Grating coupling and intersubband absorption at 10mym in GaAs/AlXGa1-XAs infrared quantum well waveguides.

Grating coupling and intersubband absorption of accordingly 10-Mym COsub2 laser radiation are demonstrated in GaAs/AlsubxGasub1minusxAs mid- infrared single-mode waveguides grown by molecular beam epitaxy. The samples contain ten Si-doped GaAs quantum wells embedded within the waveguide core. Grating coupling in mesa waveguides fabricated from such samples is studied as a function of the wavelength and polarization of the incident laser light. The devices demonstrate selective absorption of TM polarized light, as dictated by intersubband absorption selection rules. The measured wavelength dependence of the optimal coupling angle is in good agreement with a simple grating-coupler analysis. Potential applications for infrared detection and integrated optics are discussed.