Jerome K. Butler

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.

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. >

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.

Radiation fields of GaAs-(AlGa)As injection lasers

Theoretical radiation patterns from a multilayer model of a dielectric waveguide are fitted to single mode experimental profiles of three symmetrical double-heterojunction cavities to test the adequacy of the model and study the effect of the dielectric parameters on the beam pattern. The radiation from the normal TE modes is approximated by plane waves, while for the TM modes it is given by boundary value solutions of the Maxwell equations. The adequacy of the theory is shown by the faithfulness of the fit out to large beam angles and low intensities, and the agreement of the adjusted cavity parameters to the experimental values. Small changes in either the cavity thickness or the dielectric constant of the internal n-type region have similar first order effects on the angular position of the minima in the profile as well as in the amplitude of the sidelobes. Depths of the minima decrease with departures of the structure from planarity. Pattern distortion from mode coupling at the interfaces and facets is not observed.

Refractive index of n‐type gallium arsenide

The index of refraction for n‐type GaAs is calculated as a function of photon energy by a method which accounts for the contribution of the fundamental absorption edge to the index of refraction. The absorption coefficient for n‐type GaAs near the band‐gap energy is determined from experimental data; free‐carrier absorption is not included in the calculations; however, its contribution to the index of refraction is estimated to have a negligible effect compared to that due to the fundamental edge. Some applications to single‐ and double‐heterojunction (AlGa)As–GaAs laser structures are discussed. The results indicate that occasionally the most important factor contributing to radiation confinement to the optical cavity in laser structures is the index‐of‐refraction change due to the differences in doping of various regions. Index calculations are made by using absorption data on GaAs at 77 and 300°K. The difference in the index of refraction of a material with different doping can be pronounced. For examp...

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. >

Theory of Transverse Cavity Mode Selection in Homojunction and Heterojunction Semiconductor Diode Lasers

A discussion of the transverse electromagnetic modes in single and double heterojunction lasers is presented. Three basic structures are analyzed: a laser with single heterojunction and optical cavity defined by the (p+‐p) heterojunction and p‐n junction; a double heterojunction laser with the second heterojunction at the p‐n junction; and another double heterojunction unit which can have a large range of optical cavities because the second heterojunction is in the n region spaced a controlled distance from the p‐n junction. Since the dielectric discontinuity at a heterojunction is an order of magnitude larger than at a p‐n junction, these double heterojunction lasers can have high‐order transverse modes. To model the observed radiation fields and, in particular, the preference for high‐order modes, the optical properties of the junction region are treated as a five‐layer dielectric slab. The two outer regions are bulk p+ and n+ (AlGa)As in the double heterojunction structures and p+(AlGa)As and n+ GaAs i...

Grating-assisted coupling of light between semiconductor and glass waveguides

Floquet-Bloch theory is used to calculate the electromagnetic fields in a leaky-mode grating-assisted directional coupler (LM-GADC) fabricated with semiconductor and glass materials. One waveguide is made from semiconductor materials (refractive index /spl ap/3.2) while the second is made from glass (refractive index /spl ap/1.45). The coupling of light between the two waveguides is assisted by a grating fabricated at the interface of the glass and semiconductor materials. Unlike typical GADC structures where power is exchanged between two waveguides using bound modes, this semiconductor/glass combination couples power between two waveguides using a bound mode (confined to the semiconductor) and a leaky mode (associated with the glass). The characteristics of the LM-GADC are discussed. Such LM-GADC couplers are expected to have numerous applications in areas such as laser-fiber coupling, photonic integrated circuits, and on-chip optical clock distribution. Analyses indicate that simple LM-GADCs can couple over 40% of the optical power from one waveguide to another in distances less than 1.25 mm.