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Published October 29, 2007 | Published
Journal Article Open

Demonstration of air-guided quantum cascade lasers without top claddings

Abstract

We report on quantum cascade lasers employing waveguides based on a predominant air confinement mechanism in which the active region is located immediately at the device top surface. The lasers employ ridge-waveguide resonators with narrow lateral electrical contacts only, with a large, central top region not covered by metallization layers. Devices based on this principle have been reported in the past; however, they employed a thick, doped top-cladding layer in order to allow for uniform current injection. We find that the in-plane conductivity of the active region - when the material used is of high quality - provides adequate electrical injection. As a consequence, the devices demonstrated in this work are thinner, and most importantly they can simultaneously support air-guided and surface-plasmon waveguide modes. When the lateral contacts are narrow, the optical mode is mostly located below the air-semiconductor interface. The mode is predominantly air-guided and it leaks from the top surface into the surrounding environment, suggesting that these lasers could be employed for surface-sensing applications. These laser modes are found to operate up to room temperature under pulsed injection, with an emission spectrum centered around λ ≃ 7:66 μm.

Additional Information

© 2007 Optical Society of America. Received 10 July 2007; revised 21 August 2007; accepted 21 August 2007; published 26 October 2007. We thank C. Faugeras for help with the far-field measurements; F. Julien, C. Sirtori, O. Demichel for useful discussions, and J. Palomo for technical help. This work was conducted as part of a EURYI scheme award (www.esf.org/euryi). The Caltech portion of this work was supported by the DARPA Center for Optofluidics (http://www.optofluidics.caltech.edu). This work is supported by the UK Engineering and Physical Sciences Research Council (EPSRC) and by the Royal Society. The device fabrication has been performed at the nano-center "Centrale Technologique Minerve" at the Institut d'Electronique Fondamentale.

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August 22, 2023
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