Dye-doped Polymer Research Articles

Resonance Energy Transfer Studies from Derivatives of Thiophene Substituted 1,3,4-Oxadiazoles to Coumarin-334 Dye in Liquid and Dye-Doped Polymer Media

In the present work, we have carried out energy transfer studies using newly synthesised derivatives of thiophene substituted 1,3,4-oxadiazoles namely, 2-(-4-(thiophene-3-yl)phenyl)-5-(5-(thiophene-3-yl)thiophene-2-yl)-1,3,4-oxadiazole [TTO], 2-(-4-(benzo[b]thiophene-2-yl)phenyl)-5-(5-(benzo[b]thiophene-2-yl)-1,3,4-oxadiozole [TBO] and 2-(4-(4-(trifluoromethyl)phenyl)phenyl)-5-(5-(4-(trifluoromethyl)phenyl)thiophen-2-yl)-1,3,4-oxadiazole [TMO] as donors and laser dye coumarin-334 as acceptor in ethanol and dye-doped polymer (poly(methyl methacrylate) (PMMA)) media following steady-state and time-resolved fluorescence methods. Bimolecular quenching constant (k q), translation diffusion rate parameter (k d), diffusion length (D l), critical transfer distance (R 0), donor- acceptor distance (r) and energy transfer efficiency (E T) are calculated. It is observed that, critical transfer distance is more than the diffusion length for all the pairs. Further, bimolecular quenching constant is also more than the translation diffusion rate parameter. Hence, our experimental findings suggest that overall energy transfer is due to Forster resonance energy transfer (FRET) between donor and acceptor in both the media and for all the pairs. In addition, considerable increase in fluorescence intensity and energy transfer efficiency is observed in dye-doped polymer matrix systems as compared to liquid media. This suggests that, these donor-acceptor pairs doped in PMMA matrix may be used for applications such as energy transfer dye lasers (ETDL) to improve the efficiency and photostability, to enhance tunability and for plastic scintillation detectors.

Ag nanowire-assisted low threshold WGM lasing from polymer optical fiber.

Whispering Gallery Mode (WGM) emission has been observed from Ag nanowire doped polymer optical fiber laser. Low threshold lasing and high photostability of the active medium has been noticed with a given concentration of Ag nanowires in the microcavity of the fiber. Quantum yield and lifetime measurements of the dye (active medium) with and without nanowires confirm that presence of nanowires enhance the rate of radiative decay of the fluorophore, thereby providing low pump pulse energy for the excitation of lasing modes in the cavity, as compared with a bare dye-doped polymer fiber laser.

Whispering gallery mode structure in polymer-coated lasing microspheres

Whispering gallery modes (WGMs) are frequently observed in the emission spectrum of a fluorophore coupled to a dielectric microsphere. If the fluorophore is excited strongly enough the WGMs can become lasing modes, producing a much higher signal-to-noise ratio and higher Q-factors. These favorable properties have led to recent demonstrations of biochemical sensing with lasing WGMs; however, as we show here, the underlying cavity structure that leads to lasing can be highly complicated and the lasing spectrum can result from a large number of closely spaced or overlapping modes. In silica spheres coated with a dye-doped polymer bilayer, hints of underlying complexity are already indicated by the skewed shape of the fluorescence WGMs. Under lasing conditions, a more complicated structure was observed with Q-factors over 10 times higher than observed in fluorescence, while transmission measurements showed a dense forest of resonances due to m-order degeneracy breaking from a lack of perfect spherical symmetry. Lasing preferentially occurs at wavelengths where these modes tended to be most densely spaced. The tapered part of the fiber to which the microsphere is attached can also have a strong effect on the lasing spectrum, leading to significant differences between the fluorescence and lasing resonances.

