Polarimetric methods
Figure 1 shows schematic designs of IR-DCP (a) and classical FTIR
polarimetry (b). Both methods aim to probe the polarization dependent
complex transmission (reflection) coefficients
txy = |txy| · exp(i Δxy),
which describe the progression of incoming y-polarized light into
x-polarized light. Both methods are sensitive to the transmission
Txy = |txy|2.Classical FTIR polarimetry can acquire relative phase differences for
two sets of polarization configurations, such
as Δxx – Δyy. For FTIR polarimetric
studies of materials with cos Δ ≈ 1 (Δ close to 0 or π), a retarder is
required as an additional optical element to achieve sufficiently high
accuracy. In contrast, IR-DCP can directly measure absolute phases
Δxy.