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Rollable mirrors may enable space telescopes ‘orders of magnitude more sensitive’
Photonic ‘time crystals’ could improve lasers and wireless communication
Scientists have created photonic ‘time crystals’ capable of amplifying microwaves that could improve wireless communications, integrated circuits and lasers. While conventional crystals have a
structural pattern that repeats in space, a ‘time crystal’ has a pattern that repeats in time. So far, research on photonic time crystals has focused on bulk materials – 3D structures – but experiments did not get past model systems to practical applications. Now, a team including researchers from Aalto University, the Karlsruhe Institute of Technology (KIT), and Stanford University, have tried a new approach: building a two- dimensional photonic time crystal, known as a metasurface. Their work has been described in Science Advances. “We found that reducing the dimensionality
from a 3D to a 2D structure made the implementation significantly easier, which made it possible to realise photonic time crystals in reality,” said Xuchen Wang from KIT, the study’s lead author. The new approach enabled the team
to fabricate a photonic time crystal and experimentally verify the theoretical predictions about its behaviour. “We demonstrated for the first time that photonic time crystals can amplify incident light with high gain,” said Wang.
EPIC welcomes new president
Basil Garabet, the president and CEO of NKT Photonics, has replaced Benno Oderkerk as president of EPIC, the European Photonics Industry Consortium. “As an organisation, we have persevered
through challenging times and now it’s crucial that we forge new bridges to ensure that we can gather input from every voice,” said Garabet at EPIC’s recent AGM in Helsinki, Finland.
A new method for fabricating large, high- quality mirrors for space telescopes can make them thin enough to be rolled up and stored inside a launch vehicle. In Applied Optics, the researchers describe
creating the 30cm-diameter parabolic membrane mirror prototypes using chemical vapour deposition (CVD), growing them on a rotating liquid inside a vacuum chamber. The prototypes are much thinner than the mirrors previously deployed in space telescopes, and could be scaled up to similar sizes. “Launching and deploying space telescopes is a complicated and costly procedure,” said Sebastian Rabien from the Max Planck Institute for Extraterrestrial Physics in Germany. “This new approach – which is very different from typical mirror production and polishing procedures – could help solve weight and packaging issues for telescope mirrors, enabling much larger, and thus more sensitive, telescopes to be placed in orbit.” He explained that this is the first time CVD has been used to create parabolic membrane mirrors with the optical qualities suited to astronomy. A rotating container filled with a small amount of liquid was added to the inside of a CVD vacuum chamber. The liquid forms a perfect parabolic shape onto which the polymer can grow, forming the mirror base. When the polymer is thick enough, a reflective metal layer is applied to the top via evaporation and the liquid is washed away. While the work only demonstrates the
feasibility of the new fabrication method, it lays the groundwork for larger, cheaper packable mirror systems, said Rabien. “It could make lightweight mirrors that are 15 or 20 metres in diameter a reality, enabling space-based telescopes that are orders of magnitude more sensitive than ones currently deployed or being planned,” he explained. The new membrane-based mirrors could also be used in adaptive optics systems – used to improve the performance of optical systems by using a deformable mirror to compensate for distortion in incoming light. Because the surface of the new membrane mirrors is deformable, these mirrors could be shaped with electrostatic actuators to create deformable mirrors more economically than by conventional methods. Next, the researchers plan to apply more sophisticated adaptive control to study how well the final surface can be shaped and how much of an initial distortion can be tolerated.
‘Hybrid tech’ puts entangled quantum light source on a chip
A team of researchers from Leibniz University Hannover, the University of Twente and Dutch start-up QuiX Quantum has integrated an entangled quantum light source on a chip for what they say is the first time. The work, reported in Nature Photonics, used a novel “hybrid technology” that combines a laser made of indium phosphide and a filter made of silicon nitride on a single chip, to reduce the source size by over 1,000 times. This enables reproducibility, scaling, stability over time, and potential mass production – all of which are necessary for real-world applications, including quantum processors.
On-chip photonics has become a leading
Benno Oderkerk (leſt) stepped down aſter six years as EPIC’s president and welcomed Basil Garabet to the role
6 Electro Optics May 2023
platform for processing optical quantum states, as it is compact, robust, and allows for the arrangement of many elements on a single chip. Quantum light sources are used to generate light quanta, or photons, that function as quantum bits, or qubits. The researchers have developed an electrically excited, laser-
integrated photonic quantum light source that fits entirely on a chip and can emit frequency- entangled qubit states. Previously, quantum light sources required external, off-chip and bulky laser systems, which limited their use in the field. The team overcame these limitations by exploiting different integrated platforms and a novel chip design. They believe this could lead to programmable photonic quantum processors, with the quantum light source as a fundamental component. “Now we can integrate the laser with other components on a chip so that the whole quantum source is smaller than a one-euro coin,” said Dr Raktim Haldar, a research fellow at the Leibniz University Hannover’s Institute of Photonics. “Our tiny device could be considered a step towards quantum advantage on a chip with photons. Unlike Google, which currently uses super-cold qubits in cryogenic systems, the quantum advantage could be achieved with such photonic systems on a chip even at room temperature.”
@electrooptics |
www.electrooptics.com
Xuchen Wang/Aalto University
Max Planck Institute for Extraterrestrial Physics
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