Tiny, powerful lasers sculpt optical devices for giant telescopes

extremely large telescope

It makes sense that some of the giant telescopes being built by researchers across the world would require special optical technology to analyze distant space objects and light.

In one case researchers are looking at  using powerful lasers to carve out micron-sized light pathways in three dimensions with the idea of being able to more easily find and analyze deep space viewed through these giant telescopes

UK researchers are looking at using what they call ultrafast laser inscription (ULI) as a route to creating such astrophotonic devices. This relatively new technique for fabricating compact photonic devices makes use of ultrashort laser pulses.  Researchers describe two potential instruments--a highly dispersive waveguide array to measure the spectrum of the light emitted by celestial objects, and an integrated filter for removing unwanted atmospheric emissions, the researchers said.

Traditional electronic chip manufacturing techniques are not capable of making such three-dimensional devices, but ULI is able to sculpt them directly out of a glass substrate, the researchers said.  

They also note that the technique is not yet mature. The ULI fabricated light channels still lose light, which prohibits the waveguides from being longer than a few tens of centimeters. Moreover, the waveguides cannot be bent sharply, so devices have to be relatively large to allow for low-loss curves. Still, it may be possible to use ULI techniques to etch out tiny mirror surfaces that can be substituted for sharp waveguide bends, the researchers said.

"As things stand, building up-scaled versions of existing instruments would require impossibly stiff materials, impractically large optics and too much money," says Jeremy Allington-Smith, an astronomer at Durham University in England who co-authored a new paper published in the current issue of Optics Express demonstrates on how astrophotonics could be of particular benefit to the next generation of ground telescopes--the extremely large telescopes (ELTs) that will have mirrors 20 meters or larger. the paper was co-authored by colleagues Ajoy Kar and Robert Thomson of Heriot-Watt University in Edinburgh.

These gigantic instruments, like the planned 42-meter European ELT, will have the sensitivity to see galaxies at the edge of the universe, just as they were beginning to form, researchers said. There are at least 10 planned ELTs arcoss the globe. 

Such large telescopes will also be able to extract the age and possible origin of whole populations of stars in our own and nearby galaxies. This "galactic archaeology" requires collecting the light from many different objects and analyzing each of them separately. For an ELT, the number of objects to be simultaneously analyzed could be as high as 100,000, researchers said.  

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