N. W. Carlson

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.

Characteristics of coherent two-dimensional grating surface emitting diode laser arrays during CW operation

Recent progress in the development of monolithic two-dimensional coherent grating surface emitting (GSE) laser arrays is presented. Such GSE arrays have operated continuously to more than 3 W/surface and pulsed to more than 30 W/surface. They have achieved continuous wave (CW) threshold current densities of under 140 A/cm/sup 2/ with CW differential quantum efficiencies of 20-46% per surface. Linewidths in the 40-100 MHz range were obtained with output powers of 100-300 mW per surface. The arrays typically consist of 10-30 mutually injection coupled gain sections with 10 laterally coupled ridge-guided lasers in each gain section. A single GaInAs strained-layer quantum well with a graded-index separate confinement heterostructure (GRINSCH) geometry allows junction down mounting with light emission through the transparent GaAs substrate. A surface relief grating is used for feedback and outcoupling. >

Mode discrimination in distributed feedback grating surface emitting lasers containing a buried second-order grating

The operating characteristics of a novel grating surface emitting laser structure containing a buried second-order grating have been studied both experimentally and theoretically. This device consists of a pumped distributed feedback (DFB) section that is terminated at each end by unpumped distributed Bragg reflector (DBR) sections. A single continuous second-order grating layer and waveguide layer extend throughout the active and passive sections so that there is essentially no fabricated optical discontinuity at the interface between the active and passive end sections. Single mode operation (>30 dB side mode suppression) and single-lobed far fields with negligible sidelobes are observed up to more than 5*I/sub th/ with spectral linewidths as narrow as 1 MHz. >

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.

A numerical investigation of wave interactions in dielectric waveguides with periodic surface corrugations

The modal properties of planar multilayered waveguides with a rectangular surface corrugation are investigated. A rigorous full Floquet numerical analysis is performed for the fundamental TE mode of the infinite periodic structure. The algorithm is based on a boundary element solution of the integral wave equation in the grating region. A generalized transverse resonance-type matrix equation is sought that matches all continuity, periodicity, and boundary conditions. The resonant solutions of this characteristic equation represent all the surface and leaky waves supported by the structure. The exact dispersion characteristics, as well as the amplitudes of the space harmonics are computed and discussed in connection with radiation losses and coupling mechanisms near resonant Bragg conditions. In particular, a specific double-heterostructure GaAs/AlGaAs waveguide geometry is examined in detail. >

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.

Demonstration of monolithic, grating-surface-emitting laser master oscillator-cascaded power amplifier array

The design, fabrication, and performance characteristics of a monolithic grating-surface-emitting master-oscillator-cascaded-power-amplifier laser array are reported. Light output from the amplifier chain was obtained using grating output couplers after each amplifier section. Power outputs of 80-100 mW per amplifier were measured, while the spectral purity of the master oscillator was maintained. The operating characteristics of these laser arrays demonstrate that the spectral characteristics determined by the laser oscillator and power control provided by the amplifier sections are independent.<<ETX>>

Phase‐locked operation of a grating‐surface‐emitting diode laser array

A linear array of surface‐emitting distributed Bragg reflector AlGaAs diode lasers has been demonstrated. The intensity pattern for five emitting elements had structure with an angular divergence as low as 0.05°, indicating phase locking between the elements of the array.