New pulsed laser system delivers 'world’s highest' pulse energy

Hamamatsu Photonics has developed a pulsed laser system that produces what the firm says is the world’s highest pulse energy among laser-diode-pumped lasers: 250J.

The announcement was made during the Japan’s largest optoelectronics exhibition ‘Optics & Photonics International Exhibition 2021’ in Yokohama last week, where the firm also exhibited samples machined with the new system.

The new laser system boosts the energy storage capability of the laser medium as well as beam quality to deliver more than double the energy amplification capability while still maintaining the same size as currently available industrial pulsed lasers.

By acquiring and integrating the machining process data from this laser system, Hamamatsu will be able to build a useful database for optimising laser processing conditions through the use of artificial intelligence (AI)

This will not only streamline laser processing-machining tasks, but also open up new frontiers in energy and medical and applications, according to the firm.

The development of the new laser system stems from the ‘Research and Development of Next Generation Laser Processing Technology’ project supported by NEDO (New Energy and Industrial Technology Development Organization), a national research and development agency in Japan.

Powering up the pulse

Lasers used for material processing and machining are broadly classified into two groups. One group is continuous-wave (CW) lasers that continuously emit light at a constant intensity. The other group is pulsed lasers that repetitively emit pulsed light at very short time intervals. 

CW lasers are used for heat treatment tasks such as laser welding and cutting, making them the mainstream tool for laser processing and machining. Pulsed lasers on the other hand, according to Hamamatsu Photonics, have not yet been widely used in these applications, except for laser peening. This is because high-power semiconductor lasers (laser diodes) and large-size laser mediums that are needed for developing high-power pulsed laser systems have not been available. This has hindered the task of setting up systems to find critical processing and machining conditions such as the optimum irradiation time and energy. 

How a pulsed laser beam is amplified: The laser medium is pumped by laser diode modules and stores energy. When a pulsed laser beam passes through the laser medium, it receives energy from the laser medium and boosts the output power. (Image: Hamamatsu Photonics)

To overcome these challenges, Hamamatsu Photonics has been developing high-power pulsed laser systems as part of the ‘Development of Advanced Laser Processing with Intelligence Based on High Brightness and High-Efficiency Next-Generation Laser Technologies (TACMI) project, supported by NEDO. 

In 2019 it developed an industrial pulsed laser that produces a pulse energy of 117J by using four laser diode modules and two laser amplifiers, each equipped with six ceramic laser mediums.

The firm continued its efforts to further boost the output power and has now succeeded in creating the industrial pulsed laser system that delivers a pulse energy of 250J, which it says is the world’s highest energy among laser-diode-pumped lasers. The system has a wavelength of 1,030nm and can achieve a pulse width of 30ns, although the pulse width can be varied, according to Hamamatsu Photonics.

'Compared to our previous system, this new laser system has approximately double the light energy storage capacity,' the firm said in its announcement of the new system. 'We achieved this by installing a laser medium composed of 10 ceramic disks, each with the world largest surface area optimised for a laser medium. We also reassessed and revamped the amplifier design and utilised eight of our newly designed compact laser diode modules mounted at ideal irradiation angles and positions.'

Doing this increased the pumping efficiency to the laser medium and improved the pumping capacity to about twice that of the previous system.

Structure of newly developed pulsed laser amplifier. (Image: Hamamatsu Photonics)

‘At the same time, using this new laser system, we also evaluated basic conditions essential for designing a 1kJ class laser, which will prove an important milestone in laser technology development, and confirmed that it is practical and achievable,’ the firm added.