We discuss the reliability of the oxide VCSELs made by Agilent Technologies (formerly part of Hewlett Packard). Measurements of operating temperature in fiber optic modules are given; these temperatures are higher than generally assumed. General challenges with oxide VCSEL reliability are introduced, and different types of failures are discussed. Long-term oxide VCSEL lifetest results are presented, along with observations about the thermal and current acceleration models. Production monitoring strategies are discussed, and the basic degradation phenomenology is briefly shown.
The ability to tailor the emission characteristics through use of a microcavity has become an interesting topic for fabricating improved forms of light emitters. For semiconductor light emitters the novel cavity physics also complements the technological importance, and the advanced fabrication techniques allow for mode confinement presently in the volume range of tens of cubic emission wavelengths. In this paper we discuss the mode confinement possible with Fabry-Perot semiconductor microcavities that both have extremely short cavity lengths and contain embedded dielectric regions.WHile this confinements mechanism was discovered in late 1993, it was not at first clearly understood. Today we have a much better understanding of this system, and it becomes clear that it can impact a broad range of microcavity light emitters. In addition, we discuss combining the 3D confinement of the microcavity with 3D confinement of the electronic carriers, and demonstrate room-temperature lasing from quantum dot vertical-cavity surface-emitting lasers.
Time resolved photoluminescence at 295 degrees K has been used to characterize carrier recombination in a single 80 angstrom In0.20Ga0.80As quantum well before and after wet thermal oxidation of a 300 angstrom Al0.96Ga0.04As layer which is separated from the quantum well by 100 angstrom GaAs and a 225 angstrom Al0.75Ga0.25As barrier layer. Both of these layers are repeated on the other side of the quantum well and all together are typical of a half wave cavity spacer section used in low threshold microcavity VCSELs. Before oxidation the radiative lifetime is 12 ns. After steam oxidation for 5 minutes at 420 degrees Celsius the lifetime and intensity of the photoluminescence remains unchanged. An oxidation time of 10 minutes at the same temperature reduces the radiative lifetime to less than 1 ns and decreases the photoluminescence intensity by a factor of five. In addition, the lifetime and intensity of the photoluminescence remain the same as in the unoxidized case when the Al0.96Ga0.04As layer is etched off in a 1:1 HCl solution, possibly indicating that surface recombination at the Al0.75Ga0.25As barrier is not responsible for the shorter lifetimes in the oxidized samples. Furthermore, secondary ion mass spectrometry data on steam oxidized and unoxidized samples shows the presence of a significant oxygen concentration in the quantum well for oxidized samples that had sub nanosecond lifetimes and no oxygen in the quantum wells for samples that were not steam oxidized and displayed 12 ns lifetimes.
We review the recent results on the design and implementation of the performance-optimized bidirectional optical backplane bus aimed at high speed multiprocessor systems. It employs an array of multiplexed holograms, in conjunction with a waveguiding plate within which cascaded fanouts are generated. Data transfer rate of 1.2 Gbit/sec at 1300 nm is demonstrated with a single bus line for a system composed of nine boards. Packaging-related issues and misalignment effects are addressed. Theoretical treatment to minimize fluctuations among the received powers at each board was carried out and the overall performance was optimized. We also introduce a hybrid optical backplane with multiple bus lines. The hybrid backplane maintains the same waveguiding structure, and exploits optoelectronic array devices. A new demonstration system is being implemented. The optical backplane that we developed is transparent to higher level bus protocols, thus can support standard backplane buses such as Futurebus+, Multibus II, and VMEbus.
Optical interconnects have potential advantage over electrical methods at the backplane level. In this paper we present a free-space optical connection cube for backplane interconnect applications. The connection cube has a symmetric structure which reduces skew between boards. It can be expanded into a 3-dimensional configuration for parallel communication using vertical-cavity surface-emitting laser (VCSEL) and receiver arrays. Fan-out and fan-in of propagation beams for the connection cube are realized using volume holographic optical elements formed in dichromated gelatin (DCG) emulsion. A four-port communication system has been demonstrated using the connection cube and tested at 500 MHz. In this paper, advantages and detailed implementation of the free-space optical connection cube are presented. Design considerations for fan-out/in holographic gratings and alignment tolerances for the connection cube are discussed. Characteristics of the connection cube are also presented.