A Structured Laser Beam

Sometimes, oppor­tunities fall into our laps when we’re least expecting them. A team of CERN surveyors, in colla­boration with the Institute of Plasma Physics in Prague (IPP), has developed a pioneering laser beam while working on a parti­cularly chal­lenging alignment system. “While developing the align­ment system for the HIE-ISOLDE acce­lerator, we discovered that the system generating a structured laser beam had as­tonishing optical pro­perties”, explain Jean-Christophe Gayde and Miroslav Šulc, the system’s inventors. “We didn’t initially plan to develop a generator for this kind of laser beam, but the results of our research were very encouraging.”

Example of a transverse cross-section of a beam produced by the structured laser beam. The central axis, which is very dense, is surrounded by several halos of light. The darkness between the halos is absolute, creating a strong contrast. This contrast makes it possible to measure the position of the halos of light with great precision, and thus to validate the measure­ments using the principle of redundancy. (Source: CERN / IPP)

Continuing with the unplanned project, the two teams developed the “structured laser beam”, which is extremely innovative in that it produces beams that are almost non-dif­fractive. The central axis of the beams diverges very little, even over a distance of several hundred metres: 200 meters from the system, the central axis of the laser measures only a few milli­meters in diameter, hardly more than when it left the generator. The systems available on the market produce such beams over a distance of only a few metres.

Its excep­tional proper­ties give the structured laser beam potential in many fields, including communi­cation, medicine, physics and, above all, metrology. “At CERN, this laser would be a valuable tool for aligning magnets, thanks to its low central diver­gence”, says Jean-Christophe Gayde. “And it has one parti­cularly remarkable charac­teristic: in certain conditions, the beam recon­structs itself after meeting an obstacle. In other words, its halo can reconstruct the central beam after it has passed the obstacle, in a similar way to a Bessel beam.”

The structured laser beam can be produced from source laser beams in a wide range of wave­lengths and its geometry can be easily adapted – diameter of the central divergence, number of circles in the halo, etc.. The generator itself can be very compact with the size of a matchbox and adjustable, while still being fairly inex­pensive. “We filed a patent appli­cation in May 2018 and since then we’ve been in talks with several potential clients in Europe to establish colla­borations”, says Amy Bilton, the knowledge transfer officer (KTO) respon­sible for the project within CERN’s Knowledge Transfer group. “Studies are ongoing and more tests are needed, but the structured laser beam could consi­derably improve some applications that use light beams, in particular laser beams.”(Source: CERN)

Link: “Structured Laser Beam”, Knowledge Transfer Center, CERN, Geneve, Switzerland


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