Long-term large-scale holographic storage in LiNbO33:Fe

[摘要] The organization of this thesis very much coincides with the progress and "evolution" of my work here at Caltech. I came in at a time when our research activities entered a phase of full-scale realization of holographic storage after theoretical model building and proof-of-principle investigations were successfully carried out. More and more efforts have been dedicated to various experimental examination and demonstrations. Therefore, the major portion of this thesis details results from these efforts. Theoretical treatments are developed when necessary and only serve as the starting point and justification of further, serious experimentation.The centerpiece of my work described in this thesis is a large-scale fast random-access holographic memory using LiNbO[subscript 3]Fe. It is not only our first attempt to incorporate many important disciplines and understandings of holographic memory design, engineering and experimentation to construct a real working prototype, but also a tool and test-bed for later characterization and investigation of other aspects in the application of holographic storage technology. This system is described in detail in Chapter 2 and 3 and has been used repeatedly and extensively through all of our works. Another two threads in the work presented here are the use of the M/# as a system metric to evaluate the dynamic range limitations, and of the Signal-to-Noise Ratio (SNR) and Bit-Error Rate (BER) to characterize the system error performance.In Chapter 2, the design of a large-scale random-access holographic memory using LiNbO[subscript 3]Fe is discussed in detail. High, system dynamic-range-limited storage capacity is demonstrated by using angle, fractal and spatial multiplexing with a key custom-designed component—the segmented mirror array. The SNR and BER obtained from the reconstructed information are comparable to those of conventional CD-ROMs.Fast random access to the memory contents is materialized in a separate system using an acousto-optic deflector (AOD) as the addressing device and an electro-optic modulator (EOM) to compensate for the Doppler shift. Chapter 3 discusses the design issues and presents experimental demonstration of holographic storage using the system. The design and application of an optical phase-lock loop using the AOD and EOM for phase stabilization are also described at the end of this chapter.Chapter 4 and 5 address two methods of thermal fixing to solve the volatility problem in holographic memories using photorefractive materials. First, "Low-High-Low" fixing is described in Chapter 4, along with the characterization of system error performance of non-volatile holographic storage using thermal fixing. A novel "incremental fixing schedule" is introduced to improve the system fixing efficiency. Experimental demonstration of a large-scale non-volatile memory with good error performance is also presented.Chapter 5 shows theoretical treatment and experimental demonstration of high-temperature recording in LiNb0[subscript 3]Fe. Different charge transport mechanisms and their influence on the dynamics of holographic recording as well as the system dynamic range are discussed in detail. The two thermal fixing methods are examined and compared in terms of the M/#.In Chapter 6, a very important holographic noise source, the inter-pixel grating noise, is evaluated theoretically based on a linear (small-signal) model, followed by experimental investigation of its influence on the system error performance of a large-scale memory. Random-phase modulation in the signal beam is discussed and demonstrated as an effective way to suppress this holographic noise.

[发布机构] University:California Institute of Technology

[关键词] Electrical engineering