Wave pattern and weak localization of chaotic versus scarred modes in stadium-shaped surface-emitting lasers

Characterizing classical periodic orbits from quantum Green's functions in two-dimensional integrable systems: Harmonic oscillators and quantum billiards

A general method is developed to characterize the family of classical periodic orbits from the quantum Green's function for the two-dimensional (2D) integrable systems. A decomposing formula related to the beta function is derived to link the quantum Green's function with the individual classical periodic orbits. The practicality of the developed formula is demonstrated by numerically analyzing the 2D commensurate harmonic oscillators and integrable quantum billiards. Numerical analyses reveal that the emergence of the classical features in quantum Green's functions principally comes from the superposition of the degenerate states for 2D harmonic oscillators. On the other hand, the damping factor in quantum Green's functions plays a critical role to display the classical features in mesoscopic regime for integrable quantum billiards, where the physical function of the damping factor is to lead to the coherent superposition of the nearly degenerate eigenstates.

Exploring the influence of boundary shapes on emission angular distributions and polarization states of broad-area vertical-cavity surface-emitting lasers

We design the stadium-shaped and rectangular vertical-cavity surface-emitting lasers (VCSELs) to investigate the influence of boundary shapes on the emission angular distributions and polarization states. For the stadium-shaped VCSELs, the emission angular distribution prefers to be almost omnidirectional because the lasing mode with purely scarred structure is seldom to be excited. On the contrary, the rectangular VCSELs usually generate dominant lasing modes with the morphology of quasi-periodic linear ridges, which can make emission angular distribution to be concentrated on the certain direction. From the polarization-resolved light-current curves, the stadium-shaped VCSEL is quite prone to exhibit numerous abrupt changes (kinks) associated with polarization switching with increasing current, whereas for rectangular VCSEL there is no conspicuous kink to be seen during a wide range of current changing from near to far above lasing threshold.

Experimental phase-space-based optical amplification of scar modes

Wave billiards which are chaotic in the geometrical limit are known to support nongeneric spatially localized modes called scar modes. The interaction of the scar modes with gain has been recently investigated in optics in microcavity lasers and vertical-cavity surface-emitting lasers. Exploiting the localization properties of scar modes in their wave-analogous phase-space representation, we report experimental results of scar mode selection by gain in a doped D-shaped optical fiber.