Six novel N,O-coordinated benzochalcogenazole-based boron difluoride complexes (1a,b-3a,b) have been synthesized and spectroscopically characterized. The influence of the chalcogen atom (O, S, Se) in the benzochalcogenazole unit on the photophysical properties was systematically investigated. Although the complexes exhibit negligible fluorescence in solution, they display aggregation-induced emission and intense solid-state luminescence, achieving photoluminescence quantum yields of up to 85% in the crystalline state and 69% in poly(methyl methacrylate) films. The benzoxazole- and benzothiazole-based derivatives exhibit blue amplified spontaneous emission with maxima in the range of 429-455 nm (λex = 337 nm), thresholds as low as 12.4 μJ/cm2, and full widths at half-maximum as narrow as 9.5 nm. These compounds also display both prompt and delayed fluorescence, indicating efficient exciton utilization. The results demonstrate that rational chalcogen substitution effectively modulates the emission behavior, providing valuable design principles for next-generation organic photonic and optoelectronic materials.

Four N,O-coordinated benzochalcogenazolo-based boron difluoride complexes were designed, synthesized, and spectroscopically investigated in solutions, crystalline state, and dye-doped poly(methyl methacrylate) films. The single crystal analysis revealed that oxadiazaborinine dyes adopt planar geometry with multiple intermolecular hydrogen-bonding interactions. The benzoxazole- and benzothiazole-containing dyes exhibit highly intensive photoluminescence in the crystalline state and when dispersed in the inert polymer, accompanied by high-rate constants of radiative deactivation (2.2 × 108 s-1 and 2.7 × 108 s-1, respectively). This results in their amplified spontaneous emission ability with very low thresholds of 11 and 4.7 μJ/cm2, respectively, and very narrow bandwidths with the values of full widths at half maxima of 10 and 6.3 nm. In stark contrast, the benzotellurium-containing analogue shows room temperature phosphorescence with a short phosphorescence lifetime of 9.4 μs, caused by the strong chalcogen heavy-atom effect.

A new series of donor-acceptor benzochalcogenazole-based N,O-coordinated boron difluoride complexes (1a,b-3a,b) has been synthesized for applications in organic solid-state lasers and light-emitting diodes. The effect of the chalcogen atom (O, S, Se) in the benzochalcogenazole core on the photophysical properties was systematically studied. While the compounds show negligible fluorescence in solution, they exhibit pronounced aggregation-induced emission and strong solid-state luminescence, with photoluminescence quantum yields up to 48% in the crystalline state and 56% in poly(methyl methacrylate) films. Benzoxazole- and benzothiazole-based derivatives display amplified spontaneous emission with thresholds as low as 10.1 μJ/cm2, which enables to perform efficient organic solid-state lasers. Meanwhile, benzothiazole- and benzoselenazole-containing compounds exhibit both prompt and efficient delayed fluorescence. OLED devices incorporating these emitters demonstrated efficient energy conversion and bright electroluminescence. Benzothiazole-based complexes 2a and 2b achieved maximum external quantum efficiencies of 9.0% and 16.5%, respectively, with luminance values exceeding 23,000 cd/m2. In contrast, the benzoselenazole analogue 3a, despite a higher delayed fluorescence-to-prompt fluorescence ratio, showed lower device efficiency, highlighting the impact of heteroatom selection on exciton dynamics. These findings establish benzothiazole-containing boron difluoride complexes as promising, thermally stable emitters for high-performance solid-state laser and OLED applications. The results underscore the potential of molecular design and heteroatom engineering to further enhance efficiency and operational stability in organic optoelectronic devices.

