Spatial Resolution, Surface Roughness Improved in Laser Fabrication

A research group at Osaka University in Suita, Japan, reports that the spatial resolution of two-photon polymerization laser fabrication and the surface roughness of objects created using the technique may be improved with the addition of radical quenchers and control of scanning pitch, respectively.

Presenting their findings in the Feb. 14 issue of Applied Physics Letters, the scientists conclude that the minimum resolution of the technique is limited by the material properties of the polymer rather than the laser setup and that the surface roughness is sufficiently low for use in photonic applications.
In their experiments, they employed a Ti:sapphire laser producing 80-fs pulses of 780-nm radiation at 80 MHz to fabricate various objects by two-photon absorption in a resin. Adding a radical quencher and an initiator to the resin resulted in the confinement of the photopolymerization reaction and improved spatial resolution to approximately 100 nm. The resolution could be improved further, but doing so would result in softer polymerized parts as a consequence of the chemical properties of the material.

To investigate surface roughness, the scientists produced a series of structures with 12 × 12-µm end faces at different scanning pitches. They determined that surface roughness improves to 4 to 11 nm with the degree of overlap of the voxels and is slightly dependent on the laser power.