Abstract
We present a GPU accelerated toolbox for shaping the light propagation through multimode fibre using a spatial light modulator (SLM). The light is modulated before being coupled to the proximal end of the fibre in order to achieve arbitrary light patterns at the distal end of the fibre. First, the toolbox optimises the acquisition time of the transformation matrix of the fibre by synchronous operation of CCD and SLM. Second, it uses the acquired transformation matrix retained within the GPU memory to design, in real-time, the desired holographic mask for on-the-fly modulation of the output light field. We demonstrate the functionality of the toolbox by acquiring the transformation matrix at the maximum refresh rate of the SLM - 204 Hz, and using it to display an on-demand oriented cube, at the distal end of the fibre. The user-controlled orientation of the cube and the corresponding holographic mask are obtained in 20 ms intervals. Deleterious interference effects between the neighbouring points are eliminated by incorporating an acousto-optic deflector (AOD) into the system. We remark that the usage of the toolbox is not limited to multimode fibres and can be readily used to acquire transformation matrix and implement beam-shaping in any other linear optical system.
Highlights
The last decade witnessed an outstanding effort in bio-medical photonics to increase penetration depth while minimising collateral damage, whether caused by radiation or mechanical influences [1, 2]
The results of the transformation matrix are stored in GPU memory and the data can be used to generate arbitrary patterns at the distal end of the fibre in real-time
The interference effects between neighbouring points at the output facet were addressed by implementation of acousto-optic deflector (AOD) into the system
Summary
The last decade witnessed an outstanding effort in bio-medical photonics to increase penetration depth while minimising collateral damage, whether caused by radiation or mechanical influences [1, 2]. We resolve the synchronisation issues in the toolbox by harnessing the computational power of modern GPUs that are able to deliver the mask on the SLM screen without substantial delay This allows us to acquire the transformation matrix at the maximum possible refresh rate of our SLM (Boulder Nonlinear Systems 512x512). We achieve a complete removal of the interference in the output patterns by implementing an acousto-optic deflector (AOD) into the setup [6] This allows to display the fibre output points in a time-discrete manner, preventing interference. We demonstrate the functionality of the GPU toolbox by implementing a routine to generate, in real-time, an interference free, fully interactive ‘rotating’ cube made of 120 points at the distal end of the MMF fibre. We believe the toolbox will enable a wider uptake of this emergent technology by MMF community
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