The paper addresses the current status of 850nm VCSELs in data communications systems, and the outlook for adoption of VCSELs in other applications. In particular, recent experimental results obtained by research and development activities at Honeywell are discussed.

The reliability of oxidized VCSEL has similar result to implanted VCSEL. This paper presents our work on reliability data of oxidized VCSEL device and also the comparison with implanted VCSEL. The MTTF of oxidized VCSEL is 2.73 x 10⁶ hrs at 55°C, 6 mA and failure rate ~ 1 FITs for the first 2 years operation. The reliability data of oxidized VCSEL includes activation energy, MTTF (mean-time-to failure), failure rate prediction, and 85°C / 85% humidity test will be presented below. Commercialization of oxidized VCSEL is demonstrated such as VCSEL structure, manufacturing facility, and packaging. A cost effective approach is key to its success in applications such as Datacomm.

We have developed novel electrically pumped, surface-emitting lasers emitting at 980 nm with an extended coupled cavity. The concept is scalable from monolithic low power (~10 mW) devices all the way to high power extended cavity lasers. The latter have demonstrated ~1 W cw multi-mode and 0.5 W cw in a TEM00 mode and a single frequency, with 90% coupling efficiency into a single-mode fiber. By inserting a nonlinear optical medium in the external cavity, efficient and compact frequency doubling has been achieved with CW output powers 5-40 mW demonstrated at 490 nm. The latter devices are especially noteworthy due to their very low noise (0.05% rms from dc-2 MHz), sub 10 mrad beam pointing stability combined with small size, low power consumption (<10 W) and high efficiency.

Surface-micromachined 1.55μm vertical-resonator-based devices, capable of wide, continuous, monotonic and kink-free tuning are designed, technologically implemented and characterized. Tuning is achieved by mechanically actuating one or several membranes in a vertical resonator including two ultra-highly reflective DBR mirrors. The tuning is controlled by a single parameter (actuation voltage). The two different layers composing the mirrors reveal a very strong refractive index contrast. Filters including InP/air-gap DBR's (3.5 periods) using GaInAs sacrificial layers reveal a continuous tuning of >9% of the absolute wavelength. Varying a reverse voltage (U=0 .. -3.2V) between the membranes, a tuning range up to 142nm was obtained by electrostatic actuation. The correlation of the wavelength and the applied voltage is accurately reproducible without any hysteresis. Appropriate miniaturization is shown to increase the mechanical stability and the effectiveness of spectral tuning by electrostatic actuation since the relative significance of the fundamental physical forces can be varied considerably by appropriate scaling. Model calculations are performed for symmetric and asymmetric optical filter structures, varying layer thickness and compositions. Finally the filter results are used to design micromachined tunable air-gap VCSEL´s. Theoretical model calculations demonstrate very wide spectral tuning by micromachined actuation of air-gap VCSEL resonators.

Vertical Cavity Surface Emitting Lasers (VCSELs) have been widely adopted in the 850nm data communications markets with great success. Using this technology as a basis, we have developed a 1.3 μm InGaAsN VCSEL and VCSEL Array technology for telecommunications applications. Since the reliability requirement of this market is less than 150 FITs over 20 years, we focused a great deal of development time on the reliability of the device, and so far have been able to predict an MTTF of over 13 million hours or 71 FITs. This report provides a brief summary of the characteristics of the VCSEL in various stress conditions and the methodology used to measure both the wear-out and random failure rates of the devices.

Oxide VCSELs are the emitter of choice for high-speed optical communication applications. A low divergence circular beam, wafer-level testing and the capability to create dense two-dimensional arrays provide the VCSEL with unique advantages over edge emitting lasers, such that VSCELs have become a significant part of the optical communication market. An equally important metric for VCSELs is field reliability since significant failure rates are unacceptable for implementation of reliable networks. In order to better understand potential failure paths of VCSELs during field use, a variety of failures have been intentionally created on oxide VCSELs made from AlGaAs / GaAs materials operating at 850nm. Failures were created with epitaxial defects, scratches, surface contamination, thermal shock , ESD and elevated temperature and humidity (85C/85% humidity). We will present the results of these intentional failures, assess high-probability failure paths and compare and contrast the various failure mechanisms.

