Mode tuning of quantum cascade lasers through optical processing of chalcogenide glass claddings

In this letter, we demonstrate a method of tuning quantum cascade (QC) lasers by modifying the optical properties of an overlying cladding material. An amorphous chalcogenide cladding layer is deposited through a low temperature, solvent-casting technique that is compatible with current QC laser fabrication and operation. Above band gap illumination (lambda < 530 nm) of this cladding causes a permanent change in its index of refraction leading to a change of the modal refractive index and a corresponding modal shift in the laser. Combined with deep-etched distributed Bragg gratings, a tuning of over 30 nm is obtained at an operating wavelength of 7.9 mu m for constant current and temperature.