Unequal intensity splitting can reduce back action in interferometers

Typical two-path interferometers are intensity-balanced because this maximizes the visibility of their interference patterns. Unbalancing the interferometer can be advised when back action on the object whose position is monitored is to be reduced. Variations of the intensity splitting ratios in two-path interferometers are analyzed in order to determine optimal interferometric performance while minimizing back action: it turns out that homodyning-like schemes perform best.