Groundbreaking advancements are unfolding in the realm of ultrabroadband white laser sources, spanning the spectrum from ultraviolet to far infrared. These lasers, with applications ranging from large-scale imaging to femto-chemistry, telecommunications, laser spectroscopy, sensing, and ultrafast sciences, are at the forefront of technological innovation.
Yet, challenges persist, particularly in the selection of nonlinear mediums. Traditional solid materials, while efficient, face susceptibility to optical damage under high peak power conditions. Gas mediums, on the other hand, resilient to damage, often grapple with low efficiency and technical intricacies.
In a bold departure from convention, researchers at the South China University of Technology have turned to an unexpected candidate: water, as a nonlinear medium. Abundant and cost-effective, water demonstrates resilience to optical damage even under the influence of high-power lasers. Their findings, reported in Advanced Photonics Nexus, reveal that water-induced spectral broadening involves enhanced self-phase modulation and stimulated Raman scattering, yielding a supercontinuum white laser boasting a 435 nm 10 dB bandwidth and an impressive range from 478 to 913 nm.
Taking innovation a step further, the researchers combined water with a chirped periodic-poled lithium niobate (CPPLN) crystal, renowned for its robust second-order nonlinear power. This partnership not only extended the supercontinuum white laser’s frequency range but also flattened its output spectrum.
Prof. Zhi-Yuan Li, the corresponding senior author, notes, “The cascaded water–CPPLN module provides a long-lived, high-stability, and low-cost technical route for realizing a ‘three-high’ white laser with intense pulse energy, high spectral flatness, and ultrabroad bandwidth.”
The results from this water-CPPLN collaboration are promising. With a pulse energy of 0.6 mJ and a 10 dB bandwidth spanning more than an octave (413–907 nm), this ultrabroadband supercontinuum source holds potential in ultrafast spectroscopy and hyperspectral imaging.
Li emphasizes, “It offers high resolution across physical, chemical, and biological processes over extreme spectral bandwidths with a high signal-to-noise ratio. It opens an efficient route to creating 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 scientific research and applications.”
Source: SPIE