TITLE:
Self-Enhancement of Scalar and Vector Holographic Gratings in Azobenzene Molecular Glassy Films
AUTHORS:
Andris Ozols, Valdis Kokars, Peteris Augustovs, Dmitrijs Malinovskis, Kaspars Traskovskis, Elmars Zarins, Girts Ivanovs
KEYWORDS:
Self-Enhancement of Holograms, Light Polarization, Holographic Gratings, Azobenzene Molecular Glasses
JOURNAL NAME:
Optics and Photonics Journal,
Vol.4 No.6,
June
20,
2014
ABSTRACT: Self-enhancement (SE) effect of scalar and vector holographic gratings (HG)
recorded in three different azobenzene molecular glassy films is experimentally
studied in both transmission and reflection modes at 532 and 633 nm. The
maximal SE factor (the ratio of diffraction efficiency to its initial value)
SEF = 42 has been achieved. It is shown that the model of complementary HG can
be applied also in scalar transmission thin HG case to explain coherent SE. The
possibility of vector HG coherent SE in transmission mode is experimentally
demonstrated for the first time (SEF = 4.3). The possibility of coherent HG SE
in reflection mode is also established for the first time (SEF = 21). HG
recording processes as well as coherent SE processes are found to be
independent in transmission and reflection modes being determined by volume and
surface relief HG, respectively. The permittivity gradient mechanism is
proposed to explain the coherent SE of surface relief HG. Both HG recording and
coherent SE efficiencies strongly decrease when HG period is decreased from 2 mm to 0.5 mm. No
relaxational SE effect is found. Coherent SE effect in molecular glasses is
found to be weaker than in inorganic materials.