D. Wilt

The intrinsic electrical equivalent circuit of a laser diode

The basic electrical equivalent circuit of a laser diode is derived. The effects of spontaneous emission and self-pulsations are included. It is found that self-pulsations are represented by a negative resistance in the model. Application of this model suggests purely electronic methods of suppressing relaxation oscillations in laser diodes.

A self-consistent static model of the double- heterostructure laser

A new static model of the double-heterostructure laser is presented which treats the p-n junction in the laser in a consistent manner. The solution makes use of the finite-element method to treat complex diode geometries. The model is valid above lasing threshold and shows both the saturation in the diode junction voltage at threshold as well as lateral mode shifts associated with spatial hole burning. Several geometries have been analyzed and some specific results are presented as illustration.

A monolithic integration of GaAs/GaAlAs bipolar transistor and heterostructure laser

A GaAlAs double-heterostructure laser has been monolithically integrated with a heterojunction bipolar transistor on a GaAs substrate. Integration is achieved by means of a mutually compatible structure formed by Be ion implantation. Typical pulsed threshold currents for the laser are 60 mA, and the transistors have a typical common-emitter current gain of 900.

A monolithically integrated optical repeater

A monolithically integrated optical repeater has been fabricated on a single‐crystal semi‐insulating GaAs substrate. The repeater consists of an optical detector, an electronic amplifier, and a double heterostructure crowding effect laser. The repeater makes use of three metal semiconductor field effect transistors, one of which is used as the optical detector. With light from an external GaAlAs laser incident on the detector, an overall optical power gain of 10 dB from both laser facets was obtained.

The effect of lateral carrier diffusion on the modulation response of a semiconductor laser

The effect of lateral carrier diffusion upon the modulation characteristics of the semiconductor laser is investigated. A self‐consistent analysis of the spatially dependent rate equations is performed using a finite element model. The transverse junction stripe laser is treated as an example and a comparison is made between lateral carrier diffusion and spontaneous emission as damping mechanisms for the resonance peak. Experimental results bear out the conclusion that the relaxation resonance in this device is damped mainly by lateral carrier diffusion. In addition, a simple analytic result is presented which illustrates qualitatively the effect of lateral carrier diffusion upon such devices. The conclusion from this result is that lateral carrier diffusion serves to damp the relaxation resonance in the semiconductor laser quite well, but probably will not serve to improve the upper limit on modulation frequency as might have been suspected.

Whispering gallery lasers on semi‐insulating GaAs substrates

Double heterostructure lasers are described in which light is guided by total internal reflection along a dielectric interface formed by the perimeter of an etched mesa. By means of the crowding effect, injection current is restricted to a narrow strip adjacent to the edge of the mesa. This results in the preferential excitation of optical modes which are localized in the vicinity of the dielectric interface. Both half-ring lasers formed at a single cleaved facet and quarter-ring lasers formed at a cleaved corner were fabricated.

Be‐implanted (GaAl)As stripe geometry lasers

(GaAl)As double‐heterostructure stripe geometry lasers have been fabricated using Be ion implantation. Pulsed threshold currents as low as 21 mA have been found. The light‐vs‐current characteristics were kink‐free up to 10 mW output power and the measured differential quantum efficiency was 45%.

Low threshold Be implanted (GaAl)As laser on semi-insulating substrate

Be implanted stripe geometry double heterostructure lasers have been fabricated on a semi-insulating GaAs substrate, with threshold currents as low as 15 mA for a cavity length of 100 μm. The laser has been monolithically integrated with a metal-semiconductor field-effect transistor.

Single‐growth embedded epitaxy AlGaAs injection lasers with extremely low threshold currents

A new type of strip-geometry AlGaAs double-heterostructure laser with an embedded optical waveguide has been developed. The new structure is fabricated using a single step of epitaxial growth. Lasers with threshold currents as low as 9.5 mA (150 µm long) were obtained. These lasers exhibit operation in a single spatial and longitudinal mode, have differential quantum efficiencies exceeding 45%, and a characteristic temperature of 175° C. They emit more than 12 mW/facet of optical power without any kinks.

Gallium Arsenide Monolithic Optoelectronic Circuits

The optical properties of GaAs make it a very useful material for the fabrication of optical emitters and detectors. GaAs also possesses electronic properties which allow the fabrication of high speed electronic devices which are superior to conventional silicon devices. Monolithic optoelectronic circuits are formed by the integration of optical and electronic devices on a single GaAs substrate. Integration of many devices is most easily accomplished on a semi-insulating (SI) sub-strate. Several laser structures have been fabricated on SI GaAs substrates. Some of these lasers have been integrated with Gunn diodes and with metal semiconductor field effect transistors (MESFETs). An integrated optical repeater has been demonstrated in which MESFETs are used for optical detection and electronic amplification, and a laser is used to regenerate the optical signal. Monolithic optoelectronic circuits have also been constructed on conducting substrates. A heterojunction bipolar transistor driver has been integrated with a laser on an n-type GaAs substrate.