**6. References**

354 Holograms – Recording Materials and Applications

The nanophotonic code embedded in the hologram exhibited much greater polarization dependency, as indicated by *embedded* in Fig. 12(b), where the maximum *R*exp was obtained at 80-degree input polarization. On the other hand, only slight polarization dependency was observed with the isolated nanophotonic code, as indicated by *isolated*. These characteristics of retrieving the nanophotonic code in the environmental grid structure agree well with the

In this chapter, we described the basic concept of a nanophotonic hierarchical hologram and a nanophotonic code embedded in a hologram as an implementation of a hierarchical hologram. One of the most notable characteristics of our proposed approach is embedding a nanophotonic code within the patterns of a hologram composed of one-dimensional grid structures; it yields clear polarization dependence compared with an isolated nanophotonic code that is not embedded within a grid structure. These features were successfully

In future research, the relation between the retrieved optical intensity distributions and the design of the nanometric structures may come to be understood, including their environmental conditions. Such insights should allow us to propose, for instance, an optimized strategy for implementing nanophotonic codes, or a strategy that is robust against errors that possibly occur in the fabrication and/or retrieval processes (Naruse et al.,

From the point of view of practical use of these concepts in novel security devices, because embedding and retrieval of a nanophotonic code require highly advanced technical knowhow, this approach can also improve the strength of anti-counterfeiting measures. The number of layers can be increased in the near-mode observation to further extend the hierarchical function. The optical near-field interaction between multiple nanometric structures produces a characteristic spatial distribution depending on the size, alignment, etc. Therefore, various optical signal patterns can be observed depending on the size of the fiber probe, and another layer can be added in near-mode observation (Naruse et al., 2007; Naruse et al., 2005). A simpler method for achieving such a hierarchical function is required, without using optical fiber probe tips. The scale for such retrieval might be set at the submillimeter range, as represented by *optical far-field* in Fig. 3. These aspects are currently

Finally, the concept of hierarchy based on nanophotonics may produce innovations not only in optical security but also for other optical applications, such as lenses and jewellery. Adding extra functions in this way creates value-added media with only a slight impact on the primary functions. However, a trade-off occurs between the nanometric fabrication conditions (e.g., size and pitch) and the impact on the primary functions. Adequate discussion is needed to investigate these trade-offs in each

This work was supported in part by a comprehensive program for personnel training and industry–academia collaboration based on projects funded by the New Energy and Industrial Technology Development Organization (NEDO), Japan, the Global Center of

numerical results in Fig. 9.

demonstrated both numerically and experimentally.

being investigated by the authors.

application for their practical use.

**5. Acknowledgments** 

**4. Summary** 

2009).


**Part 5** 

**Signal Processing** 


**Part 5** 

**Signal Processing** 

356 Holograms – Recording Materials and Applications

Tate, N., Nomura, W., Yatsui, T., Naruse, M., & Ohtsu, M. (2009). Hierarchy in optical near-

Naruse, M., Inoue, T., & Hori, H. (2007). Analysis and Synthesis of Hierarchy in Optical

Naruse, M., Hori, H., Kobayashi, K., Ishikawa, M., Leibnitz, K., Murata, M., Tate, N., &

*Journal of Applied Physics*, Vol. 46, pp. 6095-6103, 2007

2009

26, pp. 1772-1779, 2009

fields based on compositions of nanomaterials, *Applied Physics B*, Vol. 96, pp. 1-4,

Near-Field Interactions at the Nanoscale Based on Angular Spectrum, *Japanese* 

Ohtsu, M. (2009). Information theoretical analysis of hierarchical nano-optical systems in the subwavelength regime, *Journal of the Optical Society of America B*, Vol.

**16** 

*1Australia 2,3Korea* 

**Photonic Microwave Signal Processing Based** 

The processing of radio frequency (RF) and microwave signals in the optical domain is an attractive approach to overcome the bottlenecks of bandwidth, power loss, and electromagnetic interference (EMI) encountered in conventional electronic signal processing systems. A wide range of emerging RF signal processing applications require specifically high resolution, ultra-wide bandwidth, wide-range tunability, and fast reconfigurability. While these requirements are difficult to achieve using conventional all-electronic

Holography is an historic technology that allows the light scattered from an object to be recorded and reconstructed so that the object can reappear when a reference optical beam illuminates a hologram used to record that object. Holography has a wide range of applications such as optical signal storage and retrieval and information processing. The application of reconfigurable phase holograms to realize optical beam steering is an attractive field for either optical engineering or fundamental research. The reconfigurable phase holograms are calculated from the targeted beam steering pattern and implemented using spatial light modulator. Opto-VLSI processors are one of these devices that can

Although full-electronic RF signal processing is very flexible and controllable, it is experiencing the bottlenecks of bandwidth and EMI. Processing microwave signals in the photonic domain can overcome the bottlenecks in the electronic signal processing. However the current technologies of microwave photonics have limited flexibility and reconfigurability. The Opto-VLSI technology is a novel and potential discipline that combine benefits of photonic devices and the intelligence plus processing capabilities of Very-Large-Scale Integrated (VLSI) circuits. It integrates intelligence into photonic systems providing a new foundation for a future information processing and communication systems and networks. This book chapter will discuss a new methodology of expanding the use of Opto-VLSI from the conventional paradigm of optical beam processing to a new frontier of

processing, they are feasible with photonics-based signal processing.

dynamically generate phase holograms and perform optical beam steering.

**1. Introduction** 

**on Opto-VLSI Technology** 

*2Department of Nanobio Materials and Electronics, Gwangju Institute of Science and Technology, 3Department of Information and Communications, Gwangju Institute of Science and Technology,* 

Feng Xiao1, Kamal Alameh1,2 and Yong Tak Lee2,3 *1Electron Science Research Institute, Edith Cowan University,* 
