There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

1. Introduction 2. Theoretical foundations 3. Propagation and focusing of optical fields 4. Spatial resolution and position accuracy 5. Nanoscale optical microscopy 6. Near-field optical probes 7. Probe-sample distance control 8. Light emission and optical interaction in nanoscale environments 9. Quantum emitters 10. Dipole emission near planar interfaces 11. Photonic crystals and resonators 12. Surface plasmons 13. Forces in confined fields 14. Fluctuation-induced phenomena 15. Theoretical methods in nano-optics Appendices Index.

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Principles of nano-optics

Topological photonics is a rapidly emerging field of research in which geometrical and topological ideas are exploited to design and control the behavior of light. Drawing inspiration from the discovery of the quantum Hall effects and topological insulators in condensed matter, recent advances have shown how to engineer analogous effects also for photons, leading to remarkable phenomena such as the robust unidirectional propagation of light, which hold great promise for applications. Thanks to the flexibility and diversity of photonics systems, this field is also opening up new opportunities to realize exotic topological models and to probe and exploit topological effects in new ways. This article reviews experimental and theoretical developments in topological photonics across a wide range of experimental platforms, including photonic crystals, waveguides, metamaterials, cavities, optomechanics, silicon photonics, and circuit QED. A discussion of how changing the dimensionality and symmetries of photonics systems has allowed for the realization of different topological phases is offered, and progress in understanding the interplay of topology with non-Hermitian effects, such as dissipation, is reviewed. As an exciting perspective, topological photonics can be combined with optical nonlinearities, leading toward new collective phenomena and novel strongly correlated states of light, such as an analog of the fractional quantum Hall effect.

Topological Photonics

Microcavity physics and design will be reviewed. Following an overview of applications in quantum optics, communications and biosensing, recent advances in ultra-high-Q research will be presented.

Optical microcavities

The term photonic crystals appears because of the analogy between electron waves in crystals and the light waves in artificial periodic dielectric structures. During the recent years the investigation of one-, two-and three-dimensional periodic structures has attracted a widespread attention of the world optics community because of great potentiality of such structures in advanced applied optical fields. The interest in periodic structures has been stimulated by the fast development of semiconductor technology that now allows the fabrication of artificial structures, whose period is comparable with the wavelength of light in the visible and infrared ranges.

http://ieeexplore.ieee.org/iel5/6354/16969/00781867.pdf

Photonic crystals

We have designed and fabricated an optical microcavity formed from a defect in a two-dimensionally patterned, half wavelength thick, InGaAs/InGaAsP multi-quantum well membrane.

Photonic bandgap membrane microresonator

A linear cavity design to produce a traveling wave operation as in a ring laser without the ring cavity design. All fiber configurations may be used to implement fiber lasers based on the linear cavity design.

Traveling-wave linear cavity laser

We form a microcavity laser using two-dimensional photonic crystals embedded in a half wavelength thick waveguide. Modes localized to a single defect in the photonic crystal can be theoretically shown to have mode volumes as small 2(/spl lambda//2n)/sup 3/ and near unity spontaneous emission coupling factors. The flexibility in design of the photonic crystal enables one to tailor the device for vertical emission or for coupling into an in-plane waveguide. These type of devices may be useful for high density, low threshold optical sources in compact optical systems. The added versatility in being able to etch the laser cavity may also help develop low threshold laser sources in material systems in which high index contrast epitaxial mirrors do not exist. The defect laser cavities were formed in the InGaAsP material system in order to reduce the non-radiative surface recombination rate. The active region consists of four quantum wells (QW) designed for 1.55 /spl mu/m peak emission at room temperature.

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Photonic bandgap defect laser

Photonic bandgap crystals are expected to be
of use in defining microcavities for modifying
spontaneous emission and as highly reflective
mirrors. There are several reports of microfabricating
one-dimensional structure. Here, we describe the incorporation of a microfabricated two-dimensional photonic lattice in an edge-emitting semiconductor laser structure.
We demonstrate laser operation in a cavity formed between a cleaved facet and a microfabricated periodic lattice.

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Lasers incorporating two-dimensional photonic crystal mirrors

We have demonstrated optically pumped two-dimensional photonic crystal defect InGaAsP MQW lasers at 1.5 /spl mu/m. Pulsed lasing action at 143 K has been obtained in microcavities as small as 2(/spl lambda//2n)/sup 3/.

/pdf/two-dimensional-photonic-bandgap-defect-laser-2nzg0ydqyz.pdf

Reginald K. Lee

Papers

Photonic bandgap membrane microresonator

Traveling-wave linear cavity laser

Photonic bandgap defect laser

Lasers incorporating two-dimensional photonic crystal mirrors

Two-dimensional photonic bandgap defect laser