  We performed terahertz time-domain spectroscopy, low-frequency Raman
scattering, and Brillouin light scattering on vitreous glucose to investigate
the boson peak (BP) dynamics. In the spectra of {\alpha}({\nu})/{\nu}2
[{\alpha}({\nu}) is the absorption coefficient], the BP is clearly observed
around 1.1 THz. Correspondingly, the complex dielectric constant spectra show a
universal resonancelike behavior only below the BP frequency. As an analytical
scheme, we propose the relative light-vibration coupling coefficient (RCC),
which is obtainable from the combination of the far-infrared and Raman spectra.
The RCC reveals that the infrared light-vibration coupling coefficient
CIR({\nu}) of the vitreous glucose behaves linearly on frequency which deviates
from Taraskin's model of CIR({\nu}) = A + B{\nu}2 [S. N. Taraskin et al., Phys.
Rev. Lett. 97, 055504 (2006)]. The linearity of CIR({\nu}) might require
modification of the second term of the model. The measured transverse sound
velocity shows an apparent discontinuity with the flattened mode observed in
the inelastic neutron scattering study [N. Violini et al., Phys. Rev. B 85,
134204 (2012)] and suggests a coupling between the transverse acoustic and
flattened modes.
