This Nobel Prize winner paved the way for high-intensity lasers

As a child, Donna Strickland had one goal: to get a Ph.D. But she didn’t know what subject she wanted to study until she started studying physics at McMaster University in Hamilton, Ontario, Canada. It was there that she became interested in the study of lasers after taking a course in the subject.

The theme seemed “really cool—like something out of a sci-fi novel,” says Strickland. Little did she know that her newfound passion would one day win her the Nobel Prize in Physics.

While conducting research in optics for her PhD at the University of Rochester in New York, Strickland worked with French physicist Gérard Mouroux, a laser pioneer and Nobel laureate. Muru led the development of the Extreme Light Infrastructure, a network of physics laboratories built to generate and study intense laser radiation. Together, while experimenting on how to increase the peak power of a laser without damaging it, they invented a method for amplifying chirped pulses. CPA, which produces short, high-intensity laser pulses, is now being used in corrective eye surgery, medical imaging, smartphone manufacturing, and many other applications.

Strickland and Moore shared the 2018 Nobel Prize in Physics with IEEE Life Fellow Arthur Ashkin, who invented a separate technology: “optical tweezers” that use low-power laser beams to manipulate living cells and other tiny objects.

Winning the Nobel Prize “changed lives,” says Strickland, adding, “Your life can change overnight, even if you’re not ready for it.”

Her invention also earned her an IEEE sponsored honorary membership this year. She says the recognition is special because colleagues nominated her for it.

“Donna’s work has transformed me. Her original research on amplifying chirped pulses is the research gold standard,” said one of her supporters. “In addition, she is a real role model for legions of engineers around the world. She is an extremely generous person and a shining example of what an honorary member of the IEEE should be.”

Strickland is a professor of physics at the University of Waterloo in Ontario, where she leads a research team developing high-intensity laser systems for research in nonlinear optics, such as mid-infrared pulse generation by difference frequency mixing and the study of multi-frequency Raman generation.

Donna Strickland receives the 2018 Nobel Prize in Physics from King Carl Gustaf of Sweden at the Stockholm Concert Hall.Henrik Montgomery/TT News Agency/Getty Images

Paving the way for high-intensity lasers

After graduating in 1981 with a Bachelor of Science in Engineering from McMaster, Strickland moved to New York to earn his PhD in optics from the University of Rochester, which at the time was considered one of the best institutions for studying laser optics. She joined Moore at the university’s laser energy lab, where he was looking for ways to increase the intensity of lasers (its optical power) without damaging the device.

Pulsed lasers can concentrate light on a small area for a short time to produce energy. The peak intensity increased rapidly over several years after physicist Theodor Meiman demonstrated the first laser in 1960. But after 1970, the intensity stabilized for more than a decade because amplifying light past a certain point damaged the laser.

In his study of how light interacts with matter, Muru hypothesized in 1983 that splitting and amplifying the pulses before recombining them could result in more intense laser pulses without damage. But he didn’t know how to do it, Strickland says. So for her doctoral research, she tested his hypothesis with various laser systems. However, none of her experiments worked.

“Donna is a true role model for legions of engineers around the world. She is an extremely generous person and a shining example of what an honorary member of the IEEE should be.”

It wasn’t until Strickland and Moore visited the 1984 International Conference on Ultrafast Phenomena that they found a solution. The bi-annual event brings together scientists who develop tools, methodologies and methods used to study processes in atoms, molecules or materials that occur in millionths of a billionths of a second or faster.

Strickland and Moore attended a conference presentation on newly developed fiber optic pulse compression for neodymium-doped yttrium aluminum garnet (Nd:YAG) lasers. With this method, 100 picosecond pulses can be compressed to 1 ps using non-linear optics in the optical fiber to increase the spectral bandwidth of the laser. It was found that compression was most successful when the pulses were stretched by dissipation in the fiber.

“I used the same lasers for my experiments,” Strickland recalled.

She and Moore figured out how to safely create a high-intensity impulse: the impulse had to be stretched before it was strengthened, not after, as it was done. The pulse stretch meant that it could be re-compressed to obtain the desired intensity.

To test their theory, Stickland and Moore built a system at the Laser Energy Laboratory, consisting of a 2-watt Nd:YAG laser, 1.4 km of optical fiber, an amplifier, and a pair of parallel arrays.

The Nd:YAG laser pumped a short 100 ps pulse into the optical fiber. Since the speed of light depends on the wavelength, the red component of light travels faster inside the fiber than the blue component.

According to Strickland, this is called “chirping” because bird chirps have a similar frequency structure.

The chirped pulse lengthens the duration of the pulse and distributes the intensity so that it does not damage the laser. The stretched, lower energy density pulse was then amplified and passed through a pair of parallel diffraction gratings, allowing the rear blue component to catch up with the red. Both were reassembled by reflection from the gratings. According to Stickland, the reassembled pulse was three times as powerful as the original.

The technique, named after the chirped pulse, has since paved the way for the shortest, most intense laser pulses ever made, allowing for more compact and precise laser systems.

Strickland and Moore’s 1985 paper “Compression of amplified chirped optical pulses” was published in Optical communications. This was Strickland’s first published research paper.

From Princeton to Waterloo

After helping develop the CPA, Strickland still didn’t know which career to choose. She turned to her colleagues for advice, and one of them told her that Paul Corkum, a physicist who worked in the Ultrafast Phenomena Division of the Canadian National Research Council, was receiving his first PhD fellow this year. Korkum, who specialized in laser science, pioneered the development of attosecond physics. Strickland liked the sound of it.

“I remember telling other doctoral students in my research lab that Korkum might not know my name yet, but I was going to be his second postdoc,” she says. She got her dream job in 1988 and worked for him for three years.

In 1991, she became a physicist at the Lawrence Livermore National Laboratory, a US Department of Energy facility in California.

While she lived on the West Coast, her physicist husband lived on the East Coast, working at Bell Labs in Murray Hill, New Jersey.

After spending a year apart, Strickland moved to New Jersey to join the technical staff at the Princeton Center of Excellence in Photonics and Optoelectronic Materials. According to her, she worked there with electrical engineers, mechanical engineers and chemists, and “if they had a laser, I helped them.” She helped the professor build the CPA laser and assisted the research team in the non-linear optical characterization of the new pulse amplification material.

Strickland says she thought she would work at Princeton until she retired, but after her husband left Bell Labs in 1996, they returned to Canada. Strickland joined the physics department at the University of Waterloo as an assistant professor. In 2002 he was awarded the title of Associate Professor. From 2007 to 2013 she worked as an assistant professor of the department.

“When I was young, I just wanted to get my Ph.D. and stay in school,” says Strickland. “Being a professor is better than being a student.”

She received an IEEE Honorary Membership on May 5 at the IEEE Vision, Innovation and Challenges Summit and Awards Ceremony at the Hilton Atlanta Hotel.