Pushing the limits of space laser research in China


Of his many nicknames, Hou Xia prefers Daxia, which means swordsman in Chinese.

Sharing the same pronunciation with his first name, xia translates to honorable, chivalrous and heroic, revealing an ultimate Chinese humanist spirit. As a key researcher of China’s advanced laser technology, Hou truly lives up to her modern female nickname. daxia in the scientific community.

Thanks to pioneers like her, China is no longer a beginner or a dilettante in the field of space laser technology. Additionally, the country has launched the most laser devices into space in the past decade, a feat that was inconceivable years ago.

Just at the start of this century, China still relied on importing basic components of laser devices.

“We started from scratch,” she admitted, noting that “there were no giants we could stand on” when they were tasked with developing space laser devices for the the country’s first lunar probe. “Many experts were not convinced that we could make 100% original devices. But for me, that only strengthened my determination to make them.”

For her outstanding achievements, she was honored as one of the 10 “Most Beautiful Women Science and Technology Workers” in Shanghai this year.

Ti Gong

Hou Xia fully concentrates on his research work.

Hou was in a way intended to devote himself to advanced laser research.

She developed a consuming passion for science fiction in her childhood. After school, she rushed to bookstores, wandered the shelves, and flipped through countless pages of fictional stories about space.

“I always pressed my father until he finally gave me the money to buy the newly published copies of these books,” she said wistfully for those innocent days gone by. “I still remember a book about ‘deadly light.’ Growing up, I learned it was a laser.”

Perhaps his fate with the laser first revealed itself at this point. But for sure, his childhood reading habits planted the seeds of science in his mind.

“In fact, science fiction predicts and inspires real inventions. Many science researchers and tech moguls are big fans of science fiction,” Hou said, giving the example of Tesla founder Elon Musk.

One of his favorite science fiction stories is “The Hitchhiker’s Guide to the Galaxy” by Douglas Adams. “There is no denying that its huge investment in the space industry is tied,” she added.

In college, Hou majored in optical engineering. After graduation, she went to work at the Shanghai Optics and Fine Mechanics Institute (SIOM) of the Chinese Academy of Sciences. It was there that she realized that what she had learned in the past did not match her new job.

As a simple example, cameras and laser devices are optical instruments, but the former receives light and the latter emits light.

“I was totally confused. I just knew things like cameras. I didn’t know much about lasers. I didn’t know what to do and found no interest in it,” she said, describing it as a daring new adventure. But soon she found it interesting and stimulating.

She engaged in research just as her mentor had asked her: “There are so many researchers, but very few can reap fruit. Do it.

Now, scientific research is just a platform for her to do something she loves; contribute to academia, but not to gain reputation or status. “I love science,” she said, “and I want my research to have an impact on society”.

Pushing the limits of space laser research in China

Ti Gong

Hou Xia (right) in the lab with a colleague

China’s first laser device was manufactured in 1961. Three years later, SIOM was established as China’s first institute specializing in laser science and technology. Half a century later, space has opened up. As China joined the space race, the institute began to explore laser applications in space. However, for decades it has fallen behind on the world stage.

“Developing a machine from a simple scientific experimental device is fraught with technical difficulties,” said Hou. “Plus, there is a huge gap between making it work on Earth and in space.”

The vacuum environment, microgravity, dramatic temperature changes of 200 to 300 degrees Celsius, as well as the rockets’ extremely high thrust force, made the task rather difficult. This requires multidisciplinary knowledge.

She once made the mistake of pressing an oil pump the wrong way because of her limited knowledge of the device. Over time, she worked to become a versatile researcher to fill these gaps in her team after becoming familiar with cutting-edge laser technology.

In 2003, the science of space lasers in China was still in its infancy. With no previous products or research to refer to, Hou and his colleagues forged their own path.

“At that time, only the United States had successfully developed lasers for a space probe. There was considerable skepticism about our efforts,” she said. “But we, including our government, were all so determined that we had to become technologically self-sufficient. So from a small component to a complete device, we created it step by step, and ultimately a truly developed laser device on the level. National was launched into space in 2007 as a payload for the Chang’e-1 lunar probe. “

Hou said, “It strengthened my decision to devote myself to science. In addition, I learned to understand the right ways to do scientific research.”

Known as China’s very first solid-state laser for a laser altimeter, it emitted the first laser onto the moon’s surface on November 28, 2007. Data collected by the satellite altimeter gave rise to a model of lunar topography, from which medium-scale volcanoes and basins have been discovered.

Hou and his colleagues continued to make breakthroughs at breakneck speed.

In later lunar probes, the laser devices they developed were equipped with several functions, such as drawing a 3D map on the lunar surface to help the rover find an easier landing point.

Pushing the limits of space laser research in China

Ti Gong

In 2012, she began to direct her team’s research towards space laser communication and laser remote sensing technology. Four years later, she led the team in the development of the country’s first lidar to detect particles or gases in the atmosphere.

During this time, she also developed a laser device for the very first cold atom clock to operate in space. It was sent into space with the Chinese Tiangong-2 space laboratory in 2016.

The black cylinder-shaped object is unlike any ordinary clock, but it is one of the most advanced timepieces of all time. Using advanced “cold atom” technology, it is so precise that it will not extinguish for a second for 30 to 300 million years in space.

“It has been operating stably for over four years to date,” Hou said. “China was behind other countries at the start of development, but now we are playing the leading role.”

Nowadays, besides space exploration, space lasers are mainly used for laser communications to achieve interstellar communication, remote sensing and surveillance such as analysis of the Earth’s atmosphere, as well as scientific experiments conducted in space that cannot be properly realized on Earth.

China has emerged as a major power in space lasers, according to Hou. However, she said, there is still a need to improve the development of high-end equipment, industrial materials and advanced theories.

Over the years, his team has grown from less than 20 to 200 people now. But women only make up about a quarter of team members.

As one of the few female leaders in science, Hou noticed the lack of representation of female scientists.

“Young female scientists are generally under more pressure, in large part because of the expectations of their families.”

Hou herself went through such a stage when her family members questioned her career choice and even berated her for her lack of presence as a mother.

Dedicated to work, Hou has little time for his family. She accidentally found her son’s diary one day and saw him write that “Mum doesn’t keep her promises. She said she would be there with me for the weekend, but every time she lies.”

Moreover, scientific work is not just brain work. It also takes a lot of physical work.

Previously, she was afraid of heights. But his job requires him to climb heights to install and test equipment. “I was scared. But I knew I had to get over my fear. So, I gathered my courage. Little by little, I got used to it. I don’t have the vertigo anymore,” she said.

Over time, talented young researchers come and go, which made him realize the importance of retaining young talent.

“I consider the promotion of budding scientists to be my main job at the moment. I want to see more promising scientists stay in this field, ”she said with great dedication.

She pays great attention to the members of her team. In fact, she often spends most of the day, sometimes even an entire day, patiently talking to them, encouraging them both academically and personally by offering potential solutions to their concerns.

“They are under great mental stress. They have to solve difficulties in their research as well as business in their daily life,” she said.

One day, a young man on his team lost consciousness for a while after days of hard work in the lab.

“I blame myself for that,” Hou almost sobbed as he said this. “Research occupied his life. He slept in the lab. As soon as he woke up he continued to work. I tried to persuade him to take a day off but he refused.”

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