Amos A. Hardy

Analysis of waveguided Gaussian beams coupled by misaligned or curved gratings

Coupled contradirectional mode equations are derived to describe Hermite-Gaussian beam interactions in corrugated thin-film waveguides when the grating teeth are curved and/or tilted. Coupling coefficients are evaluated for identical and hybrid modes. The problem of focusing a guided Gaussian beam by reflection from a curved grating is considered. It is shown that the grating curvature should serve to match the phase fronts of the contradirectional Gaussians and the grating should extend axially to include the region where the two beam widths are approximately equal.

Coherent radiation from a broad-area semiconductor laser in an external cavity

A compact external cavity configuration consisting of a gain guided array, a graded index lens, and a mode selective mirror was investigated. Results obtained from this external cavity configuration show 410 mW total power (CW) with a diffraction limited far field pattern.

High-power coherent operation of 2-D monolithically integrated master-oscillator power amplifiers

Two-dimensional monolithically integrated master oscillator power amplifiers have been fabricated that emit in a single longitudinal mode to an output power of 4.5 W.

Grating-coupled surface emitters: sensitivity to length-induced phase variations

The steady-state properties of a two-gain section/three-grating surface-emitting laser are studied theoretically as a function of length-induced phase variations. In particular, the optical length of one gain section is varied with respect to the other by up to one grating period. It is found that several mode hops occur. Although the number of these can be reduced by optimizing the design, stable single-mode laser operation requires control of the optical length of each gain and grating section to better than one wavelength.

Optical characteristics of multiple grating surface-emitting semiconductor lasers

The coherent operation of one-dimensional linear arrays of grating-coupled surface-emitting lasers is experimentally investigated, for different laser designs (gain lengths, grating parameters. For laser arrays with shallow grating teeth and strong interelement coupling, a diffraction-limited far field of 0.012 deg FWHM was obtained from up to six coupled lasers extending over a length of 3.5 mm.