arXiv subjects

Lech Sznitko

Publications and source records attributed to Lech Sznitko.

6 recordsLinked to original sources

arXiv2025

Polymer fiber mats provide white and full-color tunable lasing

Random Lasing has become highly advantageous for achieving white laser emission. Utilizing multiple light scattering in disordered media allows for cost-effective and flexible designs, as well as the seamless integration of multiple multicolor gain materials. However, generating light that closely meets the D65 illumination standard remains challenging due to energy transfer between chromophores. To address this issue, effective spatial separation of gain media is required. Here, we present a solution to the problem using hierarchically designed polymer fiber mats with spatially distributed red, green, and blue (RGB) laser dyes to achieve controlled and tunable multicolor and white lasing. While electrospun fibers are well-studied, their use for multicolor random lasing is demonstrated here for the first time. Our results demonstrate outstanding spectral tunability, aligning well with industrial color standards such as sRGB, Adobe RGB, and DCI-P3. The white lasing closely matches D-series white illuminants, including D65, D55, and D75 standards, with coordinate deviations as low as approximately 0.2 to 3%, surpassing previously reported values for organic, hybrid, and inorganic systems. By limiting energy transfer, our approach enables precise lasing control, demonstrating that fiber mats are versatile for next-generation random lasing applications. These findings advance technologies in Li-Fi, laser displays, optical sensors, switches, and modulators, bringing tunable lasers closer to commercialization.

physics.optics↗

arXiv2025

Photothermal tuning of microparticle diffusion anisotropy in nematic lyotropic chromonic liquid crystal

We report a photothermal approach to dynamically tuning the anisotropic diffusion of microparticles suspended in a lyotropic chromonic liquid crystal (LCLC) consisting of a 30 % aqueous solution of Sunset Yellow (SSY). By switching the illumination spectrum between non-absorbing (red) and strongly absorbing (blue) regimes matching the H-aggregate absorption bands of SSY, we demonstrate a significant enhancement in both overall particle mobility and directional diffusion anisotropy (Dx/Dy). While off-resonance illumination yields a standard anisotropy ratio of 3.0, resonant blue-light exposure drives a preferential unbinding along the molecular stacks, elevating the anisotropy ratio to 5.5. This light-dependent diffusion anisotropy offers a straightforward framework for optically controlled microfluidic sorting and active soft matter assembly.

cond-mat.soft↗

arXiv2020

Dye stabilization and wavelength tunability in lasing fibers based on DNA

Lasers based on biological materials are attracting an increasing interest in view of their use in integrated and transient photonics. DNA as optical biopolymer in combination with highly-emissive dyes has been reported to have excellent potential in this respect, however achieving miniaturized lasing systems based on solid-state DNA shaped in different geometries to confine and enhance emission is still a challenge, and physico-chemical mechanisms originating fluorescence enhancement are not fully understood. Herein, a class of wavelength-tunable lasers based on DNA nanofibers is demonstrated, for which optical properties are highly controlled through the system morphology. A synergistic effect is highlighted at the basis of lasing action. Through a quantum chemical investigation, we show that the interaction of DNA with the encapsulated dye leads to hindered twisting and suppressed channels for the non-radiative decay. This is combined with effective waveguiding, optical gain, and tailored mode confinement to promote morphologically-controlled lasing in DNA-based nanofibers. The results establish design rules for the development of bright and tunable nanolasers and optical networks based on DNA nanostructures.

physics.optics↗

arXiv2018

Stacked electrospun polymer nanofiber heterostructures with tailored stimulated emission

We present stacked organic lasing heterostructures made by different species of light-emitting electrospun fibers, each able to provide optical gain in a specific spectral region. A hierarchical architecture is obtained by conformable layers of fibers with disordered two-dimensional organization and three-dimensional compositional heterogeneity. Lasing polymer fibers are superimposed in layers, showing asymmetric optical behavior from the two sides of the organic heterostructure, and tailored and bichromatic stimulated emission depending on the excitation direction. A marginal role of energy acceptor molecules in determining quenching of high-energy donor species is evidenced by luminescence decay time measurements. These findings show that non-woven stacks of light-emitting electrospun fibers doped with different dyes exhibit critically-suppressed F\"orster resonance energy transfer, limited at joints between different fiber species. This leads to obtain hybrid materials with mostly physically-separated acceptors and donors, thus largely preventing donor quenching and making much easier to achieve simultaneous lasing from multiple spectral bands. Coherent backscattering experiments are also performed on the system, suggesting the onset of random lasing features. These new organic lasing systems might find application in microfluidic devices where flexible and bidirectional excitation sources are needed, optical sensors, and nanophotonics.

cond-mat.mtrl-sci↗

arXiv2017

Interplay of Stimulated Emission and Fluorescence Resonance Energy Transfer in Electrospun Light-Emitting Fibers

Concomitant amplified spontaneous emission (ASE) and F\"orster resonance energy transfer (FRET) are investigated in electrospun light-emitting fibers. Upon dye-doping with a proper FRET couple system, free-standing fibrous mats exhibit tunable FRET efficiency and, more importantly, tailorable threshold conditions for stimulated emission. In addition, effective scattering of light is found in the fibrous material by measuring the transport mean free path of photons by coherent backscattering experiments. The interplay of ASE and FRET leads to high control in designing optical properties from electrospun fibers, including the occurrence of simultaneous stimulated emission from both donor and acceptor components. All tunable-optical properties are highly interesting in view of applying electrospun light-emitting materials in lightening, display, and sensing technologies.

cond-mat.mtrl-sci↗

arXiv2014

Physically transient photonics: random vs. distributed feedback lasing based on nanoimprinted DNA

The authors report on a room-temperature nanoimprinted, DNA-based distributed feedback (DFB) laser operating at 605 nm. The laser is made of a pure DNA host matrix doped with gain dyes. At high excitation densities, the emission of the untextured dye-doped DNA films is characterized by a broad emission peak with an overall linewidth of 12 nm and superimposed narrow peaks, characteristic of random lasing. Moreover, direct patterning of the DNA films is demonstrated with a resolution down to 100 nm, enabling the realization of both surface-emitting and edge-emitting DFB lasers with a typical linewidth<0.3 nm. The resulting emission is polarized, with a ratio between the TE- and TM-polarized intensities exceeding 30. In addition, the nanopatterned devices dissolve in water within less than two minutes. These results demonstrate the possibility of realizing various physically transient nanophotonics and laser architectures, including random lasing and nanoimprinted devices, based on natural biopolymers.

cond-mat.mtrl-sci↗