Index guiding dependent effects in implant and oxide confined vertical-cavity lasers

Includes bibliographical references.Implant and oxide confined vertical-cavity surface-emitting lasers are compared in terms of properties dependent upon the nature of index guiding in the two structures including CW threshold current scaling with size, light-current linearity, pulsed operation delay, and beam profiles. The oxide confined lasers, fabricated by wet thermal oxidation, have a built-in index guide and thus exhibit substantially better properties than do lasers from the same wafer fabricated by proton implantation which rely on a thermal lens to reduce diffraction losses.This work was supported by the U.S. Department of Energy under Contract DEAC04-94AL85000

Improved AlGaInP-based red (670–690 nm) surface-emitting lasers with novel C-doped short-cavity epitaxial design

Includes bibliographical references (page 331).A modified epitaxial design leads to straightforward implementation of short (1λ) optical cavities and the use of C as the sole p-type dopant in AlGaInP/AlGaAs red vertical-cavity surface-emitting lasers (VCSELs). Red VCSELs fabricated into simple etched air posts operate continuous wave at room temperature at wavelengths between 670 and 690 nm, with a peak output power as high as 2.4 mW at 690 nm, threshold voltage of 2.2 V, and peak wallplug efficiency of 9%. These values are all significant improvements over previous results achieved in the same geometry with an extended optical cavity epitaxial design. The improved performance is due primarily to reduced optical losses and improved current constriction and dopant stability.This work was supported by the U.S. Department of Energy under Contract No. DE-AC04-94AL85000

High-efficiency and high-power vertical-cavity surface-emitting laser designed for cryogenic applications

Includes bibliographical references.We report the first vertical-cavity surface-emitting laser (VCSEL) that has been optimized for cryogenic applications near 77 K, with superior characteristics that include a high output power (Pout = 22 mW at I = 25 mA), high power conversion efficiency (ηd = 32%), low threshold voltage (Vth = 1.75 V) and current (Ith = 1.7 mA), and low power dissipation (9 mW at Pout = 2.0 mW) for a 20-μm-diameter device.This work was supported in part by AFOSR and the DOE under Contract No. DE-AC04-94AL85000

High power conversion efficiencies and scaling issues for multimode vertical-cavity top-surface-emitting lasers

Includes bibliographical references.We report advances in the power conversion efficiencies of vertical-cavity top-surface-emitting lasers defined by proton implantation. Efficiencies as high as 13.4% and 15.8% have been obtained for single-mode and multimode operation, respectively. Scaling issues are addressed including the size dependence of threshold current, series resistance, lasing output power, and power conversion efficiency. We find that devices between 15 μm and 25 μm diameters show the highest power conversion efficiency due to the threshold current not scaling with the conductance and output power. Device geometries with contact apertures both equal to and less than (overlapping) the active region diameter were investigated.This work was supported by the United States Department of Energy under Contract DE-AC04-94AL85000

Modal analysis of a small surface emitting laser with a selectively oxidized waveguide

Includes bibliographical references (page 2618).We describe studies of an index-guided ~4×3 µm2 vertical cavity surface emitting laser with a cw, room temperature 133 µA threshold current and 53% slope efficiency fabricated using selective wet thermal oxidation to provide optical and electrical confinement. While the device operates strictly single mode, a large number of transverse modes are evident in the subthreshold luminescence observed in both vertical and lateral directions. Despite the lumped nature of the index region, the transverse mode wavelengths agree very well with those predicted for a conventional distributed waveguide structure. Waveguide dimensions and an effective index step of 2% between the active and cladding region are determined by fitting the modal data.This work was supported by the United States Department of Energy under Contract No. DE-AC04-94AL85000

Research article - Comet 81P/Wild 2 under a microscope

The Stardust spacecraft collected thousands of particles from comet 81P/Wild 2 and returned them to Earth for laboratory study. The preliminary examination of these samples shows that the nonvolatile portion of the comet is an unequilibrated assortment of materials that have both presolar and solar system origin. The comet contains an abundance of silicate grains that are much larger than predictions of interstellar grain models, and many of these are high-temperature minerals that appear to have formed in the inner regions of the solar nebula. Their presence in a comet proves that the formation of the solar system included mixing on the grandest scales