Three-dimensional holographic optical manipulation through a high-numerical-aperture soft-glass multimode fibre

Abstract

Holographic optical tweezers (HOT) holds great promise for many applications in modern biophotonics, allowing the creation and measurement of minuscule forces on biomolecules, molecular motors and cells. Optical geometries used in HOT currently make use of bulk optics, and their usage in-vivo is compromised by the optically turbid nature of living tissues-a limiting factor in any advanced high-resolution imaging method. We present an alternative HOT approach in which multiple three-dimensional optical traps are introduced through a high-numerical-aperture multimode optical fibre, thus enabling an equally versatile means of optical manipulation through channels having cross-section comparable to the size of a single cell. Our work demonstrates real-time manipulation of 3-D arrangements of micro-objects, as well as the possibility of manipulating inside otherwise inaccessible cavities. We show that the position of the optical traps can be controlled with nanometric resolution over fibre lengths exceeding 100 mm. The results provide the basis for exploitation of holographic manipulation and other high-numerical-aperture techniques, including advanced forms of microscopy, through single-core-fibre endoscopes deep inside living tissues and other complex environments.

Physical Layer Security in Multimode Fiber Optical Networks

“…The T M approach proved to be extremely helpful to overcome the challenge to use the MMF either as an imaging [22,23,24,25,26] or data transmitting tool [34,30] for compensating the fiber's light scrambling property. Besides experimental techniques to determine the T M , approaches to identify the T M via deep learning [35,36] or convex optimization algorithms [37] have already been shown.…”

“…Using the MMF as an flexible endoscope, the aim is to generate scanning focal spots at the end of the fiber. Therefore it is obvious to choose diffraction limited focal spots [23,26,25] as the T M basis. Another suitable basis to describe light transmission through an MMF is a basis of plane waves with varying spatial frequencies [24].…”

“…Nowadays, the MMF is a key device in several fields of research. They are used in biophotonical applications [19,20,21,22,23,24,25,26] to gain access to hard-to-reach areas due to their flexibility and high number of degrees of freedom in a minimum space. These properties are particularly helpful for image transmission using the MMF as an ultrathin endoscope.…”

Single-cell micro- and nano-photonic technologies

“…To this end, graded index (GRIN) lenses [91] have been widely employed to image neurons in deep structures of the mouse brain with single, multi-photon or patterned multi-photon illumination [92][93][94][95][96]. To further reduce the implant cross sizes, researchers are pursuing wave front modulation techniques to control modal propagation in single multi-mode optical fibers in order to produce tight focal spots at the fiber distal end [97][98][99][100][101]. This ground-breaking approach has recently enabled 3D, sub-cellular resolution imaging of dendrites and dendritic spines in the mice dorsal striatum as well as spatially resolved Ca 2+ imaging in rat organotypic hippocampal slices with a 50 µm-core optical fiber [102].…”

Excitation of higher-order modes in optofluidic photonic crystal fiber

“…The controlled excitation of higher-order fiber modes has become an increasingly active area in photonics research with a range of interdisciplinary applications. For example, spatial light modulator (SLM)-based wavefront shaping techniques [1] have enabled the controlled excitation of coherent mode superpositions in multimode fibers [2], with novel applications in lensless endoscopic imaging [3,4,5] and fiber-based optical trapping [6]. In fiber communication systems, mode-division multiplexing has been used to improve data transfer rates [7,8,9,10].…”