Dye-doped Polymer Research Articles

Spatio-spectral mapping of a microbottle laser

The spatio-spectral mapping of a whispering gallery mode microbottle laser has been presented. The dye-doped polymer coated microbottle resonator (MBR) of diameter 237μm, fabricated by soften and compress technique was locally excited by a narrow pump-stripe and the lasing modes having a quality factor of 1.5×104 with 0.33 nm free spectral range were observed. The localized and delocalized lasing modes were investigated throughout the resonator axis. Unlike the tapered fiber excitation geometry, the lasing modes have been read-out by scanning a collection fiber in the imaging plane allowing the spectral mapping over the entire resonator length. When pumped at the neck of the MBR, the spatial correlations of the spatio-spectral maps reveal the excitation of modes in the unpumped regions of the resonator.

Self-Enhanced Electrochemiluminesence of Dye-Doped Polymer Dots for Coreactant-Free Visualized Detection of Iodide Ions.

The monitoring of radioactive iodide levels is of great significance in environmental science and cancer radiotherapy. In this work, a high-throughput, radiation-resistant, and visualized electrochemiluminescence (ECL) strategy was developed for detection of iodide ions. Herein, the hydrophobic ruthenium derivative (Ru(bpy)3[B(C6F5)4]2) (bpy = bipyridyl) was doped in tertiary amine-coupled polymer dots (N-PFO Pdots) to synthesize self-enhanced Pdots (Ru@Pdots), which showed extremely high ECL intensity in absence of coreactant. Due to the efficient ECL resonance energy transfer between Ru(bpy)3[B(C6F5)4]2 and N-PFO, the Ru@Pdots exhibited 18 times higher ECL intensity compared with bare N-PFO Pdots. Besides, Ru@Pdots also showed 220-times higher ECL intensity compared with Ru(bpy)3[B(C6F5)4]2 doped coreactant-dependent Pdots (Ru@PFO Pdots). Using Ru@Pdots as ECL emitters, an ECL imaging array was designed for iodide ion detection, which exhibited a detection range of 0.8 nM-4 μM and a limit of detection of 0.1 nM. In this strategy, iodide ions were oxidized as iodide free radicals on the surface of the electrode, which could further consume the nitrogen radical of Ru@Pdots and effectively quench the ECL signal. This method also showed good specificity, radiation-resistant performance, and accuracy in actual seawater sample testing, which indicated its value in marine environmental monitoring, nuclear security, and cancer radiotherapy.

Spectroscopic study of wemple-didomenico empirical formula and taucs model to determine the optical band gap of dye-doped polymer based on chitosan: Common poppy dye as a novel approach to reduce the optical band gap of biopolymer

This study investigates the effect of a natural dye extracted from common poppy (Papaver rhoeas) waste flowers on the optical properties of chitosan (CS) films. The extraction of natural dyes from waste flowers can be considered a new field for research in green chemistry. CS films are flexible and biodegradable but have low optical activity and band gap, limiting their applications in optical devices. The doped CS polymer with different concentrations of Papaver rhoeas dye exhibited enhanced optical properties. Also, 30 % glycerol was added as a plasticizer to omit film brittleness. The FTIR examinations is helpful to propose a mechanism that explains the interaction of the dye with the host polymer. The UV–vis spectroscopic examination establish that the optical characteristics of the films can be modified by adjusting the dye concentration. Furthermore, optical absorption properties are described using the Tauc non-direct transition model, revealing an approximate optical band gap of 1.64 eV. This band gap defines the energy required for electron transitions, elucidating the material’s electronic characteristics. The extinction coefficient (k) and refractive index (n) of the CS-doped films’ shows a dispersion behavior at visible regions of EM radiation. The Wemple-DiDomenico single oscillator model was used to investigate the n dispersion and determine the oscillator energy equivalent to the optical band gap. Additionally, calculations have been performed on optical dielectric properties and optical conductivity. The Urbach energy was measured and used to detect the structure of the films. The findings underscore the potential applications of these natural dye-doped CS films in eco-friendly materials and optical devices.

Electric field induced phototransport in dye-doped semiconducting polymer

Electric field induced phototransport in dye-doped semiconducting polymer

A Full-Scale Analysis of Absorption Edges in Dye-Doped Nonlinear Optical Polymers.

