Scientists achieve extremely short laser pulses with a peak power of 6 terawatts

RIKEN's two physicists have achieved extremely short laser pulses with a peak power of 6 terawatts (6 trillion watts) - roughly equivalent to the power generated by 6000 nuclear power plants. This achievement will contribute to the further development of attosecond lasers, for which three researchers were awarded the Nobel Prize in Physics in 2023. This study was published in the journal Nature Photonics.

Just like camera flashes can "freeze" rapidly moving objects, making them appear stationary in photos, extremely short laser pulses can help illuminate ultrafast processes, providing scientists with a powerful method for imaging and detecting them.

For example, laser pulses of the order of attoseconds (1 attosecond=10-18 seconds) are so short that they can reveal the motion of electrons in atoms and molecules, providing a new method for discovering the evolution of chemical and biochemical reactions. Even light seems to be able to crawl on such a short time scale, passing through one nanometer takes about 3 attoseconds.

"By capturing the motion of electrons, attosecond lasers have made significant contributions to basic science," said Eiji Takahashi of RIKEN Advanced Photonics Center (RAP). "They have the potential to be applied in a wide range of fields, including observing biological cells, developing new materials, and diagnosing medical conditions."

More impactful
However, although it is possible to produce ultra short laser pulses, they lack impact force and have low energy. Creating ultra short and high-energy laser pulses will greatly expand their potential applications. Eiji Takahashi said, "The current output energy of attosecond lasers is extremely low. Therefore, increasing their output energy is crucial if they are to be used as light sources in a wide range of fields."

Just like audio amplifiers are used to enhance sound signals, laser physicists use optical amplifiers to increase the energy of laser pulses. These amplifiers typically use nonlinear crystals with special responses to light. However, if these crystals are used to amplify single cycle laser pulses, they will suffer irreparable damage. The single cycle laser pulse is very short, to the point where it ends before the light oscillates for a complete wavelength cycle.

Eiji Takahashi stated, "The biggest bottleneck in developing high-energy, ultrafast infrared laser sources is the lack of an effective method to directly amplify single cycle laser pulses. This bottleneck results in a 1 millijoule barrier of single cycle laser pulse energy."

Set a new record
However, this bottleneck has now been overcome. They have amplified the single cycle pulse to over 50 millijoules, which is more than 50 times the best result before. Due to the extremely short laser pulses generated, these energies are converted into incredible high power of several terawatts.
Takahashi said, "We have demonstrated how to overcome bottlenecks by establishing an effective method to amplify single cycle laser pulses."

Their method, called Advanced Double Chirp Optical Parametric Amplification (DC-OPA), is very simple and only involves two crystals, amplifying the complementary regions of the spectrum.

Takahashi said, "The advanced DC-OPA for amplifying single cycle laser pulses is very simple, it's just a combination of two nonlinear crystals - it feels like an idea that anyone can think of. Such a simple concept provides a new amplification technology and has made breakthroughs in the development of high-energy ultrafast lasers, which surprised me."

Importantly, advanced DC-OPA operates over a very wide wavelength range. The research team is able to amplify pulses with wavelengths that differ by more than twice. Takahashi said, "This new method has a revolutionary feature, which is that amplifying bandwidth can achieve ultra wide frequency output without affecting the output energy scaling characteristics."

New amplification technology
Their technology is a variant of another optical pulse amplification technique called "chirped pulse amplification", for which three researchers from the United States, France, and Canada won the Nobel Prize in Physics in 2018. There is an interesting connection between the awards in 2018 and 2023: Chirped pulse amplification is one of the technologies driving the development of attosecond lasers.

Takahashi predicts that their technology will further drive the development of attosecond lasers: "We have successfully developed a new laser amplification method that can increase the intensity of a single cycle laser pulse to a peak power of terawatts," he said. "Undoubtedly, this is a significant leap in the development of high-power attosecond lasers."

In the long run, his goal is to surpass attosecond lasers and create shorter pulses.

Source: OFweek Laser Network