The height of light: From a curiosity to a global phenomenon

Lasers have long energized our imaginations, bringing us light sabers and holodecks. And, more recently, even laser cats.

In reality, light-based technologies enable our modern lifestyles, from high-speed communications to observatories that glimpse at the universe’s origins. Underlying these innovations are fundamental properties, materials and designs.

Lasers, in particular, were famously described as a “solution looking for a problem” in 1960. That’s a phrase that could refer to many areas of discovery-driven research.

Importantly, in retrospect that phrase drives home an antithetical point: that we don’t know where solutions will come from.

Knowledge and inventions created by modern explorers of the unknown (i.e., scientists and engineers) often start out as curiosities and end up bringing our world closer together.

To celebrate lasers and other light sources, the U.S. National Science Foundation, which invests in the best and the brightest of those science and technology pioneers, recently put out an article series on light. Here are some excerpts.

Besides laser cats, where would you like to see light take us next?

Seeing more deeply with laser light

This mouse brain was imaged without imaging agents using photoacoustic microscopy. Credit: Junjie Yao and Lihong Wang, WUSTL

This mouse brain was imaged without imaging agents using photoacoustic microscopy. Credit: Junjie Yao and Lihong Wang, WUSTL

A human skull, on average, is about as thick as the latest smartphone. Human skin is only about three grains of salt deep.

Yet they still present hurdles for any kind of imaging with laser light. Why?

Laser light contains photons, or miniscule particles of light. When photons encounter biological tissue, they scatter. Corralling the tiny beacons to obtain meaningful details about the tissue has proven one of the most challenging problems laser researchers have faced.

Researchers at Washington University in St. Louis decided to eliminate the photon roundup completely and use scattering to their advantage.

The result: An imaging technique that penetrates tissue up to about 2.8 inches. This approach, which combines laser light and ultrasound, is based on the photoacoustic effect, a concept first discovered by Alexander Graham Bell in the 1880s.

Whispering galleries that speak loudly on disease detection

This fiber-making process is a lot like making cotton candy, except electric fields are involved. Credit: Joe Cheeney, University of California-Riverside

This fiber-making process is a lot like making cotton candy, except electric fields are involved. Credit: Joe Cheeney, University of California-Riverside

Commonly used health tests, such as pregnancy and blood sugar tests, involve putting a drop of fluid on a test strip, which is infused with a substance designed to detect a specific molecule.

The strip acts as a simple biosensor, a device that detects chemicals with the help of biological molecules such as proteins or enzymes.

These devices work, but are limited in scope and can be imprecise. Other health tests require time-consuming chemical reactions or bacterial culture.

Researchers at University of California-Riverside are creating a new biosensor that uses laser light, engineered viruses and advanced manufacturing techniques to more accurately detect the smallest amounts possible of biological molecules – in our food, in our water and even in our own blood.

Thanks to these technologies, biosensors of the future may be in fibers woven into clothes.

Building a better atomic clock

UK National Physical Laboratory cesium fountain clock. Credit: National Physical Laboratory, United Kingdom

UK National Physical Laboratory cesium fountain clock. Credit: National Physical Laboratory, United Kingdom

Prior to the mid-18th century, it was tough to be a sailor. At the time, sailors had no reliable method for measuring longitude, the coordinates that measure a point’s east-west position on the globe.

To find longitude, you need to know the time in two places—the ship you’re on, and the port you departed from. By calculating the difference between those times, sailors got a rough estimate of their position. The problem: The clocks back then couldn’t keep time well.

Today, time is as important to navigation, only instead of calculating positioning with margins of errors measured in miles and leagues, we have GPS systems that are accurate within meters. And instead of springs and gears, our best timepieces rely on cesium atoms and lasers.

An NSF-funded scientist at University of Alabama at Birmingham, who works on atomic clocks, was inspired by the story of John Harrison, an English watchmaker who toiled in the 1700s to come up with the first compact marine chronometer.

This device marked the beginning of the end for the “longitude problem” that had plagued sailors for centuries. He and other researchers now look for new ways to make clocks more accurate, diminishing any variables that might distort precise timekeeping.

Figuring out how to hide things

Three active sources cloak an incoming circular wave, creating a quiet zone. Credit: Fernando Guevara Vasquez, University of Utah.

Three active sources cloak an incoming circular wave, creating a quiet zone. Credit: Fernando Guevara Vasquez, University of Utah.

The idea of cloaking and rendering something invisible hit the small screen in 1966 when a Romulan Bird of Prey made a surprise attack on the Starship Enterprise on Star Trek. Not only did it make for good TV, it inspired budding scientists, offering a window of technology’s potential.

Today, pop culture has largely embraced the idea of hiding behind force fields and other materials. And so have mathematicians, scientists and engineers.

Researchers have developed new ways in which light can move around and even through a physical object, making it invisible to parts of the electromagnetic spectrum and undetectable by sensors. Additionally, mathematicians, theoretical physicists and engineers are exploring how and whether it’s feasible to cloak against other waves besides light waves.

In fact, they are investigating sound waves, sea waves, seismic waves and electromagnetic waves including microwaves, infrared light, radio and television signals.

Letting go with lasers

A laser detaches delicate nanostructures from a stamp in a new way to create nanocircuits. Credit: Jorge E. Correa and Placid M. Ferreira, mechanical science and engineering, University of Illinois at Urbana-Champaign.

A laser detaches delicate nanostructures from a stamp in a new way to create nanocircuits. Credit: Jorge E. Correa and Placid M. Ferreira, mechanical science and engineering, University of Illinois at Urbana-Champaign.

Plenty of parents dread hosting a party that involves confetti.  Just like glitter, it often finds its way to everything else you touch. Why do small objects stick to things when larger objects don’t?

It’s all about the physics of letting go. When you place your hand around a smooth soda can, you exert a force through your grip in order to pick it up; if no force is applied, gravity keeps the can in place as your hand raises without the can.

The two basic principles of volume and weight that make picking up a soda can easier than handling a speck of glitter continues to apply as objects become smaller.

With these principles in mind, University of Illinois at Urbana-Champaign researchers are using lasers to “break” adhesive forces to manufacture objects too small for the human eye to see.

Solving futuristic mysteries

Solving mysteries with light. Credit: Amina Khan, NSF.

Solving mysteries with light.
Credit: Amina Khan, NSF.

Cutting-edge forensic tools rely heavily on laser and photonics research to unravel mysteries.

To illustrate this point, an NSF animator imagined a future-tech scenario where investigators must use light-based equipment to solve a whimsical (potential) crime.

More at NSF.gov/light.


batesSarah Bates is a public affairs specialist with the National Science Foundation (NSF), where she oversees communications for the Directorate for Engineering. She works with a team of talented science communicators to tell stories about fundamental science and engineering research.

 

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