Compact, low-cost photonic integrated circuits (PICs) have long been a desire of systems engineers. Unfortunately, the majority of PICs in use today use regrown buried heterostructure waveguides to achieve low crosstalk at reasonable packing density. These regrown structures are very expensive and limit PIC applications to high performance niches. The alternative low- cost approach is to use etched-rib, or strip-loaded, waveguides. Strip-loaded waveguides are simple to manufacture but may have guided slab-modes carrying unwanted light between devices within the PIC. These slab modes can result in very high crosstalk or low device density. This paper addresses techniques for control of stray light in strip-loaded PICs. Methods include mesa isolation of waveguides and ion implantation outside the waveguide rib. In addition, some devices such as Mach-Zehnder interferometers and waveguide power combiners generate radiation and slab modes as a fundamental means of operation. Improved designs for both of these structures with proper removal of both radiated and slab-mode light and high contrast-ration operation will be covered.

The use of bound and leaky eigenmodes to describe propagation in radiatively leaky planar waveguides that incorporate material absorption or gain is discussed. A criterion for determining which of the bound and leaky modes should be included in this calculation is provided, as is an explicit means of determining the contribution of each modes. The strategy provided here reveals that for the case of absorptive devices, e.g., waveguide detector structures or absorptive filters, there exists a regime in which one must discard the contribution of a fundamental mode, in favor of an improper leaky mode if one wishes to accurately obtain results such as quantum efficiency and device throughput.

Investigations of phase distortions influence, caused by the electro-optical deflector, upon the signal level in the processing channel of optical storage device in read and write modes.

Monolithic integration of a rare-earth-ion-based active waveguide on the same wafer as its diode pump laser would permit compact packaging of the technology demonstrated in fiber lasers and amplifiers. This new monolithic technology would offer the potential for developing compact infrared and visible (up- conversion) lasers, amplifiers, and other photonic integrated circuit components. One approach that we are investigating for such monolithic integration uses a high concentration of one or more rare-earth ions incorporated into polysiloxane spin-on glasses that are solvent-cast onto III-V semiconductor wafers. This `fiber on chip' technology substitutes a relatively high- ion-concentration, short-length metal-ion spin-on glass (MISOG) waveguide for the low-ion-concentration, long-length fiber. Progress to date on developing MISOG waveguide materials and technology is discussed.

The (Gamma) -X scattering rate of electrons in type-II superlattices by optical-phonon emission is calculated. The tight binding method for electronic band structure and the dielectric continuum model for phonons are used. The relative strength of scattering due to different phonon modes is examined for varying superlattice dimensions. The scattering rate is highest when the energy separation between the (Gamma) and X levels is smallest, and decreases quickly as the separation increases. It is found that the strongest scattering rate is due to the emission of AlAs confined modes. Changing of parity with layer thickness and its effect on scattering are discussed.

We present theoretical results on light pulse propagation in inverted semiconductors and semiconductor laser diodes. The theory is based on the semiconductor Maxwell Bloch equations and includes incoherent phenomena due to charge-carrier scattering based on the solution of the appropriate Boltzman equation.

An experimental and theoretical study of carrier dynamics in quantum well optical amplifiers is presented. Experimentally, the dynamics is studied using a pump-and-probe technique employing ultrashort optical pulses. The theoretical model is based on semi-classical density matrix equations. The effects of spectral holeburning, carrier heating, carrier transport (diffusion), and carrier capture are considered. Characteristic temperature relaxation and carrier capture times due to carrier-phonon scattering are calculated based on a unified treatment.

A numerical model for computing the intensity of spontaneous emission due to radiative recombination in semiconductor layers has been developed and incorporated into a complete numerical device simulation package. The model was constructed using an approach commonly employed in describing the effects of photon recycling. Results of initial simulation of LED structures are presented, and applications of the technique are discussed.

Progress in technology CAD (TCAD) tools that span the range of IC circuit design, semiconductor device modeling, and material processing simulation is discussed. Special emphasis is given to the application in the optoelectronic devices and systems. Promising techniques for the mixed device/circuit simulation are presented, using UC Berkeley's SPICE and Stanford's PISCES programs. Results show the capability to optimize the circuit timing and impedances to match the internal physical effects and the resulting optical properties in AlGaAs based LEDs. 3D solid modeling, a new approach for interactive device design based on the mask layout information, is discussed. Automatic gridding to support a unified process/device modeling capability for GaAs structures using SUPREM-IV.GS is also introduced. Taken as a whole, the unification of these TCAD tools provides a powerful design approach for the world of the optoelectronic ICs (OEIC).

