Photonic crystals with defect structures fabricated through a combination of holographic lithography and two-photon lithography

Abstract

This paper presents the capability of direct laser writing of complex defect structures in holographically formed three-dimensional photonic crystals in dipentaerythritol penta/hexaacrylate (DPHPA) monomers mixed with photoinitiators. The three-dimensional photonic crystal template was fabricated through prism-based holographic lithography. Defect structures are fabricated through the two-photon polymerization excited by a femtosecond laser. The strengths of two optical lithographic techniques are combined with holographic lithography providing a rapid and large area microfabrication and two-photon lithography providing flexibility in fabrication of defect structures. The optical fabrication process is simplified in the negative tone DPHPA without prebake and postexposure bake as is required of SU-8 while maintaining a capability for constructing photonic structures with small features.

Fabrication of periodic micro-structures by holographic lithography

“…Depending on laser wavelength, exposure can be achieved via linear [5] or nonlinear absorption [6]. HL allows fabricating periodic structures over a large area relatively fast and that makes this technique attractive and promising for mass-fabrication of functional devices such as photonic crystals [7][8][9][10] or scaffolds [11,12]. HL has certain advantages over the direct laser writing (DLW) technique [13] due to the rapid fabrication of periodic structures.…”

Rapid Prototyping across the Spectrum: RF to Optical 3D Electromagnetic Structures

“…Complex defect structures can enable the control of light propagation through localization around the defect which can also dramatically reduce emission lifetime [110]. Two-photon lithography [111] has also been used to direct write defect structures in holographically fabricated 3D photonic crystals ( Figure 10).…”

“…The combination of two optical lithographical techniques viz. holographic lithography, which can provide coverage over large areas, and two-photon lithography, which can fabricate defects of high resolution spatial placement and shape, leverages the advantages of both methods to fabricate nanoscaled features over very large areas in a relatively short time period [110]. One illustrative example shows light-trapping at 632nm based on a 2D hexagonal lattice with a missing central pillar resulting in a micro-cavity on the surface of a SiO2 prism.…”

“…Previously published work has demonstrated the use of two-photon lithography to create defects in photonic crystal templates, such as a large area woodpile in SU-8 as well as dipentaerythritol penta/hexaacrylate (DPHPA) with photoinitiator. In addition to multiphoton lithography, focused EBID has also been effectively used to create 3D photonic crystals with predefined defects for extreme light localization [110]. Nanoscaled additive manufacturing processes have also been used for nanoscale object manipulation, mask repair and fabrication of periodic arrays.…”

“…(a) 3D nanostructure patterned with mask 1 over a large area, limited only by the size of the mask, (b) (110) cross-sectional view of the structure in (a), (c) Top view of the same structure (red arrow points to an ~100-nm structure in width). Inset shows modeling (arrow indicates the direction of polarization of the exposure light).…”