Absolute distance measurements using FTPSI with a widely tunable IR laser

Fourier transform phase-shifting interferometry is further developed and applied to the absolute measurement of interferometer cavities. Using a widely tunable IR laser diode initially developed for telecom applications along with specific interferometer cavities, I apply this new capability to the measurement of absolute cavity lengths, where a 1-sigma precision of 12.6 ppb is demonstrated and the technique was then used to determinate the absolute index and thickness of a transparent parallel plate.