Photonic Crystals: Novel Nano-structures for Light
Susumu Noda
Department of Electronic Science and Engineering,
Kyoto University, Kyoto 606-8501, Japan
Tel: +81-75-753-5297, Fax: +81-75-751-1576, email: snoda@kuee.kyoto-u.ac.jp
Much interest has been drawn in photonic crystals in which the refractive index changes periodically. A photonic bandgap is formed in the crystals, and the propagation of electromagnetic waves is prohibited for all wave vectors. Various important scientific and engineering applications such as control of spontaneous emission, zero-threshold lasing, very sharp bending of light, trapping of photons, and so on, are expected by utilizing the photonic bandgap and the artificially introduced defect states and/or light-emitters. Recently, we have succeeded in developing complete 3D photonic crystals with sufficient bandgap effects at near-infrared wavelengths (1~2mm) based on a method where III-V semiconductor stripes are stacked with the wafer-fusion and the laser-beam assisted very precise (a few tens nano-meter scale precision) alignment [1]. In this presentation, I at first review our approach to create the full 3D photonic bandgap crystals at near-infrared wavelengths and possible applications to ultrasmall optical integrated circuits.
2D photonic crystals are also promising since specific (not almighty, but important) functional devices can be realized even though the control of light is limited two-dimensionally. Thus far, we have investigated novel functional devices utilizing 2D photonic crystals. One example is a 2D photonic crystal laser with multi-directionally distributed feedback effect in 2D photonic lattice structure [2, 3]. It is expected that the device can work as a high-output power surface-emitting laser, which can oscillate in very large area with single mode and desired polarization. The other is a device utilizing a single defect in 2D photonic bandgap structure [4]. The defect traps the photons which propagate through a waveguide formed in 2D photonic crystal slab and emits them to free-space. This phenomenon is very promising for the actual application to an ultra-small optical device with a function of dropping (or adding) photons with various energies from (or into) optical communication traffic (fiber). There are many other important applications by utilizing the strong localization of photons at the defect such as enhancement of nonlinear optical phenomena, and trapping of nano-particles. In this presentation, I also describe the results on the above unique 2D devices and/or phenomena.
[1] S.Noda, K.Tomoda, N.Yamamoto, and A. Chutinan, "Full Three-Dimensional Photonic Bandgap Crystals at Near-infrared Wavelengths", Science, 289, 604-606 (2000).
[2] M.Imada, S.Noda, et al, "Coherent Two-Dimensional Lasing Action in Surface-Emitting Laser with Triangular-Lattice Photonic Crystal Structure", Appl.Phys.Lett., 75, 316-318 (1999).
[3] S.Noda, M.Yokoyama, et al, "Polarization Mode Control of Two-Dimensional Photonic Crystal Laser by Unit Cell Structure Design", Science, 293, 1123-1125 (2001).
[4] S.Noda, A.Chutinan, and M.Imada, "Trapping and Emission of Photons by a Single Defect in a Photonic Bandgap Structure", Nature, 407, 608-610 (2000).