Optical phased array

The OPA can be operated in reflective mode, provided that the bottom transparent electrode is replaced by a reflector. To achieve the same phase change, the required cell gap can be 

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That SPAs can have both electrical I/O as well as optical I/O renders them potentially useful to any application that interfaces between optical and electronic realms. Such applications are more numerous than already discussed in this section. The emerging SPA technology will likely result in new applications emerging for years to come. Some additional applications not previously mentioned are the parallel-processing planes of pipeline architectures (useful for pixel-level image processing) the various levels of optical neural networks the input, filter, and/or output planes of optical correlators and optical phased-array beam steering. 

In addition to displays, liquid crystals have also been used extensively in tunable photonic devices, such as optical phased array for laser beam steering, variable optical attenuator (VOA) for telecommunications, tunable-focus lens for camera zoom lens, LC-infiltrated photonic crystal fibers [1,2], diode laser-pumped dye-doped LC laser, just to mention a few. 

D. P. Resler, D. S. Hobbs, R. C. Sharp, et al.. High-efficiency liquid-crystal optical phased-array beam steering. Opt. Lett. 21, 689 (1996). 

The PR effect was first observed in 1966 as an undesirable effect in an EO crystal, LiNb03 [1], It was soon realized that this effect is reversible and its PR mechanism was then identified [2,3], These PR materials can be applied to high-capacity optical memories, dynamic hologram formations, massive interconnections, high-speed tunable filters, and true-time relay lines for phase array... 

Figure 16.9 Possible sensor configurations for composites SHM. (a) Local detection with piezo sensors [18] (b) local detection with optical fiber sensors [11] (c) sparse array of piezosensors guided-waves tomography for remote detection [19] (d) phased arrays of piezo sensors for remote guided-waves scanning.

Another model-free method for active damage detection is based on directional transducers. For passive sensing. Section 16.9 has already discussed the use of directional strain rosettes (both piezo and optical) to effectively detect an acoustic source without the need for a structural model. For active sensing, directional transmission as well as reception of guided wave can be achieved with phased-array transducers. 

Frigyes, I. Seeds, A. J. (1995). Optical generated true-time delay in phased array antennas. IEEE Trans. Microw. Theory Tech., Vol. 43, pp. 9... 

Juswardy, B., Xiao, F. Alameh, K. (2009). Opto-VLSI-based photonic true-time delay architecture for broadband adaptive nulling in phased array antennas. Optics Express, Vol. 17, No. 6, pp. 4773-4781, Issn 1094-4087. 

Tong, D. T. K. Wu, M. C. (1998). Multiwavelength optically controlled phased-array antennas. leee Transactions on Microwave Theory and Techniques, Vol. 46, No. 1, pp. 108-115, Issn 0018-9480. 

Zmuda, H., Toughlian, E. N., Jones, M. A. Payson, P. M. (2000). Photonic architectures for broadband adaptive nulling with linear and conformal phased array antennas. Fiber and Integrated Optics, Vol. 19, No. 2, pp. 137-154, Issn 0146-8030. 

Dadfamia, S., Shahani, A.M.H., Shakerian, F. et al. (2013). Comhination of sohd phase extraction and dispersive liquid-hquid microextraction for separation/preconcentration of ultra trace amounts of uranium prior to fiber optic-hnear array spectrophotometry determination,/. Hazard. Mater. 263, 670-676. doi 10.1016/j.hazmat.2013.10.028. 

A variety of phased array systems have been fabricated based on polsrmeric electrooptic materials (141,142). One configuration is based on the photonic phase shifter shown in Figure 10. This provides a very linear phase shift as a function of control d-c voltage. Optical signals of controlled phase are thus sent to various radiating antenna elements. The optical signals are converted to radiofrequency signals by diode detectors. 

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