It is learned from the Department of Electronic Engineering of Tsinghua University that Associate Professor Liu Fang, a member of Professor Huang Yidong's team, led the researchers to develop a chip with integrated free electron light source and realized the thresholdless Cherenkov radiation for the first time in the world. It is the first time for our scientists to realize A major theoretical breakthrough, accelerating the free electron laser miniaturization process. Relevant research papers recently published in the international authoritative journal "Nature · Photon". Cherenkov radiation phenomenon was discovered in 1934 and played a key role in the discovery of elementary particles such as proton and neutrino oscillations. It is also one of the effective ways to realize free electron laser light source. Free-electron lasers are expected to be used to study condensed matter physics, material characteristics, anti-missile laser weapons, radar, and plasma diagnostics because of their short wavelength, high power, high efficiency and adjustable wavelength. In basic physics, Military, biomedical, information science and other fields have important application value. When interviewed by Science and Technology Daily reporter Huang Yidong, for example, said: "If the photons propagated in a material are likened to a series of high-speed trains traveling at constant speed, the charged particles of high energy only catch up with the tail of a train, that is, the speed of light Speed) to produce Cerenkov radiation. "At the moment, the minimum electron energy required to produce Cerenkov radiation in the wavelength band is at least 20,000 eV, which can only be achieved by large electron accelerators. This time, Liu Fang led the doctoral student Xiao Long et al. Found that artificial hyperbolic metamaterials, regardless of uniform velocity of electrons can produce radiation at a slow pace, that can be achieved without threshold Cerenkov radiation. Huang Yidong explained: "The metamaterials completely reverse the electronic energy conditions that generate radiation, and the required energy for accelerating electrons drops by several orders of magnitude, and the hard constraints that can not be achieved without large accelerators are also relieved." The evaluation concluded that the experimental results have overturned the inherent paradigm of large electron accelerators required by traditional free electron light sources, making it possible to study the interaction of flying electrons with micro / nano structures on a chip.