Abstract
Background: Optical components with high damage thresholds are very desirable in intense-light systems. Metalenses, being composed of phase-control nanostructures with peculiar properties, are one of the important component candidates in future optical systems. However, the optothermal mechanism in metalenses is still not investigated adequately. Methods: In this study, the optothermal absorption in transmissive metalenses made of silicon nanobricks and nanoholes is investigated comparatively to address this issue. Results: The geometrical dependencies of nanostructures’ transmittance, phase difference, and field distribution are calculated numerically via simulations. To demonstrate the optothermal mechanism in metalenses, the mean absorption efficiencies of the selected unit-cells, which would constitute metalenses, are analyzed. The results show that the electric field in the silicon zone would lead to an obvious thermal effect, and the enhancement of the localized electric field also results in the strong absorption of optical energy. Then, two typical metalenses are designed based on these nanobricks and nanoholes. The optothermal simulations show that the nanobrick-based metalens can handle a power density of 0.15 W/µm2, and the density of the nanohole-based design is 0.12 W/µm2. Conclusions: The study analyzes and compares the optothermal absorption in nanobricks and nanoholes, which shows that the electric-field distribution in absorbent materials and the localized-field enhancement are the two key effects that lead to optothermal absorption. This study provides an approach to improve the anti-damage potentials of transmissive metalenses for intense-light systems.
Highlights
Intense-light systems increasingly impact laser fabrication [1], directed energy [2], renewable energy [3,4], etc
Due to the electromagnetic resonant effect, the electric field is usually localized in nanostructures [12], which would lead to optothermal absorption
The optothermal absorption in transmissive metalenses made of silicon nanobricks and nanoholes was investigated comparatively
Summary
Intense-light systems increasingly impact laser fabrication [1], directed energy [2], renewable energy [3,4], etc. Due to the electromagnetic resonant effect, the electric field is usually localized in nanostructures [12], which would lead to optothermal absorption. TThheessttuuddiieeddttrraannssmmiissssiivveemmeettaalleennsseessaarreeccoommppoosseeddooffppeerriiooddiiccssiilliiccoonn((SSii))nnaannoobbrriicckkss oorr nnaannoohhoolleess oonn SSiiOO22ssuubbsstrtraatetesswwitihthththeessaammeehheeigighhttHH ==220000nnmmaanndd tthhee ssaammee llaattttiiccee ppeerriiooddPP==60600n0mn,mas, sahsoswhnowinnFinguFrieg1u.rEea1c.h uEnacith-ceulnl iht-acseallnhaansosatrnuacntuorsetrwucithuraerwecittahn-a grueclatarnsghualpaer dsheascpreibdeedscbryibleedngbtyhleLnb gotrhLLh,baonrdLhw, iadntdh wWibdothr WWhb. opr-SWi ihs. In metalenses made of nanostructures, the electric field distributes nonuniformly due to the localized-field effect.
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