Detailed Experiment-Theory Comparison of Mid-Infrared Metasurface Perfect Absorbers

• Main Authors: Naoki To, Saulius Juodkazis, Yoshiaki Nishijima
• Format: Article
• Language: English
• Published: MDPI AG 2020-04-01
• Series: Micromachines
• Subjects: metasurface; mid infrared absorption; perfect absorption
• Online Access: https://www.mdpi.com/2072-666X/11/4/409

Realisation of a perfect absorber <inline-formula> <math display="inline"> <semantics> <mrow> <mi>A</mi> <mo>=</mo> <mn>1</mn> </mrow> </semantics> </math> </inline-formula> with transmittance and reflectance <inline-formula> <math display="inline"> <semantics> <mrow> <mi>T</mi> <mo>=</mo> <mi>R</mi> <mo>=</mo> <mn>0</mn> </mrow> </semantics> </math> </inline-formula> by a thin metasurface is one of the hot topics in recent nanophotonics prompted by energy harvesting and sensor applications (<inline-formula> <math display="inline"> <semantics> <mrow> <mi>A</mi> <mo>+</mo> <mi>R</mi> <mo>+</mo> <mi>T</mi> <mo>=</mo> <mn>1</mn> </mrow> </semantics> </math> </inline-formula> is the energy conservation). Here we tested the optical properties of over 400 structures of metal–insulator–metal (MIM) metasurfaces for a range of variation in thickness of insulator, diameter of a disc and intra-disc distance both experimentally and numerically. Conditions of a near perfect absorption <inline-formula> <math display="inline"> <semantics> <mrow> <mi>A</mi> <mo>></mo> <mn>95</mn> <mo>%</mo> </mrow> </semantics> </math> </inline-formula> with simultaneously occurring anti-reflection property (<inline-formula> <math display="inline"> <semantics> <mrow> <mi>R</mi> <mo><</mo> <mn>5</mn> <mo>%</mo> </mrow> </semantics> </math> </inline-formula>) was experimentally determined. Differences between the bulk vs. nano-thin film properties at mid-IR of the used materials can be of interest for plasmonic multi-metal alloys and high entropy metals.