The development of efficient UV organic solid-state lasers (OSLs) remains a significant challenge, yet it is crucial for enabling advanced photonic technologies. This study investigates two dispirofluorene-indenofluorene regioisomers, (2,1-a)-DSF(tBu)4-IF (DSFIF-syn) and (1,2-b)-DSF(tBu)4-IF (DSFIF-anti), to elucidate the impact of subtle structural differences on their solid-state photophysical and lasing properties. Through a combination of experimental techniques and theoretical approaches, including comprehensive optical characterization and molecular dynamics simulations, it is demonstrated that DSFIF-syn exhibits significantly reduced intermolecular aggregation compared to DSFIF-anti, resulting in enhanced optical performance in solid-state thin films. Remarkably, amplified spontaneous emission (ASE) is achieved at a record-short wavelength of 365 nm with a low threshold of 4.5 mu J cm-2 (5000 W cm- 2) in a PMMA blend film. Moreover, distributed feedback (DFB) laser devices incorporating a blend film of DSFIF-syn dispersed in polystyrene (PS) enabled lasing at an unprecedentedly short wavelength of 358.5 nm, as well as a low lasing threshold of 0.7 mu J cm- 2 (780 W cm- 2) at 363.3 nm. These results demonstrate that dispirofluorene-indenofluorene derivatives are highly promising UV laser dyes, highlighting isomeric control as a valuable molecular design strategy for advancing high-performance organic lasers.

Three N,O-coordinated benzochalcogenazolo-based boron difluoride complexes have been designed, synthesized, and spectroscopically characterized using their solutions, solid state, and the films of dye-doped polymers. The structural analysis demonstrated that dyes adopt twisted molecular structures with the torsion angle ranging from 24 degrees to 37 degrees, attributed to the steric effect of the cyano group. The obtained compounds exhibit aggregation-induced emission and blue to cyan emission (455-487 nm) in the solid state with a photoluminescence quantum yield ranging from 21% to 85% and a short excited-state lifetime of 0.80-2.27 ns. These characteristics facilitate the amplified spontaneous emission (ASE) with the progressive reduction in the full width at half maximum observed across the series of benzoxazole -> benzothiazole -> benzoselenazole derivatives up to 15 nm, 11 nm, and 8 nm, respectively, and also the low ASE threshold values of 18.7-40.3 mu J cm-2. The successful application of the dyes in the fabrication of organic solid-state lasers results in a laser threshold of 46.1 mu J cm-2, 28.0 mu J cm-2, and 58.6 mu J cm-2 for the devices based on benzoxazole, benzothiazole, and benzoselenazole-based boron difluoride complexes, respectively. Our work opens the pathway for a novel class of heavy atom-containing organic laser dyes, which can be used for both organic optically and electrically pumped lasers.

The intrinsic properties of picosecond (ps) laser pulses with different wavelengths are investigated using a streak camera in the single-shot mode. It is demonstrated, how the detector parameters, such as time range (TR) and width of its entrance slit, affect the accuracy of the measurement of the laser pulse duration. Furthermore, the proper configuration of the streak camera system for ultrafast laser-based plasma diagnostics, such as ps Two-Photon Absorption Laser Induced Fluorescence (ps-TALIF) is described and discussed. As a proofof-concept, ps-TALIF measurements of the effective lifetime (teff) of H atoms in a microwave plasma torch are performed to reveal and quantify the effects of TR and slit width on the shape of the recorded ps-TALIF signals. This research contributes to advancing plasma optical diagnostics with potential applications in aerospace, combustion, and material deposition.

Organic semiconductors lasers (OSLs) do not naturally operate in the Continuous-Wave (CW) regime due to the accumulation of long-lived triplet states. Recently, however, triplet engineering has allowed quasi-CW lasing, notably in BSBCz and its derivatives. An analysis of CW lasing conditions in organic semiconductors that includes the effects of Triplet Absorption, Singlet-Triplet-Annihilation, Triplet-Triplet Annihilation or Reverse Intersystem Crossing is presented. In addition of photophysical parameters, we show the crucial role played by the resonator Q factor in the lasing regime. This work provides a roadmap towards true-CW lasing based on a global approach that encompasses photophysics and optical design.

Les matériaux organiques sont devenus des acteurs incontournables du panorama de l’optoélectronique moderne. Dans de nombreux cas, notamment celui des lasers, l’utilisation de ces matériaux permet d’accéder à des fonctions difficilement atteignables voire inatteignables pour les dispositifs inorganiques.

