Effect of intervalence band absorption on the refractive index of p-doped InSb

Kramers-Kronig analysis has been applied to the calculated intervalence ban d absorption (IVA) spectrum of p-doped InSb, calculated using 4-band Kane t heory, to determine its effect on the refractive index. In the region of th e band gap, IVA is found to cause a reduction in the refractive index. Othe r components contributing to the refractive index have also been calculated for purposes of comparison, and it is found that this reduction due to IVA is comparable to that caused by the change in the conduction-valence band absorption spectrum of p-type samples of the same doping density. It is, ho wever, much smaller than the reductions in the refractive index caused by c hanges in the absorption spectrum in similarly doped n-type samples, due to the Moss-Burstein shift and free carrier absorption. The implications of t hese results for laser design are discussed.