Chinese researchers have developed a two-kilowatt (kW) fibre laser capable of operating without the protection of heating or cooling systems across Earth’s most extreme climates – from temperatures of minus 50 degrees Celsius (minus 58 degrees Fahrenheit) in the Arctic to 50 degrees Celsius (122 degrees Fahrenheit) in the Sahara Desert.
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The device, designed for quick and ultra-portable deployment for both defence and industrial purposes, starkly contrasts with counterparts with similar power output such as the European HELMA-P or India’s IDDIS, which require truck transport with container-sized cooling units to achieve a 1km (0.62 miles) kill range on drones.
Led by Chen Jinbao, vice-president of the National University of Defence Technology and a national award-winning pioneer in high-energy lasers, the team overcame a decades-long challenge: stabilising laser performance across 100-degree temperature swings.
Their innovation hinges on some radical design choices, including 940-nanometre pump lasers with minimal thermal drift, directly injecting light via nine forward and 18 backward fibre-coupled diodes.
They also put pump combiners outside the resonator to isolate heat-sensitive components. Coiling ytterbium-doped fibre at around 8cm (3.1 inches) diameters helps to suppress parasitic lightwaves.
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“We have achieved a technological breakthrough in the performance of wide-temperature operating fibre lasers,” wrote Chen and his colleagues in a peer-reviewed paper to be published in the Chinese-language journal Higher Power Laser and Particle Beams in July, now available online.
At the laser’s core lies a dual-clad optical resonator – 99 per cent reflective gratings at both ends sandwiching ytterbium-doped fibres. When pumped, ytterbium ions emit photons amplified into a lethal 1,080nm beam, filtered and collimated through quartz caps.