It is well into the fall season on campus where a thin sweater is no longer warm enough. Shivering, I walked into the Rohm Building that houses Tsinghua’s Department of Electronic Engineering. My heart is filled with excitement but was also somewhat nervous. I am visiting the “Micro-nano Optoelectronics Lab.” It’s a mouthful to even say it. What is micro-nano optoelectronics?
Micro-nano optoelectronics is an interdisciplinary research of the interaction of photonic and matter in micro and nano structures. Research results can be applied to many fields such as information technology, energy, environmental science, biomedicine, including hot topics such as quantum communication and solar photovoltaic. The laboratory was established in 2004 and for the past 13 years, its research directions can be broadly divided into: photon and photoacoustic crystal, optical communication wavelength optical devices, silicon-based integrated devices, surface plasmon and the application of these four class. The research team includes Professor Huang Yidong (Changjiang Scholar), Associate Professor Zhang Wei, Associate Professor Feng Xue, Associate Professor Liu Fang, Associate Professor Cui Kaiyu, and more than 20 master and doctoral students.
Putting on clean clothes and walking into the laboratory, I was immediately drawn in by the bright white lights - 400 square meters of clean rooms are designed to flow like a maze. Each room can be separated and large areas are filled with manual fiber-optic couplers, plasma-enhanced chemical vapor deposition and other instruments. In a corner, there are special gas pressured bottles, air pumps and compressors - the entire space is cleverly designed and carefully laid out, giving immediate good vibes.
Looking around, there are cable-covered consoles and white blank displays, all the delicate components are breathing in a quiet laboratory. When I approached a microscope, I did not see what the professors called “important chip samples.” So Associate Professor Feng Xue had to enlighten me. “The components and structures studied in the laboratory are very microscopic, things not visible to our naked eyes,” he said. It is true what they say, that research on micro-nano structure requires patience and care. For the birth of a chip length of a few millimeters, from model designing, electron beam exposure, to ion etching process, to glueing, grinding and then to the test requires a total of at least 3 weeks.
“After students enter the post-graduate phase, the first step is to go through the ‘breaking point’ where they realize that conducting experiments is wildly different from solving a problem set. To complete the preparation and testing of a chip not only requires a certain familiarity with instruments, but also their own mathematical intuition in dealing with large amounts of data,” said Feng with a smile.
The latest scientific research in the laboratory is on integrated threshold-less Cherenkov radiation chip. Finding a method to reduce the huge electron energy threshold that produces Cerenkov radiation has been a scientific puzzle for decades. In 2014, Associate Professor Liu Fang found that the use of hyperbolic metamaterials allows for a threshold-free Cerenkov radiation. After more than two years of intensive experiments, Liu published the research results in Nature Photonics in 2017 and subverted the recognition of the traditional free electron light source, making it possible to study the flight on the chip and the interaction of electrons with the micro-nano structure.
Without realizing it, my two-hour visit had come to an end. I was impressed with the neat environment in the laboratory, the serious and hardworking students coupled with entertaining and knowledgeable professors. Here is a fertile land of theory and practice - professors and students are simulating, testing hypotheses, and conducting experiments. Although every step seems monotonous and boring, but it promises to culminate into an exquisite workmanship that ‘decrypts’ the microscopic world of photons.