Development of an ultrasensitive interferometry system as a key to precision metrology applications

Abstract

We present a symmetric heterodyne interferometer as a prototype of a highly sensitive translation and tilt measurement system. This compact optical metrology system was developed over the past several years by EADS Astrium (Friedrichshafen) in cooperation with the Humboldt-University (Berlin) and the university of applied science Konstanz (HTWG-Konstanz). The noise performance was tested at frequencies between 10^-4 and 3 Hz, the noise levels are below 1 nm/Hz ^1/2 for translation and below 1 μrad/Hz^1/2, for tilt measurements. For frequencies higher than 10 mHz noise levels below 5pm/Hz^1/2 and 4 nrad/Hz^1/2 respectively, were demonstrated. Based on this highly sensitive metrology system we also developed a dilatometer for the characterization of the CTE (coefficient of thermal expansion) of various materials, i.e. CFRP (carbon fiber reinforced plastic) or Zerodur. The currently achieved sensitivity of these measurements is better than 10^-7 K^-1. Future planned applications of the interferometer include ultra-high-precision surface profiling and characterization of actuator noise in low-noise opto-mechanics setups. We will give an overview of the current experimental setup and the latest measurement results.