Complex coupled 1.55 /spl mu/m DFB-lasers based on focused ion beam enhanced wet chemical etching and quantum well intermixing

A simplified method for the fabrication of complex coupled gratings for distributed feedback lasers was developed for 1.55 /spl mu/m wavelength applications. By using ion beam implantation enhanced wet chemical etching in combination with quantum well intermixing a refractive index grating can be selfaligned with an absorption grating. The gratings are defined after a conventional ridge waveguide process lateral to the ridge by maskless focused ion beam implantation. Therefore no overgrowth step is necessary. As cleaved laser devices show side mode suppression ratios of more than 40 dB and stable single mode emission up to operation temperatures of 90/spl deg/C.