Raghunathan Varun, Potma Eric Olaf
Department of Chemistry and Beckman Laser Institute, University of California at Irvine, Irvine, California 92697, USA.
J Opt Soc Am A Opt Image Sci Vis. 2010 Nov 1;27(11):2365-74. doi: 10.1364/JOSAA.27.002365.
Rigorous calculations are performed to study the effective reduction of the nonlinear excitation volumes when using phase-only masks to condition the pump and Stokes driving fields. Focal volume reduction was achieved using both a multiplicative operation of the excitation fields as well as a subtractive operation. Using a tunable optical bottle beam for the Stokes field, an effective reduction of the width of the excitation volume by a factor of 1.5 can be achieved in the focal plane. Further reduction of the focal volume introduces a rapid growth of sidelobes, which renders such volumes unsuitable for imaging applications. In addition, phase sensitive detection was found to provide information from selective sub-divisions of the engineered coherent anti-Stokes Raman scattering excitation volume. In the case of isolated nanoparticles, an apparent resolution improvement by a factor of 3 is demonstrated, and it is shown that the size of sub-diffraction-limited particles can be accurately determined using phase sensitive detection.
进行了严格的计算，以研究在使用纯相位掩模来调节泵浦场和斯托克斯驱动场时，非线性激发体积的有效减小。通过激发场的乘法运算以及减法运算都实现了焦体积的减小。使用可调谐光学瓶形光束作为斯托克斯场，在焦平面上可将激发体积的宽度有效减小1.5倍。进一步减小焦体积会导致旁瓣迅速增加，这使得这样的体积不适用于成像应用。此外，发现相敏检测可从工程化的相干反斯托克斯拉曼散射激发体积的选择性细分中提供信息。在孤立纳米颗粒的情况下，证明了分辨率明显提高了3倍，并且表明使用相敏检测可以准确确定亚衍射极限颗粒的尺寸。