A full-scale analysis of the absorption edges by modified Tauc-Lorentz models is essential in determining the optical bandgap and Urbach energy of semiconductors, transparent conductors, ionic compounds, and dielectric materials. This technique has not yet been applied to analyzing organic nonlinear optical (NLO) materials. This problem is tackled by preparing high-quality films of guest-host NLO polymers with a wide thickness range from sub-micron to 200 microns, allowing accurate measurement of full-spectral absorption coefficients of NLO materials over four orders of magnitude by the UV-VIS-NIR spectroscopy. The Tauc model and a new Monolog-Lorentz model are used to study the optical absorption edge of guest-host NLO polymers containing various push-pull chromophores and the dependence of optical bandgap and Urbach edge on the structure and composition of materials is analyzed. The results reveal the critical transition of the Urbach exponential tail to a low energy tail that overlaps with vibrational overtones of materials at the telecom wavelengths. Determining the fundamental absorption region of organic NLO films in this study provides quantitative insight into the research to harness the resonance-enhanced nonlinear coefficients of materials by operating at the wavelengths near the band edge with the control of optical loss.

Facile Z-scan determination of nonlinear refractive index and absorption coefficient of dye-doped polymer film

Facile Z-scan determination of nonlinear refractive index and absorption coefficient of dye-doped polymer film

Tuned the refractive index and absorption edge for Fuchsin basic dye-doped (PVA-PVP-PEG) films: Linear and nonlinear optical characterization for blocking intense laser power

The current investigation focused on creating dye-doped polymer blend films using a solution cast method with a composition of 60%PVA-30%PVP-10%PEG. These films displayed altered refractive index and absorption edge properties. Various characterization techniques, including XRD, FTIR, UV–vis spectroscopy, and optical limiting effects, were utilized to analyze the structural and optical features of the dyed films. The doped samples showed noticeable changes in the structural properties of the polymer matrix blend, as evident from their XRD and FTIR patterns. Incorporating FB dye into the blend resulted in absorption spectra appearing in multiple bands between 295 and 560 nm. For 532.8 nm He-Ne lasers, the FB/(PVA-PVP-PEG) blend was found to be ideal due to its transmittance CUT-OFF within the 200–600 nm wavelength range. The addition of FB dye had a significant impact on the optical characteristics of the polymer blend, leading to a shift in the absorption edge towards lower photon energy levels. The presence of FB dye was also observed to influence the refractive index (n) of the host polymer, indicating its potential for adjusting optical properties. Detailed investigations into the bandgap revealed a reduction in the bandgap of the host polymer due to the presence of the dye. Electronic transitions were further examined through the εi(ω) parameter during the bandgap analysis, confirming the role of the dye in altering the optical bandgap. Overall, the synthesized FB/(PVA-PVP-PEG) polymeric films hold promise for various optoelectronic applications, including lasers, optical filters, communication devices, LEDs, and optical switches.

Low-power Z-scan study of nonlinear refractive index and absorption coefficient of acid blue 129 dye-doped polymer thin film

Low-power Z-scan study of nonlinear refractive index and absorption coefficient of acid blue 129 dye-doped polymer thin film

Aggregation/Crystallization-Induced Emission in Naphthyridine-Based Carbazolyl-Modified Donor-Acceptor Boron Dyes Tunable by Fluorine Atoms.

Four donor-acceptor boron difluoride complexes based on the carbazole electron donor and the [1,3,5,2]oxadiazaborinino[3,4-a][1,8]naphthyridine acceptor were designed, synthesized, and systematically spectroscopically investigated in solutions, in dye-doped polymer films, and in the solid states. The dyes exhibit an intense blue to red solid-state emission with photoluminescence quantum yields of up to 59 % in pure dye samples and 86 % in poly(methyl methacrylate) films. All boron complexes show aggregation-induced emission and reversible mechanofluorochromism. The optical properties of these dyes and their solid state luminescence can be tuned by substitution pattern, i. e., the substituents at the naphthyridine unit. Exchange of CH3 - for CF3 -groups does not only increase the intramolecular charge transfer character, but also provides a crystallization-induced emission enhancement.

Blue micro-lasing from dye-doped hollow polymer optical fiber with an Ag nanoparticle-doped microring

We report the modified and improved whispering gallery mode laser emission from a hollow polymer optical fiber doped with 1,4-Bis(2-methyl styryl) benzene (Bis-MSB), a high-quantum yield dye with a blue emission, with the introduction of an Ag nanoparticle-doped microring. In the presence of the Ag-doped microring, the laser emission was enhanced, and a reduction in the laser threshold from 40 to 15 µJ was attained, along with a small redshift in the emission spectrum. The quality factor of the microring embedded hollow polymer optical fiber was found to be 1.3×103. Moreover, the introduction of an Ag-doped microring inside the hollow polymer optical fiber helps enhance certain lasing modes. The observations open the way for the development of low-threshold polymer optical fiber lasers in the blue region.

Photothermal heterodyne imaging of micron-sized objects.

