Optical waveguiding in (In, Ga)(As, P) inverted rib waveguide lasers at 1.3 µm wavelength

A theory is presented for waveguiding in inverted rib waveguide (IRW) lasers. For the first time, theory has been compared with experiment for these structures in (In, Ga)(As, P). Consideration is given to dielectric constant models in the quaternary system. After including the large negative effect of carriers on the dielectric constant, the modified single effective oscillator model is found to be suitable. By applying the dielectric constant values so obtained to the waveguide theory, IRW design curves are produced. Measurements of lateral far-field widths and spectral separations of zero and first order modes are used to test the validity of the predictions. The agreement is very good. The guide strengths are in the range
\Delta \epsilon_{G} = 3-11 \times 10^{-2} (\Deltan_{G} = 5-17 \times 10^{-3})
.