Substrate emitting index coupled quantum cascade lasers using biperiodic top metal grating

Abstract

We report on the design and experimental demonstration of a specific metal grating profile that enables a substrate emission of a quantum cascade laser. A low loss, index coupled, and horizontal cavity surface emitting laser (HCSEL) design is proposed, which is very robust against technological spreads. The detailed analysis of the metallic top grating is performed, enabling the laser still to operate as a distributed feedback laser while emitting from the substrate. Following this concept, HCSEL with InP cladding layers and InGaAs/AlInAs active regions have been fabricated. Room temperature HCSEL emitting at 5.65 μm with a low beam divergence is demonstrated.

Les lasers à cascade quantique : l’accès au moyen infrarouge

“…En utilisant la base du guide d'onde plutôt que la facette on augmente les dimensions de la surface émettrice et on réduit ainsi la divergence. L'émission par le substrat est obtenue en utilisant des réseaux métalliques de surface du second ordre ou une combinaison astucieuse d'un réseau du premier ordre avec un réseau du second ordre [7]. La lumière dans la cavité est alors couplée vers les modes radiatifs perpendiculaires au substrat.…”

Room-temperature edge and surface-emitting distributed-feedback quantum cascade lasers without top cladding layers

“…Different approaches have been developed to control the beam divergence, where a grating is usually needed. Plasmonic collimators have been implemented in edge emitting lasers [1], 2D photonic crystals for surface emitting laser [2], and 2 nd order DFB lasers with substrate emission [3]. We report distributed-feedback surface-plasmon quantum cascade lasers operating in the mid-infrared.…”

Directional single mode QCL emission using metal grating second order coupler at room temperature

“…For this reason, lenses are required for applications such as gas sensing. The demonstration of substrate emission at room temperature with improved divergence has already been achieved in the case of a ridge waveguide configuration with a bi-periodic grating [5]. In such structure, the size of the waveguide in the direction perpendicular to the grating could not be higher than in the case of a classical QCL cavity (about 10µm in the mid-IR) in order to suppress higher order transverse modes.…”