Evaluating the lasing potential of light-emitting materials has become an important aspect of thin-film laser research. Measurement of Amplified Spontaneous Emission (ASE) thresholds is a widespread technique for this matter, but the question of whether measuring this threshold in energy or power density becomes relevant whenever pump duration and excited state lifetime share the same order of magnitude. By comparing thresholds of a DCM-based organic waveguide with 4 different pump durations, we establish that power density is the most appropriate unit even for pulses shorter than the excited state lifetime by a factor of 5.

Exciton‐polaritons, in which the electronic state of an excited organic molecule and a photonic state are strongly coupled, can form a Bose–Einstein condensate (BEC) at room temperature. However, so far, the reported thresholds of organic polariton BECs under optical excitation are as high as P th = 11–500 μJ cm –2 . One route toward lowering the condensation threshold is to increase the Rabi energy by aligning the molecular transition dipole moments. In this report, it is demonstrated that control of the orientation of a perylene‐based discotic dye, which is able to self‐organize in mesogenic columnar structures, can significantly enhance exciton–photon interaction and polariton relaxation rate in optical cavities. These results show the importance of the molecular orientation for strong light–matter interactions and provide a promising strategy toward the realization of an organic low threshold polariton BEC system and electrically driven organic polariton BEC.

High performance organic semiconductor lasers (OSLs), especially those under current injection, have been sought for decades due to their potentially great applications in fields such as spectroscopy, displays, medical devices, and optical interconnection. The design and fabrication of high-quality resonators is a prerequisite for high performance OSLs. In the case of planar microcavities, the fabrication process of top distributed Bragg reflectors (DBRs) usually requires electron beam evaporation or manual lamination on top of organic thin-film layers, which can lead to issues including degradation of the organic materials, large-scale non-uniformity, and difficulties for current injection. Here, we report a non-destructive way of fabricating a top DBR by thermal evaporation. The top DBR based on thermally evaporated alternative TeOx/LiF stacks shows low morphological roughness, high process tolerance, and high reflectivity. Moreover, the deposition process causes negligible damage to the organic thin-film layers underneath. With the combination of a conventional e-beam evaporated bottom DBR, a high performance planar microcavity OSL with a low threshold of 1.7 μJ cm−2, an emission linewidth of 0.24 nm, and an angular divergence of <3° has been achieved under nitrogen laser pumping. Similar performance, with a high Gaussian beam quality comparable with that of an ideal diffraction-limited beam, was also obtained under diode pumping, showing the potential of this technique for building compact and cost-effective organic lasers with good beam quality. Our result will open a promising route for future high performance microcavity optoelectronic devices, especially for laser devices under current injection.

We report on the realization of a narrow-linewidth diode-pumped solution-processed solid-sate vertically emitting surface organic laser (VECSOL) using a Volume Bragg Grating as an output coupler. The diode pumped VECSOL used a commercial dye molecule (DCM) embedded in a polymer matrix leading to a laser emission at 610 nm. The ultimate linewidth achievable under that configuration as well as the broadening mechanisms have been investigated under different pumping conditions. An optimal laser linewidth of 40 MHz has been achieved for pump pulse duration of 50 ns.

High-power light-emitting diodes (LEDs) today are twice as powerful as four years ago while meantime their price has been divided by 4 making them promising sources for laser pumping. However, their irradiance still falls short by one order of magnitude of what is needed to efficiently pump solid-state lasers. We demonstrate that an LED-pumped Ce:YAG luminescent concentrator (LC) can increase the irradiance of blue LEDs by a factor of 10, with an optical efficiency of 25%, making them much more suitable to pump solid-state lasers. In our demonstration, we used 100 Hz pulsed LEDs emitting 190 W/cm(2) at 430 nm to illuminate a Ce:YAG LC, leading to an output irradiance of 1830 W/cm(2). The LC is used to pump a Nd:YVO4 laser producing 360 mu J at 1064 nm, corresponding to an optical efficiency of 2.2% with respect to the LC. LED-pumped luminescent concentrators pave the way for high-power, low-cost, solid-state lasers. (C) 2016 Optical Society of America