arXiv subjects

Jakob Kreismann

Publications and source records attributed to Jakob Kreismann.

6 recordsLinked to original sources

arXiv2020

Spin-orbit interaction of light in three-dimensional microcavities

We investigate the spin-orbit coupling of light in three-dimensional cylindrical and tube-like whispering gallery mode resonators. We show that its origin is the transverse confinement of light in the resonator walls, even in the absence of inhomogeneities or anisotropies. The spin-orbit interaction results in elliptical far-field polarization (spin) states and causes spatial separation of polarization handedness in the far field. The ellipticity and spatial separation are enhanced for whispering gallery modes with higher excitation numbers along the resonator height. We analyze the asymmetry of the ellipticity and the tilt of the polarization orientation in the far field of cone-like microcavities. Furthermore, we find a direct relationship between the tilt of the polarization orientation in the far field and the local inclination of the resonator wall. Our findings are based on FDTD-simulations and are supported by three-dimensional diffraction theory.

physics.optics↗

arXiv2019

Super-directional light emission and emission reversal from micro cavity arrays

Optical microdisk cavities with certain asymmetric shapes are known to possess unidirectional far-field emission properties. Here, we investigate arrays of these dielectric microresonators with respect to their emission properties resulting from the coherent behaviour of the coupled constituents. This approach is inspired by electronic mesoscopic physics where the additional interference effects are known to enhance the properties of the individual system. As an example we study the linear arrangement of nominally identical Limaçon-shaped cavities and find mostly an increase of the portion of directional emitted light while its angular spread is largely diminished from 20 degrees for the single cavity to about 3 degrees for a linear array of 10 Limaçon resonators, in fair agreement with a simple array model. Moreover, by varying the inter-cavity distance we observe windows of reversion of the emission directionality and super-directionality that can be interesting for applications. We introduce a generalized array factor model that takes the coupling into account.

physics.optics↗

arXiv2018

The optical Möbius strip cavity: Tailoring geometric phases and far fields

The Möbius strip, a long sheet of paper whose ends are glued together after a $180^{\circ}$ twist, has remarkable geometric and topological properties. Here, we consider dielectric Möbius strips of finite width and investigate the interplay between geometric properties and resonant light propagation. We show how the polarization dynamics of the electromagnetic wave depends on the topological properties, and demonstrate how the geometric phase can be manipulated between $0$ and $π$ through the system geometry. The loss of the Möbius character in thick cavities and for small twist segment lengths allows one to manipulate the polarization dynamics and the far-field emission, and opens the venue for applications.

physics.optics↗

arXiv2016

The 3D Limaçon: Properties and Applications

We perform electromagnetic wave simulations of fully three-dimensional optical Limaçon-microcavities, one basis for their future applications in microlasers and photonic devices. The analysis of the three-dimensional modes and far-fields reveals an increase of the quality factors as compared to the two-dimensional case. The structure of the far-field in the third dimension shows pronounced maxima in the emission directionality inclined to the resonator plane which may be exploited for coupling the resonator modes to the environment. This triggers ideas for technical applications, like the suggested sensor that can detect small changes in the environment based on changes in the emission profile.

physics.optics↗

arXiv2016

Ray picture and ray-wave correspondence in triangular microlasers

We apply ray-optical methods to dielectric optical microcavities in the shape of triangles made of low refractive index material. We find ray trajectories that maximize the intensity inside the cavity to determine the far-field emission characteristics and to complement the concept of the unstable manifold applicable to chaotic microlasers. As these maximum intensity trajectories need not to be periodic, we suggest that they provide a more general explanation for emission patterns of microlasers than short periodic orbits. Further, the geometrical optics description is extended by the inclusion of intensity amplification along the optical path to achieve a better description of active, lasing cavities. Far-field emission patterns of equilateral triangle cavities obtained in this way agree well with our full electromagnetic wave simulations and with previously reported experimental results.

physics.optics↗

arXiv2014

Understanding deviations from ray optics at curved interfaces

Ray optics is a useful tool even in the regime where, actually, full wave-calculations would be appropriate. However, wave-inspired adjustments are needed to ensure the accuracy of ray-based predictions. These corrections are known as the Goos-Hänchen shift, a lateral shift along the interface, and the Fresnel filtering effect, an angular shift, that violates Snell's law and the principle of ray-path reversibility. Whereas they are well established at planar interfaces, an accurate description of microlasers and other microoptics devices requires their precise knowledge at the curved boundaries characteristic for these devices. Here, we present analytical and numerical results that highlight the role of boundary curvature and show the clear deviations from the planar case. We introduce an intuitive picture that allows for a straightforward understanding why Fresnel filtering grows considerably with curvature whereas the Goos-Hänchen shift becomes less important.

physics.optics↗