Quantum cryptography could well be the first application of quantum mechanics at the individual quanta level. The very fast progress in both theory and experiments over the recent years are reviewed, with emphasis on open questions and technological issues.

Quantum Cryptography

We review the field of femtosecond pulse shaping, in which Fourier synthesis methods are used to generate nearly arbitrarily shaped ultrafast optical wave forms according to user specification. An emphasis is placed on programmable pulse shaping methods based on the use of spatial light modulators. After outlining the fundamental principles of pulse shaping, we then present a detailed discussion of pulse shaping using several different types of spatial light modulators. Finally, new research directions in pulse shaping, and applications of pulse shaping to optical communications, biomedical optical imaging, high power laser amplifiers, quantum control, and laser-electron beam interactions are reviewed.

Femtosecond pulse shaping using spatial light modulators

We describe devices in which optics and fluidics are used synergistically to synthesize novel functionalities. Fluidic replacement or modification leads to reconfigurable optical systems, whereas the implementation of optics through the microfluidic toolkit gives highly compact and integrated devices. We categorize optofluidics according to three broad categories of interactions: fluid–solid interfaces, purely fluidic interfaces and colloidal suspensions. We describe examples of optofluidic devices in each category.

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Developing optofluidic technology through the fusion of microfluidics and optics

Multiphoton interference reveals strictly nonclassical phenomena. Its applications range from fundamental tests of quantum mechanics to photonic quantum information processing, where a significant fraction of key experiments achieved so far comes from multiphoton state manipulation. The progress, both theoretical and experimental, of this rapidly advancing research is reviewed. The emphasis is given to the creation of photonic entanglement of various forms, tests of the completeness of quantum mechanics (in particular, violations of local realism), quantum information protocols for quantum communication (e.g., quantum teleportation, entanglement purification, and quantum repeater), and quantum computation with linear optics. The scope of the review is limited to ``few-photon'' phenomena involving measurements of discrete observables.

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Multiphoton entanglement and interferometry

Self-organized dendritic crystal growth is explored to assemble uniform semiconductor nanowires into highly ordered one-dimensional microscale arrays that resemble comb structures. The individual ZnO nanowires have uniform diameters ranging from 10 to 300 nm. They are evenly spaced on a stem with a regular periodicity of 0.1-2 micrometer. Under optical excitation, each individual ZnO nanowire serves as a Fabry-Perot optical cavity, and together they form a highly ordered nanowire ultraviolet laser array.

/pdf/dendritic-nanowire-ultraviolet-laser-array-3t8o9xiu08.pdf

Dendritic nanowire ultraviolet laser array.

We present a new modeling tool to analyze near-field phenomena in periodic nanostructures, and apply it to investigate nanophotonic devices, including 2-D photonic crystals with defects and a transverse near-field localization structure for nonlinearity enhancement.

Nanophotonic devices based on near-field phenomena in periodic nanostructures

Optical information processing, traditionally employed in the spatial domain, has been experiencing a renaissance with femtosecond laser pulse technology. Temporal optical information can now be manipulated via linear and nonlinear processes, and stored and retrieved, by converting optical signals between the spatial and temporal domains. In this manuscript, we review the state-of-the-art in the spatio-temporal optical signal processing techniques for information data coding, data conversion, signal recording, as well as signal characterization. Applications of these techniques for future computing, communication, storage, and signal processing systems are discussed.

https://www.spiedigitallibrary.org/conference-proceedings-of-spie/10296/1029604/Nonlinear-space-time-information-processing/10.1117/12.365914.pdf

Nonlinear space-time information processing

We are investigating novel methods for harnessing ultrashort femtosecond pulses to increase the speed, provide privacy and reliability in transmission, distribution and storage of information in optical communication networks applications. To implement these features, real-time all-optical processing techniques for achieving information conversion between slower optoelectronic devices and the ultrafast pulse phenomena need to be constructed. This processing is performed for the first time in the temporal frequency domain by spatially dispersing the frequency components in a spectral processing device (SPD) and performing operations on the spectrally decomposed wave (SDW) using its unique time-domain properties. These techniques enable femtosecond rate space-to-time conversion for multiplexing parallel data streams onto an ultrahigh bandwidth serial temporal channel, and, conversely, time-to-space conversion for demultiplexing an ultrahigh bandwidth serial temporal channel onto slower parallel channels. To fulfill our goal, we utilize nonlinear wave mixing processes based on three- and four-wave mixing in a second order nonlinear crystal inside the SPD.

Nonlinear space-time processing

To fulfill the goal of real-time spectrally decomposed wave (SDW) processing, we utilize nonlinear wave mixing processes based on three- and four-wave mixing in a second order nonlinear crystal inside the spectral processing device (SPD). The latter is achieved via cascaded second-order nonlinearities (CSN). The CSN arrangement consists of a frequency-up conversion process followed by a frequency-down conversion process satisfying the type-II non-collinear phase matching condition.

http://ieeexplore.ieee.org/iel5/7146/19244/00893985.pdf

Ultrafast optics for communications and computing

We have introduced and experimentally demonstrated a nonlinear optical processor that performs pulse imaging of l-D femtosecond optical pulses. The processor operates at femtosecond rates and can be useful for optical network time-to-space demultiplexing applications. The demultiplexer is based on nonlinear three-wave mixing in a LBO crystal.

Pang-Chen Sun

Papers

Nanophotonic devices based on near-field phenomena in periodic nanostructures

Nonlinear space-time information processing

Nonlinear space-time processing

Ultrafast optics for communications and computing

Femtosecond pulse imaging by nonlinear optical three-wave mixing