Conference Agenda

Second-order nonlinear optical effects - observed only in non-centrosymmetric systems - are utilised in applications including frequency conversion, electro-optic modulation, spontaneous parametric down-conversion, and quantum light generation. Conventional inorganic crystals exhibit high nonlinear coefficients and good optical transparency but often present challenging phase-matching conditions, while organic nonlinear optical materials can show larger coefficients but often suffer from optical absorption and reduced stability. Ferroelectric nematic liquid crystals (FNLCs), which exhibit long-range polar order within a fluid nematic phase, provide an alternative platform for nonlinear optics.

We report the nonlinear optical response of three commercially available, room-temperature FNLCs using second harmonic generation (SHG) measurements over excitation wavelengths from 1100 nm to 1550 nm. Thickness-dependent SHG measurements using wedge cells enable extraction of the dominant second-order nonlinear coefficient, with measured values ranging from approximately 6 to 18.5 pm/V, comparing favourably with RM734 values. Wavelength-dependent SHG measurements show a strong nonlinear response across the full spectral range for all three materials.

Under high fluence excitation, a weaker nonlinear signal is observed at one-third of the excitation wavelength, consistent with a third-order nonlinear response exhibiting cubic power dependence. These results establish room-temperature FNLCs as promising addition to nonlinear optical materials for broadband and tunable photonic applications.

A simple, easy-to-operate, yet adequate model for temporal short-pulse and CW simulations of OLED light-emission characteristics under high voltage operation (20-120 V) is presented. It allows quick comparison of OLED performances for varying organic light-emitting materials. The new theory is “voltage driven”, rather than “current driven”, and formulated in terms of simple concepts. Several applications are given, including estimations of laser thresholds and modulation performances.

High-power lasers operating beyond 2000 nm are key components of advanced systems, including tracking technologies and chemical sensors. To enhance laser performance and expand their applications, novel materials are a primary focus of current research.

We present a study of Ho3+-doped pyrochlore phosphors (Ho0.03Y0.97)2B2O7 (B=Ti, Zr). The phosphors were prepared by the sol-gel approach. We investigated the effect of the chemical composition and the nanocrystals’ morphology on the optical properties with a specific focus on the luminescence at 2100 and 2900 nm. The studied compounds exhibited a strong phosphorescence at 2200 nm with a decay time exceeding 4.3 ms. The decay times recorded for the emission at 2900 nm did not exceed 0.35 ms.

These pyrochlores represent a promising alternative to common silica or chalcogenide glasses, enabling the development of next-generation solid-state lasers operating at 2100 and 2900 nm.

Inkjet 3D printing enables dot-by-dot control of printed objects internal composition, which allows unique solution for fabrication of optical elements with gradient refractive index (GRIN). However, progress in 3D-printed GRIN devices has been constrained by the limited availability of inks with tunable refractive indices (RI). We evaluated three aliphatic thiols with varying molar mass as high RI additives to a UV-curable inkjet resin, producing a series of formulations with controlled RI. Structure–property relationships were established, linking additive structure and loading to curing behavior, optical performance, and jetting characteristics of developed resins. Cured polymer films showed total transmittance >89% across the visible spectrum above 435 nm. The maximum RI increase relative to the unmodified resin was ΔRI = 0.07. Printability was evaluated using Fujifilm Dimatix system:for each additive, the highest-RI formulation produced stable, satellite-free droplets. Using industrial printer, a mono material lens as well as a block with GRIN composition has been printed. These results provide a practical framework for designing UV-curable inkjet resins with tunable RI for 3D printing of GRIN optical components.

Energy-efficient photodetectors have become essential in modern technology and play a key role in the development of next-generation optoelectronic and photonic devices. In this context, self-powered photoelectrochemical (PEC) photodetectors offer a promising alternative to conventional solid-state systems, which often involve complex fabrication processes and high costs. By contrast, PEC devices operate at a solid (semiconductor)–liquid (electrolyte) interface, enabling simpler fabrication and more cost-effective implementation.

In this work, we successfully exfoliated single-crystal Sb₂TeSe₂, which has attracted significant interest owing to its compositional flexibility, high carrier mobility, and tunable optical absorption and carrier dynamics, into a few-layer material and used it for a self-powered PEC-based photodetector. The Sb₂TeSe₂-based PEC device shows remarkable responsivity and detectivity of 85.1 µA W⁻¹ and 1.8 × 10⁸ cm·Hz¹ᐟ²·W⁻¹, respectively, along with an ultrafast sub-second response time, confirming efficient carrier generation and interfacial charge transfer.

Our results clearly demonstrate repeatable device performance over a wavelength range of 350 nm to 650 nm. Above all, the device exhibits self-powered capability due to band bending within the material. We believe that this novel PEC photodetector, consisting of few-layer Sb₂TeSe₂ nanosheets with broadband optical activity and efficient self-powered performance, can pave the way for future high-performance optoelectronic devices.

Femtosecond laser micromachining enables localized and precise modification of transparent materials, allowing the fabrication of complex surface structures below the diffraction limit. Here, we present two optical resonator concepts for thin-film organic lasers realized via direct femtosecond laser writing: laser-induced periodic surface structures (LIPSS) and twisted Moiré superlattices. LIPSS gratings are formed on glass substrates under precisely tailored micromachining conditions and exhibit self-organized nanoscale ripples with periodicities suitable for first-order distributed feedback resonators in the visible spectral range. Twisted Moiré lattices are fabricated by overlaying two triangular lattices with a precisely controlled twist angle, producing large-area, high-order, two-dimensional feedback structures. A thermally evaporated thin-film Alq3:DCM organic layer serves as the gain medium on these micromachined substrates to probe resonator properties. Our experimental results demonstrate readily achievable lasing in these laser-inscribed resonators, with lasing properties finely tunable via micromachining parameters, including emission directionality and lasing threshold.