Micron-sized dye-doped polymer beads were imaged using transmitted/reflected light microscopy and photothermal heterodyne imaging (PHI) measurements. The transmitted/reflected light images show distinct ring patterns that are attributed to diffraction effects and/or internal reflections within the beads. In the PHI experiments pump laser induced heating changes the refractive index and size of the bead, which causes changes in the diffraction pattern and internal reflections. This creates an analogous ring pattern in the PHI images. The ring pattern disappears in both the reflected light and PHI experiments when an incoherent light source is used as a probe. When the beads are imaged in an organic medium heat transfer changes the refractive index of the environment, and gives rise to a ring pattern external to the beads in the PHI images. This causes the beads to appear larger than their physical dimensions in PHI experiments. This external signal does not appear when the beads are imaged in air because the refractive index changes in air are very small.

Colorimetric and absorbance based sensor for sulfide and bicarbonate ions by dye doped polymer composite

We have developed a simple, rapid and cost-effective Dual-channel “colorimetric and absorbance” sensor using polyvinylpyrrolidone (PVP) capped Rhodamine6g (Rh6G) dye composite. Dye-doped polymer composite probe (PVPRH) exhibit intense, narrow absorption properties and long-term stability than the bare Rh6G. The probe’s colorimetric relationship with pH was demonstrated by absorption titration. The PVPRH provides a sensitive dual channel method for the determination of sulfide and bicarbonate with colorimetric response and absorption quenching. The synthesized probe, as a two-faced, exhibited remarkable colorimetric responses from orange to pale yellow in the presence of S2- and orange to soft pink in the presence of HCO3- ion, which can be observed by the naked eye also. Under optimal conditions, the relative absorption intensity decreases with increasing ion concentration of sulfide and bicarbonate ions. This trend is observed within the probe solution concentration range of 5 mM to 50 mM. The Dye-doped polymer composite probe is easy, cost effective, rapid, and has real time detection capability for sulfide and bicarbonate ions. The composite probe is stable and optically modified and can be successfully used for detections of S2- and HCO3- ions as strip senor.

2D tunable all-solid-state random laser in the visible

A two-dimensional (2D) solid-state random laser emitting in the visible is demonstrated, in which optical feedback is provided by a controlled disordered arrangement of air-holes in a dye-doped polymer film. We find an optimal scatterer density for which threshold is minimum and scattering is the strongest. We show that the laser emission can be red-shifted by either decreasing scatterer density or increasing pump area. We show that spatial coherence is easily controlled by varying pump area. Such a 2D random laser provides with a compact on-chip tunable laser source and a unique platform to explore non-Hermitian photonics in the visible.

Random laser emission from dye-doped polymer films enhanced by SiC nanowires

As the third-generation semiconductor electronic material, silicon carbide (SiC) has good chemical stability and mechanical properties, leading to wide use in optoelectronic components, fiber sensing and detectors. However, there are few important reports on its application in the research of random laser. Hereby, we built a polymer random laser system with SiC nanowires as a scattering medium doped with dye by the spin coating method. The effect of different SiC concentrations on random laser properties and the enhancement mechanism are studied. The lasing intensity increases and threshold decrease in large concentration SiC nanowires at the same lasing system, and the minimum threshold is 20 μJ/pulse. By increasing the SiC concentration, the mean free path of photon scattering decreases, which promotes the photon gain effect and improves the laser performance. However, when the concentration of SiC nanowires is too large, the mean free path of photon scattering decreases further, and the self-absorption of fluorescence radiation emerges. Thus, fluorescence quenching is produced, leading to a negative effect on laser performance. Furthermore, the lasing wavelength can be adjusted by tuning the SiC nanowires concentrations, reaching 14 nm. The random laser enhanced by SiC nanowires is stable and pumped repeatable, which could pave the way to promote the application of SiC and achieve low-cost and high-performance random laser.

Organic Synthetic Photonic Systems with Reconfigurable Parity-Time Symmetry Breaking for Tunable Single-Mode Microlasers.

Synthetic photonic materials exploiting the quantum concept of parity-time (PT) symmetry lead to an emerging photonic paradigm-non-Hermitian photonics, which is revolutionizing the photonic sciences. The non-Hermitian photonics dealing with the interplay between gain and loss in PT synthetic photonic material systems offers a versatile platform for advancing microlaser technology. However, current PT-symmetric microcavity laser systems only manipulate imaginary parts of the refractive indices, suffering from limited laser spectral bandwidth. Here, an organic composite material system is proposed to synthesize reconfigurable PT-symmetric microcavities with controllable complex refractive indices for realizing tunable single-mode laser outputs. A grayscale electron-beam direct-writing technique is elaborately designed to process laser dye-doped polymer films in one single step into microdisk cavities with periodic gain and loss distribution, which enables thresholdless PT-symmetry breaking and single-mode laser operation. Furthermore, organic photoisomerizable compounds are introduced to reconfigure the PT-symmetric systems in real-time by tailoring the real refractive index of the polymer microresonators, allowing for a dynamically and continuously tunable single-mode laser output. This work fundamentally enhances the PT-symmetric photonic systems for innovative design of synthetic photonic materials and architectures.

