Peter Unger

Gain, refractive index, linewidth enhancement factor from spontaneous emission of strained GaInP quantum-well lasers

Unamplified spontaneously emitted light was measured through openings in the top contact of GaInP strained quantum-well ridge lasers. The data was recorded over a spectral range from 1.65 to 2.25 eV for different injection currents below threshold. Hakki-Paoli gain measurements of the same devices were used to determine the quasi-Fermi level separation and the scaling constant needed to calculate the modal gain from spontaneous emission spectra. The refractive index change due to current injection and the linewidth enhancement factor were derived from this data. >

MOVPE of AlGaInP/GaInP heterostructures for visible lasers

Abstract The current status of MOVPE for high-quality AlGaInP/GaInP heterostructure visible laser diodes is reviewed. It is shown that a detailed understanding of atomic ordering, heterointerface properties, and non-radiative traps in AlGaInP and dopant incorporation is necessary to obtain high-performance laser diodes emitting in the 600 nm range. In detail, the influence of a PH3 purifier on optical properties of AlGaInP and AlGaInP/GaInP heterostructures is discussed, and for controlled p-doping of AlGaInP, the effects of Zn and Mg incorporation are compared. Improvements in material quality and doping control have enabled us to realize index guided, AlGaInP/GaInP double heterostructure lasers emitting at λ ∼ 670 nm with a cw output power exceeding 20 mW and a maximum operation temperature of 100°C.

Low-threshold strained GaInP quantum-well ridge lasers with AlGaAs cladding layers

Visible lasers with two strained GaInP quantum wells and AlGaAs cladding layers have been fabricated using metalorganic vapor phase epitaxy. A dry-etched surface ridge has been chosen as a device structure, which results in a small astigmatism and a low threshold current. Owing to an electroplated heat spreader on top of the ridge, the devices can be operated continuous-wave (CW) junction-side-up at temperatures up to 100 degrees C. Lasers mounted junction-side-down with coated mirror facets operating at 30 mW output power show single-mode behavior and good reliability, as proven by a lifetime test of over 3000 h. >

High-resolution electron-beam lithography for fabricating visible semiconductor lasers with curved mirrors and integrated holograms

Abstract Red-emitting (Al)GaInP semiconductor laser diodes with dry-etched mirror facets have been fabricated using chemically assited ion-beam etching. These devices operate single mode up to CW output powers of 30 mW. Their properties are comparable to those of lasers with cleaved mirrors. Additionally, lasers with concave and convex facets have been realized using high-resolution electron-beam lithography to define the mirror shapes. The horizontal far-field behavior of the laser is influenced by varying the shape of the facets. The same technology can be used for integrating computer-generated holograms working as focussing grating couplers.

Al)GaInP laser with lateral confinement by epitaxial growth on nonplanar substrates

The authors present an AlGaInP/GaInP strained QW laser with AlGaAs cladding layers grown over nonplanar substrates. Excellent device quality and performance is obtained on substrates patterned with ridges prior to epitaxial growth. The lateral current and carrier confinement achieved by exploiting the disordering of the neutral superlattice at ridge sidewalls with shallow angles results in a threshold current density for 5- mu m-wide stripes that is one-half that of conventional devices. The potential of this device for high electrical-to-optical conversion makes it well suited for applications to dense addressable laser arrays.<<ETX>>