Transferable ultra-thin multi-level micro-optics patterned by tunable photoreduction and photoablation for hybrid optics

• Main Authors: Lee, Hyub, Low, Mun Ji, Lim, Joel Chin Huat, An, Jianing, Suchand Sandeep, Chandramathi Sukumaran, Rohith, Thazhe Madam, Rhee, Hyug-Gyo, Murukeshan, Vadakke Matham, Kim, Young-Jin
• Other Authors: School of Mechanical and Aerospace Engineering
• Format: Article
• Language: English
• Published: 2020
• Subjects: Engineering::Mechanical engineering; Graphene Oxide; Diffractive Micro-optics
• Online Access: https://hdl.handle.net/10356/141895
• Institution: Nanyang Technological University

Next-generation hybrid optics will provide superior performances over traditional optics by combining the advantages of refractive, reflective, and diffractive optics and metasurfaces. Hybrid optics have been realized by integrating diffractive optical structures to the top surface of traditional bulk refractive or reflective optics. However, high-resolution manufacturing requirement of diffractive patterns on top of free-form refractive or reflective optical surfaces have hindered the wide-spread dissemination of hybrid optics. In this paper, we demonstrate a transferable ultra-thin micro-optics having multi-level transmittance and phase profiles which are arbitrarily patterned by tunable photoreduction and photoablation of graphene oxides (GO) using femtosecond (fs) direct laser writing. A 5 × 5 array of multi-level ultra-thin micro diffractive lens having a focal length of 15 mm was exemplarily patterned with real-time laser power control; the resulting spot size was smaller than 14 μm with the suppression of diffractive side peaks by 14.9% at the first order and 10.8% at the second order ones. This laser-patterned diffractive lens array was successfully transferred to the surface of a refractive cylindrical lens via polydimethylsiloxane (PDMS) as the flexible/stretchable substrate; the resulting optical performance agrees well with the theoretical simulation result. This new fabrication method will pave a way to novel hybrid optical systems.