Room-temperature continuous-wave metal grating distributed feedback quantum cascade lasers

Abstract

We report on the design and elaboration of continuous wave (cw) distributed feedback quantum cascade lasers (QCLs) using a simple metal grating approach without epitaxial regrowth, neither for the grating nor for the thermal extraction. Room temperature cw single monomode QCLs with 30 dB side mode suppression ratio are demonstrated down to 4.5 μm with 20 mW output power and threshold of 1.5 kA cm−2. The beam quality factor (M2) does not exceed 1.22 for both axes. These results are discussed and the key issue of thermal management of the device is emphasized.

Stable single mode operation of quantum cascade lasers by complex-coupled second-order distributed feedback grating

“…Another spectral measurement to deduce thermal resistance is illustrated in Ref. [18]. The difference in wavelength comes from the thermal resistance of the device Dv ¼ ðv=nÞðdn=dTÞDT, where Dm is the frequency difference, DT is the temperature difference and n is the optical index.…”

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

“…Une nouvelle approche basée sur l'utilisation de réseaux métalliques de surface a été développée. Cette nouvelle approche repose sur une modulation de l'indice générée par le couplage entre les modes guidés dans la zone active et un mode confiné à l'interface, entre le métal et le guide supérieur (figures 4 et 5) [6]. Précisons que ce couplage est possible car les modes contra-propagatifs d'une part, et le mode de surface d'autre part, ont la même polarisation TM.…”

“…Un avantage supplé-mentaire de cette approche est sa robustesse vis-à-vis des variations technologiques, ce qui permet de contrôler la longueur d'onde d'émission à plus ou moins 1 cm -1 . Des QCL DFB fonctionnant en mode pulsé ou continu sont maintenant disponibles commercialement (fi gure 6, voir aussi les fiches techniques sur www.3-5lab.fr) sur la totalité de la plage allant de 4 à 10 μm [6]. Les lasers fonctionnent à température ambiante sur un module thermoélectrique à effet Peltier.…”

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

“…In order to reduce the losses introduced by the metal, and thus increase the operating temperature, the proposed configuration is based on the analysis reported in a previous paper, enabling the engineering of low loss-index coupled DFB with metal gratings [2][3]. The DFB cavity has typical dimensions (about 2mm x30µm) whereas the coupler section is larger to ensure a reduction of the divergence but should be shorter to avoid losses Fig.…”

“…For such type of application, single-mode lasers with narrow line-width are necessary and therefore distributed feedback (DFB) QCLs have been recently developed [1][2][3][4]. In standard approach, light is emitted by a cleaved facet.…”