Disturbance-free laser diode Sagnac interferometer using direct phase modulation

We exploited the wavelength tunability of the laser diode of a phase-shifting Sagnac interferometer to realize disturbance-free measurements. The Sagnac interferometer is robust against mechanical disturbances because it has a common path configuration and requires no special references. An unbalanced optical path was introduced between p- and s-polarized beams to enable easy phase shifting by direct current modulation. The experimental results indicate that the proposed system is effective for performing precise disturbance-free measurements.