  The optical and electronic properties of the {\alpha}-SiTe, {\beta}-SiTe, and
RX-SiTe_2 are investigated. A detailed analysis of electronic properties is
done using standard density functional theory (DFT) and hybrid functional
(HSE06) methods. The optical dielectric properties are studied under three
different methods: standard DFT, many-body Green's functions (GW), and
Bethe-Salpeter equation (BSE). Our calculations show that the SiTe compounds
possess extremely high static dielectric constants in their bulk forms
({\epsilon}_0({\bot}) = 68.58, {\epsilon}_0({\parallel}) = 127.29 for
{\alpha}-SiTe, and {\epsilon}_0({\bot}) = 76.23, {\epsilon}_0({\parallel}) =
98.15 for {\beta}-SiTe). The frequency-dependent dielectric functions
Im({\epsilon}) have very large values (>100) in the optical regime, which are
among the highest of layered materials, suggesting them as excellent light
absorbents in the corresponding frequencies. {\alpha}-SiTe exhibits a high
degree of optical anisotropy as compared to the other two compounds, consistent
with their structural configurations. A strong interlayer excitonic effect is
observed in bulk RX-SiTe_2. In addition, an analysis of Raman intensity is also
performed.
