Nonlinear optical materials include inorganic single crystals, doped glasses, liquid crystals compound semiconductors and organic dyes. Here, an unusual type of NLP materials, with a very simple structure, alkalimetal vapors, are discussed. The vapors have been found to be among the best nonlinear optical materials for information processing in terms of several figures of merit. The “materials” and their applications are reviewed.
Nonlinear optical materials include inorganic single crystals, doped glasses, liquid crystals compound semiconductors and organic dyes. Here, an unusual type of NLP materials, with a very simple structure, alkalimetal vapors, are discussed. The vapors have been found to be among the best nonlinear optical materials for information processing in terms of several figures of merit. The “materials” and their applications are reviewed.
Since quantum information technologies are expected to offer communication security and high computational capacities, research in the field is currently attracting a lot of attention. Among the materials studied so far, rare earth doped inorganic insulators are one of the most promising. With the different available trivalent rare earth ions, the visible and the IR range including the telecom wavelength at 1.5 μm can be covered. Transitions are usually narrow, and at low temperatures, long optical and spin coherence times can often be observed. Investigations using bulk single crystals have already led to many promising results. Recently, spectroscopic studies have been extended to other forms of inorganic materials, such as transparent ceramics, thin films, and nanoparticles for single rare‐earth qubits. Progress in these areas is expected to offer many new possibilities for the design of quantum light‐matter interfaces and scalable quantum memories and processors.
Research into slow light began theoretically in 1880 with the paper [1] of H A Lorentz, who is best known for his work on relativity and the speed of light. Experimental work started some 60 years later with the work of S L McCall and E L Hahn [2] who explored non-linear self-induced transparency in ruby. This field of research has burgeoned in the last 10 years, starting with the work of L Vestergaard Hau and coworkers on slow light via electromagnetically induced transparency in a Bose–Einstein condensate [3]. Many groups are now able to slow light down to a few metres per second or even stop the motion of light entirely [4]. Today, slow light – or more often `slow and fast light' – has become its own vibrant field with a strongly increasing number of publications. In broad scope, slow light research can be categorized in terms of the sort of physical mechanism used to slow down the light. One sort of slow light makes use of material dispersion. This dispersion can be the natural dispersion of the ordinary refractive index or can be the frequency dependence of some nonlinear optical process, such as electromagnetically induced transparency, coherent population oscillations, stimulated light scattering, or four-wave mixing processes. The second sort of slow light makes use of the wavelength dependence of artificially structured materials, such as photonic crystals, optical waveguides, and collections of microresonators. Material systems in which slow light has been observed include metal vapours, rare-earth-doped materials, Raman and Brillioun gain media, photonic crystals, microresonators and, more recently, metamaterials. A common feature of all of these schemes is the presence of a sharp single resonance or multiple resonances produced by an atomic transition, a resonance in a photonic structure, or in a nonlinear optical process. Current applications of slow light include a series of attractive topics in optical information processing, such as optical data storage, optical memories, quantum information devices, and optical communication systems in which the use of slow light will allow all-optical processing with less wasted heat. To implement these applications, devices such as buffers, memories, interferometers and switches that utilize slow light need to be developed. Future challenges include the need for improved coupling of light into slow light modes, overcoming propagation losses, and mitigating the influence of large dispersion of the group velocity. The collection of papers in this special issue of Journal of Optics features a broad spectrum of articles that highlight actual developments in many of the material types and schemes described above. It represents therefore an excellent up to date snapshot of the current state of the field of slow light research. References [1] Lorentz H A 1880 Uber die Beziehung zwischen der Fortpflanzung des Lichtes und der Körperdichte Wiedemann Ann. 9 641–64 [2] McCall S L and Hahn E L 1967 Self-induced transparency by pulsed coherent light Phys. Rev. Lett. 18 908–11 [3] Vestergaard Hau L, Harris S E, Dutton Z and Behroozi C H 1999 Nature 397 594 [4] Philips D F, Fleischhauer A, Mair A, Walsworth R L and Lukin M D 2001 Storage of light in atomic vapor Phys. Rev. Lett. 86 783–6
There is an always growing interest in the study and characterization of new nonlinear optical materials with higher nonlinear coefficients and fast responses, especially for their potential applications in the telecommunications, in the optical computing, and in several other fields where the main issues are high bit rates, parallel processing and large mass storage. The semiconductor technology allowed the construction of very complicated structures, the multiple quantum wells (MPWs), with resonant nonlinearities far bigger than those available in semiconductor crystals, and pushing further the quantum confinement to comprise all the three space dimensions (quantum dots, QDs) is the next step toward even better performances.
Unique spectroscopic properties of isolated rare earth ions in solids offer optical linewidths rivaling those of trapped single atoms and enable a variety of recent applications. We design rare-earth-doped crystals, ceramics, and fibers with persistent or transient "spectral hole" recording properties for applications including high-bandwidth optical signal processing where light and our solids replace the high-bandwidth portion of the electronics; quantum cryptography and information science including the goal of storage and recall of single photons; and medical imaging technology for the 700-900 nm therapeutic window. Ease of optically manipulating rare-earth ions in solids enables capturing complex spectral information in 105 to 108 frequency bins. Combining spatial holography and spectral hole burning provides a capability for processing high-bandwidth RF and optical signals with sub-MHz spectral resolution and bandwidths of tens to hundreds of GHz for applications including range-Doppler radar and high bandwidth RF spectral analysis. Simply stated, one can think of these crystals as holographic recording media capable of distinguishing up to 108 different colors. Ultra-narrow spectral holes also serve as a vibration-insensitive sub-kHz frequency reference for laser frequency stabilization to a part in 1013 over tens of milliseconds. The unusual properties and applications of spectral hole burning of rare earth ions in optical materials are reviewed. Experimental results on the promising Tm3+:LiNbO3 material system are presented and discussed for medical imaging applications. Finally, a new application of these materials as dynamic optical filters for laser noise suppression is discussed along with experimental demonstrations and theoretical modeling of the process.
Quantum information processing is a promising way that deals with the aspects of superposition, entanglement, computation using coherence, communication, and sensing. This review is an analysis of how alkali Rydberg atoms can be used in quantum information processing. The leading candidates are the alkali atoms, as they have a simple electronic structure, transitions that are well characterized, and which can be laser-cooled and trapped. Important mechanisms, such as EIT, dipole-dipole interactions, and Rydberg blockade, are necessary to achieve high-fidelity quantum gates, photon-photon interactions, and long-lived quantum memories. Experimental devices such as magneto-optical traps, optical tweezers, optical lattices, and warm vapor cells have made it possible to use a controllable atom-photon interface and scalable architecture. In the recent development of laser and microwave control methods, the time of coherence, state-transfer, and single-atom addressability have been enhanced. Such challenges include decoherence due to spontaneous emission, motional dephasing, and technical issues in trapping stability and laser linewidth. This review concludes that alkali Rydberg atoms, especially rubidium and cesium, are of relevance in scalable fault-tolerant quantum computing and quantum simulation, and represent the meeting of basic quantum science with new technology uses.
A review will be presented on using liquid crystal properties of molecular alignment and self-assembly into photonic bandgap structures in quantum and nano-photonics. Advances in transparent planar optics using modulation of the geometrical (Pancharatnam-Berry) phase will be outlined. The author’s results on single-photon sources with definite polarizations and collaborative research on using liquid crystals for modeling quantum mechanical tunneling phenomena will be overviewed. Future prospects of patterned liquid crystals and topological defects in these materials will be discussed.