Massively parallel interferometry: towards the all-integrated lambdameter

Abstract

In this paper we present recent work about the application of digital phase detection for accurate wavelength measurement using two beam interferometry (lambdametry). The advantage of two beam interferometry is the sinusoidal fringe signal for which precise phase detection algorithms exist. Modern algorithms can cope with different sources of errors, and correct them. We recall the principle of the Michelson-type lambdameter using temporal interference and we introduce the Young-type lambdameter using spatial interference. The Young-type lambdameter is based on the acquisition of the interference pattern from two point sources (e.g. two ends of monomode optical fibers) projected onto a CCD camera. The measurement of an unknown wavelength can be achieved by comparison with a reference wavelength. Accurate interference phase maps can be calculated using spatial phase-shifting. In this way, each small group of contiguous pixels acts as a single interferometer, and the whole set of pixels corresponds to a massively parallel interferometric measurement system (up to many hundreds of thousands units). The major advantage of our method is its structural simplicity and the possibility of full optical integration. The final goal is to achieve a relative uncertainty of the order of some 10 -8 with a measurement duration of the order of some minutes. Preliminary results are presented.