  We describe a laser interferometer experiment for the undergraduate teaching
laboratory that achieves picometer sensitivity in a hands-on table-top
instrument. In addition to providing an introduction to interferometer physics
and optical hardware, the experiment also focuses on precision measurement
techniques including servo control, signal modulation, phase-sensitive
detection, and different types of signal averaging. After students assemble,
align, and characterize the interferometer, they then use it to measure
nanoscale motions of a simple harmonic oscillator system, as a substantive
example of how laser interferometry can be used as an effective tool in
experimental science.