Stress Detection Using Polymer Optical Fiber with FRET Pair Dyes

Noble fiber-optic strain sensor using dye-doped polymer optical fiber (POF) was proposed, and its ability to sense stress (strain) by simple viewing of the large-core cross section was proposed. Conventional well-known fiber-optic strain sensors such as BOTDR or FBG types require spectral analysis to determine the strain value. Our sensor does not require expensive equipments such as spectral analyzer or well-tuned light source that are required in conventional fiber-optic strain sensors. A pair of luminescent organic dyes, Coumarin 540A and Rhodamine 6G, that functions as donor and acceptor of excitation energy were doped in core and cladding of the fiber, respectively. By taking this structure, stress applied to the fiber could be detected as an increase in cladding intensity. This happens because emission of core dye leaks to the cladding due to the deformation, and it excites the cladding dye. Using the fabricated POF, change in near field pattern upon different fiber bending diameter was detected. Lasers with three different wavelengths were used; namely, 406 nm, 532 nm, and 635 nm. 406 nm is the optimum wavelength for exciting the Coumarin 540A of the core efficiently. 532 nm excites Rhodamin 6G well, but does not excite Coumarin 540A well. 635 nm excites neither dyes. Pigtail end was coupled to the test fiber with direct contact to the core center of the test fiber in which no cladding excitation was expected. Fibers were stressed in various magnitudes by bending them in different loop diameters, namely, 1.5 cm, 3 cm, and 6 cm. Single loop was created in the middle point of the whole length. Relaxed condition, which the fiber was naturally straightened with no loop, was also investigated. Output beam from the test fiber was analyzed using Near Field Pattern measuring system (Hamamatsu C9664-01G02). In addition, dye-doped POF with lower numerical aperture had shown enhancement in sensitivity. Therefore, it was suggested that sensitivity of the sensor is controllable by further optimization of the waveguide parameters. Therefore, the proposed results suggests a potential for an enhanced fiber-optic stress detection with simpler and inexpensive accessory components.

New developments in the dye-doped polymer dispersed liquid crystals gratings: A review

ABSTRACTIn this study, the dye-doped polymer dispersed liquid crystals (PDLC) gratings techniques performed by the various research groups or being developed are briefly reviewed. Especially, the electrically switched diffraction and holographic gratings, have attained much attention by various research groups working in the PDLC-related display studies. The fabrication methodologies used for such grating texture, include like the conventional dye-doped PDLC grating, Azo-dye doped PDLC gratings, and lasing techniques etc., adopted for dye-doped PDLC gratings. The useful features and characteristics of their fabrication process of such gratings are discussed. Finally, some of the future perspectives on this particular research field are presented.

On-chip, high-sensitivity temperature sensors based on dye-doped solid-state polymer microring lasers

We developed a chip-scale temperature sensor with a high sensitivity of 228.6 pm/°C based on a rhodamine 6G (R6G)-doped SU-8 whispering gallery mode microring laser. The optical mode was largely distributed in a polymer core layer with a 30 μm height that provided detection sensitivity, and the chemically robust fused-silica microring resonator host platform guaranteed its versatility for investigating different functional polymer materials with different refractive indices. As a proof of concept, a dye-doped hyperbranched polymer (TZ-001) microring laser-based temperature sensor was simultaneously developed on the same host wafer and characterized using a free-space optics measurement setup. Compared to TZ-001, the SU-8 polymer microring laser had a lower lasing threshold and a better photostability. The R6G-doped SU-8 polymer microring laser demonstrated greater adaptability as a high-performance temperature-sensing element. In addition to the sensitivity, the temperature resolutions for the laser-based sensors were also estimated to be 0.13 °C and 0.35 °C, respectively. The rapid and simple implementation of micrometer-sized temperature sensors that operate in the range of 31 – 43 °C enables their potential application in thermometry.

Strain sensing based on radiative emission-absorption mechanism using dye-doped polymer optical fiber

A stress sensor based on a dye-doped polymeric optical fiber is able to detect stress by simple comparison of two luminescence peaks from a pair of energy transfer organic dyes. Coumarin 540A (donor) and Rhodamine 6G (acceptor) were doped in the core and cladding of the fiber, respectively. For various laser wavelengths, the change in the near-field pattern and visible emission spectrum upon variation in the fiber bending diameter was evaluated. From a comparison with a low-numerical-aperture fiber, it is shown that the sensitivity of the sensor is controllable by optimization of the waveguide parameters.

