On-demand polarization by a vertical-cavity surface-emitting laser with two tilted sub-wavelength gratings.

We show that each polarization state on the Poincaré sphere (PS) can be accessed on-demand (Poincaré sphere tailoring) by a semiconductor-based vertical-cavity surface-emitting laser (VCSEL) with two tilted sub-wavelength gratings (SWGs). We develop a vectorial Barkhausen criterion that answers the question: what conditions must the cavity fulfill to support a given desired polarization state? Addressing this inquiry leads to a completely different strategy based on the entangled interplay between two tilted SWGs, resulting in an overall chiral cavity, whose features depend on the gratings and their mutual rotation. This leads to the emission of a well-controllable polarization state based on standard technologies used in polarization-stable VCSELs, which paves the way for inspiring several new potential applications.

Spatially resolved Stokes parameters of small-area vertical-cavity surface-emitting lasers: experiment and simulation.

We present experimental investigations on spatially resolved Stokes parameters of vertical-cavity surface-emitting lasers (VCSELs) with a small aperture diameter of 3 µm and a monolithically integrated surface grating on top of the structure to technologically control the polarization. As expected, the grating fixes the state of polarization, but still shows both a spatially nonuniform linear polarization distribution of the fundamental transverse mode as well as an interesting eight-lobe pattern of circular polarization in terms of change of sign. These experimental findings are reproduced by numerical simulations using a fully vectorial three-dimensional model.

Transverse-mode-selectable microlens vertical-cavity surface-emitting laser.

A new vertical-cavity surface-emitting laser structure employing a thin microlens is suggested and numerically investigated. The laser can be made to emit in either a high-power Gaussian-shaped single-fundamental mode or a high-power doughnut-shaped higher-order mode. The physical origin of the mode selection properties of the new structure is rigorously analyzed and compared to other structures reported in the literature. The possibility of engineering the emission shape while retaining strong single mode operation is highly desirable for low-cost mid-range optical interconnects applications as well as the compact optical trapping of high-refractive-index dielectric particles and low-refractive-index, absorbing, or metallic particles.

Wave chaos in real-world vertical-cavity surface-emitting lasers.

We report the onset of wave chaos in a real-world vertical-cavity surface-emitting laser. In a joint experimental and modeling approach we demonstrate that a small deformation in one layer of the complicated laser structure changes the emission properties qualitatively. Based on the analysis of the spatial emission profiles and spectral eigenvalue spacing distributions, we attribute these changes to the transition from regular behavior to wave chaos, and justify the full analogy to two-dimensional billiards by model calculations. Hence, these lasers represent fascinating devices for wave chaos studies.