Broad-area Semiconductor Lasers Research Articles

Spatiotemporal chaos in broad-area semiconductor lasers

We study the space–time dynamical behavior of broad-area semiconductor lasers, using an extended phenomenological laser model to include transverse diffraction of the counterpropagating optical fields and transverse diffusion of carriers. Numerical results show that the profile of the output intensity exhibits spatiotemporal chaos by way of changing random filaments. A small confinement factor and/or linewidth enhancement factor can prevent instabilities. Simulations also confirm experimental results showing that a half-symmetric unstable resonator with a suitable mirror curvature restores stability.

Lateral modes of broad area semiconductor lasers: theory and experiment

Calculations of the lateral modes of an ideal broad area laser, including the nonlinear interaction between the carriers and the optical field, are made. The results include periodically modulated near fields and single- and double-lobed far fields similar to those previously measured. The unsaturable losses are higher and quantum efficiencies are lower than those determined from plane-wave approximations. Broad area InGaAs-GaAlAs-GaAs quantum-well lasers were fabricated and measured and found to closely agree with the theory in near, far, and spectrally resolved near fields. An occultation experiment on the far field confirms previously predicted unstable resonatorlike modes with V-shaped fronts.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Lateral-mode discrimination in broad-area semiconductor lasers with a smooth spatially filtering output facet

We present numerical simulations of broad-area semiconductor lasers with smooth spatial filtering at the output facet. The beam-propagation and Prony methods are used to calculate the beam characteristics and discrimination against higher-order lateral modes of the laser devices. With an output facet having a Gaussian reflectivity profile, the fundamental lateral mode is favored. Discrimination between the two lowest-order modes increases significantly with narrow reflectivity profiles.

Broad-area tandem semiconductor laser

A tandem combination of a uniform gain broad-area semiconductor laser and a (lateral) periodic gain section displays a stable, near-diffraction-limited single-lobed far-field pattern. The GaAs/GaAlAs quantum well lasers display a high degree of coherence across 60-μm-wide apertures provided that the broad-area section is sufficiently long.

Broad-area semiconductor lasers with gain-length variation for lateral mode control: The bow-tie geometry laser

A novel idea is proposed to control the spatial mode profile of broad-area semiconductor lasers in which the cumulative optical gain in the direction of light propagation is tailored by varying the effective length of the contact electrode across the lateral direction. Special interest is on a structure with the highest gain near the center of the device so as to favor the lower-order lateral modes of oscillation. Preliminary experiments indicate that the concept works as intended.

Saturable nonlinear dielectric waveguide with applications to broad-area semiconductor lasers

Self-focusing in a passive dielectric waveguide with a saturable nonlinearity is studied. The eigensolutions constitute a good approximation to the lateral modes of broad-area semiconductor lasers under low-duty-cycle pulsed conditions. The laser modes are predicted to consist of adjacent filaments coupled in phase, leading to a single-lobed far field, and to be stable with increased current injection above saturation intensity. The ultimate filament spacing is inversely proportional to the threshold gain, and thus wider filaments are expected in low-threshold broad-area lasers.

Linear tailored gain broad area semiconductor lasers

Tailored gain semiconductor lasers capable of high-power operation with single-lobed, nearly diffraction limited beamwidths only a few degrees wide have been demonstrated in proton implanted chirped arrays and halftone broad area lasers. We analyze lasers with a linear gain gradient, and obtain analytic approximations for their unsaturated optical eigenmodes. Unlike a uniform array, the fundamental mode of a linear tailored gain laser is the lasing mode at threshold. Mode discrimination may be controlled by varying the spatial gain gradient. All modes of asymmetric tailored gain waveguides have single-lobed far-field patterns offset from 0°. Finally, we utilize tailored gain broad area lasers to make a measurement of the anti-guiding parameter, and find b = 2.5 \pm 0.5 , in agreement with previous results.

Phase-locked controlled filament laser

A broad area semiconductor laser with induced self-focusing in the form of a phase-locked array of filaments is demonstrated. The multifilamentary laser has a single lobed and nearly diffraction limited far-field pattern, for injection currents up to I≂1.85Ith.

Fundamental lateral mode oscillation via gain tailoring in broad area semiconductor lasers

We show that by employing gain tailoring in a broad area semiconductor laser we achieve fundamental lateral mode operation with a diffraction-limited single-lobed far-field pattern. We demonstrate a tailored gain broad area laser 60 μm wide which emits 450 mW per mirror into a stable, single-lobed far-field pattern 3 1/2° wide at 5.3 Ith.

Tailored-gain broad-area semiconductor laser with single-lobed diffraction-limited far-field pattern

We demonstrate a 60 μm-wide asymmetric tailored-gain broad-area semiconductor laser with a single-lobed diffraction-limited far-field pattern 2.5° wide. The method used to achieve gain tailoring may be used to create nearly arbitrary two-dimensional spatial gain distributions within a broad-area laser.