Rigorous techniques to treat electron transport in heterojunction and quantum well devices are described. A scattering matrix approach, which solves the space-dependent, steady-state Boltzmann equation is described along with a transition matrix approach to treat the time-dependent processes in quantum wells. Ultimately, these two techniques can be combined to provide a rigorous and comprehensive treatment of heterojunction and quantum well devices. The objective is to understand the role of heterostructures in semiclassical devices and to illuminate the merits and shortcomings of standard current transport theories of such structures.

Four-layer pnpn electrophotonic devices are studied to improve both the dc characteristics and transient switching performance. The performance and analysis of AlGaAs/GaAs pnpn electrophotonic devices are examined numerically against experimental results. Preliminary results are shown to be instrumental and essential in the design and analysis of four-layer AlGaAs/GaAs PNPN bistable optoelectronic devices. The simulation methods studied in this work are aimed at overcoming the limitations of existing simulators.

We model the electron transport in the base of the resonant tunneling light emitting transistor, which is a crucial parameter for this device since it determines the spatial distribution of the light output. It is shown that this transport is ruled by diffusion of electrons. Carrier diffusion profiles are determined in the case that the Einstein approximation is valid (a constant diffusion coefficient). In this case, the electron transport under the emitter can be exactly calculated yielding a confluent hypergeometric function as spatial distribution. Better solutions using a charge-dependent diffusion coefficient are indicated (the Stern approach both with and without a magnetic field). This charge-dependent diffusion coefficient is calculated using the quantum capacitance concept. This makes only a numerical solution for the transport equation possible.

We review some AT&T works on physics of semiconductor lasers, including a method for calculating the electronic states and optical properties of semiconductor quantum structures applicable to bulk, quantum wells, quantum wires, and quantum dot lasers. Two-dimensional numerical simulation of carrier transport in laser structures, which allows calculation of the efficiency of injected carrier consumption by the active region, and the dependence of the laser current on applied voltage are also discussed. Calculations of quantum efficiency and threshold current for bulk InGaAsP lasers are supported by the experimental data.

We discuss some of the methods for 2D self-consistent simulation of semiconductor quantum-well lasers. First, the electronic and optical parts are each treated separately, then the coupling of the two problems is addressed. We briefly discuss the evolution of self-consistent laser simulation up to its present level, and some of the electronic transport concerns are discussed in greater detail. Transport in bulk regions and at heterojunctions, and the coupling of classical and quantum regions are each presented separately. Then, we review the approaches to the solution of the eigenvalue problem for the optical field. Finally, to illustrate the issues involved in coupling electronic and optical solutions, we introduce a model laser structure in which the optical field is poorly confined in the lateral direction, and the different confinement mechanisms are discussed. We then present calculations showing how gain can contribute to the lateral confinement of the fundamental cavity mode.

Maintaining cladding-layer material composition uniformity is inherently difficult during high temperature MBE growth of GaAs/AlGaAs laser structures. These nonuniformities can lead to asymmetrical waveguiding structures with distorted optical output characteristics of the laser. Distortions in optical characteristics can greatly affect the alignment and the coupling efficiency between laser diodes and optical fiber or other electro-optical systems in integrated optoelectronic applications. A 2D dielectric waveguide simulator has been used to analyze the optical properties of GRINSCH GaAs/AlGaAs lasers with asymmetrical cladding structures. Through this analysis, we have demonstrated an optimal laser device structure which as the desired optical characteristics and is less sensitive to cladding composition asymmetries arising in typical growth conditions.

We describe a 2D model for quantum-well lasers that solves self- consistently the electrical and optical equations. The model includes a wavelength- and position-dependent gain function that is derived from a quantum-mechanical calculation. We have also incorporated the effects of strain into the model, through an anisotropic parabolic band approximation of the band structure from a Luttinger-Kohn k.p theory. With this model we are able to predict the lasing characteristics such as the light-current behavior, current and optical field distributions, as well as the optical gain, spontaneous emission rate and dependence of the characteristics on geometry and layer design. Examples of the utility of our approach are shown which, for instance, clearly show the benefit of strain to laser design.

