Spatial intensity modulation

Keywords Fiber optic sensors Chemical sensors Biosensors Evanescent field sensor Intrinsic fiber optic sensors Multimode fibers Modal power analysis Modal power distribution Spatial intensity modulation Optical far-held pattern... 

Radhakrishnan J, El-Sherif MA (1996) Analysis on spatial intensity modulation for fiber optic sensor applications. J OptEiber Technol 2 114-126... 

Figure 6.12 Experimental two-color setup featuring an IR beamline, to generate intense shaped IR pump pulses, and a VIS probe beamline, to provide time-delayed probe pulses of a different color. Both beams are focused collinearly into a supersonic beam to interact with isolated K atoms and molecules. Photoelectrons released during the interaction are measured by an energy-calibrated TOE spectrometer. The following abbreviations are used SLM, spatial light modulator DL, delay line ND, continuous neutral density filter L, lens S, stretcher T, telescope DM, dichroic mirror MCP, multichannel plate detector.

In this section we will consider another type of nonuniform liquid crystal structures in nematics. These structures are created by a spatially nonuniform electric field, and have nothing in common with the modulated orientational and electrohydrodynamic patterns discussed above which, in fact, were created as a result of self-organization. A spatially nonuniform electric field exists in an electrooptical cell in many important cases such as, photosensitive liquid crystal cells [152-154], spatial light modulators with matrix addressing [152], liquid crystal defectoscopy of surfaces [155], liquid crystal microlens [156], etc. By analyzing the liquid crystal electrooptical behavior in a nonuniform field we can estimate different characteristics of the layer, in particular, sensitivity (i.e., the intensity of the optical response at a given voltage), spatial resolution, etc. 

To develop a surface relief structure, the UV-curable polymer was spin coated on the substrates at a rate of 4000 rpm for 30 sec. The resultant thickness of the spin coated polymer film was about 3 pm. After a polymer film formed on the glass substrate, spatially modulated UV light was irradiated onto the film through a photomask. The photomask was designed to generate the intensity modulation of the UV light to form a pattern of microlens arrays. The irradiation led to the diffusion of monomers in the polymer composites from the unexposed to exposed regions. The result was the formation of a lens-shaped surface relief structure. 

The spatial period, d, of the intensity modulation is related to An by d = /An, while An is related to the degree of orientational order in the gel and can be used to estimate the order... 

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