title: 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 l (1/4) 7:66 mum.
authors: V
authors: V
authors: Moreau
authors: M
authors: M
authors: Bahriz
authors: R
authors: R
authors: Colombelli
authors: R
authors: R
authors: Perahia
authors: O
authors: O
authors: Painter
authors: L R
authors: LR
authors: Wilson
authors: A B
authors: AB
authors: Krysa