Adaptation to low temperatures of a differential interference contrast microscope with subnanometer sensitivity

We show how a differential interference contrast microscope can be adapted for low temperature operation by having only the microscope objective at lo w temperatures. The microscope's body, with delicate birefringent optics, i s kept at room temperature. A key part is the use of two Wollaston prisms w ith opposite anisotropic media to ensure a flat field. The device can detec t optical path differences of the order of 10 pm/mum with a few seconds of integration time. Images taken at several hour intervals can be subtracted, indicating good mechanical stability. (C) 2001 American Institute of Physi cs.