摘要
研究了染料嗪 (oxazine 1 )溶液中掺有高折射率玻璃微球时 ,微球表面附近染料荧光的荧光光谱特性 ,发现微球外表面附近染料分子的荧光光谱也会象球内情况一样形成结构共振。用Mie散射理论和微腔理论对此实验现象进行了分析 。
A perfect nonabsorbing microsphere with higher refractive index than the surrounding medium is a good optical microcavity. Inside such a sphere, which has a diameter of a few microns,there are a discrete number of resonant optical modes. The spontaneous emission cross-sections at the microcavity resonance photon energies are larger than the bulk spontaneous emission cross-sections because of the modified photon density of states of the microcavity. In the conventional study on microsphere, the luminescent molecules are inside the microspheres. In this paper, we report the fluorescent resonances of a dye solution outside a micrometer-sized, nonluminescent, spherical particle. Oxazine 1 was dissolved in distilled water, and its concentration was adjusted to 10 -3mol/l. TiBa glass microspheres (refractive index ～1.88, diameter=20～50μm) were dispersed in the aqueous solution of oxazine 1. One drop of the solution was put on a glass plate, and placed on a microscope stage at room temperature. The experimental apparatus is micro-Raman spectrometer (RENISHAW System 2000). The laser beam at wavelength of 633nm was introduced into an optical microscope and focused into a ～5μm spot by an objective lens (20x, numerical aperture 0.4). The laser beam was irradiated on the edge of the microsphere, so that the oxazine 1 aqueous solution just outside of the microsphere was excited. Emission from the microsphere was collected by the same objective lens, and the spectra were observed by the spectrometer (with CCD). Many regularly spaced, sharp peaks were observed together with a broad background spontaneous emission. These resonance peaks can be ascribed to microspherical cavity mode. Based on the Mie scattering theory, the separation between the adjacent peak wavelengths of the resonance modes is approximately given byΔλ=λ 2πdtan -1[{(n 2/n 1) 2-1} 1/2]n 1{(n 2/n 1) 2-1} 1/2(1) Where λ and d are the emission wavelength and the diameter of the microsphere, respectively. n 1 and n 2 represent the refractive indices of the surrounding solution (～1.33) and sphere. The calculated value for Δλ is 6.35nm in this spectral region, which agrees well with the observed mode spacing of 6.30nm.
出处
《发光学报》
EI
CAS
CSCD
北大核心
2002年第1期53-56,共4页
Chinese Journal of Luminescence
基金
国家自然科学基金资助项目 ( 6 96 780 15
6 97780 0 7和 6 0 1780 2 4)
关键词
荧光光谱
玻璃微球
结构共振
激光染料
恶嗪染料
fluorescent spectrum
glass microsphere
morphology dependent-resonances
laser dyes
