Manipulation of Photons by Photonic Crystals
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Photons by Photonic Crystals Susumu Noda
The following article is based on the plenary presentation given by Susumu Noda of Kyoto University, Japan, on July 29, 2008, at the 2008 International Union of Materials Research Societies—International Conference on Electronic Materials Meeting in Australia.
Abstract Photonic crystals, in which the refractive index changes periodically, provide an exciting new tool for the manipulation of photons and have received keen interest from a variety of fields. This article reviews recent progress in the manipulation of photons by photonic crystals. First, the article covers spontaneous emission, a fundamental phenomenon associated with all photonic devices that emit light, which now can be successfully controlled. Light emission is suppressed in areas where the photonic crystal is complete, while strong emission occurs in the areas where there are artificial defects. Next, it is shown that a very strong confinement of photons in a small volume on the scale of cubic wavelengths becomes possible by using photonic crystals, where nanocavities with ultrahigh-Q values of more than 2 million have been successfully demonstrated. Finally, photonic crystals promise to realize unprecedented types of lasers, which can produce tailored beams on demand, while keeping stable single longitudinal and lateral modes.
Introduction Photonic crystals are optical nanostructures based on a periodic refractive index distribution. One can expect to explore various unique optical phenomena and develop novel devices that cannot be realized in ordinary materials. For example, spontaneous emission is expected to be inhibited at the photonic bandgap (PBG), while strong emission occurs in areas where defects or disorder have been introduced inside the crystal.1,2 This leads to the development of nanolasers3 and ultrahigh efficient light-emitting diodes (LEDs).4 The photonic crystals also enable strong confinement of photons in ultrasmall-sized spaces of cubic wavelengths (or nanocavities),5 which are important for stopping or slowing light,6,7 photonic nanochips, and quantum information processing devices.2,8 Photonic crystals also can control photons in a large area of more than a few hundred micrometers square, which enables new types of semiconductor lasers that can oscillate in a perfect single mode in a broad area9 and produce various unique beam patterns.10
In the following, such manipulation of photons by photonic crystals are explained.
Spontaneous Emission Control by 3D and 2D Photonic Crystals Spontaneous emission is a fundamental phenomenon associated with all photonic devices that emit light. Unfortunately, it can often be troublesome, limiting the performance of photonic devices in applications, such as illumination, displays, optical communication, solar cells, and quantum-information systems. For example, LEDs, which are poised to replace fluorescent and incandescent lighting, rely on spontaneous emission to generate light, but a large amount of the spontaneous emission is confined inside t
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