AIR-REFRACTIVE-INDEX STABILIZATION USING A FABRY-PEROT CAVITY AND A HE-NE FREQUENCY STABILIZED LASER

摘要

The displacement measurement with sub-nanometer resolution is required due to the progress of nanotechnology. Commercial laser interferometers, including homodyne and heterodyne interferometers, are widely used in displacement measuring systems because of their high resolution and traceability. However, in normal air environment, optical path difference (OPD) of the laser interferometers, which is used to derive the displacement, is changed owing to the air-refractive-index fluctuation (△n_(air)). If the △n_(air) level is bigger than 10~(-9)-order, it is difficult to achieve sub-nanometer resolution in the displacement measurement. Therefore, the stabilization of air-refractive-index is required for precise interferometers in the view of measurement uncertainty reduction.