Such light amplification has been disfavored because the stimulated emission is also accompanied by constant spontaneous emission by the same atoms. This is an improvement on direct detection, which is based only on the original photon (without an amplifier), improves the resolution of the telescope without increasing its size. These daughter photons also obey the initial diffraction limit, but by their mere number they allow for a better measurement of the angle at which the original, astronomical photon has crossed the telescope aperture. These stimulated photons are identical to the original photon, both in direction and in wave length. When a photon, arriving from a star, crosses the telescope aperture, it reaches a light amplifier, a medium of atoms, which responds by stimulating the emission of many additional photons. The experiment is based on amplification of photons. In mid-sized telescopes or space telescopes, limited by launcher volume, resolution is still an issue. Indeed, the giant telescopes being built in recent decades provide very high resolution. Since in astronomy we observe natural light that is out of our control, we cannot reduce the wave length, but we can increase the telescope aperture. One is reduction of the wave length, for example by illuminating the object by blue light, instead of red the other is to increase the telescope aperture. There are two basic ways to reduce diffraction and improve resolution, as set by the uncertainty principle of quantum mechanics. Thus, two nearby stars will look like overlapping fuzzy spots, which we cannot distinguish any more. The original angle of the light is blurred, causing the observed object, in this case a star, to look like a fuzzy spot. The resolution limit is set by diffraction: light rays diffract and scatter around objects in their path, in this case the telescope mirror, as they travel to the focal plane, where the detector (camera) is. The resolution of a telescope – how sharp its images are – is the smallest angle between two observed objects, where they can still be visibly separated. Gal was also interviewed in " Three who know" in Kan. In a feature issue on Astrophotonics (read the paper here). Their work on increasing a telescope’s resolution without enlarging its mirror was featured in " Mada Gadol, BaKtana". Erez Ribak from our Department, was published in the Journal of the Optical Society of America B
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