Abstract: A band-gap spectral filter is made of a nanochannel glass structure having a two-dimensional array of parallel dielectric rods arranged in a matrix material. The materials for the dielectric rods and the matrix material are selected so that the difference between the refractive index of the dielectric rods and the refractive index of the matrix material is equal to or less than about 0.5.

Abstract: A passive optical limiter for protecting a light-sensitive object from damage due to an incident light beam above a first predetermined value of light intensity is disclosed.

Abstract: A broadband thermal optical limiter disposed between a laser oscillator and laser amplifier system for protecting optical components in the laser oscillator from damage due to amplified optical feedback from the laser amplifier system at all near ultraviolet, visible and near infrared wavelengths is disclosed.

Abstract: A broadband thermal optical limiter for protecting a light-sensitive object from intense laser beams at all near ultraviolet, visible and near infrared wavelengths is disclosed. The broadband thermal optical limiter comprises: a sample cell containing a solution of broadband absorber material dissolved in a thermal solvent; and a first optical device for converging an incident laser beam into the sample cell. The sample cell is responsive to a converged incident laser beam below a predetermined intensity level for passing therethrough the converged incident laser beam below the predetermined intensity level. The sample cell is also responsive to a converged incident laser beam at or above a predetermined intensity level for thermally defocusing substantially all of the converged incident laser beam in different directions and passing therethrough only a remaining small portion of the converged incident laser beam at or above the predetermined intensity level.

Abstract: A method and apparatus for determining the absorption spectra, and other properties, of aerosol particles. A heating beam source provides a beam of electromagnetic energy which is scanned through the region of the spectrum which is of interest. Particles exposed to the heating beam which have absorption bands within the band width of the heating beam absorb energy from the beam. The particles are also illuminated by light of a wave length such that the light is scattered by the particles. The absorption spectra of the particles can thus be determined from an analysis of the scattered light since the absorption of energy by the particles will affect the way the light is scattered. Preferably the heating beam is modulated to simplify the analysis of the scattered light. In one embodiment the heating beam is intensity modulated so that the scattered light will also be intensity modulated when the particles absorb energy.

Abstract: A picosecond traveling-wave parametric device capable of controlled spectral bandwidth and wavelength in the infrared is reported. Intense 1.064 .mu.m picosecond pulses (1) pass through a 4.5 cm long LiNbO.sub.3 optical parametric oscillator crystal (2) set at its degeneracy angle. A broad band emerges, and a simple grating (3) and mirror (4) arrangement is used to inject a selected narrow-band into a 2 cm long LiNbO.sub.3 optical parametric amplifier crystal (5) along a second pump line. Typical input energies at 1.064 .mu.m along both pump lines are 6-8 mJ for the oscillator and 10 mJ for the amplifier. This yields 1 mJ of tunable output in the range 1.98 to 2.38 .mu.m which when down-converted in a 1 cm long CdSe crystal mixer (6) gives 2 .mu.J of tunable radiation over the 14.8 to 18.5 .mu.m region. The bandwidth and wavelength of both the 2 and 16 .mu.m radiation output are controlled solely by the diffraction grating.

Abstract: A method of initiating a rapid pH change in a solution by irradiating the solution with an intense flux of electromagnetic radiation of a frequency which produces a substantial pK change to a compound in solution. To optimize the resulting pH change, the compound being irradiated in solution should have an excited state lifetime substantially longer than the time required to establish an excited state acid-base equilibrium in the solution. Desired pH changes can be accomplished in nanoseconds or less by means of picosecond pulses of laser radiation.

Abstract: Self-focusing damage caused by diffraction in laser amplifier systems may be minimized by appropriately tailoring the input optical beam profile by passing the beam through an aperture having a uniform high optical transmission within a particular radius r.sub.o and a transmission which drops gradually to a low value at greater radii. Apertures having the desired transmission characteristics may readily be manufactured by exposing high resolution photographic films and plates to a diffuse, disk-shaped light source and mask arrangement.

Abstract: A system for protecting ships from attack by an infrared-seeking missile is provided which comprises decoying the missile by deploying an aerosol. In one embodiment, the aerosol merely scatters a modulated light beam. Another embodiment deploys particles that can undergo an exothermic photochemical reaction when initiated by an ultraviolet laser. The laser projects an image of the ship onto the aerosol and at the same time causes the particles to generate sufficient heat to attract the infrared-seeking missile away from the ship. This system presents an infrared-decoy target with a suitable infrared image of appropriate spatial scale to mislead a missile with imaging capability. The spectral content of the decoy's image resembles that of a blackbody 20.degree.-50 .degree. C. above ambient, and has a brightness and spatial extent equal to the largest ships, approximately 10 kw/steradian, in the 3-5 and 8-12 micrometer bands.