Gain, refractive index change, and linewidth enhancement factor inbroad-area GaAs and InGaAs quantum-well lasers

摘要

We report experimental and theoretical results for theninjection-level dependence of the gain, refractive index variation, andnlinewidth enhancement factor (Α) for four different quantum-welln(QW) laser structures. Two of the lasers have GaAs QW layers that varynin width while the other two have InGaAs active layers that vary in QWndepth. Experimental Hakki-Paoli data are used to compare gain, indexnchange, and Α-parameter between these pairs of devices. Thenresults of two simulations are compared to the experimental data. Thenfirst is based on the approximation of parabolic bands for both thenconduction and valence bands while the second employs the k·pnmethod to refine the calculation of the valence bands. Our findingsninclude: (1) narrower and deeper QWs yield lower Α values; (2)nmodeling results from the k·p method are only slightly improvednover those from the parabolic band model; (3) at high injection levels,nstimulated emission below threshold is a prominent effect in thesendevices; and (4) at high injection levels, carriers in the barriernenergy states above the well are shown to be responsible for increasingnΑ values