” The lasers required for these experiments are extremely effective, so its difficult to not warm up and damage the materials,” states Shan. “On the one hand, we want the material to be subjected to extremely intense laser light. On the other hand, we do not desire the material to absorb any of that light at all.”
The team discovered a “sweet area” to get around this, Shan says, where the frequency of the laser is fine-tuned in such a method to noticeably change the materials residential or commercial properties without imparting any undesirable heat.
Junyi Shan. Credit: Caltech
The researchers also say they discovered a perfect material to demonstrate this method. The material, a semiconductor called manganese phosphorus trisulphide, naturally absorbs only a little amount of light over a broad range of infrared frequencies. For their experiments, Hsieh, Shan, and associates utilized extreme infrared laser pulses, each lasting about 10-13 seconds, to rapidly change the energy of electrons inside the product. As a result, the material moved from an extremely nontransparent state to a highly transparent one for certain colors of light.
When the laser turns off, the material quickly goes back to its original state totally untouched. This would not be possible if the product had soaked up the laser light and warmed up due to the fact that it would take a long time for the product to dissipate the heat.
The technique works since the light modifies the distinctions between the energy levels of electrons in the semiconductor (called band spaces) without kicking the electrons themselves into different energy levels, which is what creates heat.
David Hsieh. Credit: Caltech
” Its as if you have a boat, and after that a big wave occurs and vigorously rocks the boat up and down without causing any of the passengers to drop,” explains Hsieh. “Our laser is vigorously rocking the energy levels of the product, which alters the materials homes, but the electrons stay put.”
Scientists have formerly theorized how this method would work. In the 1960s, Caltech alumnus Jon H. Shirley (PhD 63), put forth mathematical ideas about how to resolve for electron-energy levels in a product in the existence of light. Building on this work, Hsiehs Caltech team worked together with theorists Mengxing Ye and Leon Balents from UC Santa Barbara to calculate the predicted effects of laser lighting in manganese phosphorus trisulphide. The theory matched the try outs “amazing” precision, states Hsieh.
The findings, Hsieh says, mean that other researchers can now potentially use light to synthetically create materials, such as unique quantum magnets, which would have been otherwise difficult or even difficult to develop naturally.
” In principle, this method can change optical, magnetic, and lots of other residential or commercial properties of products,” says Shan. “This is an alternative method of doing materials science. Instead of making brand-new materials to understand various properties, we can take just one material and eventually give it a broad series of useful homes.”
Reference: “Giant modulation of optical nonlinearity by Floquet engineering” by Jun-Yi Shan, M. Ye, H. Chu, Sungmin Lee, Je-Geun Park, L. Balents and D. Hsieh, 8 December 2021, Nature.DOI: 10.1038/ s41586-021-04051-8.
The study was moneyed by the Army Research Office; the David and Lucile Packard Foundation; the National Science Foundation via the Institute for Quantum Information and Matter at Caltech and through UC Santa Barbara; the Gordon and Betty Moore Foundation; and the National Research Foundation of Korea. Other authors include Hao Chu (PhD 17), as well as Sungmin Lee and Je-Geun Park of Seoul National University.
The laser is being utilized to change the products degree of transparency.” The lasers required for these experiments are very powerful, so its hard to not warm up and harm the products,” says Shan. “On the one hand, we want the material to be subjected to extremely intense laser light. For their experiments, Hsieh, Shan, and associates utilized extreme infrared laser pulses, each lasting about 10-13 seconds, to rapidly change the energy of electrons inside the product. Rather than making new products to realize different properties, we can take simply one product and ultimately offer it a broad range of useful homes.”
A strong laser is seen lighting up a material in a low-temperature chamber. The laser is being used to change the products degree of openness. Credit: Caltech/David Hsieh Laboratory
Envision windows that can easily transform into mirrors, or extremely high-speed computers that run not on electrons however light. These are simply a few of the prospective applications that might emerge from optical engineering, the practice of using lasers to rapidly and momentarily change the homes of materials.
” These tools might let you change the electronic homes of products at the flick of a light switch,” states Caltech Professor of Physics David Hsieh. “But the innovations have been restricted by the issue of the lasers developing excessive heat in the products.”
In a brand-new study in Nature, Hsieh and his group, including lead author and college student Junyi Shan, report success at utilizing lasers to significantly shape the properties of products without the production of any excess harmful heat.