A survey of optical nonlinearities theory and observation in (AlGa)As injection lasers

As a guide to understanding laser spectra, the results of published theories of nonlinear interactions in injection lasers are expressed in terms of a dimensional constant P¿, the power at which the effective steady-state gain, i.e.(gain/loss), at fixed junction voltage is halved. An analytical expression for P¿ is derived; with it the numerical value of P¿ corresponding to any particular theoretical model of optical nonlinearity can be deduced. This permits quantitative comparison of the strengths of the various model nonlinearities with each other as well as with experimental observation on actual devices. The paper deduces P¿ from the published analysis of two-photon absorption and of several formulations of spatial and spectral hole burning. Tabulations of the general expressions for P¿, of numerical values calculated for particular devices, and of observed values, indicate which interactions might be affecting the spectra of specific lasers. They also suggest experimental tests of nonlinear models.