Processing and fabrication of micro-structures by multiphoton lithography in germanium-doped arsenic selenide

Abstract

This work reports the processing and properties of a new chalcogenide glass film that can be photo-patterned by multiphoton lithography (MPL) with enhanced post-fabrication stability. Thermally evaporated germanium-doped arsenic selenide [Ge 5 (As 2 Se 3) 95 ] thin films were photo-patterned using the output of a mode-locked titanium:sapphire laser. The morphology, chemical structure, and optical properties of the material were studied before and after photo-patterning and compared for their long-term aging behavior and stability to previously investigated arsenic trisulfide (As 2 S 3) films fabricated using similar MPL conditions. Relative to As 2 S 3 , thermally deposited Ge 5 (As 2 Se 3) 95 is found to offer higher photosensitivity and greater chemical stability after photo-patterning, as evidenced by lack of ageinduced crystallization and reduced feature degradation over a four year aging period. These findings demonstrate the suitability of a new photo-patternable material for the creation of robust, long-lived functional infrared anti-reflective coatings and meta-optics.

Advances in femtosecond laser processing of optical material for device applications

“…Laser‐processed chalcogenide glasses (ChGs) have been investigated as a means for creating infrared (IR) functional devices . ChGs are materials that are mostly made of one or more of the following chalcogen elements: sulfur (S), selenium (Se), and tellurium (Te), but excluding oxygen (O).…”

“…As 2 S 3 has high transparency in the IR (620 nm to 11 μm), an optical bandgap of E g = 2.35 eV ( λ = 517 nm), high refractive index ( n ∼ 2.45‐2.53), and potential for optical applications . Raman spectroscopy has shown that thermal deposition of As 2 S 3 breaks the bulk network solid into As 4 S 4 , As 4 S 6 , and S 8 molecular clusters . The As 2 S 3 films are most photosensitive if they contain a high fraction of these molecular clusters with homopolar bonds .…”

“…After exposure, a chemical etchant (usually an amine) can be used to selectively remove the unexposed material, revealing the patterned structure. Film deposition and subsequent processing has been shown to influence the size, shape, composition, durability, and optical properties of the photopatterned structures . DLW has been used to create waveguides, nanowires, woodpile and chiral gyriod photonic crystals in As 2 S 3 films .…”

“…Film deposition and subsequent processing has been shown to influence the size, shape, composition, durability, and optical properties of the photopatterned structures . DLW has been used to create waveguides, nanowires, woodpile and chiral gyriod photonic crystals in As 2 S 3 films . These types of structures can have direct applications in optics and electronics including sensors, detectors, acousto‐optics, and imaging and monitoring systems …”

“…The etchant used was neat ethanolamine and the 3D structures sizes were as small as 200 nm in width. Ge 5 (As 2 Se 3 ) 95 was observed to possess higher photosensitivity and increased stability when compared to As 2 S 3 . Thermally deposited As 2 S 3 films and photopatterned structures surfaces have been found to become degraded when exposed to ambient conditions such as light and humidity .…”