Phase-matched mid-infrared difference frequency generation in GaAs-based waveguides

We demonstrate difference frequency generation of 4 mm radiation from 1 to 1.32 mm pumps in GaAs-based waveguides. Phase matching is obtained by using form birefringence in selectively oxidized AlGaAs/AlAs multilayers. A tunability over 50 cm-1 around 4 mm is demonstrated by changing the waveguide temperature and one pump wavelength. A much larger tunability may be achieved by using two tunable sources