ORGANIC OPTICAL LIMITER WITH A STRONG NONLINEAR ABSORPTIVE RESPONSE

Molecules with weak ground-state absorption that form strongly absorbi ng excited states can be used in optical limiters, which can protect s ensors or human eyes from optical damage. Phthalocyanine complexes bea ring heavy atoms or paramagnetic groups or in solvents containing heav y atoms show optical limiting enhanced by excited tripler-state absorp tion. A nonhomogeneous distribution of indium tetra(tert-butyl)phthalo cyanine chloride along the beam path substantially enhances the excite d-state absorption, yielding an optical limiter with a linear transmit tance of 0.70 that can attenuate 8-nanosecond, 532-nanometer laser pul ses by factors of up to 540.