We report on a volume holographic imaging spectrometer (VHIS) system which allows retrieval of a scene's two-dimensional spatial information as well as its spectral information. This is performed using a transmission volume hologram and a simple rotary scanning mechanism. The system has the advantages of high spectral and spatial resolutions and the potential of single-shot, four-dimensional (3D spatial plus 1D spectral) imaging by recording multiple volume holograms in the same material. Also, due to the transmission diffraction geometry, the system automatically eliminates the stray excitation light from the captured signal. We give theoretical analysis of the performance and experimental demonstration using fluorescent CdSe/ZeS quantum dots. The measured quantum dots spectra agree well with the spectra obtained using a conventional spectrometer.
We present an overview of imaging systems that incorporate a volume hologram as one of the optical field processing elements in the system. We refer to these systems as volume holographic imaging (VHI) systems. The volume hologram is recorded just once, and the recording parameters depend on the functional requirements of the imaging system. The recording step offers great flexibility in designing application-specific imaging systems. We discuss how a VHI system can be configured for diverse imaging applications ranging from surface profilometry to real-time hyperspectral microscopy, and summarize recent developments in this field.
We propose and demonstrate a widely tunable optical filter, realized by angle tuning a volume holographic grating. The volume holographic grating selectively drops a narrow portion of the signal bandwidth into a fiber while passing through the rest of the signals. The demonstrated 1510- to 1590-nm tuning range covers the entire erbium-doped fiber amplifier (EDFA) C band, with small bandwidth variation and low insertion loss (<1 dB). Group delay, polarization-dependent loss, and polarization mode dispersion are measured and investigated for optimizing the filter characteristics.
We demonstrate 10 plane wave holograms angularly multiplexed at one frequency channel in spectral hole burning medium. We show that the M/# is still a valid system metric and the measured M/# in one frequency channel is about 0.01.
The high data transfer rate achievable in page-oriented optical memories demands for parallel interfaces to logic circuits able to process efficiently the data. The Optically Programmable Gate Array, an enhanced version of a conventional FPGA, utilizes a holographic memory accessed by an array of VCSELs to program its logic. Combining spatial and shift multiplexing to store the configuration pages in the memory, the OPGA module is very compact and has extremely short configuration time allowing for dynamic reconfiguration. The reconfiguration capability of the OPGA can be applied to solve more efficiently problems in pattern recognition and digit classification.
With a photorefractive crystal sitting on top of silicon, a read/write compact holographic memory module is a potential competitive data storage technique. The main advantages of a holographic memory are to store more data with smaller silicon area and lower cost than the traditional silicon Dynamic Random Access Memory (DRAM), and to readout data with faster access time than the magnetic storage.
Compact holographic memory architecture with phase conjugate readout and diffraction suppression by internal reflection is investigated. The pixel size requirement for a competitive system is determined. The bandwidth of the holographic recording in LiNbO<SUB>3</SUB> is broad enough to support the pixel size requirement by theoretical calculation and experimental measurement. Holograms of 1 micrometers <SUP>2</SUP> pixel size binary data are recorded and reconstructed with this system. The pixel size limit, signal noise ratio and the storage density for holographic recording in photorefractive crystals are discussed.
This paper compares the read/write holographic memory with silicon storage on issues of cost, density, size and speed. With a photorefractive crystal on top of a silicon interface, the holographic memory is of cost efficiency, volume compactness and fast data accessing. Key challenges to implement the competitive holographic memory are discussed.
We will descrihe the role of holographic memorv in a current research effort 1 that seeks to combine ariuus advanced technologies to achieve petaflops scale computing within the next decade In addition to holographic memory. the petatlop architecture combines superconductor Rapid Single Flu-.: Quantum (RSFQ) logic. which can operate at I 00 GHz within a cryogenic cm ironmem with power consumption less than 'iO watts. a packet-switching optical network with a multi-le el strncture capable of providing interconnection among tens or thousands of pons '' ith latencies of only I 0 to 30 nanoseconds. Processor-In-Memory (PIM) technology. and a multithreaded hierarchical structure (see Figure I) to allow the processors to access a high capacitv memnrv vhile compensating for the latenc)· problem inherent in such a system.