Optimization of passive optical limiters

In this dissertation, we investigate the phenomenon of passive optical limiting, which serves the purpose of protecting sensors and eyes from strong incident laser pulses. I introduce several different nonlinear mechanisms and evaluate their performance in terms of important criteria for optical limiting. The remaining chapters are devoted to the experimental optimization of different types of optical limiters.; Many designs of optical limiters are based on nonlinear absorption (NLA). The best limiting result from NLA was previously obtained in a 3-cell tandem limiter based on strong excited-state absorption. A detailed description of the concept of tandem limiters is given and experimental results based on NLA are presented. Thermally induced nonlinear refraction due to the absorbed light energy reduces the efficiency of the tandem limiters. However, we propose and demonstrate a novel limiter design utilizing this thermal effect to enhance the limiting performance.; Previously, the nonlinear scattering (NLS) properties of carbon black suspensions (CBS) were used to produce good limiting results. Another NLS limiter design with scattering elements mixed in an index-matching fluid is proposed and compared to the CBS limiter. We have also applied liquid crystals to the design of limiters. This new mechanism is based on the polarization change due to induced nonlinear birefringence. An attractive property of this design is its insensitivity to wavelength.; Finally a dual-focus limiter system is presented. This design combines nonlinear absorption, nonlinear refraction and nonlinear scattering. Experimental results show that the output energy of nanosecond 532 nm pulses through a 1.5 mrad aperture placed after a final focusing lens is held below 1μJ for inputs greater than 14.5 mJ without damage while the linear transmittance is 21%.