Electrically switchable and thermally erasable biphotonic holographic gratings in dye-doped liquid crystal films

Lee, C.-R.; Mo, Ting; Cheng, Kuo-Hsing; Fu, Tingting; Fuh, Andy Ying–Guey

doi:10.1063/1.1629374

Cited by 55 publications

(41 citation statements)

References 11 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…SEM and AFM were used to identify smooth layers of adsorbed molecules on the surfaces following exposures that caused the reorientation of the directors perpendicular to the direction of polarization and layers with well-oriented ripples upon exposures that caused alignment toward the direction of polarization [42,48]. The adsorbed layer consists of MR molecules with their long axes perpendicular to the ripples.…”

Section: Bulk-mediated Photo-isomerization and Adsorption Effectsmentioning

confidence: 99%

Photo-Alignment Technology

Lin

2014

Topics in Applied Physics

View full text Add to dashboard Cite

LCDs are used in many everyday devices, including mobile phones, notebook computers and wide screen televisions. A typical LCD is composed of two glass substrates between which is a gap that is filled with LC. The arrangement of the LC is controlled by the boundary condition of an alignment film. A long-range orientational interaction causes the preferable alignment of a LC by the surface boundary to extend into the LC bulk. The alignment layer is typically rubbed with a special cloth to induce a unidirectional alignment of the LC. In the first devices based on twisted LCs, these LCs were aligned only by rubbing transparent electrodes. The rubbing technique became much more reliable when the glass substrate was covered with a rubbed polymer layer. The rubbing of polymers is a very simple technique and it is now extensively utilized in both small scientific laboratories and large LCD factories.Despite the extensive use of rubbing in LCD manufacturing, it has some serious shortcomings that arise from the contact involved in rubbing. These critically affect the production of the most recent generation of LCDs and miniature LC photonic devices. First, rotational rubbing for the polymer surface causes the accumulation of static charges and the formation of fine dust particles. The accumulation of static electricity may destroy the transistors or diodes in the LCD. The second shortcoming is the effect of decreasing in manufacturing yield. Rubbing for large and high-resolution active matrix LCDs (AMLCDs) involve additional difficulties that are associated with the precise control of the rubbing characteristics. Other problems are the difficulty of producing local structures with the required LC director alignment in the selected areas of the device. Finally, this method cannot be used to align LCs in closed volumes.For all of the above reasons, new alignment solutions and approaches are sought. There are some alternative methods of rubbing include laser writing, micro-rubbing, ion beam irradiation and photoalignment. Of these methods, the

show abstract

Section: Bulk-mediated Photo-isomerization and Adsorption Effectsmentioning

confidence: 99%

Photo-Alignment Technology

Lin

2014

Topics in Applied Physics

View full text Add to dashboard Cite

show abstract

“…When ADDLC cells are exposed to certain wavelengths, azo-dye molecules on a surface diffuse, adsorb, and desorb sequentially because of photoisomerization. [1][2][3][4][5] This causes LC-structure reorientation by excited dye molecules. In related studies, the optical characteristics of ADDLC photoexcitation have been obtained on the basis of pump-probe twistnematic experiments.…”

Section: Two Novel Approaches Enable Better Insights Into Liquid-crysmentioning

confidence: 99%

Dynamics of azo-dye-doped liquid crystals

Lo¹

2009

SPIE Newsroom

View full text Add to dashboard Cite

Two novel approaches enable better insights into liquid-crystal photoalignment.Because of their potential importance for photoalignment, azodye-doped liquid crystals (ADDLCs) have been studied extensively over the past decade. Photoalignment of liquid-crystal (LC) molecules can avoid unnecessary contamination due to mechanical rubbing. When ADDLC cells are exposed to certain wavelengths, azo-dye molecules on a surface diffuse, adsorb, and desorb sequentially because of photoisomerization. [1][2][3][4][5] This causes LC-structure reorientation by excited dye molecules. In related studies, the optical characteristics of ADDLC photoexcitation have been obtained on the basis of pump-probe twistnematic experiments. 1, 2 To better understand the transient as well as the permanent behavior of ADDLCs, here we present two novel approaches to observe the reorientation of LC molecules on short 5 and long timescales, 6 respectively.The dye-adsorbed layer is formed during photoalignment. The dye molecules can interact with the surrounding LC molecules through intermolecular forces. As a result, the LC's director (i.e., the LC structure's preferred direction) is reoriented perpendicular to the pump field. 7 After irradiation of the sample for a sufficiently long period, a ripple structure is generated parallel to the pump field. 7 To explore the structural variation of the dye-adsorbed layer, we channeled unpolarized light into a traditional pump-probe twist-nematic experiment, (which is generally used for observing light scattering during formation of the dye-adsorbed layer). The transmitted probe light was scattered during photoexcitation because of the dye's adsorption. Because the ripple structure is formed gradually, it is regular, thus enhancing the dye's surface anchoring (see Figure 1). At the same time, Rayleigh scattering from isolated (or separated) dye-adsorbed grains changes to Mie scattering since the regular ripple structure has a similar spatial scale as the wavelength of the incident light. The increase in transmission intensity is more centralized for Mie than for Rayleigh scattering in the presence of the regular ripple structure. 8 After the ripple structure has formed, the dye molecules' adsorption increases the depth of the grooves, which in turn enhances the surface-anchoring coefficient. The Mie scattering does not vary significantly because the spacing of the ripple structure remains the same in the optical view. Our experimental results verify that the formation of the ripple structure correlates with light scattering induced by adsorption of dye molecules on the surface.Attenuated total-reflection (ATR) measurements are highly sensitive to variations in the dielectric constants close to the surface (approximately 100nm from the surface in LC systems) within the depth of the evanescent wave, which is not affected by the elastic continuum. 9 Our pumped-ATR experiments result in improved measurements compared to the traditional ATR approach. We channeled green pump light-accompanied by a red probe beam...

show abstract

“…Azo dye doped nematic liquid crystals have been actively investigated due to their promising applications in display technology, optical storage, optical limiting and nonlinear optical devices [1][2][3][4]. Disperse Red 1 (DR1) doped nematic liquid crystals have been regarded as one of the most potential materials for application in transient holographic display because of the fast response time of several milliseconds and no need for external electric field [5][6][7].…”

Section: Introductionmentioning

confidence: 99%

Diffraction efficiency enhancement of transient holographic gratings in nematic liquid crystals doped with Disperse Red 1

Li¹,

Wang²

2017

Proceedings of the 2017 2nd International Conference on Automation, Mechanical Control and Computational Engineering (AMCCE 201

View full text Add to dashboard Cite

Abstract. The diffraction properties of transient holographic gratings recorded by two 532 nm laser beams were investigated in nematic liquid crystals doped with Disperse Red 1. A nearly 30-fold enhancement of the first-order diffraction efficiency as a function of heating time was obtained when the sample temperature was close to the clearing point in the nematic phase. A peak shift of diffraction efficiency with the increase of recording light intensity was observed, which was attributed to laser induced photochemical nematic-isotropic phase transition.

show abstract

Electrically switchable and thermally erasable biphotonic holographic gratings in dye-doped liquid crystal films

Cited by 55 publications

References 11 publications

Photo-Alignment Technology

Photo-Alignment Technology

Dynamics of azo-dye-doped liquid crystals

Diffraction efficiency enhancement of transient holographic gratings in nematic liquid crystals doped with Disperse Red 1

Contact Info

Product

Resources

About