New Materials For Fun with Photons

1
New Materials For Fun with Photons
Pierre Wiltzius, wiltzius_at_uiuc.edu

• Make materials with 3D microperiodicity photonic
  structures
• Develop new techniques for 3D fabrication
• Colloidal self-assembly and materials templating
  (Profs. P. Braun and Jennifer Lewis)
• Combine colloidal crystals and liquid crystals
• Biologically Inspired Self-Assembly
• Multibeam Holography

2
Multibeam Holography and Two-photon
Polymerization for Photonics
3
Number of beams?
uniform
1D
2D
4 beams needed for 3D pattern
4
Three beam interference
3 coherent beams
Interference pattern
2.5 µm hole size
5
4 beams
Intensity
Polarization
Beam direction
Same wavelength kikj
6
Polarization
Ex2Ey2Ez2
Each component interferes only with itself.
7
Stability
Mach-Zehnder interferometer
8
Setup

• Optical table, box
• Laser elsewhere

Sample in center (beams fictitious)
9
Turberfields method
Short pulse (10 ns) Ultraviolet light
Nature 404 (00) p. 53
10
Photoresist formulation
h?

• Spectra Group H-Nu535
• photo sensitizer
• absorbs photon
• transfers energy to PAG

• Shell EPON resin SU-8
• highest epoxide functionality commercially
  available
• ? high cross-linking density
• ? good sensitivity
• low molecular weight
• ? good solubility, high contrast

• Sartomer CD1012
• photoacid generator (PAG)
• generates acid, starting polymerization of epoxy

11
Recipe

• Mix photosensitizer photo acid generator
  amine SU-8 resin, in suitable solvent
• Spin coat or cast film
• Prebake to evaporate the solvent (2hr 65 ºC)
• Expose (514 nm, 1 J/cm2)
• Postbake (65 ºC, 25 min)
• Dissolve non-crosslinked parts (in PGMEA, 15 min
  - day)
• Critical point drying in CO2

12
Three-dimensional
13
ABC stacking
B
A
C
14
Various filling ratios
15
Large areas
16
Terraces
17
Two-photon patterning
using the same resist!
18
Outlook

• Optical measurements (reflection transmission
  spectra, diffraction, fluorescence lifetime, )
• Fill with liquid crystal
• Make replicas in higher refractive index
• Combine interference two photon lithographies
• Optimize resist formulation