Two‐Photon Laser‐Written Photoalignment Layers for Patterning Liquid Crystalline Conjugated Polymer Orientation

Abstract

Systematic tuning of chemical and physical structure allows fine control over desired electronic and optical properties, including those of conjugated polymer semiconductors. In the case of physical structure, orientation via liquid crystalline alignment allows access to fundamental optical anisotropies and the associated refractive index modification offers great potential for fabrication of photonic structures. In this paper, photoalignment is used to orient the liquid crystalline conjugated polymer poly(9,9‐dioctylfluorene‐co‐benzothiadiazole) (F8BT), specifically involving two‐photon infrared laser writing of patterns in an azobenzene sulphonic dye (SD1). These patterns are transferred into the overlying film by thermotropic orientation in the nematic melt, then frozen in place by quenching to a room temperature nematic glass. Optimization of laser power and scan speed allows features with linewidths ≤ 1 µm. Photoluminescence (PL) peak anisotropy values reach PLII/PL⊥ = 13 for laser writing, compared with PLII/PL⊥ = 9 for polarized ultraviolet light emitting diode exposure of the same SD1 layer. These two approaches also result in different film microstructures; evidenced by characteristic changes in PL spectra. The anisotropic PL spectra provide information on emissive excited states that complements previous studies on non‐oriented F8BT and related copolymers, also suggesting two emissive states.

Efficient Anisotropic Polariton Lasing Using Molecular Conformation and Orientation in Organic Microcavities

“…In addition, it is anticipated that a further increase in the PLQY of PFO through the use of a lower fraction of β-phase [44] combined with the use of additional DBR layers should allow a further reduction in threshold. Spatial patterning of the SD1 alignment layer using either a photomask [59] or direct two-photon laser writing [60] represents an additional exciting avenue that may allow further improvement in the performance of polariton lasers through in-plane confinement of polaritons and, additionally, offers the opportunity to study topologic phenomena [61] without a need to pattern the cavity mirrors.…”

Smart Nematic Liquid Crystal Polymers for Micromachining Advances

“…The intensity of the current applied has a great influence on how the mesogens will rotate allowing control of the degree of orientation. The addition of a dopant such as an azobenzene [ 34 , 35 ], as shown in Figure 2 D, offers another way to control LC alignment with polarized UV light. The azobenzene molecules will follow the light polarization direction and the LC molecules will be led in the same direction making them reconfigurable ( Figure 2 D).…”

Optical Logic Operation Encryption on ZnTe Flake

“…Generally, photoluminescence (PL) can be efficient for encryption due to its fast readability and facile design. [4,13,[19][20][21] In recent years, many PL materials such as quantum dots, [19,22] upconverting nanoparticles, [23] perovskites, [6,24] and organic dyes [5,25] were employed for information encryption. However, the traditional optical materials usually exhibit unsatisfied PL properties such as few peaks and uncontrollability, limiting the by a 532-nm laser, two emission bands required for encryption are observed, with peaks at 547 nm and 680 nm, respectively (Figure 1d).…”