Gary A. Evans

Design and characterization of 1.3-/spl mu/m AlGaInAs-InP multiple-quantum-well lasers

A comprehensive design method for long wavelength strained quantum-well lasers is applied to design uncooled multiple-quantum-well AlGaInAs-InP 1.3-/spl mu/m lasers for communication systems. The method includes multiband effective mass theory and electromagnetic waveguide theory. The resulting AlGaInAs-InP laser has a threshold current of 12.5 mA at 25/spl deg/C, with a slope efficiency of 0.43 W/A, at 77 K or greater characteristic temperature, a 38/spl deg/ perpendicular far-field beam divergence, and will operate at temperatures in excess of 100/spl deg/C.

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.

Surface‐emitting second order distributed Bragg reflector laser with dynamic wavelength stabilization and far‐field angle of 0.25°

Operation of a dynamically stabilized surface‐emitting AlGaAs channeled‐substrate‐planar large‐optical‐cavity distributed Bragg reflector laser with a 0.25°×8° far‐field pattern is reported. With 50% duty cycle and 50 ns–2 ms pulse length operation at room temperature, thresholds as low as 150 mA were obtained. No side modes were observed to 40 dB below the principal wavelength intensity under 100% modulation depth operation.

Surface Emitting Semiconductor Lasers and Arrays

Review of edge-emitting coherent laser arrays, S.R. Chinn vertical cavity surface emitting lasers and arrays, K. Iga and F. Koyama grating-coupled surface emitting semiconductor lasers, N.W. Carlson et al horizontal-cavity surface emitting lasers with integrated beam deflectors, Z.L. Liau et al second order grating surface emitting theory, A. Hardy et al network analysis of two-dimensional laser arrays, R. Amantea and N.W. Carlson external methods of phase locking and coherant beam addition of diode lasers, J. Leger coherence and its effect on laser arrays, M. Lurie microchannel heat sinks for two-dimensional diode laser arrays, J.N. Walpole and L.J. Missaggia.

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. >

Semiconductor laser insert with uniform illumination for use in photodynamic therapy

A low-cost semiconductor red laser light delivery system for esophagus cancer treatment is presented. The system is small enough for insertion into the patients body. Scattering elements with nanoscale particles are used to achieve uniform illumination. The scattering element optimization calculations, with Mie theory, provide scattering and absorption efficiency factors for scattering particles composed of various materials. The possibility of using randomly deformed spheres and composite particles instead of perfect spheres is analyzed using an extension to Mie theory. The measured radiation pattern from a prototype light delivery system fabricated using these design criteria shows reasonable agreement with the theoretically predicted pattern.

Analysis of grating-assisted directional couplers using the Floquet-Bloch theory

The Floquet-Bloch theory is used to develop a theory for grating-assisted directional couplers which predicts the coupled power and coupling lengths and is applicable to lossy waveguides. This theory views grating-assisted directional couplers as conceptually similar to conventional synchronous (nongrating) couplers. In the Floquet-Bloch analysis of the directional coupler, it is necessary to include both proper and improper space harmonics. The determination of which space harmonics are improper is critical to the understanding of the coupler performance. The choice of the improper space harmonics used for the analysis of the coupler is different from that used in contemporary papers.

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.