Hamamatsu Photonics announces successful output of 100J laserpulses at a high repetition rate of 10Hz

18th January 2023
Harry Fowle

Hamamatsu Photonics has succeeded in producing laser pulses with energy of 100J at a high repetition rate of 10Hz. This was achieved by increasing the cooling capacity for the laser medium of the pulsed laser system and by optimizing the output of the laser diode module for pumping.

To make laser fusion practical, the fusion fuel needs to be efficiently irradiated with a pulsed laser that produces as much as 1MJ at a high repetition rate of 10Hz. We believe that establishing this technology is an important milestone where the results from this study will help us move toward this goal. We will present the results of this study at a symposium and general lecture at the 43rd Annual Meeting of the Laser Society of Japan to be held at WINC AICHI, Nakamura-ku, Nagoya, Japan from the 18th to 20th January 2023.

Laser system for producing 100J pulsed laser output at 10Hz

The system uses several amplifiers to boost the energy of 10Hz laser output from the oscillator from 1μJ to 100J.

Nuclear fusion is a reaction in which atomic nuclei are fused together to form a heavier nucleus, releasing a huge amount of energy in the fusion process. Laser fusion is a technology that creates nuclear fusion by irradiating fuel capsules containing deuterium and tritium with high-power lasers.

Practical laser fusion requires pulsed lasers with energy as high as 1MJ to irradiate the fusion fuel at a high repetition rate of 10Hz. To accomplish this goal, we are engaged in research and development of high-energy, high-repetition-rate pulsed laser systems using laser amplifiers in which the laser medium is pumped by LD modules and highly efficiently cooled by helium gas.

In 2021, in collaboration with the New Energy and Industrial Technology Development Organization (NEDO), which is Japan’s national research and development agency, we developed a pulsed laser system that produces 250J laser pulses at 0.2Hz with an average output power of 50W, which is the world’s highest energy level among LDpumped lasers. Since then, we have been working to increase the repetition rate. However, increasing the repetition rate also raises the temperature of the laser medium and degrades its optical characteristics. To cope with this situation, we improved the cooling mechanism for the laser medium to increase the flow of helium gas and in this way enhance the cooling capacity. We also optimised the output of the pumping LD modules to prevent the temperature of the laser medium from rising. This resulted in minimal deterioration of laser medium characteristics and successful output of a 100J pulsed laser at10 Hz with an average output power of 1kW.

Results of this study confirmed the possibility of increasing the average output power by scaling up the laser system, and so helped us move forward to establish a technology to produce laser pulses of 1kJ at 10Hz, which we see as an important milestone on the road to practical laser fusion. These results are also expected to contribute to new research in the field of basic science.

As our next step, we will continue research and development to establish a technology to produce laser pulses of 250J at 10Hz.

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