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首页> 外文会议>Conference on Laser Applications to Chemical and Environmental Analysis, Feb 11-13, 2000, Santa Fe, New Mexico >Spherical cavity ringdown spectroscopy experiments
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Spherical cavity ringdown spectroscopy experiments

机译：球腔衰荡光谱实验

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We recently reported the time-domain observation of whispering gallery mode (WGM) propagation for picosecond optical pulses and macroscopic glass spheres. By analogy to the well-known acoustic phenomenon, optical WGMs propagate along the surface of spheres with high quality factors (Q) allowing optical path lengths many times the sphere diameter. The optical pulse duration (2 ps) was short relative to the equatorial round trip time and the detector response; thus, resolution of a series of individual output pulses was achieved, each corresponding to a single traverse of the sphere circumference. These results are complementary to optical frequency domain measurements wherein continuous wave excitation is used and WGMs are observed as sphere scattering resonances as the excitation laser wavelength is scanned. An unexpected build-up of the oscillation intensity was observed in our experiments that was approximately constant in the number of sphere round trips, independent of the sphere diameter; this phenomenon was explained using a mode evolution argument invoking a coupling of a family of efficiently excited modes to different modes better coupled to the detector geometry. We speculated that these robust spherical cavities could find use for cavity ringdown spectroscopy, as a replacement for the more common linear cavities. The evanescent wave penetrating the sphere surface should interact with the external environment. Optical absorption by species at the interface would create loss during each round trip, yielding a shorter cavity decay time, indicative of the absorption. Absorbing gases, adsorbed surface species, and liquid solutions would be sample candidates. The results of experiments designed to test this concept are reported here.
机译：我们最近报告了皮秒光学脉冲和宏观玻璃球体回音壁模式（WGM）传播的时域观察。类似于众所周知的声学现象，光学WGM以高品质因数（Q）沿球体表面传播，从而允许光程长度是球体直径的许多倍。相对于赤道往返时间和探测器响应，光脉冲持续时间（2 ps）短；因此，获得了一系列独立的输出脉冲的分辨率，每个输出脉冲对应于一个球体圆周的单次遍历。这些结果是对光学频域测量的补充，在光学频域测量中，使用连续波激发，并在扫描激发激光波长时观察到WGM作为球体散射共振。在我们的实验中，观察到了振荡强度的意外增强，该振荡强度在往返行程的数量中几乎是恒定的，与球形直径无关。使用模式演化论证来解释这种现象，该论证是将一系列有效激发的模态耦合到更好地耦合到检测器几何形状的不同模态。我们推测这些坚固的球形腔可用于腔衰荡光谱学，以替代更常见的线性腔。穿透球体表面的e逝波应与外部环境相互作用。界面处物质的光吸收将在每次往返过程中产生损耗，从而产生较短的腔衰变时间，表明吸收。吸收气体，吸收的表面物质和液体溶液将是候选样品。这里报道了旨在测试该概念的实验结果。

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