\begin{table}%t1
\caption{Complex refractive indices ($m=n+{\rm i}~k$) at a wavelength~$\lambda$ for candidate constituent materials.}\label{tbl-1}
%\centering
\par
\begin{tabular}{p{0.2\linewidth}llp{0.4\linewidth}}
\hline
\hline
Material           & $m$~at~$\lambda=450$~nm  & $m$~at~$\lambda=600$~nm  & Reference \\
\hline
Magnesium-rich olivine & $1.69+ {\rm i}~1.04\times{10}^{-4}$ & $1.68+ {\rm i}~1.15\times{10}^{-5}$ & \citet{huffman76}\\
Organic refractory  & $1.91+{\rm i}~3.17\times{10}^{-1}$&$1.97+{\rm i}~2.79\times{10}^{-1}$&\citet{li-greenberg97}\\
Amorphous carbon    &$1.95+{\rm i}~7.86\times{10}^{-1}$&$2.14+{\rm i}~8.05\times{10}^{-1}$&\citet{rouleau-martin91}\\
Pyrrhotite                &$1.45+{\rm i}~1.53 $              &$1.70+{\rm i}~1.86$               &\citet{egan-hilgeman77}\\
\hline
\end{tabular}
\end{table}