ABSTRACT
Blister formation occurs when a laser pulse interacts with the underside of a polymer film on a glass substrate and is fundamental in Laser-Induced Forward Transfer (LIFT). We present a novel method of controlling blister formation using a thin metal film situated between two thin polymer films. This enables a wide range of laser pulse energies by limiting the laser penetration in the film, which allows us to exploit nonlinear interactions without transmitting high intensities that may destroy a transfer material. We study blisters using a helium ion microscope, which images their interiors, and find that laser energy deposition is primarily in the metal layer and the top polymer layer remains intact. Blister expansion is driven by laser-induced spallation of the gold film. Our work shows that this technique could be a viable platform for contaminant-free LIFT using nonlinear absorption beyond the diffraction limit.
ABSTRACT
We report ultrafast-laser-induced photochemical, structural, and morphological changes in a polyimide film irradiated at the polymer-glass interface in back-incident geometry. Back-illumination creates locally hot material at the interface leading to a confined photochemical change at the interface and a morphological change through a blister formation. The laser-induced photochemical changes in polyimide resulted in new absorption and luminescence properties in the visible region. The laser-treated polyimide exhibited photoluminescence anisotropy resulting from formation of ordered polymer upon irradiation by linearly polarized ultrashort laser pulses. Confocal fluorescence microscopy resulted in similar observations to the bulk. Reflection-absorption infrared spectroscopy and X-ray photoelectron spectroscopy together indicated confinement of laser-induced chemical changes at the interface.
