The control of luminous radiation has extremely important implications for modern and future technologies as well as in medicine. In this Review, we detail chemical structures and their relevant photophysical features for various groups of materials, including organic dyes such as metalloporphyrins and metallophthalocyanines (and derivatives), other common organic materials, mixed metal complexes and clusters, fullerenes, dendrimeric nanocomposites, polymeric materials (organic and/or inorganic), inorganic semiconductors, and other nanoscopic materials, utilized or potentially useful for the realization of devices able to filter in a smart way an external radiation. The concept of smart is referred to the characteristic of those materials that are capable to filter the radiation in a dynamic way without the need of an ancillary system for the activation of the required transmission change. In particular, this Review gives emphasis to the nonlinear optical properties of photoactive materials for the functi...

Nonlinear Optical Materials for the Smart Filtering of Optical Radiation.

(CdSe)ZnS Core−Shell Quantum Dots: Synthesis and Characterization of a Size Series of Highly Luminescent Nanocrystallites

An eye tracker having a waveguide for propagating illumination light towards an eye and propagating image light reflected from at least one surface of an eye, a light source optically coupled to the waveguide, and a detector optically coupled to the waveguide. Disposed in the waveguide is at least one grating lamina for deflecting the illumination light towards the eye along a first waveguide path and deflecting the image light towards the detector along a second waveguide path.

Apparatus for eye tracking

An Electrically Switchable Bragg Grating (ESBG) despeckler device comprising at least one ESBG element recorded in a hPDLC sandwiched between transparent substrates to which transparent conductive coatings have been applied. At least one of said coatings is patterned to provide a two-dimensional array of independently switchable ESBG pixels. Each ESBG pixel has a first unique speckle state under said first applied voltage and a second unique speckle state under said second applied voltage.

Laser illumination device

There is provided a transparent wearable data display comprising: a source of collimated light; a means for deflecting said collimated light into a scanned beam; a first array comprising one column and integer N TOWS of switchable grating elements sandwiched between first and second parallel transparent substrates, the substrates together functioning as a first light guide; an second array comprising M columns and N rows of switchable grating elements sandwiched between third and fourth, parallel transparent substrates the substrates together functioning as a second light guide; transparent electrodes applied to opposing faces of the first and second and the third and fourth substrates. Hie apparatus further comprises a first coupling means tor directing the scanned beam into a first TIR light path between the outer surfaces of the first lightguide along the first array column; and a second coupling means for directing the first HR light into a second TIR path between the outer surfaces of the second lightguide along a row of elements of the second array.

Wearable data display

We have performed a detailed comparison of the predictions of coupled-wave theories of isotropic and anisotropic volume gratings. It is shown that material birefringence can dramatically modify the diffractive properties of volume gratings. The predictions of the coupled-wave theories have also been compared with the diffractive properties of volume gratings fabricated with polymer-dispersed liquid crystals. It is shown that a coupled-wave theory that includes the effects of the birefringence of the liquid crystal must be used to explain the diffraction properties of these highly anisotropic gratings. Information can be obtained about the alignment of the liquid crystal within the composite gratings from comparisons of theory and experiment.

Diffractive properties of highly birefringent volume gratings: investigation

We have fabricated electrically switchable holographic gratings, using Polaroid Corporation’s DMP-128 photopolymer filled with the nematic liquid crystal E7. It is shown that a coupled-wave theory that includes the effects of the birefringence of the liquid crystal must be used to explain the diffraction properties of these anisotropic volume gratings. Furthermore, a detailed comparison of theory and experiment provides information about the alignment of the liquid crystal within the polymer host.

Diffraction properties of highly birefringent liquid-crystal composite gratings.

Transmission properties of refractive index-shifted Bragg gratings

An experimental investigation of the transmission of multimode capillary waveguides with a nonlinear absorber in the core shows an enhanced nonlinear absorption relative to the same length of bulk material. The results are consistent with partial mode filling within the cores of the waveguides. This study confirms the promising optical limiting capabilities of multimode nonlinear waveguides and implies that the mode structure should be considered in the design and evaluation of capillary array optical limiters.

Optical limiting properties of nonlinear multimode waveguides

An experimental investigation of the transmission of multimode capillary waveguide arrays containing a liquid nonlinear absorber shows an enhanced nonlinear response relative to that found in a single waveguide and to the same length of bulk material. Comparison of the nonlinear response of arrays with different pitch to diameter (d/Lambda) ratios confirm that both the intensity distribution within an individual waveguide and coupling between the elements of the array influence the overall nonlinear response.

James J. Butler

Papers

Diffractive properties of highly birefringent volume gratings: investigation

Diffraction properties of highly birefringent liquid-crystal composite gratings.

Transmission properties of refractive index-shifted Bragg gratings

Optical limiting properties of nonlinear multimode waveguides

Optical limiting properties of nonlinear multimode waveguide arrays.