To simulate vertical cavity surface emitting lasers (VCSELs), we are developing a 3D, time-dependent field-gain model with absorption in bulk dielectric regions and gain in quantum-well regions. Since the laser linewidth is narrow, the bulk absorption coefficient is assumed to be independent of frequency with a value determined by the material and the lattice temperature. In contrast, the frequency-dependent gain regions must be solved consistently in the time domain. Treatment of frequency-dependent media in a finite-difference time-domain code is computationally intensive. However, because the volume of the quantum-well regions is small relative to the volume of the multilayer dielectric (MLD) mirror regions, the computational overhead is reasonable. A key issue is the calculation of the fields in the MLD mirror regions. Although computationally intensive, good agreement has been obtained between simulation results and matrix equation solutions for the reflection coefficient, transmission coefficient, and bandwidth of MLD mirrors. We discuss the development and testing of the 2D field-gain model. This field- gain model will be integrated with a carrier transport model to form the self-consistent laser code, VCSEL.

Low threshold strained-layer InGaAs/GaAs single quantum well (SQW) lasers are studied experimentally and analyzed on the basis of a computer model for the ridge-waveguide structure. The transition from the index guiding to the gain guiding is occurring with power anomalies provided by the antiguiding contribution of excess carriers. The mode gain is found to have a maximum attainable in the index-guided mode and a negative slope range in the dependence on the carrier concentration. If the operation point reaches the gain maximum the laser action can be ceased in the index-guided mode with power drop to the spontaneous level (lasing collapse) or to lower level of an antiguided mode. Mechanisms of the mode gain decrease are considered caused by a breakdown of the lateral index guiding and by an internal coupling of modes inside the diode chip, particularly of laser mode to cap layer mode. Latter has resonances at a phase synchronism of both modes accompanied a strong drop of the mode gain.

Carrier transport significantly affects the high-speed dynamics of quantum-well lasers. Adverse transport properties lead to severe low frequency rolloff in the modulation response and also lead to a reduction in the dynamic differential gain of the lasers. The same transport properties also adversely affect the wavelength chirp in these lasers. As in the case of device optimization for high-speed operation, one has to minimize the transport time across the optical and current confinement regions and maximize the escape time out of the quantum-well active region, to minimize wavelength chirp.

Large signal analysis of dual modulation of semiconductor lasers (by a simultaneous high-frequency control of the pumping current I and an additional intrinsic parameter) shows that the method allows suppressing the relaxation oscillations for an arbitrary shape of the pumping current signal I(t). Because of that, the rate of information coding can be enhanced to about 80 Gbit/sec. Moreover, we demonstrate that dual modulation allows us to maintain a linear relationship between I(t) and the output optical power in a wide frequency band.

In this work we present a study of the nonlinear behavior of semiconductor laser diodes by using mainly circuit model analysis. By numerical integration and by equivalent circuit modeling of the laser rate equations we have studied the dynamics of a semiconductor laser under strong sinusoidal modulation. The circuit model approach allows also to study the influence of parasitic effects in the pulsed modulation response of the laser. We demonstrate the importance of considering the parasitic effect and the restriction imposed by the bandwidth of the equivalent parasitic circuit in the treatment and the observation of the nonlinear behavior of semiconductor lasers.

This paper proposes an accurate computer model of the nonuniform FM response of semiconductor lasers, to be used in the computer- aided design of coherent optical communication systems. The model is communications engineer oriented and does not involve the physical insight of the device. The main idea of this approach is that the FM response of the laser can be approximated by a recursive digital filter based directly on measurements of the FM response. The procedure is divided into two steps: First, measurements of the FM response are fitted by a rational interpolant using the theory of multi-point Pade approximants. Then, the impulse invariant transformation is used to calculate digital filter coefficients. The procedure is applied in the case of a conventional single-electrode distributed-feedback laser. The calculated digital filter is used to study the influence of the nonuniform FM response on the performance of a coherent heterodyne CPFSK system with differential receiver operating at 1 Gb/s. The sensitivity penalty is given as a function of SNR, phase noise, and sequence length by a semianalytical technique. Theoretical and experimental results are in excellent agreement.

Nonlinear optical properties of lattice-matched and strained semiconductor quantum wells are computed using generalized optical Bloch equations. The equations combine the influence of many-body, strain and bandcoupling effects, within a consistent model for quasi-static screening that includes contributions from all occupied subbands in a single-plasmon-pole type approximation. Numerical solutions for the absorption and refractive index change of InGaAs-AlGaAs systems are presented in the quasi-equilibrium regime for a broad range of excitation conditions, from the low density excitonic regime to the highly excited gain region. Good agreement with recent experimental results is found.

In this report, we summarize our recent theoretical analysis of the electroabsorption and electrorefraction in Mach-Zender interferometric III-V semiconductor modulators.

We present an electrical pump optical probe experiment to investigate the temporal and spectral gain dynamics of an actively modelocked diode laser. The temporal behavior of the gain is studied with picosecond time resolution by measuring the transmission of a modelocked Ti:sapphire laser synchronized to the semiconductor laser through the active region of the diode. Our results show that the gain transients exhibit a strong temporal asymmetry which leads to incomplete modelocking.

