Real-time wavefront phase retrieval from intensity-based measurements-Placement
Internship 6 months Oberpfaffenhofen, Germany
Uploaded 29 Apr 2020
It is conventional for satellites and Earth-based stations to communicate using radio transmissions. At these wavelengths the atmosphere is transparent. However, if these transmissions could be performed at optical wavelengths, the channel would benefit from having improved security. Free-space optical communication would also dramatically increase the bit rate of the signal. By having a number of optical stations around the world, this technology would enable worldwide high-speed internet. A further application of this technology is that, in the future, it will allow for high-speed data communications between the Earth and deep space missions.
Optical wavefronts become perturbed as they travel through atmospheric turbulence. The source of this image blurring is the constant mixing of different temperatures throughout the atmosphere, causing the wavefront to travel through regions of varying refractive index. For Earth-satellite communications, these aberrations are so strong that they destabilize the signal and prevent a link from being established.
The effects of atmospheric turbulence must be mitigated if we are to realize the benefits of free-space optical communications. To do this, we propose using an Adaptive Optics (AO) system that is capable of measuring the strength of wavefront perturbations across a 2D field of view. This information can then be relayed to a Deformable Mirror (DM) – situated in the optical path – that changes its shape to correct for the measured perturbations. The wind drives atmospheric turbulence and so the AO system must update the shape of its DM thousands of times a second.
The proposed optical stations will be situated around the world and must operate at all times. We expect strong turbulence conditions – especially during the day. At such strengths, conventional wavefront sensors suffer from non-linearity and inaccurate measurements. The goal of this project is to investigate an alternative wavefront sensor that addresses these issues directly. There will be a strong focus on optimising the efficiency of any data analysis technique developed. Novel ideas will be encouraged.
The student will have access to advanced software and high performance computing hardware. It is hoped that they will test their new concepts using our AO demonstrator.
- theoretical analysis of optical wavefront propagation
- evaluation of measurements and analysis of the results
- writing and maintaining advanced software packages
- concise presentation of results and further ideas to the department
- investigation into efficiency optimization of iterative fitting algorithms
- possible participation in experimental on-field measurement campaigns
- study in the direction of physics, space sciences or optical engineering
- experienced in MATLAB and Python programming languages
- understanding of optical propagation and wavefront modelling
- experienced in optical alignment