Retarded Kerr effect

For optimum performance, CD measurements require a polarization modulated source. In principle, any of the polarization-selective optical devices discussed earlier could be mechanically moved to create the required modulation. However, this approach is problematic in that it is difficult to implement physically, the mechanical movement may introduce noise into the measurement situation, and there are limitations to the rate at which the polarization can be modulated. A preferable approach is to use an electronic device to effect the required phase retardation. Although a number of devices have been used for this purpose (e.g. magneto-optical, Kerr effect, etc.), modern CD instruments rely upon either the Pockels effect, or photoelastic modulation for this function. 

Computational analysis has been limited, on the other hand to the gas phase [40, 184, 185, 189, 190], However, optical apparata designed for measurements in the gas phase of other birefringences, as the Kerr and Cotton-Mouton effects, may in principle be adapted to measure JB and MEB. It is thus probably useful to provide reliable predictions of the magnitude of the effect. Table 19 shows a comparison from [40] of predicted birefringences and corresponding retardances for the two birefringences discussed in this section, i.e. CME and JB (or MEB). 

---