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In this paper we report a numerical study of a palladium-based metallo-dielectric photonic band gap structure for the purpose of detecting H2. In particular, and as an example, we will explore applications to the diagnosis of lactose malabsorption, more commonly known as lactose intolerance condition. This pathology occurs as a result of an incomplete absorption or digestion of different substances, causing an increased spontaneous emission of H2 in human breath. Palladium is considered in order to exploit its well known ability to absorb hydrogen spontaneously. The proposed structure is particularly able to detect the lactose malabsorption level of the patient with relatively high sensitivity and rapidity. [ABSTRACT FROM AUTHOR]

The influence of high energy radiations on the performance of silicon-on-insulator photonic devices, such as straight waveguides, ring resonators and Raman lasers based on resonant microcavities, has been investigated theoretically in the near infrared. The modeling is based on a generalized full-vectorial wave equation system which also includes deep defect rate equations. Simulation results are compared with the state-of-the-art, demonstrating a very good agreement between theoretical predictions and experiments reported in literature in the case of both ionizing and nonionizing events. Moreover, a parametric analysis is presented in order to investigate the degradation mechanisms of photonic device performance that occur under the influence of radiation bombardment. [ABSTRACT FROM AUTHOR]

A mid-IR amplifier consisting of a tapered chalcogenide fiber coupled to an Er3+-doped chalcogenide microsphere has been optimized via a particle swarm optimization (PSO) approach. More precisely, a dedicated three-dimensional numerical model, based on the coupled mode theory and solving the rate equations, has been integrated with the PSO procedure. The rate equations have included the main transitions among the erbium energy levels, the amplified spontaneous emission, and the most important secondary transitions pertaining to the ion-ion interactions. The PSO has allowed the optimal choice of the microsphere and fiber radius, taper angle, and fiber-microsphere gap in order to maximize the amplifier gain. The taper angle and the fiber-microsphere gap have been optimized to efficiently inject into the microsphere both the pump and the signal beams and to improve their spatial overlapping with the rare-earth-doped region. The employment of the PSO approach shows different attractive features, especially when many parameters have to be optimized. The numerical results demonstrate the effectiveness of the proposed approach for the design of amplifying systems. The PSO-based optimization approach has allowed the design of a microsphere-based amplifying system more efficient than a similar device designed by using a deterministic optimization method. In fact, the amplifier designed via the PSO exhibits a simulated gain G = 33.7 dB, which is higher than the gain G = 6.9 dB of the amplifier designed via the deterministic method. [ABSTRACT FROM AUTHOR]

The bidirectional beam propagation method based on the method of lines is proposed as an innovative and efficient algorithm to investigate the optical properties of photonic band gap (PBG) structures. A few examples illustrate the application of this technique to the modeling of passive, lossy and active one-dimensional and index confined PBG structures. The algorithm results are validated by comparison with those obtained via the transfer matrix method, the mode-matching method and the finite difference time domain method. With respect to these methods, the present algorithm exhibits accurate results with reduced computer resources. [ABSTRACT FROM AUTHOR]

Abstract: A number of numerical and analytical methods with different complexity can be exploited to analyse fibre amplifiers. Conventional approaches make the refinement and design of the devices extremely time consuming, especially when several design parameters have to be simultaneously optimised to obtain the desired performance in terms of gain and noise figure. In order to tackle this issue, a method based on an artificial neural network to perform the refinement and design of erbium doped photonic crystal fibre amplifiers is proposed in this paper. The capability of the neural network to capture the nonlinear functional link among the physical and geometrical characteristics of the fibre amplifier and its gain and noise figure is exploited. In the refinement it is employed to determine the optimal values of the parameters maximising the gain. In the design, it is used to develop an inverse problem solver in order to determine the values of the parameters corresponding to the known values of gain. Numerical results show that the proposed approach finds the refinement/design parameters in good accordance with respect to the conventional one. [Copyright &y& Elsevier]