Robert A. Morgan

200/spl deg/C, 96-nm wavelength range, continuous-wave lasing from unbonded GaAs MOVPE-grown vertical cavity surface-emitting lasers

We report record temperature and wavelength range attained using MOVPE-grown AlGaAs vertical cavity surface-emitting lasers (VCSELs). Unbonded continuous-wave lasing is achieved at temperatures up to 200/spl deg/C from these top-emitting VCSELs and operation over a 96-nm wavelength regime near 850 nm is also achieved from the same nominal design. Temperature and wavelength insensitive operation is also demonstrated; threshold current is controlled to within a factor of 2 (2.5-5 mA) for a wavelength range exceeding 50 nm and to within /spl plusmn/30% (5-10 mA) for a temperature range of 190/spl deg/C at 870 nm.<<ETX>>

Vertical-cavity surface-emitting lasers come of age

This manuscript reviews our efforts in demonstrating state-of-the-art planar, batch-fabricable, high-performance vertical-cavity surface-emitting lasers (VCSELs). All performance requirements for short-haul data communication applications are clearly established. We concentrate on the flexibility of the established proton-implanted AlGaAs-based (emitting near 850 nm) technology platform, focusing on a standard device design. This structure is shown to meet or exceed performance and producibility requirements. These include > 99% device yield across 3-in-dia. metal-organic vapor phase epitaxy (MOVPE)-grown wafers and wavelength operation across a > 100-nm range. Recent progress in device performance [low threshold voltage (Vth equals 1.53 V); threshold current (Ith equals 0.68 mA); continuous wave (CW) power (Pcw equals 59 mW); maximum and minimum CW lasing temperature (T equals 200 degree(s)C, 10 K); and wall-plug efficiencies ((eta) wp equals 28%)] should enable great advances in VCSEL-based technologies. We also discuss the viability of VCSELs in cryogenic and avionic/military environments. Also reviewed is a novel technique, modifying this established platform, to engineer low-threshold, high-speed, single- mode VCSELs.

Hybrid dielectric/AlGaAs mirror spatially filtered vertical cavity top‐surface emitting laser

A novel AlGaAs/AlAs–TiO2/SiO2 hybrid distributed Bragg reflector is implemented in a planar vertical cavity (top)‐surface emitting laser (VCSEL) to control emission (near 850 nm) to a single TEM00‐like mode. This structure exhibits ≳30 dB side‐mode suppression ratio and constant divergence (or modal profile) throughout its operating range (i.e., the detrimental effects of thermal lensing inherent in implanted VCSELs are eliminated); moreover, a record low threshold voltage ≂1.6 V, (0.16 V above photon energy) is obtained, without sacrificing the producibility of the standard all‐epitaxial structure.

Vertical-cavity surface-emitting laser arrays

This paper reviews the state-of-the-art performance of producible, 850-nm, current-guided GaAs/AlGaAs, top-emitting vertical-cavity surface-emitting lasers (VCSELs) and arrays. We focus on the flexibility of this technology platform in demonstrating a variety of devices and arrays. This includes a 99.8% device yield across a 3-in-dia. Metal-Organic Vapor Phase Epitaxy (MOVPE)-grown wafer and wavelength operation across approximately equals 100-nm range. Recent progress in device performance (Vth equals 1.55 V; Ith equals 0.68 mA; Pcw equals 59 mW; Tcw equals 200 degree(s)C, (eta) wp equals 28%) have and will enable great advances in VCSEL-array-based technologies. Included are unique ways of engineering modal characteristics from single-mode to quasi-incoherent emission. Array applications include 1D addressable arrays, particularly in the area of high-speed optical data links. An example application is the 32-channel-wide Optoelectronic Technology Consortium parallel links that have been operated error-free up to 980 Mbit/s (Manchester coded) through 100 m of bier. Two-dimensional matrix-addressable VCSEL arrays for processing and imaging applications will also be reviewed. Finally, we will discuss the exploitation of this VCSEL technology to explore the use of patterned or phased arrays of VCSELs. Their performance and relevant physics will be described, including the recent demonstration of in-phase coupling, watt-level emission, and multi-transverse-element mode coupling.

