Diode lasers with InGaAs strained-layer quantum wells and GaInP cladding layers for operation at 980 nm have been investigated. Two types of device structure, differing in the optical-waveguide material have been grown by organometallic vapor phase epitaxy. Threshold current densities as low as 85 A/cm² and differential efficiencies as high as 93% have been measured on broad-area devices. Mass transport of GaInP and GaInAsP alloys has been used to fabricate buried-heterostructure lasers with threshold currents as low as 3 mA and output powers of 30 mW/facet for uncoated devices. Threshold currents of 7 mA and single spatial mode output power in excess of 50 mW/facet have been obtained for uncoated, ridge-waveguide lasers.

The OMVPE growth and performance of graded-index separate-confinement heterostructure strained quantum-well InGaAs-AlGaAs diode lasers are reviewed. Broad-stripe lasers have exhibited J_th as low as 60 A cm^-2 for a cavity length L equals 1500 micrometers and differential quantum efficiency (eta) _d as high as 90% for L equals 300 micrometers . Similar heterostructures have been used to fabricate traveling wave amplifiers with a laterally tapered gain region that emit over 1 W cw in a nearly diffraction-limited spatial lobe at 0.98 micrometers , linear arrays of 200-micrometers -long uncoated ridge-waveguide lasers with average threshold currents of 4 mA and (eta) _d approximately 90%, and high-power broad-stripe lasers with power conversion efficiency exceeding 50% at 75 degree(s)C.

We report on the growth of AlGaInP materials on GaAs substrates using solid, elemental phosphorus in a valved cracker source by molecular beam epitaxy (MBE). The two ternaries are found to be of comparable or better quality than material grown by other, more conventional techniques which use phosphine. The successful growth and doping of the quaternary is reported and recent work in the growth of GaInP quantum well (QW) lasers is discussed. Finally, the compatibility of the valved source in growing arsenide/phosphide heterojunctions is demonstrated.

High performance, AlGaInP, strained-layer single quantum well, semiconductor laser diodes emitting in the 630 to 680 nm spectral range have been designed, fabricated, and characterized. Thermal calculations and modelling have been carried out both to estimate the thermal resistivity of various AlGaInP alloys and to optimize the device geometry and performance. Threshold current densities below 300 A/cm² at room temperature, cw outputs over 1 Watt, and operating lifetimes in excess of 10,000 hours have been achieved.

Strained InGaAs/AlGaAs quantum well (QW) lasers operating at 0.98 micrometers are currently of great interest due to their suitability for pumping erbium-doped fiber amplifiers. They are reported to yield a lower noise figure and higher gain coefficient than the 1.48 micrometers InGaAs/InP pump lasers as well as 0.8 micrometers AlGaAs/GaAs pump lasers. In addition, the InGaAs/AlGaAs strained QW lasers have lower threshold current, higher slope efficiency, and less temperature dependance. All these factors contribute to lowering the power dissipation of the pump design. Recently Ga_0.51In_0.49P, lattice-matched to GaAs has been introduced as a substitute for the AlGaAs cladding layers due to reports suggesting its resistance to rapid degradation by dark line defect propagation and to catastrophic mirror damage. The aluminum-free system also lends itself more readily to device fabrication by selective etching and epitaxial regrowth or mass transport. We report on the first InGaAs/GaAs strained-layer QW lasers using GaInP cladding layers grown by chemical beam epitaxy. The laser structure is a separate confinement heterostructure (SCH) with the active region consisting of 70 angstroms thick In_0.2Ga_0.8As quantum well and 220 angstroms thick GaAs barriers. The active and the SCH region are cladded by Ga_0.51In_0.49P layers of 1.35 micrometers thickness. A very low broad-area threshold current density of 70 A/cm² was obtained for 1500 micrometers long single QW lasers which is among the lowest reported for InGaAs/GaAs/GaInP lasers. The J_th for two and three QW lasers were 135 A/cm² and 170 A/cm² respectively. Ridge waveguide lasers with 4 micrometers width have very low cw threshold currents: 7.8 mA for 500 micrometers -long cavity and 10 mA for 750 micrometers -long cavity. External differential quantum efficiency as high as 0.9 mW/mA was obtained for 250 micrometers -long lasers. From the slope of inverse quantum efficiency versus cavity length, a very low internal waveguide loss of 2.5 cm^-1 and an internal quantum efficiency of 0.95 are inferred.

The temperature engineered growth (TEG) technique for the single step fabrication of buried heterostructure lasers is reviewed. GaAs/AlGaAs quantum well lasers and strained InGaAs/GaAs quantum well lasers have been fabricated with threshold current of 2 mA and 3 mA for the GaAs and InGaAs systems, respectively. We show that the use of strained quantum wells resulted in better collection of carriers and higher external quantum efficiency (88%). The growth of strained InGaAs/GaAs lasers integrated with Bragg reflectors utilizing the TEG technique is shown to be a promising technique for obtaining low threshold current surface emitting lasers incorporating a folded cavity.

