Disperse Red 1 Research Articles

A new way of improving non-linear optical properties of side-chain non-linear optically active copolymers

A new set of side-chain non-linear optical copolymers containing two different amounts of 2-methyl-4-nitroaniline (MNA) and disperse red 1 (DR1) chromophores are reported. From this set of copolymers, it is easy to see how to optimize such key properties as glass transition temperature, maximum absorption wavelength and second harmonic signal, d 33. The composition dependence of these properties is seen to vary linearly with MNA and DR1 content.

Novel naphthoquinone methide dyes for second-order nonlinear optical materials

Naphthoquinone methide dyes show a large Pockels coefficient at 1.3 µm when poled in a polymer matrix: the second-order nonlinear hyperpolarizability (µβ) values obtained from Pockels coefficients that appear after poling in a constant electric field are (5700–7400)× 10–48 esu, being much higher than that of commonly used Disperse Red 1 (DR1).

Determination of complex tensor components of electro-optic constants of dye-doped polymer films with a Mach–Zehnder interferometer

The complex electro-optic constants of disperse red 1 (DR1) dye molecules doped in polymethylmethacrylate film were measured by a scanning Mach–Zehnder interferometric technique. Despite a very small absorbance at 632.8 nm, DR1 molecules still have a measurable imaginary part of the EO constants. Two independent complex components, r̃13 and r̃33 were determined by incident angle dependence. The ratios Re[r̃33]/Re[r̃13] and Im[r̃33]/Im[r̃13] are 3.5±0.5 and 3.2±0.9, respectively. These results show that EO response is dominated by the electronic mechanism. The influence of multiple reflection in polymer film on the experimental results are briefly discussed.

Rotational reorientation dynamics of disperse red 1 in polystyrene: α -relaxation dynamics probed by second harmonic generation and dielectric relaxation

Using a novel experimental protocol involving second harmonic generation (SHG), the rotational, reorientation dynamics of disperse red 1 (DR1) chromophores doped at 2 wt. % in polystyrene (PS) have been monitored over 11 decades in time, from 10−6 s onwards. This nonlinear optical (NLO) technique allows quantification of the average rotational, reorientation time constant 〈τ〉 over a broad range of temperatures, 28 to 138 °C, above and below the glass transition temperature Tg. Good agreement was obtained between 〈τ〉’s determined from SHG and dielectric relaxation measurements. This is expected since both SHG and dielectric relaxation measurements of PS+2 wt. % DR1 monitor the rotational reorientation of DR1 chromophores. Values of 〈τ〉 fit well to a Williams–Landel–Ferry equation above Tg, indicating that the rotational reorientation of DR1 is coupled to the α relaxation of PS; below Tg the values of 〈τ〉 show an apparent Arrhenius temperature dependence with an activation energy of 45–50 kcal/mol. Above Tg, the SHG data are in agreement with the literature values of the temperature dependence of the α-relaxation dynamics for homopolymer PS obtained using NMR, viscosity, compliance, and photon correlation spectroscopy measurements; at Tg the absolute values of 〈τ〉 obtained by SHG are also in good agreement with the literature values obtained for relaxation times in PS using NMR, photon correlation spectroscopy, and enthalpy relaxation. Upon scaling the data using a reduced parameter, Tr/T, where Tr is close to the calorimetrically determined Tg, an excellent overlap of SHG results for the rotational reorientation dynamics of DR1 and thereby the α transition in PS, poly(ethyl methacrylate), and poly(isobutyl methacrylate) is observed below Tg; however, above Tg, the PS data show a much stronger temperature dependence, suggesting that PS may be a more ‘‘fragile’’ glass-former than the methacrylate-based polymers. Physical aging greatly shifts the relaxation to longer times, resulting in a significant increase in the temporal stability of SHG properties in these NLO polymers.

Photoinduced orientation of azo dyes in polymeric films. Characterization of molecular angular mobility

The reversible cis-trans photoisomerization of azobenzene derivatives is very sensitive to the polarization of the pumping beam which induces birefringence and dichroism. Recently, we have demonstrated a new method for poling azo dye-containing polymers, at room temperature, by applying a d.c. electric field during the optical pumping process. Here, we present a model for the dynamics of the photoinduced modifications of the angular distribution of chromophores and we compare a guest-host system (Disperse Red 1 (DR1) in PMMA) and a PMMA-DR1 copolymer.

