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Tehranchi A.,University of Montreal | Morandotti R.,INRS EMT | Kashyap R.,University of Montreal
Optics Express | Year: 2011

High-efficiency ultra-broadband wavelength converters based on double-pass quasi-phase-matched cascaded sum and difference frequency generation including engineered chirped gratings in lossy lithium niobate waveguides are numerically investigated and compared to the single-pass counterparts, assuming a large twin-pump wavelength difference of 75 nm. Instead of uniform gratings, few-section chirped gratings with the same length, but with a small constant period change among sections with uniform gratings, are proposed to flatten the response and increase the mean efficiency by finding the common critical period shift and minimum number of sections for both single-pass and double-pass schemes whilst for the latter the efficiency is remarkably higher in a low-loss waveguide. It is also verified that for the same waveguide length and power, the efficiency enhancement expected due to the use of the double-pass scheme instead of the single-pass one, is finally lost if the waveguide loss increases above a certain value. For the double-pass scheme, the criteria for the design of the low-loss waveguide length, and the assignment of power in the pumps to achieve the desired efficiency, bandwidth and ripple are presented for the optimum 3-section chirped-gratings-based devices. Efficient conversions with flattop bandwidths > 84 nm for lengths < 3 cm can be obtained. © 2011 Optical Society of America. Source

Szczecinski L.,INRS EMT
IEEE Transactions on Communications | Year: 2012

In this work we analyze the problem of correction of the reliability metrics (L-values) in bit-interleaved coded modulation (BICM) receivers. First, we propose a method for finding the linear correction factors that minimize the probability of error of a maximum likelihood decoder that uses the corrected L-values. To this end, we use the efficient approximation of the pairwise error probability in the domain of the cumulant generating functions (CGF) of the L-values and conclude that the optimal correction factors are equal to the twice of value of the saddlepoint of the CGF. Next, a simple extension of the proposed method to the non-linear correction is presented. We provide numerical examples demonstrating improvements attainable with the proposed method comparing it to the competitive solutions. © 2012 IEEE. Source

Djerafi T.,INRS EMT | Wu K.,Ecole Polytechnique de Montreal
IEEE Transactions on Antennas and Propagation | Year: 2012

This communication presents a low-cost 77-GHz switched-beam slot antenna array driven by a Butler matrix. In the proposed configuration, four broadband couplers are combined and crossovers are effectively avoided. In this case, the overall circuit and beamforming network losses are considerably reduced. A 4$\,\times\,$4 planar SIW Butler matrix is designed and demonstrated for integrated beamforming network applications, which exhibits about 7 degrees phase error and $\pm {0.75}~{\rm dB}$ coupling imbalance over 11% bandwidth. This experimentally prototyped matrix is integrated with a four-array slot antenna on the same substrate. An alternating displacement of the slots in subsequent radiating waveguides is proposed to save the arrangement of the input ports and to achieve broadband performances. Measured radiation patterns are in good agreement with simulated counterparts over the proposed 77-GHz frequency range. © 1963-2012 IEEE. Source

Moss D.J.,University of Sydney | Morandotti R.,INRS EMT | Gaeta A.L.,Cornell University | Lipson M.,Cornell University
Nature Photonics | Year: 2013

Nonlinear photonic chips can generate and process signals all-optically with far superior performance to that possible electronically-particularly with respect to speed. Although silicon-on-insulator has been the leading platform for nonlinear optics, its high two-photon absorption at telecommunication wavelengths poses a fundamental limitation. We review recent progress in non-silicon CMOS-compatible platforms for nonlinear optics, with a focus on Si3N4 and Hydex®. These material systems have opened up many new capabilities such as on-chip optical frequency comb generation and ultrafast optical pulse generation and measurement. We highlight their potential future impact as well as the challenges to achieving practical solutions for many key applications. © 2013 Macmillan Publishers Limited. Source

Driben R.,Tel Aviv University | Driben R.,University of Paderborn | Hu Y.,INRS EMT | Chen Z.,San Francisco State University | And 2 more authors.
Optics Letters | Year: 2013

By means of direct simulations and theoretical analysis, we study the nonlinear propagation of truncated Airy pulses in an optical fiber exhibiting both anomalous second-order and strong positive third-order dispersions (TOD). It is found that the Airy pulse first reaches a finite-size focal area as determined by the relative strength of the two dispersion terms, and then undergoes an inversion transformation such that it continues to travel with an opposite acceleration. The system notably features tight focusing if the TOD is a dominant factor. These effects are partially reduced by Kerr nonlinearity. © 2013 Optical Society of America. Source

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