Polymer surface relief structures caused by light-driven diffusion

Abstract

Two amorphous side-chain copolymethacrylates containing 60% azobenzene chromophores (PII, PIV) were irradiated homogeneously with a linear polarized Ar+ ion laser beam at 488 nm. From polarized UV/VIS spectra the maximum of the photoinduced dichroism was calculated (dPII=0.25, dPIV=0.35). No intensity dependence of this values was notified. PIV was irradiated under holographic conditions with a grating period of 30 m. Two types of polarization gratings, circular orthogonal and linear orthogonal ones were inscribed. Using a microscope spectrometer polarized UV/VIS spectra were measured within the grating period with a lateral resolution of about 2 m. The induced local dichroism was measured and the different modulation of the molecular orientation in the recorded gratings was confirmed by this direct experiment. PII was used to monitor the grows up stages of the surface relief grating, starting from the molecular photoorientation until the surface deformation. Parallel t o the online observed diffraction efficiency, the offline surface profile measurements were done by AFM. The details of surface topography and the reversibility of the process are discussed and an interesting possibility of the surface structuring is demonstrated

Light induced processes in thin films of indandione type organic molecules

“…These laser beams were irradiated through one point of the gratings and diffraction patterns were investigated. Experiments on inscribing of the surface relief gratings in azobenzene polymers [19] show that the mass transport may be related to photoorientation of chromophores. Therefore in polymer film chromophores form structures with different orientation order.…”

Polymers films with indandione derivatives as alternatives to azobenzene polymers for optical patterning

“…At extremely high intensity SRGs can be written by thermal effects [9]. But our own experimental findings and results of other studies [10] indicate, that at low light intensities which we use, the driving force has to be related to the light polarisation and hence on photoorientation. It is explained by a thermodynamic theory for optically driven mass transport [11].…”

“…Interference of circular polarised light keeps the intensity constant but a periodic change of the vector direction in plain is generated. The direction of the material driving force is depending on photoorientation and so the transport is more efficient if the force is not only working in one direction [10,11].…”

Stable Lasing in Azobenzene Polyelectrolyte with Polarization Gratings as Distributed Feedback

“…[2b] This supplied the proof‐of‐principle, even though the oligomeric azobenzene‐containing material used shows relatively low photoinduced birefringence, and consequently was not the best choice of material for such an application. However, the polarization gratings could be inscribed in a great number of azobenzene‐containing materials and they usually evolve at the initial stage of holographic inscription, thus not requiring longer exposure times . Thus, this yields the possibility to use other azobenzene‐containing materials for the fabrication of single‐layer laser devices based on polarization gratings.…”