Stable and Large Second Harmonic Generation in Sol-Gel-Processed Poled Silica Waveguides Doped with Organic Azo Dye

Sol-gel-processed silica films doped with organic azo dye, Disperse Red 1 (DR1) in a higher concentration of 21.7 wt%, were prepared at a higher baking temperature with corona poling of higher voltage than in other reports to obtain stable and large second harmonic generation (SHG) and film strength. A large effective SHG coefficient of 75 pm/V was measured for the film of 0.2-µm thickness at a fundamental wavelength of 1064 nm, and the value was unvaried for 700 h with no relaxation. Moreover, a waveguide SHG device of four-layer structure with DR1-doped sol-gel film as a top layer was fabricated for the first time, and Cherenkov-type phase-matched SHG was observed successfully.

Ultraviolet defined selective in-diffusion of organic dyes in polyimide for applications in optical interconnection technology

We report here, for the first time, a novel ultraviolet (UV) defined selective in-diffusion technique for refractive index alterations in a BTDA-alkylated diamine type of preimidized polyimide film. This has been achieved by in-diffusing disperse red 1 (DR1) dye into the polyimide film from an organic solvent-based solution. UV photocrosslinking of the polyimide chains was observed to significantly suppress the in-diffusion of DR1 and provided the means for selective doping of this dye in the polyimide film. This technique is amenable to a laser direct write maskless approach for applications in integrated optics. We have demonstrated this technique by fabricating a low-loss (<0.5 dB/cm) embedded polyimide channel waveguide.

Photoassisted poling of azo dye doped polymeric films at room temperature

The reversible cis-trans photoisomerization of disperse red 1 (DR1) in PMMA thin films has been demonstrated to be strongly polarization sensitive [1]. In this communication two mechanisms are identified: the angular hole burning and the angular redistribution of molecules. It is shown that, in the presence of a DC electric field, the redistribution is not centrosymmetric and produces a poling of the film. The evolution of the second-order nonlinear susceptibility, χ(2), is monitored by measuring the electro-optic effect by attenuated total reflection and by second-harmonic generation.

Photoisomerization of azobenzene derivatives in polymeric thin films

The photoisomerization of disperse red 1 (DR1) in polymethylmethacrylate thin films is demonstrated by monitoring the refractive index variations by the attenuated total reflection method. Absorption spectrum measurements give a confirmation of this phenomenon. The kinetics of photoisomerization and of thermal relaxation are nonexponential. Some other molecules are studied. As in solution, azobenzene derivatives (N—N) produce reversible isomerization while dimethylaminonitrostilbene, a stilbene derivative (C—C), exhibits no thermal cis→trans relaxation.

Polarization effects in photoisomerization of azo dyes in polymeric films

The reversible cis-trans photoisomerization of disperse red 1 (DR1) in PMMA thin films has been demonstrated previously by using the Attenuated Total Reflection (ATR) method. In this communication photoisomerization of DR1 is shown to be strongly polarization sensitive. This new property of dye doped polymeric films could lead to practical applications in integrated optics. A simple molecular interpretation is given. Illumination of a DR1 sample by polarization fringes produces a grating of molecular orientation able to diffract a probe beam.

Electrooptic Light Modulation in Poled Azo-Dye-Substituted Polymer Waveguides

The DC electrooptic modulation of 0.633-µm He-Ne laser light has been measured in thin-film waveguides of copolymers containing Disperse Red-1 (DR1) and/or novel dis-azo-dye side chains. The polarized laser light is butt-coupled to the polymer waveguides with propagation length of 4 mm and film thickness of 10-15 µm. The DC linear electrooptic coefficients r33 of the poled DR1- and dis-azo-dye-substituted polymer films are estimated to be 18 pm/V and 27 pm/V at 0.633 µm. Comparison with second-harmonic generation results demonstrates that the DC linear electrooptic effect in the poled azo-dye-substituted polymers is primarily electronic in nature.