In this paper we review our recent works in developing photonic crystals and nanophotonic structures for the control of light. We show that dynamic crystal structures, in which the refractive index of the material is modulated by a small extent while a photon pulse is in the crystal, can be used to stop, store and even time-reverse light pulses [ 1][ 2][ 3]. We also show that by incorporating magneto-optical effects into the crystal structures, the reciprocity of light can be broken, resulting in uni-directional devices that are extremely compact [ 4]. And finally, by exploiting sub-wavelength electromagnetic resonances in meta structures, new meta-materials can be created. These materials feature frequency-independent refractive index that is controlled by geometry and can be arbitrarily large [ 5]. Such materials can be of importance for integrated optics and image sensing applications.
In this paper we review our recent works in developing photonic crystals and nanophotonic structures for the control of light. We show that dynamic crystal structures, in which the refractive index of the material is modulated by a small extent while a photon pulse is in the crystal, can be used to stop, store and even time-reverse light pulses [ 1][ 2][ 3]. We also show that by incorporating magneto-optical effects into the crystal structures, the reciprocity of light can be broken, resulting in uni-directional devices that are extremely compact [ 4]. And finally, by exploiting sub-wavelength electromagnetic resonances in meta structures, new meta-materials can be created. These materials feature frequency-independent refractive index that is controlled by geometry and can be arbitrarily large [ 5]. Such materials can be of importance for integrated optics and image sensing applications.
Recently there has been a considerable interest in metamaterial waveguide structures capable of dramatically slowing down or, even, completely stopping light. Here, we shall explain in some detail the working principle behind the deceleration and/or stopping of light in metamaterial structures, and review the various, metamaterial-enabled, methods that have been proposed thus far towards achieving such a goal. Further, we will concisely describe how one can construct zero-loss metamaterials over a continuous and broad (but not infinite) range of frequencies, which is an essential prerequisite for any slow-light system. Moreover, it will be explained that inside such waveguide structures light can in principle be stopped (zero group velocity, vg = 0) even in the presence of losses. By nature, metamaterialenabled schemes for stopping/storing light invoke solid-state materials and, as such, are not subject to low-temperature or atomic coherence limitations. Furthermore, these methods simultaneously allow for broad bandwidth operation, since they do not rely on group index resonances; large delay-bandwidth products, since a wave packet can, in principle, be completely stopped and buffered indefinitely; and (for the case, in particular, where a negative-index metamaterial is used) high, almost 100%, in/out-coupling efficiencies. Thus, we conclude that these methods for trapping photons, which can be realised using existing technology, could open the way to a multitude of hybrid optoelectronic devices to be used in 'quantum information' processing, communication networks and signal processors and may conceivably herald a new realm of combined metamaterials and slow light research.
The extremely large speed of light is a tremendous asset but also makes it challenging to control, store or shrink beyond its wavelength. Particularly, reducing the speed of light down to zero is of fundamental scientific interest that could usher in a host of important photonic applications, some of which are hitherto fundamentally inaccessible. These include cavity-free, low-threshold nanolasers, novel solar-cell designs for efficient harvesting of light, nanoscale quantum information processing (owing to the enhanced density of states), as well as enhanced biomolecular sensing. We shall here present nanoplasmonic-based schemes where timedependent sources excite “complex-frequency” modes in uniform (plasmonic) heterostructures, enabling complete and dispersion-free stopping of light pulses, resilient to realistic levels of dissipative, radiative and surface-roughness losses. Our theoretical and computational results demonstrate extraordinary large lightdeceleration factors (of the order of 15,000,000) in integrated nanophotonic media, comparable only to those attainable with ultracold atomic vapours or with quantum coherence effects, such as coherent population oscillations, in ruby crystals.
We review recent theoretical and experimental breakthroughs in the realm of slow and stopped light in structured photonic media featuring negative electromagnetic parameters (permittivity/permeability and/or refractive index). We explain how and why these structures can enable complete stopping of light even in the presence of disorder and, simultaneously, dissipative losses. Using full-wave numerical simulations we show that the incorporation of thin layers made of an active medium adjacently to the core layer of a negative-refractive-index waveguide can completely remove dissipative losses – in a slow-light regime where the effective index of the guided wave is negative.
We review recent theoretical and experimental breakthroughs in the realm of slow and stopped light in structured photonic media featuring negative electromagnetic parameters (permittivity/permeability and/or refractive index). We explain how and why these structures can enable complete stopping of light even in the presence of disorder and, simultaneously, dissipative losses. Using full-wave numerical simulations we show that the incorporation of thin layers made of an active medium adjacently to the core layer of a negative-refractive-index waveguide can completely remove dissipative losses - in a slow-light regime where the effective index of the guided wave is negative. We, also, review and compare several 'trapped rainbow' schemes that have recently been proposed for slowing and stopping light.
A global web of optical fibers forms the backbone of the Internet. This network relies on routers that switch the transmitted pulses from one fiber to another, so that information ends up at the desired destination. Currently, data traffic at major interconnections requires routers to first convert the travelling optical pulse into an electrical one, perform a switching operation, and then convert the electrical pulse back to its original form. This process can slow-down systems by a factor of 1000. Until now, the prime difficulty in designing an all-optical network router was finding a means to temporarily store or buffer the packets of information. Researchers have recently proposed a variety of methods for completely stopping light. Unfortunately, inherent limitations prevent their deployment. For instance, previous approaches employed ultra cold or hot gases1 and did not use solid-state materials. Other methods stored the data pulses as acoustical disturbances, which still travelled slowly down the fiber2. We have proposed3 a light-guiding structure that does not require cryogenic temperatures and can efficiently bring an optical pulse to a complete halt. In this approach, light travels inside an engineered solid-state meta-material (MM), that has a negative refractive index. This material was developed4 in 2001 and the scheme is conceptually simple. The device we envisioned is a three-layer waveguiding heterostructure, in which the middle MM layer is surrounded by two regular dielectrics. The center portion tapers from wide to narrow. Because the power-flow direction inside theMM layer is opposite to the one in the dielectric regions, the guided electromagnetic waves are markedly slowed. Figure 1 shows the propagation of a monochromatic ( f = 1THz) p-polarized magnetic-field component. The light enters the device from the wide end and stops at the prearranged critical thickness. Because of theMM’s anomalous frequency dispersion, the longest (red) wavelength components stop at the Figure 1. A white light beam hits the tapered negative refractive index layer (shown in white), which is surrounded by two regular dielectric layers (shown in blue and green). Upon entering the structure, each frequency component, or color, of the beam stops at different thicknesses, forming a trapped rainbow.