Photosensitization agents for fs laser writing in PDMS

Abstract

This study aims at identifying compounds incorporated into Polydimethylsiloxane (PDMS) which produce large refractive index change under fs laser exposition, potentially leading to optimal writing of waveguides or photonic devices in such a soft host. Germanium derivative, titania and zirconite derivatives, benzophenone (Bp), irgacure-184/500/1173 and 2959 are investigated. We show a mapping of the RI index change relative to the writing speed (1 to 40 mm/s), the repetition rate (606 to 101 kHz) and the number of passes (1 to 8) from which we establish quantitative parameters to allow the comparison between samples. We show that the organic materials, especially irgacure-184 and benzophenone yield a significantly higher maximum refractive index change in the order of 10−2. We also show that the strongest photosensitivity is achieved with a mixture of organic/organo-metallic material of Bp + Ge. We report a synergetic effect on photosensitivity of this novel mixture.

Effect of Photoinitiators Doped in PDMS for Femtosecond-Laser Writing: Characterization and Outcomes

“…To understand the effect of aging on the studied materials after fs-laser writing, we performed a kinetic study. Our aging measurements were dependent on several writing parameters reported previously by us, such as a power range from 4 to 8 mW, a writing speed of 20 mm·s –1 , a repetition rate in the range of 101–606 kHz, λ writing of 515 nm, a pulse width of 250 fs, number of passes 1–8, and focus lens (NA) of 0.01 and 0.25. These parameters can vary between photoinitiators depending on their chemical sensitivity.…”

“…As shown in Figure a–e, physical characterization of the polymer was performed, and the results revealed that the highest RI change was 15 times larger than the best result obtained with pure PDMS, indicating the successful incorporation of the photoinitiator into the polymer network. A wavelength of λ = 515 nm was used to influence the course of the reaction during the writing, and this influence can be adjusted by changing the writing speed, the number of passes, and the repetition rate, as detailed in our previous report . This enhancement indicates the successful incorporation of the photoinitiators into the polymer network.…”

“…Composites were prepared according to our previously reported fabrication method . Typically, the PDMS prepolymer containing divinyl-end groups (Sylgard-184: base material) was mixed at a high speed with 2–4% (w/w) of a photosensitizing agent and subsequently ultrasonicated for 15 min.…”

“…The main challenge in this research is to acquire a transparent material that is suitable for fs-laser writing. Previously, we reported the fabrication of highly transparent composites of PDMS that have been evaluated through careful selection of the concentration ratio of the photosensitizer to PDMS and the choice of suitable solvents to acquire suitable conditions for fabrication …”

Single‐Step 3D Printing of Micro‐Optics with Adjustable Refractive Index by Ultrafast Laser Nanolithography

“…[15][16][17] Taking control over it enables 3D printing inside the volume of the already solidified/dried resins, for example, the is a rapidly increasing interest in writing waveguiding free-form structures and photonic bonds. [18][19][20] However, up to date the controlled cross-linking has only been exploited for bulky shape (volumetric) structures via refractive index modification inside the resin/resist. Thus, it invites to refer to as (3+1)D writing as was named in the original report.…”