Deep‐UV Lithography of Nanocomposite Thin Films into Magnetooptical Gratings with Submicron Periodicity

Abstract

Incompatibility of conventional magneto-optical (MO) materials with photonicsystem fabrication processes constitutes a major technological roadblock limiting their integration into photonic devices, especially for micro-or nano-patterned films. This paper proposes a photolithography approach toward MO micro-and nano-patterns, based on hybrid photosensitive matrices doped with magnetic nanoparticles to concentrations as high as 20%vol. The as prepared and characterized nanocomposite thin films exhibit excellent MO properties: a high Faraday rotation (5300 °/cm), comparable with the best existing materials that nevertheless require much more involved processes. The photosensitive matrices allow patterned gratings with a wide range of periods (100 µm to 500 nm), using a simple procedure at room temperature. The fabricated gratings exhibit welldefined regular structures and resolutions suitable for optical applications, including those at telecommunications wavelengths. Finally, direct applications of the proposed material and its associated process are demonstrated on two examples: 1) a magneto-optical grating in free-space and 2) in combination with a waveguide. The obtained optical and MO results are consistent with simulations.

Photocrosslinking and photopatterning of magneto-optical nanocomposite sol–gel thin film under deep-UV irradiation

“…As shown in a previous study 40 , the concentration of the MNP has an impact on the photopatterning. Patterns with various concentrations of MNP (between 0 and 20 vol%) were prepared using interference lithography (period 600 nm).…”

“…The photopatterning setup relies on a Braggstar (Coherent) nanosecond ArF Excimer laser emitting at 193 nm 40 . The beam section measures 3 × 6 mm 2 .…”

“…We recently introduced a process that relies on the synthesis of a photocurable sol-gel matrix in which magnetic nanoparticles (MNP) can be introduced 40 . Cobalt ferrite (CoFe2O4) MNPs were chosen because they exhibit large Faraday rotation in the 1400-1550 nm spectral range 41 , an important criterion for potential applications in telecommunication devices and photonic integrated circuits.…”

Electroless Cobalt Deposition on Dealloyed Nanoporous Gold Substrate: A Versatile Technique to Control Morphological and Magnetic Properties

“…A multiplicity of advanced fabrication techniques have been designed, combined together, and successfully used to tailor magnetic thin films to usage needs. Such techniques are mainly based on top-down approaches such as lithography and etching or on bottom-up approaches involving deposition and self-assembly processes [ 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 ].…”