Optical Poling Process Research Articles

Second-harmonic generation in an optically poled azo-dye/polymer film

The power dependence of the optical poling process of a new azo chromophore in the polymethylmethacrylate matrix at room temperature has been investigated. The existing theory is found to be inconsistent with the experiment. A simple model based on the rate equation is proposed to describe the writing process of the chromophore/polymer system. The measured growth rate and the plateau second-harmonic generation intensity as induced by all optical poling are found to be in good agreement with the prediction of the simple model.

Carrier-Envelope Phase-Controlled Quantum Interference in Optical Poling

We demonstrate the efficiency of the optical poling process that depends on the CE phase-controlled quantum interference. For the experiment we employed our noncollinear optical parametric amplifier system for the self-stabilization of the CE phase, with the f-to-2f spectral interferometry system to control the CE phase.

Restriction of the efficiency of photoinduced second-harmonic generation during optical poling of germanium-silicate glass

The large growth of the absorption of radiation with doubled frequency in a region of high values for the induced electric fields has been detected during the investigation of an optical poling process in germaniumsilicate glass. The absorption suppresses the writing of the second-order susceptibility grating and leads to restriction of the maximum efficiency of the photoinduced second-harmonic generation in the glass.

Optical poling of oligoether acrylate photopolymers doped by stilbene-benzoate derivativechromophores

A large second harmonic generation (SHG) excited by an Nd:YAG laser(λ = 1.32 µm) has been observed during the investigation of the optical poling process in2-(stilbene-4-yl)benzoxazole derivatives chromophores incorporated within oligoetheracrylate photopolymer matrices. We have revealed that the maximum outputSHG is observed for the chromophore derivatives molecule possessing the highestsecond-order hyperpolarizabilities and corresponding dipole moments. Due tothe incorporation of the chromophore into photopolymer matrices, second-ordermicroscopic susceptibilities of the composites substantially increase (from 0.24 up to1.89 pm V−1). The investigated composites possess long-lived polarized states and after more than106 laser pulses the output SHG did not decrease below 75% compared with the initial SHG one. Optimalconditions for optical poling corresponded to a power density of the doubled frequency beam of about0.07 GW cm−2 and chromophore content about 6.5% (in weighting units).

Writing Laser Power Dependence of Second Harmonic Generation in an Optically Poled Azo-dye/polymer Film

ABSTRACTThe time and power dependence of the optical poling process of an azo chromophore in the PMMA matrix at room temperature is investigated. A model previously proposed is used to account for the writing process of the optical poling of the chromophore/PMMA system. Theoretical predictions of the growth rate and the plateau SHG intensity are found to be in good agreement with the experimental result.

Optical poling of oligoether acrylate photopolymers doped by 1- H-pyrazolo[3,4-b]quinolines derivative chromophores

Second harmonic generation excited by Nd:YAG laser ( λ=1.32 μ m) was observed during the investigation of second-order optical poling process in 1- H-pyrazolo[3,4-b]quinolines chromophores incorporated within the oligoether acrylate (OEA) photopolymer matrices. We have found that the observed SHG output is correlated well with the values of corresponding dipole moments. Due to incorporation of the chromophore into photopolymer matrices second-order microscopic hyperpolarizabilities of the composites substantially increase (up to 3.01 pm/V). The investigated composites possess long-lived photopolarized states and after about 10 5 laser pulses the output SHG output signal did not decrease below 75% compared to the SHG signal in the beginning of the treatment. Optimal conditions of the optical poling corresponded to power density of the doubled frequency beam about 0.024 GW/cm 2 and chromophore content about 5.2% (in weighting unites).

Limitation of optical poling in germanium-silicate glasses

The giant increase of the absorption of the radiation with the doubled frequency in a region of high values of the optically-induced electric fields (about 10 5–10 6 V/cm) has been observed during the investigation of the optical poling process in germanium-silicate glass. The absorption suppresses the writing of the second-order susceptibility grating and leads to the restriction of the maximum efficiency of the photoinduced second harmonic generation in glass. We demonstrate that the observed effect is not anisotropic and may be considered as a consequence of a competition between the charge separation by the local trapping levels due to electrostricted photoinduced phonons and recombination diffusion of carriers.

Giant increase of the second harmonic radiation's absorption during optical poling of oxide glass

A giant reversible growth (≥ 103 times) of the absorption of second harmonic radiation by optical poling of oxide glass was discovered. The observed absorption exerts an influence on the optical poling process and leads to a restriction of the maximum value of the photoinduced second harmonic generation in oxide glass. A theoretical model of the observed phenomenon is given. The growth of absorption is considered as a result of special anharmonic electron-phonon interactions caused by photoinduced electrostricted phonons. Exploration of the total absorption indicates that the effects of photodarkening do not play a key role in the observed phenomena.

Effect of temperature on the optical poling process in a side-chain polymer system

An improvement to the Fiorini and Nuzi’s theory for all-optical poling is proposed. The influence of cis is taken into account in the photoinduced process. An analytical expression for the dynamic optical poling process is derived. Contrary to Fiorini and Nuzi’s theory which is based on unique process, three processes exist in the time evolution of the photoinduced second-order susceptibility χ(2) during the optical poling: two of which are fast and the other one which is slow. Furthermore we discuss the influence of temperature on the poling process in a side-chain polymer system with a high glass transition temperature. It is predicted that the two fast processes will become even faster and their relative contribution to the magnitude of χ(2) will decrease with the increase of temperature. The prediction is verified by our experiment with disperse red 19-functionalized polyimide polymer.

Thermosetting enhancement of the light-induced polar orientation stability of molecules in polymers

Two kinds of polymers with disperse red 19 pendant groups, a thermal-imidization polyimide and a thermal-crosslinking polyurethane, were used in thermal-assisted optical poling to improve the photostability of the optically induced polar orientation of molecules. During the seeding process, samples heated in an oven were irradiated simultaneously by the coherent superposition of the 1064 nm fundamental and the 532 nm second-harmonic light of a nanosecond-pulsed Nd:YAG laser. The second-order optical nonlinearity of the polymer films seeded at elevated temperatures kept stable at room temperature even under illumination of the intense 1064 nm fundamental light. The nonlinear optical coefficient d33 was estimated to be 6.9 pm/V for the azopolyimide film and 12.7 pm/V for the azopolyurethane film, respectively. Experimental results indicated that the optically aligned azodye molecules were fixed by the thermosetting polymer matrix during the thermal-assisted optical poling process.