Phase-Shift-Locked Interferometer with a Wavelength-Modulated Laser Diode

A phase-shift-locked interferometer has been constructed for distance measurement. A phase shift produced by sawtoothcurrent modulation of a laser diode is locked to a phase difference preset by polarization optics that consists of a quarter-wave plate and polarizers through an electrical feedback technique. An optical path difference can be measured from the locked sawtooth-wave current amplitude in real time. The sensitivity of the interferometer is discussed. [Optical Society of America ]