A microring multimode laser using hollow polymer optical fibre

We report the observation of multimode laser operation at wavelengths corresponding to whispering-gallery modes from a freestanding microring cavity based on rhodamine B dye-doped PMMA hollow optical fibre. Cylindrical microcavities with diameters 155, 340 and 615 μm were fabricated from a dye-doped hollow polymer optical fibre preform. An average mode spacing of 0.17 nm was observed for the 340 μm cavity. This shows that the laser mode intensity distribution is concentrated on the outer edge of the cavity.     

DR1掺杂复合凝胶玻璃光学二阶非线性效应的研究

对分散红1(disperse red 1,缩写为DR1)掺杂聚甲基丙烯酸甲酯(PMMA)/凝胶玻璃复合材料的光学二阶非线性及其热稳定性进行了研究.分析了实时极化二次谐波产生(SHG)的动态过程及影响光学二阶非线性的因素.同时对影响DR1掺杂复合凝胶玻璃材料的光学二阶非线性强度的因素进行了分析. 关键词：     

Red colored transparent PMMA-SiO2 hybrid films

Red colored transparent organic-inorganic hybrids films of a cross-linked polymethyl-methacrylate (PMMA) and silica were prepared via the sol-gel route using tetraethoxy-silane (TEOS) as precursor and a commercial organic red dye. 3-(Trimethoxysilyl) propyl methacrylate (TMSPM) was used to make compatible the organic and inorganic components of the precursor solution mixture. Four type of colored hybrid films were deposited using precursor solutions with the reactants molar ratio 1:0.5:1 for TEOS: TMSPM:MMA, respectively, and four different weight contents of the organic red dye. The hybrid films were studied by Fourier transform infrared spectroscopy, atomic force microscopy and optical transmission and reflection spectroscopy. The hardness of the films was determined from a pencil hardness test referred to ASTM Standard D 3363-92. The results showed that the colored hybrid films have a thickness of about 2 μm and consist of a homogeneous cross-linked organic-inorganic matrix with embedded dye molecules very well dispersed. The hardness of the hybrid films was enhanced with respect to that of the pure organic component. The AFM measurements showed very flat and smooth film surfaces with rms average roughness about 0.3 nm. The optical properties of the hybrid films including their color properties were determined from optical transmission and reflection spectroscopy. We found that the intensity of the color in the hybrid films and the corresponding color coordinates depend on the amount of red dye in the hybrid films. Photodegradation studies were performed by monitoring the optical density of the films as a function of the exposure time to illumination for several values of illumination intensity.     

Fluorescence characterization and gain studies on a dye-doped graded index polymer optical-fiber preform

Preparation of an appropriate optical-fiber preform is vital for the fabrication of graded-index polymer optical fibers (GIPOF), which are considered to be a good choice for providing inexpensive high bandwidth data links, for local area networks and telecommunication applications. Recent development of the interfacial gel polymerization technique has caused a dramatic reduction in the total attenuation in GIPOF, and this is one of the potential methods to prepare fiber preforms for the fabrication of dye-doped polymer-fiber amplifiers. In this paper, the preparation of a dye-doped graded-index poly(methyl methacrylate) (PMMA) rod by the interfacial gel polymerization method using a PMMA tube is reported. An organic compound of high-refractive index, viz., diphenyl phthalate (DPP), was used to obtain a graded-index distribution, and Rhodamine B (Rh B), was used to dope the PMMA rod. The refractive index profile of the rod was measured using an interferometric technique and the index exponent was estimated. The single pass gain of the rod was measured at a pump wavelength of 532 nm. The extent of doping of the Rh B in the preform was studied by axially exciting a thin slice of the rod with white light and measuring the spatial variation of the fluorescence intensity across the sample.     

Third-order optical nonlinearities and optical-limiting properties of a Pararosanilin dye in liquid and solid media

Solid-state dye-doped polymers are attractive alternatives to the conventional liquid-dye solutions. In this paper, the third-order nonlinear optical properties of a Pararosanilin dye in 1-Butanol and a dye-doped polymer film were measured by the Z-scan technique using a continuous wave 532-nm diode-pumped Nd:Yag laser. This material exhibits a negative optical nonlinearity. The low-power optical-limiting properties based on the nonlinear refraction of this material have also been studied.     

