Multi-wavelength optical data processing and recording based on azo-dyes doped organic-inorganic hybrid film

Plasma immobilization of azobenzene dye on polyamide 6 polymer

Plasma treatment of polymeric materials is a cost-effective and efficient technique to modify the surface and change the constituent unit configuration. This research investigates the effects of argon DC glow discharge plasma on pure and DR1 dye-loaded polyamide 6 polymer films and stabilization of dye on the surface. Plasma breaks some bonds and activates the surface through creating reactive structures such as free radical sites on the surface and increases tertiary amides on the surface of polymer. Besides, this process alters surface topographical characteristics and conformation of azobenzene dye which are effective on the durability of the dye on the surface. Plasma causes interactions of the dye with the polymer and immobilizes the dye on the polymer. On the other hand, these interactions lead to changes in the dye's optical and geometric isomeric activity and stability. This work studies the chemical and morphological changes of polyamide 6 by plasma with AFM and spectroscopic methods. Furthermore, the aging of nylon 6 films loaded with DR1 dye is measured, and the conformational changes of the dye are investigated. Plasma stabilizes the dye on the polymer surface through making changes of chemical and physical properties on the surface components.

Influence of heating temperature on the optical response properties and surface relief patterns of TiO2/GeO2/ormosils composite films containing azobenzene

With the progress of modern integrated optical technology, organic-inorganic composite materials have been widely used in integrated optoelectronic devices. Because of satisfying optical response properties among azobenzene, it will be an ideal choice to introduce the material into organic-inorganic composite materials. TiO₂/GeO₂/ormosils composite films containing azobenzene were prepared by combining the solgel technique with the spin-coating process. The optical transmission modes and loss of as-prepared samples at different transmission wavelengths were researched by a prism coupler. The result shows that the composite film is multi-mode transmission at the transmission wavelength of 633 nm and single-mode transmission at 1538 nm. The transmission loss is sufficient for applications in optical elements. The response properties and Fourier transform infrared spectroscopy of as-prepared samples at different heating temperatures were also studied. The composite films obtained at 50°C have the best optical response properties. Furthermore, the banding energy and chemical composition among the films were measured through x-ray photoelectron spectroscopy. Finally, the surface topography of as-prepared samples was observed by atomic force microscopy. The surface of the composite film appears with patterns of relief under the appropriate temperature. The above results show that the as-prepared TiO₂/GeO₂/ormosils composite films containing azobenzene will be a kind of ideal material in the field of integrated optics applications.

A Modified Oxazolone Dye Dedicated to Spectroscopy and Optoelectronics

Here we present a newly synthesized bifunctional organic chromophore with appealing spectroscopic and nonlinear optical features. The positions of absorption and emission maxima of the dye vary with increasing solvent polarity and exhibit positive solvatochromism. The determined change in the dipole moment upon excitation based on the Bilot and Kawski theory is 5.94 D, which corresponds to the intermolecular displacement of a charge equal to 1.24 Å. An investigated organic-based system represents a significant, repeatable, and stable over time optical signal modulation in the manner of the refractive index value. Its magnitude is varied both by optical pumping intensity as well as by external frequency modulation, which indicates that such system is an alluring and alternative core unit for optoelectronic devices and complex networks. Then, the same active system, due to the nonresonant mechanism of higher harmonics of light inducement, can provide second and third harmonic signals. According to the introduced laser line spatial modifications (parallel or perpendicular polarization directions), it is resulted in output SHG signal with magnitude varied about 100%. Its magnitude is noticeably small; however, to construct sensitive optical sensors or infrared indicators, such feature may guarantee satisfying circumstances.

Fast readout method for multidimensional optical data storage using interferometry-aided reflectance spectroscopy

The multiplex technique increases the capacity of optical data storage, but the current reading throughputs is limited by the single-bit reading. We propose a fast readout method of multidimensional optical data storage using interference-aided reflectance spectral measurement to readout multiple bits information simultaneously. The multidimensional data is recorded in the photoresist layer on the disc with dielectric multilayer substrate by laser direct writing. With the designed interference layer inside the disc, the relation of thickness of recording layer and the peak shift of the reflected spectra has been built up. With different writing depths representing different bit of data, 2 bits and 3 bits unit information have been recorded and successfully read out at one exposure. This fast readout method is not only suitable for optical data storage by engineering the optical path length for example Blu-ray disc but also for super resolution optical data storage.

Fluorescence Spectral Properties of Methyl Orange in Homogeneous Media

The methyl orange [C₁₄H₁₄N₃SO₃Na], an azo dye exhibited strong emission and large Stokes shift in various solvents, and the largest shift (Δλ = 125.51nm or Δν = 9297cm^-1) was obtained in the water. The UV-visible spectra of the dye showed the absorption in the range (33,333 - 20,000) cm^-1. We found that solvent effects on the absorption wavelength are consistent. The bathochromic shift in water and the hypsochromic shift in methanol observed in the absorption (43 nm) as well as in the fluorescence (42 nm) spectra predict the strong solute-solvent interaction. The fluorescence quantum yield (ɸ_f) was decreased from 24% in DMSO to 5% in water. The fluorescent properties of this dye are strongly solvent dependent, the wavelength of minimum fluorescence emission (λ_em = 435.51nm) shifts to the red. The maximum and minimum calculated oscillator strength is 32% with (Ɛ_max = 29011 M^-1cm^-1) and 11% (Ɛ_max = 6682 M^-1cm^-1) in methanol and DMSO, respectively. Protonated solvents without exception give a shorter lifetime and lower quantum yield. The average excited-state lifetime of the dye was found maximum (τ_av = 5.36 ns) in DMSO. Also, fluorescence lifetime was combined to deduce the radiative and non-radiative decay rate.

Probing the high performance of photoinduced birefringence in V-shaped azo/PMMA guest-host films

Optical birefringence in polymeric films containing azo-chromophores is an important feature related to the development of several technologies such as electro-optic modulators, optical switching, and optical gates, to cite a few. Therefore, it is essential to understand the main underlying mechanisms describing dynamic switching. In this context, we have investigated the optical birefringence performance of a guest-host film produced from a poly(methyl methacrylate) (PMMA) matrix containing a V-shaped azo-chromophore, which exhibited a larger optical response in comparison to the linear chromophores. The optical birefringence was induced by a linearly polarized diode laser (532 nm, writing laser), while a low-intensity HeNe (632.8 nm) laser and a tungsten-halogen lamp are employed, respectively, to monitor the optical storage and the absorption change during the photoinduced birefringence. Our results pointed out that the guest-host film presents maximum residual optical memory at around 50% and local optical birefringence at around 3.3 × 10^-4 in the low concentration and intensity regimes. The high optical birefringence obtained in guest-host films was attributed to the considerable photoisomerization quantum yield in the solid-state (0.15 ± 0.02 for 532 nm). Besides, we have shown that the switching mechanism is driven by angular hole-burning during the first seconds after excitation, and, subsequently, molecular reorientation quickly rises, dominating the photochemical process. The latter mechanism is highly efficient in converting cis to trans molecules (100%), which is responsible for the high residual optical memory obtained. In order to better understand the isomerization mechanism of the azo-chromophore/PMMA film, we performed quantum chemical calculations within the DFT framework. The electronic transitions of the azo-chromophore isomers were determined using the TD-DFT method and potential energy curves (PECs) were constructed to investigate the possibility of the thermal-isomerization process of the V-shaped azo-chromophore through both rotation and inversion mechanisms. For both mechanisms, the amplitude of the energy barrier and activation energy for thermal isomerization are determined and the results are discussed.