Interferometer Talbot

The very first demonstration of molecule interference dates back to the days of Estermann and Stern [Estermann 1930] who demonstrated experimentally diffraction of 11-2 at a LiF crystal surface in 1930. Further experiments with diatomic molecules had to await progress and interest in atom optics. A Ramsey-Borde interferometer was realized for the iodine dimer in 1994 [Borde 1994] and was recently used [Lisdat 2000] with K. Similarly, a Mach-Zehnder interferometer was demonstrated [Chapman 1995 (a)] for Na2. The nearfield analog to the Mach-Zehnder interferometer, a Talbot-Lau interferometer, was recently applied to experiments with L12 [Berman 1997], Diffraction at nanofabricated gratings also turned out to be the most effective way to prove the existence of weakly bound helium dimer [Schollkopf 1996] and to measure its binding energy [Grisenti 2000],... 

In contrast to these near field setups, a near-field interferometer of the Talbot-Lau type, does away with the collimation requirement and accepts spatially incoherent molecular beams. Such a scheme is much more compact, rugged and allows a much higher transmission [Clauser 1992],... 

As described above, the Talbot-Lau interferometer is essentially a lens-less imaging device which produces a strictly periodic molecular density pattern... 

Figure 10. Setup for the investigation of thermal decoherence. Up to 16 laser beams are used to heat the fullerenes before they enter the Talbot-Lau interferometer.

If one wants to observe the wave nature of even more massive molecules brilliant beams are needed that have a low molecular velocity. In practice one will hardly be able to work with de Broglie wavelengths less than 100 fm. For particles in the mass range of 105 amu this requires velocities of the order of vm = 10 rmm/s. Although this is a rather demanding requirement it seems not impossible to develop appropriate sources in the future. Moreover, a realistic earth-bound interferometer would be limited to a Talbot length of the order of one meter. 

In the Talbot-Rayleigh interferometer developed by Warenghem et al. [55, 56], the planar-oriented nematic cell is inserted in the focal plane of an ordinary spectroscope that covers only half of the field of polychromatic light. In this way dark bands (Talbot bands) appear due to the interference between the upper and the lower part of the beam. The position of the bands is correlated with the phase retardation (and, therefore, with the refractive index) induced by the nematic layer. By means of a proper spectrum analysis, dispersion curves of n and can also be determined. 

We know of many types of optical interferometer (the simple double-slit Young interferometer, the Mach-Zehnder interferometer, the Fabry-Perot interferometer, the Talbot interferometer, etc.). A similar situation occurs in atom interferometry. Artificial laboratory devices exploit various types of structure for atom interferometry both material bodies (slits and gratings) and nonmaterial light structures. All these atom interferometers will be considered very briefly we refer readers for details to the book by Berman (1997) and reviews by Baudon et al. (1999), Kasevich (2002), and Chu (2002). 

Figure 15 Combination of Talbot Interferometer consisting of two gratings and an X-ray Imaging microscope.

Figure 16 High-resolution X-nay phase tomogram of the PS/PMMA/PB ternary blend observed by the X-ray Talbot interferometer in combination with the X-ray imaging microscope shown in Rgure 15. The phase separation structure is revealed. Black spots are voids. Reproduced with permission from Momose, A. Takeda, Y. Takeuchi, A. Suzuki, Y. J. Phys Conf. Ser. 2009, 186, 012044. 2009 Institute of Physics.

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