Recently, Professor Li Zhiyuan's team at South China University of Technology collaborated with Academician Li Ruxin's team at the Shanghai Institute of Optics and Mechanics, Chinese Academy of Sciences. They innovatively proposed a novel strategy based on mid-infrared femtosecond laser pumping-the "synergistic nonlinear frequency up/down conversion" approach-successfully developing a full-spectrum white light pulsed laser source. This laser spans seven octaves from 200 to 25,000 nm, achieves a pulse energy of 1 mJ, and exhibits a spectral flatness of 17 dB. with a spectral flatness of 17 dB. The findings were published in the top-tier international optics journal Light: Science & Applications.
From electron transitions within atoms to molecular vibrations between atoms and solid lattice vibrations, diverse microscopic processes span characteristic bands ranging from deep ultraviolet to far-infrared. For over 60 years since the invention of lasers, scientists have pursued a laser source capable of covering the entire spectrum to simultaneously observe these microprocesses with vastly different energy scales. However, traditional laser sources suffer from limitations such as narrow spectral bandwidth, insufficient energy, or low spectral flatness, failing to simultaneously meet the stringent requirements of broad spectral coverage, high pulse intensity, and high spectral flatness.
The full-spectrum white light laser source proposed in this study overcomes these limitations. It is poised to pioneer a new paradigm in laser spectroscopy-"single-source full-spectrum, synchronous snapshot"-and open new frontiers in high-speed spectrography and pump-probe ultrafast spectroscopy. This breakthrough holds vast promise for fundamental research in physics, chemistry, materials science, and biology, as well as for applications in biomedical imaging, environmental monitoring, and industrial inspection.
Nonlinear Frequency Up- and Down-Conversion Synergy Enables High-Performance Deep-UV to Far-IR Full-Spectrum White-Light Laser
This white-light laser system employs a 3.9μm mid-infrared laser as the bridging source. Through up-conversion, the short-wavelength boundary is extended to the 200nm deep-ultraviolet region, while down-conversion extends the long-wavelength boundary to the 25μm far-infrared band. The team's innovatively designed chirped-periodic-polarized lithium niobate (CPPLN) crystal simultaneously generates 2nd to 12th-order harmonics. The upconversion module achieves 40% conversion efficiency with 1.45 mJ output energy. The downconversion module, featuring a cascaded LN-AGSe crystal architecture, achieves 18% conversion efficiency with 0.75 mJ output energy. The overall technical specifications significantly surpass those of comparable supercontinuum laser systems.
The system's photon beam intensity surpasses synchrotron radiation facilities by 7-8 orders of magnitude, enabling simultaneous detection of five physicochemical processes across distinct energy scales-deep ultraviolet electronic transitions, visible light electronic excitations, near-infrared and mid-infrared molecular vibrations, and far-infrared lattice vibrations-using a single laser beam or pulse.
Hong Lihong, a postdoctoral researcher jointly trained by South China University of Technology and the Shanghai Institute of Optics and Mechanics, Chinese Academy of Sciences, is the first author of the paper. Li Zhiyuan, Professor at the School of Physics and Optoelectronics, South China University of Technology, and Academician Li Ruxin of the Chinese Academy of Sciences are the co-corresponding authors. Professor Li Zhiyuan has long been engaged in theoretical, experimental, and applied research in micro-nano photonics, nonlinear optics, laser technology, topological photonics, and quantum physics.
