An intense white-light laser casts a dazzling rainbow, as demonstrated by an image from the experiments carried out by L. Hongs group at South China University of Technology. Credit: L. Hong et al., South China University of Technology.Water assists in a broad-spectrum supercontinuum white laser spanning an excellent series of wavelengths.Researchers are achieving notable development in producing ultra-broadband white laser sources, which span a broad series of wavelengths from ultraviolet to far infrared. These advanced lasers are used in a range of locations, including extensive imaging, femtochemistry, telecommunications, laser spectroscopy, sensing, and the field of ultrafast sciences.However, the pursuit faces difficulties, especially in the selection of proper nonlinear mediums. Conventional solid materials, while efficient, are vulnerable to optical damage under high peak power conditions. Gas mediums, though damage-resistant, commonly struggle with low efficiency and technical complications.Innovative Solutions with Water as a Nonlinear MediumIn a non-traditional move, researchers from the South China University of Technology recently turned to water as a nonlinear medium. Inexpensive and plentiful, water shows immune to optical damage, even under the impact of high-power lasers. As reported in the Gold Open Access journal Advanced Photonics Nexus, water-induced spectral widening involves boosted self-phase modulation and promoted Raman scattering, leading to a supercontinuum white laser with a 435 nm 10 dB bandwidth covering an outstanding 478– 913 nm range.Advances with Water-CPPLN CollaborationTaking development even more, researchers combined water with a chirped periodic-poled lithium niobate (CPPLN) crystal, known for its robust second-order nonlinear power. This partnership not just broadened the supercontinuum white lasers frequency variety however likewise flattened its output spectrum. According to the matching senior author Prof. Zhi-Yuan Li, “The cascaded water– CPPLN module offers a long-lived, high-stability, and inexpensive technical path for recognizing a three-high white laser with extreme pulse energy, high spectral flatness, and ultrabroad bandwidth.” The output from this water-CPPLN partnership is appealing. With a pulse energy of 0.6 mJ and a 10 dB bandwidth spanning more than an octave (413– 907 nm), this ultra-broadband supercontinuum source has potential in ultrafast spectroscopy and hyperspectral imaging. Li observes, “It uses high resolution throughout physical, chemical, and biological procedures over extreme spectral bandwidths with a high signal-to-noise ratio. It opens an effective route to producing a long-lived, high-stability, and inexpensive white laser with intense pulse energy, high spectral flatness, and ultrabroad bandwidth, paving a way for new possibilities in clinical research study and applications.” Reference: “Intense white laser of high spectral flatness via optical-damage-free water– lithium niobate module” by Lihong Hong, Yuanyuan Liu, Haiyao Yang, Lingzhi Peng, Mingzhou Li, Yujie Peng, Ruxin Li and Zhi-Yuan Li, 12 January 2024, Advanced Photonics Nexus.DOI: 10.1117/ 1. APN.3.1.016008.