Martina Hentschel

Combining directional light output and ultralow loss in deformed microdisks.

A drawback of optical modes in microdisk cavities is their isotropic light emission. Here we report a novel, robust, and general mechanism that results in highly directional light emission from high-quality modes. This surprising finding is explained by a combination of wave phenomena (wave localization along unstable periodic ray trajectories) and chaotic ray dynamics in open systems (escape along unstable manifolds) and applies even to microlasers operating in the common multimode regime. We demonstrate our novel mechanism for the limaçon cavity and find directional emission with narrow angular divergence for a significant range of geometries and material parameters.

Unidirectional light emission from high-Q modes in optical microcavities

We introduce a new scheme to design optical microcavities supporting high-

Quantum Transport in Nonuniform Magnetic Fields: Aharonov-Bohm Ring as a Spin Switch

Q

Directional emission and universal far-field behavior from semiconductor lasers with limaçon-shaped microcavity

modes with unidirectional light emission. This is achieved by coupling a low-

Quantum chaos in optical systems: The annular billiard

Q

Orthogonality catastrophe and Kondo effect in graphene

mode with unidirectional emission to a high-

Chaos-assisted directional light emission from microcavity lasers.

Q

Husimi functions at dielectric interfaces: Inside-outside duality for optical systems and beyond

mode. The coupling is due to enhanced dynamical tunneling near an avoided resonance crossing. Numerical results for a microdisk with a suitably positioned air hole demonstrate the feasibility and the potential of this concept.

Asymmetric scattering and nonorthogonal mode patterns in optical microspirals

We study spin-dependent magnetoconductance in mesoscopic rings subject to an inhomogeneous in-plane magnetic field. We show that the polarization direction of transmitted spin-polarized electrons can be controlled via an additional magnetic flux such that spin flips are induced at half a flux quantum. This quantum interference effect is independent of the strength of the nonuniform field applied. We give an analytical explanation for one-dimensional rings and numerical results for corresponding ballistic microstructures.

Aharonov-Bohm physics with spin. II. Spin-flip effects in two-dimensional ballistic systems

We report experimental demonstration of directional light emission from limacon-shaped microcavity semiconductor lasers. Quantum cascade lasers (QCLs) emitting at λ≈10 μm are used as a model system. Both ray optics and wave simulations show that for deformations in the range 0.37<e<0.43, these microcavities support high quality-factor whispering gallerylike modes while having a directional far-field profile with a beam divergence θ∥≈30° in the plane of the cavity. The measured far-field profiles are in good agreement with simulations. While the measured spectra show a transition from whispering gallerylike modes to a more complex mode structure at higher pumping currents, the far field is insensitive to the pumping current demonstrating the predicted “universal far-field behavior” of this class of chaotic resonators. Due to their relatively high quality factor, our microcavity lasers display reduced threshold current densities compared to conventional ridge lasers with millimeter-long cavities. The perfor...