Nav: Home

Making lasers cool again

October 31, 2016

Once the preferred weapon of B-movie madmen and space-fiction heroes alike, the laser -- a device that generates an intense beam of coherent electromagnetic radiation by stimulating the emission of photons from excited atoms or molecules -- has grown a bit domesticated of late.

These days, it has a steady job in industry, and spends its spare time printing documents in home offices and playing back movies in home theaters. Here and there it pops up in medical journals and military news, but it's basically been reduced to reading barcodes at the grocery checkout -- a technology that's lost its mojo.

But lasers are still cool, insists Sushil Kumar of Lehigh University, with vast potential for innovation we've just begun to tap. And with support from the National Science Foundation (NSF), he's on a mission to prove it.

Kumar, an associate professor of electrical and computer engineering, focuses specifically on lasers that arise from a relatively unexploited region in the electromagnetic spectrum, the terahertz (THz), or far infrared, frequency. A researcher at the forefront of THz semiconductor 'quantum-cascade' laser technology, he and his colleagues have posted world-record results for high-temperature operation and other important performance characteristics of such lasers.

His goal is to develop devices that open up a wide array of possible applications: chemical and biological sensing, spectroscopy, detection of explosives and other contraband materials, disease diagnosis, quality control in pharmaceuticals, and even remote-sensing in astronomy to understand star and galaxy formation, just to name a few. (Pretty cool stuff...the folks back at the checkout line would be impressed.)

Yet despite the known benefits, Kumar says that terahertz lasers have been underutilized and underexplored; high cost and functional limitations have stymied the innovation that would lead to such usage. Kumar, however, believes he's on track to truly unleash the power of THz laser technology; he recently received a grant from the NSF, Phase-locked arrays of high-power terahertz lasers with ultra-narrow beams, with a goal of creating THz lasers that produce vastly greater optical intensities than currently possible -- and potentially removing barriers to widescale research and commercial adoption.

Focusing on a solution

According to Kumar, the terahertz region of the electromagnetic spectrum is significantly underdeveloped due to lack of high-power sources of radiation. Existing sources feature low output power and other undesired spectral characteristics which makes them unsuitable for serious application. His current project aims to develop terahertz semiconductor lasers with precise emission frequency of up to 100 milliwatts of average optical power -- an improvement of two orders of magnitude over current technology -- in a narrow beam with signifcantly less than five degrees of angular divergence.

Kumar works with quantum cascade lasers (QCLs). These devices were originally invented for emission of mid-infrared radiation. They have only recently begun to make a mark at THz frequencies, and in that range they suffer from several additional challenges. In this cutting-edge environment, Kumar's group is among a select few in the world making progress toward viable and low-cost production of these lasers.

Kumar's intended approach will significantly improve power output and beam quality from QCLs. A portable, electrically-operated cryocooler will provide the required temperature-cooling for the semiconductor laser chips; these will contain phase-locked QCL arrays emitting at a range of discrete terahertz frequencies determined by the desired application.

In previous work, Kumar and his group showed that THz lasers (emtting at a wavelength of approximately 100 microns) could emit a focused beam of light by utilizing a technique called distributed feedback. The light energy in their laser is confined inside a cavity sandwiched between two metallic plates separated by a distance of 10 microns. Using a box-shaped cavity measuring 10 microns by 100 microns by 1,400 microns (1.4 millimeters), the group produced a terahertz laser with a beam divergence angle of just 4 degrees by 4 degrees, the narrowest divergence yet achieved for such terahertz lasers.

Kumar believes most companies that currently employ mid-infrared lasers would be interested in powerful, affordable terahertz QCLs, and that the technology itself will spawn new solutions.

"The iPhone needed to exist before developers could write the 'killer apps' that made it a household product," he says. "In the same way, we are working toward a technology that could allow future researchers to change the world in ways that have yet to even be considered."
-end-


Lehigh University

Related Radiation Articles:

Cloudy with a chance of radiation: NASA studies simulated radiation
NASA's Human Research Program (HRP) is simulating space radiation on Earth following upgrades to the NASA Space Radiation Laboratory (NSRL) at the US Department of Energy's Brookhaven National Laboratory.
Visualizing nuclear radiation
Extraordinary decontamination efforts are underway in areas affected by the 2011 nuclear accidents in Japan.
Measuring radiation damage on the fly
Researchers at MIT and elsewhere have found a new way to measure radiation damage in materials, quickly, cheaply and continuously, using transient grating spectroscopy.
Radiation that knocks electrons out and down, one after another
Researchers at Japan's Tohoku University are investigating novel ways by which electrons are knocked out of matter.
Novel advancements in radiation tolerance of HEMTs
When it comes to putting technology in space, size and mass are prime considerations.
Radiation-guided nanoparticles zero in on metastatic cancer
Zap a tumor with radiation to trigger expression of a molecule, then attack that molecule with a drug-loaded nanoparticle.
Graphene is both transparent and opaque to radiation
A microchip that filters out unwanted radiation with the help of graphene has been developed by scientists from the EPFL and tested by researchers of the University of Geneva (UNIGE).
Radiation causes blindness in wild animals in Chernobyl
This year marks 30 years since the Chernobyl nuclear accident.
No proof that radiation from X rays and CT scans causes cancer
The widespread belief that radiation from X rays, CT scans and other medical imaging can cause cancer is based on an unproven, decades-old theoretical model, according to a study published in the American Journal of Clinical Oncology.
Some radiation okay for expectant mother and fetus
During pregnancy, approximately 5 to 8 percent of women sustain traumatic injuries, including fractures and muscle tears.

Related Radiation Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Climate Crisis
There's no greater threat to humanity than climate change. What can we do to stop the worst consequences? This hour, TED speakers explore how we can save our planet and whether we can do it in time. Guests include climate activist Greta Thunberg, chemical engineer Jennifer Wilcox, research scientist Sean Davis, food innovator Bruce Friedrich, and psychologist Per Espen Stoknes.
Now Playing: Science for the People

#527 Honey I CRISPR'd the Kids
This week we're coming to you from Awesome Con in Washington, D.C. There, host Bethany Brookshire led a panel of three amazing guests to talk about the promise and perils of CRISPR, and what happens now that CRISPR babies have (maybe?) been born. Featuring science writer Tina Saey, molecular biologist Anne Simon, and bioethicist Alan Regenberg. A Nobel Prize winner argues banning CRISPR babies won’t work Geneticists push for a 5-year global ban on gene-edited babies A CRISPR spin-off causes unintended typos in DNA News of the first gene-edited babies ignited a firestorm The researcher who created CRISPR twins defends...