W. Streifer

Low threshold, high efficiency Ga1−xAlxAs single quantum well visible diode lasers grown by metalorganic chemical vapor deposition

Laser threshold current density and emission wavelength were investigated for broad area single quantum well double heterostructure (SQW DH) Ga1−xAlxAs lasers grown by metalorganic chemical vapor deposition (MOCVD) under pulsed operation at room temperature. The shortest lasing emission wavelength was 7065 A. At that wavelength, the threshold current density was 1 kA/cm2 for a Fabry–Perot diode of 500‐μm cavity length and the external differential quantum efficiency was 48%. These values are significantly better than those previously reported for Ga1−xAlxAs DH lasers operating under similar conditions at the same wavelengths. We attribute the improved performance in part to the quantum size effect (active layer thickness 400– 600 A).

Coupled-mode equations for multimode waveguide systems in isotropic or anisotropic media

Coupled-mode theory for parallel waveguides is extended to include systems with multimode guides. The basic set of coupled differential equations is similar to that for single-mode guides, but the matrices are more broadly defined to allow for coupling among all the modes. Cases of embedding medium are also considered. anisotropic dielectric waveguides and/or an anisotropic embedding medium are also considered.

Leaky wave room-temperature double heterostructure GaAs:GaAlAs diode laser

Operation of a new cleaved facet room‐temperature double heterostructure GaAs:GaAlAs laser utilizing leaky wave coupling through the substrate is reported. The coupling mechanism is analogous to that of prism coupling from a waveguide, but no external components are used. The laser produces a highly collimated output beam with approximately 2°×8° divergence. The peak pulsed beam power at 2 times threshold is 1.5 W from one end with approximately one‐third of this power in the collimated beam. The total external differential quantum efficiency is on the order of 35%. These desirable characteristics are obtained at the expense of threshold current increases of approximately 30%.

High‐power (cw) in‐phase locked ‘‘Y’’ coupled laser arrays

Buried heterostructure phased array lasers have been fabricated with ‘‘Y’’ coupling regions to produce in‐phase locking. The far‐field pattern corresponding to the in‐phase emission of ten waveguides is stable under wide variations of operating conditions. Power outputs of up to 200 mW cw and 400 mW pulsed are obtained from a ten‐element (50 μm aperture) array. By monitoring the far‐field pattern under impulse excitation, the phase locking is shown to evolve in less than 300 ps.

Low‐divergence beams from grating‐coupled composite guide heterostructure GaAlAs diode lasers

Room‐temperature operation of a new grating‐coupled heterostructure diode laser is reported. The laser contains two GaAs layers separated by a GaAlAs layer. One of the GaAs layers is electrically pumped, whereas the other is corrugated. Light is distributed over both layers and the grating couples out low‐divergence polarized beams approximately normal to the p‐n junction. Room‐temperature thresholds as low as 2 kA/cm2 have been observed.

Output coupling and distributed feedback utilizing substrate corrugations in double-heterostructure GaAs lasers

Conventional double‐heterostructure lasers with a thin n‐Ga1−yAlyAs layer grown on a periodically corrugated n‐GaAs substrate have been operated at room temperature. The evanescent tail of the guided mode interacts with the substrate corrugation to produce both distributed feedback and output coupling perpendicular to the waveguide. A single polarized low‐divergence (0.65°×10°) output beam at 8825 A radiated normal to the waveguide was obtained from such a diode with cleaved end facets at a threshold current of 4.1 kA/cm2.

Ultrahigh power 38 W continuous‐wave monolithic laser diode arrays

Continuous‐wave output power levels of 38 W from one facet have been obtained from a 1 cm monolithic AlGaAs laser array with a 2 mm total active aperture width. One of the diodes has been operated under constant current conditions (initial output power of 5 W) at room temperature for over 1100 h.

Distributed feedback buried heterostructure diode laser

We report room‐temperature operation of a buried heterostructure distributed feedback diode laser. The device operates in a single TE polarized longitudinal mode over a temperature range from 232 to 324 K and exhibits a temperature sensitivity of 0.72 A/K. In comparison, the variation for a similar Fabry‐Perot diode is 3.4 A/K.

Phased‐array lasers with a uniform, stable supermode

A phased‐array semiconductor laser with identical coupled waveguides is designed to favor a uniform, stable supermode. All but the two outermost waveguides are equally spaced with the placement of the first and Nth guides chosen so as to increase their coupling coefficient by √2. The lowest and highest order supermodes have a uniform near‐field intensity envelope and utilize the injected charges more efficiently. Whichever of these is favored at threshold should remain stable with increasing pumping or under modulation.

High power, AlGaAs buried heterostructure lasers with flared waveguides

High power, buried heterostructure laser with flared waveguide horns have been grown by a two‐step metalorganic chemical vapor deposition process. Powers up to 120 mW cw in a single longitudinal and transverse mode have been obtained from a single stripe laser. The flared waveguides decrease the lateral far‐field divergence from 25° to 11° while supporting only the lowest order transverse mode.