Fabrication and Characterization of Polymer Optical Fibers Doped with Perylene-Derivatives for Fluorescent Lighting Applications

Four different dye-doped polymer optical fibers (POFs) have been fabricated following a two-step fabrication process of preform extrusion and fiber drawing, using poly-(methyl methacrylate) (PMMA) as host material and dye derivatives from perylene and naphtalimide as active dopants. The side illumination technique (SIT) has been employed in order to determine some optical properties of the fabricated fibers, such as the side illumination coupling efficiency, optical loss coefficients, and their performance under solar simulator excitation. The aim of this work is to investigate the performance of the manufactured fibers for fluorescent lighting applications, specially targeting on fluorescent fiber based solar concentrators.

Thermo-optic tuning of whispering gallery mode lasing from a dye-doped hollow polymer optical fiber.

We report temperature-induced tuning of whispering gallery mode (WGM) laser emission from a Rhodamine-B-doped polymethylmethacrylate hollow optical fiber. Lasing studies on dye-doped hollow fibers with different radii were carried out with optical pumping using a Q-switched Nd:YAG laser. The observed lasing modes were confirmed as WGM emission with a high quality factor of 7.58×103. The diameter-dependent variation in lasing spectra of these hollow fibers was investigated. A tuning range of 0.44nm with a sensitivity of 0.011 nm/°C was obtained for the lasing modes by varying the temperature from 25°C to 60°C from a dye-doped polymethylmethacrylate hollow fiber of diameter 305μm.

Lasing from isotropic solid layer sandwiched between cholesteric liquid crystals

We investigated the lasing characteristics of multilayer cholesteric liquid crystal (CLC) structures comprising a dye-doped polymer matrix sandwiched between two films of CLC. Our experiment results were explained in terms of the calculated photonic density of states (DOS). The wavelength of lasing was located at the edge of the overlap between the band gaps of the CLC. Decreasing the thickness of the polymer matrix was shown to lower the threshold energy for lasing because of an increase in the DOS. Furthermore, a shift between the band gaps of the CLC films was shown to reduce the DOS at the lasing wavelength. The inclusion of a nematic liquid crystal layer within a sandwich structure makes it possible to tune the wavelength of lasing.

Study of Nonlinear Optical Properties of Disperse Yellow – 7 Dye-doped Polymer Films using CW Laser

The materials with an ability of self-focusing/defocusing through their light intensitydependent refractive index and phase shift properties are potential candidates for all-optical photonic devices. Several organic materials including dye-doped polymer films are attracting many researchers due to their advantages in terms of enhanced efficiency, and acceptable mechanical properties to fabricate useful devices. In this paper, we have reported the nonlinear optical properties like nonlinear absorption and nonlinear refraction of an organic dye Disperse Yellow - 7 (DY-7) doped in Polymethyl methacrylate-methacrylic acid (PMMA-MA) polymer matrix using open aperture and closed aperture Z-scan experimental methods by means of low power continuous wave (CW) laser beam. The optical limiting properties of these films are also studied using Type 1 and Type 2 configurations at different input powers using continuous wave (CW) laser beams of 532 nm wavelength. The nonlinear refractive index n2, nonlinear absorption coefficient β, changes in refractive index with input intensity, and the magnitude of third-order optical nonlinearity of the dye-doped film are experimentally determined. The sample is tested for optical power limiting in which the input limiting threshold and saturated output power level for both type 1 and type 2 optical limiting configurations are recorded. DY-7 dye-doped in PMMA-MA polymer film has shown saturation absorption at lower input irradiance and reverse saturation absorption at higher input irradiance along with thermal nonlinearity and hence found to be a potential candidate for the third harmonic property based photonic devices.