Hybrid near-field optical memory and photofabrication in dye-doped polymer film

A hybrid near-field fluorescence microscopy, which combines near-field scanning optical microscopy and photon scanning tunneling microscopy, is demonstrated for nanoscale optical memory and photofabrication on spin-coated dye-doped polymer films. Storage capacity and readout signal-to-noise ratio with near-field one-photon and two-photon excitations are studied.     

Characteristics of color optical shutter with dye-doped polymer network liquid crystal

The optical properties and the theoretical prediction of color optical shutter with dye-doped polymer network liquid crystal (PNLC) were investigated. The view-angle dependence of reflectance according to the bias conditions showed distinctive characteristics, which could be explained from the effects of dye absorption and path length. It was also shown that the thickness dependence of reflectance was strongly influenced by the light-scattering coefficient. Our experimental results matched up well with the theoretical prediction based on the light scattering of liquid crystals in polymer network and the absorption of dichroic dye. This work indicates potential to improve the optical device using dye-doped liquid crystal-polymer composite.     

Optical properties of nanocomposites based on polymers and metal nanoparticles

The optical properties of nanocomposites of metal nanoparticles and polymers of two types have been studied. Gold and silver nanoparticles were obtained by laser ablation of corresponding metal targets in acetone and chloroform. The thus formed colloidal solutions were used to prepare nanocomposites of these nanoparticles in polymer matrices of polymethylmethacrylate (PMMA) and fluorine-containing polymer LF-32. The polymer matrix is found to promote aggregation of the metal nanoparticles under study into elongated chains. In turn, metal nanoparticles affect the polymer matrix. In the case of PMMA, suppression of the vibrational peaks of polymer in the low-frequency region of its Raman spectrum occurs. In the case of LF-32, gold and silver nanoparticles amplify the Raman signal of the polymer matrix. In addition, the Raman spectra of nanocomposites indicate aggregation of disordered carbon around the nanoparticles obtained by laser ablation in organic solvents. The possibilities of studying the ultrafast (about 1 ps) optical response of the nanocomposites obtained in order to use it in photonics elements are discussed.     

Change in optical path length of saturable absorbing dye-doped polymer films under laser irradiation

The cause of the change in the optical path lengthΔ(nd) of the saturable absorbing dye-doped polymer films under laser irradiation is investigated using polyvinyl alcohol and gelatin films doped with erythrosin B. The temperature rise of the dye-doped films, the changes in optical path length, film thickness, the refractive index and the optical density of the dye-doped films are measured under laser irradiation. The thermal expansion due to the temperature rise of the dye-doped films caused by the irradiation has greater effect on theΔ(nd) than the fading of dye molecules due to the irradiation of laser beams.     

双包层掺染料聚合物光纤放大器的增益性能分析

双包层聚合物光纤放大器可以减小染料的热漂白,使用速率方程的方法,给出了一个能够全面描述双包层掺染料聚合物光纤放大器增益性能的模型,模型既考虑了染料三重态能级对速率方程的影响,又考虑了双包层结构对泵浦光的影响,可以在稳态的情况下计算放大器的各种增益性能指标.     

Conductivity, dielectric behaviour and thermal stability studies of lithium ion dissociation in poly(methyl methacrylate)-based gel polymer electrolytes

Thin films of poly(methyl methacrylate) (PMMA) with lithium triflate (LiCF₃SO₃) were prepared by using the solution-casting method with PMMA as the host polymer. Ionic conductivity and dielectric measurements were carried out on these films. The highest conductivity for polymer electrolyte with a ratio of 65:35 was found to be 9.88 × 10⁻⁵ S cm⁻¹, which is suitable for the production of mobile phone battery. Thermal gravimetric analysis was carried out to evaluate the thermal stability of the polymer electrolyte. The addition of salts will increase thermal stability of the polymer electrolyte.     

氧化多孔硅/聚合物复合膜的折射率

用Bruggeman模型理论,分析了氧化多孔硅/聚合物复合膜的等效折射率与多孔硅孔隙率、氧化度和嵌入率的关系.实验研究了嵌入PMMA材料的氧化多孔硅/聚合物膜的等效折射率.证实了在多孔硅中嵌入聚合物可使薄膜的光学参量保持稳定.     

