Water produces broad-spectrum supercontinuum white laser light with an impressive range of wavelengths. Researchers have made significant progress in creating ultra-broadband white-light laser sources covering a wide range of wavelengths from ultraviolet to far-infrared. These advanced lasers are used in a variety of fields, including broad imaging, microchemistry, telecommunications, laser spectroscopy, sensing and ultrafast science.

Experimental photos from Hong Lihong’s team at South China University of Technology show that a strong white light laser projects a brilliant rainbow. Image source: L.Hong et al., South China University of Technology.

However, this pursuit faces challenges, especially in selecting a suitable nonlinear medium. Although traditional solid materials are highly efficient, they are prone to photodamage under high power peak conditions. Although gaseous media are not easily damaged, they generally suffer from low efficiency and technical complexity.

Researchers at South China University of Technology recently took an unconventional step and looked at water as a nonlinear medium. Water resources are abundant and the price is low. Even under the action of high-power laser, it will not cause damage to the optics. As reported in the open-access journal Advanced Photonics Nexus, the water-induced spectral broadening involves enhanced self-phase modulation and stimulated Raman scattering, resulting in a supercontinuum white-light laser with a 10-dB bandwidth of 435 nanometers covering the impressive 478-913 nanometer range.

In a further innovation, the researchers combined water with chirped periodically poled lithium niobate (CPPLN) crystals, which are known for their powerful second-order nonlinear power. This collaboration not only expands the frequency range of the supercontinuum white-light laser, but also makes its output spectrum flatter. According to the corresponding author Professor Li Zhiyuan: "The cascaded water-CPPLN module provides a long-life, high-stability, and low-cost technical route for the realization of a 'three-high' white light laser with strong pulse energy, high spectral flatness, and ultra-wide bandwidth."

The output of this water-CPPLN cooperation project is promising. This ultra-broadband supercontinuum light source has a pulse energy of 0.6mJ and a 10dB bandwidth over one octave (413-907nm), and has potential in ultrafast spectroscopy and hyperspectral imaging.

Li Zhiyuan pointed out: "It can provide high resolution of physical, chemical and biological processes with high signal-to-noise ratio over extreme spectral bandwidth. It opens up an effective way to create long-life, high-stability and cheap white lasers with strong pulse energy, high spectral flatness and ultra-wide bandwidth, paving the way for new possibilities in scientific research and applications."

Compiled source: ScitechDaily