Y junctions in photonic crystal channel waveguides: high transmission and impedance matching

We investigate the efficiency of transmission through photonic crystal Y junctions and show the importance of matching mode symmetries. Furthermore, we show that by adding tuning holes to the input waveguide it is possible to achieve almost perfect impedance matching, leading ideally to unitary transmission through the junction. The model system is based on a triangular photonic lattice of holes in dielectrics to reflect experimental reality.     

Time-domain Fourier optics for polarization-mode dispersion compensation

We report on a novel technique to compensate for all-order polarization-mode dispersion. By means of this technique, based on a suitable combination of phase modulation and group-velocity dispersion, we compensated for as much as 60 ps of differential group delay that affected a 10-Gbit/s return-to-zero data stream.     

Superprism Behaviour of an Array of Photonic Crystal Waveguides

The behaviour of an array of photonic crystal waveguides is numerically investigated. It is shown that high dispersion may be achieved in the telecommunication window around 1550 nm, with a device whose dimensions are in the order of half a mm².     

Noise in optical amplifiers

This article presents an application of a recently published probablistic model for traveling wave optical amplification. Both optical signal and amplified spontaneous emission (ASE) noise are modeled as bunches of photons traveling along the amplifying region with size varying according to simple random rules. The results of the theory enable one to obtain a complete and accurate characterization of the signal and noise counting at the amplifier output. On the basis of the above statistics, we find a realistic evaluation of the limits imposed by both quantum and ASE noise on the performances of a receiver including an optical amplifier at a preamplifier stage.     

Energy flow in negative index materials

From Maxwell's equations, we compute the speed and the direction of propagation of active power refractedfrom air into a negative index material. We prove, both analytically and numerically that the power mayrefract positively even if phase fronts refract negatively. Considerations on the usage of ray optics inproblems involving negative index materials are drawn.     

Long-range soliton interactions in dispersion-managed links

A numerical analysis of soliton propagation in a dispersion-compensated transmission system reveals the presence of a small dispersive-wave contribution to the propagating soliton that increases dramatically whenever the input soliton energy is detuned from its optimal value. A straightforward consequence of the dispersive-wave emission is an unexpectedly strong contribution to the long-range soliton-soliton interaction. We show that the combination of long- and short-range interactions induces soliton timing jitter that grows larger than that which arises from the Gordon-Haus effect.     

Compact polarization rotators for integrated polarization diversity in InP-based waveguides

We present the design, fabrication, and operation of a polarization converter based on angled waveguides in the InP/InGaAsP material system. By combining design elements from mode evolution and birefringent devices, the total device length is kept short (less than 50 microm) and the insertion efficiency high at 81%+/-19%, which corresponds to an insertion loss of 1 dB. Devices operate broadband, i.e., the polarization conversion exceeds 15 dB over a 100 nm wavelength range. A polarization rotator with these specifications is a prime candidate for use in an integrated polarization diversity scheme.     

Lossless tapers,Gaussian beams,free-space modes: Standing waves versus through-flowing waves

It was noticed in the past that, to avoid physical inconsistencies, some basic features of waves flowing through Marcatili's lossless tapers must be different from those of standing waves in the same structures. In this paper, we first present numerical results (based on an extended BPM algorithm) which reconfirm this statement. Next, we explain this surprising behavior as straightforward consequences of Maxwell's equations. Finally, we show that similar situations occur for Gaussian beams in a homogeneous medium, and free-space modes expressed in terms of Bessel functions.