Zhenqian Wei

Bio: Zhenqian Wei is an academic researcher from Jilin University. The author has contributed to research in topics: Azobenzene & Birefringence. The author has an hindex of 6, co-authored 10 publications receiving 232 citations.

Photoinduced birefringence and reversible optical storage in liquid-crystalline azobenzene side-chain polymers

Abstract: A liquid crystal with an azobenzene moiety as a photoactive mesogenic unit is investigated in photoinduced birefringence. Measurements reveal that it possesses large magnitude of photoinduced birefringence (Δn∼10−2) and the characteristic of long-term optical storage. The resulting polarization information can be erased either by heating the sample to a temperature much higher than the glass transition temperature, or by optical method with a circularly polarized light. The mechanism of long-term optical storage is discussed in this letter.

Biphoton holographic storage in Methyl Orange and Ethyl Orange dyes

Abstract: Biphoton holograms are recorded by a He–Ne laser in Methyl Orange and Ethyl Orange dyes on exposure to 514.5-nm argon-ion laser, and the dynamic of holographic recording is reported. The recording utilizes an unusual photochemistry that is due to either to a triplet–triplet transition from a long-lived triplet lower state of the cis configuration or a transition back to the trans state.

Low-power phase conjugation in push–pull azobenzene compounds

Abstract: Push–pull azobenzene compounds were synthesized by the diazocoupling reaction, and low-power phase conjugation of azobenzene-compound-doped poly(methyl methacrylate) films was studied with a He–Ne laser at 632.8 nm. It is shown that this kind of polymer has appreciable third-order optical nonlinearity, with a χ(3) of approximately 10−4 esu in the tail of absorption.

Surface relief structures on azo polymer films

Abstract: All optical fabrication of Surface Relief Grating (SRG) on azobenzene functionalized polymer films is reviewed in this article. The uniqueness of the single step erasable photofabrication of large amplitude surface relief structures on azo polymer films is mainly due to the photoisomerization and photoanisotropic behavior of the azobenzene group. The design and synthesis of several classes of suitable azobenzene functionalized polymers for the SRG formation is presented. Experimental studies are carried out in a systematic manner to understand the chemical and physical intricacies involved in the SRG formation process. Structural requirements and their limitations for the efficient fabrication of SRGs on azo functionalized polymer films are also discussed. Understanding the fundamental mechanism of SRG formation on the azo functionalized polymer films enables us to make use of these structures in a variety of applications.

Mechanism of Optically Inscribed High-Efficiency Diffraction Gratings in Azo Polymer Films

Abstract: A series of amorphous azobenzene-containing polymers were cast as thin films and shown to produce both reversible volume diffraction gratings and high-efficiency surface gratings by laser irradiation at an absorbing wavelength. The latter process involves localized mass transport of the polymer chains to a high degree, as atomic force microscopy reveals surface profile depths near that of the original film thickness. A mechanism for this phenomenon is proposed which involves pressure gradients as a driving force, present due to different photochemical behaviors of the azo chromophores at different regions of the interference pattern. The phase addition of the two beams in the interference pattern leads to regions of high trans-cis-trans isomerization by the absorbing azo groups, bordered by regions of low isomerization. As the geometrical isomerization requires free volume in excess of that available in the cast films, the photochemical reaction in these areas produces a laser-induced internal pressure ab...