The vulnerability of human eyes and sensing devices to high power laser radiation presents a critical need in both the military and private sectors for protection devices. These devices must permit normal eye and sensor functions while blocking all damaging wavelengths when subjected to high power radiation. Optical power limiting provides just such a mechanism for this type of passive protection. Optical limiting has been investigated in a number of materials with distinct nonlinear mechanisms 1. Of these materials, the most widely investigated are: (1) Organic and organometallic molecules which rely on reverse saturable absorption (RSA). The more promising RSA materials include heavy-atom-substituted phthalocyanines 2,3, porphyrins 4, and fullerenes 5. The phthalocyanines have demonstrated superiority at the most commonly investigated wavelength of 532 nm, and show optical power limiting for a range of wavelengths in the visible spectral region. Very recent studies have shown enhanced properties of fullerenes in the red and near-IR 6,7,8,9. (2) Colloidal carbon suspensions, which rely on nonlinear scattering. While they yield broadband limiting in the near-IR, carbon suspension materials are widely regarded as unsatisfactory, especially in view of the requirement that they be used in a liquid state.

Optical limiters are materials that are transparent to low-intensity, ambient light but become opaque to high-intensity light. Such materials are of particular interest to the Navy for protecting optical sensors and human eyes from battlefield lasers. The most successful optical limiters known are soluble phthalocyanines, in particular those metallated with lead and indium. Yet further improvements are needed. This research project used a two-pronged approach to create improved optical limiters. The first approach was to synthesize and study soluble thallium phthalocyanines. Thallium, due to its proximity to lead and indium on the periodic table, should exhibit favorable optical limiting properties. Yet soluble thallium phthalocyanines had never been synthesized. A substituted thallium(III) phthalocyanine complex which is readily soluble in organic solvents has been prepared. The second approach to improved optical limiters was to prepare covalently-linked phthalocyanine complexes which allow control of aggregation, an important parameter affecting optical limiting properties. Towards this end, a.

In the search for materials suitable for optical limiting applications to protect eyes & electro-optical sensors against laser radiation, fine carbon particles suspended in a liquid have been shown to possess highly desirable properties. This publication reports on the measurement of the threshold energy fluence (energy per unit area) for optical limiting of nanosecond & microsecond pulses in a high-performance carbon suspension named DREV CBS-100. The technique was tested by measuring materials whose properties can be found in the technical literature.

The latest edition of the leading resource on the properties and applications of liquid crystals In the newly revised Third Edition of Liquid Crystals, Professor Iam Choon Khoo delivers a comprehensive treatment of the fundamentals and applied aspects of optical physics, light scattering, electro-optics, and non-linear optics of liquid crystals. The book's opening chapters include coverage of the foundational physics and optical properties of liquid crystals and lead to more advanced content on the display, photonics and nonlinear optics applications of liquid crystals. New topics, including photonic crystals, metamaterials, ultrafast nonlinear optics, and fabrication methods for massive cholesteric and blue phase liquid crystals are discussed at length. Analytical methods and experimental observations of nonlinear light propagation through liquid crystalline and anisotropic materials and devices are also discussed. Liquid Crystals offers an insightful and unique treatment of the nonlinear optics of liquid crystals. New and expanded sections round out this new edition and add to the most up-to-date resource on this topic available today. The book also includes: A thorough introduction to liquid crystals, including their molecular structures, chemical compositions, order parameter, phase transition, and free energies Practical discussions of nematic, cholesteric, smectic, and ferroelectric liquid crystals, and explorations of linear and nonlinear light scattering in these phases. A detailed quantum mechanical treatment of the linear and nonlinear electronic optical response of liquid crystal molecules to optical fields. A self-contained discussion of the fundamentals of nonlinear optics/photonics and comprehensive review of all liquid crystalline materials-based nonlinear optical processes and applications. The latest edition of Liquid Crystals is an indispensable resource for graduate students, professors, research scientists and engineers in industrial or government laboratories. It's also an ideal reference for anyone seeking a one-stop textbook with complete coverage of the optical, electro-optical, and non-linear optical properties and processes of liquid crystals.

A system to provide eye or sensor protection from laser-beam damage is investigated. Light beams exceeding a safe energy density are prevented from reaching the observer or sensor by the destruction of a mirror in the line-of-sight. The replaceable mirror consists of a 10- to 20-nm vacuum-deposited metal film on a 2- to 8-micrometer black plastic substrate. The mirror is vaporized directly by focusing the input beam on it. The vaporization, which occurs fast enough to protect against Q-switched lasers, prevents the potentially damaging radiation from reaching the eye or sensor. The energy reflected by various prototype limiting mirrors is measured as a function of the incident energy in an experimental arrangement employing 1-J Q-switched and normal-pulsed ruby, and 2-W CW argon laser beams.

Reversible saturable absorption of C60 and sacrificial mirrors with double path were examined for eye protection from laser beams of picosecond and nanosecond lasers. Both approaches can achieve significant attenuation to protect eyes from serious or permanent damage although the clamped energy is still higher than the permissible values of ANSI standards. The combination of these two approaches can eliminate the need to replace sacrificial mirrors. The phenomena of absorbing 100 photons in a single picosecond pulse definitely deserves further study for its mechanism.