Lai Puxiang, Wang Lidai, Tay Jian Wei, Wang Lihong V
Optical Imaging Laboratory, Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, Missouri 63130-4899.
Nat Photonics. 2015 Feb;9(2):126-132. doi: 10.1038/nphoton.2014.322.
Non-invasively focusing light into strongly scattering media, such as biological tissue, is highly desirable but challenging. Recently, ultrasonically guided wavefront shaping technologies have been developed to address this limitation. So far, the focusing resolution of most implementations has been limited by acoustic diffraction. Here, we introduce nonlinear photoacoustically guided wavefront shaping (PAWS), which achieves optical diffraction-limited focusing in scattering media. We develop an efficient dual-pulse excitation approach to generate strong nonlinear photoacoustic (PA) signals based on the Grueneisen relaxation effect. These nonlinear PA signals are used as feedback to guide iterative wavefront optimization. As a result, light is effectively focused to a single optical speckle grain on the scale of 5-7 µm, which is ~10 times smaller than the acoustic focus with an enhancement factor of ~6,000 in peak fluence. This technology has the potential to benefit many applications that desire highly confined strong optical focus in tissue.
将光无创地聚焦到诸如生物组织等强散射介质中是非常理想的，但具有挑战性。最近，已经开发出超声引导的波前整形技术来解决这一限制。到目前为止，大多数实现方式的聚焦分辨率都受到声衍射的限制。在这里，我们介绍非线性光声引导的波前整形（PAWS），它在散射介质中实现了光学衍射极限聚焦。我们开发了一种高效的双脉冲激发方法，基于格鲁尼森弛豫效应产生强非线性光声（PA）信号。这些非线性PA信号被用作反馈来引导迭代波前优化。结果，光被有效地聚焦到5-7微米尺度的单个光学散斑颗粒上，这比声聚焦小约10倍，峰值通量增强因子约为6000。这项技术有可能惠及许多希望在组织中实现高度受限的强光聚焦的应用。
