F. Z. Hawrylo

Two-dimensional coherent laser arrays using grating surface emission

The concepts, fabrication, and operating characteristics of monolithic two-dimensional, coherent AlGaAs laser arrays are presented. The arrays consist of 100 (10*10) active elements fabricated from a single-quantum-well graded-index separate-confinement heterostructure laser geometry. A surface relief grating is used for feedback and outcoupling. The elements of the array are index-guided ridge lasers with evanescent or Y coupling in the lateral direction and injection coupling longitudinally. The far field emanating from a 60- mu m*5-mm aperture, measures 0.01 degrees *1 degrees . These arrays emit more than 1 W peak power into a 2-AA wavelength interval. By adjusting the drive current to the electrically independent gain sections of these arrays, the angular position of the far-field beam can be steered. >

Coherent, monolithic two-dimensional (10×10) laser arrays using grating surface emission

Two‐dimensional, coherent AlGaAs laser arrays consisting of 100 (10×10) active elements have been fabricated using single quantum well laser structures. A surface relief grating is used both for feedback and outcoupling. The elements of the array are index‐guided ridge lasers. In one array design, the elements are coupled laterally by evanescent field overlap while in the second design, the coupling is by Y branches. Longitudinal coherence is achieved by injection coupling. The far field, emanating from a 60 μm by 5 mm aperture, measures 0.01°×1°. Both types of arrays emit more than 1 W peak power. The mode spectrum of the emitted power is contained in a ∼2–3 A wavelength interval at ∼1 W.

Electronic beam steering in monolithic grating‐surface‐emitting diode laser arrays

Electronic beam steering has been demonstrated in both one‐ and two‐dimensional injection‐coupled grating‐surface‐emitting diode laser arrays. By appropriately varying the drive current to the electrically independent gain sections of an injection‐coupled grating‐surface‐emitting laser array, the angular position of the far‐field output can be steered. Experimental results for two‐dimensional surface‐emitting arrays are presented, as well as a theoretical model which shows that beam steering is a general property of injection‐coupled surface‐emitting arrays.

High‐power seven‐element grating surface emitting diode laser array with 0.012° far‐field angle

A coherent seven‐element grating surface emitting diode laser array with a predominant single‐lobe far‐field pattern having an angular divergence of 0.012° has been demonstrated. The extent of the emitting aperture was 4 mm, and the beam divergence was within 10% of the diffraction limit. Under pulsed operation the array had a peak output power of over 400 mW and a differential quantum efficiency of 15%.

Coherent, monolithic two-dimensional strained InGaAs/AlGaAs quantum well laser arrays using grating surface emission

Two‐dimensional coherent strained‐layer InGaAs/AlGaAs quantum well laser arrays consisting of 100 (10×10) active elements have been fabricated and characterized. The central lobe of the far field has a full width at half power of 0.04°×1°. Observation of about 2 W peak power from either the substrate or the junction surface, with differential quantum efficiencies from each side of about 40%, is reported. The mode spectrum of the emitted power is contained in a ∼2 A wavelength interval at ∼2 W.

Efficient, high-power (>150 mW) grating surface emitting lasers

Surface emitting AlGaAs second‐order distributed Bragg reflector lasers using a superlattice graded‐index separate confinement heterostructure with a single quantum well have been fabricated. The total peak power is emitted coherently from both gratings into a 0.06° full width half‐power single lobe far field pattern. Peak powers are in excess of 150 mW. The external differential quantum efficiency is as high as 30%. Under severe current modulation conditions, the stable single longitudinal mode had 20–45 dB wavelength side mode rejection.

Improving the performance of strained InGaAs/AlGaAs single quantum well lasers

By adjusting the carrier confining structure and the optical confining structure of strained InGaAs/AlGaAs single quantum well (QW) lasers, an improvement in performance has been obtained. First, the influence of optical confinement was examined by comparing two graded‐index confining structures. For InxGa1−xAs QWs with either x=0.20 or x=0.25, lasers with greater optical confinement factor had improved performance, with both lower threshold (180 A/cm2 for x=0.20) and higher characteristic temperature (250 K for x=0.20), despite their reduced carrier confining potentials. Second, experiments on graded‐composition quantum wells show that thin step‐grading layers result in improved performance. In this structure, where the QW has x=0.35, and the step layers have x=0.15, the optimum step thickness is 30–40 A. Thicker step layers appear to create too much strain, degrading the laser operation. These results indicate that step grading of strained QWs produces active region interfaces with lower defect density,...

Efficient 30 mW grating surface-emitting lasers

A surface‐emitting AlGaAs second‐order distributed Bragg reflector laser using a graded index separate confinement heterostructure with a single quantum well has been fabricated. The surface emitted power is in excess of 30 mW with an external differential quantum efficiency of 20%. These values approach the performance of present commercially available edge‐emitting diode lasers. Under severe current modulation conditions, the stable single longitudinal mode had nearly 30 dB wavelength sidemode rejection, and a near diffraction limited 0.51° full width half‐power beam divergence of the single‐lobe far‐field pattern.

Dynamically stable 0° phase mode operation of a grating-surface-emitting diode-laser array

A coherent grating-surface-emitting diode-laser array has demonstrated dynamically stable operation in the 0° phase mode. The array was operated under pulsed conditions, had a peak power output of 44 mW and a large central lobe on axis in the far field, and exhibited single-mode spectral output with better than 18-dB side-mode rejection.

Coherent two-dimensional surface-emitting arrays of strained InGaAs/AlGaAs quantum-well lasers

Summary form only given. An effort was made to fabricate and characterize monolithic, coherent two-dimensional arrays of grating surface emitting (GSE) lasers emitting in the 0.9-1.1- mu m wavelength region using strained InGaAs/AlGaAs quantum-well lasers. The two-dimensional arrays of GSE distributed Bragg reflector (DBR) lasers were grown on both GaAs and AlGaAs substrates by atmospheric pressure organometallic vapor-phase epitaxy, using a graded-index separate-confinement-heterostructure (GRINSCH) geometry with a single InGaAs strained quantum well. The emitting aperture of these arrays was 0.04 mm by 5.0 mm when a 10*10 section of the wafer was probe tested at 12 A. Typically, the full width half-power of the single-lobed longitudinal far field was about 0.02 degrees . The tested lasing wavelengths of the 10*10 arrays from different wafers ranged from 0.95 and 1.03 mu m. The device is a monolithic, coherent array and performs comparably to previously reported devices based on AlGaAs/GaAs. >