We develop a generalized optimisation algorithm based on gradient ascent to design mode sorters and optical circuits using multi-plane light conversion. We experimentally demonstrate the sorting of photons based on their orbital angular momentum state, Zernike mode, step-index multimode fibre (MMF) mode, or, most generally, a random spatial mode basis of up to 55 modes. In simulations, we showcase the future potential of these devices to undo the scrambling introduced by the propagation of light through optical fibres: we design a passive device, which we term an optical inverter, that is complementary to a MMF and reverses its scrambling effect on light. We describe how this enables real-time imaging directly through MMFs.
Hair-thin strands of multimode optical fibre (MMF) can operate as ultra-low footprint endoscopes–delivering sub-cellular resolution images from deep inside the body at the tip of a fine needle. However, images transmitted through MMFs are unrecognisably distorted. Here we present two new ways to unscramble this light and recover images. Firstly, we describe a new in-situ calibration technique requiring access to only the input end of the fibre–promising a way to image through flexible fibres. Secondly, we describe the design of a new optical element–an ‘optical inverter’–that can unscramble all modes in parallel, offering the potential of single-shot and super-resolution imaging through MMFs.
Optical tweezers have propelled the advancement of micro-manipulation. Yet not all materials can be optically
tweezed, and high laser intensities can be harmful to living organisms. We propose a method for using optical tweezers to
indirectly control particles which are freely diffusing in water. By optically trapping and controlling specially designed
actuators, the surrounding fluid can be locally manipulated in a predictable manner. This, in turn, offers materialindependent
hydrodynamic control over nearby free objects. We experimentally demonstrate control over translational
and rotational motion of individual objects, and multiple particles simultaneously.
Optical tweezers have contributed substantially to the advancement of micro-manipulation. However, they do have restrictions, mainly the limited range of materials that yield to optical trapping. Here we propose a method of employing optically trapped objects to manipulate the surrounding fluid and thus particles freely diffusing within it. We create and investigate a reconfigurable active-feedback system of optically trapped actuators, capable of manipulating translational and rotational motion of one or more nearby free objects.
Optical tweezers have played a significant role in the advancement of micro-manipulation. However, optically trappable objects are limited to a certain size and material range. To overcome these constraints, we propose a noncontact micro-manipulation technique, which uses optically trapped particles to locally manipulate the surrounding fluid and thus freely diffusing particles within it. We show that our method can be used to successfully suppress both translational and rotational Brownian motion of a free-floating object, using hydrodynamic interactions alone, in an easily reconfigurable setup.
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