A joint research team led by Professor Li Zhiyuan from South China University of Technology and Academician Li Ruxin from the Shanghai Institute of Optics and Fine Mechanics, CAS, has developed an ultra-flat full-spectrum white-light pulsed high-power laser. The team put forward an innovative strategy of “synergistic nonlinear frequency up- and down-conversion” pumped by mid-infrared femtosecond intense laser.

The laser covers seven octaves spanning 200–25000 nm, with pulse energy of 1 mJ and spectral flatness of 17 dB. The findings were published in *Light: Science & Applications*, a top international optics journal.

Microscopic phenomena ranging from atomic electron transitions to molecular and lattice vibrations occur across bands from deep ultraviolet to far infrared. For over 60 years since the invention of lasers, scientists have sought a full-spectrum laser source to simultaneously observe these vastly different microscopic processes. Conventional lasers fail to meet the strict requirements for broad bandwidth, strong pulse energy and high spectral flatness at the same time.

This newly developed full-spectrum white-light laser overcomes those limitations. It is expected to pioneer a new paradigm of “single-source full-spectrum, synchronous snapshot” laser spectroscopy, advancing high-speed spectrography and pump-probe ultrafast spectroscopy. It unlocks broad prospects for fundamental research in physics, chemistry, materials science and biology, as well as applications including biomedical imaging, environmental monitoring and industrial inspection.

The system uses a 3.9 μm mid-infrared laser as the bridge source. Up-conversion extends the short wavelength edge to 200 nm deep ultraviolet, while down-conversion reaches 25 μm far infrared. The innovatively designed chirped periodically poled lithium niobate (CPPLN) crystal enables simultaneous generation of the 2nd to 12th high-order harmonics. Its up-conversion module achieves 40% conversion efficiency and 1.45 mJ output energy. The cascaded LN-AgGaSe₂ down-conversion module reaches 18% efficiency and 0.75 mJ output energy. Its overall performance outperforms similar supercontinuum laser systems.

The photon beam intensity of this laser system is 7–8 orders of magnitude higher than synchrotron radiation facilities. A single laser pulse can simultaneously probe physical and chemical processes across five energy scales: deep-UV electron transitions, visible electronic excitation, near/mid-infrared molecular vibrations and far-infrared lattice vibrations.

Dr. Hong Lihong, a joint postdoctoral researcher, is the first author. Professor Li Zhiyuan and Academician Li Ruxin serve as co-corresponding authors. Professor Li Zhiyuan’s research focuses on micro/nanophotonics, nonlinear optics, laser technology, topological photonics and quantum physics.