Stephen Cheng — South China Morning Post Sept 22, 2015
A breakthrough in laser technology may give the Chinese military the ability to blind the sensors on enemy missiles or even satellites using a portable device the size of a suitcase, rather than the large container-sized version typically found on warships.
A research team led by Professor Li Zhiyuan with the Chinese Academy of Sciences’ Institute of Physics reported that they had reduced the sophisticated mechanism that generates a high-frequency laser down to a single piece of crystal.
This means the huge ultrafast laser generator that is used to render heat-seeking missiles useless, and which can be found on warships today, could be shrunk to the size of hand baggage and mounted on aircraft, tanks or even soldiers.
“This is a groundbreaking achievement,” said a professor at Beijing’s Tsinghua University, who requested that his name not be used due to the sensitivity of the issue.
“Nobody has generated a laser at such a high frequency on a single piece of crystal before,” added the professor, who was not involved in the research.
“Their technology will significantly simplify the process of ultrafast laser production and reduce the size of relevant devices.”
Part of the team’s research was detailed in the latest issue of the journal Physical Review Letters, which is run by the American Physical Society.
Since the invention of laser technology, scientists have been trying to increase the frequency of laser beams by reducing their wavelength. The higher the frequency, the more energy can be carried by photons.
A typical ultrafast laser device generates pulses as short as one quadrillionth of a second. Despite decades of development, however, their use has been mostly restricted to research laboratories, and eye surgery, because of the level of cost and sophistication involved.
Nonetheless, many countries have been racing to develop the technology for military applications.
The US Navy, for instance, reportedly commissioned a research project in 2012 to develop an ultrafast laser system to blind the infrared sensor on missiles.
This is based on the logic that it is much easier to use high-energy photons to attack a sensor than depend on a laser to destroy the thick metallic shell of a missile.
Apart from inflicting damage on enemy targets, ultrafast lasers can also serve as a handy tool to deal with encrypted communications and detect stealth aircraft.
However, the prototypes for military applications proved cumbersome and heavy.
While researchers developed various ways of making high frequency laser beams, such as using purified gas or multiple crystals, they all required the device to be set up in a large room with delicate components that are vulnerable to external disturbances such as shaking.
Li’s team claim to have solved this problem. They developed a special crystal with lithium and niobium that can convert a normal laser beam into high frequency waves as short as 350 nanometres, or three times faster than the ultrafast system in use today.
The technology “hints at a very promising means for greatly expanding the power” of laser technology, the team said in their paper.
The Tsinghua professor said the biggest challenge was the loss of energy in the frequency conversion process.
“The larger the laser system, the more serious the energy loss,” he said.
The conversion efficiency of Li’s crystal was 18 per cent, which meant more than 80 per cent of the energy would be lost.
But the professor said that the rate of efficiency was still “very high” for an ultrafast laser system.
“If they can achieve the efficiency they claim, I think their technology can be quickly deployed in field applications,” he said.