New discovery could lead to new laser and photocatalyst technologies

A team of researchers has made a groundbreaking discovery regarding the trapping of optical waves in three-dimensional randomly packed micro- or nanoparticles. This advancement, made possible by a significant boost in computing capability, has solved a decades-long mystery and holds tremendous potential for various applications including lasers and photocatalysts.

The concept of Anderson localization, proposed by Philip W. Anderson in 1958, revolutionized contemporary condensed physics by explaining how electrons in a material can either move freely to conduct current or become trapped and act as insulators. This principle extended to both quantum and classical realms, encompassing electrons, acoustic waves, water, and gravity.

While Anderson localization had been extensively studied in different contexts, the localization of electromagnetic waves in three dimensions remained unclear despite four decades of research. Previous experimental reports of three-dimensional light localization had been met with skepticism due to experimental artifacts or other physical effects being attributed to the observed phenomena.

This uncertainty sparked an intense debate regarding the existence of Anderson localization of electromagnetic waves in three-dimensional random systems. Conducting conclusive experiments to eliminate all artifacts proved exceptionally challenging, leading the researchers, led by Prof. Hui Cao, to resort to numerical simulations.

However, simulating large three-dimensional systems had previously been hindered by limited computing power and memory. The collaboration between Prof. Cao’s team and Flexcompute, a company specializing in accelerating numerical solutions, proved instrumental in overcoming this hurdle. Flexcompute’s FDTD Software Tidy3D enabled simulations that ran exponentially faster than previous methods, allowing the researchers to explore various random configurations, system sizes, and structural parameters to determine the possibility of three-dimensional light localization.

The international research team, which included Prof. Alexey Yamilov, Dr. Sergey Skipetrov, Prof. Zongfu Yu, and Dr. Tyler Hughes, alongside Dr. Momchil Minkov from Flexcompute, successfully conducted artifact-free simulations that put an end to the long-standing debate. Their study yielded accurate numerical results and provided two key findings: the impossibility of localizing light in three-dimensional random aggregates of dielectric materials like glass or silicon, which explained the failures of past experimental efforts, and the unambiguous evidence of Anderson localization in random packings of metallic spheres.

The discovery of Anderson localization in metallic systems, despite their light absorption properties, presents exciting opportunities. The researchers found that even with losses incurred by common metals like aluminum, silver, and copper, Anderson localization still occurred.

The robustness and strength of this effect make it particularly significant. Aside from resolving long-standing questions, this breakthrough opens up new avenues for applications in lasers and photocatalysts.

The confinement of light in porous metals can enhance optical nonlinearities, light-matter interactions, and enable control over random lasing and targeted energy deposition. With these promising outcomes, the research paves the way for numerous potential advancements in the field.

Source: Yale University

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