Design, fabrication, and characterization of deep-etched waveguide gratings

One-dimensional (1-D) deep-etched gratings on a specially grown AlGaAs wafer were designed and fabricated. The gratings were fabricated using state-of-the-art electron beam lithography and high-aspect-ratio reactive ion etching (RIE) in order to achieve the required narrow deep air slots with good accuracy and reproducibility. Since remarkable etch depths (up to 1.5 /spl mu/m), which completely cut through the waveguide core layer, have been attained, gratings composed of only five periods (and, thus, shorter than 6 /spl mu/m) have a bandgap larger than 100 nm. A defect was introduced by increasing the width of the central semiconductor tooth to create microcavities that exhibit a narrow transmission peak (less than 7 nm) around the wavelength of 1530 nm. The transmission spectra between 1460 and 1580 nm have been systematically measured, and the losses have been estimated for a set of gratings, both with and without a defect, for different periods and air slot dimensions. Numerical results obtained via a bidirectional beam propagation code allowed the evaluation of transmissivity, reflectivity, and diffraction losses. By comparing experimental results with the authors' numerical findings, a clear picture of the role of the grating's geometric parameters in determining its spectral features and diffractive losses is illustrated

Nonlinear transmission properties of a deep-etched microstructured waveguide

In this letter, we investigate the nonlinear transmission properties of a one-dimensional micro-structured AlGaAs waveguide with a defect in the middle of a deep-etched Bragg grating. The transmitted spectrum depends on the spectral position of the incident pulse spectrum with respect to the defect mode as well as the pulse intensity. These findings are very important for all optical switching applications and can be explained by the interplay between self-phase modulation of the incident 250 fs pulses in the waveguide and the filtering properties of the defect mode

Quasi phase matching in GaAs–AlAs superlattice waveguides through bandgap tuning by use of quantum-well intermixing

We report the observation of second-harmonic generation by type I quasi phase matching in a GaAs–AlAs superlattice waveguide. Quasi phase matching was achieved through modulation of the nonlinear coefficien

Asymmetric spectrum evolution of high power short pulses in AlGaAs waveguides

We measured the self-phase modulation spectra at the output of deep-etched AlGaAs waveguides. The light source was an OPO laser system providing 250 fs long pulses, at wavelengths around 1520 nm, with a peak power as high as 1 kW. FROG measurements of the OPO pulses reveal their asymmetric shape. The multi-peak spectra, observed at the waveguide output, show a dramatic asymmetry and a power shift towards short wavelengths. The interplay between the Kerr non-linearity, dispersion and self-steepening amplifies the initial slight asymmetry of the injected spectrum. Experimental results compare favourably with the numerical solution of the generalized non-linear Schrödinger equation