Effects of the chirality and functionality of monomers on the holographic gratings formed in photosensitive films

Abstract

Photosensitive holographic polymer films were fabricated. Instead of liquid crystals, a nonreactive high-refractive-index diphenyl sulfide was mixed with several monomers and an initiator for the preparation of the holographic grating films. To investigate the formation of periodic arrays of the photosensitive refractive-index modulation films and the effects of the chirality and functionality of monomers on the diffraction efficiency, chiral monomeric (Ϫ)-bornyl acrylate, (ϩ)-bornyl acrylate, and the racemate (Ϯ)-bornyl acrylate were synthesized and copolymerized with various multifunctional monomers. A reasonable schematic of the photosensitive polymerization mechanism was proposed. The effects of the multifunctional monomers, initiator concentrations, and feed monomer concentrations on the diffraction efficiencies were investigated. The morphologies of the polymer matrices were studied with scanning electron microscopy. Pictures of real light diffraction patterns with 15 grating points were obtained. In comparison with those described in the literature, the diffraction efficiency obtained in this investigation was relatively high.

Creation of periodic structures in a thick photopolymerizing layer

“…In such media, due to the weak absorption of actinic radiation, a steady distribution of light intensity can be provided over the entire depth of a fairly thick layer 23,24 by holographic methods. [25][26][27] However, in real conditions, the possible thickness of an optically recorded grating is limited by many factors causing blurring or noising of the interference pattern. 28 Among them, fluctuations in the optical density of the photosensitive medium, phase disturbances, instability or inhomogeneity of the radiation intensity, and the speckle noise can be indicated.…”

“…Recently, photopolymerizable compositions (PPCs) sensitive to visible radiation, 19–22 which allow light to initiate nonuniform polymerization in the volume, have become increasingly popular. In such media, due to the weak absorption of actinic radiation, a steady distribution of light intensity can be provided over the entire depth of a fairly thick layer 23,24 by holographic methods 25–27 . However, in real conditions, the possible thickness of an optically recorded grating is limited by many factors causing blurring or noising of the interference pattern 28 .…”

A theoretical analysis of refractive-index grating waveguide structures for integrated optics

“…In recent years, man has investigated several kinds of refractive-index polymeric waveguide gratings with a uniform surface, fabricated by photopolymerization [8][9][10] and photoreaction [11][12][13]. Refractive-index gratings have many advantages over their competitors, such as simpler fabrication method, better photosensitivity and smoother surface.…”