Optical limiting behavior of Sudan III dye doped polymer

The optical limiting performance of Sudan III dye doped into ethylene propylene diene polymethylene polymer (EPDM) is investigated using 532 nm, 10 ns pulses from a frequency-doubled Nd-YAG laser. The optical limiting behavior is investigated by transmission measurement through the sample at different concentrations. Our results show that the optical limiting efficiency is concentration dependent.     

Gain studies of coumarin 307 dye doped polymer laser

Solid state dye doped polymer is an attractive alternative to the conventional liquid dye solution. In this paper the laser characteristics of coumarin 307 (C307) doped polymethyl methacrylate rods modified with dioxane are studied under nitrogen laser excitation in a transverse pumping configuration and the variation of gain of the dye in solid medium for different pumping powers is studied. The photobleaching of dye doped polymer rod is also studied.     

Optical limiting behavior of disperse red 1 dye doped polymer

Measurements of optical limiting response in disperse red 1 dye doped into ethylene propylene diene polymethylene polymer (EPDM) are reported using 532 nm wavelength, 10 ns pulses from a frequency-doubled Nd-YAG laser. The optical limiting behavior of the dye doped polymer was studied by transmission measurement technique at various concentrations. The results reveal that the optical limiting efficiency is dependent on concentration.     

Holographic grating formation in dye doped polymer dispersed liquid crystals

We report a detailed investigation on holographic grating formation in dye-doped polymer dispersed liquid crystals. Both optical and scanning electron microscope measurements have been carried out. All the experimental data support the idea that a photorefractive-like effect is the basic mechanism of the optical storage effect, while it is demonstrated that neither droplets' size or shape effects, nor dye or polymer reorientation are involved in the process.     

Broadband emission of dye mixtures in films and polymer matrices

Emission of mixtures of organic compounds in thin acrylic films and matrices is investigated from the blue to red range of the spectrum. The present paper is aimed at studying the feasibility of obtaining white light by conversion of output diode radiation (379 nm) using a mixture of fluorophors. It is demonstrated that the emission band shape depends on ratios of dye concentrations and geometry of excitation and registration that must be taken into account in the development of devices based on these compounds.__________This revised version was published online in May 2005 with a correction on affiliation.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 67–70, November, 2004.     

掺杂红外染料聚叠氮缩水甘油醚工质激光烧蚀推进性能优化探索

选择含能聚合物聚叠氮缩水甘油醚(GAP)作为激光烧蚀微推力器的工质,分析了红外染料掺杂对激光烧蚀GAP工质推进性能的影响.通过对比掺杂红外染料GAP在不同激光功率密度、掺杂浓度、靶材厚度和激光烧蚀模式下的推进性能数据和烧蚀羽流,初步探索了掺杂红外染料GAP工质的推进性能优化方式.实验结果表明:透射式激光烧蚀模式下,激光能量的指数衰减特性和掺杂红外染料GAP的强黏性使得烧蚀羽流中易存在未充分烧蚀的工质; GAP的推进性能受红外染料掺杂浓度和靶材厚度的综合影响,当靶材厚度与激光吸收深度接近时,靶材充分吸收激光能量使中心烧蚀区达到化学能释放的温度阈值,同时沿激光传播方向未充分烧蚀的质量最少,此时推进性能达到最优值.反射式下掺杂红外染料的聚合物的激光烧蚀过程遵循"先吸收激光能量先喷射"的规律,工质分解充分,推进性能优于透射式.     

Surface relief grating formation in luminescent dye doped photochromic polymer containing azobenzene side groups

We study the formation of a surface relief grating and photoluminescence in a thin layers of a photochromic polymer doped with the luminescent dyes 3-(1,1-dicyanoethenyl)-1-phenyl-4,5-dihydro-1H-pyrazole and Rhodamine 6G. Surface topography measurements via Atomic Force Microscopy confirmed the existence of a surface relief grating with amplitudes as high as 650 nm both for doped and undoped photochromic polymers. Spectroscopic measurements carried out for polymers containing luminescent dyes have shown efficient photoluminescence and amplified spontaneous emission which is characteristic for gain media.     

On the design of a Nd doped silica fiber-laser using a cholesteric liquid crystal mirror

We report operation of a Nd³⁺-doped fiber-laser using a cholesteric liquid crystal acting as a narrow band reflector. The aim of this work is to apply to a fiber-laser the particular optical properties of an helical structure, whatever is the medium exhibiting this structure, either a liquid crystal or either any other material. The advantage of the use of these mediums in the design of fiber-lasers is that they can favourably take the place, in an easy and compact way, of several optical elements such as a polarizer and a quarter-wave plate at one and the same time. This technology promises to design rugged compact low cost tunable coherent sources the lasing range of which can easily be adjusted. We emphasize here the particular part played by the cholesteric liquid crystal-glass interface in the laser action of the fiber. Received 21 October 1999 and Received in final form 7 February 2000     

Two-photon-pumped amplified spontaneous emission and cavity lasing of an organic dye HEASPS in PHEMA polymer

Two-photon-absorption (TPA)-induced upconverted amplified spontaneous emission (ASE) and cavity lasing of a styrylpyridinium dye: trans-4-[p-(N-hydroxyethyl-N-ethylamino)styryl]-N-methylpyridinium p-toluene sulfonate (abbreviated as HEASPS) in poly(2-hydroxyethyl methacrylate) (abbreviated as PHEMA) polymer were observed under a picosecond pump condition. The spectral and temporal behaviors of TPA-induced fluorescence, ASE and cavity lasing were studied. The cavity lasing with a total oscillation time of more than 200 ps was achieved when pumped with 1064-nm, 50-ps laser irradiation. The population inversion could persist for three times longer than the duration of the pump pulse. The gain coefficients of the dye-doped polymer at various wavelengths were calculated based on cavity lasing spectra and one-photon fluorescence spectra. PACS 78.20.Ek; 42.65.Ky; 42.65.Re; 78.47.+p     

Electro-optical properties of polymer stabilized cholesteric liquid crystal film

Liquid crystals (LCs) and polymers are extensively used in various electro-optical applications.In this paper,normal mode polymer stabilized cholesteric LC film is prepared and studied.The effects of chiral dopant and monomer concentrations on the electro-optical properties,such as contrast ratio,driving voltage,hysteresis width and response time,are investigated.The reasons of electro-optical properties influenced by the concentrations of the materials are discussed.Through the proper material recipe,the electro-optical properties of polymer stabilized cholesteric LC film can be optimized.     