Saturation Effect of Pump Light on Degenerate Four-wave Mixing in Azo Dye-doped Polymer

Saturation Effect of Pump Light on Degenerate Four-wave Mixing in Azo Dye-doped Polymer

Ordered photonic nanojet arrays for luminescent optical sensing in liquid and gaseous media

Here we demonstrate a novel sensor structure based on ordered arrays of dielectric microstructures produced via CMOS-compatible technology. The microstructures are fabricated on a transparent substrate and covered with a chemosensitive dye-doped polymer layer. Under excitation from the substrate side, the microstructures generate extended and intensive photonic nanojets into the polymer layer, selectively exciting it, thus forming a large distributing sensing area. The fabricated arrays were used for sensor response enhancement of luminescent dye-based chemosensitive receptors for metal ions detection in aqueous media and volatile organic compounds in gaseous media. We have shown that the sensor's detection limit depends on both PNJ length and intensity, which can be controlled by the refractive index difference between the microstructure and the sensitive layer, the parental microparticle shape and size, and spatial ordering and period of the microstructures in the array. It was found that once all the parameters are optimized, the photonic nanojet of 10λ length and peak intensity higher than 10 is generated. That results in a 50-fold reduction of the limit of detection for analytes in aqueous media and a 15-fold reduction of the limit of detection for analytes in gaseous media. The obtained results demonstrate a high potential for fabricated structures in the next-generation lab-on-chip device development.

Anomalous dips in reflection spectra of optical polymers deposited on plasmonic metals.

We have studied reflection spectra of dye-doped and undoped polymers deposited onto Ag and Au substrates and found anomalous dips in the UV spectral range. On top of Ag substrates, the λ ∼ 375nm dips were observed in undoped PMMA, PVP, and PS polymers as well as PMMA doped with Rh590 and HITC laser dyes. In silver-based samples, the spectral positions of the observed reflection dips were close to singularities in the refractive indexes of surface plasmon polaritons (SPPs) propagating at the interface between Ag and polymer. The latter singularities can tentatively explain the λ ∼ 375nm reflection dips, if the scattering of Ag and polymeric films is large enough to launch SPP without any prism or grating. The dips observed in reflection of Rh590:PMMA and HITC:PMMA on top of Au, were more pronounced than those on Ag, broader, shifted to shorter wavelengths, and their spectral positions had large standard deviations. Furthermore, no anomalous dips in gold-based samples were observed in the reflection spectra of undoped PMMA, PVP, and PS polymers, and a modest singularity in the SPP refractive index, predicted theoretically at λ ∼ 500nm, cannot explain the dips in the UV reflection spectra observed experimentally. It appears likely that the origin of the reflection dips on top of Au substrates is different from that on top of Ag substrates.

Visualized concentration sensors based on fluorescence indication in a dye-doped polymer microwire.

We demonstrate visualized microwire sensors based on fluorescence indication for detecting the concentrations of the aqueous solutions. The single Rhodamine (RhB) doped polymer microwires (PMWs) which are excited by the waveguiding excitation method are used as the sensory area. According to the fluorescent microimages of the PMWs, stable periodic oscillations could be observed in the RhB-doped PMWs. The fluorescent period which is dependent on the concentration is further analyzed by image processing and information extraction algorithms. Corresponding to a 1.0% change, the period length change of the visualized sensor reaches ∼380 nm, ∼270 nm, and ∼300 nm in NaCl, KCl, and sucrose solutions, respectively. The dection limits of the three solutions are estimated to be around 1.5 × 10-4%. The dye-doped PMW sensors by fluorescence indication and image analysis proposed here realize the direct visualized detection in concentration sensing, making it possible to avoid the challenges of stability and weak signal detection and offer a potentially stable and cost-effective approach for micro/nanofiber sensor application.

Amplification of whispering gallery microlaser emission using dye-doped graded-index polymer optical fiber

PMMA-based Rhodamine-640 perchlorate doped microring embedded hollow polymer optical fiber (MEHPOF), as well as graded-index polymer optical fiber (GIPOF), were fabricated. At a threshold pump pulse energy (PPE) of 0.23 mJ, a whispering gallery mode lasing was observed from the MEHPOF. The quality factor and free spectral range of the fabricated microcavity were found to be 3.69×103 and 0.25 nm respectively. The lasing modes from the MEHPOF were amplified using a GI fiber doped with the same gain material. The maximum gain achieved from the experiment is 17.5 dB. The optimum length of the amplifier fiber for maximum gain was found to be 8 cm.