Polymer-dispersed Liquid Crystal Reflection Research Articles

Distributed feedback all-organic microlaser based on holographic polymer dispersed liquid crystals

An optically pumped vertically emitting all-organic laser, based on a holographic polymer dispersed liquid crystal reflection grating operating in a distributed feedback configuration, is presented. The used experimental geometry overcomes the main drawbacks characterizing similar systems, allowing virtually infinite operations and absence of damages associated with the high energy of the optical pumping.

Droplet deformation and alignment for high-efficiency polarization-dependent holographic polymer-dispersed liquid-crystal reflection gratings

Droplet deformation and alignment are achieved in holographic polymer-dispersed liquid-crystal reflection gratings by applying an in situ shear during recording. High diffraction efficiency (99%) is obtained for light polarized parallel to the shear, with nearly zero efficiency for perpendicular polarization, and no increase of incoherent scattering. Permanent polarization dependence is related to stress-induced morphology changes of liquid-crystal droplets that are frozen by polymerization. The system is studied by electron microscopy and modeled by anisotropic coupled-wave and scattering theory. The morphology is consistent with the theory of small deformations of liquid droplets in fluid flow. Diffraction efficiency measurements are in agreement with theory incorporating this morphology as well as concomitant orientation and alignment of liquid-crystal molecules.

Holographic polymer dispersed liquid crystal reflection gratings formed by visible light initiated thiol-ene photopolymerization

Visible laser light of wavelengths 442, 488 and 532 nm was used to write holographic reflection gratings with notches into the infra-red spectral region in polymer dispersed liquid crystals (H-PDLC). The gratings were formed by the spatially periodic phase separation of nematic liquid crystal during thiol-ene photopolymerization. An organic titanocene based complex, Rhodamine 6G (Rh6G) and Pyrromethene 597 (Pym) dyes in combination with benzoyl peroxide, were used as initiators. Using visible laser light and a single prism, electrically switchable reflection gratings with notches in the blue, green, yellow, red, and near infra-red (NIR) spectral regions were fabricated using angle tuning. The photophysics of the initiator dyes was studied by absorption and fluorescence spectroscopy. Morphology studies by TEM showed a periodic distribution of discrete nematic droplets of nearly spherical shape. The development of visible photoinitiator systems broadens the range of fabrication wavelengths of dynamic reflection filters using inexpensive visible lasers.

Comprehensive Examination of the Morphology of Holographic Polymer Dispersed Liquid Crystal Reflection Gratings Written in Thiol-ene Polymer Hosts

Comprehensive Examination of the Morphology of Holographic Polymer Dispersed Liquid Crystal Reflection Gratings Written in Thiol-ene Polymer Hosts

Morphology of Holographic Polymer Dispersed Liquid Crystal Reflection Gratings Written in Thiol-ene and Acrylate Polymer Hosts: Part II-The Effect of Diamond Knife Angle and Sectioning Direction in Ultramicrotomy

Morphology of Holographic Polymer Dispersed Liquid Crystal Reflection Gratings Written in Thiol-ene and Acrylate Polymer Hosts: Part II-The Effect of Diamond Knife Angle and Sectioning Direction in Ultramicrotomy

Morphology of Holographic Polymer Dispersed Liquid Crystal Reflection Gratings Written in Thiol-ene and Acrylate Polymer Hosts: Part I-Grating Formation

Morphology of Holographic Polymer Dispersed Liquid Crystal Reflection Gratings Written in Thiol-ene and Acrylate Polymer Hosts: Part I-Grating Formation