#laser cooling

[silicontrivance]

“Butterflies and Beamsplitters”

llustration I made for one of my favorite professors who taught me about laser cooling, which blew my mind. The glassware and lasers are inspired by the insane amount of optics he had in his lab. The body pattern is based off a graph he made in one of his papers.

[blossoms-and-petrichor]

wait till tumblr hears about laser cooling. one must imagine sodium happy.

[katenepveu]

if you like counterintuitive physics with a sprinkling of life-in-a-lab anecdotes, Chad Orzel (my spouse) has an article about the early history of laser cooling (part 1 of 3) out today, which should be free to read (I did not get a paywall). I am admittedly biased, but I think it's neat.

Cold: how physicists learned to manipulate and move particles with laser cooling – Physics World

The early history of laser cooling is a tale of three Nobel prizes and plenty of hard work, as Chad Orzel reveals

[keystonewarrior]

Have y'all heard about laser refrigeration?

Cooling stuff down using lasers?

The theory parts are almost a hundred years old. The book I'm reading is from 1997.

Neato stuff.

[materialsscienceandengineering]

Running an LED in reverse could cool future computers

In a finding that runs counter to a common assumption in physics, researchers at the University of Michigan ran a light emitting diode (LED) with electrodes reversed in order to cool another device mere nanometers away.

The approach could lead to new solid-state cooling technology for future microprocessors, which will have so many transistors packed into a small space that current methods can't remove heat quickly enough.

"We have demonstrated a second method for using photons to cool devices," said Pramod Reddy, who co-led the work with Edgar Meyhofer, both professors of mechanical engineering.

The first -- known in the field as laser cooling -- is based on the foundational work of Arthur Ashkin, who shared the Nobel prize in Physics in 2018.

Read more.

[suryaray-blog]

Laser cooling of semiconductors by annihilating excitations

#SuryaRay #Surya A visible-light laser rapidly cools some semiconductors by 40 degrees. http://dlvr.it/2rFbxY @suryaray

[txchnologist]

Lasers Eyed To Cool Satellite Cameras, Night-Vision Goggles

by Charles Q. Choi

Instead of using lasers to heat targets, now researchers are shooting light beams that cool what they shine on.

Normal refrigerators use motors to pump compressed gas through tubes lining them. As these gases expand, they remove heat from inside the appliance.

Laser refrigerators

The technique whereby lasers can be used to cool targets is called optical refrigeration. It works like this: lasers focused on an object can make it fluoresce, which causes it to lose energy as light and decrease in temperature. Optical refrigerators potentially have a number of advantages over conventional units. Since they require neither gas nor moving parts, they can be more compact, free from vibration and not prone to mechanical failure.

Although optical refrigeration of solids was first predicted in 1929, it was not seen experimentally until 1995 with glassy and crystalline materials doped with rare earth metals. In less than 20 years, research using these materials has advanced optical refrigeration enough to achieve cooling from room temperature to about -260 degrees Fahrenheit. Still, that is significantly warmer than the -321 degrees F at which liquid nitrogen boils.

Scientists wanted to accomplish optical refrigeration with semiconductors instead of rare-earth-metal-doped glasses and crystals. Semiconductors are the basis of modern electronics, and so researchers strove to directly integrate optical refrigerators into existing devices. Calculations also suggested that optical refrigerators that used semiconductors could achieve much lower temperatures. However, attempts to develop the units based on the semiconductor gallium arsenide failed. Although this semiconductor does fluoresce when hit by lasers, the emitted light does not escape from the material efficiently, so it heats up instead of cooling down.

Now, using the semiconductor cadmium sulfide, researchers have shown that lasers could trigger cooling, from about 62 degrees F to about -9 degrees F.

"This came to us as a surprise," says Qihua Xiong, a physicist and optical spectroscopist at Nanyang Technological University in Singapore. He and his colleagues were originally investigating how the semiconductor responds to lasers for completely different purposes.

The laser excites electrons in the semiconductor, dislodging them and leaving behind a "hole." This electron-hole pair is known as an "exciton," which is surrounded by vibrating atoms. Extremely strong interactions between the excitons and bundles of these vibrations, known as phonons, lead to fluorescence that cools the semiconductor very efficiently.

"It was a very welcome surprise to see that these types of bulk semiconductors can be laser-cooled," says University of New Mexico physicist Mansoor Sheik-Bahae, who did not participate in this study. "Initially we were skeptics, but when we looked at their methodology — the way they measured temperatures, the way they did experiments — it looked very solid to us."

The researchers achieved cooling using specific wavelengths of green light. They precisely engineered the semiconductor into thin ribbons less than 10 microns wide, or less than one-tenth the width of a human hair, and only 100 nanometers thick, less than a wavelength of visible light, to confine the interactions within the semiconductor and accomplish cooling.

"People may think the nanobelt is too small, that it is not going to be useful," Xiong says. But, by showing that laser cooling of semiconductors is possible, more practical devices may emerge "once we find better materials, pushing the cooling to bulk materials."

Important future uses

"The big potential users of this cooling technology are night-vision goggles, and infrared cameras on satellites, where weight is very important and you would not want the motors and pumps and vibrations that come with regular coolers if you can," says Richard Epstein, a University of New Mexico physicist and CEO at technology startup ThermoDynamic Films, who did not take part in this research.

"There are still lots of questions of why laser cooling of nanobelts works so well here — research should try different thicknesses and different-shaped structures to understand why laser cooling was so successful here," Epstein says. "On a practical level, one would then like to start incorporating these cooling cadmium sulfide nanobelts with some actual electronics."

The researchers want to see if semiconductor optical refrigerators can reach far lower temperatures, even reaching down to that of liquid helium, which is at least -452 degrees F, just a few degrees above absolute zero.

"Rare-earth-doped glasses or crystals always reached a fundamental limit of about 110 Kelvin (-261 degrees F), while semiconductors are our hope to reach liquid helium temperature by laser cooling," Xiong says.

The scientists detailed their findings in the Jan. 24 issue of the journal Nature.

Charles Q. Choi has written for Scientific American, The New York Times, Wired, Science and Nature, among others. In his spare time, he has traveled to all seven continents, including scaling the side of an iceberg in Antarctica, investigating mummies from Siberia, snorkeling in the Galapagos, climbing Mt. Kilimanjaro, camping in the Outback, avoiding thieves near Shaolin Temple and hunting for mammoth DNA in Yukon.

[sciencesoup]

Laser Cooling and Quantum Computers

Lasers aren’t just used to destroy things—a team of Yale physicists are working towards using them for a completely different purpose, employing a technique called laser cooling to contribute to the development of quantum computers. Quantum computers are devices that could theoretically use the laws of quantum mechanics to solve computational tasks at incredible speeds, and researchers have previously tried to create “qubits” (information bits to use in basic quantum processors) in two different ways. Firstly by using individual atoms, which don’t communicate as strongly as needed; and secondly by using “artificial atoms”, a combination of billions of atoms that behave as one, which are subject to interference. “It’s a kind of Goldilocks problem,” says Yale physicist David DeMille. “[But] molecules made up of a few different atoms could be just right.” However, the kinetic energy of molecules makes them move, rotate and vibrate so much that it’s difficult to manipulate them without disturbing their quantum properties. They therefore need to be slowed down—using laser cooling. The Yale team hit molecules with laser beams (i.e., streams of photons) in such a way that the laser's energy was absorbed and then re-emitted, taking kinetic energy with it and thus reducing the molecule’s momentum. To make the molecules useful in the creation of qubits, the team is trying to cool them down to absolute zero (−273.15 degrees Celsius).

Read More on NatureNews