A comprehensive microscopic theory that includes bandgap renormalization, plasma screening and interband Coulomb effects is used to calculate the gain and carrier-induced refractive index in an active semiconductor medium. This paper describes the effects of these many-body interactions on bulk and quantum well structures.

In semiconductor lasers, hot carriers are injected into the active region of the device, and their thermalization is essential for the laser performance. In this work, carrier thermalization is studied for quantum well, wire and dot laser stuctures. Low threshold considerations dictate the transition from bulk to quantum well to quantum wire to quantum dot systems. However, we find that carrier thermalization times increase as the dimensionality of the structures is reduced. The equilibration times are approximately equals 1 ps in bulk, approximately equals 10 ps in quantum wells, approximately equals 30 ps in quantum wires and approximately equals 100 ps in quantum dots. The increase of the thermalization times is responsible for serious limitations of the high-speed response of the quantum-confined laser structures. The implications of the slow carrier thermalization are discussed.

In this work we present the dynamic behavior of a two laterally coupled semiconductor lasers using numerical integration and circuit modeling of the array rate equations. We have obtained the same dynamic behavior when the system becomes stable. In this situation we can validate the conditions of the circuit model of such a device developed by the authors. By comparing the results obtained from direct numerical integration of the rate equation for the photon and carrier densities and the circuit response through a SPICE base program we have obtained the same bandwidth with both methods. The results show as well that the system presents unstable behavior for definite regimes of operation with agreement of both methods of analysis.

Optical feedback from an external cavity containing an element of dispersive loss was used to reduce the amplitude noise of a semiconductor laser. At feedback levels of P_fb/P_out approximately equals 10+-2), a maximum amplitude noise reduction of 16 decibel was measured close to threshold but the potiential for reduction was reduced considerably at higher injection currents as the laser noise approached the shot noise limit. In addition, the threshold current decreased and the linewidth was reduced to 10 kilohertz. The relaxation oscillation peak in the amplitude noise spectrum was also found to be dramatically suppressed and we find evidence that the relaxation resonance can be moved to much higher frequencies using optical feedback techniques.

The theory of feedback into a diode laser by an externally located reflector is developed for the case of arbitrary feedback strength. Assuming typical values for laser diode parameters, it is predicted that by employing a nearby (13.5mm) external partially transmitting mirror, line narrowing by a factor of at least 2000 is possible without increasing the threshold gain of the laser, while maintaining dynamical stability of the output and flattening the modulation transfer function up to about 8 GHz.

We describe a single-photon turnstile device that is based on a double-barrier mesoscopic p-i-n heterojunction driven by an alternating voltage source. In such a semiconductor device, Coulomb blockade and quantum confinement effects together can suppress the quantum fluctuations usually associated with electron and hole injection processes. It is therefore possible to generate heralded single-photon states without the need for high-impedance current source. The present scheme promises high- precision photon-flux state and current standards, as the repetition rate of the single-photon states and the magnitude of the junction current are determined by the frequency of the alternating voltage source.

New kinds of semiconductor microcavity lasers are being created by modern semiconductor technologies like molecular beam epitaxy and electron beam lithography. These new microcavities exploit 3D architectures possible with epitaxial layering and surface patterning. The physical properties of these microcavities are intimately related to the geometry imposed on the semiconductor materials. Among these microcavities are surface-emitting structures that have many useful properties for commercial purposes. This paper reviews the basic physics of these microstructured lasers.

This paper describes a noise theory for semiconductor microlasers which combines a microscopic description of the semiconductor medium and also macroscopic field propagation effects. Such a model is particularly apt for gain-guided systems whose noise properties can show significant deviations from sipmle plane-wave models.

The recent development of vertical-cavity surface-emitting lasers or whispering-gallery mode microdisk lasers opens the possibility of altering the photon density of states and the spontaneous carrier lifetime of the active medium. In this paper we investigate the corresponding changes of the stationary and dynamical emission properties of these microcavity lasers. We present a quantum mechanical theory for the coupled photon- carrier system in a semiconductor microcavity which includes the relevant nonequilibrium and many-body effects in the carrier system and mode confinement effects in the photon system. The theory considers the spectral interplay of stimulated and spontaneous emission and the cavity loss according to a kinetic equation for the spectral laser intensity. The nonequilibrium dynamics of the carrier system is discussed in terms of a Boltzmann equation which includes carrier-photon, carrier-carrier and carrier-phonon scattering.

