Optical sensors based on the surface plasmon resonance (SPR) effect are generally designed in a prism coupling configuration. Metal gratings can also be used to support surface plasmons, in turn allowing for the design of alternative, SPR based, sensor configurations. Determination of design parameters for developing such sensors is an important step for fabrication of these devices. In this paper the spectral dependence of sinusoidal metal grating parameters, represented by amplitude and periodicity, for front surface sensors is calculated to allow maximum sensitivity of the device. Results may be an important tool for those investigators involved in developing new applications of the technique.Index Terms -Optical sensors, Gratings, Optical diffraction, Coupled Mode Analysis. I. INTRODUCTION The surface plasmon resonance (SPR) effect in metals has important applications in biological and chemical[1] sensing, in drug development in the pharmaceutical industry [2], in photonics devices [1], [3] etc. In the field of SPR-based optical sensors, the Kretschmann's prism coupling configuration [4] is generally employed [5]. A metal grating type configuration [6]is also feasible for SPR-based sensor devices. The latter approach is attractive relative to the former, because it eliminates the need of the prism that couples the driving laser beam to the surface oscillation on the metal. On the other hand, diffraction gratings fabricated to a given specification are expensive. However, as shown in the literature inexpensive gold-coated diffraction gratings in the form of commercial CD-R [6] type optical storage disks [7], can support surface plasmon oscillations and can serve as lowcost substrates for fabrication of SPR-based optical sensors.One important step prior to fabrication or for use of prefabricated grating substrates for sensor devices is the determination of parameters that maximize device performance at a given wavelength. In this paper, we use coupled mode analysis to determine the relative intensities of diffracted orders reflected from a sinusoidal metal surface. From these, optimum parameters for maximum sensitivity of front surface optical sensors based on the SPR effect on sinusoidal metal gratings are obtained.For a given wavelength, grating amplitude and periodicity are determined so as to maximize the value of the maximum slope of the angular dependent zero-order reflectance curve, under the SPR effect, a criterion proposed by Fontana[5] for the case of sensors optimized for non-absorbing media in the Kretschmann prism coupling configuration. An example of design parameters for a front surface, grating type, SPRbased, device for gas sensing applications with maximum sensitivity at normal incidence is presented. II. GRATING CONFIGURATION AND THE SPR EFFECTThe configuration discussed in this work, shown in Fig 1, consists of two semi-infinite media, a dielectric and a metal with relative permittivities ε 1 and ε 2 , respectively. The metal surface has a sinusoidal profile with amplitude h and periodicity...

The knowledge about the true nature of the traffic in computer networking is a key requirement in the design of such networks. The phenomenon of self-similarity is a characteristic of the traffic of current client/server packet networks in LAN/ environments dominated by network technologies such as Ethernet and the TCP/IP protocol stack. The development of networks traffic simulators, which take into account this attribute, is necessary for a more realistic description the traffic on these networks and their use in the design of resources (contention elements) and protocols of flow control and network congestion. In this scenario it is recommended do not adopt standard traffic models of the Poisson type.

No abstract

ext Generation etworks ( xG ), as pursued by international standards development organizations, represent the telecommunication operator approach to provide convergent multimedia experience for their users with improved support for mobility and unfettered service access. In contrast, research efforts in so-called ew Generation etworks ( wG ), such as the Japanese project Akari and the European Future Internet initiatives, are part of an exciting trend towards re-architecting the Internet. Despite the enormous interest regarding both lines of work, few comparisons between their design approaches have been discussed in the literature. This paper provides a first glance comparison between key aspects of both proposals.

No abstract