Semiconductor laser arrays with enhanced mode stability
TL;DR: In this article, a semiconductor laser array with a highly uniform intensity distribution for the fundamental mode can be constructed, which is desirable for improved modal stability at high power levels because the effect of spatial hole burning is strongly reduced.
Abstract: An analysis is presented which shows how a semiconductor laser array with a highly uniform intensity distribution for the fundamental mode can be constructed. The high uniformity is desirable for improved modal stability at high-power levels because the effect of spatial hole burning is strongly reduced.
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TL;DR: In this article, a numerical model for calculating the emission characteristics of diode laser arrays and broad-area devices operating well above threshold is discussed, which uses the beam propagation technique for determining the field intensities for several lateral modes, while simultaneously and self-consistently solving for the two-dimensional current flow through the laser structure and subsequent carrier diffusion in the active region.
Abstract: A numerical model for calculating the emission characteristics of diode laser arrays and broad-area devices operating well above threshold is discussed. This model uses the beam propagation technique for determining the field intensities for several lateral modes, while simultaneously and self-consistently solving for the two-dimensional current flow through the laser structure and the subsequent carrier diffusion in the active region. The active-region temperature distribution is also computed in a self-consistent manner, based on the flow of heat generated in the active region through the layered device structure to a constant-temperature heat sink. The model is applied by investigating the sensitivity of the lasing modes of a broad-area diode laser to variations in the lateral temperature distribution. >
73 citations
TL;DR: In this paper, a two-dimensional arrays of 3*3 vertical cavity surface emitting GaAs-AlGaAs lasers with 7- mu m center spacing are described, which are grown by molecular beam epitaxy and contain one grown GaAsAlAs mirror under the active layer and another, thermally deposited, high-reflectivity, SiO/sub 2/Si mirror on top of the epitaxial layer.
Abstract: Two-dimensional arrays of 3*3 vertical cavity surface emitting GaAs-AlGaAs lasers with 7- mu m center spacing are described. The lasers were grown by molecular beam epitaxy and contain one grown GaAs-AlAs mirror under the active layer and a second, thermally deposited, high-reflectivity, SiO/sub 2/-Si mirror on top of the epitaxial layer. The array has a 295-K threshold of 90 mA, corresponding to 10 mA per laser. The individual lasers in the array have Gaussian beam profiles both spatially in the near field and angularly in the far field. When all the lasers in the array are operating in a coupled manner, the emission exhibits a lobed far-field pattern with a 5 degrees separation in the direction parallel to the contact edge and a 2.5 degrees separation perpendicular to the contact edge. >
47 citations
TL;DR: In this paper, a review of the main results obtained in the last few years in the course of development and studies of integrated injection laser arrays is given, where the main configurations of such arrays are considered: they differ in respect of the structure of the active elements and methods used to couple the elements optically.
Abstract: A review is given of the main results obtained in the last few years in the course of development and studies of integrated injection laser arrays. The main configurations of such arrays are considered: they differ in respect of the structure of the active elements and methods used to couple the elements optically. The main approaches to calculations of the mode compositions of the output radiation are described. The experimental energy, spectral, spatial, and dynamic parameters of laser arrays are reported to illustrate the attained levels of their technical characteristics. An analysis is made of phase locking of the radiation from laser arrays by injecting an external phase-locking optical signal, and also by using a shared external resonator, spectral–spatial selectors, and other external optical components.
20 citations
TL;DR: In this paper, an approximated coupled-mode solution to the problem of lateral mode behavior in twin-stripe index-guided injection lasers near threshold is presented, where the optical properties are determined by the coupling coefficients between the two waveguides, taking into account the external currentdependent perturbation to the dielectric constant.
Abstract: An approximated coupled-mode solution to the problem of lateral mode behavior in twin-stripe index-guided injection lasers near threshold is presented. The optical properties are determined by the coupling coefficients between the two waveguides, taking into account the external current-dependent perturbation to the dielectric constant. In the calculations of the external perturbation, a simple model of current spreading under the contacts and carrier diffusion in the active layer is given for a multistripe structure. Emphasis is on the influence of the current ratio on the lateral field shape and modal gain. It is shown that for symmetrical current injection, the fundamental supermode has a slight advantage (higher gain) over the second 180 degrees phase-shifted mode. As the injected current ratio is driven away from the symmetrical point, the second supermode is favored with increasing modal gain difference. The coupled-mode approach is relatively simple and can describe rather accurately this already-known behavior. >
14 citations
TL;DR: In this article, a numerical analysis of transient turn-on in a gain-guided semiconductor laser array is presented, valid in the strong-coupling limit, treating the array as a single waveguide laser with a transversely varying refractive index.
