Grating structures with symmetric fractionally organized gaps

Abstract

It is well known that grating structures with subgratings separated by small identical gaps (for example, quarter‐wavelength gaps) create a transmission window in the middle of the reflectivity spectrum. In this paper, we analyze structures with mirror symmetry with respect to their centers, but with gaps at both ends that continuously decrease toward their centers. These structures exhibit several dips in the central lobe of the reflectivity spectrum, with spectral properties (linewidths, spectral spacing between dips, etc.) dependent upon the design parameters of the subgratings (length, period, and magnitude of the modulation of the core refractive index). In a special case, the spectral separation between two dips in the main lobe can be controlled by adequately changing these parameters. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 223–229, 2001.

Fractal-Like Square Lattice of Air Holes

“…The modified square lattice of air holes is shown in Figure 1 The propagating mode is assumed to be TE, with the main magnetic field in the y-direction (perpendicular to the plane containing the photonic crystal structure). The epitaxially layered structure consists of a GaAs core region (thickness of 140 nm) surrounded by air on top and an oxidized Al 0.98 Ga 0.02 As region on the bottom [17], as shown in Figure 2. The thickness of the active region is h 1 = 140 nm, while the thickness of the oxidized region (before oxidation) is h 2 = 450 nm.…”

“…They can sometimes represent natura phenomena better than do conventiona geometric objects [15]. These special geometrical forms have a so been applied to optica devices [16][17][18][19], eading to DFB asers with improved performance [18,19]. Also, fractals have been applied to antennas to produce specially tailored radiation beams [20].…”

Analysis of optically pumped compact laterally coupled distributed feedback lasers with three symmetric defect regions

“…[7][8][9] In these structures, the lengths of the subgratings were integer multiples of a reference phase shift. For example, the three phase shifts introduced in the DFB structure may be /3, 2 / 3, and /3 ͑multiples of /3͒ or /4, / 2, and /4 ͑multiples of /4͒.…”