PhD researcher investigates techniques to help beat astronomy’s nemesis: the Earth’s atmosphere

Oana, a PhD student on the CEPS CDT at University of Cambridge, is investigating the application of liquid crystals as the medium of correction, rather than the tried-and-tested deformable mirror. This research has won her a 2023 CAPE Acorn Postgraduate Research Award (CAPA). The Award, presented by the Centre for Advanced Photonics and Electronics (CAPE), is in recognition of her project titled Blue Phase Liquid Crystal Phase Modulators For Astronomical Adaptive Optics.

“Using liquid crystals is cheaper, provides longer lifespans and can be made to higher resolutions (as we can see from modern display technology such as televisions and smartphones).” - Oana Niculescu

Astronomical observation from Earth is hindered by having to look through the atmosphere. Small changes in temperature and wind velocity add distortion images. This problem has been solved over the years by using purpose-built sensors to measure the atmospheric aberration, before correcting it with a deformable mirror that changes shape to invert the effect of this distortion.

“This works very well, but this type of mirror is costly to produce,” says Oana. “My intention is to use liquid crystals as the medium of correction rather than a mirror.”

IMAGE A: Liquid crystal blue phase depicting platelets (10 microns).

Liquid crystals are a versatile material used in light beam manipulation and much progress has been made in using the material in adaptive optics. But there are challenges in fabrication. What hasn’t been attempted so far in astronomy, says Oana, is using liquid crystal devices that can reach kilohertz refresh rates (the number of times per second the device can predictably affect light coming from the telescope) to provide a distortion-free image.

“I aim to use the blue phase of liquid crystals, which have a complex structure that is only stable over a very short temperature range (less than 1ºC) but can be increased by polymerisation (a process by which the said structure is 'fixed' into place) to work over a range of about 40ºC.

“This is a fiddly process, but using liquid crystals is cheaper, provides longer lifespans due to the lack of moving parts, and can be made to higher resolutions (as we can see from modern display technology such as televisions and smartphones).”

“This would provide an alternative to current telescopes and could be much more attractive to the amateur astronomer attempting to take pictures of the night sky,” she added.

IMAGE B: diagram showing the functionality of an adaptive optics system, with Oana's blue phase device acting as a correcting element.

Find out more

Read the full article, published 23 Jun 2023: http://www.eng.cam.ac.uk/news/postgrad-research-will-investigate-technique-help-beat-astronomy-s-nemesis-earth-s-atmosphere.

Oana Niculescu: http://www-g.eng.cam.ac.uk/CMMPE/Team/OanaNiculescu.html

Oana is part of the Centre of Molecular Materials for Photonics and Electronics (CMMPE) research group. Her PhD is titled Liquid Crystal Adaptive Optics System for Ground-Based Telescopes.

For her Master of Research (MRes) degree, Oana completed two projects under the Connected Electronic and Photonic Systems (CEPS) programme at Cambridge. These were:

• Nanophotonics for enhancing optical absorptions in optoelectronic devices
• Liquid crystal lenses for head-up displays in automotive applications.

Images:

A) Liquid crystal blue phase depicting platelets (10 microns). Part of Oana's (left) research aims to fabricate blue phases with larger platelets to increase the precision in the operation of the devices. Credit: © Rachel Garsed 2023, CMMPE PhD graduate.

B) Diagram showing the functionality of an adaptive optics system, with Oana's blue phase device acting as a correcting element. Image credit: © Oana Niculescu 2023.