S. Margalit

On the linewidth enhancement factor α in semiconductor injection lasers

A simple model for the linewidth enhancement factor α and its frequency dependence in semiconductor lasers is presented. Calculations based on this model are in reasonable agreement with experimental results.

A new infrared detector using electron emission from multiple quantum wells

A new type of infrared photodetector using free electron absorption in a heavily doped GaAs/GaAlAs quantum well structure has been demonstrated. Preliminary results indicate a strong response in the near infrared with a responsivity conservatively estimated at 200 A/W. The structure can potentially be tailored during fabrication for use in several infrared bands of interest, including the 3 to 5 micron band and the 8 to 10 micron band.

Noise equivalent circuit of a semiconductor laser diode

The noise equivalent circuit of a semiconductor laser diode is derived from the rate equations including Langevin noise sources. This equivalent circuit allows a straightforward calculation of the noise and modulation characteristics of a laser diode combined with electronic components. The intrinsic junction voltage noise spectrum and the light intensity fluctuation of a current driven laser diode are calculated as a function of bias current and frequency.

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.

Diffraction coupled phase‐locked semiconductor laser array

A new monolithic, diffraction coupled phase‐locked semiconductor laser array has been fabricated. Stable narrow far‐field patterns (∼3°) and peak power levels of 1 W have been obtained for 100‐μm‐wide devices with threshold currents as low as 250 mA. Such devices may be useful in applications where high power levels and stable radiation patterns are needed.

High quality molecular beam epitaxial growth on patterned GaAs substrates

In this letter we describe a procedure for high quality molecular beam epitaxy (MBE) growth over finely patterned GaAs substrates which is suitable for device fabrication requiring lateral definition of small (∼1–2 μm) dimension. This method was used for the fabrication of index guided laser arrays. Yields of individual lasers exceeded 90%, and thresholds were uniform to 10%. Temperature and flux ratio dependence of faceting during MBE growth over patterned substrates is shown for temperatures ranging from 580 to 700 °C and for As/Ga flux ratios from 1.4:1 to 4:1. The real index guided structure, which can be formed by a single MBE growth over a ridged substrate, is discussed. This technique should prove useful in the fabrication of devices which take advantage of unique features formed during regrowth by MBE.

Chirped arrays of diode lasers for supermode control

We propose nonuniform structures of phase-locked diode lasers, which make it possible to discriminate efficiently against all the higher order array supermodes (lateral modes). In these nonuniform arrays, the effective mode index in each channel varies across the array. Consequently, the envelopes of the various supermodes, including the highest order one, differ significantly from each other. Thus, by proper tailoring of the gain distribution across the array, one can conveniently select the fundamental supermode. Such fundamental supermode oscillation is essential in order to obtain single lobe, diffraction limited beams and minimal spectral spread from phase-locked laser arrays.

AlGaAs lasers with micro-cleaved mirrors suitable for monolithic integration

A technique has been developed for cleaving the mirrors of AlGaAs lasers without cleaving the substrate. Micro‐cleaving involves cleaving a suspended heterostructure cantilever by ultrasonic vibrations. Lasers with microcleaved mirrors have threshold currents and quantum efficiencies identical to those of similar devices with conventionally cleaved mirrors.

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.

Monolithic integration of an injection laser and a metal semiconductor field effect transistor

A new laser structure, the ’’T‐laser’’, has been monolithically integrated with a MESFET on a semi‐insulating GaAs substrate. Integration is achieved by means of a compatible structure in which the optically active layer of the laser also serves as the electrically active layer of the MESFET. Direct modulation of the laser by means of the transistor is demonstrated.