title: Subpicometer length measurement using semiconductor laser tracking frequency gauge.
abstract: We have demonstrated heretofore unattained distance precision of 0.14 pm (2 pm) incremental and 14 nm (2.9 μm) absolute in a resonant (nonresonant) interferometer at an averaging time of 1 s, using inexpensive telecommunications diode lasers. We have controlled the main source of error, that due to spurious reflection and the resulting amplitude modulation. In the resonant interferometer, absolute distance precision is well under λ/6. Therefore, after an interruption, an absolute distance measurement can be used to return to the same interferometer order.
authors.affiliation: Smithsonian Astrophysical Observatory, Harvard Smithsonian Center for Astrophysics, Cambridge, Massachusetts 02138, USA.
authors.forename: Rajesh
authors.initials: R
authors.lastname: Thapa
authors.forename: James D
authors.initials: JD
authors.lastname: Phillips
authors.forename: Emanuele
authors.initials: E
authors.lastname: Rocco
authors.forename: Robert D
authors.initials: RD
authors.lastname: Reasenberg