X. L. Jiang

Polarization dependent recordings of surface relief gratings on azobenzene containing polymer films

Experimental studies on the recording of surface relief gratings on azobenzene containing polymer films using laser beams with different polarizations were carried out. The results indicate that the localized variations of light intensity and alternation of the resultant electric field polarization in the film are essential to the formation of the surface relief gratings.

Unusual polarization dependent optical erasure of surface relief gratings on azobenzene polymer films

Direct formation of surface relief gratings at modest intensities on azobenzene polymers has recently been accomplished. Unusual optical erasure of these surface relief gratings was observed. It is found that the optical erasure is dependent on the polarization state of the erasing beam as well as that of the recording beams used to form the gratings. Thus, gratings when formed memorize the polarization states which created them and influence their erasure behaviors accordingly. Direct transfer of patterns by photoprinting through a phase mask has been achieved.

Epoxy matrix for solid-state dye laser applications

The preparation and performance of an epoxy-based matrix impregnated with Pyrromethene 580 for solid-state dye laser applications are discussed. The matrix proved to be stable and efficient as a laser medium when pumped by a frequency-doubled, Q-switched Nd:YAG laser with a 10-ns pulse width. Stability measurements were performed on a 1-mm-thick epoxy sample, doped with Pyrromethene 580 at a concentration of 4 x 10(-3) M. When the sample was pumped at millijoule energy levels, the stability was measured to be ~55,000 pulses from a single spot on the sample before the power dropped by a factor of half.

Photoassisted poling induced second harmonic generation with in‐plane anisotropy in azobenzene containing polymer films

Photoassisted poling of azobenzene containing polymer films at room temperature using polarized Ar+ laser beam as pump light was studied. Irradiating the films with p‐polarized pump light at an incident angle to the normal during the poling process, second harmonic generation with in‐plane anisotropy could be induced. Second order nonlinear optical coefficient, d33, of the poled sample was measured to be 20 pm/V. The second harmonic generation properties induced by photoassisted poling and thermal assisted poling were compared.

Second-order nonlinear optical properties of a photocrosslinkable epoxy-based polymer

The synthesis and characterization of a novel epoxy-based photocrosslinkable nonlinear optical (NLO) polymer exhibiting enhanced thermal stability is reported. The synthesized polymers show spectroscopic properties (NMR, IR, UV) in accordance with the proposed structures. A glass transition temperature (T g ) of 112°C and a thermal degradation temperature (T d ) of 310°C were recorded. The poled polymer film exhibits stable second-order nonlinear optical activity (d 33 = 19.5 pm/V) over a period of 500 h as characterized by the temporal response of the second harmonic signal at room temperature.

Stable highly transparent nonlinear optical polymer for laser frequency doubling

Abstract Channel waveguides of a polymer with nonlinear optical properties and transparency down to 400 nm were fabricated to be used for laser frequency doubling. The polymer was corona poled to induce orientation of the nonlinear chromophores, resulting in a stable poled polymer. End-fire coupling was used to couple the fundamental beam into the polymer channel waveguide. Green light was observed in the form of Cerenkov radiation using a Q -switched Nd-YAG laser lasing at 1064 nm as the fundamental beam. The total efficiency of the second harmonic conversion was 1.4 × 10 −3 %/W.

Photofabrication of surface relief gratings on azobenzene polymer films

Surface relief gratings were photofabricated on various polymer films containing azobenzene groups in the side chain or in the main chain. Formation of the surface relief gratings on the polymer was very sensitive to the polymer structures. The surface gratings were produced on the polymers containing photoisomerizable azobenzene groups. Recording of the gratings was strongly dependent on the polarization of the beams. The localized variations of magnitude and polarization of the resultant electric field in the film are essential to the formation of the surface relief gratings. Large surface modulation (greater than 6000 angstrom) and high diffraction efficiency (greater than 40% into each of plus or minus 1 order) were obtained under optimal recording conditions. The diffraction efficiency of the surface relief grating was dependent only on the total light energy incident on the film. The surface pattern resulting from straight edge diffraction mapped the negative first derivative of the intensity distribution. Fabrication of various multiple gratings on the same spot of the polymer films were demonstrated. Fourier blazed gratings were also fabricated. The resulting surface pattern was a simple superposition of all the interfering recording waves.

Design of new polydiacetylenes as self assembling second order nonlinear optical polymers

A series of diacetylenic monomers containing a polarizable aromatic substituent at one side and a flexible sidegroup with hydrogen bonding groups at the other side are reported. BPOD, 3-BPOD and NPOD are metallic red as polymerized and highly soluble in chloroform, phenol and trifluoroacetic acid. They undergo a dramatic color transition from red(h,-510 nm) to purple(h,-590 nm) upon the addition of a nonsolvent such as hexane. Films with excellent optical quality can be prepared by spin coating or casting the solutions of these polymers. These polydiacetylenes self assemble in an acentric stable polar organization without recourse to poling. Second harmonic signals are observed from the monomer crystals of these materials as well as the bulk polymers.

Nonlinear Optical Polymers Derived from Organic/Inorganic Composites

Abstract : A general approach to the development of multicomponent multifunctional stable NLO materials based on sol-gel reactions has been discussed. We have shown that these second order NLO organic/inorganic composites exhibit excellent room temperature stability of the second order optical nonlinearity. The final structure is an orientationally ordered organic/ inorganic network. After an initial decay, excellent long term stability at elevated temperatures, ranged from 100 to 120 deg C is observed for a number of different systems. The second order optical nonlinearities are reasonably large for radical device considerations. Sol-gel, Nonlinear optical polymers, Organic/ inorganic composites.

Photofabrication of surface relief gratings using post functionalized azo polymers

A series of azobenzene funtionalized polymers has been synthesized by post polymerization azo coupling reaction. Photo-fabrication of surface relief gratings were studied on the polymer films. Epoxy based azo polymers were prepared by post azo coupling reaction to form polymers containing donor-acceptor type azo chromophores. The azo chromophores were designed to contain ionizable groups to impart self-assembling and photoprocessing capabilities to the polymers. The polymers containing 4-(4-(carboxylic acid)phenylazo)aniline chromophores can be directly photofabricated to form surface relief gratings with large surface modulations. Charge interactions had a strong influence on the details of the writing process. A new soluble polydiacetylene, post-functionalized with azobenzene groups was also prepared. Large amplitude surface gratings could be fabricated on this polydiacetylene film as well.