Defect mode properties in a one-dimensional photonic crystal

Based on the transfer matrix method (TMM), the interaction of electromagnetic waves with one-dimensional (1D) defective photonic crystal in ultraviolet (UV) frequency region had been studied. With the calculated transmittance characteristics in the wavelength domain, it can be found that the defect mode can be generated within the photonic band gap (PBG) at the central wavelength. Also the effects of many parameters such as the angle of incidence, the state of polarization and the defect layer thickness have been taken in account. A significant effect in generating multiple defect peaks within the PBG has been illustrated.     

Single mode operation of a tunable cw dye laser

Using the differential absorption method the NO₂ concentration within the plume of a smoke stack and over the area of a chemical factory was measured.     

甲基红掺杂碳纳米管悬浮液的光限幅特性研究

利用实验的方法研究了甲基红掺杂碳纳米管悬浮液对波长为532 nm激光的光限幅效应.分析了样品厚度和入射激光重复频率对光限幅特性的影响,并与纯碳纳米管悬浮液的光限幅特性进行了比较.实验结果表明,对于线性透过率为60%（500 nm）的碳纳米管悬浮液,掺入甲基红后其沉淀速度明显减慢,限幅阈值由250 μJ降低为200 μJ;对于2和5 mm 厚度的样品,掺杂甲基红使碳纳米管悬浮液的箝位输出激光脉冲能量分别由45和20 μJ降低为35和9 μJ.     

甲基红掺杂碳纳米管悬浮液的光限幅特性研究

利用实验的方法研究了甲基红掺杂碳纳米管悬浮液对波长为532 nm激光的光限幅效应.分析了样品厚度和入射激光重复频率对光限幅特性的影响,并与纯碳纳米管悬浮液的光限幅特性进行了比较.实验结果表明,对于线性透过率为60%（500 nm）的碳纳米管悬浮液,掺入甲基红后其沉淀速度明显减慢,限幅阈值由250 μJ降低为200 μJ;对于2和5 mm 厚度的样品,掺杂甲基红使碳纳米管悬浮液的箝位输出激光脉冲能量分别由45和20 μJ降低为35和9 μJ. 关键词： 非线性光学 光限幅效应 甲基红 染料掺杂碳纳米管悬浮液     

Mechanics of a rate-dependent polymer network

Pure rubber-like materials usually have little or no rate-dependency during finite straining. In contrast, polymeric materials can exhibit rate-dependent rubber-like responses in the large-strain range. A thermodynamic analysis points to the existence of rate-effects for an elastic network. The presence of reversible crystallization with a rate-dependent feature changes the conformation mobility of the network structure and, subsequently, contributes to the alterations in its elasticity. The internal energy of an elastic polymer network, however, exhibits a step-wise dependence on the applied strain-rates; it alters only at discrete values of strain-rates, every pair of which differs with a unique value that can be described as a sensitivity parameter. At loading rates lower than this parameter, the rate-effects of the polymeric network are absent.     

Security devices based on liquid crystals doped with a colour dye

Liquid crystal properties make them useful for the development of security devices in applications of authentication and detection of fakes. Induced orientation of liquid crystal molecules and birefringence are the two main properties used in security devices.     

Polarized emission of doped ZnS crystals

Polarization of light emitted in various spectral ranges was studied in two single crystals ZnS:Cu, Cl and ZnS:Ag, Cu, Al. The G-Cu, B-Cu and a small amount of S-A centers have been identified in the ZnS:Cu, Cl crystal by the spectral and polarization methods. The B-Ag band was found in the spectrum of the ZnS:Ag, Cu, Al crystal and its polarization properties investigated. This emission appears to be always polarized perpendicular to the [111]_c axis of the stacking faults independently of the polarization of the exciting light. The symmetry of the B-Ag center is not lower than that of the host lattice. Analogy with G-Cu centers suggests a model for the B-Ag center in which the polarization comes from the symmetry properties of the Ag²⁺ orbitals in the trigonal field of stacking faults.     

Spectral optimisation of a synchronously mode locked femtosecond dye laser

Through optimisation of the spectrum and dispersion parameters of a synchronously mode locked Rhodamine B dye laser, pulses as short as 270 fs have been directly generated without using any saturable absorber or pulse compressor. In addition a system of tunable output coupling with well characterised dispersion has been demonstrated.     

Sharply directed emission in microcavity organic light-emitting diodes with a cholesteric liquid crystal film

A flexible microcavity organic light-emitting diode (OLED) was fabricated and the emitting characteristics were examined. A pair of right- and left-handed cholesteric liquid crystal (CLC) films were attached to the microcavity OLED between aluminum (Al) and silver (Ag). Sharply directed spontaneous emission was observed from microcavity OLEDs, in which a typical luminescent material, 8-hydroxyquinoline aluminum (Alq₃), with a broad emission spectrum was used for emitting layer. The introduction of the CLC film improved both the emission bandwidth and directionality, preserving the turn-on voltage and maximum brightness.