In this paper we will review the shadow masked growth technique and its applications. The technique enables us to change the layer thicknesses over a substrate by the variation in dimensions of windows in the shadow mask. One of the major application areas is the realization of photonic integrated circuits where materials with a different bandgap have to be integrated on the same substrate. The combination of thickness variations with the use of quantum wells results in the required bandgap changes. In the paper we will first start with an overview of the basic technology of shadow masked growth and in a second part we will discuss some of the important applications. Note that we will limit ourselves to the shadow masked growth technique and no review will be given on other technologies such as selective growth.

An analysis of transport and film growth over masked and nonplanar substrates is presented. Special emphasis is placed upon modelling strategies with regard to whether the gas is in the viscous or rarefied flow regimes and the appropriate assumptions which can be made to simplify the model. A coupled volume and surface diffusion model is used to describe selective and nonplanar growth in the viscous flow regime. Results of a parametric study suggest that diffusion in the gas phase is responsible for the growth rate enhancements and nonuniformity which accompany patterned substrate growth. The direct simulation Monte Carlo method is used to model rarefied gas flows and deposition over patterned substrates where the mean free path of the gas molecules is of the same order or larger than the characteristic feature size.

We report an integrated wavelength demultiplexing grating spectrometer and p-i-n array for use in dense wavelength division multiplexing (WDM) applications. The single InP chip incorporates a novel waveguide/detector coupling scheme and is capable of demultiplexing up to 92 wavelength channels. Operation in the 1.5 micrometers fiber band was successfully demonstrated with a channel spacing of 1 nm. The detectors exhibited bandwidths of 15 GHz.

The dynamic linewidth enhancement factor, (alpha) , and damping rate, (Gamma) , for distributed feedback (DFB) lasers are obtained at various bias levels by measuring the frequency modulation and amplitude modulation indices of the lasers simultaneously. The (alpha) -value of a DFB lasers is generally reduced with increasing output power except at low bias, and the (Gamma) -value typically increases with output power. The measured results show that ninety percent of the 1.3-micrometers capped-mesa buried heterostructure DFB lasers have (alpha) -values in the range 4 to 7 and (Gamma) -values below 4 X 10¹⁰ s^-1. The 1.3-micrometers lasers have smaller damping rates than the 1.5- micrometers lasers of the same DFB laser structure. Compared with buried heterostructure DFB lasers, multiquantum well (MQW) DFB lasers exhibit a much smaller (alpha) -value and a larger damping rate. For both unstrained and strained 1.5-micrometers MQW-DFB lasers, (alpha) -values as low as 1.5 can be easily realized for these lasers at high output power (>= 10 mW).

The fabrication and performance characteristics of InGaAs/GaAs strained quantum well lasers are described. Lasers with low threshold current, high output power and excellent reliability have been fabricated. In_0.2Ga_0.8As/GaAs lasers emitting near 1 micrometers are useful as pump sources for erbium doped optical fiber amplifiers.

A new self-consistent thermal electrical model of proton-implanted top-surface-emitting lasers is applied to study thermal properties of GaAs/AlGaAs/AlAs devices with the active-region diameter of 35 micrometers . The results show that intense heating occurs at pumping currents exceeding 4 times threshold. Minimization of electrical series resistance is shown to be very important for improving the device performance. However, due to p-side up mounting, calculated thermal resistance remains relatively large even when electrical series resistance is very small.

We report the fabrication and performance of InGaAs/InGaAsP multi-quantum well distributed-Bragg-reflector lasers grown by chemical beam epitaxy. By using a long and weak grating, which was made on a thin and uniformly grown quaternary layer, we have been able to well control the grating coupling constant, (kappa) . For most of the lasers the measured linewidths are below 10 MHz. A record high side mode suppression ratio of 58.5 dB was obtained.

Analytical expressions are derived for calculating electrical spreading resistance in vertical- cavity surface-emitting diode lasers. Three contact configurations are considered: annular, circular, and broad-area. Calculations performed for proton-implanted surface-emitting lasers demonstrate that low values of series resistance can be achieved by combining the broad-area or circular contact configuration with a sufficiently large active-region diameter.

As the speed of microelectronic circuits continues to increase, the propagation delay between the semiconductor chips on a conventional multilayer printed wiring board becomes a bottleneck for achieving higher system performance. One way to reduce the packaging delay is to package bare semiconductor dies on a multichip module (MCM). This approach has been successfully implemented on high performance mainframe and supercomputers. In the past several years, there have been many reports on advanced signal processor and fault tolerant computer modules using thin film metal/polyimide MCMs. However, there have been very few, if any, implementations on real avionics systems. In this talk, we will examined the reasons why MCM implementations have not taken off in avionics at present. In particular, we will discuss the relationship between cost and performance in MCM implementation. Performance requirements are defined in terms of wiring density, controlled impedance, high frequency operation, and reliability. Both the manufacturing cost and system cost will be examined. Finally, some future extension of the present MCM technology to optical and microwave applications will be discussed.

