Phase modulating two Fabry-Perot interferometry and its application to nanometrology

We discuss how to expend the SPM of double beam interferometer to multi-beam interferometer or Fabry-Perot interferometer and deduce the corresponding theoretical results in this paper. Besides the introduction section 1 the principle of Fabry-Perot interferometer and how to simplify the representation of its intensity are described in section 2. Two typical conditions such as (1) nearby the maximum and fineness coefficient F, the light phase θ satisfied the condition F sin²θ < 1 or (2) offset the maximum and F θ satisfied the condition F sin²θ > 1 considered. Phase modulating Fabry-Perot interferometry and theoretical results for 1, ramp, 2, saw teeth, 3, sinusoidal voltage modulating or SPM Fabry-Perot interferometer are deduced in section 3. It should be noted that the construction of double Fabry-Perot interferometer for nanometrology and the experimental results are stated in section 4. Our measurement resolution could be arrived in <0.3nm using the method of time space difference.