Scientists use lasers to cool small areas of film to absolute zero for highly sensitive sensors

Researchers at the University of Basel have successfully developed a new method that allows a small area of thin film to be cooled very close to absolute zero (minus 273.15 degrees Celsius) using only lasers. According to reports, this highly cooled film may be used for extremely sensitive sensors in the future.

German astronomer Johannes Kepler proposed the idea of a solar sail 400 years ago, a type of spacecraft that would use the pressure of sunlight for cosmic voyages and could be used to carry ships through space. He believed that when light is reflected off an object, a force is exerted. He also used this theory to explain why comets' tails point away from the sun.

The team was led by Dr. Philipp Treutlein and Dr. Patrick Potts. Their results have just been published in the scientific journal Physical Review X.

No measurement feedback

Today, atoms and other particles are slowed down and cooled by the power of light. A complex instrument is usually required for this purpose. What's special about the team's approach is that they achieved this cooling effect without taking any measurements.

According to the laws of quantum mechanics, feedback loops often require measurement processes that cause quantum states to change, causing interference. To prevent this from happening, researchers at the University of Basel have created a system known as a "coherent feedback loop," in which lasers act as both sensors and dampers.

They achieved this by suppressing and cooling the thermal vibrations of a silicon nitrate film about half a millimeter in size. In their experiments, the researchers aimed a laser beam at a thin film and fed the light reflected from the film into a fiber-optic cable. During this operation, the vibration of the membrane produces a small change in the oscillating phase of the reflected light.

Information about the immediate motion state of the membrane contained in the oscillating phase is then utilized, with a time delay, to apply the right amount of force to the membrane at the right moment using the same laser. The researchers used a 30-meter-long fiber-optic cable to achieve an optimal delay of about 100 nanoseconds.

Near absolute zero

A postdoctoral researcher at the University of Basel in Switzerland and his colleagues cooled the membrane to 480 microKelvin, or less than a thousandth of a degree above absolute zero.

The next stage will be to refine the experiment so that the membrane reaches its quantum-mechanical ground state of oscillation - the lowest temperature that can be reached. The emergence of the so-called membrane extrusion state should be conceivable.

Because of their ability to improve measurement accuracy, this state is particularly meaningful for sensor structures. In the future, atomic force microscopes, which are used to scan surfaces at nanometer resolution, will be a potential application for such sensors.

Source: OFweek