John A. Lehman

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.

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.

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.

Optical modulation of light transmission in GaAs doping superlattices

We report results of measurements of optically modulated optical transmittance of GaAs doping superlattices. The data extend over a spectral region of 1.39–1.58 eV. We find that the peak transmission modulation reaches 21% for a 2.6‐μm‐thick sample and an optical pump power density of <10 W/cm2 at room temperature. We interpret our data in the framework of a simple semiclassical model that includes the Franz–Keldysh effect both below and above the bulk GaAs band gap, as well as band filling and band shrinkage effects.

VCSEL-based modules for optical interconnects

We present characteristics of 850-nm oxide confined vertical-cavity surface-emitting lasers (VCSELs) developed for applications in optical parallel data links and free- space optical interconnects. Low threshold currents of less than 200 (mu) A, wall-plug efficiencies approaching 30%, operating voltages of less than 2 V for 1 mW of optical power, and operation over a wide temperature range, up to 190 degree(s)C, are demonstrated. We optimized VCSEL arrays for operation at elevated temperatures for use in dense free- space interconnects. Excellent performance uniformity-optical power of 1 +/- 0.1 mW at a drive current of 3 mA-across a 20 X 20 array was achieved at 75 degree(s)C. We integrated 2D top emitting VCSEL arrays with top- illuminated metal-semiconductor-metal detectors for future use with CMOS integrated circuits. We discuss design issues encountered in VCSEL-based modules for optical interconnects.

In vacuo responses of an AlGaAs vertical cavity surface emitting laser irradiated by 4.5 MeV protons

Vertical cavity surface emitting lasers (VCSELs) have high potential for space applications, yet little is known of their sensitivity to radiation under vacuum conditions. The first observations of a commercially available proton implanted quantum well AlGaAs VCSEL operating at 850 nm in vacuo and irradiated by 4.5 MeV protons by a scanning ion microbeam is presented. Degradation of L-I-V responses at a proton dose of 1.19 MGy are discussed with particular attention drawn to heating arising from increased nonradiative carrier recombination and that resulting from the vacuum environment.

Component tradeoffs and technology breakpoints for a 50 Mbps to 3.2 Gbps fiber optic data bus for space applications

The design of the optical portion of a fiber optic data bus for space applications is described. A maximum NRZ data rate of 1.9 Gbps is predicted using low risk components which have either been demonstrated in space or for which sufficient qualification data are available. Substitution of lasers and fibers for higher bandwidth components are expected to extend the data rates to 4 Gbps but require additional qualification effort.