Abbas Ghaleb Khalil, Georges Joseph
Laboratoire des Sciences Analytiques, Université Claude Bernard, Bât. CPE-308D, Domaine Scientifique de la Doua, Villeurbanne Cedex 69622, France.
Spectrochim Acta A Mol Biomol Spectrosc. 2004 Mar;60(4):863-72. doi: 10.1016/S1386-1425(03)00311-1.
Optimization of the optical design for pulsed-laser crossed-beam thermal lens (PLCBTL) spectrometry has been investigated. Experiments have been carried out with large samples as well as for very small samples in a microchannel and using different lens combinations to focus the probe and excitation beams. The results have been interpreted in terms of the influence of the excitation beam size as well as the degree of mode-mismatching of the excitation and probe beams on the optimum sample position and on the amplitude and decay of the photothermal signal. A semi-empirical formula that describes the influence of the sample position with respect to the probe beam waist has been established. We have shown that the optimum signal is inversely proportional to the waist of the excitation beam and is independent of the sample size as long as the size of the excitation beam is smaller than the microchannel. Time-resolved experiments have also shown that when the excitation beam is smaller than the sample, the signal decay depends not only on the size of the excitation beam but also on the mode-mismatching factor. Otherwise, the temporal characteristics are closely related to the size of the microchannel.
研究了脉冲激光交叉束热透镜（PLCBTL）光谱法光学设计的优化。针对大尺寸样品以及微通道中的极小型样品进行了实验，并使用不同的透镜组合来聚焦探测光束和激发光束。已根据激发光束尺寸以及激发光束与探测光束的模式失配程度对最佳样品位置以及光热信号的幅度和衰减的影响来解释实验结果。建立了一个描述样品相对于探测光束束腰位置影响的半经验公式。我们已经表明，最佳信号与激发光束的束腰成反比，并且只要激发光束的尺寸小于微通道，就与样品尺寸无关。时间分辨实验还表明，当激发光束小于样品时，信号衰减不仅取决于激发光束的尺寸，还取决于模式失配因子。否则，时间特性与微通道的尺寸密切相关。
