Contents I. Introduction
Photonic crystals can in many ways be regarded as man-made materials that exhibit similar properties for light propagation as solids for electrons. Scanning electron microscopy (SEM) graph of the device. (a) Photonic crystal coupled-cavity laser source with waveguides along - orientation. (b) Photonic crystal-based Y-coupler in - orientation. (c) Cross-sectional view of output waveguide, total etch depth is approximately 3 . A periodic modulation of the refractive index on a wavelength scale creates band structures similar to those observed in solids [1], [2]. In particular, the formation of frequency bands that prohibit light propagation can be exploited to overcome the difficulty of light confinement in low index contrast material systems. Efforts have been made to fabricate passive structures such as optical waveguides with ultrasmall bends [3], filters [4], and active devices such as optically pumped defect cavity lasers [5]. Progress has been reported on single-wavelength sources [6], [7] as well as on wavelength tunable sources [8] with integrated photonic crystal mirrors. One of the major benefits expected from photonic crystal-based optical components is their high integration density. Classical optoelectronic circuits such as ridge waveguide-based combiner designs [9], [10] have design dimensions of several millimeters.