Abstract: A numerical analysis of transient turn-on in a gain-guided semiconductor laser array is presented. The self-consistent approach, valid in the strong-coupling limit, treats the array as a single waveguide laser with a transversely varying refractive index. The program first solves for the modes of this system without considering stimulated emission. The overall modal gain is then inserted into the rate equations in order to calculate a photon density; this results in a new spatial gain distribution, which in turn causes changes to the modal intensity profiles. This analysis is used to find both steady-state results and instabilities which result from mode competition. The approach is to solve instantaneous eigenvalue equations. >
11 citations
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TL;DR: In this paper, a coupled mode formulation for parallel dielectric waveguides is described, and the results apply to any guided modes (TE, TM, or hybrid) in waveguide of arbitrary cross-section, dissimilar index, and non-identical shape.
Abstract: A new coupled mode formulation for parallel dielectric waveguides is described. The results apply to any guided modes (TE, TM, or hybrid) in waveguides of arbitrary cross-section, dissimilar index, and nonidentical shape. Additional index perturbations not included within the waveguides are encompassed by the theory. Propagation constants and mode patterns for the coupled modes computed according to this theory are shown to agree very well with numerical solutions for the system modes when the latter can be determined. Moreover, the new results are more accurate than those obtained from prior coupled mode formulations. It is shown that even for Iossless guides the coupling coefficients from waveguide "b" to "a" and from "a" to "b," described by k ab and k ba respectively, are not related by their complex conjugates if the guides are not identical.
435 citations
TL;DR: It is shown that the broadening in the far-field beam divergence, as well as the broadens of each of the longitudinal modes that were observed in phase-locked arrays, may arise from the excitation of an increasing number of supermodes at increasing pumping levels.
Abstract: The optical characteristics of phase-locked semiconductor laser arrays are formulated in terms of the array supermodes, which are the eigenmodes of the composite-array waveguide, by using coupled-mode theory. These supermodes are employed to calculate the near fields, the far fields, and the difference in the longitudinal-mode oscillation wavelengths of the array. It is shown that the broadening in the far-field beam divergence, as well as the broadening of each of the longitudinal modes that were observed in phase-locked arrays, may arise from the excitation of an increasing number of supermodes at increasing pumping levels.
404 citations
TL;DR: In this article, a coupledmode analysis has been developed to describe the output of phase-locked injection laser arrays, showing that an array of emitters with weak coupling can only operate in a set of discrete modes determined by the number and the spacing of the emitters.
Abstract: A coupled‐mode analysis has been developed to describe the output of phase‐locked injection laser arrays. We show that an array of emitters with weak coupling can only operate in a set of discrete modes determined by the number and the spacing of the emitters. The interaction between emitters leads to a splitting of the common frequency of operation that can be estimated from the coupling strength. The coupled‐mode analysis is compared to calculations based on simple diffraction theory. A consequence of the analysis is an explanation for the commonly observed discrepancy between experimentally observed far‐field lobe(s) widths and those predicted by simple diffraction theory.
277 citations
TL;DR: In this paper, an improved coupled-mode equation for parallel dielectric waveguides was derived by using a newly found relationship that connects the propagation constants of the individual guides to the coupling coefficients via an overlap integral that measures the guides' proximity.
Abstract: An improved version of coupled-mode equations for parallel dielectric waveguides has been derived by using a newly found relationship that connects the propagation constants of the individual guides to the coupling coefficients via an overlap integral that measures the guides' proximity. The four parameters of these new coupled equations are simple functions of essentially one single quantity: the asynchronism of the individual guides properly normalized.
254 citations
TL;DR: A phase-locked multiple-quantum-well (GaAl) injection laser with a highly reflective rear facet coating and a low reflective front facet coating is reported to emit 2.6 W CW at room temperature from the front facet as mentioned in this paper.
Abstract: A phase-locked multiple-quantum-well (GaAl)As injection laser with a highly reflective rear facet coating and a low reflective front facet coating is reported to emit 2.6 W CW at room temperature from the front facet.
169 citations