Understanding the photon-photon resonance of DBR lasers using mode expansion method

A theoretical model based on the mode expansion of the traveling wave equations is developed to investigate the mode interaction processes behind the photon-photon resonance (PPR) effect in distributed Bragg reflector (DBR) lasers. With dual-mode rate equations, strength of mode interactions is characterized by the cross power and the coupling factors, which arise from the non-orthogonality of the main mode and the PPR mode. Small signal analysis and large-signal dynamics are performed, and results indicate that the cross power is a key contributor to the PPR effect.

Interior of the horizon of the Bañados-Teitelboim-Zanelli black hole

A quantum scalar field inside the horizon of the non-rotating BTZ black hole is studied. Not only the near-horizon modes but also the normal modes deep inside the horizon are obtained. It is shown that the matching condition for the normal modes of a scalar field at the horizon does not uniquely determine the normal-mode expansion of a scalar field inside the horizon. By choosing a certain appropriate prescription for removing this ambiguity, an integral form of a new scalar propagator for points on both sides of the horizon are obtained. A similar problem may arise in higher-dimensional black holes.