Performance, uniformity, and yield of 850-nm VCSELs deposited by MOVPE

Vertical-cavity surface-emitting lasers (VCSELs) emitting near 850 nm and fabricated with the metal-organic vapor phase epitaxy (MOVPE) epitaxial growth technique and a planar proton implant process have been demonstrated with excellent performance, uniformity, and yield across a 3-in wafer. Four thousand lasers were tested on a three-inch-diameter wafer, with a yield of 99.8%. This translates into a yield of 94% for fully functional 34/spl times/1 arrays. The average threshold current, threshold voltage, and dynamic resistance at 10 mA operating current were 3.07 mA, 1.59 V, and 34 ohms, respectively. Uniformity of better than /spl plusmn/9% in threshold current, /spl plusmn/1% in threshold voltage, and /spl plusmn/1.5% in maximum optical output power across a 34-element array was demonstrated.

Reliability of proton-implanted VCSELs for data communications

We describe vertical cavity surface emitting laser (VCSEL) reliability tests comprising hundreds of parts and more than a million device hours. The VCSELs studied were of a previously described production design intended for local-area network data communication at 850 nm. Devices were operated at temperatures of 35, 80, 100, 125, and 150 degrees C and at currents of 5, 10, 15, 20, and 30 mA, and their operating characteristics were measured at room temperature. Additional groups were operated at 225 degrees C. Nominal operation is expected to be at 40 degrees C ambient and near 10mA; stresses due to temperatures and currents above the operating range accelerated degradation. The results support an Arrhenius- type failure-acceleration model with lognormal reliability distribution and lead to an 0.88-1.2- eV estimate for the failure activation energy. When tested at room temperature, typical VCSELs exhibited initial increases in power followed by decreases. The results were essentially independent of the package type (hermetic, unsealed, or overmolded plastic). Time- lapse video of degrading devices was employed in an effort to define the failure mode, which does not appear to be mediated by dark-line defects. Under normal operating conditions the observed VCSEL reliability is equal to, or better than, typical reliability results for other AlGaAs data communications lasers or LEDs.

Single-mode vertical cavity surface emitting laser by graded-index lens spatial filtering

4.5 mW of power in a single spatial mode has been obtained from a vertical cavity surface emitting laser (VCSEL) in an external cavity setup, using a graded index (GRIN) lens with a spatial filtering high reflecting aperture deposited on its endface. The spatial filter on the GRIN lens endface forces a larger single transverse mode in the VCSEL than is obtained without it. A brightness of 5.1×105u2009W/cm2 str is demonstrated, which is 91% of the maximum achievable.

Guided-mode grating resonant filters for VCSEL applications

A brief summary of both VCSEL technology and guided-mode grating resonant filters (GMGRFs) is presented. We then discuss benefits and issues of integrating the two technologies, emphasizing control of wavelength, polarization, and laser cavity modes. We present a GMGRF design suitable for a 980 nm InGaAs VCSEL and show that a significant loss (-4%) in reflectivity results from the slight loss associated with the minimum mirror conductivity required to inject current through the mirror. Experimental data are presented at 850 mm for gratings designed for and fabricated on fused silica substrates and illustrate that GMGRFs are also very sensitive to other forms of loss such as scatter caused by roughness in the grating lines. We suggest a hybrid approach of a GMGRF on a reduced distributed Bragg reflector stack as a means to circumvent the high sensitivity to loss in the GMGRF.

Recent progress in short-distance optical interconnects

Short distance optical interconnects are under development for a range of applications including local area networks, optical backplanes, and optoelectronic accelerators or signal processors. In some applications, the aggregate bandwidth required cannot be provided with electrical interconnects, offering an obvious advantage for optics, while in others it is the density of available interconnects which motivates the use of optics. In most commercial applications, it is the cost of the interconnect solution which will affect its acceptance by system integrator. For optics to be applied in a broad range of applications, greater transparency must be provided to the system integrator. We describe both intercabinet and intracabinet interconnects in which the addition of optical interconnects has been designed to perturb the overall system as little as possible and yet still take advantage of optics.

Vertical cavity surface emitting lasers for spaceborne photonic interconnects

Vertical cavity surface emitting lasers (VCSELs) offer substantial advantages in performance and simplicity of packaging over the edge emitting lasers currently being applied to state-of-the-art photonic interconnects. We have demonstrated operation of VCSELs at cryogenic temperatures and at temperatures as high as 200 degrees Celsius, with a single device operating from minus 55 degrees Celsius to plus 125 degrees Celsius. The devices operate to 14 GHZ and can be operated in excess of 1 GHZ with bias-free operation. Initial radiation tests indicate an order of magnitude improvement in hardness with respect to neutron damage over an LED which is currently used in spaceborne photonic interconnect modules. We also describe the packaging of VCSELs in compact multichip modules. By using passive alignment techniques, optoelectronic devices can be packaged in established multichip module fabrication schemes without adding costly high precision assembly techniques.