Effect of Photo-Induced Periodic Gain Structure on Oscillation Power and Tunability in Polymer Dye Laser

Pumping dye-doped organic polymer by interference pattern of a frequency-doubled Nd:YAG 532 nm laser to induce a periodic gain-structure and confining it within a stable optical resonator, the oscillation output can be effectively enhanced in comparison with either that of uniform irradiation, i.e., pumping, or of distributed feedback (DFB) operation, and the oscillation wavelength becomes tunable by adjusting the period of the interference pattern. Using Rhodamine-B as a dopant over the range from 200 to 1000 ppm, the oscillation output was enhanced by - 10 dB, which was larger than the output of the uniform irradiation and was - 30% greater than the DFB scheme. Moreover, changing the period of the interference pattern by adjusting the setting angle of the Koster prism enables us to vary the oscillation wavelength around 600 nm.     

Photoacoust1C Studies on Very Thin Poly(Methyl Methacrylate) Films Prepared by a Cast1Ng-On-Water Method

Photoacoustic (PA) responses from very-thin poly(methyl methacrylate) (PMMA) films were investigated at various lamination conditions. The PA signal increased when the dye-doped films were laminated up to five layers, but tended to saturate beyond five layers. When the blank films were superimposed on the dye-doped film, the signal became smaller. The signal was larger when the dye-doped film was arranged outermost in the laminated film assembly of dye-doped and blank films. The results imply the effect of film vibration on the PA response.     

Multimode laser emission from dye-doped hollow polymer optical fibre

Well-resolved multimode laser emission was observed for the first time from a freestanding microring cavity based on Rhodamine B dye-doped hollow polymer optical fibre by transverse pumping. Fibres with different diameters such as 180, 460, 640 and 800 μm were fabricated from a dye-doped hollow polymer preform. A blueshift in the mode structure was observed with decrease in fibre diameter leading to wide range tunability of the laser emission.     

聚合物材料PMMA/DR1光漂白过程中折射率的变化

用双光束扫描法研究了在488nm的Ar^ 激光照射下，聚合物材料RMMA／DR1的光漂白过程，为精确测量光漂白模型中的参数提供了一种简单实验方法。这对于今后用光漂白的方法制备光波导器件具有重要意义。     

Preparation of Organic–Inorganic Multifunctional Nanocomposite Coating via Sol-Gel Routes

The inorganic–organic nanocomposite coatings are prepared on poly(methyl methacrylate) (PMMA) substrate by the spinning technique which involves incorporating homogeneously nanosized ZnO particle into the molecular inorganic–organic hybrid matrices. The hybrid matrices are derived from tetraethoxyasilane (TEOS) and 3-glycidoxypropyltrimethoxyailane (GLYMO). To avoid the destruction of the polymer structure caused by ZnO and modify the interface between nanoparticles and organic groups, ZnO was first surface-coated with SiO₂ from hydrolyzed TEOS using ammonia water as catalyst. The coatings thus obtained are dense, flexible, abrasion resistant and UV absorbent.     

杂环偶氮染料薄膜的全息光存储

采用含杂原子的偶氮染料TADEB、DMTAM、DMTAA和DMTAMB掺杂高分子聚合物PMMA制成薄膜,利用四波混频全息光路系统,研究了它们的全息光存储性质。实验结果显示DMTAA样品的衍射效率最高,可达到22%,是一种存储性能较为优良的永久性全息光存储介质材料。     

采用密度泛函理论与分子动力学对聚甲基丙烯酸甲酯双折射性的理论计算

双折射性是各种光学材料的重要性能之一,具有高双折射率的光学材料在诸多研究及工业领域的应用越来越广泛.然而,作为常用的光学薄膜及光波导材料之一的聚合物材料的双折射性通常却很弱,只能通过实验对其双折射率进行大致的表征,缺乏对其双折射率的系统性理论计算,从而限制了提高聚合物双折射性的研究.本文建立了从聚合物的单体分子结构到多分子链的系统性的双折射率理论计算方法,并借助此方法研究了导致聚合物弱双折射性的限制因素.以聚甲基丙烯酸甲酯(PMMA)为研究对象,运用密度泛函理论研究了其本征双折射率,这里的本征双折射率是指分子链完全取向时其单体单元的双折射率.计算结果表明其本征双折射率高达0.0738左右,并且通过计算给出了PMMA单体单元的平均双折射率色散曲线.采用分子动力学方法研究了该聚合物(包含20个分子链)的材料双折射率.理论计算结果表明,尽管该聚合物具有较大的本征双折射率,但是由于聚合物中分子链取向度极低,聚合物材料最终表现出来的双折射率只有0.00052.本文建立的研究方法及研究结果为研究增强聚合物材料双折射性提供了理论依据.