Passive cavity surface-emitting and edge-emitting lasers: physics, design, modeling

Abstract

We have proposed the concept of a passive cavity laser for both surface emitting and edge emitting devices. Passive cavity surface emitting laser has an active medium placed in or even outside of a distributed Bragg reflector, whereas the optical cavity remains passive and can be formed of an arbitrary, e. g. a dielectric material. This approach allows a significant reduction of the thickness of the epitaxially grown semiconductor structure (e.g., by a factor of 3) and also allows fabricating a surface emitting laser combined with a true photonic crystals, the latter being formed directly in the optical cavity allowing advanced possibilities for engineering of the lasing optical modes and providing their extreme lateral confinement. Passive cavity edge emitting laser employs a thick passive waveguide, e.g. a transparent substrate, while gain medium is placed in the evanescent part of the field in the cladding. If the gain medium is placed in another, thin cavity coupled to the substrate (Tilted Wave Laser) an ultranarrow vertical beam (down to 0.65 degrees full width at half maximum) is generated. Additional processing of a thin active waveguide by its cutting by the trenches enables to prohibit undesired emission with a broad angular distribution. Two-dimensional modeling of tilted wave lasers provides the optimum laser geometry with zero scattering losses and a high efficiency.