Inventions: Ultra-fast lasers
Medical surgery, detailed manufacturing and scientific research took a quantum leap forward when Swiss scientist, inventor and professor Ursula Keller discovered how to turn continuous laser light into ultra-fast laser pulses. With light bursts lasting less than a trillionth of a second, Keller's inventions handed science, industry and the medical community an instrument of unprecedented precision.
Scientific research, industrial micromachining and critical medical operations require increasingly precise tools. But scientists,
manufacturers and surgeons alike were unable
to tame the instrument of greatest precision - light itself.
Keller's semiconductor saturable absorber mirror (SESAM), which she invented in 1992 while working at AT&T Bell Laboratories, provided a practical method to create extremely short, energetic bursts of laser light. Thanks to her developments, lasers can now produce short bursts ranging in duration from picoseconds (10-12 seconds) to femtoseconds (10-15 seconds) and repeating up to several billion times a second.
Ultra-fast Femto-Lasik for eye surgery is able to make tiny incisions with no risk of damaging nearby tissue. Similarly, cancerous tissue can be cut away without searing neighbouring healthy cells. And the technology has opened up numerous machining and material-processing applications that are vital to the automotive and electronics industries.
In her role as a physics professor at the Eidgenössische Technische Hochschule (ETH) Zurich, Keller has further refined and developed the SESAM concept, widening it to include more types of laser; in addition, she has developed precise scientific measuring equipment that explores the wonders of the universe down to the quantum level.
Societal benefit
Nearly every commercially available ultra-fast laser now incorporates SESAM in its design. Thanks to these ultra-fast lasers, extremely small, thin slices of a material can be removed (10 to 100 nanometres per laser pulse) - not by heat, as with other types of laser, but through a process called cold ablation. In medical applications, especially in eye surgery, SESAM-equipped lasers deliver the precise amount of energy required to make fine incisions without damaging the surrounding tissue.
Because these lasers do not heat the surrounding material, they are also used for fine details on glass, polymer and silicon substrates that would otherwise crack or become brittle under higher temperatures. These lasers are helpful for the manufacturing of high-tech electronic devices such as smartphone touchscreens, flat-screen monitors and television sets, which require etching patterns on toughened glass or precision cutting.
The automotive industry has also been a major adopter of ultra-fast laser applications since SESAM technology was first marketed two decades ago. Ultra-fast lasers can "drill" intricate, small pits to reduce friction and extend the product life of small rotating parts. They are also a replacement for standard micromachining techniques used to optimise the spray pattern of direct fuel injectors. The resulting, simple but precise design feature can help improve fuel efficiency by 10% or more without affecting performance.
In addition, Keller has adopted her SESAM technology for inexpensive laser light sources, making them suitable for applications such as laser displays, telecommunications and as the light source for medical imaging technologies. A newer adaptation of SESAM, called MIXEL, is easier to produce and broadens the potential applications to include consumer electronics - such as lasers in gaming consoles and laser guidance systems (LIDAR) for self-driving vehicles.
Economic benefit
The global market for ultra-fast lasers was valued at EUR 2.17 billion in 2017, or about one-fifth of the total laser market, and is expected to reach a value of EUR 8.3 billion by 2023. The automotive industry has been identified as one of the prime areas for growth, because of new ultra-fast laser micromachining applications for both turbocharger turbine wheel shafts and direct fuel injectors. The global market for ophthalmic (eye surgery) lasers, including ultra-fast (femtosecond) lasers, is expected to grow from about EUR 784 million in 2016 to around EUR 1 billion in 2021. The femtosecond laser segment is expected to dominate the overall market in terms of revenue and growth.
Major players in the ultra-fast laser sector include France-based Amplitude Systèmes, US firm Coherent, German company Trumpf, Lithuania's Ekspla and the UK's Fianium. Another is Lumentum, the parent company of Time-Bandwidth Products, which is a spin-off company from ETH Zurich that Keller started in 1995.
Keller also launched a second start-up, GigaTera, that was incorporated into Time-Bandwidth Products. Several of Keller's students have developed spin-off or start-up companies of their own, including High-Q (now owned by MKS), Onefive (acquired by NKT Photonics in 2017) and Amplitude Systèmes. While it is difficult to assign exact values, these activities are estimated to have generated over EUR 100 million of economic activity, with the majority of their high-end laser jobs created in Europe.
