Platinum ethynyl compound for optical limiting

摘要

Abstract: Nanosecond and picosecond studies have been carried out on a platinum ethynyl compound dissolved in tetrahydrofuran. Nonlinear absorption was observed at 532 nm using nanosecond pulses and at 1064 nm using picosecond pulses. The nonlinear absorption observed at 532 nm was found to have a long time constant associated with it indicating the presence of excited state absorption. A possible route for this excited state absorption may be single photon absorption from the ground state to the T$+1$/ excited state followed by excited state absorption from the T$+1$/ state. Strong nonlinear scattering was observed at 532 nm using nanosecond pulses and at 1064 nm using picosecond pulses. Optical limiting studies using 532 nm, nanosecond pulses revealed that below input fluences of 6 J/cm$+2$/ nonlinear absorption is the dominant limiting mechanism whereas above 6 J/cm$+2$/ there is significant nonlinear scattering. Picosecond experiments indicated that the scattering may, in part, be attributed to strongly absorbing scattering centers present in the solution, possibly originating from laser induced breakdown of the platinum ethynyl material. Excite-probe studies indicated that the time constant associated with the scattering is of the order of tens of milliseconds suggesting that this platinum ethynyl compound is a good candidate for use against picosecond to microsecond pulses. !9