A dual back-illuminated photodetector for balanced coherent receivers applications is presented. The photodetectors have an InP/InGaAs/InP p-i-n structure. Several additional semiconductor layers have been added to fabricate the structure by selective wet etching. The material was grown by metalorganic vapor phase epitaxy (MOVPE) on a semiinsulating, Fe doped, InP substrate. The passivation and the insulation between contacts were obtained using polyimide. The contact structure is intended to connect the photodetector to the package by flip-chip. The measured photodetector capacitance was around 0.2 pF for a single photodetector (without series connection), the series resistance under 20 ohms, and the dark current under 10 nA.

Optical systems using WDM are of increasing interest for telecommunications transmission, switching, wavelength routing, and broadcast networks, where often an array of sources at different wavelengths is needed. Conventionally this is achieved with separately packaged sources and WDM multiplexers. However, a considerable reduction in system complexity, along with potential cost reductions, can be achieved by reducing the number of separately packaged components. In this paper we describe a high performance multiple wavelength laser transmitter that operates at four wavelengths spaced by 4 nm around 1550 nm, in the erbium fiber amplifier window. The transmitter package includes an array of four DFB lasers along with a miniature diffraction grating and hybrid micro-optics for efficient coupling into a single mode output fiber. An array of micro-lenses bonded directly to the front facet of the laser array reduces alignment tolerances and minimizes optical losses. The compact package (5 X 3.5 X 1.5 cm) also includes novel ECL-level compatible laser drive circuitry that allows each laser in the array to be controlled and modulated independently at bit rates up to 2.5 Gbit/s. A thermoelectric cooler and thermistor provide temperature stabilization of the laser array. Prototype components have demonstrated mean launched powers of greater than -4 dBm per channel and laser wavelengths within +/- 0.3 nm of target for all channels simultaneously. Wavelength crosstalk between lasers caused by thermal effects was measured at less than 0.1 nm.

Quantum fluctuations in a semiconductor laser produce noise both in the amplitude and in the phase of the output field. These noise sources have a significant effect in optical coherent systems. Measurements of the field spectrum and RIN spectrum of a DFB laser, at three different optical power levels, are fitted to the corresponding analytical curves. The shapes of the measured curves are closely matched by the analytical expressions and the fitting produced very similar values for the common parameters in the field and RIN expressions, providing a good validation for the theory. These analytical/experimental results show a non-lorentzian shape for the field spectrum, as opposed to the commonly used lorentzian shape. Using the more accurate laser models derived from our work, we were able to predict successfully by simulation, the experimental values obtained for the BER in a practical FSK system.

The sensitivity of PIN-FET-receivers can be improved if a matching network is used between the photodiode and the FET. Serial or parallel inductors as the simplest matching circuits are widely used in state-of-the-art receivers. This paper answers the question which performance can be achieved by an optimum infinite order matching network using only reactive (noise- free) passive elements. The highest signal-to-noise ratio at the output of an amplifier is achieved with noise matching at the input. It can be shown that for an FET noise matching is nearly equivalent to power matching. The fundamental works of Fano and Fielder on broadband power matching are applied to the matching problem between photodiode and FET. The result is a fundamental limitation on the transimpedance function for any matching network. The transimpedance function is defined as the ratio between the input voltage of the interior FET and the photocurrent. It can be concluded that a maximum bandwidth for a given transimpedance can be achieved if the transimpedance function is an ideal low-pass function. A trade-off between transimpedance and bandwidth is possible. In a numerical example, several novel low-pass structure matching networks were optimized with the result that the theoretical bound can almost be achieved. But even for high-order networks there is a ripple in the transimpedance function which cannot be reduced. It was found that networks with transmission lines show a performance always inferior to that of networks with lumped elements.

The Transmitter and Receiver modules are developed for half-duplex transmission system, i.e. a full-duplex on two optical fibers with a link length of up to 15 km. The associated electronic circuits are integrated in Silicium technology and mounted on an appropriate substrate in terms of performance, costing and packaging easiness. The laser transmitter and the receiver are connected to a few passive components and to the optical connector. The number of module inputs-outputs is low and the power consumption is less than 1 Watt for each module making it possible to seal a low cost plastic package.

Fabrication and characterization results of a novel 1.55 micrometers DFB laser which use a strained-layer multi-quantum-well active grating for mixed index/gain coupling are presented. High yield single-mode operations due to the gain-coupling effects have been obtained. Experimental results have been well interpreted and simulated by a transfer-matrix theory.