<title>Light-induced volume-phase holograms for cold neutrons</title>

Abstract

We succeeded in characterizing by long-wavelength neutron diffraction light-induced volume phase holograms which have been recorded in photopolymers. The samples were prepared from protonated and deuterated poly-(methylmethacrylate). They initially contained about 10 -15 % monomers and a photo-initiator.Discs of about 2 mm thickness and 2 to 3 cm diameter were exposed, in a conventional two-beam interference set-up, to a periodic light intensity pattern, with fringe spacings between 120 and 390 nm. The illumination modulated the neutron optical refractive index. This was due to a density variation which was introduced by a diffusion-controlled photopolymenzation, within the light regions, of the residual monomers.The neutron djffraction has been observed using the full length of the 80 m small-angle camera Dl 1 at the High-Flux Reactor, Grenoble. The primary neutron beam was monochromatized at around = 1 nm within AX/? = 18 % full width and collimated within 0.75 mrad. The amplitude of the neutron refractive index modulation of the protonated samples was by i05 smaller than the light refractive index modulation if using a helium-neon laser beam of X = 633 nm (R.A. Rupp, J. Hehmann, R. Matull, K. Ibel, Phys. Rev. Lett. 64 (1990) 301). The neutron reflectivity of the fully deutcrated samples, 1.4 %, was by a factor 40 larger than that of the protonated samples (R. Matull, P. Eschkotter, R.A. Rupp, K. Ibel, Europhys. Lett. 15 (1991) 133); this makes these gratings to valuable etalons for neutron small-angle cameras. Possible further applications of our research include: the study of light-induced neutron refractive index changes and of photochemical processes in situ using a radiation which does not alter the structure; the investigation of the factors which influence the regularity and stability of the holographic gratings; the development of neutron optical devices, as beam splitters, mirrors, lenses; and, in a more distant future, the construction of instruments, e.g., neutron interferometers and neutron microscopes. 0-8194-0687-2/91 /$4.0O SPIE Vol. 1559 Photopolymer Device Physics, Chemistry, arid Applications II (1991) / 393 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/27/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx