Gain/loss characterisation of optical waveguide and semiconductor laser structures

Finite element analysis, employing the H-field vector and scalar formulations, has been used with the aid of perturbation techniques to determine the modal gain and loss characteristics of optical waveguides and semiconductor laser structures. The accuracy and the applicability limits of the perturbation method are examined, and compared to the more accurate but more computer intensive transverse magnetic field formulation for an embedded-channel waveguide. Further, the method is applied to a rib-waveguide laser structure, where the imaginary part of the refractive index of the InGaAsP active layer is seen to vary according to the carrier concentration profile. Finally, the accuracy of a widely used but simpler method for determining the modal gain for QW and MQW laser structures, in terms of the optical mode confinement, is determined.