Department of Biomedical Engineering, Hong Kong Polytechnic University, Hong Kong, Hong Kong.
Shenzhen Research Institute, Hong Kong Polytechnic University, Shenzhen, 518057, China.
Sci Rep. 2019 Feb 7;9(1):1537. doi: 10.1038/s41598-018-38326-4.
Focused and controllable optical delivery beyond the optical diffusion limit in biological tissue has been desired for long yet considered challenging. Digital optical phase conjugation (DOPC) has been proven promising to tackle this challenge. Its broad applications, however, have been hindered by the system's complexity and rigorous requirements, such as the optical beam quality, the pixel match between the wavefront sensor and wavefront modulator, as well as the flatness of the modulator's active region. In this paper, we present a plain yet reliable DOPC setup with an embedded four-phase, non-iterative approach that can rapidly compensate for the wavefront modulator's surface curvature, together with a non-phase-shifting in-line holography method for optical phase conjugation in the absence of an electro-optic modulator (EOM). In experiment, with the proposed setup the peak-to-background ratio (PBR) of optical focusing through a standard ground glass in experiment can be improved from 460 up to 23,000, while the full width at half maximum (FWHM) of the focal spot can be reduced from 50 down to 10 μm. The focusing efficiency, as measured by the value of PBR, reaches nearly 56.5% of the theoretical value. Such a plain yet efficient implementation, if further engineered, may potentially boost DOPC suitable for broader applications.
长期以来，人们一直希望在生物组织中实现超越光扩散极限的聚焦和可控光学传输，但这被认为是具有挑战性的。数字光学相位共轭（DOPC）已被证明是解决这一挑战的一种有前途的方法。然而，其广泛的应用受到系统复杂性和严格要求的限制，例如光束质量、波前传感器和波前调制器之间的像素匹配，以及调制器有源区的平整度。在本文中，我们提出了一种简单而可靠的 DOPC 装置，具有嵌入式四相、非迭代方法，可以快速补偿波前调制器的表面曲率，以及一种无需电光调制器（EOM）的非相移在线全息术方法用于光学相位共轭。在实验中，使用所提出的装置，通过标准毛玻璃的光聚焦的峰值与背景比（PBR）可以从 460 提高到 23,000，而焦点光斑的半峰全宽（FWHM）可以从 50 降低到 10 μm。通过 PBR 值测量的聚焦效率达到了理论值的近 56.5%。如果进一步设计，这种简单而高效的实现方式可能会推动 DOPC 适用于更广泛的应用。
