How to Create the World's Sharpest Laser

Researchers from the Physikalisch-Technische Bundesanstalt (PTB), which is the national metrology institute of Germany, have broken the record for the sharpness of a laser by building one that has a linewidth (the width of a laser's optical spectrum) of just 10 millihertz (0.01 hertz).
The laser is stable for 11 seconds before the light waves are desynchronized, but due to them oscillating approximately 200 trillion times per second, in this time the "wave train emitted has already attained a length of approx. 3.3 million kilometers. This length corresponds to nearly ten times the distance between the Earth and the moon," the team said a press release.
In order to do this, the scientists used a Fabry-Pérot silicon resonator, which consists of a fixed double cone with two mirrors facing each other inside. To optimize the laser, the researchers then began to rid the system of any interference by eliminating the movement in the mirrors caused by sound, seismic waves, or temperature fluctuations.They then optimized the resonator. In order to prevent any thermal motions of the atoms themselves, they cooled the silicon in the resonator to the point that Brownian motion was minimized — which in this case was -150° Celsius (-238° Fahrenheit).

A Solution to a Problem

A 'sharper' laser increases the accuracy of whatever system it is put into by making it more precise. Currently, the scientists are using the technology to measure ultracold atoms and increase the quality of time telling. According to Thomas Legero, a member of the team, "the smaller the line-width of the laser, the more accurate the measurement of the atom's frequency in an optical clock. This new laser will enable us to decisively improve the quality of our clocks."

However, the possible uses of this technology could extend much further. These lasers could be used to test Einstein's theory of relativity more accurately, as the two lasers that were fired into space that gave evidence to the discovery were far cruder.

This is one of many advancements that have been made recently in the field of laser technology. NASA has developed their Lunar Orbiter Laser Altimeter (LOLA) in order to make accurate topographical maps of the moon, while the world's largest laser — the European XFEL — is primed to reveal the secrets of the atomic world.

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