Gong Qihuang's team Successful development of high spatial and temporal resolution optoelectronic imaging system
Femtosecond-nanometer space-time resolved optical experiment system.
"We just want to pursue the limits in time and space." Gong Qihuang told China Science News. Supported by the National Natural Science Foundation of China, Gong Qihuang's team, a member of the Chinese Academy of Sciences and a professor at Peking University, has been working for a long time to challenge the frontiers of science in "spatio-temporal limit" research, helping people to continuously broaden the boundaries of cognition.
The team has successfully developed a high spatio-temporal resolution optoelectronic imaging system. It allows people to see nanoscale structures and their temporal evolution on the nanometer (10-9 m) scale (space) and femtosecond (10-14 s) scale (time), with both energy and momentum resolution. The system will drive revolutionary developments in basic and applied research in the fields of iso-excited photonics, quantum materials, semiconductor materials, and their related interdisciplinary disciplines.
Significance of photonics
At the "2020 China Photonics Industry Summit", Gong Qihuang delivered a keynote speech entitled "The Future of Photonics".
The term photonics first appeared in 1970: Dutch scientist Arie Poldervaart first introduced Photonics - "the science of photons as information carriers" and "the science of photons as energy carriers". Photonics - "the science of photons as energy carriers". At the 1994 Xiangshan Conference, a definition of photonics was clearly given: the science that studies the behavior of photons as carriers of information and energy and their applications, and, broadly speaking, photonics is the science of photons and their applications.
After the advent of laser technology in the 1960s, on average a Nobel Prize was awarded every three years for photonics achievements: many prizes in physics, and even in chemistry, physiology or medicine, have done much work with photonics techniques. Photonics is not only advancing science, but is playing an increasing role in human progress.
If the 20th century was the century of electricity, then the 21st century is the century of light.
The important research fields and directions of photonics include photonic devices and photoelectric integration, laser devices and applications, photoelectric detection and sensing, photoelectric control and processing, optical transmission and optical exchange, micro and nano optoelectronics integration, quantum optics and quantum information, microwave photonics, and biomedical photonics. In fact, more importantly, it is a system engineering with the technology and application of optical processing and manufacturing, photoelectric imaging, spectroscopy and light processing system, as well as photoelectric measurement, photoelectric detection, and really the final formation of optical instruments and systems.
At present, the technology in the fields of optical information processing, optical display, optical detection and sensing is iteratively updated, and optoelectronic functional devices are constantly developing in the direction of ultra-high density, ultra-fast speed and ultra-low power consumption, and the development of composite micro-nano devices based on new materials has become a major trend. This requires people to figure out the photoelectric ultrafast dynamics process in the micro and nano scale. However, for a long time, China has been lacking in the accumulation of research in related fields.
Time and space dimensions to achieve the resolution limit
In 2016, under the funding of the National Major Research Instrument Development Project, Gong Qihuang's team started to develop the "Femtosecond-Nanometer Spatio-Temporal Resolution Optical Experiment System".
"Our goal is to achieve the resolution limit in the spatial and temporal dimensions (nanometer scale and femtosecond scale) and combine the two to see extremely fast change processes at a very small spatial scale, thus broadening the boundary of people's cognition." Gong Qihuang said.
While the human eye can distinguish objects the size of 100 microns and see objects the size of 200 nanometers with the help of an optical microscope, an electron microscope allows one to see objects the size of 0.1 nanometers. With such a system, it is like having a special ultra-high-speed camera with 10 femtosecond resolution (10 million times faster than a high-speed camera) and the spatial resolution of an electron microscope, which can see structures smaller than 10 nanometers clearly.
"No one has done this system before, and there is no international experience to draw from, so we have to keep trying, and a lot of times it's trial and error." Liu Yunquan, a team member and professor at Peking University, told China Science News, "Sometimes it feels as if everything is done right, but we just can't get the ideal signal, and we can only check and optimize it over and over again, drilling into every detail and debugging it repeatedly so that we can get the optimal index."
"The Femtosecond-Nanometer Space-Time-Resolved Optical Experiment System is a new research tool in the field of semiconductor materials and surface physics because it can see the surface shape of materials and observe the dynamics of electrons in real time. The system can reveal the interaction between excited carriers and excitons, phonons, defects, etc. It can be used for the imaging of spatio-temporal evolution of femtosecond iso-excited fields, the spatio-temporal characterization of topological defects, the functional characterization and manipulation of micro- and nano-iso-excited components, and the dynamics of hot carriers in metal-semiconductor and two-dimensional materials.
Group photo of the team
The team has developed the first ultra-fast extreme ultraviolet photoemission electron microscope based on gas high harmonics in China, and characterized the spatial, energy and time resolution, and the performance index has reached the international leading level. The successful development of the extreme ultraviolet photoemission electron microscope provides an advanced platform for dielectric photonic devices and ultrafast photophysics research at the micro- and nano-scale, and also provides a powerful research tool for human beings to explore the unknown material world, discover new scientific laws and realize technological changes.
At present, the Femtosecond-Nanometer Spatio-Temporal Resolution Optical Experiment System (FTS-NRTES) has demonstrated powerful capabilities in related disciplines by combining nanometer-femtosecond extreme spatio-temporal resolution functions. With the help of the system, they have made some important research results in the field of carrier dynamics of various systems such as equipartitioned excitonic metal nanostructures, semiconductor heterostructures and chalcogenide materials, as well as the photomechanical characterization of ice-single crystal micro and nano fibers. During the development of the project, the team has published more than 160 papers in Science, Nature and other journals; around the project development process, important technical difficulties and breakthroughs, 25 patents have been applied for, 20 of which have been granted.
"We have entered the first echelon of the field." Gong Qihuang said, "After these years of refinement, the team has a good accumulation of technology and has achieved first-class results using the system. The project team is continuously improving its performance, perfecting instrument management, and opening it to domestic and international users to improve the efficiency of using large instruments and serve scientific and technological innovation and social needs."
In answer to a question from the China Science News.
Science China: What is the current level of the instrument in the international arena? What is the next step, the team's research focus or the development direction of the field?
Gong Qihuang: This is one of the world's most advanced extreme spatio-temporal resolution experimental systems, only a few countries in the international development of related equipment. This is currently the only system in China, and some of its indicators have reached the international leading level.
In the next step, we will continue to focus on fundamental research to provide support for frontier exploration and for people to broaden their knowledge boundaries. For example, in the research of new states of matter or new change processes in special two-dimensional materials and nano-materials, we allow people to re-understand the change of matter in a new perspective and expand the understanding of materials, condensed matter, physics and optics. In terms of applications, we provide support for some small-scale devices, such as chip detection and diagnosis, detection and performance characterization of highly sophisticated scientific devices.
