical information via their rotational spectrum. This enables in particular the determination of the individual, physically relevant components of the orientated optical activity pseudotensor. Using the explicit example of (S)-propylene glycol we show how measuring the rotational spectrum of molecules in the microwave domain allows for the recording of a small set of rotational transitions from which the individual polarizability components can be determined.
We investigate the evanescent field at the surface of laser written waveguides. The waveguides are written by a direct femtosecond laser writing process into fused silica, which is then sanded down to expose the guiding layer. These waveguides support eigenmodes which have an evanescent field reaching into the vacuum above the waveguide. We study the governing wave equations and present solution for the fundamental eigenmodes of the modified waveguides.
The similarities and differences of spatial shifts to the centroids of reflected beams, and their (optical vortex) structure are discussed and reviewed. The differences between vortex-induced shifts to a beam centroid on reflection, and to the distribution of the vortices themselves is discussed. We conclude by discussing the shifts of a reflected beam containing a single anisotropic vortex.
Weak measurements typically require two non-orthogonal states, which are not eigenstates of an observable. This is why weak values of the orbital angular momentum operator seem counterintuitive or involve additional auxiliary observables, such as polarization. We show how the use of states emerging from spiral phase plates or holograms with fractional step height can be used to construct weak values of the orbital angular momentum operator.
On scattering, the high strength singularity of a vortex beam breaks into a configuration of single charge vortices. The precise geometry of such a vortex constellation depends on the angle of incidence and the material properties of the scatterer, but also on the optical spin-orbit coupling as choosing different input and output polarization results in a family of vortex constellation. Measuring the position of the individual vortices allows us to reconstruct elements in an systematic expansion of the scattering matrix, in an analogy to optical aberration theory. We discuss in detail the dependence of the constellation geometry on external parameters, which is the basis for an optical metrology based on vortices.
In optics, the Goos-Hänchen shift is a transverse displacement of a reflected light beam along a material interface.
It is usually associated with the presence of evanescent waves beyond the interface. We describe an analogous
displacement effect for scalar waves at a boundary satisfying Robin, or mixed, boundary conditions, although
the wave does not penetrate the boundary. We briefly discuss how the reflection of electromagnetic plane waves
differs from reflection due to Robin boundary conditions.
Optical vortices are points of zero intensity in a two dimensional, classical optical field. As first discussed by Berry
and Dennis [Berry, M. V. and Dennis, M. R., "Quantum cores of optical phase singularities" Journal of Optics
A 6, S178-S180 (2004)] these singularities are replaced by 'quantum cores' in a deeper level of description. In a
fully quantized theory of optical fields an excited atom trapped at the singularity can emit light spontaneously
and hence soften the perfect zero of an optical vortex. More recently Barnett [Barnett, S. M., "On the quantum
cores of a optical vortex," Journal of Modern Optics 55, 2279-2292 (2008)] presented a more realistic analysis of
quantum cores which accounts for the effect of the trapping potential on the transition dynamics inside a vortex
core. Here, we revisit the scenario of emission near an optical vortex in the realistic setting of Barnett.
In the 1970s, Jones demonstrated a photon drag by showing that the translation of a window caused a slight displacement
of a transmitted light beam. Similarly he showed that a spinning medium slightly rotated the polarization state. Rather
than translating the medium, the speed of which is limited by mechanical considerations, we translate the image and
measure its lateral delay with respect to a similar image that has not passed through the window. The equivalence, or
lack of it, of the two frames is subtle and great care needs to be taken in determining whether or not similar results are to