R. Srinivasan
Polymer
The etching of polymethyl methacrylate (PMMA), by pulsed ultraviolet laser radiation [20-ns full width at half maximum (FWHM), 193 nm] can be increased more than threefold by overlapping both spatially and temporally laser pulses of 308 nm (20 ns FWHM) along with the 193 nm pulses. At a constant fluence of 193 nm, increasing the fluence of the 308 nm pulses progressively increases the etch depth/pair of pulses even though the fluence of the 308 nm radiation is kept below the value at which it would etch the polymer by itself at 1 Hz repetition rate. When a time delay of +300 to -400 ns is introduced between the two pulses, the 193 nm pulse being set as time zero, the enhancement due to pairing the pulses is found to be a maximum at nearly total overlap. A similar enhancement in the etching of PMMA by pulsed 248-nm laser radiation can be achieved by mixing 308 nm pulses with the 248 nm, and in the etching of polyethylene terephthalate, by mixing 351-nm laser pulses with 308-nm laser pulses. Chemical analysis of the solid polymeric product from the laser ablation of PMMA by 248 and 308 nm alone, and by a mixture of 248 and 308 nm laser radiation shows that the mixed laser radiation etches in a way that is chemically similar to pulsed 248-nm laser light and the effect can probably be attributed to an enhancement of the photoablation process.
R. Srinivasan
Polymer
S.E. Blum, K.H. Brown, et al.
Applied Physics Letters
R. Srinivasan
Proceedings of SPIE 1989
Yoshihisa Inoue, Naofumi Matsumoto, et al.
Journal of Organic Chemistry