A new comprehensive thermal-electrical self-consistent model of proton-implanted top-surface-emitting lasers is described. The model is applied to study thermal characteristics of GaAs/AlGa As/AlAs devices with the active-region diameter of 35 micrometers . Our results show that intense heating occurs at pumping currents exceeding 4X threshold. Long tails of radial temperature distribution will result in severe thermal crosstalk if integration of these devices into densely packed 2D arrays were to be attempted. Minimization of electrical series resistance is shown to be very important for improving the device performance.

We obtain numerical results for the injection current in the active region and the total series electrical resistance of proton-implanted top-surface-emitting lasers with top annular contact. We investigate the variation of the resistance and the current uniformity over a range of values of parameters such as the number of periods in the p-type top spreading region, the active region radius and the specific contact resistance. Approximate analytical expressions are also obtained for the injection current in the confinement region and the agreement between analytical and numerical results is investigated for varying active region radius values.

A circular cylinder resonator modal analysis is applied to vertical cavity surface emitting lasers to obtain a resonance mode chart to identify possible lasing spectra. For the first time a 2D/ (radial and azimuthal) calculation of the inversion population distribution in the device is done, inclusive of current spreading, carrier diffusion, (bimolecular) spontaneous recombination, and stimulated recombination to account for above- threshold operation. Analysis of corresponding modal gain competition is used to indicate possible lasing mode selection.

Issues relating to modeling the full spatiotemporal dynamics of wide aperture semiconductor lasers and amplifiers are discussed. Included in the discussion are the limitations of the usual beam propagation approach, characteristics of the many-body light- semiconductor material interaction, spurious nonphysical instabilities which mimic numerical grid oscillations and novel subpicosecond pulse reshaping and compression effects. An explicit simulation is presented for a flared amplifier structure and the results are compared with those using a linear gain model.

Data from regrown-lens-train lasers are used to validate a computer program for their simulation. Curves of light output as a function of current have been calculated and compare well with experimental data taken for three lasers with widely varying geometries. The optimum reflectivity of the front facet of a laser with a high-reflectivity back facet is calculated, and the output power is about the same as was obtained for the double- facet output of the experimental laser with uncoated facets. The power loss due to the finite width of the lenses is estimated.

A physical optics laser model based on a many-body semiclassical laser theory of the gain medium is used to investigate the gain medium effects on the modal stability of an unstable resonator semiconductor laser. Quantum confinement or strain are shown to result in single-mode operation over significantly wider ranges of unstable resonator configurations and gain medium excitation.

Power limitations are considered in semiconductor lasers of different configuration emitting a light beam which is not distorted by optical nonlinear processes. A simple approach is used to obtain estimations of the power threshold for the self- focusing in 1D and 2D geometry. It is shown that the multielement nonguided configuration may have advantage in the emission of the most powerful stable laser beam.

The role of boundary conditions for the correct formulation photoelasticity problems based on the restoration of tensor fields by means of optical tomography is presented in this article.

This paper reports the effects of third-order dispersion on the propagation of an optical soliton in an optical fiber: (1) the squeezing is nonuniform over the pulse, (2) a critical value of (beta) ₃, i.e., the third-order dispersion, governs the optimum range of squeezing as the soliton propagates along the fiber.

The energy spectrum is considered of ultrathin active layer with the quantum well (QW) depth modulation in one or two lateral directions. It is shown, that the modulation can produce more or less sharp spectral peaks in the density-of-state (DOS) distribution. This is a transient case between 2D and lower- dimensionality carrier gases, which may be treated also as cases of coupled quantum-wires (QWr) or coupled quantum boxes (QB). It is shown that the DOS may be modified to place its peak just at the band edge to provide its involvement in the working optical transitions and, due to it, such structures have more low- threshold carrier concentration and stabilization of the operation wavelength comparing with ordinary quantum well structures.

The properties and characteristics of asymmetric quantum-well heterojunction lasers having a set of active layers of different thickness and composition are described. The regimes of bistable switching and regular radiation pulsations are analyzed and optimal schemes of the laser structures are proposed.

The effect of nonlinear gain suppression to the higher order lateral modes is investigated using a self-consistent 2D strained quantum-well laser model. Both CW and transient simulation are performed at different ridge widths for a single quantum well InGaAs/AlGaAs ridge waveguide laser emitting at 0.98/micrometers . The simulation shows that the gain suppression significantly enhances the second order mode while reducing the fundamental mode. It also causes the L-I curve to become nonlinear. The nonlinear effect suppresses the ringing in both the first and second modes in the modulation response.