Researchers at the Technion achieved an improvement in the separation capacity of telescopes without increasing the telescope's mirror

The researchers developed an amplifier - a medium containing atoms that the photon coming from space passes through after the telescope key. The photon hitting the atom forces the atom to release a large number of photons identical to the original photon The improvement in resolution will benefit any telescope, especially medium-sized telescopes, and in particular space telescopes

A new article heralds a significant improvement in the resolving power of telescopes. The research was conducted by the doctoral student Gal Gompel under the guidance of Dr. Erez Ribak from the Faculty of Physics at the Technion and was published inJournal of the Optical Society of America B - Journal of the American Optical Society - in an issue dedicated to astrophotonics.

The separation capacity of telescopes, i.e. their resolution - the level of sharpness of the image obtained in them - is limited in part by the smallest angle between two observed objects in which they still appear separate (and not as one object). The ability to separate, for its part, is determined by the phenomenon of diffraction: the light waves are scattered around obstacles in their path - the edge of the telescope mirror in this case - and the light penetrates the area where there was supposed to be a shadow. This phenomenon means that the observed object (a star, for example) will not appear to us as a sharp point but as a set of rings, and two close objects will appear to us as two ring-systems that overlap each other. In other words, we cannot differentiate between the two objects.

Two ways to reduce diffraction - that is, to improve the ability to separate - is to reduce the wavelength (as in microscopy) and to increase the diameter of the mirror. Since in astronomy we are based on the natural light that is not under our control, we cannot reduce the wavelength, so all that remains is to increase the mirror, i.e. the aperture of the telescope. Indeed, the huge telescopes built in recent decades provide a very high separation capacity; However, in medium-sized telescopes, such as those launched into space and therefore limited in size for logistical reasons, the separation problem is still very significant.

Calculation of the transition angle of the photon

The experiment carried out by the Technion researchers is based on the amplification of photons (particles of light): when a photon coming from space passes through the aperture of the telescope, it enters the amplifier - a medium containing atoms; The photon hitting the atom forces the atom to release a large number of photons identical to the original photon. These are called forced photons, and they move in the same direction as the original photon, and at the same wavelength. These photons are also subject to the diffraction phenomenon, but their large number makes it possible Restore, according to their impact on the detector and based on mathematical and statistical calculations, the The transition angle of the original photon (the astronomical) in the telescope key. This is in contrast to direct photography based on the original photon only (in the absence of an amplifier). The innovative method increases the separation capacity of the telescope without increasing its diameter.

The existing reluctance to use photon amplification is due to the fact that the forced emission is also accompanied by a strong and constant spontaneous emission that increases the noise in the system and therefore reduces the ability to separate. That's why the researchers used the method that also measures the spontaneous emission. In a laboratory experiment they hid the light of the "star" alternately, so that part of the time they measured only the spontaneous emission, and another part of the time was used to measure both emissions, the spontaneous and the forced. The image of the star is obtained by subtracting the two measurements and thus neutralizes the noise and leaves only the relevant information. This is the first time such an experiment has been performed with white light, since most photon amplifiers (such as those present in lasers) only work at one wavelength (color).

The researchers point out that "one of the possible disadvantages of the proposed method is the loss of sensitivity in the produced images, but this is a worthy price for the jump in the level of angular separation. Furthermore, the loss of sensitivity can be partially overcome by increasing the exposure times, i.e. extending the observation time."

for the article in Journal of the Optical Society of America B 

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