RESUMEN
We present a fibre laser broadly tunable in a wavelength range from 1058 nm to 1640 nm based on a new type of metallic resonant leaky-mode diffraction grating and three fibre-pigtailed semiconductor optical amplifiers. For TM polarization in Littrow configuration, the grating has experimentally measured diffraction efficiency into the -1st reflected order of more than 90 % over a spectral range of 1417 nm to 1700 nm. The laser covered a spectral range of 331 nm within a tuning band of 558 nm without any adjustment of optics and its tuning range was limited by amplification bands of available semiconductor optical amplifiers.
RESUMEN
We experimentally investigate the dispersion relation of silicon-on-insulator waveguides in the 1.5 microm wavelength range by using a technique based on far-field Fourier-space imaging. The phase information of the propagating modes is transferred into the far field either by linear probe gratings positioned 1 microm away from the waveguide core or by residual gratings located on the sidewalls of the waveguide. As a result, the dispersion curve of rectangular and slot waveguides as well as the group index dispersion are accurately determined.
RESUMEN
If a one-dimensional (1D) or two-dimensional (2D) photonic bandgap (PBG) structure is incorporated into a planar optical waveguide, the refractive-index nonuniformity in the direction perpendicular to the waveguide plane responsible for waveguiding may affect its behavior detrimentally. Such influence is demonstrated in the paper by numerical modeling of a deeply etched first-order waveguide Bragg grating. On the basis of physical considerations, a simple condition for the design of 1D and 2D waveguide PBG structures free of this degradation is formulated; it is, in fact the separability condition for the wave equation. Its positive effect is verified by numerical modeling of a modified waveguide Bragg grating that fulfills the separability condition.
RESUMEN
Propagation of Ga(x)In(1-x)As(y)P (1-y) light-emitting-diode radiation through an optical fiber was found to affect its spectral curve very strongly, and the origin of this effect was analyzed. Various kinds of fibers were found to induce interferencelike modulations superimposed on the smooth spontaneous spectral curve of the diodes. We were able to show that when a monomode polarization-preserving fiber is used, the modulations are mostly due to intermodal interference.
RESUMEN
Analysis of a directional coupler by use of rigorous coupled-mode theory is presented. The coupling process is explained by the mutual coupling of modes of a single waveguide that is due to the presence of the other waveguide. It is explicitly shown by example that the radiation modes that take part in the coupling are just those needed to form the guided modes of the composite double-guide structure.
RESUMEN
A novel method of measuring the refractive-index profile of deep multimode planar waveguides is described. Unlike in mode spectroscopy, several modes are excited simultaneously by a prism coupler. Superposition of the modes forms a guided beam that refracts continuously inside the graded-index waveguide and reflects periodically from the waveguide surface. Measurement of the periodicity as a function of the excitation angle enables one to calculate the refractive-index profile of the waveguide.
