Advanced OPA enhances the energy of attosecond imaging ultra short pulses

The attosecond level ultra short laser pulse provides a powerful method for detecting and imaging ultra short processes, such as the motion of electrons in atoms and molecules.

Although ultra short laser pulses can be generated, generating ultra short and high-energy pulses is a continuous challenge. In order to expand the photon energy, photon flux, and continuous bandwidth of isolated attosecond pulses, it is necessary to develop stable, high-energy, and long wavelength single period laser sources.

Researchers at the RIKEN Advanced Photonics Center have developed a method for generating high-energy single cycle MIR pulses. This method is called Advanced Dual Chirp Optical Parametric Amplification (Advanced DC-OPA), which increases the energy of a single cycle laser pulse by 50 times and can be used to generate extremely short pulses with a peak power of 6 terawatts.

"At present, the output energy of attosecond lasers is extremely low," said researcher Eiji Takahashi. "If they are to be used as light sources for a wide range of fields, increasing their output energy is crucial."

Researchers used two types of nonlinear crystals to develop advanced DC-OPA - bismuth triborate oxide (BiB3O6) and lithium niobate doped with magnesium oxide (MgO: LiNbO3). The crystal magnifies the complementary regions of the spectrum.

Takahashi said, "The advanced DC-OPA for amplifying single cycle laser pulses is very simple, based only on a combination of two nonlinear crystals." "What surprised me was that such a simple concept provided a new amplification technology and brought breakthroughs in the development of high-energy, ultrafast lasers."

The damage threshold of nonlinear crystals limits the energy scalability of OPA under high pulse energy. Takahashi said, "The biggest bottleneck in the development of high-energy and ultrafast infrared laser sources is the lack of effective methods for directly amplifying single cycle laser pulses." "This bottleneck results in a millijoule barrier in the energy of single cycle laser pulses."

The advanced DC-OPA method overcomes the bottleneck of pulse energy scalability using single cycle IR/MIR laser systems.

The team expects that advanced DC-OPA methods will drive the development of attosecond laser technology forward. Takahashi said, "We have successfully developed a new laser amplification method that can increase the intensity of a single cycle laser pulse to terawatt level peak power." "This is undoubtedly a significant leap in the development of high-power attosecond lasers."

Due to the excellent energy scalability of the advanced DC-OPA method, laser pulses with higher pulse energy and fewer pulse duration cycles can be achieved based on different crystal combinations and higher pump energy. The extension of pulse energy can promote high-throughput detection conditions in strong field physics research.

Takahashi believes that by capturing the motion of electrons, attosecond lasers have made significant contributions to fundamental science. "They are expected to be used in a wide range of fields, including observing biological cells, developing new materials, and diagnosing medical conditions," he said.

The ultimate goal of Takahashi is to exceed the speed of the attosecond laser and generate shorter pulses. "By combining a single period laser with higher-order nonlinear optical effects, it is possible to generate optical pulses with a time width of Ze seconds (one Ze second=10-21 seconds)," he said. "My long-term goal is to open the door to research on Zeosecond lasers and open up the next generation of ultra short lasers after Atosecond lasers."

Source: Laser Net