Optical Constants of Germanium in the Region 1 to 10 ev

TLDR

Reflectance of single‑crystal germanium was measured from 0.6 to 11.3 eV, the phase was derived via Kramers–Kronig analysis, and the refractive index and extinction coefficient were obtained from the Fresnel reflectivity equation. The refractive index peaks at 5.5 at 2.07 eV and 4.2 at 3.2 eV, falling to ≈1 above 6 eV, while the extinction coefficient peaks at 2.0 at 2.5 eV and 4.2 at 4.4 eV; below 3.5 eV the data agree with Archer, but diverge beyond that.

Abstract

The reflectance, ${|r(\ensuremath{\lambda})|}^{2}$, of single-crystal germanium was measured in the range 0.6 to 11.3 ev. The phase, $\ensuremath{\theta}(\ensuremath{\lambda})$, was computed from these data using the Kramers-Kronig relation between the real and imaginary parts of the complex function $\mathrm{ln}r=\mathrm{ln}|r|+i\ensuremath{\theta}$. The optical constants, $n$ and $k$, were then determined from the Fresnel reflectivity equation. The real part of the refractive index, $n$, has maxima of 5.5 at 2.07 ev and 4.2 at 3.2 ev. Above 6 ev, the index is very nearly 1. The extinction coefficient, $k$, shows maxima of 2.0 at 2.5 ev and 4.2 at 4.4 ev. Below 3.5 ev, the results are in good agreement with the recent measurements of Archer. Beyond this point, they depart from his extrapolated curve.