SPONSORED: HIGH DAMAGE OPTICS
New high LDT coatings help break world record
With laser systems pushing the boundaries of high power and performance, it is no surprise the dedicated team at Hilase have managed to break new ground, using optics supplied by Manx Precision Optics
I
n January a team of scientists at Hilase, led by Dr Martin Divoký, beat the previous
world record for average power output from a high energy laser (which they set themselves in 2016). The team, in partnership with the Science and Technology Facilities Council’s (STFC) Central Laser Facility, operated the BIVOJ laser system for an hour at a pulse energy in excess of 145J in 10ns pulses at a repetition rate of 10Hz at 1030nm. The BIVOJ laser system is a pulsed nanosecond diode-pumped solid-state laser (DPSSL) developed at the Central Laser Facility, and classifies as a powerful kW laser. The system uses cryogenic cooling technology and the extraordinary feat achieved by the team is a huge milestone in the development of high-power laser systems. Key to the facility is the
dedication and professionalism of the team behind it. Dr Martin Divoký’s highly skilled and passionate team adheres strongly to cleanliness procedures, and their knowledge and experience ensures that all the featured optics are carefully mounted and aligned. Part of the success of the record-
breaking BIVOJ laser system is down to the optical components used, supplied from partners Manx Precision Optics, in the Isle of Man, as well as Crytur, in the Czech Republic. Manx Precision Optics (MPO)
have been working with STFC since MPO’s inauguration in 2013, and with Hilase since 2017, being trusted by both to provide high quality, high LIDT optical components. In working with
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Hilase, MPO have developed coatings which have a Laser- induced Damage Threshold (LIDT) close to the physical limits of the BIVOJ laser.
Achieving high LIDT When designing an optical component for a sustained high- power beam such as the BIVOJ system, the optical coating is the primary factor in the success. Manx Precision Optics has years of experience in high energy optics, and understands that there are a number of factors that are highly important in optical performance. Chris Bridle, MPO's large optic and key account manager, explained: 'It’s not just about selecting materials, obviously these are critical, you need to select materials that can withstand the Laser-induced Damage Threshold, but also the process parameters are all critical. The vacuum environment, temperature, evaporation rates and background gasses all have an important role to play, and process repeatability is key’
When designing the coating
for the optics in the BIVOJ, Manx Precision Optics were mindful of how the system was to be used, and worked within those considerations to design a coating that could withstand the laser damage, without negatively impacting other areas of the optical configuration. Coating design was not the
only factor that Manx Precision Optics had to consider, as any surface errors can significantly impact the LIDT of an optic. MPO’s grinding and polishing processes
BIVOJ laser system
High LIDT optic manufactured by Manx Precision Optics
are designed to remove sub surface damage and promote a high quality, low-surface roughness, contamination-free substrate. ‘Our after-coating flatness is
something that we take great pride in’ says Dr Helmut Kessler, the firm's managing director. MPO’s superior after coating flatness ensures beam quality is maintained throughout the chain of optics, which ensures a superb output performance.
Partnership is paramount The success of Dr Divoký and the Hilase team shows the importance of partnership within the photonics community. The BIVOJ laser system used to break the record was initially developed at STFC’s Central Laser Facility, and it was a joint team of Hilase and STFC scientists who set the previous record. While not only a record-breaking
achievement, the success of the joint project provides invaluable data and will feed into STFC’s development of the Extreme Photonics Application Centre, to be constructed at STFC Harwell. With the organisation also loaning another laser to the European
XFEL system in Germany, co- operation remains strong in the European photonics community. In working with Manx Precision Optics and Crytur on the world record achievement, Hilase has shown the power of strong international co-operation with trusted suppliers who can offer high LIDT, high quality optical components. Dr Divoký commented on the
relationship between the facility and Manx Precision Optics. ‘We started looking for durable optics for our new high-energy high-average power laser in 2017, when most of the mirrors in the laser burned in just under five minutes. We approached several manufactures, MPO being one of them. Over the years I valued their open approach to share information about the coating process with us. This openness on both sides bore fruit in a couple of years, when the first mirror with high enough LIDT was made available to us. The mirrors were one of several key elements needed to push the limit of the laser to 1.45kW in 145J @ 10Hz’ EO
https://mpo.im March 2021 Electro Optics 25
Image courtesy of Hilase Czech Republic,
www.hilase.cz
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