Biphoton-Induced Refractive Index Change in 4-Amino-4‘-nitroazobenzene/Polycarbonate

Abstract

Transient biphotonic optical storage in the guest−host system 4-amino-4‘-nitroazobenzene/polycarbonate is accomplished by excitation of the azo dye molecules at 488 nm with an argon ion laser and subsequent writing at 633 nm with two interfering HeNe laser beams. The mechanism of the observed refractive index change is investigated by detailed kinetic studies. It is based on the formation of cis isomers of the azo dye by the argon ion laser. These are subsequently transformed back to the trans isomers by fast photoinduced cis−trans isomerization where the interference of the writing beams is constructive and by slow thermal cis−trans isomerization where the interference of the HeNe beams is destructive, respectively. The cis concentration produced by the exciting light is thus modulated with the HeNe beams, resulting in a modulation of the refractive index.

Biphotonic holographic gratings in azobenzene polyesters: Surface relief phenomena and polarization effects

“…The liquid crystalline structure of our polymer, with strong cooperative interactions among the molecules, can strengthen the influence of aggregation and reorientation processes with respect to amorphous polymers previously studied. [9][10][11][12] Those processes can give place to an increase of the diffracted light and to a relief grating as observed in our surface relief experiments. A similar mechanism has been proposed to explain some of the phenomena observed in gratings induced with coherent blue light.…”

“…They have explained it in terms of a spatial modulation of the isomer populations induced by the interference of the two He-Ne laser beams. [9][10][11] The growth of the diffraction efficiency observed in our experiments when the two He-Ne beams and the Xe lamp are present could be explained using the same model. When the Xe lamp is switched off, only cis to trans isomerization takes place in the illuminated areas and a reinforcement of the contrast between both populations would occur.…”

“…Another type of holographic storage has also been reported using coherent red light by means of biphotonic processes. [9][10][11][12] In these processes, a blue incoherent light is used to sensitize the azo chromophores in the red region and recording is performed with a coherent red source. This allows diode lasers to be used which is important for photonic applications.…”

High diffraction efficiency polarization gratings recorded by biphotonic holography in an azobenzene liquid crystalline polyester

“…10,11 In addition, holographic recording can also be performed with coherent red light using biphotonic processes. 12,13 In these processes an incoherent blue light source is used to generate a cis population. Thus, the polymer film becomes sensitized to light in the red region and recording is performed with a coherent red light source.…”

A study on tautomeric investigation of new hetarylazo-6-aminouracil

“…14 Non-textile uses of hetarylazo disperse dyes have been explored, for example in reprographic technology, functional dye applications, and non-linear optical systems. [25][26][27] It is well-known that mono-azo dyes prepared from enol-and enamine-type coupling components exhibit azo-hydrazone tautomerism. [28][29][30][31][32][33][34][35] Determination of azo-hydrazone tautomerism both in solid state and solution phase is quite interesting both from theoretical and practical standpoints, since the tautomers have different technical properties and dyeing performance.…”