Applications of volume holographic gratings for signal processing.

摘要

The work presented here represents a series of research projects that are unified in their goal: to use volume holographic gratings to enhance traditional signal processing applications in ways that would otherwise not be possible. To this end, we have completed work that can be classified into four different projects. First, we have developed experimentally a novel holographic medium for volume holographic gratings. Future work on this material will center on achieving greater consistency of results. Second, we have studied the formation of highly selective holographic spectral filters for optical communications using the material that we have developed. Future work will include using optimized material samples and using beam profiling and apodization to achieve the desired filter shape. Third, we have studied the design of a holographic Stokesmeter. We have determined the proper figures of merit for the noise-tolerance of such a Stokesmeter, and have shown how the robustness of this Stokesmeter depends on the properties of its volume holographic gratings. Future work will entail developing a version of the holographic Stokesmeter for laser radar. Finally, we have studied the use of a super-parallel holographic random-access memory (SPHRAM) as the database for a holographic smart eye that can perform high-speed searches using a real-time Vanderlugt correlator. This holographic smart eye has the potential to perform high speed, translation-invariant correlation searches. The SPHRAM was studied theoretically, and the lenslet array, a key component of the SPHRAM, was designed and tested using an industrial optical simulation. With this design in hand, the SPHRAM can now be completed. While developing the full SPHRAM design, we built a real-time Vanderlugt correlator and constructed a prototype holographic smart eye using a disc-based holographic memory system as an alternative to the SPHRAM while the latter is under development. Using the prototype holographic smart eye, a holographic data storage disc was successfully searched for a query image in an automated fashion. Once the holographic smart eye is completed, it can be combined with the polarimetric LADAR system to create a target recognition system that is capable of searching a massive database at high speed for a given query image using visible and polarimetric signature data. Such a device would have a myriad of possible applications, none of which are possible using current technology.