3,665 research outputs found
Low noise single aperture multimode monopulse antenna feed system Patent
Development and characteristics of low-noise multimode monopulse antenna feed system for use with microwave communication equipmen
Transmission of natural scene images through a multimode fibre
The optical transport of images through a multimode fibre remains an
outstanding challenge with applications ranging from optical communications to
neuro-imaging. State of the art approaches either involve measurement and
control of the full complex field transmitted through the fibre or, more
recently, training of artificial neural networks that however, are typically
limited to image classes belong to the same class as the training data set.
Here we implement a method that statistically reconstructs the inverse
transformation matrix for the fibre. We demonstrate imaging at high frame
rates, high resolutions and in full colour of natural scenes, thus
demonstrating general-purpose imaging capability. Real-time imaging over long
fibre lengths opens alternative routes to exploitation for example for secure
communication systems, novel remote imaging devices, quantum state control
processing and endoscopy
Turning Optical Complex Media into Universal Reconfigurable Linear Operators by Wavefront Shaping
Performing linear operations using optical devices is a crucial building
block in many fields ranging from telecommunication to optical analogue
computation and machine learning. For many of these applications, key
requirements are robustness to fabrication inaccuracies and reconfigurability.
Current designs of custom-tailored photonic devices or coherent photonic
circuits only partially satisfy these needs. Here, we propose a way to perform
linear operations by using complex optical media such as multimode fibers or
thin scattering layers as a computational platform driven by wavefront shaping.
Given a large random transmission matrix (TM) representing light propagation in
such a medium, we can extract a desired smaller linear operator by finding
suitable input and output projectors. We discuss fundamental upper bounds on
the size of the linear transformations our approach can achieve and provide an
experimental demonstration. For the latter, first we retrieve the complex
medium's TM with a non-interferometric phase retrieval method. Then, we take
advantage of the large number of degrees of freedom to find input wavefronts
using a Spatial Light Modulator (SLM) that cause the system, composed of the
SLM and the complex medium, to act as a desired complex-valued linear operator
on the optical field. We experimentally build several
complex-valued operators, and are able to switch from one to another at will.
Our technique offers the prospect of reconfigurable, robust and
easy-to-fabricate linear optical analogue computation units
- …