Study of Third Order Optical Nonlinearity in Disperse Orange-25 Dye-doped Polymer Films using CW Laser

The organic materials with the ability of self-focussing/defocusing through their light intensity-dependent refractive index and phase shift properties are potential materials in alloptical photonic devices have become interesting topic of continuous research. Several organic materials including dye-doped polymer films are attracting many researchers due to their advantages in terms of enhanced efficiency, and acceptable mechanical properties tofabricate useful devices. In this paper, we have reported the nonlinear optical properties like nonlinear absorption and nonlinear refraction of an organic dye Disperse Orange-25 (DO-25) doped in Polymethyl methacrylate-methacrylic acid (PMMA-MA) polymer matrix usingopen aperture and closed aperture Z-scan experimental methods by means of low power continuous wave (CW) laser beam. The optical limiting properties of these films are also studied using Type 1 and Type 2 configurations at different input powers using continuous wave (CW) laser beams of 532 nm wavelength. The nonlinear refractive index n2, nonlinear absorption coefficient β, changes in refractive index with input intensity, and the magnitude of third-order optical nonlinearity of the dye-doped film are experimentally determined. The saturated output power for type 1 and type 2 optical limiting are determined. The inputlimiting threshold and saturated output power level for both type 1 and type 2 optical limiting configurations are recorded. DO-25 dye-doped in PMMA-MA polymer film has shown saturation absorption at lower input irradiance and reverse saturation absorption at higher input irradiance and hence found to be a potential candidate for the third harmonic property based photonic devices.

Study of Third Order Optical Nonlinearity in Disperse Orange-25 Dye-doped Polymer Films using CW Laser

The organic materials with the ability of self-focussing/defocusing through their light intensity-dependent refractive index and phase shift properties are potential materials in alloptical photonic devices have become interesting topic of continuous research. Several organic materials including dye-doped polymer films are attracting many researchers due to their advantages in terms of enhanced efficiency, and acceptable mechanical properties to fabricate useful devices. In this paper, we have reported the nonlinear optical properties like nonlinear absorption and nonlinear refraction of an organic dye Disperse Orange-25 (DO-25) doped in Polymethyl methacrylate-methacrylic acid (PMMA-MA) polymer matrix using open aperture and closed aperture Z-scan experimental methods by means of low power continuous wave (CW) laser beam. The optical limiting properties of these films are also studied using Type 1 and Type 2 configurations at different input powers using continuous wave (CW) laser beams of 532 nm wavelength. The nonlinear refractive index n2, nonlinear absorption coefficient β, changes in refractive index with input intensity, and the magnitude of third-order optical nonlinearity of the dye-doped film are experimentally determined. The saturated output power for type 1 and type 2 optical limiting are determined. The input limiting threshold and saturated output power level for both type 1 and type 2 optical limiting configurations are recorded. DO-25 dye-doped in PMMA-MA polymer film has shown saturation absorption at lower input irradiance and reverse saturation absorption at higher input irradiance and hence found to be a potential candidate for the third harmonic property based photonic devices.

Random lasing in dye-doped polymer random media with a bubble structure

We experimentally investigate random laser (RL) emission from dye-doped polymer random media with inhomogeneously distributed scatterers. A random structure, which we call a bubble structure (BS), is realized by using nonscattering spacer particles randomly distributed in a gain medium. The experimental results show that the bubble-structured RL that incorporates an appropriate amount of spacer particles exhibits a higher spectral peak and a larger slope efficiency than conventional RLs. The highest peak intensity is observed when the size variation of spacer particles is maximized. Furthermore, an analysis of laser modes reveals that an increase in the spectral peak intensity can be partly attributed to the mode selection properties of the BS.

Fabrication of Lasing Whispering Gallery Mode Microresonators by Controllable Injection Method

Dye-doped polymer microdroplet resonators were fabricated by injecting dye solutions into a low refractive index UV curable polymer. The self-assembled microdroplets had the various sizes ranging from 5 to 200 μm. Pumped by a pulse laser, whispering-gallery-mode (WGM) lasing emission from the microresonators was achieved. Experimental results show that the microresonators had the advantages of high-Q factors, low lasing thresholds, and good long-term stabilities. The injection method can provide a promising approach for fabricating the high-Q WGM microresonators, which had some potential applications in the fields of tunable microlasers and on-chip biosensing system.

