Digilens is developing a new class of optical components based on the combination of Electrically Switchable Bragg Grating ( ESBG) and optical waveguide technology. One or more optical waveguides are formed on a substrate which is used as one wall of a cell filled with an ESBG. The ESBG layer forms part of the waveguide cladding, such that the grating can interact with the evanescent field of the light energy traveling in the waveguide. This device architecture has been used to make Electrical Variable Optical Attenuators with more than 50 db of controllable range, flat attenuation over the optical communications C band, fast (<100 tsecond) switching speed, and encouragingly low polarization dependent loss. Initial results on a variable wavelength-selective filter are also reported.
The application of an unintensified charge-coupled device (CCD) to one-dimensional multispecies Raman flame imaging is demonstrated. Relative signal strength is improved by the higher quantum efficiency of the unintensified CCD versus an intensified CCD generally used for Raman imaging. Experimental comparisons of unintensified and intensified CCD systems show ~40% improvement in the signal-to-noise ratios of major-species Raman signals for laboratory-scale H(2)-air flames. The maximum possible signal improvement is limited by the 40% transmission efficiency of the ferroelectric liquid-crystal light valve used to gate the CCD, although the light valve is demonstrated to be unnecessary for low-luminosity flames.
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