Significant advancements have been made in the characterization and understanding of the degradation behavior of the III-V semiconductor materials employed in Vertical Cavity Surface Emitting Laser (VCSEL) diodes. Briefly, for the first time a technique has been developed whereby it is possible to view the entire active region of a solid state laser in a Transmission Electron Microscope (TEM) using a novel Focussed Ion Beam (FIB) prepared plan-view sample geometry. This technique, in conjunction with TEM cross-section imaging has enabled a three-dimensional characterization of several of the degradation mechanisms that lead to laser failure. It is found that there may occur an initial drop in laser power output due to the development of cracks in the upper mirror layers. In later stages of degradation, dislocations are punched out at stress-concentrating sites (e.g. oxide aperture tips) and these dislocations can then extend over the active region in a manner consistent with recombination enhanced dislocation motion. Alternatively, complex three-dimensional dislocation arrays which exhibited dendritic-like growth and which cover the entire active region can nucleate on a single defect.

There is a wide variety of reasons why future high-performance datacom links are believed to rely on two-dimensional VCSEL arrays suitable for direct flip-chip hybridization. Some typical are as follows: highest interconnect density, high-frequency operation, self alignment for precise mounting, productivity at high number of channels per chip. In this paper the latest approaches to flip-chip VCSELs are presented. In particular we will asses the properties of transparent substrate VCSEL arrays which are soldered light-emitting side up as well as VCSEL arrays which are soldered light-emitting side down, e.g., onto a CMOS driver chip. The VCSEL arrays are designed for bottom- or top-emission at 850 nm emission wavelength and modulation speeds up to 10 Gbps per channel.

Lateral interactions due to fringe field overlap or "stray" reflections from optical elements in VCSEL array based interconnects are analyzed. Interacting cavity pairs act as coupled oscillators. The cavity that happens to switch on first, determined by the bit sequence between neighbors, acts as a master oscillator that affects the switch on jitter for the next cite. Earlier analytic results for the BER rate are extended to include the influence of the cavity coupling strength on the switch on jitter. Numerical examples, including pre-biasing cases, demonstrate the potential for a large degradation in BER rate at small coupling strengths. Extreme cases result into complete pulse suppression (bit skipping).

The integration of different components in optoelectronics modules, such as VCSEL and photodiode arrays, optical guides and electronics, introduces optoelectronical, thermal and mechanical interactions. In this context, a thermal and optoelectronic model of VCSEL array is proposed. The self and cross heating of VCSEL arrays have been simulated. The thermal behavior of VCSEL in the array can be modeled by an equivalent circuit model. A small signal electrical equivalent circuit is also presented. This model is obtained from the electrical effects in the component structure and the identification with the rate equations. The models have been validated with 850nm VCSEL arrays characterization.

Modal behavior of a 2-D (square lattice geometry) antiguided vertical cavity surface emitting laser (VCSEL) array was studied by 3-D bi-directional beam propagation method. Above threshold operation of leaky modes was simulated using multiple iterations. Besides, a method based on functions of Krylov’s subspace, was developed to find a number of array optical modes in a VCSEL array with gain and index distributions established by the oscillating mode. In calculations, both Fourier and space variable descriptions of beam propagation were combined. The FFT technique was used for calculations of the Fourier image and the original. Conditions are found for favorable lasing of the in-phase mode providing high laser beam quality. Experimentally realized 5x5 laser array was studied numerically. The 2-D antiguided array results from shifting the cavity resonance between the element and inter-element regions and is fabricated by selective chemical etching and two-step metalorganic chemical vapor deposition (MOCVD) growth. In-phase and out-of-phase array mode operation is observed from top-emitting rectangular arrays as large as 400 elements, depending on the inter-element width, in good agreement with theory.

