  Phase sensitivity determines the lowest optical path length (OPL) value that
can be detected from the noise floor in a quantitative phase microscopy (QPM)
system. The temporal phase sensitivity is known to be limited by both photon
shot-noise and a variety of noise sources from electronic devices and
environment. To beat temporal phase sensitivity limit, we explore different
ways to reduce different noise factors in off-axis interferometry-based QPM
using laser-illumination. Using a high electron-well-capacity camera, we
measured the temporal phase sensitivity values using non-common-path and
common-path interferometry based QPM systems under different environmental
conditions. A frame summing method and a spatiotemporal filtering method are
further used to reduce the noise contributions, thus enabling us to push the
overall temporal phase sensitivity to less than 2 picometers.
