Raytheon Vision Systems (RVS) has a long history of providing state of the art infrared sensor chip assemblies (SCAs) for the astronomical community. This paper will provide an update of RVS capabilities for the community not only for the infrared wavelengths but also in the visible wavelengths as well. Large format infrared detector arrays are now available that meet the demanding requirements of the low background scientific community across the wavelength spectrum. These detector arrays have formats from 1k x 1k to as large as 8k x 8k with pixel sizes ranging from 8 to 27 μm. Focal plane arrays have been demonstrated with a variety of detector materials: SiPiN, HgCdTe, InSb, and Si:As IBC. All of these detector materials have demonstrated low noise and dark current, high quantum efficiency, and excellent uniformity. All can meet the high performance requirements for low-background within the limits of their respective spectral and operating temperature ranges.
Raytheon has built hybrid focal planes based on Silicon P-I-N photo-sensors for the past three decades. The device has undergone a continuous improvement process during this period. The detector material has been improved and the thickness has been greatly reduced. Most recently, the readout integrated circuit (ROIC) and the hybridization process, have undergone significant advancements1,2,3. This paper presents recent advancements in the latest generation 8μm pixelpitch 1k2 format and 5k2 format visible Si PIN focal-planes. The current family of devices has very low read-noise ROICs, low detector dark current, operate with a 25 volt bias and deliver 50% mean response operability greater than 99.995%.
Raytheon continues to build large format digital visible focal planes. This paper provides the most recent performance to date in operability and performance.
Raytheon has been building silicon p-i-n (Si-PIN) detector arrays for the past twenty years for various remote sensing
instruments such as MODIS, EO-1, and Landsat now on orbit. See Figure 1. The Si-PIN technology at Raytheon has
matured in the past five years with the addition of a dedicated silicon wafer fab, improvements in hybrid technologies,
and the enhanced digital functionality of RVS custom read out integrated circuits (ROICs). This paper will discuss the
advantages that Raytheon Si-PIN arrays offer over conventional CCDs and monolithic CMOS imagers such as 100%
optical fill factor, high QE (visible - near IR), high MTF, and radiation hardness.
Standards activities for the next generation of Ethernet, 10 Gigabit Ethernet, are underway. Vertical Cavity Surface Emitting Lasers (VCSELs) offer significant advantages for realizing cost-effective, high speed optical data links. The progress towards achieving 10 Gb/s VCSEL-based links is reviewed.
System architects in the communications and computing industries have been waiting for the arrival of cost effective fiber optic links to relieve the copper BW*distance constraint for intra and short reach inter-system connections. Parallel optics has been targeted at this application space for several years, but up until the current generation of systems, these applications largely remained copper. The current change-over in interconnect media is partially due to the engineering challenge in meeting performance requirements with electrical interconnects as well as the progress in parallel fiber optic components. Gore has been investigating aggressively in the research and development of the technologies required for producing high bandwidth, reliable, and cost effective parallel fiber optic links. The first commercialization of this effort will be the nLIGHTEN parallel optical modules. This paper details the design, fabrication, and operation of this high performance, short haul communication system.
Vertical cavity surface emitting lasers (VCSELs) operating near 1310 or 1550 nm have been the subject of intensive research by multiple groups for several years. In the past year at Gore, we have demonstrated the first 1300 nm VCSELs which operate with useful power, high modulation rate, and low voltage over the commercial temperature range of 0 - 70 degree(s)C. These results have been achieved using a new structure in which an 850 nm VCSEL optical pump is integrated with the 1300 nm VCSEL. Electrical drive is applied to the 850 nm pump, and 1300 nm light is emitted from the integrated structure. This approach has resulted in over a milliwatt of single transverse mode power at room temperature, and several hundred microwatts of single transverse mode power at 70 degree(s)C. In addition, these devices demonstrate multi-gigabit modulation and excellent coupling efficiency to single-mode fiber.
Applications for serial and parallel fiber optic data links are reviewed along with the barriers to widespread commercial adoption. An alternative migration path from copper to optical media, enabled by VCSEL technology, is investigated including initial performance results.
The use of native oxides (selective oxidation) in vertical cavity surface emitting lasers has produced dramatic improvements in these laser diodes but has also been suspected of causing poor reliability because of incidental reports of short lifetimes and physical considerations. Here we discuss the results of thousands of hours life-tests for oxide confined and implant confined devices at current densities from 1 to 12 kA/cm2. There was a single infant mortality failure from a sample of 14 oxide confined lasers with the remainder showing relatively stable operation. The failed device is analyzed in terms of light current characteristics and near-field electroluminescence images, and potential screening criteria are proposed.
Future advances in the application of photonic interconnects will involve the insertion of parallel-channel links into Multi-Chip Modules (MCMs) and board-level parallel connections. Such applications will drive photonic link components into more compact forms that consume far less power than traditional telecommunication data links. These will make use of new device-level technologies such as vertical cavity surfaceemitting lasers and special low-power parallel photoreceiver circuits. Depending on the application, these device technologies will often be monolithically integrated to reduce the amount of board or module real estate required by the photonics. Highly parallel MCM and board-level applications will also require simplified drive circuitry, lower cost, and higher reliability than has been demonstrated in photonic and optoelectronic technologies. An example is found in two-dimensional point-to-point array interconnects for MCM stacking. These interconnects are based on high-efficiency Vertical Cavity Surface Emitting Lasers (VCSELs), Heterojunction Bipolar Transistor (HBT) photoreceivers, integrated micro-optics, and MCM-compatible packaging techniques. Individual channels have been demonstrated at 100 Mb/s, operating with a direct 3.3V CMOS electronic interface while using 45 mW of electrical power. These results demonstrate how optoelectronic device technologies can be optimized for low-power parallel link applications.
The gain-dependent polarization properties of vertical-cavity surface emitting lasers and methods for polarization control and modulation are discussed. The partitioning of power between the two orthogonal eigen polarizations is shown to depend upon the relative spectral alignment of the nondegenerate polarization cavity resonances with the laser gain spectrum. A dominant polarization can thus be maintained by employing a blue-shifted offset of the peak laser gain relative to the cavity resonance wavelength. Alternatively, the polarization can be controlled through use of anisotropic transverse cavity geometries. The orthogonal eigen polarizations are also shown to enable polarization modulation. By exploiting polarization switching transitions in cruciform lasers, polarization modulation of the fundamental mode up to 50 MHz is demonstrated. At lower modulation frequencies, complementary digital polarized output or frequency doubling of the polarized output is obtained. Control and manipulation of vertical-cavity laser polarization may prove valuable for present and future applications.
An optical interconnection system is being developed to provide vertical, digital data channels for stacked multichip modules. A key component of the system is an array of individually addressable vertical-cavity surface-emitting lasers with diffractive lenses integrated into the substrate to control beam divergence and direction. The lenses were fabricated by direct-write e-beam lithography and reactive ion beam etching into the GaAs substrate. Preliminary device performance data and the design and fabrication issues are discussed.
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