The near-field emission profiles of oxide confined GaAs vertical cavity surface emitting lasers (VCSELs) with 20 m aperture have been investigated at different operating temperature and different driving current. The subthreshold emission profile provided the information of carrier distributions. At 20oC, a uniform plateau profile was observed at subthreshold emission, which then transferred to a fundamental mode at just above the threshold current. At higher driving current, the fundamental mode evolved into higher order modes due to the spatial hole burning effect. However, at 90oC the subthreshold emission was no longer a uniform plateau profile but showed some locally high gain regions off the aperture center. The subsequent lasing mode profiles showed high order mode in coincidence with these locally high gain regions at 90oC. The higher order mode profiles remained nearly unchanged under different temperature conditions when driving at constant current above the threshold. These locally high gain regions probably caused by the non-uniformity of the open aperture and the current crowding effect. In addition to the spatial hole burning and thermal lensing effect, these locally high gain regions appeared at elevated operation temperature also affected the higher order mode transitions of oxide confined VCSELs.

We report on in-depth experimental and theoretical studies of the polarization behavior and mode structure of Vertical-Cavity Surface-Emitting Lasers with an elliptical surface relief. The aim of the relief is twofold, first to enhance the single mode operation by introducing spatially distributed losses, and second, to enhance polarization stability by making these losses anisotropic, i.e. polarization dependent. We first identify the transverse mode structure for different dimensions of the relief ellipse as a function of the injection current. Then we proceed with a systematic measurement of the change in orientation of the two linearly polarized (LP) fundamental modes emitted by VCSELs and their frequency splitting as a function of an externally applied strain, anisotropic in the plane of the quantum wells. We investigate two orientations of the surface relief ellipse: longer sides along [110] and [-100] directions, respectively. These studies show that whereas the polarization direction is governed by the orientation of the index ellipsoid, the selection of the lasing LP mode is mainly determined by the anisotropy in the mirror losses introduced by the elliptical surface relief. We confirm these experimental studies by theoretically estimating the effect of the relief and the anisotropic strain on both the refractive index and the losses.

In this work we present performance characteristics of metalorganic vapor-plase epitaxy grown GaInNAs and InGaAs quantum-well (QW) vertical-cavity lasers (VCLs) for 1.3-μm applications. The InGaAs VCLs emit in a wavelength range from 1200 to somewhat above 1260 nm, while the GaInNAs VCLs operate from 1264 to 1303 nm. The InGaAs VCLs are based on highly strained InGaAs double QWs, with photoluminescence (PL) maximum around 1190 nm, and extensive negative gain-cavity detuning. As a consequence, these devices are strongly temperature sensitive and the minimum threshold current is found at very high temperature (~90-100°C). Both kind of VCLs work continuous-wave well above 100°C, and while the InGaAs VCLs reach slightly higher light output power, they show significantly larger threshold currents. In addition, the large device detuning also has profound effects on the high-frequency response. Nevertheless, for a 1260-nm device, 10 Gb/s transmission is demonstrated in a back-to-back configuration. We also show that by further optimization of the InGaAs QWs the PL peak wavelength can be extended to at least 1240 nm. The incorporation of such QWs in the present VCL structure should considerably improve the device performance, resulting in higher light output power, lower threshold current, and reduced temperature sensitivity with a shift of the minimum threshold current towards room temperature, thus approaching standard VCL tuning.

High speed fiber optic transceiver modules using parallel optics require that oxide-confined vertical-cavity surface-emitting lasers (VCSELs) be moisture resistant in non-hermetic environments. Conventional storage 85/85 (85°C and 85% relative humidity) testing without a bias does not adequately characterize oxide VCSEL’s moisture resistance. Oxide VCSELs do not fail or degrade significantly under such conditions. With a bias, however, we have found that moisture can cause failure modes not seen in dry reliability testing. Without proper device design and fabrication, these failure modes lead to high failure rates in oxide VCSELs. In this paper, we first discuss the failure mechanisms we have identified, including dense dislocation network growth, semiconductor cracking and aperture surface degradation, all in high humidity and high temperature under operating conditions. We then report the results of environmental reliability tests on Agilent’s oxide VCSELs developed for the parallel optics modules. The results from a large number of wafers produced over an extended period of time have shown consistent, robust environmental reliability.

In this paper we describe the processes and procedures that have been developed to ensure high reliability for Emcore’s 850 nm oxide confined GaAs VCSELs. Evidence from on-going accelerated life testing and other reliability studies that confirm that this process yields reliable products will be discussed. We will present data and analysis techniques used to determine the activation energy and acceleration factors for the dominant wear-out failure mechanisms for our devices as well as our estimated MTTF of greater than 2 million use hours. We conclude with a summary of internal verification and field return rate validation data.

