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Title image: A technician inspects a high-tech laser at a natural gas facility in Colorado. (Credit: Casey Cass/����������)

Sean Coburn walks down a dusty dirt road in Greeley, Colorado, flanked by a scene that’s becoming more common in this city at the edge of the Front Range—rows and rows of tanks, pipes, stacks and other hallmarks of the oil and gas industry.

The engineer, who earned his doctorate from ���������� and now splits time between the university and a company called , is wearing a flame retardant jacket, bulky boots and a hard hat. He needs them on this site. Here, operators take raw and very flammable oil and natural gas, the latter mostly composed of methane, and process it into a form that people can use to heat their homes or drive their cars.

But Coburn is heading for something else: a metal tower, about 50-feet-tall with what looks like a security camera on top.

“We pipe the laser light up from there,” said Coburn, pointing at a cabinet at the base of the tower. “Then we shoot it at different targets around the site.”

As he talks, the cabinet beeps, and the laser emitter at its end begins to turn, sweeping over the landscape.

The tower is part of an ambitious undertaking from scientists at LongPath and ����������. They’re using new laser technology to do what other technologies have struggled to do for years: detect natural gas, which is invisible to the eye, leaking from pipes at sites like this, in real time.

Methane is a powerful greenhouse gas, said Greg Rieker, an associate professor of mechanical engineering��at ����������. He testified before the U.S. House of Representatives��Committee on Science, Space and Technology��June 8 . He noted that methane��can trap nearly 80 times more heat in the atmosphere than carbon dioxide, and research suggests that escaped methane from oil and gas operations may play a much bigger role in climate change than previously thought.

LongPath is trying to plug that source. The company’s towers shoot lasers over miles of terrain to sniff out even the faintest whiffs of methane in the air. So far, the company has installed 23 of them covering almost 300,000 acres in Texas, New Mexico, Oklahoma��and Colorado. Rieker believes��the technology could be a win-win for the West: Slowing down emissions of this dangerous gas, while also reducing costs for an industry that employs tens of thousands.

The story of this technology, called a dual frequency comb laser spectrometer, dates back to the 1990s when a�� first developed frequency comb lasers to explore the working of atoms—and earned a Nobel Prize in the process.

“Now, we’re able to use those same ideas and, with just one of these systems, mitigate about 80 million cubic feet of methane emissions per year,” said Rieker who co-founded LongPath in 2017.

A LongPath Technologies van visits a natural gas facility in Greeley. (Credit: Casey Cass/����������)

Thinking small

Scott Diddams was part of those early days of frequency comb lasers. He was a postdoctoral researcher working with Hall at between ���������� and the National Institute of Standards and Technology (NIST), to probe quantum physics—or the mysterious workings of very, very small things.

The researchers weren’t thinking about methane hovering over oil fields at the time. Instead, they used their lasers to measure how fast atoms tick. To make an atomic clock, Diddams explained, physicists first shine laser light at a cloud of atoms, giving them a kick so that they flip between different energy levels at a staccato pace. Hall’s group invented frequency combs to help count out that rhythm.

“Atoms tick nearly a quadrillion times per second,” said Diddams, now a professor in the Department of Electrical, Computer and Energy Engineering. “You need a really special tool to count those cycles.”

Frequency combs were special. Normal lasers, like the pointers in any lecture hall, can only generate one type of light: say, red light or green light. But these new lasers could produce thousands or even millions of colors of infrared light at the same time—an entire rainbow inside a single beam.

Hall and German scientist Theodor Hänsch took home a Nobel in 2005 “for their contributions to the development of laser-based precision spectroscopy, including the optical frequency comb technique."

By the time Rieker joined ���������� in 2013, he and Diddams were already wondering what else frequency combs could do.

Quantum comb

Greg Rieker (left) works with a colleague in his��lab at ����������. (Credit: Casey Cass/����������)

Comb-like spikes on a computer��screen illustrate measurements of methane, water and carbon dioxide. (Credit: Casey Cass/����������)

A laser emitter sits at the top of a tower at a natural gas facility in Colorado. (Credit: Casey Cass/����������)

At LongPath’s offices in Boulder, Coburn and his colleagues open a computer window showing the data coming in from the system in Greeley. The graph shows a squiggly readout with sharp spikes like the teeth in a comb.

Each tooth corresponds to a color in the team’s frequency comb laser (hence, the name). Rieker explained that if you shine one of these devices into a cloud of gas, the molecules inside will absorb some of those colors but not all of them. In other words, molecules will leave an imprint on the laser light, almost like pressing your thumb to a glass.

“Each of these different molecules absorbs a different pattern of light,” Rieker said. “Methane has o