Advancement trends in dye-doped polymer dispersed liquid crystals—a survey review

ABSTRACTAt present there is significant interest in the doping of various types of dyes into polymer dispersed liquid crystals (PDLCs) in display films. Till to date, various types of dyes have been employed to improve the electro-optical properties of PDLC films in various situations by different research groups. Some of the advantageous features of dye-doped PDLC predict that such dye-doping into the PDLC films resolve the scattering effect, improve the films absorbance, enhance the degree of alignment, stability, and the electro-optical properties of the film such as reflectance, contrast ratio and better transmittance. The current article contains a short review on the present and past studies conducted on the dye-doped polymers dispersed liquid crystals films. The fabrication techniques and their various applications in the different display areas are reviewed, along with the new key findings are discussed.

Photovoltaic effect in dye-doped polymer films with free-surface and sandwich structures

Photovoltaic properties of the polymer composite films doped with cationic, anionic and neutral polymethine dyes were investigated. It was revealed that the magnitude and even the sign of photovoltaic effect change in going from the free-surface to sandwich structures. It was shown that in free-surface samples the photo-emf sign is determined by the nature of polymer and dye. By contrast, in sandwich structures the photo-emf sign does not depend on composition of the photoactive layer and is governed by drift of the photogenerated charge carriers in the electric field formed by different work function of the electron- and hole-collecting contacts.

Study the nonlinear optical property of pull/push type azo dye-doped polymer using 633nm He–Ne laser

Azo dyes with different pull/push substituents are selected as photosensitive molecules. Guest–host amorphous azo polymer samples are prepared by doping these azo dyes directly in poly(methyl methacrylate) polymeric matrices. Nonlinear optical properties of these pull/push type azo dye-doped polymers are investigated using the Z-scan experiment. The influence of the pull/push substituents and the azo dye concentration on the nonlinear optical property is studied.

Revisiting the combined photon echo and single-molecule studies of low-temperature dynamics in a dye-doped polymer

The photon echo (PE) spectroscopy and single-molecule spectroscopy (SMS) may be combined to give a very powerful tool for comprehensive study of low-temperature dynamics in dye-doped disordered solids (polymers, glasses). At the same time, this type of studies are likely to reveal discrepancies when comparing characteristic times of optical dephasing T2 and single-molecule zero-phonon spectral lines (ZPL) broadening obtained from PE and SMS, correspondingly, for tetra-tert-butylterrylene in polyisobutylene in the temperature range of a few–dozen of Kelvins [see Phys. Status Solidi B 241, 3480 and 3487 (2004)]. Inexplicably, PE-experiments demonstrated T2-times to be much shorter than it is sufficient to cause the corresponding ZPL broadening. Here we experimentally solve this problem and show that at T = 4.5–15 K the incoherent PE gives T2-times which correspond to the narrowest SM ZPL. On the SM-level there is a pronounced additional ZPL-broadening due to spectral diffusion processes which are strongly dependent on the characteristics time of the measurement (tens of nanoseconds for PE and seconds for SMS). There is also a broad distribution of ZPL spectral widths for different SMs due to different local environments, that contribute differently to both the optical dephasing and the spectral diffusion processes, but always in addition to the value of inverse optical dephasing times measured using a PE technique.

CW Optical Limiting Study in Disperse Yellow Dye-doped PMMA-MA Polymer Films

<div><p><em>Molecules with high two-photon absorption (TPA) cross section and the molecules which have reverse saturation absorption (RSA) cross section are of great interest today because of their application in three-dimensional optical data storage and photonic switches. During last forty years, several techniques have been developed to determine the two-photon absorption cross-sections and reverse saturation absorption cross-sections of the materials. This includes direct methods, such as nonlinear transmission and Z-scan methods and indirect methods, such as two-photon excited fluorescence and two-photon pump-probe transient absorption spectroscopy. During recent years, the organic dye-doped polymer films getting more attention due to their advantages to fabricate photonics devices. In this paper, we have studied the nonlinear optical properties like nonlinear absorption and nonlinear refraction of an azo dye Disperse yellow-7 (DY-7) doped in Polymethyl methacrylate-methacrylic acid (PMMA-MA) polymer matrix using open aperture and closed aperture Z-scan experimental methods using continuous wave (CW) laser. The optical limiting properties of these films are also studied in Type 1 and Type 2 configurations at different input power using continuous wave (CW) laser beams of 532 nm wavelength.</em></p></div>