Electrostatic Discharge (ESD) damage is considered to be the leading cause for IC field failures. With increasing integration densities, devices tend to become more and more sensitive to ESD events. This observation holds in particular true for 850nm VCSELs, as the quest for higher modulation frequencies calls for shrinking device dimensions and aperture sizes in particular. This publication is geared towards an understanding of the various factors that lead to ESD-related failures of oxide VCSELs. A broad variety of current VCSEL product lines at Agilent have been investigated in respect to their ESD resistance and related long-term reliability. Intentionally stressed devices have been characterized in terms of their electrical, optical and visual failure patterns as well as the medium time-to-failure. Cross-sectional and plan-view TEM have been employed to localize ESD damage and its propagation. For the first time, emission microscopy has been used to study the electroluminescence pattern of damaged VCSELs at very low currents. The paper will conclude by listing experimental signatures allowing for differentiation between ESD and other failure modes. Based upon these, effective screening methods are proposed.

We are discussing design issues and measurement results for a new type of VCSEL based small form factor low cost optical front end (OFE). The optical interface of the OFE is a duplex LC receptacle. Mechanical, optical and electrical design restrictions are considered. High speed VCSEL biasing, the driver-VCSEL interface, influence of misalignment on RF performance, general requirements for serial 10Gb/s transceivers are main topics. Measurements of transmitter and receiver eye diagrams including a commercially available driver are presented.

Development of vertical cavity surface emitting lasers (VCSELs) at 850nm-wavelength for high speed interconnection systems is disclosed. The device structure is designed for a given set of static and dynamic characteristics. Electrical resistance, thermal characteristic and lateral mode characteristic are carefully designed and realized by a well-controlled fabrication process. 10Gbps transmission through a 500m-long, high-bandwidth multimode fiber is successfully demonstrated. An overview of 850nm-VCSEL technologies including future prospect is also described.

We describe a novel blue-green laser platform, based on the intracavity frequency doubling of Novalux Extended Cavity Surface Emitting Lasers. We have demonstrated 5 to 40mW of single-ended, 488nm, single-longitudinal mode emission with beam quality M²<1.2. The optical quality of these lasers matches that of gas lasers; their compactness and efficiency exceed ion, DPSS, and OPSL platforms. These unique properties are designed to serve diverse instrumentation markets such as bio-medical, semiconductor inspection, reprographics, imaging, etc., and to enable new applications. We also present data on the reliability of this novel laser platform and its extensions to different wavelengths (in particular, 460nm and 532nm) and to next-generation, highly compact, monolithic intracavity-doubled lasers.

A fluidic cavity vertical-cavity surface-emitting laser (VCSEL) is presented for the detection of biological agents via introducing the analytic biofluid into the high finesse laser cavity. The optical properties of the fluid as modified by the biological cells they contain are sensed by monitoring the output optical intensity and wavelength of the laser. As a preliminary study, our first generation electrically pumped GaAs/AlGaAs based fluidic cavity VCSEL is described, with emphasis on the system design and techniques for the system construction. The device shows a strong spontaneous emission and a considerable wavelength shift when DI water is capillarily fed into the fluidic cavity.

The 2-dimensional photonic crystal (2-D PhC) structure has been investigated as a method of lateral mode control of vertical cavity surface emitting lasers (VCSELs). The 2-D PhC structures were designed using an equivalent index model developed for photonic crystal fibers combined with a plane wave expansion method. The etching depth dependence of the PhC effect was incorporated for the first time to design practical devices. 2-D PhC confied VCSELs with a 7-point defect structure are demonstrated to operate in single PhC confined mode.

In this paper we describe both the 1310 and 1550 nm VCSEL development work at Honeywell using both InP and GaAs substrates, and using both MOCVD and MBE. We describe the material systems, the designs, the growth techniques, and the promising results obtained and compare them to the needs of the communications industry. InGaAsN quantum well based VCSELs have been demonstrated to 1338 nm lasing at temperatures up to 90 C. Continuous wave InP based 1550 nm VCSELs have also been demonstrated.