Fiber optic networks –must be fast-acting –must integrate into fiber systems –must operate at infrared wavelengths Eye protection –scope sights –binoculars –must operate at both visible and infrared wavelengths Applications Optical Limiters Acquisition of spectroscopic and computational instruments for undergraduate education and research in nonlinear optical materials James J. Butler, Pacific University, DMR The optical limiters in this investigation use nonlinear absorbers. The percentage of light that these materials absorb increases with the intensity of the incident light. Dim Light In Dim Light Out Bright Light In Dim Light Out Optical limiters are devices that can be used to control the brightness of the light that reaches a sensitive optical component

Nonlinear Transmission Data and Models Optical Limiting in Capillary Waveguides at Infrared Wavelengths Simulations suggest the primary pathway into highly absorbing triplet state changes from single-photon absorption at 900nm to two-photon absorption at 1050nm Possible explanation: The T 0 band may be narrower and have a lower edge near the same energy as the S 1 band so that transitions from S 1 to T 0 at 1050nm are unlikely Silica capillaries with 10 μm internal diameter filled with 0.2mM solution of OsPZnOs dissolved in DMSO Optical limiting response shows significant enhancement at 1050nm * Experiments are continuing at Pacific University with equipment purchased from this grant The data shown here was taken by the PI and collaborators at the Naval Research Laboratory (NRL) in the summer of 2006.* The modeling of the data was done by undergraduates at Pacific University in James J. Butler, Pacific University, DMR

Molecular Modeling Results Undergraduate student Phillip Cox, now a sophomore, started working on the project during the summer of His work has extended the work into new metals. SCIENTIFIC PROGRESS Recent Results A computational study of the effect oxidation state and ligand in tin phthalocyanines was completed. Simulated electronic absorption spectra for ground singlet, S0, first excited singlet, S1, and first excited Triplet states were calculated and are shown to the right. Energy of electronic state to state transitions were calculated and are illustrated to the right. The tin (II) and tin (IV) dichloride compounds show similar characteristics and theoretical absorbance ratios for excited singlet and triplet states can be calculated from the spectra. These are tabulated below. The tin (IV) oxide has no predicted absorbance from the excited electronic states. This is apparently caused by the degenerate highest occupied molecular orbitals with electron density concentrated on the oxygen. The MO visualizations for this compound are illustrated to the right. SOFTWARE & HARDWARE IMPLEMENTATION Two new 8-core Apple Mac Pro computers were purchased by Pacific University and employed on this project in mid-July. The upgrade in computers has greatly accelerated the rate at which calculations can be completed. Software License supported by internal Faculty Development Grant from Pacific University to co-Pi Johnson Sn(IV)=O Pc Molecular orbital visualizations (red-blue = occupied orbitals & yellow-green = virtual orbitals James J. Butler, Pacific University, DMR