Abstract. We report on the observation of a new type of propagation mechanism through evanescent coupled optical cavity modes in one-dimensional photonic crystals. The crystal is fabricated from alternating silicon-oxide/silicon-nitride pairs with silicon-oxide cavity layers. We achieved nearly full transmission throughout the guiding band of the periodic coupled cavities within the photonic band gap. The tightbinding (TB) parameter κ is determined from experimental results, and the dispersion relation, group velocity and photon lifetime corresponding to the coupled-cavity structures are analyzed within the TB approximation. The measurements are in good agreement with transfer-matrix-method simulations and predictions of the TB photon picture. 42.70.Qs; 71.15.Fv; 42.60.Da; 42.82.Et In recent years, the intense theoretical and experimental investigations of photonic band-gap (PBG) [1,2] phenomena have generated a trend towards the use of these materials in certain potential applications. In particular, enhancement of spontaneous emission near the photonic band edges [3], second-harmonic generation [4], nonlinear optical diodes, switches, limiters [5][6][7], a photonic band-edge laser [8] and transparent metallo-dielectric structures [9,10] were reported for one-dimensional (1D) PBG structures. PACS:By introducing a defect into a photonic crystal, it is possible to create highly localized defect modes within the PBG. Photons with certain wavelengths can be trapped locally inside the defect volume [11], which is analogous to the impurity states in a semiconductor [12]. Recently, we demonstrated guiding and bending of electromagnetic (EM) waves along a periodic arrangement of defects inside a threedimensional photonic crystal at microwave frequencies [13,14]. It was also observed that the group velocity tends towards zero and the photon lifetime increases drastically at the coupled-cavity waveguiding band edges [15]. In the coupledcavity structures, photons hop from one evanescent defect mode to the neighboring one due to overlapping between * Author to whom correspondence should be addressed. (E-mail: bayindir@fen.bilkent.edu.tr) the tightly confined modes at each defect site, as illustrated in Fig. 1a [13,16,17]. Due to coupling between the localized cavity modes, a photonic defect band (waveguiding band) is formed within the stop band of the crystal. This is analogous to the transition from atomic-like discrete states to the continuous spectrum in solid-state physics. Recently, Bayer et al. observed formation of a photonic band due to coupling between the optical molecules [18].In this communication, we demonstrate the guiding of light through localized coupled optical cavity modes in 1D PBG structures which are fabricated from siliconoxide/silicon-nitride (SiO 2 /Si 3 N 4 ) pairs with λ/2 SiO 2 cavity layers. It is observed that nearly 100% transmission can be achieved throughout the waveguiding band. The dispersion relation, group velocity and photon lifetime of the coupled cavities are investigated within t...

Narrow-band and enhanced photoluminescence have been observed in hydrogenated amorphous-silicon-nitride microcavities. The distributed Bragg reflectors were fabricated using alternating layers of hydrogenated amorphous-silicon nitride and hydrogenated amorphous-silicon oxide. The microcavity resonance wavelength was designed to be at the maximum of the bulk hydrogenated amorphous-silicon-nitride luminescence spectrum. At the microcavity resonance, the phololuminescence amplitude is enhanced, while the photoluminescence linewidth is reduced with respect to the bulk hydrogenated amorphous-silicon nitride. © 2001 American Institute of Physics

Abstract. We investigated photoluminescence (PL) from one-dimensional photonic band gap structures. The photonic crystals, a Fabry-Perot (FP) resonator and a coupledmicrocavity (CMC) structure, were fabricated by using alternating hydrogenated amorphous-silicon-nitride and hydrogenated amorphous-silicon-oxide layers. It was observed that these structures strongly modify the PL spectra from optically active amorphous-silicon-nitride thin films. Narrow-band and wide-band PL spectra were achieved in the FP microcavity and the CMC structure, respectively. The angle dependence of PL peak of the FP resonator was also investigated. We also observed that the spontaneous emission increased drastically at the coupled-cavity band edge of the CMC structure due to extremely low group velocity and long photon lifetime. The measurements agree well with the transfer-matrix method results and the prediction of the tight-binding approximation. 42.70.Qs; 42.60.Da;78.66.Jg Ability to control spontaneous emission is expected to have practical importance in certain commercial applications. Thus, in the past decade, photonic band gap materials were proposed for alteration (inhibition and enhancement) of the spontaneous emission from atoms [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. PACS:Recently, we reported a new type of propagation mechanism in which photons move along the localized coupledcavity modes [15,16]. Moreover, it was observed that the group velocity tends to zero and photon lifetime increases drastically at the coupled-cavity band edges [17]. In this paper, we experimentally demonstrate the modification of spontaneous emission from the hydrogenated amorphous-siliconnitride active layers in a Fabry-Perot (FP) resonator and a coupled-microcavity (CMC) structure.Since the density of electromagnetic modes (ω) is modified by the surrounding environments, the spontaneous emission from atoms can be controlled by placing the atoms inside * Corresponding author. (Fax: +90-312/266-4579, E-mail: bayindir@fen.bilkent.edu.tr) cavities. The spontaneous emission rate is directly proportional to the photon density of modes via Fermi's golden rule:. Thus, it is expected that spontaneous emission from a CMC structure can be enhanced by a low group velocity.Our structures were composed of alternating hydrogenated amorphous-silicon-nitride (Si 3 N 4 ) and hydrogenated amorphous-silicon-oxide (SiO 2 ) multilayers [18]. The SiO 2 and Si 3 N 4 layers were deposited on glass and silicon substrates by plasma-enhanced chemical vapour deposition (PECVD) at 250• C. Nitrogen (N 2 ) balanced 2% silane (SiH 4 ), pure ammonia (NH 3 ) and nitrous oxide (N 2 O) were used as the silicon, nitride and oxide sources, respectively. The refractive indices and thicknesses of layers were n SiO 2 = 1.46, n

Original citationTanriseven, S., Maaskant, P. and Corbett, B. (2008)

Size dependent current-voltage measurements were performed on InGaAs quantum dot active region mesa diodes and the surface recombination velocity was extracted from current density versus perimeter/area plots using a diffusion model. An effective surface recombination value of 5.5 x 10(4) cm/s was obtained that can be reduced by more than an order of magnitude by selective oxidation of Al(0.9)Ga(0.1)As cladding layers. The values are three times smaller than those obtained for a single quantum well. The effect of p-type doping in the active region was investigated and found to increase the effective surface recombination. (C) 2011 American Institute of Physics. [doi:10.1063/1.3611387