‘Metalens’ could disrupt vacuum UV market —

Rice College photonics researchers have created a doubtlessly disruptive know-how for the ultraviolet optics market.

By exactly etching lots of of tiny triangles on the floor of a microscopic movie of zinc oxide, nanophotonics pioneer Naomi Halas and colleagues created a “metalens” that transforms incoming long-wave UV (UV-A) right into a targeted output of vacuum UV (VUV) radiation. VUV is utilized in semiconductor manufacturing, photochemistry and supplies science and has traditionally been pricey to work with, partially as a result of it’s absorbed by nearly all sorts of glass used to make typical lenses.

“This work is especially promising in gentle of latest demonstrations that chip producers can scale up the manufacturing of metasurfaces with CMOS-compatible processes,” mentioned Halas, co-corresponding creator of a metalens demonstration research printed in Science Advances. “This can be a elementary research, however it clearly factors to a brand new technique for high-throughput manufacturing of compact VUV optical parts and units.”

Halas’ staff confirmed its microscopic metalens might convert 394-nanometer UV right into a targeted output of 197-nanometer VUV. The disc-shaped metalens is a clear sheet of zinc oxide that’s thinner than a sheet of paper and simply 45 millionths of a meter in diameter. Within the demonstration, a 394-nanometer UV-A laser was shined in the back of the disc, and researchers measured the sunshine that emerged from the opposite aspect.

Research co-first creator Catherine Arndt, an utilized physics graduate scholar in Halas’ analysis group, mentioned the important thing function of the metalens is its interface, a entrance floor that’s studded with concentric circles of tiny triangles.

“The interface is the place all the physics is going on,” she mentioned. “We’re truly imparting a section shift, altering each how shortly the sunshine is transferring and the path it is touring. We do not have to gather the sunshine output as a result of we use electrodynamics to redirect it on the interface the place we generate it.”

Violet gentle has the bottom wavelength seen to people. Ultraviolet has even decrease wavelengths, which vary from 400 nanometers to 10 nanometers. Vacuum UV, with wavelengths between 100-200 nanometers, is so-named as a result of it’s strongly absorbed by oxygen. Utilizing VUV gentle at the moment usually requires a vacuum chamber or different specialised surroundings, in addition to equipment to generate and focus VUV.

“Typical supplies normally do not generate VUV,” Arndt mentioned. “It is made at the moment with nonlinear crystals, that are cumbersome, costly and infrequently export-controlled. The upshot is that VUV is kind of costly.”

In earlier work, Halas, Rice physicist Peter Nordlander, former Rice Ph.D. scholar Michael Semmlinger and others demonstrated they may rework 394-nanometer UV into 197-nanometer VUV with a zinc oxide metasurface. Just like the metalens, the metasurface was a clear movie of zinc oxide with a patterned floor. However the required sample wasn’t as complicated because it did not have to focus the sunshine output, Arndt mentioned.

“Metalenses benefit from the truth that the properties of sunshine change when it hits a floor,” she mentioned. “For instance, gentle travels sooner by air than it does by water. That is why you get reflections on the floor of a pond. The floor of the water is the interface, and when daylight hits the interface, slightly of it displays off.”

The prior work confirmed a metasurface might produce VUV by upconverting long-wave UV by way of a frequency-doubling course of known as second-harmonic era. However VUV is expensive, partially, as a result of it’s costly to control after it is produced. Commercially out there methods for that may fill cupboards as massive as fridges or compact automobiles and value tens of hundreds of {dollars}, she mentioned.

“For a metalens, you are making an attempt to each generate the sunshine and manipulate it,” Arndt mentioned. “Within the seen wavelength regime, metalens know-how has grow to be very environment friendly. Digital actuality headsets use that. Metalenses have additionally been demonstrated lately for seen and infrared wavelengths, however nobody had executed it at shorter wavelengths. And lots of supplies take up VUV. So for us it was simply an general problem to see, ‘Can we do that?'”

To make the metalens, Arndt labored with co-corresponding creator Din Ping Tsai of Metropolis College of Hong Kong, who helped produce the intricate metalens floor, and with three co-first authors: Semmlinger, who graduated from Rice in 2020,Ming Zhang, who graduated from Rice in 2021, and Ming Lun Tseng, an assistant professor at Taiwan’s Nationwide Yang Ming Chiao Tung College.

Assessments at Rice confirmed the metalens might focus its 197-nanometer output onto a spot measuring 1.7 microns in diameter, growing the ability density of the sunshine output by 21 occasions.

Arndt mentioned it is too early to say whether or not the know-how can compete with state-of-the-art VUV methods.

“It is actually elementary at this stage,” she mentioned. “Nevertheless it has lots of potential. It could possibly be made way more environment friendly. With this primary research, the query was, ‘Does it work?’ Within the subsequent section, we’ll be asking, ‘How a lot better can we make it?'”

Halas is Rice’s Stanley C. Moore Professor of Electrical and Laptop Engineering, director of Rice’s Smalley-Curl Institute and a professor of chemistry, bioengineering, physics and astronomy, and supplies science and nanoengineering. Nordlander, a co-author of the research, is the Wiess Chair and Professor of Physics and Astronomy, and professor {of electrical} and laptop engineering, and supplies science and nanoengineering.

Further research co-authors embrace Benjamin Cerjan and Jian Yang of Rice; Tzu-Ting Huang and Cheng Hung Chu of Academia Sinica in Taiwan; Hsin Yu Kuo of Nationwide Taiwan College; Vin-Cent Su of Nationwide United College in Taiwan; and Mu Ku Chen of Metropolis College of Hong Kong.

The analysis was funded by Taiwan’s Ministry of Science and Expertise (107-2311-B-002-022-MY3, 108-2221-E-002-168-MY4, 110-2636-M-A49-001), Nationwide Taiwan College (107-L7728, 107-L7807, YIH-08HZT49001), the Shenzhen Science and Expertise Innovation Fee (SGDX2019081623281169), the College Grants Committee/Analysis Grants Council of China’s Hong Kong Particular Administrative Area (AoE/P-502/20), the Division of Science and Expertise of China’s Guangdong Province (2020B1515120073), the Division of Electrical Engineering of Metropolis College of Hong Kong (9380131), the Taiwan Ministry of Schooling’s Yushan Younger Scholar Program, the Analysis Middle for Utilized Sciences at Taiwan’s Academia Sinica, the Robert A. Welch Basis (C-1220, C-1222), the Nationwide Science Basis (1610229, 1842494), the Air Drive Workplace of Scientific Analysis (MURI FA9550-15-1-0022) and the Protection Risk Discount Company (HDTRA1-16-1-0042).