John O. Dimmock

Losses in left-handed materials

Interest in negative refractive index, or left-handed (LH) materials, has escalated rapidly over the last few years and it now appears that useful LH materials may be realizable in the microwave region. However there is also considerable interest in LH materials for infrared and visible applications. The purpose of this paper is to explore the limitations of LH materials at short wavelengths due to inherent losses. Our conclusions are that it may be quite difficult to achieve useful LH materials at wavelengths less than about 10 microns using current approaches.

Slow and fast light in coupled microresonators

We predict the propagation of slow and fast light in two co-resonant coupled optical resonators. In coupled resonators, slow light can propagate without attenuation by a cancellation of absorption as a result of mode splitting and destructive interference, whereas transparent fast light propagation can be achieved by the assistance of gain and splitting of the intracavity resonances, which consequently change the dispersion from normal to anomalous. The effective steady-state response of coupled-resonators is derived using the temporal coupled-mode formalism, and the absorptive and dispersive responses are described. Specifically, the occurrence of slow light via coupled-resonator-induced transparency and gain-assisted fast light are discussed.

Wide angle refractive optics for astrophysics applications

Optical systems consisting of several Fresnel lenses are demonstrated to provide large aperture, wide field imaging for systems with forgiving imaging requirements. Fresnel lenses are shown to be made very thin which makes them ideal for space applications in which system mass and absorption losses are critical. Optics for a proposed space-based air shower detector (Orbiting Wide-angle Light-collector, OWL) are displayed which are the result of a feasibility study.

Nonlinear Self-Organization in Photorefractive Materials

Publisher Summary This chapter discusses self-organization and its effects in optics. One of the most exciting and potentially useful areas of current research in optics involves the understanding and exploitation of self-organization in nonlinear optical systems. This self-organization may sometimes lead to the evolution of complex spatial patterns that can be regarded as the nonlinear eigenmodes of the system. Generation of these patterns is characteristically marked by the presence of intensity thresholds. In a nonlinear system with complicated temporal dynamics, it turns out that one cannot retain purity in spatial dimensionality. It is therefore equally important to investigate the dynamics of the transverse spatial variations, which in fact give rise to very interesting patterns due to self-organization. A vast wealth of patterns can be achieved by using a nonlinear optical element with feedback that has the capability of providing field transformation, for example, by spatial filtering. These types of systems are called optical kaleidoscopes simply because of the different self-organized patterns that they can generate.

Steady state analysis of self-organization of light into a scattering ring due to induced reflection gratings in photorefractive materials

We present a steady state theory and derive the eigenmodes for the nonlinear self-organization of light into a scattering ring in photorefractive materials such as potassium niobate, due to the formation of reflection gratings. The configuration we consider comprises solely of a mismatched sample of potassium niobate in air, with no external feedback mirror. This is the first part of the two-step process involved in the self-organization of light into a hexagonal pattern observed in this and other materials. Complete steady state solutions are derived and amplitude and phase variations of the counterpropagating main beam and its spatial sidebands (responsible for ring formation) with propagation are shown. Our computations show the bifurcation diagrams of the amplitudes and phases as a function of the photorefractive gain parameter. Dependence of the results on the amount of linear scattering is also demonstrated. Connections with available experimental results are made, and improvements on the model used are proposed.

Principles of wide angle, large aperture optical systems

The general principles of designing wide angle, large aperture optical systems are addressed. In particular, the advantages and disadvantages of reflective and refractive optical systems are discussed. It is shown that reflective optics have an inherently smaller field of view than do refractive systems. Conservation of etendue is discussed and directly applied to the determination of focal plane size of all optical systems as well as the central obscuration of systems with reflective primaries.

Effect of the phase of the coupling constant on the self-organization of light in potassium niobate

We investigate self-organization of a laser beam into a scattering ring in photorefractive potassium niobate when the phase of the coupling constant is arbitrary. We find that for a range of values of the phase and amplitude of the coupling gain, the calculated forward and backward scattered ratios are in reasonable agreement with experimental observations. The phase of the coupling constant is determined by an interplay of both diffusive and photovoltaic nonlinearities, as well as phase shifts in the induced grating profile with only photovoltaic nonlinearities but for strong modulation depths of the intensity grating.

OWL—Orbital Wide-angle Light-collector for the air watch program, and multiple OWL

The International Space Station (ISS) will revolutionize scientific experimentation by providing a platform upon which some of the most ambitious projects yet conceived may be constructed, operated, and deployed. The Orbiting Wide-angle Light-collector (OWL-Airwatch) is a proposed space-based extensive air shower observatory which will detect a significant number of cosmic rays with energies above 1020 eV (Takahashi, 1996; Streitmatter, 1998; DeMarzo, 1998). A complete understanding of the origins and propagation of these particles may only be possible by introducing new and exotic physical mechanisms, and OWL-Airwatch may provide the first definitive evidence for the existence and decay of topological defects and other such exotic phenomena. There also exists the possibility of detecting high energy neutrinos as well as observing the effects of quantum gravity with the OWL-Airwatch instrument. Although the first OWL-Airwatch mission is planned as a free-flying observatory, its scientific abilities can be...

Focal plane reduction of large aperture optical systems

The size of the focal plane of an optical system is shown to be reduced through the use of re-imaging optics. The general principles of image segmentation and relay optics are discussed as well as trade-offs that must be performed to develop a practical system. A system of re-imaging optics is designed that reduces the necessary detector area of a proposed air shower detector by almost an order of magnitude.

Self-organization in photorefractive crystals in the presence of transmittsion and refletion gratings

Pattern formation and self phase conjugation are observed simultaneously in photorefractive potassium niobate. The effects have been modelled assuming the presence of reflection gratings. In this paper, we further the theoretical analysis by incorporating the effects of both reflection and transmission gratings. Also, we state image processing applications of self phase conjugation such as edge enhancement and contrast reversal.